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June 19

Coefficient of thermal expansion...

Those who are following this list may have spotted occasional references to my current pet project - refurbishing (well, throwing away and rebuilding from scratch) my home-made computer-driven milling machine (essentially, a robotic 2 horsepower router).

I'm thinking about the calibration of the machine. I'm using three precise stepper motors to rotate threaded steel rods that move the cutter up and down, left and right and in and out. The thread on the rod has a pitch of 16 turns per inch - and the stepper motor can move by just 1/200th of a revolution at a time. So, I have a resolution at around 1/3200'th of an inch! (Well, it's not really that good because of backlash etc...but it's not bad).

The problem is that the steel is going to expand and contract with temperature. So I'd need to calibrate the thing every time I turned it on. The drive system has limit switches - so I can move all the way down/left/in until the limit switches all trip - then move up/right/out until the other limit switches trip - and I'll know how many steps there are between the two limit switches.

But the limit switches are mounted onto the MDF (Medium-density fibreboard) frame - which (I'm hoping) doesn't expand and contract anywhere near as much as steel...but is that really true? Our article says: "Subject to significant shrinkage in low humidity environments."

So - to cut a long story short:

What's the coefficient of thermal expansion of MDF?
What's the coefficient of humidity-related expansion of MDF?
Is it really less than steel?

SteveBaker (talk) 12:23, 19 June 2009 (UTC)[reply]

Steve (I assume)

Carbon steel is 10.8, other steels, depending on composition, range from 11.0 to 13.00 according to our own article on co-efficients. "The thermal conductivity of MDF varies slightly with thickness with the usual range being 0.05-0.08 kcal/mh°C (0.12 - 0.15 W/m°K). Like natural timber, MDF has a low thermal capacity. Within the normal range of temperature variation, MDF is dimensionally stable" according to this trade datasheet.

Humidity seems to be more of an issue, as 30% humidity at 20C can result in 5% moisture content, rising to 12% at 85% humidity. Moisture causes changes in length about 0.03 - 0.06% for every 1% change in moisture content, and by 0.3 - 0.5% in thickness. If your frame is 2 inches wide, this might come to 1/100th of an inch, which is substantial if you are working to 1/3200th accuracy. - KoolerStill (talk) 08:01, 19 June 2009 (UTC)[reply]

(Sorry - I forgot to sign...and for some reason sinebot took a vacation.) The longest distance over which expansion would occur is about a meter. The operating volume of the robot is 1m x 0.5m x 0.25m. So with a range moisture content from 0% to maybe 30%, I might see 30x0.06=2% !! Wow. That is a lot! I hadn't planned to paint the MDF - but now I might...just to control the uptake of water in it! Over (say) a 30 degC temperature range, the steel is going to expand by 30x11=330 parts per million..which is only a third of a millimeter over the longest dimension. So that gets me thinking...if MDF doesn't change size with temperature - and we know that steel doesn't change size with humidity - I wonder if I can have the robot somehow figure out which dimensions are changing. Because the distance between my two limit switches is determined by the moisture content of the MDF and the number of stepper motor steps it takes to move between them is determined by the temperature of the steel...tricky. SteveBaker (talk) 12:23, 19 June 2009 (UTC)[reply]

Ah! I think I have it figured out. If I change the design a bit and mount one pair of limit switches on an aluminium bar - then I can count the number of steps to span that pair of switches (which will be independent of humidity) and I should be able to use the difference in thermal expansion rates of aluminium and steel to calculate the temperature and correct for it. Aluminium expands about twice as much as steel - so I'd get maybe a third of a millimeter difference over a 30 degreeC temperature range - which is around 30 steps of my motor - so this would allow me to measure the temperature accurate to about a degree (is it a robotic milling machine or is it an exceedingly silly thermometer?!) Then I can count the number of steps it takes to get between the limit switches in the other axis (where the limit switches are on MDF) - correct for the expansion of the steel and then I'll know how much the MDF has changed size by and I can figure out how all of the dimensions of the machine have changed and correct for that too. That way, I don't have to care whether the MDF changes dimensions with temperature because I'm just measuring the size directly.

This is so much fun! (Well, if you're a serious geek it is...I imagine some people are yawning at this point.)

SteveBaker (talk) 13:02, 19 June 2009 (UTC)[reply]

Steve, your whole setup, including the workpiece and jigs, will expand and contract. If you intend to work with materials that all have the save coeffiecients of expansion as you machine, then you can simply ignore the problem. If not, then you need to consider the whole system, not just the machine itself. Perhaps you can invest in a single reference block of invar (or something) and calibrate against it each time. -71.0.188.190 (talk) 13:54, 19 June 2009 (UTC)[reply]

That's certainly true - and it's certainly something I've thought about. It's clear that nothing that's made of wood has precise or stable dimensions...and that's mostly what this machine is making. The previous incarnation did a wonderful job of doing wood carving. You could design a 3D pattern of leaves and flowers and stuff by processing a photograph using "shading-to-shape" techniques - then just hit the GO button and about an hour later - you'd have something that looked like someone had spent a month out of their lives carving it. The new version will be much better than that...I'm just exploring the envelope a little here...seeing if I can do yet better without it costing me much. SteveBaker (talk) 14:58, 19 June 2009 (UTC)[reply]

Why don't you measure the MDF fittings, buy a chunk of Hardened Steel, rework your fittings, and design or buy a small coolant pump (a tray underneath to recycle the used coolant, picture ;-)

none goes down the drain) which will work quite well with only a fraction of the flow shown in that picture. You will have no end of improvement to your finish and be much kinder to your tools. Keep the workpiece cool rather than the machine (when it heats up too much it makes crap out of the piece anyway! How can you properly tighten your fittings to MDF without damaging it? You can't.) Use coolant, settle for a frictionless finish rather than all this messing about with burnable stuff! Coolant is dilutable, oils your stuff and recycles itself. It shouldn't cause any major overhead and is the standard method. ~ R.T.G 14:15, 19 June 2009 (UTC)[reply]

Why build a thermometer-machine? can't you put a simple real thermometer/temperature sensor into it? reading that will take less calculation in your already very_tight_on_memory controller chip than having to calculate temperature from relative expansion measurements. It would save having a set-up routine to do the measuring. How are the bars being fixed to allow for this amount of movement without stress or shearing? - KoolerStill (talk) 14:53, 19 June 2009 (UTC)[reply]

I don't think you understand what I'm doing. This is a hand-made machine I keep in my garage for making small (mostly wooden) things - with the new setup, I'm hoping to be able to mill copper circuit boards and drill holes for components - maybe mill a occasional aluminium part for a classic car restoration. I can't have pumps squirting stuff all over the place! If the workpiece gets too hot while I'm milling it - I'll just adjust the software to move the cutting head more slowly and shave off thinner layers - maybe pause for a while between tool passes to let everything cool off. Anyway - the machine has been doing great work for several years now - it's just that all of the cheap rollerskate bearings I used are getting worn and other parts are starting to fail and some of the wires have been flexed back and forth one time too many and broke...so I'm refurbishing it. And in the process using chunkier motors with more precision - new computer interfaces - that kind of thing. Since I have much more precision in the new machine than the old one - I thought I'd do a bit of 'due diligance' and check on the size of the thermal expansion error - and see if some simple steps (SIMPLE!) would reduce it. (Before, the errors due to thermal expansion would have been negligable compared to the backlash in the gear boxes, the lack of precision in the shaft-encoders, etc). My entire budget for building the machine is $200 ($120 of which went into the three big-assed stepper motors). I use the shaft encoders from an old USB mouse for figuring out how far the thing has rotated...that kind of thing. This is a "toy" compared to a professional CNC milling machine...but an amazingly useful toy...well worth a few weekends of work and $200. SteveBaker (talk) 14:52, 19 June 2009 (UTC)[reply]

Would like to say woodworking and PCB baords can't cause too much heat but can't say. Still be much better for the tools and the piece if you cool it when you are cutting metals. You could set up an open top gallon drum with a tube and a tap, chill in the fridge refill it occasionally, use a well aimed trickle, don't want to short the router either. The powerful gush in the CNC picture is probably the optimum but also the maximum. The coolant is reusable and dilute so isn't the most expensive in itself. Fair play but it seems you are agonising rocket science on what you could just make your own hardened steel fittings for. Good luck with it. ~ R.T.G 15:58, 19 June 2009 (UTC)[reply]

You should add it too Wikibooks and Wikiversity unless you are keeping the copies on it. Hardly a mean feat to put together and the motor is as powerful as your average 7-8 foot machine which lasts forever if you replace bits. I guess you are still working out bits for now or even selling the idea. ~ R.T.G 11:09, 20 June 2009 (UTC)[reply]

Without seeing SteveBaker's machine, I think using limit switches mounted on wood as a length standard is not a good idea. Not only is wood the least dimensionally stable material in the machine, the switches themselves presumably contain deformable springs. But if you dissect mice then you have light emitters and detectors with which to arrange optically sensed limits of a length standard. See this table of expansion coefficients. If you choose two readily available materials (steel and aluminium) and make an optical length standard based on each material, your software can calculate a temperature-independent length from the observed difference between the lengths of the materials. Cuddlyable3 (talk) 23:46, 19 June 2009 (UTC)[reply]

Err . . . you are talking about computer mice, aren't you, Cuddlyable3? I had a brief Girl Genius moment there. 87.81.230.195 (talk) 19:53, 20 June 2009 (UTC)[reply]

Why not measure the thermal and humidity related expansions directly with a Strain gauge or two? They are cheap and rather easy to use. Noodle snacks (talk) 12:05, 21 June 2009 (UTC)[reply]

remedy or something else?

On an episode of Emergency! before the opening credits, Roy was gargling warm salt water when Johnny and Chet came into the locker room. A minute later, Chet said his mother made him gargle with vinegar and soybean oil when he had a sore throat. Can those two fluids do the same thing salt water does when gargled?69.203.157.50 (talk) 04:25, 19 June 2009 (UTC)[reply]

Sore throat in common usage has a wider meaning than Acute pharyngitis. It can range from simple dry mucous tissue to something viral or bacterial among other things. Salt water helps with the hydrostatic pressure of the cell walls. Some bugs are sensitive to acids and the ph of many tissues in the human body is slightly acidic. This environment can be changed in favor of pathogens during an infection. Oil will coat the tissue and help against further drying. It may also keep a couple of the nasties from entering cells. So, depends on what you got if it has much of a positive effect, but at least it doesn't do harm. Unlike some OTC and prescription drugs that can seriously upset your system. (Patients who urge their doctors to prescribe antibiotics ignore the fact that those don't work on viruses.) 71.236.26.74 (talk) 07:42, 19 June 2009 (UTC)[reply]

Sustainability

Is it possible for humanity to live in a sustainable global society?

Or are there physical limiations on our global impact in that we will always need to consume more resources than we can replace? TheFutureAwaits (talk) 09:55, 19 June 2009 (UTC)[reply]

It's certainly possible - but almost certainly not at anything like the present population levels. If there were (say) ten million people in the world - we would have negligable impact - but at seven billion, I think it's quite clear that it's unsustainable - somewhere between those two numbers is the limit. SteveBaker (talk) 11:54, 19 June 2009 (UTC)[reply]

I disagree. It isn't at all clear whether or not the current population is sustainable. For example, if economies were all free markets with good protection of property rights, it is possible that we could support more people using fewer resources and with less environmental degradation. Wikiant (talk) 12:07, 19 June 2009 (UTC)[reply]

I'm sorry - but that's incredibly naive.

We can manage less environmental degradation...yes - for sure...but ZERO degradation? That would mean zero use of fossil fuels, zero increase in atmospheric carbon (in fact, a significant REDUCTION in the present levels) - zero mining of metals (100% recycling of every scrap of metal we use...that's insanely difficult!) - zero over-fishing of the oceans. Abandonment of non-recyclable plastics and other chemicals based on fossil oil.

Consider just one case: It's not high on the list of environmental panics - but did you know that the world only has 60 years worth of copper reserves left? Yep - we're going to run out of copper during the lives of some of our younger readers. Even if we go into recycling overdrive - there are no recycling processes that reclaim even 50% of any given resource. So we have 120 years of copper supplies - at most - assuming everyone treats this stuff like gold. Can we do better? Are we geared up to recycling every single scrap of copper we ever use? It's very difficult to do that. Sure - when a building is demolished, we can go in there and salvage all of the copper pipes and electrical wiring - and when a car is recycled, we can pull all of the copper wiring out of the alternator and starter motor. We could stop using copper in coins. But those tiny little copper contacts inside the battery compartment of your kid's toys? Will those get fully, 100% recycled? No - I don't think so. Also, many of the uses of copper require us to mix it with something else - eg to make Brass. You can't get the copper out of brass in order to recycle it without huge expenditures of energy (which - you'll recall - we are also trying to save!)...so gradually, no matter what we do, we cannot sustain the use of copper. We're probably going to run out of copper in industrial quantities within 100 years...the price will rise until it's the price of platinum or something - and we'll have to resort to mining less and less viable mines - resulting in us tearing up yet more of the landscape and consuming yet more energy. Meanwhile - what do we use for conducting electricity? Aluminium works - but it has lots of problems with corrosion in the air and it's not as flexible as copper - so no more bendy wires between your toaster and the wall socket! Silver makes great conductors - but it's kinda rare too.

And that's just one of a whole bunch of things we're running out of. Helium supplies are dwindling - all sorts of the more exotic metals used in modern electronics come from single-source mines that are unique to a particular place on the planet and have predicted lifetimes measured in decades - not centuries.

We are very, VERY far from living sustainably!

SteveBaker (talk) 13:25, 19 June 2009 (UTC)[reply]

Steve makes some great points and I'm really curious about the implications of them. I just don't see how even in theory we can live sustainability given our resource requirements and the difficulty in reusing and recycling these resources. Which also means unless we all move off-world (which is really, really impractical so can we not get into that?) it seems like we're doomed. Maybe to an agrarian culture? Maybe to not exist at all. Am I wrong? TheFutureAwaits (talk) 13:34, 19 June 2009 (UTC)[reply]

How is "moving off world" sustainable? All you have done is generalize all resources that we consume into one "planet resource", which you have casually discarded when it becomes easier to go somewhere else. Nimur (talk) 14:56, 19 June 2009 (UTC)[reply]

Before we get too much into the carrying capacity discussion I should clarify I'm wondering if it's possible for people to live a 100% sustainable lifestyle and then apply this on a broad scale. In my experience even the greatest green technologies always produce waste. On the other hand when we lived without technology we apparently had major ecological impacts (the death of native species in the Americas and Australia upon our early arrivals comes to mind) so I don't think abandoning technology would offer much of a solution.

So is it possible through the application of technology to live a 100% sustainable life and to apply that on a massive scale? Or are there simply limits to the degree we can minimize our impact? TheFutureAwaits (talk) 13:28, 19 June 2009 (UTC)[reply]

We could certainly revert to stone-age existances - but there is no way for seven billion people to live that way! We'd all need stone tools - will the supply of flinty rocks be enough? Are there enough natural caves for us to live in? Would the much lower density of wild animals be able to support such a population without dense farming with fertilizers and irrigation? No! Not by a million miles! For us to revert to a stone-age lifestyle - we'd need a stone-age population density - which means that we would have to wipe out 99.9% of humanity to get down to about 5 to 10 million people (that was the estimated world population in 10,000 BC when farming and such like started). If we did that - then we could live very close to sustainably in the lap of luxury with all of modern technology. Copper would run out in 60,000 years instead of 60 years. Global warming would cease to be a problem - we could all drive gas-guzzling Hummer's and the planet would hardly notice. The problem isn't our technology - it's our sheer numbers. SteveBaker (talk) 13:37, 19 June 2009 (UTC)[reply]

I disagree, it seems like population reduction (say everyone had one child for the next several generations) would only delay the inevitable. Sure copper might last 60,000 years instead of 60 but we're just moving the problem further downfield. It seems like eventually, no matter what we do, we're going to hit that wall. That's why I'd like some evidence that we won't; that there is some way to live sustainably at least until the sun runs out of hydrogen. TheFutureAwaits (talk) 13:48, 19 June 2009 (UTC)[reply]

Certainly there is no way to consume anything whatever and last forever. Even that stone-age existance with just 1 million people would result in them running out of stone to make tools - eventually. The rate of new rock formation just isn't high enough. We'd have to revert to being great apes with zero technology. That probably requires a genetic change - we'd have to de-evolve back to a more primitive form. But there is a massive difference between having 60 years worth of copper reserves and 60,000 years worth. In 60,000 years we could produce the technology to mine the asteroids - spread onto other planets - build robotic mining machines to dismantle entire planets in search of copper (or whatever). With the resources of the entire solar system and 60,000 years of technological advancement, I have no doubt whatever that we could survive until the extinction of the sun without reverting to pre-stone-age techniques. But there is no way we're going to find a way to mine the asteroids for copper in the next 60 years.

A chinese-style one-child-per-family approach would drop the population by a factor of two in every generation. If we could enforce that world-wide for 10 generations then switch to a two-child-per-family approach, we'd survive this. But that's not such a simple thing to do. Each new generation of workers - has to support two retired people each in addition to themselves...that's tough! But if we could do it - we might be OK. If we take copper as our benchmark (we could choose oil or atmospheric carbon instead) - then in the 60 years it takes the copper to run out - we may have halved our population - which means that we extended the life of the copper reserves by what? 15 years (assuming linear reduction in consumption)...but we can't halve the population again in the next 15 years without killing a lot of people! So the copper is gone...there is nothing we can do to stop that. For oil, I think we could reduce our population faster than we're running out - and for global warming, we could certainly avert disaster by halving our population over the next 60 years.

But applying such draconian measures is tough! China did it only because they were a totalitarian state with relatively compliant people. Could you imagine doing that in the USA?!! It's pretty inconcievable. Religious limitations on birth control would prevent large swaths of the roman catholic world from following that reduction rate. If some countries decided to make the supreme sacrifice and others didn't, you'd find that the sharply decreasing population of the "good guys" would result in them being overrun by the numerical superiority of the "bad guys". Governments would realise this - and we'd never get agreement to do this on a global scale.

Sadly, we're probably doomed.

SteveBaker (talk) 14:08, 19 June 2009 (UTC)[reply]

I strongly disagree that asteroid mining in the next 60 years is infeasible. 60 years is a long time, technologically speaking. Think where we were 60 years ago. We were still 8 years away from putting something into orbit. Now trips to LEO are strictly routine and there are serious plans to long-term occupation of the moon (as opposed to everyone assuming there would be such plans sometime next week but nobody actually planning it which has been going on for decades). Manned missions to Mars are intended for sometime in the next 30 years (although 40 might be more likely). Once you can get to Mars, getting to the asteroid belt isn't much harder (near-Earth asteroids are even easier and wholly robotic mining operations might be a better option as well). If the price of things like copper increases as your numbers suggest it will, asteroid mining will easily become economically viable, which means private business will get involved. Private businesses generally move much faster than national space programs since they don't have to contend with massive budget cuts. I wouldn't be at all surprised to see asteroid mining within the next 60 years (although I know better than to make definite predictions that far into the future where technology is concerned). --Tango (talk) 22:53, 20 June 2009 (UTC)[reply]

What is sustainability, anyway? How long does something have to be sustainable? After all, our energy comes exclusively from stellar fusion, so we really only need to be as sustainable as the sun.

All life is an energy-intensive process. I make the vague-and-handwavey claim that "higher forms of life are less efficient Carnot engines." In the most basic life-like things on Earth (say, a virus), the energy consumption is near zero until it is time to reproduce. The next steps up on the chain, the autotrophic prokaryotes, are pretty darn efficient - they absorb solar or geothermal energy, and use it to drive a simple chemical reaction and produce complex chemicals. The next few steps upward on the chain of "complex life" move into the realm of multicellular organisms, and the first heterotrophs emerge. These are much less energy-efficient organisms, in that they can't even generate their own energy, but must prey on some other thing. So, solar energy gets concentrated by algae, and then multicellular pondscum comes along and eats on the solar-fed algae. Pond scum, in my naive definition, is thus a "higher form of life," because it has a more complex energy pathway, and uses the excess energy to produce more complicated molecules (like enzymes for digesting the cellulose that they're eating).

As we continue to move up to higher organisms, we see that the total amount of energy for each organism is increasing; and the total efficiency of the food chain is decreasing. When we reach macroscopic organisms like frogs and monkeys, these guys are consuming just enormous quantities of energy compared to the single-celled organisms. So, you need to have billions of algaes so that the pondscum zooplankton can eat them, and millions of zooplankton to feed thousands of fish, and thousands of fish to feed one or two monkeys or frogs ("sustainably"). The root energy supply is still solar, but the ecosystem is getting more towering and the food chain is very sophisticated by this point.

After several million years, some creature decides that this is actually an inefficient way to extract energy from the environment, and begins to develop technology to circumvent the foodchain. They domesticate sheep and cows, and learn how to farm, to speed up the process of concentrating solar energy into usable food. They also develop fire, and waterwheels, and nuclear fission, and petroleum refining. This is a new step up on the hierarchy of "advanced forms of life" - they are able to extract a larger quantity of energy by collecting solar energy that has been stored somewhere for the last millions of years by trillions of algaes. Amazing! Biology has been circumvented with engineering! Now, more energy is extracted, but as always, it is a less-efficient way of using each individual joule of solar energy. This is sort of necessary, though, because thermodynamics teaches us that by physical law, every energy transfer process has some waste. (Maybe somebody who is familiar with thermodynamics can voice their interpretation of the Second Law?)

By extrapolation (making stuff up) it would seem that the most advanced forms of life will continue to consume more and more energy. SteveBaker's robot brains will start to take shape - a server room full of ten thousand blade servers will consume far more energy (in Joules) than the human that it is simulating. But, it will be able to use electricity, instead of trying to digest rice and cow; and it will be able to speed its simulation up or down or whatever. But it's using more energy, which is the only nonrenewable resource.

So, I propose Nader's Law Nimur's Law?: an optimal form of life is the one which matches its energy consumption to the rate of maximum return before the heat-death of the universe. In other words, the pitiful little algaes are extremely energy efficient but their form of life is so primitive and limited that they won't accomplish much. At best, they can hope to make lots of sugar and... sweeten the ocean or something. That's their maximal impact. We humans are successfully changing our atmosphere, launching manmade objects into deep space, building cities and art and pornography, setting fire to cities and art and pornography, raising sheep, developing advanced languages and computers, walking on the moon... so sure, we're not as energy-efficient as the algae, but we do a lot more cool stuff. We've managed to concentrate our resources into a form that is useful for these sorts of tasks - at the expense of some of those resources. Maybe our robot computer replacements will be even better at that sort of stuff with less waste (but I doubt it - they'll find needs for larger energy budgets, with the accompanying extra resource waste). It's entirely possible that some form of life higher or lower than us will actually be more effective, over the cosmological time-scales of our universe, to use energy more efficiently than us to accomplish the same things - but there is a ticking clock - if we don't use the energy up, entropy will dissipate it for us anyway. Nimur (talk) 15:22, 19 June 2009 (UTC)[reply]

When human load exceeds supply, something like a Malthusian catastrophe could result. Remember that we'd run out of natural resources if everyone in the world had an ecological footprint as large as that of say, an average American, in fact we'd need about 5 Earths' worth of resources. ~A H 1^(TCU) 01:08, 22 June 2009 (UTC)[reply]

On Hawaii

When did the first settlers arrive in Hawaii? I'm not talking about americans, mind you, but the original people of hawaii?Drew Smith What I've done 10:46, 19 June 2009 (UTC)[reply]

According to ancient Hawaii, it was some time between the third and eighth centuries. Algebraist 10:50, 19 June 2009 (UTC)[reply]

Big Bang

Is there a formal name for the big bang theory? or is that all there is? 84.97.254.29 (talk) 10:55, 19 June 2009 (UTC)[reply]

It's formally called the Big Bang theory. An earlier name is l'hypothèse de l'atome primitif, if you want an alternative for some reason. Algebraist 10:59, 19 June 2009 (UTC)[reply]

Yeah - it's kinda sad. The guy who named it (Fred Hoyle) didn't believe in the theory and was being incredibly sarcastic about it in a radio interview - he pretty much thought up the name on the spot as a way to mock the people who believed in it! So the name of the theory that explains how the entire universe started doesn't get a fancy, grandiose name...but a joke. <sigh> SteveBaker (talk) 13:29, 19 June 2009 (UTC)[reply]

Hoyle did coin the name, but I don't think he meant it to be insulting, it was just meant to contrast with "steady state". The articles Fred Hoyle and Big Bang have a couple of sources backing this up. It's better than the earlier names "primeval atom" and "cosmic egg", which are just ridiculous. The problem with all of those names is that they emphasize the wrong thing, the singularity where the model breaks down instead of the well-behaved region where it makes predictions. "Big bang cosmology" is not about a big bang, it's about the evolution of an expanding universe. You might as well call general relativity "the theory of black holes". Of course, "general relativity" is a stupid name also. So is "quantum mechanics". Oh well. -- BenRG (talk) 16:27, 19 June 2009 (UTC)[reply]

Why are "general relativity" and "quantum mechanics" stupid names? A Quest For Knowledge (talk) 16:31, 19 June 2009 (UTC)[reply]

General relativity isn't a great name because it only makes sense in the historical context of it being a generalisation of special relativity. And, of course, special relativity only makes sense in the context of it being a special case of general relativity. It is something of a circular definition. The only part which has any meaning in itself is "relativity", which offers no suggestion of how it is different to Galilean relativity which had been around for several hundred years before Einstein came on the scene. "(General/Special) invariant speed of light theory" would be more descriptive, albeit it a little less catchy. I don't have any real problem with "quantum mechanics", though, although I would rather name theories by their hypotheses, not their uses. The theory has nothing to do with mechanics, that's just what it is used for. "Quantum energy theory" might be better. --Tango (talk) 16:41, 19 June 2009 (UTC)[reply]

I had a professor who said that the name "special relativity" was ironic, because the key point of the theory was that the speed of light *wasn't* relative, but was the same for everyone everywhere. If I remember correctly, Einstein didn"t like "relativity" either, and prefered the term "invariance theory". (Doesn't seem to be mentioned on Wikipedia - Google ("invariance theory" einstein) for references.) -- 75.42.235.29 (talk) 03:26, 20 June 2009 (UTC)[reply]

Yes, Einstein later in his life thought it ought to be called invariance theory (because he got sick of people missing the point that the invariances are more novel than the relativity), and on GR he later (following Vladimir Fock) wanted just to call it a "theory of gravitation" or something like that, more straightforward and less emphasis on the relativity. Quantum mechanics was so named to differentiate it from (old) quantum theory. --98.217.14.211 (talk) 18:42, 20 June 2009 (UTC)[reply]

Most physicists would probably say "big bang cosmology" rather than "the big bang theory". The latter sounds like a layperson's term (and now like a TV series). You could also call it "Friedmann cosmology" or "Friedmann-Robertson-Walker cosmology". That calls attention to the expansion instead of the singularity. The currently favored version of big bang cosmology is called the "Lambda-CDM concordance model". It's the simplest version of Friedmann cosmology that's consistent with the currently available data. You could also call it "Lambda-CDM cosmology". Lambda-CDM might give way in a few years to another model with a different name which would still be under the umbrella of big bang/Friedmann cosmology. None of these are very good names, but they're a bit more formal sounding. -- BenRG (talk) 16:27, 19 June 2009 (UTC)[reply]

Nudibranch (or something)

Hey guys, could some marine enthusiast help me identify this nudibranch subspecies? The picture is from Crete. If the relevant article is in need of a pic, I'll gladly post this one. Thanx! P.S. At least I think it's a nudibranch! PervyPirate (talk) 11:11, 19 June 2009 (UTC)[reply]

It's surely a sea slug of some slimy sort, but whether it's a nudibranch or a Cephalaspidea, or a Aglajidae, or a Sacoglossa, or even a Onchidiidae is not clear to me. This website http://www.nudipixel.net/ might help. If they have a forum you could ask there too. (I know the name sounds sketchy but it is a legit site on nudibranchs. It's SFW as long as your boss isn't a gastropod.) Sifaka ^talk 19:28, 20 June 2009 (UTC)[reply]

It's probably a polycladida flatworm, maybe yungia aurantiaca, which looks pretty similar,[1] but there's plenty to choose from. Mikenorton (talk) 20:35, 20 June 2009 (UTC)[reply]

To Sifaka: What a wonderful site this is! I think I'm gonna start making T-shirts with all those nudibranchs! Unfortunately, the genus I'm looking for is not there... Oh, and my boss kinda behaves like a gastropod, throwing ink at people and looking annoyed if somebody bothers him (Yes, we are both scuba instructors!)
To Mikenorton: YES!! That's exactly the one I've been looking for... I wish we had a relevant article for me to add that picture to.. I guess I'll have to create it myself then.. "Orange flatworm" it is!

Thanx a lot to both of you! PervyPirate (talk) 01:03, 21 June 2009 (UTC)[reply]

ADD and stimulants

Hi there. I notice most treatment for ADD/ADHD are amphetamine stimulants like Adderol and Ritalin. How are the actions of those drugs different than say giving someone with ADD 20 cups of coffee? How is one stimulant different than another? --70.167.58.6 (talk) 13:34, 19 June 2009 (UTC)[reply]

It has a few side-effects! I think that 20 cups of coffee contains something close to the lethal dose of caffeine for a human. It's LD50 is 150mg/kg of body weight...and a cup of coffee has about 150mg of the stuff - so if you drink one cup of coffee per kilogram of your body weight in a period of a few hours - you have a 50/50 chance of dropping dead. So a 20kg kid and 20 cups of coffee will likely die. A 50kg kid would do better - but it's hardly healthy! One assumes that these other stimulants have much better controlled side-effects. SteveBaker (talk) 13:48, 19 June 2009 (UTC)[reply]

I was using hyperbole. ;) I didn't really mean for someone to drink 20 cups. Aren't amphetamines highly addictive? (Valley of the Dolls, Judy Garland, and all that?) --70.167.58.6 (talk) 14:42, 19 June 2009 (UTC)[reply]

Really, Steve? How long do you think it would take for you to drink 70 cups of coffee? Quite a bit longer than the ~5 hour half-life of caffeine, I would expect. – Clockwork Soul 16:47, 19 June 2009 (UTC)[reply]

In laymen's terms, the neurobiology of ADHD can be simplified in a similar way that depression is simplified. With depression, low serotonin levels cause depressive symptoms, and most antidepressants (TCAs and SSRIs) increase these levels. For ADHD, low dopamine levels cause irritability, lack of focus and lack of pleasure (from tasks such as reading), and most ADHD treatments (amphetamine, methylphenidate) increase these dopamine levels. In reality neurobiology is far more complicated than that (and the "monoamine hypothesis" - which states that low serotonin causes depression - is pretty much obsolete now). --Mark PEA (talk) 18:39, 19 June 2009 (UTC)[reply]

Well, I think those statements are somewhat controversial, but the key point is that all stimulants are not created equal. The stimulants that work for ADHD are psychomotor stimulants, which affect the brain's dopamine system. Caffeine operates by a completely different mechanism. (Nicotine, on the other hand, might have some effect, since it partly acts as a psychomotor stimulant.) Looie496 (talk) 00:04, 20 June 2009 (UTC)[reply]

Stimulants used to treat ADHD raise the extracellular concentrations of the neurotransmitters dopamine and norepinephrine which causes an increase in neurotransmission. The therapeutic benefits are due to noradrenergic effects at the locus coeruleus and the prefrontal cortex and dopaminergic effects at the nucleus accumbens. ^[1] Hit up the refs on the Main ADHD page in the management section to find some decent scientific papers on the subject. I suppose you can compare that to the pharmacological effects of caffeine. People with ADHD are more prone to using psychoactive substances which include caffeine. As for how stimulants are different there is info at ADHD management, (the article could use a little cleanup for clarity...) Sifaka ^talk 19:11, 20 June 2009 (UTC)[reply]

kineto-baric?? what is this?

Hi

Here are a couple of links to a phenomena called kineto baric effects. Could someone tell me what exactly this is, found a Nasa page on it and mention on a book so Its not something a internet crackpot just made up. Can anyone please tell me exactly what this is??

Kinetobaric effects, a new phenomenon Peschka, W. http://adsabs.harvard.edu/abs/1974DFVLR......603P

http://books.google.co.uk/books?id=zENRkvFO0SEC&pg=PA226&lpg=PA226&dq=kineto+baric&source=bl&ots=qxeQVo7ZB_&sig=SN0aR7fGi9hy1lvD4Puozpjr9bc&hl=en&ei=OJc7SsWhMOeMjAfoxpAg&sa=X&oi=book_result&ct=result&resnum=4

Thanks in advance

Rob —Preceding unsigned comment added by 79.67.246.16 (talk) 13:56, 19 June 2009 (UTC)[reply]

It looks like junk-science to me. Your first link doesn't suggest that NASA endorses it - only that it's in their database of science abstracts. This work dates back to the 1970's - if they had truly found a new kind of force - you'd bet that mainstream scientists would have been all over it by now. So your evidence boils down to a 35 year old paper in an obscure German publication - and a reference in a book that's full of crackpot theories. A google search on the term turns up lots of crackpot/free-energy web sites. It's junk. SteveBaker (talk) 14:40, 19 June 2009 (UTC)[reply]

I second the vote for junk science, with the caveat that it's equally likely that the abstract has been mangled by poor translation. If you can get your hands on the original, you may be able to get a better translation. Nimur (talk) 15:44, 19 June 2009 (UTC)[reply]

The original article is not necessarily junk science—it might just be wrong science, or incomplete science, or premature science. --98.217.14.211 (talk) 18:35, 20 June 2009 (UTC)[reply]

Ok thanks guys, just thought I would ask.

Rob —Preceding unsigned comment added by 79.67.246.16 (talk) 18:24, 19 June 2009 (UTC)[reply]

I couldn't access one of your links. I had a look around for the German text by W. Peschka [2] His report looks like any other "our experiment has shown this result and we don't have any clue as to why" kind of scratching our heads report. They were re-creating some setup originally done by R. Zinsser during WWII. The effect is described as generating "mechanical energy from an an anisotropic gravitational field" Peschka has a reasonable track record in research at the German Aerospace Center. There doesn't seem to have been much further study since 1974. A followup study in 2004 could not re-create the effect and assumes that the previous results were caused by thermal expansion or air movement [3] However Peschka's report seem to have been adopted by some fans of Fringe science. 68.208.122.33 (talk) 19:04, 20 June 2009 (UTC)[reply]

Black rope has musty mildew smell. How to clean?

How can one remove a musty mildewy smell from a colored rope? My first instinct is to dip it in bleach, but that would destroy the color. Are there any color safe ways to remove mildew? --Navstar (talk) 14:35, 19 June 2009 (UTC)[reply]

Vinegar would work as well as bleach, and smell better too. Use white vinegar diluted no more than 1:3 with warm water, and move the rope around vigorously to make sure it gets in between the twists. Rinse in plain water. Then dry it in the tumble dryer, as it is residual dampness that causes the growth of mold or mildew.- KoolerStill (talk) 15:48, 19 June 2009 (UTC)[reply]

Many things you could do to remove mildew from a rope could reduce its strength, as could the mildew itself. Unless it is just a decoration, how about starting with fresh rope and taking better care to store it is conditions not conducive to mildew? [4] gives some hints on cleaning and caring for rope, and says that bleach weakens it as does battery acid. No mention of vinegar. Here is a 1956 Popular Mechanics article on rope care [5]. Here is a book on rigging with a section on rope care: keep it clean and dry.[6] The sources suggest thay poly rope is not likely to mildew. Is your rope natural fiber? Edison (talk) 18:43, 19 June 2009 (UTC)[reply]

Some OR on mildewed poly rope: The fibers themselves are not likely to mildew, but that doesn't mean that stuff can't grow in between the twists. There are a number of products on the market that claim to be safe on fabric. (e.g.[7]) If it's just the smell you want to get rid of, go over to the nearest dive shop. They sell little packets to use on dive gear. I'd second opinions voiced above on not using the rope for anything critical and replacing it sounds like a great idea. 68.208.122.33 (talk) 19:28, 20 June 2009 (UTC)[reply]

Fishing in Ontario lake

Was fishing today. Saw clearly a pink, almost red fish swimming around. Fish was big - I would say more then 2kg (umm, relatively big). Looked like oversized aquarium fish(only because of the color). Put fish like bait in front of her - but then realized that predator could not wear such color. Asked two fisherman - both come up with idea that it could be carp fish. Why pinkish red? One said that it could be ill(was not looking like ill one at all) and another one joked that it is too much uranium around... Is there a spice that could look like that? Or it is totally weird fish? I'm really a newbie in fishing(caught my very first fish today, Largemouth bass:)) DeadlyPenguin (talk) 17:42, 19 June 2009 (UTC)[reply]

Carp, Goldfish, and Koi are all very closely related species. It's very possible that there can be colored variants in the wild, even with never-domesticated fish. (There was a recent story about a yellow lobster caught from the wild, where there are also blue and white variants.) By the way, carp are omnivores/scavengers, so they would have no problem eating dead fish. -- 128.104.112.114 (talk) 20:38, 19 June 2009 (UTC)[reply]

Definitly a carp. As IP said before, carp, goldfish, and koi are all closely related, with the common ancestor being carp. Obviously carp ancestors had to have the light colored pigmentation gene otherwise we would not have such vibrantly colored goldfish and koi today. Selective breeding has beautified, and mangled goldfish completely.Drew Smith What I've done 14:36, 20 June 2009 (UTC)[reply]

Might be Chinook salmon if carp doesn't fit your bill. [8] —Preceding unsigned comment added by 68.208.122.33 (talk) 19:37, 20 June 2009 (UTC)[reply]

Question on J.J. Sakurai's notation

I've just read through the first chapter of Sakurai's Modern Quantum Mechanics, and I've begun working through the problems. The second problem has totally baffled me with notation. Throughout the chapter the dot, $\cdot$ , is used for explicit multiplication, and the boldface dot, which I'm not sure how to produce with this LaTeX, is used for the inner product. In problem 2 (page 60) Sakurai states

Suppose a $2\times 2$ matrix $X$ … is written as
$X=a_{0}+\mathbf {\sigma \cdot a}$
where $a_{0}$ and $a_{1,2,3}$ are numbers.

where the sigma, dot, and 'a', are all boldface, and he asks

a. How are $a_{0}$ and $a_{k}$ ( $k=1,2,3$ ) related to $\mathrm {tr} (X)$ and $\mathrm {tr} (\sigma _{k}\,X)$ ?
b. Obtain $a_{0}$ and $a_{k}$ in terms of the matrix elements $X_{ij}$ .

Since $X$ is $2\times 2$ , clearly $a_{0}=a_{0}I_{2}=a_{0}{\begin{pmatrix}1&0\\0&1\end{pmatrix}}$ , right? He uses this implied notation in the chapter. But what is $\mathbf {\sigma \cdot a}$ ? Clearly $\mathbf {a}$ is a 3-component vector. It seems like $\mathbf {\sigma }$ is also. But, if they're both vectors, and the dot is the inner product, then

$X=(a_{0}+\mathbf {\sigma \cdot a} )I_{2}$

and the questions make no sense…to me, anyway.

One further piece of evidence is that in Problem 3 Sakurai refers to the "determinant of a $2\times 2$ matrix $\mathbf {\sigma \cdot a}$ " as well as $\mathbf {\sigma \cdot {\hat {n}}}$ "when $\mathbf {\hat {n}}$ is in the positive $z$ -direction".

So, $\mathbf {\sigma \cdot a}$ can be a $2\times 2$ matrix! But how? Even if the boldface dot were an outer product, that would make it a $3\times 3$ matrix, which, in some sense, is even worse of a description!

Does anyone see or know what I'm missing? Thanks! — gogobera (talk) 18:54, 19 June 2009 (UTC)[reply]

Does he use the notation σ elsewhere? It might refer to the Pauli matrices which are a triple of 2x2 matrices, so it makes sense to dot them with a vector and get a 2x2 matrix. Algebraist 19:02, 19 June 2009 (UTC)[reply]

hmm. He hasn't defined them, yet. On p. 23 he writes "…when we discuss the Pauli two-component formalism in Chapter 3". On the other hand, the book expects some introductory quantum experience. I'll go with your suggestion though, for now, and see what comes out of it. Thanks! — gogobera (talk) 19:09, 19 June 2009 (UTC)[reply]

Oh yeah, and I know this is a math question, but it being in a Quantum text, I thought someone here might've had experience with it. I'll cross-post, I guess, but only if necessary. — gogobera (talk) 19:05, 19 June 2009 (UTC)[reply]

Is there a list of notation at either the beginning or the end of the book? --Tango (talk) 21:06, 19 June 2009 (UTC)[reply]

The

\sigma \,

are the Pauli matrices, as Algebraist sugested. That's why I don't like Sakurai too much. He doesn't explain things well enough. Dauto (talk) 05:11, 21 June 2009 (UTC)[reply]

June 20

Consistancy and Acceleration.

Apologies if this is in the wrong place. I'm still in training.

In many articles e.g. PCC streetcar, the unit of acceleration is given as mph/ps. In other articles, it's given as mphps (f'rinstance Washington Metro rolling stock).

What is meant is "miles per hour per second". So it seems to me that the correct unit would be mphps, without that extra slash(/), since that would be read as "miles per hour per per second".

Since there are over a hundred articles to be changed, it seems rather tedious to post the suggestion in each discussion page. Also, I'm not so sure that I'm correct (actually, I'm sure I am, but I have to maintain an appearance of humility), since it's possible that one use or the other is standard.

What do y'all think, should I be bold, or just let sleeping dogs lie. Bunthorne (talk) 02:30, 20 June 2009 (UTC)[reply]

Alternately, there's mph/s. Agreed that "per per second" is incorrect, so I recommend boldness (always worthwhile for obvious errors). — Lomn 02:49, 20 June 2009 (UTC)[reply]

I agree, mph/ps is wrong and mph/s is better then mphps. But where the unit occurs just once or twice in a text passage, I'd be inclined to forget abbreviating the seconds and just use "mph per second"; I think more people will easily understand that. --Anonymous, 03:21, June 20/09.

mph/ps is definitely incorrect. Fortunately, that senseless notation only exists in 3 articles. As far as what to change it to, I think mph/s is clearer than mphps, but mphps is used in twice as many articles as mph/s (14 vs. 7), so at first glance it looks like most editors prefer mphps. Red Act (talk) 03:26, 20 June 2009 (UTC)[reply]

mph/ps would be "miles per hour per picosecond". That's some serious acceleration.... --Trovatore (talk) 03:52, 20 June 2009 (UTC)[reply]

Not if the number before "mph/ps" were 0.000000000000000000000000001, for example. That might apply to the acceleration of a male smail when he sees his girlfriend in all her alluring, sultry seductiveness. -- JackofOz (talk) 07:16, 20 June 2009 (UTC)[reply]

Snails are hermaphrodites. (There's a Perry Bible Fellowship cartoon about snail sexism.) As for the units of acceleration, why not use feet per second per second? That way you don't have the confusion of two different time units in one compound unit. AlexTiefling (talk) 11:43, 20 June 2009 (UTC)[reply]

Because speeds of cars are usually measured in mph and they generally accelerate for periods on the order of a few seconds, so the odd mix of units is actually the most convenient. You can, for example, easily convert "0 to 60 in X seconds" (a common way of expressing acceleration off the line) to an average acceleration in mph/s. --Tango (talk) 16:56, 20 June 2009 (UTC)[reply]

I believe it is correct Wikipedia style to provide the customary unit (which should be mph/s in this context) followed by the appropriate metric unit in brackets (ms^-2) ? So I think you're free to go with mph/s as your customary unit - provided you also give a more "normal" unit for people who are not familiar with streetcars or who don't use "miles" as their natural unit. Think of your confusion if you were to be given the acceleration of an unladen european swallow in teaspoons per acre per square fortnight...you'd be quite justified in demanding to have the number in meters per second in brackets afterwards. SteveBaker (talk) 15:19, 21 June 2009 (UTC)[reply]

Notational point: the metric unit you speak of is not inverse square milliseconds. If you must write m/s² without using a slash, you need a space or a centered dot between the m and the s.

But is m/s² the appropriate metric unit anyway? In metric countries vehicular speeds are normally written in km/h, not m/s. This suggests that km/h per second would be more commonly used then m/s² for accelerations, but I don't know if that's true. And if this unit is commonly used, is it commonly symbolized as km/h/s (not proper SI style) or kph/s (also not proper SI style) or km/h s or km/h·s or km/s·h or what? I don't know; I haven't done enough reading of European materials where it might be used.

--Anonymous, 19:18 UTC, June 21, 2009.

Wikipedia style aside, Steve's ms^-2 is quite correct, and is the way I've always been taught to write such. You don't need the dividing dot unless there's going to be ambiguity — for example if you were also talking about milliseconds — but here it is clear that we're talking about acceleration in SI units so ms^-2 is metres per second per second. Actually with the -2 there I can't see how it could be confused anyway... nothings per milliseconds per millisecond?. --Polysylabic Pseudonym (talk) 09:02, 24 June 2009 (UTC)[reply]

I'm sorry, but you were taught wrongly. The SI allows national variations in the spelling of unit names, but the unit symbols are international and the standard is quite specific about forming them. In the edition of the standard linked in the following subsection, see page 44: "Multiplication must be indicated by a space or a half-high (centered) dot (·), since otherwise some prefixes could be misinterpreted as a unit symbol." Or if you prefer the original, see here at page 33: "Quand une unité dérivée est formée en multipliant deux ou plusieurs unités, elle est exprimée à l’aide de symboles d’unités séparés par des points à mihauteur ou par un espace." Thus ms^-2 can only mean square inverse milliseconds. --Anonymous, 22:19 UTC, June 24, 2009.

What is an SI unit?

I've split out this subthread into a separate subsection. --Anonymous, 22:12 UTC, June 22, 2009.

Yeah, I think when Steve said "metric" he meant "SI". --Tango (talk) 20:18, 21 June 2009 (UTC)[reply]

The hour is a non-SI unit, but is accepted for use with the SI and, as I said, vehicular speeds are commonly measured in km/h. --Anon, 21:59 UTC, June 21, 2009.

The SI unit for acceleration is m/s². Are you disputing that? --Tango (talk) 22:08, 21 June 2009 (UTC)[reply]

Only the first word. SI includes many units for acceleration: m/s² is one, km/s² is another, and so on. Additional units are accepted for use with the SI. --Anon, 07:52 UTC, June 22, 2009.

I've never heard of units with prefixes being called "an SI unit" they are just "the SI unit with a prefix". --Tango (talk) 14:44, 22 June 2009 (UTC)[reply]

I can't help what you've heard. The SI standard defines what units are part of the SI, and that includes the prefixed ones. (The link is to the US edition, but other editions will show the same thing.) By the way, that also includes the four prefixes in between milli- and kilo-; some people have the false idea that those are not part of SI. It is true that certain units are designated as SI base units -- the meter is the base unit of length and the second is the base unit of time -- but that's just a way of stating their definitions, and provides a convention for the construction of named derived units like newtons and watts. There is no base unit for acceleration, as it is derivable from units for length and time. --Anonymous, 22:12 UTC, June 22, 2009.

(deindent and rather late) Kilometres per second per second is rather an unusual measure, can't say I can think where it'd be used. Acceleration due to gravity, for example is in the region of 0.01km/s² or 10m/s² approximation was deliberate. --Polysylabic Pseudonym (talk) 08:56, 24 June 2009 (UTC)[reply]

Which wikiproject would best encompass an Electrical Pollution article.

Hey. I'm starting work on an electrical pollution article on my userpages. How this article doesn't already exist I don't know (Probably because of the electric companies that still try to claim that it's "false science")...

Anyways, I don't feel it's something I can do alone, and want to find some editors that know the subject a bit to help construct it with me. Which wikiproject would best cover this article? Earth Sciences? Natural Sciences? Physics? Energy? Or perhaps just the ol' Wikipedia:Editor_assistance/Requests page would be best for me. What is recommended? -- Floydian ^τ _γ 03:57, 20 June 2009 (UTC)[reply]

The content on your user-page article appears to be a less-than-accurate effort to describe Electromagnetic interference. Since we already have this article, any relevant information should be added there. "Electric pollution" is not a term in common use in radio-science or utility electric power. Wikipedia has a strong policy against coining neologisms, described here. If you feel that there are sufficient third-party reliable sources that use such terms as "electric pollution" you should find those sources. The burden lies with you, the editor, to back up such claims with reliable sources. The image you have posted, File:ElectricSineWave.jpg, does not appear to be out of the ordinary - in fact, the electric utilities document the frequency harmonics and phase/amplitude variations, and if you look closely at their technical information you will find that these variations are within the specifications they contractually agree to deliver. It is more likely that those "noise" sources, which you are viewing in the time domain, are due to load variations, not due to electromagnetic interference from cell phones or radio towers. If you don't believe me, consider looking at the frequency spectrum of electric power - there is not a lot of man-made radio activity in there, and when there is, you can clearly see it. Nimur (talk) 06:21, 20 June 2009 (UTC)[reply]

Isn't illness due to "electrical pollution" a myth? What's recommended for you is a sixth form/high school physics course......Alaphent (talk) 08:56, 20 June 2009 (UTC)[reply]

Please take your negativity and childish insults elsewhere. There are plenty of documents the back it and its effect on humans and animals up. This page lists plenty of research into it. The content on my userpage is a few days of piecing together some small things. It is far from complete and is not being placed here for peer review. ~~I will look into the article you linked and comment later.~~

EDIT: EMI is a cause. Electrical pollution is an effect. - Floydian ^τ _γ 09:06, 20 June 2009 (UTC)[reply]

Maaate, I fail to see where the "childish insult" in Alaphent's contribution there. As for the documents that back it up, there are documents that back anything up - and for that matter there are documents that will refute anything. Just because some "Alternative Medicine Scientists" think that it is a valid effect, it does not neccessarily mean that it is.

Anything you place on wikipedia will be criticised and reviewed, sometimes unjustifiably. Maybe it is slightly arrogant to assume that you can write an article perfectly by yourself? Perhaps consider creating the article and seeing how it goes from there? But here isn't the place for that discussion.Heinzcreamofchickensoup (talk) 09:38, 20 June 2009 (UTC)[reply]

After looking at your talk page and contributions, it seems that you have a "thing" about adding controversial unsourced "anti-establishment" information. Governments witholding information about drugs?Heinzcreamofchickensoup (talk) 09:48, 20 June 2009 (UTC)[reply]

(outdent). Wikipedia should also have articles on common conspiracy theories and junk science, as long as they are notable, so i see no problem with the concept so long as the article is balanced. There must be tonnes of credible research into this, even if it only debunks the idea. WP:SKEPTIC, WP:Pseudoscience, WP:Environment and WP:Energy all seem appropriate if the article is ever created. It is usually easiest to create the article and worry about projects after, although it is a good idea to get the projects opinions in this case, as we see even a refdesk question causes responses unpleasantly close to incivility and a determination to not answer the questionYob Mod 10:52, 20 June 2009 (UTC)[reply]

Floydian, please do feel welcome to contribute to Wikipedia. To the other editors, please avoid personal attacks. That being said, a few important issues arise:

Floydian - if your work is not to be subject to peer review, why are you asking for help? I'm a contributor to the WikiProjects you mentioned - Science, Energy, Physics, ... didn't you come here asking for input or help from these projects? You might not want to completely slough off other editors' suggestions, or they will be less inclined to help.
Your claim that "EMI is a cause. Electrical pollution is an effect" does not seem to make sense, because EMI is an effect of electric power coupling into places it shouldn't be. It's a symptom of a broad class of phenomena. If you disagree with this concept, you should do the following:
- Read electromagnetic interference very thoroughly
- Read about electromagnetism in general
- Read about electricity distribution
The claims that your article makes, and your incorrect use of technical language (for example, emf is neither the electric field nor the magnetic field) suggests that you are new to these terms. White noise is not RF interference. Your image of clean and dirty power conveys almost no scientific information, because it is an amplitude-versus-time plot (how about showing us a power spectrum?) Do you know the difference? Do you really feel comfortable to make strong claims about an area you know so very little about?
If you do, then perhaps you should publish your original research elsewhere, because Wikipedia is not the place to publish new ideas. You must find somebody else's published research and cite it. We will subject that research to fierce debate about whether it is reliable. Your two sources do not appear to be very reliable. Hint: any web page that starts off with an incorrect fact is likely to rank low on the subjective scale of reliability.
If you still believe that "electric pollution" belongs somewhere in Wikipedia, by all means be bold and add it in.

I can tell you honestly that this article will be edited severely, and probably deleted, because it fails several key criteria (most importantly, the lack of reliable sources; and secondly, the coining/definition of a new term which is not in common use in scientific literature). By submitting your work to Wikipedia, it will be subject to merciless editing, including deletion. If you do not like this idea, then Wikipedia is not the place to publish your ideas. That's why we have our warning on edit-pages: If you don't want your material to be edited mercilessly or redistributed for profit by others, do not submit it. Nimur (talk) 17:11, 20 June 2009 (UTC)[reply]

Childish insult: "What's recommended for you is a sixth form/high school physics course". First of all I want to ask which scientists are correct. The ones that are hired, and payed by the companies that want to sell the stuff to come up with "conclusive" research on the topic? Or the ones that do it on their own accord? How about the university of wisconsin, which has been studying the effects of this for 25 years? What defines scientific literature in this case? Who is more credible? The electric company, or the independent not-for-profit study? I can provide well over 30 published and accepted studies that go far more in depth into this subject then a bunch of average people who just feel like slapping a conspiracy theory label on anything that is new to them. I wonder how many people told Darwin that he was a conspiracy theorist?

I am looking for advice on where to ask for help. I'm not asking for people to criticize the 3 sentences that I've written so far. I'm looking for people that actually can back up their claims that this is not real or science.

My research is not original. Everybody that has commented here has made claims without any sort of backup. I'm not sure what you are talking about with my incorrect language use because the article really isn't written and once again isn't being submitted here for review in its current state.

EMI is a cause and Electrical pollution is the effect. This is the case because EMI is a term to envelop any sort of undesired electrical signals, and electrical pollution is the effect that these signals have on our cells and our bodies. —Preceding unsigned comment added by Floydian (talk • contribs) 17:33, 20 June 2009 (UTC)[reply]

If you are not going to help me (Or those of you who aren't), then shut up and don't reply - It isn't neccessary. I did not post this to be called arrogant or anti-establishment just because I don't believe everything that I am told, especially when Pfiezer is sponsoring it. -- Floydian ^τ _γ 17:29, 20 June 2009 (UTC)[reply]

I tend to believe scientists who follow proper methodologies, irrespective of who funds them. Post your 30 sources, and I'll take a look at them, with an open mind. My professional career is built on doing lots and lots of reading (Why else would I be browsing the Science desk on a sunny Saturday morning?), so it never hurts to throw 30 more papers at me. Nimur (talk) 17:43, 20 June 2009 (UTC)[reply]

Firstly, 6 of the 8 studies posted [9] are led by "Magda Havas". I don't know who she is of course (I assume female), but it would be good to check her out for any potential conflicts of interest (although she very loosely states there are none). Secondly, the studies aren't great. The first study contains 8 non-controlled cases. The second one isn't placebo controlled, relies on participant self-reports (instead of doing any objective measurements), and the actual experiments are related to multiple sclerosis and diabetes, yet it is concluded:

"Diabetes, multiple sclerosis, ADD/ADHD, asthma chronic fatigue, and fibromyalgia are all increasing in the population and the reasons for this increase are poorly understood. Dirty electricity may be one of the contributors to these illnesses."

Although she says "may", based on some self-reports (not discussed in the paper) really it is an irrelevant conclusion (as the decrease in pirates may have caused the rise of ADHD/fibromyalgia). Also "Table 1" - which states the symptoms of radio wave sickness - lists almost every common symptom there is. Seems like a case of the barnum effect applied to a disease. Another issue I have is this quote:

"GS filters have been placed in homes, offices, and schools. People report having better sleep, more energy, and less pain. They document cognitive improvements in memory and concentration"

Now there is no reference for this, although a few lines lower it does state something vaguely similar with the ref "Havas et al., 2004". Unfortunately the reference is this:

Havas, M., Illiatovitch, M., Proctor, C. (2004). Teacher and student response to the removal of dirty electricity by the Graham/Stetzer filter at Willow Wood School in Toronto, Canada. Presented at the 3rd International Workshop on the Biological Effects of Electromagnetic Fields, 4–8 October 2004, Kos, Greece.

This is where all the claims fall down for Wikipedia standards. A presentation in Greece is not a reliable source, but I decided to read it anyway (it is on the Electrical Pollution site). From a quick glance over the results, there is no significant difference between GS filters present and absent. In some cases the GS filters caused a reported positive response, whilst in other cases there was a reported negative response. In the bottom right corner of Table 1 it summarises the overall response, and it is clearly insignificant. In all of the results, there is only one case where the GS filters produced a statistically significant improvement, and that is in "unproductive time/class (min) in grade 4 students". Unfortunately it is not stated what statistical test was used, and the sample is still pretty small (18 in GS absent group and 14 in GS present group).

I can't really be bothered to read through any more of this, I'll put my trust in Nimur's conclusions if he/she reads the studies, or I will read for my self any double blind, placebo controlled lab experiments posted in scientific journals (not case studies). --Mark PEA (talk) 19:18, 20 June 2009 (UTC)[reply]

Ok people let me put this here plain and simple. I posted this here to find editors to collaborate with. NOT to get opinions. NOT to be told that the scientific body you believe in says it doesn't exist and thus it doesn't exist. NOT to be told I have no qualifications (Because quite frankly, since you are posting to the internet under a pseudonym, qualifications are irrelevent in this discussion. As per WP:NOR, every editor's qualifications are irrelevent). I do not need to prove anything to you, as you are just as qualified as I am.

Secondly, there is not one all-powerful all-knowing scientific body that declares things as fact or fiction. You do not have this power either. Thirdly, the GS filters are something I believe to be BS, and I myself will not introduce that to this article. Fourth, why is a presentation in Greece any less reliable than a presentation in America? You do not know the size or importance of this meeting, and your claim is unfounded. Fifth, lets see proof pointing the other way if you feel so strongly that it doesn't exist. Sixth, objective reports of "I feel sick" are just as valid as having some machine spit out a number that says "This means she is feeling sick". Seventh, 100 years of western medicine doesn't automatically invalidate several millenia of alternative and natural medicine. Eighth, is scientific research done by a company that sells the product it is "researching" proper methodology? By that standard, I should ingest half the pills I see on TV because I have one of the symptoms they list. Almost anything can be made to appear true. I feel myself that research done into a subject matter by a company that makes profit off that subject matter is not as valid as a third party's independent look.

Here are plenty of articles. They are hosted by electrical pollution.org (Which by the way, please back up your claim that this site is not reliable. The publisher is a big part of the studies conducted by the university of WI in Madison.), and each in themselves also reference countless published and reliable articles. I have not read through all of these yet, and only have them selected thus far as potential sources for information. First off, here is the requested power spectrums, published by Dr Martin Graham, Professor Emeritus at University of California in Berkeley. I admit I am not qualified and cannot read them. I'm an editor here though, not a scientist.

Granted, this is not 30. But again, I do not need to prove myself at this point. The article is not being submitted for review, I am looking for editors that want to collaborate with me and not against me. -- Floydian ^τ _γ 20:12, 20 June 2009 (UTC)[reply]

I would be happy to look at a draft. But you would do well to edit the existing articles or section which cover the topic. Right now it seems to be covered in Electromagnetic radiation and health#Health effects of electric power transmission. Additionally, cell phones, radio and television, and wireless broadband could be examined.They are covered in Mobile phone radiation and health Also leakage from microwave ovens, and occupational exposure to radar. There is Wireless electronic devices and health. There is some duplication. There have been many books and journal article published over the last 30 years or so dealing with the question of whether electromagnetic radiation from power lines (and more recently, from cell phones) causes cancer or problems with the immune system. The null hypothesis has seldom been rejected (of no effect). But a principle of "prudent avoidance" has led many to get rid of the electric blanket, and to avoid sleeping in the bedroom with only a brick wall between it ant the distribution line going overhead down the alley. It should be covered in an article, and I expect it is, somewhere. Early studies(Wertheimer and Leeper, 1979) just coded for the presence of power lines without measurements, and noted cancer cases. Later studies did measurements. Lifetime dosimetry of power line EMF exposure is difficult. Incidence of cancer among power company employees tended toward the null hypothesis. See Google book search at [10] for 215 books citing Wertheimer. Some are sensational crap, others are reliable sources. If "the power companies were covering it up" there would not be so many studies looking carefully at the effects. Edison (talk) 20:16, 20 June 2009 (UTC)[reply]

There are lots of studies, but many of them contradict the studies published by the power companies. The power companies almost always conclude "there is no such thing", while other studies almost always conclude that there is some sort of effect happening here, but that its not fully understood. -- Floydian ^τ _γ 20:21, 20 June 2009 (UTC)[reply]

You are wrong about the studies finding no measurable effect being published by the power companies. Read the articles/sections cited in my post above. Edison (talk) 20:27, 20 June 2009 (UTC)[reply]

I never stated that only the power companies publish these studies, I only stated that studies published by the power company (almost) always claim there is no measurable effect, or no noticeable effect on human health. If I am wrong, please link studies and not wikipedia articles for me to decipher and find sources in. My burden of proof doesn't lie on the reference desk, so can we please stop discussing whether or not my article is relevent? I am removing the link to my article in my userpages. It is irrelevent to what I am asking, and it seems that everybody is judging it no matter how many times I state that it is not in any way, shape, or form completed in any sense. It will be at least a C class article before I go ahead and publish it on the encyclopedia. At that point, everyone is free to make whatever comments they wish. -- Floydian ^τ _γ 20:40, 20 June 2009 (UTC)[reply]

Fourth, why is a presentation in Greece any less reliable than a presentation in America? You do not know the size or importance of this meeting, and your claim is unfounded.

Firstly, I thought it was quite clear from my sentence that I meant that any presentation is not a reliable source, whether it be in Greece, the USA or on Mars. Wikipedia requires evidence published in a scientific journal, because if not the presentations I've done at University could be cited and I could quack on about anything. Secondly, my claim is not unfounded. The "paper" that was discussed at the presentation was [11], and I discussed (not really 'claimed') its lack of significant results earlier.

Fifth, lets see proof pointing the other way if you feel so strongly that it doesn't exist

The burden of proof is not on me to disprove it. You prove to me that Russel's teapot doesn't exist, along with the Flying Spaghetti Monster.

Sixth, objective reports of "I feel sick" are just as valid as having some machine spit out a number that says "This means she is feeling sick"

No they are not. See: demand characteristics

Eighth, is scientific research done by a company that sells the product it is "researching" proper methodology? By that standard, I should ingest half the pills I see on TV because I have one of the symptoms they list

How would I know without looking at the studies? I have very little knowledge of electricity and "electrical pollution". What I do know is that when someone claims something to exist, they must provide solid evidence of its existence (as mentioned earlier re: burden of proof).--Mark PEA (talk) 11:39, 21 June 2009 (UTC)[reply]

Okay, I'm done. I can't take any more. I reviewed as much as I can, and I'm just ... well, did you even read the sources you provided? Three out of three reviewers strongly do not believe that EMF is a universal carcinogen. Half of your papers were self-published. Three apparently centered around an eight-person conference in Kazakhstan, a nation which (according to the conference brief you provided) conducts no research in this area. Nimur (talk) 00:05, 21 June 2009 (UTC)[reply]

Also, as I mentioned on your talk page, it is very ironic that you are critiquing "the scientific establishment" at large for conflict of interest, while citing reports that are little more than an advertisement for a bogus commercial "filter thingie". I believe that is the technically correct term for ... whatever this is. Nimur (talk) 00:36, 21 June 2009 (UTC)[reply]

The Wikipedia articles I found and cited above, in turn cite reliable sources. It is not reasonable for you to demand that I list the references here because it would be too much trouble for you to read the relevant articles and see what references are cited. Please provide a link to your draft article if you would like commentary and advice. One somewhat dated (from 1973) book I really liked was Power over people[12]," which criticized the EMF that utilities exposed people to, and encouraged ways of minimizing the effects. Edison (talk) 03:29, 21 June 2009 (UTC)[reply]

To answer Floydians question(!!!), possibly many projects, from Environment and Ecology to Industry and Electricity, not to mention various other projects this topic would fall under (I've seen four or five projects on a talk page many times), that is to say, so many you will probably just have to pick a couple you feel best, stick their banner on the talk page and invite them to come edit. Try to pick the ones that will gladly read it and wish to edit it, (I would go to Wikipedia talk:WikiProject Environment to ask, "Why is there not (or) which project is, the WikiProject for pollution" and ask more questions from there.) Everything you post on Wikipedia of a scientific or historical nature will be judged by the standard "Is that what they say on the Discovery channel?" (and it's true so don't give me a hard time for saying it) You may be everything from misled and idiotic, to unlearned and unable to speak English (I have heard these things many times but what you have here is certainly mild compared to the process at WP:AFD (deletions) where they won't even insult you, rather, just two or three people will say "don't beleive in it" and delete the whole thing forever, ignoring any arguements and feeling much worse than having some university students telling you to go back to school). There are strong arguements to say that human effects on global warming are about as strong as spitting in the ocean, but, you try to publish that or ask questions about it on Wikipedia you are a) saying the world is flat and b) claiming the holocaust didn't occur. Even articles about quite sensible scientific topics are easily deleted if, for instance, most of the work has been done by one person and he/she is not Albert Eintstein. For scientific theories you can have two things 1) previously published in a major English language/European scientific journal or 2) covered in high-ranking tabloids in a major English language speaking/European country. After that you have a) topics covered in websites that look or sound important (this will not count if the website covers only one topic so, on its own, electricalpollution.org will not withstand a deletion review here) and b) you have the Wikipedia Lottery that even though people ask to delete the topic, nobody wants to because amusing, interesting, signifigant or some other reason (and Electrical pollution will probably get a year or two on that last ticket unless it is truly absurd). I hope this is a helpful preparation for creating articles on more obscure scientific projects. If you can't read what I said, (I wonder sometimes) he said, "They will be more skeptical when they delete it and wont even suggest going back to school, try asking WikiProject Environment." ~ R.T.G 12:49, 21 June 2009 (UTC)[reply]

THANK YOU!!! You just did what about half a dozen people were incapable of doing. You answered the question that I actually asked! Thank you very much.

I don't know where in my 2 year absence wikipedia became such a disinclusionist community. Just because every scientist doesn't agree, or hasn't yet, doesn't mean a subject is not notable or that discussion on it can't persist. So many here just right away jump to researching away articles... Kinda defeats the purpose of calling wikipedia the "compendium of human knowledge". Should be changed to the "compendium of important human's knowledge".

And as I haven't released the article, the burden of proof does not lie on me yet. Further to that, I have produced several reports. No matter how much you contest them or their reliability, nobody has provided anything that proves that electricity and electromagnetic fields produces no effect on the environment. -- Floydian ^τ _γ 18:01, 21 June 2009 (UTC)[reply]

I beg to differ. RTG's answers are almost always wrong - check back through his history here on the science ref desk. What you really mean is that RTG told you what you wanted to hear...which may make you happy - but won't do you much good. The very first answer to your question was correct - what you are writing is either already covered by Electrical interference - or it isn't a referenceable topic for an article - which will indeed result in it being deleted. Wikipedia has grown up - we have standards - we are actively excluding junk. SteveBaker (talk) 21:59, 21 June 2009 (UTC)[reply]

And nobody has provided anything that proves that the Flying Spaghetti Monster, Russel's teapot, the Invisible Pink Unicorn, Steve Baker's Pink Aardvarks and an infinite number of other ideas don't exist, whilst others have produced reports on their existence (hence me mentioning them). That doesn't mean they are suddenly scientific truths. --Mark PEA (talk) 21:21, 21 June 2009 (UTC)[reply]

In fact, there is a type of human "allergy" to electrical emissions. It's called electrosensitivity. ~A H 1^(TCU) 00:58, 22 June 2009 (UTC)[reply]

Getting cancer and our destiny

I apologize beforehand if I am posting this in the wrong section...

I took a workshop a few weeks ago and the teacher mentioned that we choose our own destiny and people that get cancer choose to get it. Even though I don't agree with the second part, I am interested in an explanation to why some people believe this. I know this is not a place for discussion, but can someone please point me to where I can find more information about this? I am having a hard time finding it on my own.

Thanks for your time —Preceding unsigned comment added by 76.166.207.196 (talk) 05:45, 20 June 2009 (UTC)[reply]

You are basically asking, "Why does somebody choose to believe patent nonsense?" Some people are just stupid. I wish I had a nicer or more pleasant answer, but it's true. Explaining things scientifically, in simple terms, with factual evidence, building from simple ideas to complex consequences, is not enough to convince some people. These people are just stupid. Nimur (talk) 06:27, 20 June 2009 (UTC)[reply]

Yes, Nimur, I think you are largely correct... but those who choose to smoke cigarettes, let's just say, are choosing to increase their risk of a number of cancers unnecessarily. But otherwise, it sounds like the teacher may have been pretty ignorant on the subject of cancer. – Clockwork Soul 06:31, 20 June 2009 (UTC)[reply]

Sorry, I may have been a bit harsh. To remedy my harsh language, let me provide some helpful references. Many of our cancer articles have entire sections or at least some content related to misconceptions - I found a lot by searching for this combination. These articles may also point to off-site links, such as Popular Myths about the Causes of Cancer and Myths about HPV. You might find cognitive dissonance and ignorance useful articles. Although not about cancer, we have HIV and AIDS misconceptions; this may illuminate some persistent misunderstandings about health and diseases in general. Nimur (talk) 06:37, 20 June 2009 (UTC)[reply]

I believe there may have been a little bit of a misunderstanding about what I meant in my original question. I should have been a bit more clear, sorry for the confusion. When I mentioned people choosing their own destiny and choosing to get cancer, I meant choosing to get cancer in an indirect way, not in a direct way. I am sure no one really "chooses" to get cancer or really wants to get cancer unless they are crazy. I'm kind of having a hard time explaining what I am trying to say. The teacher did not really explain it, he just mentioned it. This was not a topic of the class, it is 2 courses from now, but I wanted to look into it beforehand.

I appreciate the links, I read all that stuff in school, I used to want to become a pharmacist so I have taken several biology courses, so I know all about all that stuff. When the workshop instructor mentioned destiny and cancer I disagreed, but I am very open to other people's opinions so I wanted to look into it. —Preceding unsigned comment added by 76.166.207.196 (talk) 08:49, 20 June 2009 (UTC)[reply]

The placebo effect is a real and measurable effect that depends on belief. I can think of no scientific reason that a "negative placebo effect" couldn't cause illness in people based on their beliefs. Psychological states have been shown to effect the immune system (eg. clinical depression), so why can't believing you will get ill do the same? Resisting pseudo-scientific nonsense (of which there is a lot!) does not mean we should ignore real possibilities.

That said, i expect the teacher will actually talk about subconcious changes in life-style that pre-dispose people to certain illnesses, rather than direct psychosomatic effects. YobMod 10:47, 20 June 2009 (UTC)[reply]

Your question is pretty meaningless without context (is it a science setting, social, philosophical, religious?) and your offhand response I read all that stuff in school kind of implies that you are not really listening to any kind of answer you get at the science desk. But to have a try at it, possibly the point being made was that everyone arrives at the point they are at in their life due to the decisions they have made on the way. In that respect your decisions are responsible for the situation you are now in whether or not you could foresee, or intended them. But that is little more than a truism and has no scientific value since it is completely devoid of predictive power or falsifiability. SpinningSpark 11:09, 20 June 2009 (UTC)[reply]

Re: YobMod's comment about the "negative placebo effect": Here is the article: Nocebo effect. --NorwegianBlue^talk 13:50, 20 June 2009 (UTC)[reply]

Wow, that's a facinating read - many thanks for the link. We have articles on everything!YobMod 14:06, 20 June 2009 (UTC)[reply]

The teacher may have been referring to the concept of karma or spiritism, which are not scientific and so don't belong in this section!--TammyMoet (talk) 15:59, 20 June 2009 (UTC)[reply]

I saw a bumper sticker that said "Sorry, my karma ran over your dogma." Edison (talk) 03:34, 21 June 2009 (UTC)[reply]

The teacher most certainly was talking about the relationship between behavior and cancer. Lung cancer, for example, has a VERY strong positive correlation with smoking; the incidents of lung cancer are very low in people without exposure to cigarette smoke, or in some cases with other environmental concerns, like asbestos exposure. Yes, there are anecdotal accounts of people getting lung cancer for no reason, but these are not statistically significant; at the actuarial level (i.e. when looking at millions of cases) there is an extremely strong correlation between lung cancer and enviornmental factors, especially smoking. Likewise, there are some correlations between colon cancer and diet; though less strongly so. Our articles on lung cancer provide the evidence and are quite well referenced to reliable sources. Thus, you have a case where the #1 cancerous cause in men, and the #2 cancerous cause of death in women, has a 90% correlation with a chosen behavior (smoking), then the teacher's comment, while certainly glib, is not entirely inaccurate. --Jayron32.talk.contribs 22:24, 25 June 2009 (UTC)[reply]

mecca

Does the city of mecca really lies on the Golden mean point of Earth??? They claim that the ratio of the distance from the North Pole to mecca and from mecca to South Pole is exactly equal to the Golden Mean Ratio which is supposed to be a standard ratio followed by the Supreme Being in the design of the entire universe. —Preceding unsigned comment added by 121.246.174.130 (talk) 13:38, 20 June 2009 (UTC)[reply]

I'm confused - wouldn't every place at that latitude have the same ratio of distances to the poles? For it to be a point, doesn't the longitude have to be defined too?YobMod 14:08, 20 June 2009 (UTC)[reply]

Yes, it would be everything on a line of latitude. Let's see, though -- Mecca is at 21°25' N, so it's 68°35' to the North Pole and 111°25' to the South Pole. The Golden ratio is ~1.618. Mecca's latitude ratio, South to North, is 1.624. Close, but not quite. Of course, the ratio of North to South is way off, about .616. So no, this is not true. — Lomn 14:13, 20 June 2009 (UTC)[reply]

For what it's worth, we can work out what the latitude of the Golden ratio circle would be -- it's 90-(180/(1+φ)), which is 21°15' S if you want your north-to-south ratio equal to φ. — Lomn 14:15, 20 June 2009 (UTC)[reply]

The Chicxulub crater seems to get rather closer though, do you think God is trying to tell us something? SpinningSpark 14:55, 20 June 2009 (UTC)[reply]

It might be pointed out that it doesn't matter much if you divide the larger part by the smaller and compare it to φ = 1.618... or divide the smaller part by the larger and compare it to 1/φ = 0.618... Sure, the former is the one that gets the Greek letter, but it's really no more special than its inverse. So saying that 0.616 is "way off" is a little much—it's slightly below 0.618, for the very same reasons that its inverse is slightly above 1.618. (I don't doubt you know this, but the OP might not.) —JAO • T • C 16:01, 20 June 2009 (UTC)[reply]

Of course, given enough constants, reference points, units of measure, etc. some sort of cosmological significance can be found for thousands of locations in the world. And if God/Allah was trying to send a message by the location of Islam's holiest city, I don't think it would have really cost Him much more effort to be a bit more precise. 64.252.193.6 (talk) 19:34, 20 June 2009 (UTC)[reply]

Maybe he was precise - how much have the tectonic plates shifted since Mecca started being an important place in Islam and in what direction? (I'm clutching at straws here, admittedly, but if you are going to rule it out on grounds of precision it is a question you need to answer (I'd rule it out on grounds of "What would be the point?", personally!).) --Tango (talk) 19:50, 20 June 2009 (UTC)[reply]

With respect to the african plate (which is taken as nearly stationary), the arabian plate is moving at about 20 mm/yr to the north, so since the time of Ibrahim (or Abraham) when according to Islamic tradition Mecca was founded around 2000 BC, that's about 80 m north, so not very far. Mikenorton (talk) 20:13, 20 June 2009 (UTC)[reply]

I'd prefer it relative to the North Pole. You also need to account for the North Pole moving due to axial shift/precession/whatever. --Tango (talk) 20:18, 20 June 2009 (UTC)[reply]

Why has no one mentioned Ley lines in this post yet, are all the fringe theory nutters on holiday today? SpinningSpark 21:16, 20 June 2009 (UTC)[reply]

Several independent points, not intended to argue to any conclusion:

It's not just the whole line of 21°15'N, or more accurately 21°14'46"N, that meets the criteria; it would be equally notable if the two distances were in the reverse ratio, so the whole line of 21°14'46"S qualifies as well.
The city of Mecca is not a point, so it's not accurate to say that the whole city is "at" 21°25'N. But the city's not so large that it extends to touch the line of 21°14'46"N latitude. Looking at Google Maps satellite imagery, that line of latitude misses the built-up area by about 10 km.
Because the Earth is not a sphere, there are two different ways to measure latitude. Geographers use geodetic latitude, based on the direction of the local vertical at a place. But it would be equally valid, if less convenient, to use geocentric latitude, based on the direction to the center of the Earth, which gives slightly lower values. According to Latitude#Comparison of selected types, the difference at the latitude of Mecca is about 8 minutes, which means that 21°15'N geocentric latitude just about skims the south edge of the city's built-up area -- I'd need to do a more accurate conversion to be sure whether it hits it or not.

--Anonymous, 23:59 UTC, June 20/09.

"It's not just the whole line of 21°15'N, or more accurately 21°14'46"N, that meets the criteria; it would be equally notable if the two distances were in the reverse ratio, so the whole line of 21°14'46"S qualifies as well." -- Hey, isn't that the latitude of Rio de Janeiro? 76.21.37.87 (talk) 05:43, 21 June 2009 (UTC)[reply]

No. Algebraist 20:09, 21 June 2009 (UTC)[reply]

Right, it's 22 deg. 54 min. S, or about 100 miles south of the 21°14'46"S line. I stand corrected.

76.21.37.87 (talk) 00:08, 23 June 2009 (UTC)[reply]

niper-2009

i got 2824 rank in niperjee 2009 n i hav sc reservation n female .......will i get a seat in niper institutions? —Preceding unsigned comment added by 117.195.181.1 (talk) 15:32, 20 June 2009 (UTC)[reply]

Googling niperjee only results in 26 matches...if you could be more specific it may helpHeinzcreamofchickensoup (talk) 16:15, 20 June 2009 (UTC)[reply]

It seems to be a reference to this. --Tango (talk) 16:48, 20 June 2009 (UTC)[reply]

We have an article on National Institute of Pharmaceutical Education & Research (NIPER), and presumably this question is referring to the NIPER Joint Entrance Examination test. You should contact individual schools with regards to their admissions standards, I don't think Wikipedia keeps rigorous statistics on admissions requirements in any of our school or university articles. You should be sure to use proper spelling and grammar when contacting these schools, as informal web-speak is generally not well regarded in the context of university admissions. Nimur (talk) 17:34, 20 June 2009 (UTC)[reply]

Sigfigs

As part of a chemistry assignment, I have to do the arithmetic problem 8.937–8.930 to the correct number of significant figures. The obvious answer would be 0.007, which, since leading zeros are not counted as significant, would have only 1 significant digit. Preserving the answer with 4 sigfigs such as both 8.937 and 8.930 have would yield the answer 0.007000, which seems ridiculous. Which one is it, and why? 64.252.193.6 (talk) 17:11, 20 June 2009 (UTC)[reply]

Addition and subtraction do not preserve the number of significant digits. They only preserve the accuracy of the result. This can increase or decrease the number of significant digits from the input (for example, consider the exact addition of 3 + 8 = 11. The inputs had 1 digit each, and the output is an exact answer with two significant digits). For more subtleties of the rules regarding significant figures, check the article. Your correct answer is 0.007, with only one significant digit. Nimur (talk) 17:30, 20 June 2009 (UTC)[reply]

Significant figures are a pretty useless way of expressing precision (because of problems like this) and are virtually never used at a higher level. For that reason, the "right answer" is simply whatever is on your teacher's answer sheet. --Tango (talk) 17:46, 20 June 2009 (UTC)[reply]

Keeping aware of sigfigs is quite important to avoid expressing a result with too many digits. They are always used at "higher levels" by anyone hoping to publish a result without being laughed at by editorial reviewers at a journal. Edison (talk) 20:04, 20 June 2009 (UTC)[reply]

No, they aren't used. The actual precision is stated. For example, you may see a value quoted as "4.586(34)" (the number is brackets indicates the precision) or as "1.65 +/- 0.023", or sometimes other notations. You virtually never see a number written with the precision given simply by the number of significant figures. --Tango (talk) 20:26, 20 June 2009 (UTC)[reply]

Additional question: for the problem (5.1 + 6.3) * 0.245 (just an example), do you give the answer to 2 sigfigs as in 5.1 and 6.3, or do the addition first, change the equation to 11.4 * 0.245, and give the answer to 3 sigfigs? 64.252.193.6 (talk) 21:47, 20 June 2009 (UTC)[reply]

I'd work it out using "interval arithmetic". You interpret 5.1 as 5.1 +/- 0.05, etc. and then work out what the smallest answer you can get is and what the largest is. In this case, that's easy - the smallest is by using the smallest value for each term, so you have (5.05+6.25)*0.2445=2.76285, and the largest is similar: (5.15+6.35)*0.2455=2.82325. You can then say the answer is 2.79305 +/- 0.0302. If you really want it just in terms of significant figures then you find the most figures you can do without giving false precision. In this case, that would be 2 sig figs, or 2.8, since that means 2.8 +/- 0.05, so the smallest possible value is 2.75, smaller than the real smallest value, and the largest is 2.85, larger than the real largest, so we're not stating any false precision. If we added another significant figure we would be narrowing the range too much and it would be false (you can work out the numbers for yourself!). --Tango (talk) 22:29, 20 June 2009 (UTC)[reply]

Tango's "interval arithmetic" assumes that the figures in the example problem are quantised approximations. But if that is not stated then it is reasonable to take them at face value. The answer is 2.793. Exactly. Cuddlyable3 (talk) 23:31, 20 June 2009 (UTC)[reply]

If we are talking about sigfigs and rounding then obviously we are in the context of uncertain data. --Tango (talk) 23:58, 20 June 2009 (UTC)[reply]

Not true that is is un-used past school. I often weigh small amounts to 0.000001 g precision, but i ony report the result down to 3 s.f. as that precision is not needed. Sigfigs usually do not mean the one has uncertain data, just that further precision is useless. This is probably why you do not find them often in other fields - it is often possible in chemistry to measure variables far more precisely than we ever need to: this is not uncertain data. It would be difficult to find any Organic Chemistry Professor that ever reported errors in simple measurments or even had the possibility to calculate them (they would need a full time postdoc position just to continuously calibrate and validate machines), so sig figs are the best one can hope for. Physics is not the only science around! :-)YobMod 12:57, 21 June 2009 (UTC)[reply]

You might report your final results to 3sf, but I would hope you either keep the full precision while doing the calculations or keep track of the precision properly. If you don't, you run a very high risk of getting the wrong answers. --Tango (talk) 15:35, 21 June 2009 (UTC)[reply]

I keep them, but never use them. Percentage yields are always reported to the nearest percent - so 3 sf is already far more precise than needed when weighing products for example. Keeping track of errors is nice in theory, but practically not possible - i wouldn't even know how to estimate systematic errors produced by the balance, and would not have time to do so even if i could, and any error study would be unpublishable as non-novel. This is the case for a large portion of scientific endevour.Yob Mod 08:51, 22 June 2009 (UTC)[reply]

Sigfigs are a somewhat useful rule of thumb - but they shouldn't be regarded with the same religious furvor that they are taught in most schools. Keeping careful track of error limits is a much better way to manage error tracking. After all - what's so special about base 10? If you're working in base 2, what do you do about preserving significant digits? (You CERTAINLY arrive at a different answer that way!) Very often, the concept of sigfigs goes horribly wrong because of the order of operations - you can get a different "significance" in your answer if you calculate AxB+AxC than if you do Ax(B+C). So the whole concept is very approximate - and should be treated accordingly. Of course if you have to get through a high school exam - do what the teacher says - get your passing grade - and THEN treat this technique with the lack of respect it deserves! SteveBaker (talk) 15:09, 21 June 2009 (UTC)[reply]

The error I was referring to above is the obvious one of measuring diameter as 75 millimeters, multiplying it by pi and reporting the circumference as 235.619 mm. That would get a manuscript sent back by return mail, and should get points taken of in a lab or exam. It is a sort of error that became very common among high school and college students in intro science courses after calculators became common, which was rare when all used slide rules (good to about 3 digits). Edison (talk) 18:09, 21 June 2009 (UTC)[reply]

Sure, but it's not that you need to quote to an appropriate number of sigfigs, it's that you need to quote to an appropriate precision. If the diameter was measured accurate to the nearest millimetre at 75mm then you would quote the circumference as 235.6(16), or something (in some contexts you may specify a few more decimal places, but I see little point). That is significantly more useful than quoting "240mm (2sf)", which is what you would do if you followed the standard rules taught in schools. --Tango (talk) 20:15, 21 June 2009 (UTC)[reply]

That's a really good example - let's do it the proper way - preserving the information we actually have: If you know the diameter is 75mm (plus or minus 1mm) then the circumpherence is 235.619 plus or minus 3.14159 mm). To put it another way, if the diameter is between 74mm and 76mm then we know that the answer lies between 232.4778mm and 238.7610mm. The sigfigs approach says that the answer is 240mm plus or minus 5mm...which is far from the mark! It's unnecessarily increased the error bar at the top end by 2.3 millimeters - implying that the answer could be as large as 245mm (which is in fact impossible) - and at the bottom end, it's saying that the smallest the answer could be is 235mm - when in truth, it could be 2.5mm less than that: 232.5mm! That's very, VERY wrong - completely unscientific - mathematically untenable! By using the sigfigs approach we've widened the error range from it's true value at one end and limited the possible error at the bottom end.

But it's worse than that - we arbitarily decide to round to the nearest DECIMAL digit! Why decimal? Because it's kinda convenient when we're working in base 10...because humans have 10 fingers! That's not good math nor good science. Mathematical statements should be independent of the number base you choose. If we did the math in binary notation and used the "sigfigs" approach, we'd say that the diameter is 1001011mm (rounded to the nearest millimeter). The circumpherence comes out of your pocket calculator as 11101011.100111101mm - which we'd have to round to 7 binary digits: 11101100mm...which in decimal is 236mm. 240mm is 11110000mm in binary. So by choosing to impose these supposedly universal rules - but in a different number base - we get a different answer! If you do the math in hexadecimal (base 16) you get an even more vague answer! This is ridiculous! Science and math shouldn't depend on how many fingers you have! Why is base-10 sigfigs treated as "The Right Way"?

The true and only valid reason to teach this approach is to use as a rough rule-of-thumb to prevent people stating ridiculous amounts of precision - but by codifying these ridiculously complex (and wrong!) rules - you are misleading people into believing that its "The Right Way" to do science...which is far from the truth.

SteveBaker (talk) 21:35, 21 June 2009 (UTC)[reply]

Side Note: The Drake Equation is uncertain by as much as 20 orders of magnitude! (hence SETI is little more than pseudoscience and hope). ~~ Ropata (talk) 04:33, 25 June 2009 (UTC)[reply]

How big a population is needed to sustain the current technological society?

If the world's population is too small, a lot of the technologies that we have would be infeasible due to a lack of economy of scale. For example, if the world's population were a mere million, it would be too small to support a space exploration program. There are many other examples I can think of. Has anyone come up with a (well-reasoned) estimate of how big a population is needed to sustain the current state of technology? --173.49.12.233 (talk) 18:41, 20 June 2009 (UTC)[reply]

I think it is going to depend on the details. For example, if the population shrank due to wiping out everyone living in sub-Saharan Africa that might well improve the state of technology in the developed world due to the reallocation of resources currently going on humanitarian aid to that region. Another key detail is how spread out the remaining population is. If there are a million people left spread out all over the world, chances are good that they will be unable to remain very technological at all due to an inability to sustain reliable electricity production (a diesel generator per family would work at first, but you would struggle to produce and distribute the diesel). A million people all in one city wouldn't have any problem there at all. --Tango (talk) 19:47, 20 June 2009 (UTC)[reply]

Why could a population of a million not support a space exploration program? If they were all the "right" kind of people, like Wikipedia users say, and had access to present-day industrial plants, libraries and an abundance of the resources that 6 billion people consume today they could achieve anything they wanted. Look at it this way: You are the latest of a long line of ancestors none of whom failed to develop, thrive and explore whatever the current population was. Apropos electricity, the Internet could be run on hand generators. Cuddlyable3 (talk) 23:23, 20 June 2009 (UTC)[reply]

The cost per person would probably be too high if the only return was scientific development. --Tango (talk) 23:57, 20 June 2009 (UTC)[reply]

A keyword here is "specialist" --- one would not be able to have specialist doctors for all sorts of "advanced" diseases, for example, if population was too small. Similar for space engineers, etc (and even carpenters and similar if population becomes very small) Jørgen (talk) 00:45, 21 June 2009 (UTC)[reply]

I've searched around the articles on wikipedia concerning societies, civilizations and trying to find models for these. These aren't the fields best covered on Wikipedia, as is understandable giving the intricate models required by even simple questions on the subject. This has already been explained to some extent: Given different factors (population spread or centered), the answer will vary. Until exact numbers are provided, the solution is not... quantifiable, and a mathematical model would be abhorring. For instance, a population requires a constant source of food. Too small a population, and any dent in the agricultural production can have severe consequences. If there is any step back in technology, so to speak, each service's output (agriculture, industry, medicine and so forth) will diminish by a certain bit, and the society can support itself less, possibly spiralling downwards. This is of some importance since you ask "current technological society", which suggests there is a benchmark already to which we can hold all offices and organizations.

One could also add that some industries that exist today rely on multi-million markets (units or buyers) for them to be able to progress financially and thus lend their money to research. The answer to your question, for now, will be that no such thing exists, although I am afraid of answering so absolutely. 90.149.144.31 (talk) 11:10, 21 June 2009 (UTC)[reply]

It's a tough question - certainly it took the combined skills of at least a million people to get a man on the moon. Between skills in electronics, software, propellants, engines, aerodynamics, biology, machining, space-suit design, parachute technology, helicopter piloting...you name it! So I think a million people would make that difficult - but perhaps not impossible. Certainly it could be done as a multi-generational thing. We would have to be very careful to preserve knowledge from one generation to the next because it's perfectly possible for one entire generation to have not one single expert in some obscure field like (say) quantum chromodynamics - but you'd want to be sure that such a thing would not be forgotten forever. Education would be very important - and ensuring that we did not have too many people crowding into one area of study to the extreme neglect of another would be tough. But consider it like this...if we imagine that Wikipedia represented the whole of human knowledge (at least in scope, although obviously not in depth) - then with 2.8 million pages and 1 million people - each person would only have to be a 'deep expert' in the subject areas of roughly three articles to have all of human knowledge fully represented. But an awful lot of those 2.8 million pages are things like rock bands, TV shows, movies, descriptions of cities, biographies characters in "The Simpsons"...things that humanity doesn't need to have live, human experts on. We could have a dozen "history of music" people and another dozen "history of TV shows" people who would be able to keep the necessary information "alive" and be available for consultation as needed - so we could still afford to have 1000 mathematicians, 1000 biologists, etc. My guess is that if we considered the topics that are more than mere listings of information (things like math, chemistry, etc) - then we might have less than a million articles that "matter". So one person could be the world expert on (say) Aardvarks - another on Boyles gas laws, another on Xeno's paradox...those are awfully narrow areas of study. So I think the knowledge and skills we need could be retained by a million people. The difficulty with a space mission is that you might need (say) 1000 software engineers to write the software. There might (just) be a thousand software engineers in the world - but could we spare them all on getting a man to mars? I don't think so.

But (since this evidently relates to the earlier sustainability question), I think 1 million people is too few. 10 million or perhaps even 100 million would be a more realistic target. With that number of people, I think humanity could have a few dozen MAJOR projects being worked on in each generation and still have enough people to produce food, repair machinery, etc.

Space missions might become a thing of the past - or they might be considered important enough to be the main work of an entire generation - or something that we'd be happy to take the "long view" of and stretch over 10 generations. Certainly the work of mankind would have to be a more 'focussed' affair - there would be little scope for petty bickering about what would be the work of this generation.

But with no more worries over food shortages, energy shortages - with everyone being able to live on large estates with comfortable lives - with everyone having the responsibility to be THE one singular world expert on something that matters to them - I'd hope that the world would become a more peaceful, relaxed place than it is now. Fighting wars would become exceedingly difficult with so few people spread out so widely! There could probably only be a few thousand soldiers in the world - dropping a nuke on a "major city" might kill a few dozen people. That could be serious in terms of loss of expertise in some key areas - but nothing like the scale of horror such a thing would mean today.

SteveBaker (talk) 14:59, 21 June 2009 (UTC)[reply]

If you only have one expert on each area you could keep current knowledge alive, but it would be difficult to develop new knowledge. A lot of academia is focused around collaboration. Without anyone the exchange ideas with, new work would dramatically slow down (by more than just what you would expect from fewer people working on it). I would expect people to live close together, rather than all spread out. You can live a much more comfortable lifestyle that way, so a well placed nuke could wipe out a sizeable portion of the world's population. --Tango (talk) 15:32, 21 June 2009 (UTC)[reply]

I think I've mentioned before, but there is a very very bad historical precedent for these sorts of societies, where individuals exist solely because they are "needed." What happens when you have un-needed individuals? Do you euthanize? Even the most effectively planned society will experience environmental and situational changes that will skew the instantaneous need for certain professions and certain individuals. Pol Pot claimed he only needed about one million Khmers for his ideal society; and everyone else was ... well, no loss. All for the benefit of the Planned Society where everyone had a proscribed job and glorious equality among the classes! The idea of having to breed exactly the correct number of individuals, and then forcing them into a particular career path, seems to be a major step backwards in human society. It's important to keep in mind that in our society, even the most unproductive individuals, who are of no "use" to some particular agenda, still have a right to exist. Nimur (talk) 23:36, 21 June 2009 (UTC)[reply]

Heating canned goods directly

I seem to remember reading or hearing many years ago that it was a very bad idea to heat canned food directly over a heating element in the can (say a low flame on the range top). Now, mind you, I am not talking about an unopened can! The pressure danger there is or should be evident to most people. Is this true? If so, why? The only thing I can think of is leaching of the metal but most modern store bought cans are made from steel (not mercury or lead etc.)--141.155.143.180 (talk) 19:47, 20 June 2009 (UTC)[reply]

Someone asked this question on Yahoo. Hopefully someone here can corroborate the answers. Sifaka ^talk 19:56, 20 June 2009 (UTC)[reply]

Someone at Yahoo answers correctly pointed out that it is cooked in the can during the canning process. How would stove-heating be worse, unless it got hotter than at the cannery? Edison (talk) 20:02, 20 June 2009 (UTC)[reply]

Assuming the paper label will not be catching fire, then there is the question of any lead in the solder sealing the can, or any chemicals in the coating inside the can which could leach into the food. Many years ago, I recall a vending machine which had cans of chilé and soup kept hot inside and dispensed hot when purchased. Such long-term heating would probably be worse than brief heating on the stove. If steel, the cans are likely coated with tin inside. I have seen some which appeared to be coated with zinc inside, from the mottled appearance. Edison (talk) 20:00, 20 June 2009 (UTC)[reply]

Thanks for the answers. I think I'll refrain but I was curious.--141.155.143.180 (talk) 20:35, 20 June 2009 (UTC)[reply]

In addition to the can interacting with its contents, the bottom lid is crimped to the side walls. The bottom lid is designed to disburse impact stresses and resist heat expansion of the content at temps. around boiling. It is not designed to deal with the heat expansion caused by direct exposure to temperatures above 1000°F. It is likely to warp, which is in turn likely to put strain on the crimping and the seam on the side of the can. Material failure can be instantaneous and is unlikely to be pretty (launched lunch). The fact that the can not being the right size for your heating element the uneven heat absorption will damage the heating element of your range will probably be the least of your worries. 68.208.122.33 (talk) 21:21, 20 June 2009 (UTC)[reply]

This article cites reports that when taken together could imply that the food in 0.5% of tested cans (that's a LOT of cans) contained enough tin to cause nausea, vomiting, and diarrhoea. Heating of acidic food like fruits and vegetables may exacerbate this. Cuddlyable3 (talk) 23:07, 20 June 2009 (UTC)[reply]

I do not see how a can of food, with some liquid content, could be heated anywhere near 1000 F on a stove burner. In fact, it is possible to boil water in a paper bag over open flame (Ref: Michael Faraday, Mr. Wizard). The content keeps the container cool. The can should not get much above 212F/100C. Edison (talk) 03:39, 21 June 2009 (UTC)[reply]

Agreed. Also about the canning process being far more harsh than any reasonable re-heating method. It seems some canned food may contain tin, but cooking food in the can should do nothing to increase this level significantly. And cans can easily maintain their shape in a camp-fire. Cooking canned beans on the camp-fire is done all the time, and i have never seen any ill effects.Yob Mod 12:48, 21 June 2009 (UTC)[reply]

A can is made of thinner material than a pot. This accentuates any of the contemplated problems above. I doubt there is any problem involved in placing an opened can (of food) inside a pot of water and then heating the water, resulting in the contents of the can becoming heated. Something like a trivet could even be placed beneath the can to further separate it from the source of heat. Bus stop (talk) 13:55, 21 June 2009 (UTC)[reply]

But there is no need. A can can easily withstand the direct heat of a typical camp fire. Don't belive me? try it, the same as 1000s of people do every day. Repeated experimental observations surely count for something - any experienced camper should have seen this done, even if they prefer to carry around pots and pans. Camprecipes says it works for any canned food that just needs heating.Yob Mod 14:26, 21 June 2009 (UTC)[reply]

(un-indent)There may not be much of a need. But it is probably best to utilize low heat. And it is probably best to try to endeavor to apply heat in a way that doesn't concentrate it on one spot on the can. Any possible failure in the materials or construction of the can is likely to be exacerbated by both high heat and very unevenly applied heat. Bus stop (talk) 14:40, 21 June 2009 (UTC)[reply]

My guess would be that the canning company would use a label saying not to heat in can so that someone does not try heating up an unopened can and sue the company. 65.121.141.34 (talk) 14:26, 22 June 2009 (UTC)[reply]

Aren't some cans plastic lined -- to battle the metallic taste caused by direct contact of metal and acidic foods? --70.167.58.6 (talk) 14:38, 22 June 2009 (UTC)[reply]

"Homeopathic"?

In the spirit of AGF, I'm going to put this under "Science". I started to feel the symptoms of a cold coming on while visiting my family and my step-mum offered me a treatment that was apparently popular in the US (where she lives). It was some kind of spray that you apply to the back of your throat containing zinc and said on the packaging that is was "homeopathic". My understanding of homeopathy is that the remedies contain (prior to dilution, anyway) organic substances understood to be the cause of the malady. That suggests that this zinc thing wasn't actually homeopathic. In discussion with her, we came to the conclusion that the term in used in the US for any complementary medicine. Firstly, is this true? Secondly, does anyone know what this zinc treatment was and whether there is any evidence to support the claims? --Tango (talk) 20:09, 20 June 2009 (UTC)[reply]

A few comments for Tango. It is true that some people who don't understand what homeopathy really is may sometimes use the term to mean alt med, but that's an obvious misuse. Homeopathy is just one of many forms of alternative medicine, IOW untested, unproven, or disproven methods. (That doesn't mean they can't ever be proven to be effective, but it's increasingly rare for that to happen.) Homeopathic "remedies" are based on the use of substances which in their undiluted form would cause the same "symptoms" as a disease, which is not the same as using what would actually "cause" the malady. That means that extremely many substances can be used as the starting base for many preparations to treat ONE malady. This is based on the pseudo-doctrine of signatures. It sounds symmetrical and appealing, but it's nonsense in the real world when the rubber meets the road. Homeopathic remedies can be made from organic and inorganic substances, and even from things so exotic as moonrays and starlight. This is simply an expression of the fact that to be able to believe in homeopathy, one has to have some form of fundamental defect in logic, but that only applies if one really understands how it really "works". Otherwise such belief is just based on ignorance and what "sounds" appealing and superficially logical. As one guy put it: "Homeopathy is bullshit. Only very, very diluted. It's completely safe to drink." - Peter Dorn. Also: "Homeopathy is God's way of thinning the flock". - dpr; and "Homeopathy, where a little of nothing is better than something at all." - Jeanne E Hand-Boniakowski, R.N.[13] It's all an interesting subject. -- Brangifer (talk) 02:38, 23 June 2009 (UTC)[reply]

The Mayo Clinic says of zinc cold remedies that they "probably don't work", and WebMD says studies are "inconclusive". Still, if you take enough of it, there's some chance you'll develop some kind of super-power, and will fight crime as Rust Resistant Man. 87.115.17.119 (talk) 20:18, 20 June 2009 (UTC)[reply]

The article Zinc gluconate cites reports about cold treatments containing zinc and mentions a warning on 16 June 2009 from the FDA about nasal products from Zicam. The Zicam article cites a NY Times report on the same date that the manufacturer has withdrawn Zicam from the US market. It was (or is) marketed as a homeopathic remedy with some additional ingredients. Please see the articles concerned. Wikipedia can only cite reliable sources and will offer no medical advice. Of course you know that but it had to be said. Be cautious and get well soon. Cuddlyable3 (talk) 22:52, 20 June 2009 (UTC)[reply]

Thanks for the kind words, but the cold never really materialised (which isn't uncommon for me - I must have a good immune system). I think some of the symptoms were actually caused by dehydration, which I worked out a little latter and treated homeopathicly by drinking lots of plain water! (I would have switched to rehydration salts if necessary, so you don't need to warn me about the perils of rehydrating with only water!) --Tango (talk) 01:20, 21 June 2009 (UTC)[reply]

Oh - my - God - Tango. Don't you know that that "plain water" contains the succussive remnants of every other homeopathic remedy ever applied? And they've been getting ever stronger with dilution. This can be simply proved by the fact that water flows to the ocean, which is succussed by gravity waves, so you've clearly crossed the 200C barrier. You're invulnerable to all common ailments now. If there are any actual zinc molecules in the preparation you're spraying in the area of your lungs, you may have a small case of metal fume fever, but I'd recommend you counter that with a dilute application of chromium or vanadium. Remember to use fewer than zero atoms to get the maximum effect though. ;) Franamax (talk) 23:28, 21 June 2009 (UTC)[reply]

Homeopathic can mean more than the diluted bit but I have a hard time finding any justification for labeling the zinc treatment as being homeopathic. I agree in this case it seems to be just be a synonym for "alternative medicine" in general. --98.217.14.211 (talk) 01:34, 21 June 2009 (UTC)[reply]

"we came to the conclusion that the term in used in the US for any complementary medicine. Firstly, is this true?" No, not as far as I know. It sounds like the term is being misused. I'm surprised that the packaging said this. Perhaps this is just marketing-speak? 'Alternative medicine' is the term we generally use in the US (I live in Chicagoland). A Quest For Knowledge (talk) 02:01, 21 June 2009 (UTC) TC)[reply]

Homeopathy does not refer to "alternative medicine" in general but instead has a more precise meaning. An extremely accessible explanation of the origins of homeopathy and the scientific consensus regarding homeopathy is presented here by James Randi. The term is however abused to refer to any complementary/alternative medicine. Whatever you do, do not use a zinc-based "cold remedy" without reading the recent FDA warning regarding Zicam. --71.58.103.112 (talk) 09:42, 21 June 2009 (UTC)[reply]

Be careful with that stuff. The FDA recently issued a warning that Zicam may destroy your sense of smell. Guettarda (talk) 14:05, 21 June 2009 (UTC)[reply]

Yes. To be clear, according to the FDA, the manufacturers of Zicam have on record complaints from several hundred people who discovered the hard way that Zicam can PERMENANTLY destroy your sense of smell. And since almost all of what most people imagine to be their sense of taste is actually their sense of smell - you can pretty much write off ever enjoying food again - all of the subtle flavors reduce to salty/sweet/sour/bitter/savory. I don't understand how Zicam can be classified as "homeopathic" and still have enough active ingredient to cause this - it seems to me that they must have been abusing the "loophole" that allows homeopathic drugs to get onto the market without adequate testing. The only reason that loophole exists in the first place is because true homeopathic "drugs" are nothing more than water...they are a horrible scam - but they shouldn't be dangerous. If they actually have measurable amounts of (for example) Zinc in them then they aren't homeopathic and they should be undergoing a full swath of clinical trials, etc, etc. If the law allows measurable amounts of active ingredients in homeopathic medicines then they become more than just a scam - you should read that word on the label and mentally translate it to "Completely untested - use at your own risk!" SteveBaker (talk) 14:29, 21 June 2009 (UTC)[reply]

I should clarify - I turned down the offered treatment. I know better than to trust anything with the work "homeopathic" on it, regardless of whether it is correctly used or not! This particular treatment was apparently intended to be sprayed on the back of the throat, rather than the nose, which should prevent it destroying your sense of smell. It also would seem to prevent it working if the claimed mechanism regarding mucus membranes in the nose (as described in the pages linked to above) is correct. --Tango (talk) 15:20, 21 June 2009 (UTC)[reply]

Mucous membranes. Mucus is a noun, mucous is an adjective. By the way you made the same mistake on phosphorus/phosphorous a few threads back (at least I think it was you). --Trovatore (talk) 22:24, 21 June 2009 (UTC)[reply]

I don't remember talking about phosphorus or phosphorous recently, but my spelling has never been ideal. I am far too reliant on spell checkers, so that kind of mistake is quite common for me! I will try and remember the distinction in future, thanks! --Tango (talk) 00:07, 22 June 2009 (UTC)[reply]

In US drug regulations "homeopathic" is a specific class of treatments based on homeopathic principles and accepted into the Homeopathic Pharmacopoeia. Inclusion generally requires that the remedy closely follows some traditional alternative medical practice with a long history of use. While they are regulated for safety, and for the kinds of claims they can make, most homeopathic "medicines" are not reviewed for their effectiveness. They are allowed to be sold alongside over-the-counter medications, which can often be confusing. Dragons flight (talk) 22:14, 21 June 2009 (UTC)[reply]

Above, "SteveBaker" said, "Zicam can PERMENANTLY destroy your sense of smell". <-- How did you reach this conclusion? "If they actually have measurable amounts of (for example) Zinc in them then they aren't homeopathic" <-- Is this part of the FDA's regulatory position? "Completely untested" <-- Strange, but the Wikipedia article Zicam cites at least one clinical study that tested the zinc nasal gel and the sales figures suggest that millions of people have used these products. --JWSchmidt (talk) 02:36, 22 June 2009 (UTC)[reply]

Well, me not being SB and all, but: "permanently destroy" may come from the same sources the NY Times used when they quoted the FDA director of compliance saying "This disabling loss..may be..permanent..." - would that do? [14] And of course, anyone actually reading the Zicam article can easily ascertain which compounds are claimed to be homeopathic, none of them are zinc, that's just a metal you likely shouldn't be spraying into your respiratory system. And I'd be interested in the peer-review and full text of the clinical study to which you refer (is it one which found damage to health, or the metastudy which suggested that further study is required to verify primary efficacy and doesn't mention side-effects in its abstract?[15]). Oh, and millions of people have used crack cocaine, crystal meth, alcohol, tobacco, asbestos and benzene too, what was your point there? Franamax (talk) 04:00, 22 June 2009 (UTC)[reply]

The Wikipedia anosmia article makes it clear that anosmia can be permanent. Infections such as the common cold can cause anosmia, so people who do not use Zicam get anosmia. Who do they sue? Where does the FDA say that Zicam causes anosmia? This is the published study I noticed in the reference list at Zicam. It is certainly wrong to suggest that when you see the word "homeopathy" on a package it means "completely untested". Franamax, I don't know what your point is in mentioning crack cocaine, crystal meth, alcohol, tobacco, asbestos and benzene. Part of the testing of drugs comes after they are introduced into the market and used by large numbers of people. Should we count the number of conventional drugs that have been withdrawn by the FDA only after they were given to millions of people? --JWSchmidt (talk) 14:30, 22 June 2009 (UTC)[reply]

June 21

Cockatoos: are they more likely than other birds to go crazy?

It seems as though 3/4 of the cockatoos I see in people's pet videos on Youtube have some sort of psychological problem, whether it's pulling out their own feathers, gnawing strips off of their own flesh or doing that 'rocking around and making repetative noises because I've gone insane' thing. I know that the same thing can happen to most species of parrot but it seems way more prevalent in cockatoos. Is there any particular (known) reason for this? --90.240.20.62 (talk) 00:02, 21 June 2009 (UTC)[reply]

There is an article on Feather-plucking but it lacks sources. Sifaka ^talk 00:23, 21 June 2009 (UTC)[reply]

Maybe just nobody videos "sane" birds to put onto YouTube? - KoolerStill (talk) 10:32, 21 June 2009 (UTC)[reply]

"Enamel strengthening" toothpaste

I see many ads for new toothpaste that proclaim new "enamel strengthening", re-mineralizing, enamel hardening, and other similar claims. Is it me, or is this just new marketing approaches to old fashioned flouride? Are there any new discoveries better than flouride? --70.167.58.6 (talk) 01:14, 21 June 2009 (UTC)[reply]

There are other compounds, more recent compounds for that matter, which have been proven to at least a small extent to either strengthen enamel or increase deposits of enamel on your teeth. An example is xylitol. Regards, --—Cyclonenim | Chat 23:21, 23 June 2009 (UTC)[reply]

"Waveguide" ultrasonic toothbrushes

Another product I see advertised as being new and different are "waveguide" ultrasonic toothbrushes. Aren't all ultrasonic toothbrushes waveguide -- with the waveguide being the brushing head? A non-waveguide ultrasonic toothbrush could not exist, could it? --70.167.58.6 (talk) 01:23, 21 June 2009 (UTC)[reply]

If it's anything like the one described in U.S. patent 7,296,318, then the waveguide is an extra blob of rubber stuck to the brushing head. This is meant to couple more energy into the liquid than you can do by relying on the bristles alone. --Heron (talk) 12:30, 21 June 2009 (UTC)[reply]

Interesting. It sounds like a marketing gimmick. At any rate, the company went out of business. [16] --70.167.58.6 (talk) 13:45, 22 June 2009 (UTC)[reply]

Range data for Lockheed Electra 10-E?

Hello everyone, sorry to bother y'all about Amelia's plane again, but I seem to be involved in a bit of a dispute about its maximum range (one other editor claims she had barely enough fuel to reach Howland Island, while I'm trying to prove that she had plenty to spare). So I've crunched the numbers a while ago and came up with the following: --Economical cruise speed of ~140 kts. at ~40% power; --Fuel flow rate of ~40 gal./hr. at this speed, giving a maximum range of ~3,850 miles with 1,100 gal. of fuel on board (I know she had exactly 1,100 gallons on board, as it is on the official record).

These figures are pretty close to the range of 3,600 miles that one other source gives, but I'm not sure if they're correct, because (1) I actually calculated the 40% power setting for the Lockheed Lodestar and applied it to the Lockheed L-10 Electra, and (2) I did all the calcs in my head, so I probably introduced quite a bit of rounding error too. So could someone be so kind as to double-check these figures to see if they're correct or not? Thanks!

76.21.37.87 (talk) 06:10, 21 June 2009 (UTC)[reply]

I have nothing to say about anything except the calculation: 140 knots X (1100 gallons / 40 gallons/hour) is 3,850 nautical miles. If you were implicitly assuming that "miles" would mean nautical miles in this context, fine. --Anon, 07:21 UTC, June 21, 2009.

Was there a headwind? Remember - your calculations relate to AIRspeed - not GROUNDspeed. There is a huge difference! Also, you use a lot of fuel during takeoff - much more than at cruising speed - particularly if the aircraft is overloaded. Weight is everything here! You also use a lot more fuel if you are changing altitude a lot - eg to get above bad weather or to get low enough to navigate using maps. The amount of power (and hence the fuel consumption) required to maintain level altitude depends on the weight of the plane - so initially, the fuel economy at 140kts would have been much worse than your data suggests. This question (and the previous ones you asked) are extremely bothersome to me. The degree of oversimplification is very worrying. Her plane was not even a standard Electra - and it was not being flown within the manufacturer's original weight restrictions. She'd modified the heck out of the thing...there is no way to know what it's fuel efficiency was - you certainly can't use the data sheets for the standard plane. So IMHO, all bets are off. The answer is "We don't know"...and even..."We will never know". All answers that are other than that are wild-assed guesses and should be treated accordingly. Neither you - nor the person you are disputing with - can possibly have the slightest clue about what you're arguing about! Some mysteries are just mysteries. SteveBaker (talk) 14:15, 21 June 2009 (UTC)[reply]

Hey SteveBaker -- good point. Perhaps I should have made it more clear that all the range data that I either calculated myself or quoted from other sources are just ballpark estimates and no more than that. In case you're wondering, this has to do with that whole Gardner Island controversy, I was just trying to see if she would have had the range to reach the island. FWIW, I have tried to model the fuel consumption again, using exact numbers, taking account of the overload, and assuming a 25-knot headwind (which is a worst-case estimate), and got an estimated maximum range of ~2,900 nautical miles (once again, a worst-case estimate that assumes she did not adjust her cruising speed for the overload and the headwind, which she would certainly have done, being the experienced pilot that she was). So, based on these calculations (which, I want to make clear, are only a ballpark estimate), the answer to my original question would be "probably yes". Well, thanks for the info, and clear skies to you! 76.21.37.87 (talk) 04:15, 26 June 2009 (UTC)[reply]

Four towers around rocket gantry

What is the purpose of the four towers shown here: http://en.wikipedia.org/wiki/File:LRO-LCROSS_Atlas_V-Centaur_launching_from_Launch_Complex_41.jpg And do the wires that connect them have any non-structural purpose? 89.242.100.210 (talk) 09:29, 21 June 2009 (UTC)[reply]

As it says in the description on the image file, they are lightning towers built to reduce the risk of lightning strikes on the launch vehicle or associated equipment prior to launch. The wires are all part of the system, see this animation [17]. Mikenorton (talk) 10:25, 21 June 2009 (UTC)[reply]

should we scale down the internet?

Looking scientifically ....

1) Is there enough future energy to power the servers? [assuming no energy breakthrough]

2) Are we being unbelievably selfish to future generations by depleting energy on websites which are lets face it 99% pointless data?

3) Could a way to remedy this is have a vast archive (like the wayback machine) and delete old pages after a few years?

—Preceding unsigned comment added by 84.13.124.167 (talk • contribs) 11:42, 21 June 2009

Those are interesting questions, but I'm not going to attempt to answer them except to say that I suspect the Internet saves energy in terms of visits to libraries, bookshops, and video rental and other shops, as well as saving on postage and fax costs. Perhaps someone knows of a study into this aspect of the Internet.--Shantavira|^{feed me} 12:11, 21 June 2009 (UTC)[reply]

Yes, I agree. The Internet uses a really tiny amount of energy compared to all other human activities - and it certainly saves energy in many ways. Sure - it's possible that in future we'll have insufficient energy to power the thing - but I rather doubt that. Computers don't need much power - and it would be perfectly possible to power the servers using solar panels - particularly because solar panels are getting more efficient and computers are needing less and less power as time goes by. The problems for humanity are in things like cars, trucks, planes and ships which (being mobile) can't take advantage of things like solar power and wind energy - and for large scale industrial activities that need so much power that the amount of area they'd need to be powered from renewable sources becomes a huge issue. But the Internet is far, FAR down the list of things that are problematic.

Another thing - the amount of data on a server has little or nothing to do with the energy it takes to run it. Data exists as little magnetic zones on a hard drive. If you power down the hard drive when nobody is accessing it - you can have as much data on the server as you want and it costs zero energy to maintain it. The only cost is when somebody ACCESSES that data and the drive has to spin up to speed, copy the data into main memory and ship it off down the wires. So the fact that 99% of it is "pointless" is not relevent. If you need something to complain about - it should be the number of people who are accessing that "pointless" stuff. However, most of us would argue that if someone feels the need to access it, it's probably not pointless at all.

Deleting pages is actually a wasteful activity because you have to power up the hard drive to do it - and that takes energy. (I should explain a small caveat here: It does take energy to manufacture a hard drive - so I guess there is an initial cost to storing "pointless" data - but very, very few websites need more than one hard drive to store everything - so the cost is the same whether the drive is empty or full.) SteveBaker (talk) 14:03, 21 June 2009 (UTC)[reply]

Also, even if the wasted enery came anywhere near that of, for example, cars - i think many people would already prefer to lose the car than the internet. Pointless car journeys (or 5-7 people-carrying cars with only one occupant) far out-number those we need, so eliminating those would be a higher priority in an energy shortage. Why target the internet, but not older industries?YobMod 14:13, 21 June 2009 (UTC)[reply]

The free market is capable of working these things out. We would leave fossil fuels in the ground if there weren't better investments, so we're safe in saying that we're not being selfish by using too much energy (though we may be selfish in having too high a prevailing interest rate). As for if we should scale down the internet, the cost of power is part of the maintenance costs. The higher the costs, the fewer webpages will be made. The whole "scaling down the internet" will happen continuously. — DanielLC 17:21, 21 June 2009 (UTC)[reply]

"The free market" only works properly if all costs are internalized. See tragedy of the commons. --Stephan Schulz (talk) 00:08, 22 June 2009 (UTC)[reply]

They are. There's no way to get energy that doesn't involve owning whatever you're getting the energy from. Or are you referring to environmental costs? — DanielLC 15:07, 22 June 2009 (UTC)[reply]

Environmental cost, of course, and political cost - arguably the price of oil is kept artificially kept low by political pressuring and operations like the war in Iraq. For a long time coal-mining has received massive subsidies in Germany (and I'd bet other places). Nuclear power has received not only massive research funding, but so far is not paying market price for safe waste disposal and insurance against possible environmental risks. --Stephan Schulz (talk) 15:14, 22 June 2009 (UTC)[reply]

NOTHING

I was just having a discussion with a friend about NOTHING - meaning try to explain nothing in refrence to the univers is expanding into nothing; the idea you can go to the end of the univers and then it stops but whats on the other side. Is there just a quantum theory for this or a mathamaticle one? or is there anybody that could offer a no nonsense explanation for Nothing...a bit about face the question but i am sure you will get my meaningChromagnum (talk) 12:56, 21 June 2009 (UTC)[reply]

The word "universe" means "everything". If it had an "edge" and there was something on the other side - then the something on the other side would just be a part of the universe and the "edge" would be some unusual feature running through the universe - not the end of it. But I think you misunderstand how the expansion of the universe works. Space itself is expanding. It's not like there is a bunch of solid objects moving outwards into otherwise empty space...it is the space itself that's growing. Either space is (and always was) infinite - or it curves back around on itself in some fourth spatial dimension - or a couple of other variations on that. But there isn't going to be an "edge". It's best to think of the two-dimensional rubber sheet analogy. Imagine 2D beings living in 2D space...for them, there is no third dimension. Their universe could be a super-stretchy rubber sheet with a grid of lines drawn on it. If space is infinite - then they live on an infinitely large flat sheet...but even though it's already infinite - it's still stretching outwards. If you watch closely, the grid lines around your position on the grid are gradually getting further and further apart. Off in the far distance - the grid lines are moving away from you really quickly - but nearby, the movement is so slow, you can hardly see it happening. That's a valid 2D analogy for what we're seeing happening in 3D. However, there is another possibility. These 2D beings might be living on the surface of a 3D balloon that's slowly being inflated. They can walk around on the surface of the balloon - and the grid-lines on the surface of the balloon will gradually be moving apart - but their universe is still 2D. It has no edge - and it's expanding. In theory, they could travel off in one direction around the balloon in what seems like (for them) a dead straight line - and they'd arrive back at the starting point. However, because the balloon is expanding faster than the speed of light - they could never actually do that in practice - so the universe is larger than they'll ever be able to see.

But in neither case did their rubber sheet universe have an "edge"...and neither does ours. So there is no "nothing" out there that the universe is expanding "into"...space itself is stretching. It's a hard thing to get your head around...but that's how it is. SteveBaker (talk) 13:52, 21 June 2009 (UTC)[reply]

I think it is simpler to say we don't understand. If we can't get our heads around something perhaps we should admit that we are stymied by a question. I accept neither that the universe is finite or infinite. I don't understand. That is simpler to say. And I think the same is true of time. I cannot contemplate how time can be infinite, and I cannot contemplate how time can be finite. I'm not trying to stall debate and questioning and contemplation of possibilities. For myself though, I just want to say that I find this unanswerable at this time. Bus stop (talk) 14:21, 21 June 2009 (UTC)[reply]

Steve isn't saying he knows the answer, he is just reporting very well-known conjectures that appear in journals. The Flatland comparison is in some UK A-level curriculum - there is no need to deny these theories exist, all becasue we cannot know their validity.Yob Mod 14:33, 21 June 2009 (UTC)[reply]

I don't think it's a good idea to talk about the universe being curved in a "fourth spacial dimension". While things like String Theory and Kaluza-Klein theory posit extra spacial dimensions, that is very different to General Relativity's description of the universe as curved. In mathematics there are two distinct concepts of curvature - extrinsic curvature which describes how a space is embedded in a higher dimensional space, and intrinsic curvature which describes how the space is curved from the point of view of the space itself (eg. what the angles in a triangle in that space add up to). When we talk about the universe being curved we mean the latter, there is no need to consider it being embedded in a higher dimensional space. --Tango (talk) 15:05, 21 June 2009 (UTC)[reply]

I'm not denying that any theories exist. I didn't think I was denying anything. On the contrary I am affirming something. I am affirming my own ignorance. I am asserting my inability to cope with such a question as to whether space and/or time is infinite and/or finite. I personally find the questions unanswerable, and even un-addressable. But I don't mean to prevent or discourage others from addressing such questions. Bus stop (talk) 15:04, 21 June 2009 (UTC)[reply]

So why the heck are you posting? If there is a question who's answer you don't know or don't understand, the best strategy is to sit quietly in a corner and read the answers. It's pointless to post your own failure to understand. It may be simpler to say "we don't understand" - but we can do much better than that. SteveBaker (talk) 21:03, 21 June 2009 (UTC)[reply]

To some extent, it is not exactly correct to call these questions "unanswerable". There are observable consequences to many of the hypotheses about the universe and its shape and curvature. You can read a bit about them here. The effect of having a closed universe, as opposed to an open universe, shows up in many advanced cosmological observations. The math is very hard and I don't pretend to follow all of it, but simply put, there are falsifiable consequences to any hypothesis we make about the nature of the universe. It may show up as a doppler shift on the cosmic microwave background, or a certain flavor of gravitational lensing, or some other subtle effect. This is the point of modern cosmology. It's insufficient just to "think about the unanswerable" - cosmologically inclined physicists must mathematically demonstrate an observable consequence of some theory; or, observe some evidence of somebody else's theory. This is what separates cosmology physics from "wild speculation" or "philosophy." Nimur (talk) 15:11, 21 June 2009 (UTC)[reply]

You said "we" not "I". While you may not have the training necessary to truly comprehend these matters there are experts that do. --Tango (talk) 15:16, 21 June 2009 (UTC)[reply]

Granted, I said "we," not "I." But I have an expectation of an explanation that I can grasp, on some level, and that has not been forthcoming. It may be a function of the seeming simplicity of the question posed that makes me think someone ought to be able to explain it to an untrained person such as myself. Bus stop (talk) 15:37, 21 June 2009 (UTC)[reply]

I think Steve's answer is pretty understandable to the layman. Perhaps you could explain what it is about it you don't understand? --Tango (talk) 15:46, 21 June 2009 (UTC)[reply]

It is a non-answering of the question. It is the diverting of a question concerning 3 dimensionality into a 2 dimensional realm. Two-dimensionality is an abstract construct. Three-dimensionality applies best to our understanding of the world, and it is what the original question inquires about. I have to admit, I don't even understand the explanation posed. I only accept analogies so far. And then I want further explanations. The so-called 2 dimensional beings are inconceivable. And even the comparison to a rubber sheet is merely conceptual, because such a rubber sheet would have thickness. I find the question to persist, at the end of the explanation. I still find myself asking if a 3 dimensional universe is finite or infinite. I don't think analogies to 2 dimensionality are answers to problems concerning 3 dimensionality. And again, the same problem, as I see it, applies to time. Is time infinite, or is time finite? I am not trained in these things. I will not rule out that answers are known, concerning these questions, by those more knowledgeable than myself. But I have not seen any that seem realistic. That is all I'm saying. I know I'm repeating myself. Sorry. Bus stop (talk) 16:44, 21 June 2009 (UTC)[reply]

It's not a non-answering. It's a means to try to explain a tricky concept by analogy. I don't, personally, have a problem imagining the 3D version of an infinite of a finite-but-wrapped-around universe. But you are kinda stuck with the word "universe" meaning "absolutely everything" - so if there is an "edge" and something "beyond the edge" then it's a part of the universe by definition. If you want to talk about something smaller than everything (like a galaxy or a galactic cluster) then we can - but if we're talking about "everything" then you can't go around asking "what's beyond the edge of everything" - because whatever that is would be a part of everything. Hence, if we are discussing "the shape of absolutely everything" - we have to start to accept infinities and wrapping-around-ness. SteveBaker (talk) 21:03, 21 June 2009 (UTC)[reply]

So, you are saying the universe is infinite? And you are saying that we have different understandings of what infinite means? And that "wrapping-around-ness" is an aspect of your understanding of an infinite universe? Bus stop (talk) 22:01, 21 June 2009 (UTC)[reply]

I'm pretty sure that was a typo on Steve's part - he means "infinite or a finite-but-wrapped-around universe". As far as I'm aware, modern science hasn't been able to determine which of those options is the correct one (I think we have some lower bounds on the size of the universe, but that's all). --Tango (talk) 22:05, 21 June 2009 (UTC)[reply]

What is the scientific definition of "nothing" and in what form can it or has it been found? ~ R.T.G 15:25, 21 June 2009 (UTC)[reply]

I don't think there is one. There is vacuum, if that is any help. --Tango (talk) 15:46, 21 June 2009 (UTC)[reply]

The problem is that a vacuum is proving to be anything but nothing - quantum foam and virtual particles and the concept of false vacuum. There are a lot of interesting things going on in this supposed nothingness. Also, even if vacuum somehow fitted your definition of nothingness - there is no such thing as a sizeable volume of hard vacuum - even in deep intergalactic space - there are measurable number of hydrogen and helium atoms. Worst still, even the hardest of hard vacuums still has photons and neutrinos and all manner of other exotic things flying through it - so do describe it as "nothing" is a tough sell. SteveBaker (talk) 21:03, 21 June 2009 (UTC)[reply]

(Intrinsic curvature has not yet been written.) ~ R.T.G 15:26, 21 June 2009 (UTC)[reply]

Try Curvature of Riemannian manifolds, then. It's rather technical, though. --Tango (talk) 15:46, 21 June 2009 (UTC)[reply]

To agree with you, Tango, I quote : "In mathematics, specifically differential geometry, the infinitesimal geometry of Riemannian manifolds with dimension at least 3 is too complicated..." :o~ R.T.G 15:49, 21 June 2009 (UTC)[reply]

RTG - please stop answering questions...you have no clue about the things you're talking about. Quoting that half-sentence out of context is EXCEEDINGLY misleading. SteveBaker (talk) 22:23, 21 June 2009 (UTC)[reply]

You can easily get into trouble talking about "nothing", as in the old syllogism "Nothing is better than eternal happiness; a ham sandwich is better than nothing; therefore a ham sandwich is better than eternal happiness." When you say the universe is "expanding into nothing", you may be making a similar error, treating "nothing" as a concept on the same footing as "empty space" or "green cheese". That will get you into trouble. If space does end, then it just means there's no more space beyond that point. If you ask what's beyond that point, you're implicitly imagining that there's space beyond that point that something could be in. What would happen at the edge? Well, there would be a set of two-dimensional physical laws governing the boundary. It's impossible to know what those laws would be without a better understanding of space than physicists have now, although we have some ideas from studying two-dimensional quantum systems theoretically and in the lab. (This turns out to be a surprisingly deep and interesting subject. Topological quantum computers are one example of new physics that exists only in two dimensions.) Or maybe the edge would be like a black hole event horizon, in which case you wouldn't necessarily need a separate set of laws. Either way, you have physics in space (called the "bulk"), and physics on the boundary, and that's all.

That said, the universe that we see could be expanding into a preexisting vacuum or preexisting cheese. Neither hypothesis seems very likely to me, but they are mathematical possibilities and they're consistent with what we observe. We simply don't know what's out there beyond the limited distance that we can see. -- BenRG (talk) 21:06, 21 June 2009 (UTC)[reply]

Gents/Ladies thank you very much for the answers given, a difficult concept for me to understand; however i think i now have a better understandingChromagnum (talk) 05:25, 25 June 2009 (UTC)[reply]

The non-entity "nothing" is incapable of having, doing or being anything. Semantically the questions What has nothing, What does nothing and What is nothing are all ill-posed questions that defeat proper answers. However to a Zen buddhist "What is nothing" is a productive Kōan question. The problem posed by a koan is to be taken quite seriously, and to be approached as literally a matter of life and death. The student will realize that even in the vacuum of space the answer is not to be found physically because there is no volume anywhere where intermolecular forces are absent. Even if they could be eliminated forces of attraction remain, and the strongest attractive force is the student's own spiritual clinging desire and repulsion. When the student gains the insight that the Kōan can only be answered after letting go of all clinging, the Zen teacher can observe that "the place and the time and the event where truth reveals itself"^[2] is near. Cuddlyable3 (talk) 23:42, 6 July 2011 (UTC)[reply]

Pakistan

Does that country of pakistan have any indigeneous missile technology ???I heard it has stacked up the missiles thrown away by N.Korea and China!!! —Preceding unsigned comment added by 121.246.174.130 (talk) 14:48, 21 June 2009 (UTC)[reply]

Are you talking about nuclear missiles or missiles in general? Pakistan has had superior weapons technology to N. Korea for some time, I believe, so I doubt they are using N. Korean weapons. It is possible they have bough Chinese weapons, though. --Tango (talk) 14:58, 21 June 2009 (UTC)[reply]

This 1999 Unclassified CIA Report discusses Pakistan in particular. According to this report, Pakistan has a well-developed internal nuclear program but their missile infrastructure seems to be largely imported from China and North Korea. Specifically, the CIA claims that the North Korean Rodong-1 inspired (or is) the Pakistani Ghauri_(missile). From a cursory survey, it would seem that missile technology is imported while warhead technology is indigenous to Pakistan. Nimur (talk) 15:17, 21 June 2009 (UTC)[reply]

By the time of this 2003 report, Pakistan is no longer considered "developing" a program, and is classified as having a "well-established" program. Nimur (talk) 15:20, 21 June 2009 (UTC)[reply]

Well what about the war head technology???Is it superior to it's neighbour India??? —Preceding unsigned comment added by 121.246.174.130 (talk) 17:44, 21 June 2009 (UTC)[reply]

It's unclear, but the fact that they have been cooperating with the Chinese on their warhead development suggests that they possibly could be (as China is far more advanced from a nuclear standpoint than India). --98.217.14.211 (talk) 16:29, 22 June 2009 (UTC)[reply]

One notices that the anonymous OP refers asymetrically to "that country of pakistan" (not capitalised) and India (properly capitalised). Does the hearsay that N.Korea and China throw away missiles for another country to collect come from a credible source, perhaps overheard in a Calcutta bar ? Cuddlyable3 (talk) 19:20, 22 June 2009 (UTC)[reply]

Seems to be from Mumbai. NotAHen (talk) 22:41, 22 June 2009 (UTC)[reply]

With a wide range of interests. NotAHen (talk) 22:43, 22 June 2009 (UTC)[reply]

You can, of course, deliver nuclear weapons via aircraft - and Pakistan has 700 aircraft in their fleet. Against an enemy with really modern anti-aircraft defences, that's not much use - but when you consider who it is that Pakistan wishes to impress with their nuclear arsenal - that may not be an issue. SteveBaker (talk) 03:37, 23 June 2009 (UTC)[reply]

Race and brain size/characteristics.

This might be a bit controversial, but here it goes. I'm looking for information regarding correlations, or lack thereof, between race and brain size/characteristics. For example, do blacks have smaller brains than whites? If true, would that affect their intelligence? Is it true that the brains of whites and blacks are "wired" differently? Links such as this one would be helpful too. Thanks in advance, ― Ann _{( user | talk )} 15:25, 21 June 2009 (UTC)[reply]

File:Ele-brain.png

Human, dolphin and elephant brains up to scale

As a start, why don't you read about Intelligence and brain structure in normal individuals, and then you can develop a baseline for comparison? This is a really complicated issue, and it sounds like you want to boil it down to an "IQ vs. mass" plot, or a "race vs. brain size." This is too simplistic and will not possibly capture any meaningful scientific conclusion. Brain structure is very vaguely correlated to mental acuity. Race and ethnicity is only vaguely correlated to brain structure, if at all. Different definitions of "race" will skewer any sort of meaningful comparison studies. Nimur (talk) 15:48, 21 June 2009 (UTC)[reply]

See Race and intelligence. WP:WHAAOE! --Tango (talk) 15:56, 21 June 2009 (UTC)[reply]

We also have several other articles relating to this topic, including Neuroscience and intelligence, Brain size and intelligence, and Heritability of IQ. Before plunging too deeply into this topic, though, here is a question you should think about: suppose when you look up the data you find that black people have larger brains than white people. What conclusion would you draw? Looie496 (talk) 18:13, 21 June 2009 (UTC)[reply]

That you've got the "wrong answer" so your methodology must be flawed, of course! --Tango (talk) 18:26, 21 June 2009 (UTC)[reply]

...What to speak of elephants and dolphins.--Shantavira|^{feed me} 07:21, 22 June 2009 (UTC)[reply]

Though to be more clear nobody actually asserts it is just large size but large brain size relative to overall body mass. So elephants do better than some animals but are not nearly in league with humans. --98.217.14.211 (talk) 16:27, 22 June 2009 (UTC)[reply]

The conclusions that the OP seeks are much more than "a bit" controversial. Measuring comparative intelligence is fraught with controversies, such as what different IQ test results really mean, and whether it is even defensible to postulate black and white as different human races. It seems everyone has a vested interest here, for example I don't think I am alone in viewing favourably the idea that I belong to an excellent race with impressive intelligence. The OP must expect accusations of bias connected with any answers to the questions asked, that can be defended only by very conservative labelling of whatever evidence exists. Cuddlyable3 (talk) 19:08, 22 June 2009 (UTC)[reply]

Brain size/exercise

Can anyone correlate brain size to exercise? Bruce Lee (see Bruce_lee#Death) died of a swollen brain which various doctors said was caused by either trace amounts of cannabis or normal painkillers but the urban legend is that he trained so hard his brain swelled inside his head (the painkillers and cannabis were both disputed as causes of death). ~ R.T.G 16:05, 21 June 2009 (UTC)[reply]

Brain size is primarily determined by skull size, I think. What you want to look for is a correlation between intracranial pressure and exercise. --Tango (talk) 16:24, 21 June 2009 (UTC)[reply]

It's hard to do the experiments properly, damn ethics committees, if some people need to be sacrificed it would be for the greater good ;-) From Dance and health "A study in New York in 2003 has shown that cognitive activities like crosswords help ward off dementia but, except for ballroom dancing, most physical activities do not". It seems you need to use your brain to exercise it, raising weights in the gym won't make you any smarter. Dmcq (talk) 16:38, 21 June 2009 (UTC)[reply]

I had heard that physical exercise did increase your IQ, by increasing the blood flow through your brain. My non-scientific personal experience supports that idea. 78.146.242.171 (talk) 12:58, 22 June 2009 (UTC)[reply]

To my knowledge, there is no correlation between brain size and intelligence, so whether or not it makes you smarter doesn't answer the question. — DanielLC 17:09, 21 June 2009 (UTC)[reply]

I expect there is a correlation within humans between adult brain size and intelligence, if you do not exclude persons with Microcephaly. Also in animals and humans, other genetic causes or trauma can cause stunted brain size with diminished mental ability. Additionally, with extreme age or with many diseases or conditions, the brain often shrinks and mental ability decreases. Also across primate species, there is likely a correlation between brain size and intelligence [18]. "Encephalization" normalizes brain size compared to body size, and thus primates have about twice the relative brain size as other mammals [19]. Sternberg says the brain size, after adjusting for body size, is a measure of information processing ability and thus a measure of intelligence. Scholars debate how to normalize brain size versus body size to make a fair comparison. The relative brain size of higher primates, our ancestors as well as dead end higher primates, have shown higher encephalization over the past several million years [20] page 769. Only if you restrict the range to "normal adult humans" will the correlation disappear, as is usually the case when only the center part of an x-y distribution is used in a correlation calculation. Some research indicates that mental activity can decrease the loss of cognitive ability with age. So it is probably true that whatever "intelligence" is, it does not correlate with absolute brain size in normal humans. As for exercise affecting the structure of the brain, many animal studies have shown that experience and environmental richness affects the brain structure in terms of microscopic structure complexity, as well as cortical size [21] page 47. Edison (talk) 17:35, 21 June 2009 (UTC)[reply]

A "swollen brain" such as supposedly killed Bruce Lee is not caused by growth of the brain, but by a build-up of fluids as a result of damage. It happens for the same reason your skin or muscles swell when you get a bruise. There is some evidence that exercise or other types of experience can affect brain structure, making certain parts of the brain slightly larger, but that wouldn't come into play here. We have an article, brain fitness, that deals with some of these factors, but unfortunately it isn't a very good article at the moment. Looie496 (talk) 18:04, 21 June 2009 (UTC)[reply]

It's a bit unfair because Bruce Lees life was given to philosophy and to suggest that he stretched his physique more than his mind is unfair at least. Could you fault a man if he stretched that muscle? Well its fair due to say that. ~ R.T.G 12:47, 22 June 2009 (UTC)[reply]

Low doses of radiation protecting against cancer?

I have read people saying that low doses of radiation provides a measure of protection against cancer. Is that the case? Unomi (talk) 17:40, 21 June 2009 (UTC)[reply]

See radiation hormesis. -- BenRG (talk) 17:50, 21 June 2009 (UTC)[reply]

We do not give medical advice. But taking the question as just a request for referenced information, a recent publication from the National Research Council (US) says (p 89[22]) that "low dose radiation acts primarily as a tumor-initiating agent." It says there is no expectation of a low dose threshold below which it does not initiate tumors. On page 10 they conclude that there is a linear relationship between radiation dose and cancer risk down to the lowest doses, with no threshold below which the added risk is zero. Edison (talk) 17:59, 21 June 2009 (UTC)[reply]

Thank you, it was not meant as soliciting medical advice, merely a query regarding a statement here: http://news.bbc.co.uk/2/hi/health/3554422.stm that I found 'curious'. I found http://www.radscihealth.org/rsh/Papers/FrenchAcadsFinal07_04_05.pdf to be pretty interesting reading regarding their opinion on low levels of radiation. Unomi (talk) 20:10, 21 June 2009 (UTC)[reply]

I think that that paper quoted by Edison doesn't really reflect the best understanding about the action of low radiation doses. This[23] paper, for instance, shows a different point of view. Figure 3 suggests that doses as high as 10000 mGy/year may be considered be considered beneficial. Dauto (talk) 21:47, 21 June 2009 (UTC)[reply]

I strongly disagree. The paper is recent and authoritative. "Radiation in low doses is good for you" sounds like rank bullshit. 02:37, 23 June 2009 (UTC)Edison (talk)

I tend to agree with the paper that Dauto linked. The Linear-No-Threshold model seems almost unscientific; I'm not sure if I believe in a benefit of low-doses, but extrapolation of risk by linear model to low-dose seems sloppy in the absence of strong data. Nimur (talk) 23:14, 21 June 2009 (UTC)[reply]

It reads as though the posited mechanism of hormesis is by causing enough damage to encourage apoptosis and/or stimulating DNA self repair mechanisms? Also, for general purposes is 1 sievert equivalent to 1 gray for EM radiation ?

no, a sivert is not a unit of EM radiation... its a unit of biological damange... 1 sv = 1 J/kg = 100 Rem... 1 Gray = 100 Rads... a dosage in rems = dosage in rads * QF... the QF depends on the type of radiation (Gamma, Beta, Alpha)... for gamma QF = 1, but alpha has a higher linear energy transfer and QF = 20... 70.71.22.45 (talk) 00:54, 22 June 2009 (UTC)[reply]

Ok, but from Sievert it says (as far as I can tell) Sv * Q * N = gray and that a 'human' has an N of 1 and that EMR has a Q of 1, is that a correct interpretation? Unomi (talk) 01:35, 22 June 2009 (UTC)[reply]

There are huge differences between saying "low level radiation is tolerable", "low level radiation may be good for you" AND ""Low levels of radiation are probably essential for life itself." The BBC reports Professor Zbigniew Jaworowski stating the latter. Without evidence that sounds like the unscientific adage "The blow that doesn't break my back makes it stronger." I suspect the BBC may have misunderstood the professor if he actually meant that some level of radiation was historically essential to the evolution of life. Cuddlyable3 (talk) 18:18, 22 June 2009 (UTC)[reply]

It's apparently the same Zbigniew Jaworowski as this one, with whom I am somewhat familiar. Given his past pronouncements on various topics it wouldn't be at all surprising if he really did say "radiation is good for you." Short Brigade Harvester Boris (talk) 00:24, 23 June 2009 (UTC)[reply]

Phone sound

Why is sound quality from phone speakers so poor compared to anything else I've ever heard? Vimescarrot (talk) 19:05, 21 June 2009 (UTC)[reply]

Probably for several reasons. First, they are commodity devices and are designed to reduce cost before all other requirements. Next, the telephone system (whether it is POTS or a modern digital wireless system) does not even use high fidelity signal - it is usually found that about 1.5kHz to 3 kHz is sufficient to understand voice and conversations with minimal distortion. So, because the sound played over the speaker is rarely "hi-fi", there is no reason to use a hi-fi speaker. The form-factor of a telephone makes it difficult to have a nice resonant cavity, so the result is a poor signal, poor transducer, and poor acoustic properties - cumulatively, a less than top-notch audio quality. Nimur (talk) 20:02, 21 June 2009 (UTC)[reply]

And the reason none of these systems is improved is because of cost? Vimescarrot (talk) 20:12, 21 June 2009 (UTC)[reply]

Yeah, pretty much. However, that's a fairly trivial conclusion. Most anything could be further improved if you were willing to spend more for it. — Lomn 20:26, 21 June 2009 (UTC)[reply]

Most people who are using their phones as music players are using headphones - it would be hard to justify the size/power/cost of a decent speaker in a phone. SteveBaker (talk) 20:38, 21 June 2009 (UTC)[reply]

Just in case you were thinking otherwise, I was specifically thinking of conversation, not music. Vimescarrot (talk) 21:05, 21 June 2009 (UTC)[reply]

Well, as others have pointed out, speech is quite comprehensible with just a few kHz of bandwidth. Providing better speakers would help very little because the data simply isn't there. The higher frequencies are chopped off by the microphone - then by any line filtering, then again by the telephone exchange...voice transmitted via phone would sound pretty much like it does even if you had really high quality reproduction. SteveBaker (talk) 22:06, 21 June 2009 (UTC)[reply]

Because the frequency range is limited I sometimes find it hard to understand people with accent I am not used to, but understand them much better on VOIP (e.g. Skype). My guess is that VOIP supports a wider range of frequencies. NotAHen (talk) 22:39, 22 June 2009 (UTC)[reply]

They could send the signal encoded in MP3 and fit a relatively power-hungry speaker but the batteries wouldn't last very long. My own phone is roughly twice the size of most ordinary phones and yet, the one I had ten years ago was roughly 3 times the size again but the battery size is only about one quarter or less even though it lasts much longer. The Sony Walkman is probably the first well known example of the miniaturisation craze but certainly, your computer is as powerful as one that would have filled a whole building half a century ago. ~ R.T.G 13:01, 22 June 2009 (UTC)[reply]

Landlines wouldn't have to worry about power consumption so much, would they? Vimescarrot (talk) 13:16, 22 June 2009 (UTC)[reply]

Sure they would. Imagine a million phone calls per day on a companys lines. Power would be one of the main factors in cost and as folks are saying, even a top class speaker system (which you can hook up to your phone) would only recieve a certain quality of signal. (you could hook up as decent a signal as you like over the internet if that is what you are looking for) ~ R.T.G 13:38, 22 June 2009 (UTC)[reply]

No - I used to design telephone exchanges - the land lines don't consume much power. The reason relates to bandwidth - and compatability with a trillion phones out there. You can't use MP3 encoding because it's a compressed format - you'd end up with a second or more of latency between speaker and listener. The computer inside a cellphone is considerably more powerful than even the largest computer from 1959. The IBM 7080, for example - released in 1960 - only had 160kbytes of RAM. SteveBaker (talk) 16:52, 22 June 2009 (UTC)[reply]

The primary goal of telephone design is intelligibility. Good intelligibility is obtained by restricting the sound bandwidth to, say, 300 - 3200 Hz. However minimal distortion is not necessarily a goal. It is common in avionic and amateur radio communication to limit (clip) the voice waveform. This is a deliberate distortion that actually improves voice intelligibility especially over background noise. It is also a crude way of reducing the dynamic range of the voice signal amplitude that varies with different speakers and mouth-to-microphone distances.

Modern mobile telephones use a variety of voice digitising methods, such as the CELP coding used in GSM networks, that provide data compression while introducing acceptably small delay for natural conversation. MP3 encoding is popular for music i.e. wide bandwidth sound at relatively high data rate; however it uses a masking algorithm that gives poor results for voice bandwith at low data rate, as well as the long latency that SteveBaker mentioned. Cuddlyable3 (talk) 17:56, 22 June 2009 (UTC)[reply]

And finally; is sound quality for conversations in phones likely to improve in the future? Vimescarrot (talk) 18:03, 22 June 2009 (UTC)[reply]

The technology to improve telephone conversation sound fidelity could be used tomorrow but there is little motivation to make that happen. Most telephony is mobile these days. Mobile networks represent large investments in particular data- and sound bandwidths and codecs while the telephones themselves are overweighted with the features that users are willing to pay for. Examples of these features are music storage, inbuilt camera, GPS, SMS, handheld computing, e-mail, Internet access... But hi-fi voice is not on the investment horizon. Cuddlyable3 (talk) 18:31, 22 June 2009 (UTC)[reply]

I think widespread VOIP could solve the hardware problem of telephone lines restricting bandwidth. There could be HiFi VOIP, yes? Multichannel, high-fidelity telephone calls. --Navstar (talk) 00:49, 23 June 2009 (UTC)[reply]

Speaking of "land" lines, for over 50 years, long distance phone conversations have been sent in a multiplexed way via coax cable or microwave link. The narrower the bandwidth, the more conversations the communication channel can carry at the same time. A narrow bandwidth is adequate for normal conversation. The same is true , I would expect, for cell phones. When a higher fidelity channel is desired, more bandwidth can be purchased, as for a link between a radio station remote and the transmitter. Even back in the 1920's and 1930's phone company engineers could provide audio channels with much higher fidelity (wider bandwidth and more even frequency response) than normal voice communications required. Edison (talk) 02:34, 23 June 2009 (UTC)[reply]

Thanks very much, guys. Best answer(s) yet, keep up the good work. <3 Vimescarrot (talk) 10:00, 23 June 2009 (UTC)[reply]

A bit late, but of course there already exist high quality telephone links - ISDN - broadcasters, for example, use (or used) ISDN links between studios. --Polysylabic Pseudonym (talk) 03:01, 25 June 2009 (UTC)[reply]

Bacteria-based stain remover

This product and others like it say that they use "nonpathogenic bacteria" and "natural enzymes" to destroy stains and odors. I notice the ingredients list also includes isopropyl alcohol, though, which I'd think would kill all the bacteria. Does anyone know how this solution works? What bacteria are being used to magically destroy the sources of the bad odors? Tempshill (talk) 20:25, 21 June 2009 (UTC)[reply]

It probably works the same way as any biological detergent does. Detergents contain enzymes, not live cultures. However, there are bacteria that help remove odors, too. A freshwater aquarium nitrogen cycle is a good example. --Dr Dima (talk) 21:27, 21 June 2009 (UTC)[reply]

Oh, and regarding your question on isopropyl alcohol, it really depends on concentration and on duration of contact which bacteria are killed and which survive. --Dr Dima (talk) 21:33, 21 June 2009 (UTC)[reply]

June 22

Binary stars orbiting a planet

Would it be theoretically possible for a pair of binary stars to orbit a planet that sat between them? For that planet to be Earth-like? Neon Merlin 01:25, 22 June 2009 (UTC)[reply]

I don't think that would be stable. If the planet moved slightly towards one star it would accelerate towards it. There are several known stable solutions to the three-body problem, but I don't think that is one of them. It's very similar to L1, which isn't a stable equilibrium point. (It may be exactly like L1, I can't remember what the requirements for ratios of masses are...) --Tango (talk) 01:55, 22 June 2009 (UTC)[reply]

Something very close to what is being asked is possible. Although the L₁ Lagrangian point is nominally unstable, it’s possible to find stable periodic orbits around these points (called "halo" orbits), in the restricted three-body problem. Also, although the L₄ and L₅ Lagrangian points aren’t between the two stars, they are stable if the ratio of masses of the two stars is at least about 25, and would be reasonable good places for a planet to hang out without large variations in gravity or light. Red Act (talk) 02:12, 22 June 2009 (UTC)[reply]

According to [24], the answer is "sometimes" (specifically, 40% to 50% of observed binary systems). For the case of α Centauri, according to [25], the answer is yes. Someone42 (talk) 04:33, 22 June 2009 (UTC)[reply]

I don't believe that's the question being asked. Your links are about forming planets around one member of a binary pair. I believe the original question is whether a planet can exist at a stable point created by the combined gravity of both stars. Dragons flight (talk) 07:52, 22 June 2009 (UTC)[reply]

With a binary pair of stars - there must be stable lagrange points at which a planet could exist...in theory, it's a three body problem - and therefore, unstable - but providing the planet has negligable size compared to the stars, it's OK. But that's not quite what's being asked because the planet isn't "between" the two stars - it would be off to one side - and the stars aren't orbitting the planet. But given the right setup, I think the planet could possibly be somewhat earthlike. SteveBaker (talk) 15:21, 22 June 2009 (UTC)[reply]

If there is a big difference between the size of the stars (Red Act says above that the required ratio is at least 1:25, which rings a bell), then you could have the planet at L4 or L5 and there is no problem. If the stars are similar in size, which I think is what the OP is thinking of (although I may be wrong), then I'm not sure what stable solutions there are... I know of stable solutions for 3 similar sized bodies (there's a great one where they all follow a figure-of-eight), but not one for 2 similar sized large bodies and one small one. If there were a solution where the planet was just sat at the barycentre (which I think is what the OP is thinking of) then the planet could be Earth like, but it would be a little different due to constant daylight. If the planet rotated relative to the stars (which I actually suspect it wouldn't, I would expect it to be tidally locked) then you would get sunsets and sunrises, but there would be no night inbetween since when one sun sets the other rises. That would have some effect on the weather, but probably not anything that would completely rule out life as we know it. If it were tidally locked, then it is a little more difficult, but with the right kind of atmosphere the temperature variations wouldn't be too bad. --Tango (talk) 16:44, 22 June 2009 (UTC)[reply]

horsepower and cc

Is there any conversion factor between horsepower and cc of a motor car?? can these be relation in any such numerical figure?? or are these two different things?? —Preceding unsigned comment added by 119.153.21.132 (talk) 06:22, 22 June 2009 (UTC)[reply]

They are related, in that all other things being equal, a larger engine produces more power than a smaller one. However, many things are unequal, including bore, stroke, ignition, compression, fuel,... In general, modern engines with higher compression and direct injection get much more horsepower per volume of engine displacement than older, carburetor-based designs. --Stephan Schulz (talk) 06:53, 22 June 2009 (UTC)[reply]

There certainly isn't a direct conversion factor - there are too many clever ways of getting more HP from the same cc. To give you a concrete example: My wife's car (a MINI Cooper) has an identical engine (same cc's, same everything) as mine - but mine (A MINI Cooper'S) has a turbocharger, a free'er flowing exhaust system, and different settings on the engine management computer. I don't recall the exact numbers - but mine has about 50% more peak horsepower than hers. There is another version of the exact same car (the MINI One) that's sold only in Europe that's tuned for better fuel economy - it gets even less horsepower than my wife's car - and there are race-tuned versions that get 50% more horsepower than mine...so from the most extreme fuel-efficient version to the race-track version of the exact same car with the exact same engine - you get probably a 2:1 or maybe 3:1 difference in horsepower for the same number of cc's. SteveBaker (talk) 15:17, 22 June 2009 (UTC)[reply]

As Stephan and Steve said, there is no direct ratio of cc to hp. However, that doesn't stop people from measuring it. This guy, for example, has compiled an interesting table. It shows cc/hp ratios ranging from 1 (F1 engine) through about 12 to 15 for a production car, up to more than 40 for some unidentified industrial engines. I would be interested to know if there is a theoretical lower limit for this ratio. I guess it must be limited by the speed at which fuel can burn. --Heron (talk) 19:43, 22 June 2009 (UTC)[reply]

Is time finite or infinite?

Is time finite or infinite? Bus stop (talk) 07:41, 22 June 2009 (UTC)[reply]

The answer to your question isn't known. The solid consensus among scientists is that a Big Bang occurred, so time for sure has a finite beginning. However, there isn't a solid consensus regarding the ultimate fate of the universe. If it turns out that there will be a Big Crunch, then time also has a finite ending, so time is finite. But if there is a Big Freeze, then time will continue indefinitely, and time will be infinite. Red Act (talk) 08:06, 22 June 2009 (UTC)[reply]

I'm going to hedge my statement even further. There actually isn’t even a complete consensus as to whether the Big Bang marks the beginning of time. Although I don’t think the idea is widely favored, one possibility under consideration by some cosmologists is that the Big Bang was actually a Big Bounce. Red Act (talk) 08:15, 22 June 2009 (UTC)[reply]

I think a big crunch has been pretty much ruled out now. That would require the expansion to be slowly fairly quickly, it is actually measured to be speeding up. --Tango (talk) 14:40, 22 June 2009 (UTC)[reply]

Just to confuse things still further it may not even be 1 dimensional at the smallest scales though that's getting very speculative. See Spacetime and Multiple time dimensions. Dmcq (talk) 11:53, 22 June 2009 (UTC)[reply]

I agree with everything that's been said already - but I'd say that on balance, the smart money is on time having a finite beginning at the moment of the big bang - and no ending (ie it's infinite) - although when the overall entropy of the universe gets small enough, nothing will be "happening" so it would be hard to measure the progress of time. But there are other possibilities that have not yet been entirely discounted. 15:10, 22 June 2009 (UTC)

Don't you mean when entropy (absence of ability to complete work) gets large enough? Or am I missing something? —Anonymous Dissident^Talk 15:18, 22 June 2009 (UTC)[reply]

Actually, I'd suggest that many physicists believe that some form of time and space existed before the Bang, but that our theories and experiments are simply inadequate to understand what came before the apparent singularity. Quantum gravity, whatever form that ultimately takes, will almost certainly eliminate true singularities and create a path to considering space-time before the Bang (though that space-time may be structurally very different than our present reality). Dragons flight (talk) 16:01, 22 June 2009 (UTC)[reply]

I think most physicists consider "what happened before the big bang" to be an unscientific question since it is impossible for us to know. The big bang wipes the universe clean, so to speak, so there is no information left from that time for us to observe. If we can't observe something then, from the point of view of science, it doesn't exist. --Tango (talk) 16:48, 22 June 2009 (UTC)[reply]

There is a difference between an unanswered question and an unscientific question. No one has evidence of extraterrestrial life, and yet there are many theories for what could exist out there based on our understanding of chemistry and terrestrial life, and someday those theories may be tested. Similarly, there are theories (e.g. Big Bounce, brane collisions, "true" vacuum) for what might have come before the Big Bang. We don't know how to test those ideas today, but that doesn't mean that they will never be tested. For example, most quantum gravity proposals lead necessarily to the conclusion that there was a "before the Bang". If we ever validate one of those proposals as likely correct for the modern universe, then it would be indirect evidence of what the universe may have been like before the Big Bang. Nor is it necessarily true that the Big Bang wipes the universe clean. In the speculative brane collision cosmologies, there could be remnants of before the Bang imprinted on the distribution of dark matter. (That no one has found evidence of this doesn't make it uninteresting to look.) As a physicist, I would suggest that most other physicists see it as a largely intractable question, but not an intrinsically unscientific one. Dragons flight (talk) 17:24, 22 June 2009 (UTC)[reply]

Would a better question be "is time as we know it finite or infinite?" A different version of "time" could exist before the big bang and after the big crunch. --Navstar (talk) 00:45, 23 June 2009 (UTC)[reply]

Or perhaps just try to figure out how long it took to read this sentence? See Xeno's paradoxes :-). --SB_Johnny | ^talk 01:05, 24 June 2009 (UTC)[reply]

Inverted vertical tube manometer

Why the pressures within an inverted vertical tube manometer is being substracted..? —Preceding unsigned comment added by Sreekanth awh (talk • contribs) 08:26, 22 June 2009 (UTC)[reply]

Beam of light

Is there an angle that you could cast light at (in a beam) where the circle iluminated would appear the same size at all distances? Say if you shon it at a wall a foot away from you and held a ruler a couple of inches away from your eye the circle of light would appear 4" wide, and it would also appear that if you stood 10 feet away from the wall, due to perspective. Gunrun (talk) 08:43, 22 June 2009 (UTC)[reply]

I would think so. The apparent radius of a circle goes like 1/d with d the distance between you and the circle. The actual radius of the illuminated circle is proportional to d. You might want to have a look at http://en.wikipedia.org/wiki/Gaussian_beam

You'd need a "collimation" lens or mirror which makes the incoming light exit in a parallel beam. SteveBaker (talk) 15:06, 22 June 2009 (UTC)[reply]

Help with project

My friends and i are trying to do a project in the summer, which would keep us engaged, and at the same time learn something new. We are all first year undergraduate students. The basic idea is this: You have a (computer) mouse which eats light, that is, goes to the brightest area it can. It can do cool things like following the light from a torch, etc. In addition, whenever it collides with an obstacle, it veers back a couple of meters and then zooms off in some other direction. It isn't wired. This is to be done with basic electronics. We are following this book, and you can find the circuit diagram and other details in the link. But the thing is, we are facing multiple problems, and in need of help. The first problem is the IR emitter thingy. The book says the IR emitters (removed from an old mouse) will sense the incoming light, and hence act like the "eyes" of the mouse. It has given clear instructions on how to desolder the emitters and all. My question is, how can IR emitters possibly detect light? Shouldn't you use detectors? This can't be a printing mistake, he's used it several times. Then comes another problem. According to his illustrations, his emitters have 2 terminals, whereas our emitters have 3. What do we do? Worse, our detectors have four! Are there various types of emitters/detectors used in a mouse pcb,and are we stuck with a different kind? If that is the case, would the correct IR emitters/detectors be available in any electronics shop (The major electronics hub in the city is quite some distance away)? I think we are seriously in need of help... Rkr1991 (talk) 09:13, 22 June 2009 (UTC)[reply]

You really want to talk with some robot building enthusiasts, there's lots of them around on the web and they're very happy to help with newcomers. You might even find a club nearby if you're lucky. Just google for things like robots builders enthusiasts. Dmcq (talk) 12:13, 22 June 2009 (UTC)[reply]

It would be nice if someone could give me a direct link of one such site that's really good... Rkr1991 (talk) 13:07, 22 June 2009 (UTC)[reply]

I guess from what you are saying that your university does not have a robotics course or club, that would be best but you can always found one. You really do need to get to grips with searching the web, for instance you have to look at electronics catalogues like Maplin if you are going to strip things down and use the bits. Did you try a google and look at the top few entries for clubs? Wikipedia has articles on robotics from Portal:Robotics but it tends to be more institutional stuff rather than how-to and friendly. You have to suck it and see and sometimes just put the blue smoke down to a learning experience. Dmcq (talk) 14:14, 22 June 2009 (UTC)[reply]

Well, there are two kinds of mice:

Mechanical (the kind with a ball underneath)
Optical (the kind with LED's underneath)

The mechanical kind do have light sensors in them - but they'd be hard to use. If you pull the mouse apart, you'll see that the ball rolls against a pair of rollers - and if you dismantle the mouse enough - you'll see that each roller connects to a slotted disk that sits inside a U-shaped black box. That box has an LED light and a light sensor - one on each side of the disk that count the number of times the disk interrupts the light beam. But to use the light sensor in your application, you'd have to somehow get it out of the black plastic enclosure without damaging it. Maybe you can do that - but it's not something I've ever tried.
The optical kind uses a camera that looks down at your desktop and watches it slide past - measuring the speed that it moves. This is a very low-resolution camera (I vaguely recall it's a monochrome 64x64 pixel gizmo) - and the lens it looks through is focussed to produce a sharp image at a distance roughly equal to the thickness of the little rubber feet on the mouse! So you aren't going to be taking any photo's with it! However, technically - I guess you could remove the lens and let it see an amazingly blurry view of the world - which would certainly give you an overall idea of the light level. However, interfacing to the camera might take some fancy electronics...and I don't know how fancy you want to get!

I've built a robot just like you're describing - but I cheated and used Lego Technics - which lets you build such a thing in about an hour - and get the software working in a couple of hours. It can certainly be done. My son and I actually built two of them - put IR LED's on the top of each one and programmed them to play "Tag" - one robot is programmed to seek light and the other to avoid it - they each have a 'skirt' with microswitches as a 'bump' sensor - when one robot hits the other, it changes from seeking light to avoiding it and vice versa. The one that's set to seek light doesn't start moving for 10 seconds in order to give the other one time to escape - and (theoretically) they change sides. It's actually a little bit more complicated than that - they send each other messages via IR to be sure it was a legal "Tag" and not a collision with the wall or something. Anyway - it's hilarious to watch - and an interesting programming challenge to have two people each program their own bot and run it as a competition. SteveBaker (talk) 15:04, 22 June 2009 (UTC)[reply]

By the way my favourite book on this sort of thing is Hardware Hacking Projects for Geeks by Scott Fullam. Rather self identifies I guess :) With projects like for instance how to hack a furby (rather a difficult one that). or turn yourself into a Borg. Dmcq (talk) 21:04, 22 June 2009 (UTC)[reply]

We have dismantled a mechanical mouse, and got the two IR emitters and detectors out of the PCBs safely. Now, thanks for all your help, but it would be nice if someone could directly address the two questions i asked, one whether if we should use emitters or detectors, and the other, their availability and terminals (please refer to my posts above). In the meantime, I'll just hunt for some Robotics sites and clubs.... Thanks for your help everyone :-) Rkr1991 (talk) 05:14, 23 June 2009 (UTC)[reply]

Where are you, Spinningspark ? I thought you were the resident electronics specialist... Rkr1991 (talk) 05:22, 23 June 2009 (UTC)[reply]

Anyway to your question, I'd have expected four IR emitters and detectors in a mouse two for each wheel. The emitters are LEDs that emit the IR and I'd expect them to be clear and only have two legs each. If they have put two detectors in a single package then that may explain why you've found only two detectors and they have three legs. Some detectors actually do have three legs but that would be overkill for a mouse. The detectors are probably red to filter out other light. The detectors are what you want to detect the light but you probably want both the emitters and detectors, it can be quite hard enough working with the changing ambient light never mind the occasional TV controller. It is common to modulate the emitter and detect a modulated light at the detector to cut out such interference - also LEDs can be run brighter being pulsed. Dmcq (talk) 09:03, 23 June 2009 (UTC)[reply]

By the way I'd guess an IR emitter probably can be used as a detector but it sounds rather a strange idea to me when you've already got good detectors designed for the job. Dmcq (talk) 09:08, 23 June 2009 (UTC)[reply]

No - you can't use an LED as a light detector! The IR emitters in a mouse don't look like regular LED's - they are encapsulated...but if you need to detect light - the emitters aren't really of any interest. But if you have the mouse's light detectors separated out without damaging them - then you should be able to use them to detect sunlight and things like your TV remote...but many other kinds of light source don't produce enough IR to be detectable - so your robot might not be interested in seeking things like flashlights. Also, I have no idea what the sensitivity of the mouse's detectors are - they might require quite a lot of light to make them trigger because they're designed to operate with an IR LED about 5mm away - and they are also working hard to exclude the possibility of sunlight or other stray light sources from triggering the thing accidentally - so it may be designed to make sure that what you're trying to do won't work! Finding the manufacturer's data sheet for the part you're using would help an awful lot! If it has any serial numbers or anything on it - then typing that number plus "mouse" into Google would probably turn up what you need to know. SteveBaker (talk) 18:35, 23 June 2009 (UTC)[reply]

OK - let's try to answer the actual questions here.

There is no way a light emitter can be used as a detector. Your book is wrong. If it's not a misprint then the author is an idiot...which is actually possible - many of these books are written by enthusiastic amateurs who are sloppy with scientific terms.
So what you want is the detector. The two slotted disks in the mouse are used by the electronics to figure out by how much the wheel has turned - and in which direction. With a simple IR emitter and detector pair - one on either side of the wheel - you could count the number of dark/light transitions are picked up by the detector and know how many slots have passed by - and therefore, by how much the mouse has moved in that axis. However, that's not enough - you've also got to figure out the DIRECTION it's moving (forwards/right or left/backwards) - and for that you need a second detector positioned a little off to one side of the first one. By noting which detector triggers the dark/light transition first - you can figure out the direction as well as the distance.
Hence, each axis of the mouse needs TWO detectors - but you only really need one IR light source. So the black block on the side of the slotted disk that contain the emitter will have two pins - power and ground - probably just like a regular IR LED - and the black block on the opposite side which contains the detector will have three pins - probably a common ground wire and two pins where the light brightness value appears as a small voltage...or possibly as a variable resistance to that common ground.
You'll have to figure out which pin of the detector is ground. If you can trace where the three copper tracks on the circuit board went - then probably you'll find that the ground pin connects to a dozen places in the circuit - but the two other outputs each go to just one or two places. Try to trace where they go - see if there are any resistors or anything connected up along the way.
So I guess you could try to get a reading on a multimeter on the most sensitive range - see if putting the detector in bright sunlight produces a voltage or a change in resistance...that'll give you an idea of what circuits to use to interface to this beast.

But still, the best advice is to try to find a data sheet for the device...there is no substitute for knowing what the heck the thing does in detail.

SteveBaker (talk) 00:43, 24 June 2009 (UTC)[reply]

The dismantled mouse in question is more than 20 years old, there's no way I can get a data sheet for that old thing ! I'll try bread boarding the circuit now with Steve's advice using the detectors, and I'll get back if I have any doubts. And thanks for the help, everyone... Rkr1991 (talk) 08:03, 24 June 2009 (UTC)[reply]

Steve, our article LED as light sensor and the internet disagree with you. 76.11.230.33 (talk) 05:03, 25 June 2009 (UTC)[reply]

Well I just took a red LED out and tried it to see if it could be used as a detector, and I think it pretty definitely can't. I thought there was a chance it would work but no it doesn't look that way. There's nothing like checking with the real world to get yes/no answers. Dmcq (talk) 10:01, 24 June 2009 (UTC)[reply]

Wisdom Tooth Extraction After effects

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. Algebraist 09:47, 22 June 2009 (UTC)[reply]

Reaching the lowest possible temperature

How can we reach the lowest possible temperature? If something is 0 C, I can put something -5C and cool it a little. But since the absolute zero temperature does not exist, how can be cool something until the lowest existent temperature, there is nothing cooler than it...--Mr.K. (talk) 09:56, 22 June 2009 (UTC)[reply]

Bringing an object in contact with a cooler object is not the only way of cooling it. see for example http://en.wikipedia.org/wiki/Laser_cooling

Or even have a look at fridge, have you wondered how that works? Dmcq (talk) 12:25, 22 June 2009 (UTC)[reply]

For all that though, an object reaching absolute zero is not possible, because the laws of thermodynamics will insist that some energy enter your sample, which will raise the temperature above 0K. You would need a way to perfectly isolate your sample, and that is not possible. How close you get to 0K will depend on that factor. 65.121.141.34 (talk) 14:01, 22 June 2009 (UTC)[reply]

Although we have got remarkably close to it; see absolute zero.--Shantavira|^{feed me} 15:28, 22 June 2009 (UTC)[reply]

Even more remarkably, using the technical definition of temperature given by statistical thermodynamics, it is actually possible to have objects with negative absolute temperatures -- and such things have even been created in the laboratory. The way it works out, though, is that negative temperatures are hotter than infinity, and such a system will always lose heat to any system at a positive temperature that it is in thermal contact with. It remains true that no system can be at perfect absolute zero -- systems at negative temperatures cool by dropping to negative infinity and then dropping from positive infinity. Looie496 (talk) 16:58, 22 June 2009 (UTC)[reply]

Telescope on the moon

OK, forgive my lack of comprehension of science. As I understand it, because light moves extremely fast, but not infinitely quickly, whatever you see took place a fraction before you actually noticed it. And furthermore, the further away the incident is, logically, the longer ago the incident took place. So I wondered, (Q1) what happened if someone had an improbably powerful telescope and was on the moon, looking at Earth. How long ago would whatever he saw actually have taken place?

Q2 What about if the person with the telescope was even further away, say in some high-tech capsule that allowed him to survive and also get a good view from Alpha Centauri?

Q3 How far away would you need to be to see, say, the Romans invading Britain?

If there's a flaw in my logic, please point it out. --Dweller (talk) 10:13, 22 June 2009 (UTC)[reply]

The moon is about one light-second away, so an observer sitting there "now" (scare quoted because that doesn't quite make sense: see relativity of simultaneity) would see events on Earth that took place about a second ago. Similarly, Alpha Centauri is about four and a half light-years away, so an observer there would see events four and a half years ago. To see the Romans invading Britain, you'd have to be about two thousand light-years away (more or less depending on which invasion you want), perhaps somewhere near NGC 6826. Algebraist 10:20, 22 June 2009 (UTC)[reply]

Thanks for that (and that's a very pretty picture in your link). Is there some kind of 2D map of [our bit of?] the universe that I can look at that'd show me where we're talking about, to contextualise with other objects even I might have heard of? And, if I might throw yet another question, can I assume that an object c.2,000 light years away is about 500 times further away than something about 4 light years away, or is it some kind of non-linear scale? I'd assume it is, but one thing I've learned is not to make too many assumptions in ignorance. --Dweller (talk) 10:39, 22 June 2009 (UTC)[reply]

As the article states, 'light-year' is just a fancy (and shorter) way of saying '9,460,730,472,580.8km', so it's a perfectly linear scale (up to the usual quibbles involving relativity). The best map of the universe I know is this (but note that it is not linearly scaled). I can't find a decent linearly-scaled map of nearby space at present. Algebraist 10:50, 22 June 2009 (UTC)[reply]

Interesting, thanks. I can't really understand the map properly (I get that it's a log scale) - why is it rendered as a column, not (as I expected) a square? Presumably, the real universe is roughly spherical from whatever its central point is... so I expected a 2D rendering to resemble the 2D renderings we do of Earth. --Dweller (talk) 11:17, 22 June 2009 (UTC)[reply]

I think it's that shape largely so it makes a good wallchart, though the paper may contain other reasons (I read it a while ago and can't remember). The question of the Shape of the Universe is a complicated one on which I am not competent to pronounce. Algebraist 11:43, 22 June 2009 (UTC)[reply]

Maps of the Earth's surface usually only attempt to show the two dimensions of longitude and latitude. Drawing a map of the universe presents the challenge of presenting the three dimension of right ascension, declination (the astronomical equivalents of longitude and latitude) and radial distance in a two-dimensional format. The solution adopted in the case of the "column" map is to simply throw away one dimension - it does not attempt to represent declination. The vertical axis is, as you say, a logarithmic distance scale and the horizontal axis is right ascension (there is a further simplification for objects within the solar system which do not have a constant right ascension - they are placed at an arbitrary horizontal co-ordinate a horizontal co-ordinate that corresponds to their right ascension at a specific date and time). So, for example, the Andromeda Galaxy (M31) is shown almost directly above the Small Magellanic Cloud (SMC) because they have similar right ascensions, even though their declinations are very different - the SMC at a declination of -72^o is a southern sky object, whereas M31, at a declination of 41^o, is a northern sky object. To see how the universe is mapped onto the rectangular column, imagine that all the objects shown are projected onto a disc around the celestial equator centered on the Earth; cut a small hole in the middle of the disc and make another cut from this hole out to the edge of the disc; then fold the sides of the cut disc together (like closing a fan), until you have the column shown. Gandalf61 (talk) 12:06, 22 June 2009 (UTC)[reply]
They're not shown at arbitrary right ascension, they're shown as they were at 0448 UT on the 12th of August 2003. Algebraist 12:17, 22 June 2009 (UTC)[reply]
Ah, yes - thank you - fixed in my post above. Gandalf61 (talk) 12:28, 22 June 2009 (UTC)[reply]

The galaxies from the Sloan Digital Sky Survey are actually close to the equatorial plane, so the top part of the diagram is a slice rather than a projection. As for why it's a column instead of a disc: if you just plot a scale model of the equatorial plane then a lot of small-scale structure is invisible because each pixel of the image is millions of light years across. If you logarithmically scale the radial distance then you can fit in small-scale and large-scale structure, but shapes are distorted. To avoid distorting shapes you have to rescale the angular direction also, and it turns out the rescaling that's needed is to make it a fixed width at all distances. This is familiar as the fact that the complex logarithm (which is conformal, i.e. "shape-preserving") repeats at a fixed interval of 2π in the imaginary direction. The mapping they used is actually the complex logarithm with the imaginary part plotted horizontally. The authors compare it to this famous New Yorker cover. -- BenRG (talk) 13:57, 22 June 2009 (UTC)[reply]

It's probably impossible to see the romans invade britain now though, unless you're at the planet already, because to get there to see it you'd have to travel faster than than the speed of light. The invasion of the romans is moving away from our planet at light speed! Gunrun (talk) 10:46, 22 June 2009 (UTC)[reply]

Yes, I got that. If you could travel faster than light, I suppose you wouldn't need to travel to NGC 6826, you could just go to Kent! --Dweller (talk) 11:14, 22 June 2009 (UTC)[reply]
Assuming the age of Earth to be 5 billion years, at what distance in the universe would one have to be to see Earth being "born," and is there enough distance in the universe to get far enough away from the Earth to get this view, or is the universe just too small for this? And if the universe is too small to find a sufficiently distant vantage point from which to see the Earth being born, where does the light go to when it runs out of "universe" in which to travel? In fact, if I can ask one more question, where in general does light go when it reaches the outer limits of the universe? 12:07, 22 June 2009 (UTC)
Now we're into large enough scales that general relativity becomes unavoidable. To be looking at an event here 5Gyears ago, an observer would have to be five billion light years away in terms of light travel distance, but not in terms of more commonly used measures such as comoving distance or cosmological proper distance. See Distance measures (cosmology) for a discussion. Light does not reach the outer limits of the universe, because no such limits exist. Algebraist 12:13, 22 June 2009 (UTC)[reply]

You'd also need a pretty big telescope to see these things. To see the Romans invade Britain at 25 frames per second and be able to see individual Romans, the width of the mirror would have to be um well I haven't worked it out but I'd guess quite a bit bigger than the earth. Dmcq (talk) 12:34, 22 June 2009 (UTC)[reply]
We need Stephen Hawking here. Is Stephen Hawking in the house? Bus stop (talk) 12:37, 22 June 2009 (UTC)[reply]
A back-of-an-envelope calculation, ignoring all possible technicalities, suggests we're talking about an optical telescope about the size of the orbit of Pluto. Algebraist 12:40, 22 June 2009 (UTC)[reply]
Perhaps rather than one stationary large mirror we could have a series of smaller, rapidly moving mirrors that gather up light in the course of their journeys, interpolating data at convenient intervals. Bus stop (talk) 12:52, 22 June 2009 (UTC)[reply]

The light that reached that galaxy would also be a different shape, right? They'd have to decode it in some complicated way as well, right? ~ R.T.G 13:14, 22 June 2009 (UTC)[reply]
Chaps, you sound like a group of ancient scientists laughing about how many horses you'd need to tether together to get an object to move fast enough to fly. Any technology good enough to be able to get a clear view from the surface of a star is probably capable of making a telescope that doesn't depend on massive mirrors. --Dweller (talk) 13:20, 22 June 2009 (UTC)[reply]
Well, yes, but that wouldn't be nearly as much fun. Algebraist 13:51, 22 June 2009 (UTC)[reply]

That's big. But it is an opportunity. Any sufficiently advanced civilization then that was interested in what was going on round them would build telescopes the size of the orbit of Pluto. It must be possible to spot one of those I'd have thought :) Dmcq (talk) 13:48, 22 June 2009 (UTC)[reply]

One way to avoid improbably large lenses and/or mirrors would be to use gravitational lensing. Since gravity bends light - if you position your camera on the opposite side of (say) some suitably gigantic black hole - then you can use it as a lens. Of course you've just exchanged the problem of building a lens the size of the orbit of pluto for the inconvenience of having to fly your camera out to the right place (which might take a few thousand years) - and wait another few thousand for the photos to get back...but it would certainly be cheaper if you're not in a hurry. SteveBaker (talk) 14:47, 22 June 2009 (UTC)[reply]

Even cheaper if you don't pay for one hour processing. NotAHen (talk) 22:35, 22 June 2009 (UTC)[reply]

re a map of the universe, it seems mandatory that this should be linked from here. Jørgen (talk) 15:38, 22 June 2009 (UTC)[reply]
As the Pluto-orbit-sized telescope would be at NGC 6826, we would need to have another 'here' in order to be able to spot it, wouldn't we? If it were to replace the orbit of Pluto, then "they" would be using it for something other than observing Roman invasions. - KoolerStill (talk) 05:43, 23 June 2009 (UTC)[reply]

And there would be all kinds of problems with a telescope that size. For one, you would have to aim it at England, taking into consideration that England is spinning around the earth's axis at about 1,000 feet per second, the earth is orbiting the sun at about 120,000 feet per second, and that is only the earth moving, your telescope is probably moving as well. 65.121.141.34 (talk) 13:19, 23 June 2009 (UTC)[reply]

Apparent contradiction?

According to the article on Thymine, the molecular formula of this nucleoside is C₅H₆N₂O₂. However, in the image to the right I can only see two hydrogens and no carbons at all. Where are the four missing hydrogens and the five missing carbons? --83.34.187.22 (talk) 12:00, 22 June 2009 (UTC)[reply]

See skeletal formula. Algebraist 12:04, 22 June 2009 (UTC)[reply]

Rain in the East Coast, USA

Is there a scientific reason why the East Coast is getting so much rain in the past few weeks? --Reticuli88 (talk) 13:23, 22 June 2009 (UTC)[reply]

Farthest blue-shifted object?

Large-scale movement of the universe is dominated by the metric expansion of space, making further objects recede faster. But what is the farthest object that does actually travel towards us? More generally, what it the object with the largest difference between expected and observed red shift (either way)? --Stephan Schulz (talk) 14:59, 22 June 2009 (UTC)[reply]

I don't think anything outside the Virgo Supercluster (or Local Supercluster) is blue-shifted. If it is, then it's just a fluke. According to our article on the Virgo Cluster (which is the largest cluster in the local supercluster), its gravity only slows our recession from it by 10%, so nowhere near enough for us to be moving toward it. So I suspect the farthest blue-shifted galaxy will either be in the Local Group (in which there are plenty) or in a group very nearby in the Local Supercluster. --Tango (talk) 16:54, 22 June 2009 (UTC)[reply]
We have several blue-shifted galaxies listed in the M81 Group. I can't find any blue-shifted galaxies in other nearby groups, so I'm going to put my money on the furthest away one in that group, which I can't determine (the distances don't seem to be listed anywhere, maybe because they aren't known very precisely). --Tango (talk) 17:01, 22 June 2009 (UTC)[reply]

Colours of night sky objects?

Is there an online database that lists the apparent or observed colours of night sky objects to the human eye using some sort of scientific scale? For example, Mars and Betelgeuse are redder. I know Rigel is blue in absolute terms, but is it blue to the naked eye from a human perspective? I want a version of the Hertzsprung-Russell_diagram using observed data from the human eye on Earth rather than absolute data out there in space. --Sonjaaa (talk) 16:53, 22 June 2009 (UTC)[reply]

I saw something like this a while ago but I can't find it now. If you want to search around a little, try looking up the photography technique using long exposures and movement so that stars appear as smears which makes their apparent color much more noticeable than when they are just points. Sifaka ^talk 18:37, 22 June 2009 (UTC)[reply]
The Cambridge Star Atlas [26] classifies stars by their visual appearance and presents them in color right on the charts. Will Tirion also did Sky Atlas 2000.0 [27]. It's open to interpretation as different eyes respond differently to very low levels of light, but they're the best I know of. Acroterion _(talk) 21:19, 22 June 2009 (UTC)[reply]

Does a star or planet's B-V colour index represent its apparent colour to a human observer on Earth?--Sonjaaa (talk) 00:33, 23 June 2009 (UTC)[reply]

Only in the broadest terms. Rigel and Betelgeuse are useful comparisons, both being in Orion (constellation), with Rigel (to me, anyway) seeming bluish-white and Betelgeuse rosy. Acroterion _(talk) 03:46, 23 June 2009 (UTC)[reply]

Mold on mushrooms

I often make spaghetti with different kinds of spaghetti sauces, and it seems that the mushroom sauce gets mold much more often than the tomato-only sauce. I can't imagine why, since both are the same brand, bought in the same amounts, stored in the same type of jar in the same place in the same refrigerator; the only difference between the types is the presence of cooked chunks of mushrooms. Obviously the mushrooms and the mold are different species, so it's not as if the mushrooms are manifesting themselves as mold, but realistically is there any possibility that the mold grows more readily on the mushrooms themselves, and/or that the presence of the mushrooms makes the sauce a better host for mold? Nyttend (talk) 17:49, 22 June 2009 (UTC)[reply]

My guess would be that the acidity of the tomato sauce retards mold growth. The mushrooms floating at top might provide a low-acidity area for mold growth to start. It could also be that the recipes are different regarding the sauce itself, for example one saltier than the other. Or, well, who knows? Looie496 (talk) 18:07, 22 June 2009 (UTC)[reply]
(Post e.c.)There are quite a few fungal species that specifically parasitize other fungi including mushrooms, the genera of which are escaping my memory right now; however, I strongly doubt that those are the fuzzy culprits in this case. Most likely what is infesting your sauce is similar to what infests your fruit, bread, cheese, or other items. My intuition is that your mushroom sauce has a more favorable environment for growth. The process of preparation or different ingredients may change the pH or solute concentration of the sauce to a more favorable range for instance or if it includes cooking may deactivate some of the natural preservative compounds in the tomato sauce. It could also very well be that mushrooms may be a good host for mold the same way that certain items tend to fuzz over before others do. Hope this helps. Sifaka ^talk 18:26, 22 June 2009 (UTC)[reply]
I can confirm that the mold on the mushroom sauce looks the same as the mold on the non-mushroom sauce. What I meant by "cooking" was the preparation that Hunt's puts into before I buy it — between opening the can and actually preparing the pasta, the only thing I do with the sauce it putting it into the jar. Nyttend (talk) 21:16, 22 June 2009 (UTC)[reply]

chicken eggs

Are chicken eggs sterile (free of bacteria) before the shell is opened? 65.121.141.34 (talk) 18:31, 22 June 2009 (UTC)[reply]

There are bacteria all over the surface of the shell which are there before the egg is opened. According to Egg (food)#Contamination, if the egg is laid by a healthy chicken then yes they are sterile inside, but according to this source, some very few eggs do have bacteria in the interior. Sifaka ^talk 18:48, 22 June 2009 (UTC)[reply]

Oops accidentally posted here.. removed!--87.113.12.133 (talk) 20:00, 22 June 2009 (UTC)[reply]

I see, the article says that about 1/30,000 chicken eggs in the US is contaminated with salmonella. Now I can accept the risk of eating raw cookie dough (homemade, not sold in the store, because who know how many eggs are in 1 batch). 65.121.141.34 (talk) 20:09, 22 June 2009 (UTC)[reply]

As a matter of fact - there has just been a massive recall of raw cookie dough for precisely this reason. SteveBaker (talk) 00:19, 23 June 2009 (UTC)[reply]

The recall was due to E. coli O157:H7, which is a little surprising. (See, for example, this discussion.) -- Coneslayer (talk) 11:31, 23 June 2009 (UTC)[reply]

Eradicated bacteria on a space station

If we were to create a substantial population in a space station (something like Babylon 5) and ensured that the construction and all people sent there were free of all bacteria/viruses would it remain sterile indefinitely or would the human flora be likely to eventually mutate into forms that cause illness? Thanks :-) --87.113.12.133 (talk) 19:58, 22 June 2009 (UTC)[reply]

Not quite addressing the original question here, but I would like to point out that the people who lived on such a space station long term, and eventually left would probably have the equivalent of a compromised immune system, and it would not be advisable for them to leave. 65.121.141.34 (talk) 20:06, 22 June 2009 (UTC)[reply]

Human gut flora already causes illness if it colonises places other than the gut. Always wash your hands - especially in space. 86.4.190.83 (talk) 20:48, 22 June 2009 (UTC)[reply]
E.coli which is part of normal flora has several serotypes which are major causes of food poisoning. I'm not 100% about what that actually means, but I think it convinces me that even if those serotypes didn't make it onto your station, it wouldn't remain sterile indefinitely . The debate however is for how long, if you really managed to get a completely sterile human population it could possibly be centuries or millennia before anything mutated significantly enough to cause illness. To get a bit more sci fi on the idea, on your station you'd also have to include something to sustain a human population for generations. This means you'd probably need many other organisms to take care of nutrition and decomposition. I find it hard to imagine an environment which is can sustain a human population for generations but is completely sterile. I think you'd quicker develop a population with a very poor immune system, if a bug finally did mutate or get on board, it would wipe you out most of your population.Vespine (talk) 23:15, 22 June 2009 (UTC)[reply]

"Normal human [gut] flora" are bacteria, so your premis is inconsistent: you cannot be bacteria-free and also have normal human flora. Separate;y from that, I'm not clear on how you would eliminate all bacteria and virii from a small human population in the first place. But let's assume you magically eliminate all bacteria and virii, and then re-introduce a completely-controlled set of flora as would be needed for human health. Then, you will probably get evolved pathogens as the flora mutate (as in the earlier answer.) You might also get "spontaneous" virii, as the human genome incorporates virus DNA that has been inserted by retrovirii, and it is possible that mutation or some other replication error would "liberate" a virus particle. It only takes one. -Arch dude (talk) 01:34, 23 June 2009 (UTC)[reply]
Viruses, with respect, and confirmed by Collins English Dictionary, The Oxford English Dictionary and Dictionary.com. 86.4.190.83 (talk) 07:09, 23 June 2009 (UTC)[reply]

Thanks all. I'm particularly interested in the fact DNA can spontaneously create a virus, I'll have a further look at that --87.113.128.46 (talk) 22:15, 23 June 2009 (UTC)[reply]

star diameter

Do we know of any stars whose diameter is larger then the orbit Pluto would make (at maximum distance, assuming its eccentricity was 0.0000)? What would be the angle we would be able to see if it was at the distance of Alpha Centari (sp?)?65.121.141.34 (talk) 20:53, 22 June 2009 (UTC)[reply]

Guess: No. Too big. No star could be that big. (Just a guess.) Bus stop (talk) 20:57, 22 June 2009 (UTC)[reply]
Any star even remotely that big would have long since become a black hole. To be that big and not be a black hole, you'd have to have a density of less than 3 kilograms per cubic metre (about twice that of air), and I'm pretty sure you couldn't make a star with such low density. Algebraist 21:05, 22 June 2009 (UTC)[reply]

And for the easy part: an object that big at the distance of Alpha Centauri would have an angular size of about 1.25 arcminutes, twelve times smaller than the full moon. Algebraist 21:07, 22 June 2009 (UTC)[reply]
~~Interesting, I got 0.98', did you use Pluto's aphelion distance or something? --Tango (talk) 21:15, 22 June 2009 (UTC)~~ No, I lost a factor of two, it's more like 0.49'. --Tango (talk) 21:18, 22 June 2009 (UTC)[reply]
I used the aphelion, as suggested by the OP's 'at maximum distance'. Pluto's aphelion is about 50AU, so the diameter is 100AU. Alpha Centuari is about 4.4 light years away, which according to Google is about 278255AU, so the angle is 100/278255 radians, which (according to Google again) is about one and a quarter arcminutes. Algebraist 21:23, 22 June 2009 (UTC)[reply]
I was right the first time, I actually lost two factors of two in different directions. The difference is simply because I used the semi-major axis. I didn't read the question carefully enough! --Tango (talk) 21:26, 22 June 2009 (UTC)[reply]
What were you doing with another factor of two anyway? Algebraist 21:28, 22 June 2009 (UTC)[reply]
I guess strictly speaking it was the same factor of two twice. I managed to get very confused about whether I was using the radius or diameter of Pluto's orbit. --Tango (talk) 21:38, 22 June 2009 (UTC)[reply]

(ec) I believe Antares is one of the largest stars we know of and its diameter is between those of the orbits of Mars and Jupiter, so quite a long way short of Pluto. I don't know if it is impossible for a star to be much bigger than that, but I would be surprised if any were a big as Pluto's orbit. Pluto's orbit at the distance of Alpha Centari would span ~~just under 1 arcminute, if my calculations are correct. That's about the angular diameter of Venus when it is at its closest.~~ I've just fixed an error, I get about half an arcminute. --Tango (talk) 21:15, 22 June 2009 (UTC)[reply]
We have List of largest known stars, of course. If the data is correct, VY Canis Majoris's diameter is twice that of Betelgeuse and four times that of Antares, and it would extend out to about the orbit of Saturn. Still a way to go to Pluto, though (and the more boring theory puts it at only 600 solar radii). --Stephan Schulz (talk) 21:34, 22 June 2009 (UTC)[reply]
I took a look at Pluto, Stellar classification, and List of largest known stars and found some cool stuff:
Star diameter is measured in solar radii (R_☉) (1 R_☉ = 69,550 km = 0.004652 AU)

Plutos orbit: 4,436,824,613 km (about 30 AU) at perihelion and 7,375,927,931 km (about 49 AU) at aphelion

A star would therefore have have to be 6,379 R_☉ to extend to the closest point to the sun in Pluto's orbit, and 10605 R_☉ to extend to its furthest.

The largest known star (though that size is disputed), is the hypergiant VY Canis Majoris, at between 1,800 R_☉ and 2,100 R_☉, not even close to the orbit of Pluto, but extending to somewhere around the orbit of Saturn.

Stuff I didn't know yesterday. Hope that helps! – Clockwork Soul 21:59, 22 June 2009 (UTC)[reply]

Small stars/planets

In reading about small stars (due to an earlier question here), I found this quote: "The relatively puny body weighed in at 96 times Jupiter's mass - above the threshold of 75 Jupiter-masses required for a bona fide star, which must also burn hydrogen." So, are there hydrogen-burning planets, considered planets simply because they are less than 75 Jupiter-masses? -- kainaw ™ 22:19, 22 June 2009 (UTC)[reply]

Objects around the boundary between stars and planets are called brown dwarfs. There is no generally agreed upon definition of where to draw the line between planets and brown dwarfs and between brown dwarfs and stars. What elements they fuse is a key factor in most proposed definitions, but it doesn't seem to be quite that simple. --Tango (talk) 22:21, 22 June 2009 (UTC)[reply]

Also, once an object begins to fuse hydrogen, its radius expands from the outward pressure. Take a look at brown dwarf, in particular the sections "Distinguishing high mass brown dwarfs from low mass stars" and "Distinguishing low mass brown dwarfs from high mass planets". – Clockwork Soul 22:24, 22 June 2009 (UTC)[reply]

Thanks for that article, Kainaw. Bus stop (talk) 22:26, 22 June 2009 (UTC)[reply]

In a sense, this is the wrong place to ask this question because it is another one of those problems that has more to do with the English language than with science. Just as it was highly contentious when Pluto was "demoted" from plantary status - it might be just as bad to promote a super-Jupiter exoplanet to "star" status (although fans of the 2010 sequel to 2001 might think otherwise!). It seems kinda wrong to call the second largest object within its solar system a "dwarf" and something that's probably a rather pretty pinkish-purple color "brown". But it's just linguistics - there is certainly a continuum of objects out there from things that are clearly NOT stars to things that clearly ARE - somewhere between those two extremes there is something which will allow debate on the subject to rage on for years! SteveBaker (talk) 00:14, 23 June 2009 (UTC)[reply]

In my opinion, this is a question about scientific terminology, so it belongs in science as much as language. We get many questions about scientific terminology and I feel that pushing them into a desk that, as a whole, is not expected to be watched by many people with a scientific background will cause the questions to go unanswered. -- kainaw ™ 11:27, 23 June 2009 (UTC)[reply]

I don't disagree - which is why I said "In a sense..." - rather than "This question doesn't belong here - I've moved it to the language desk for you". But the answer is the same - it's a completely arbitary choice made by people who used to think that there was such an obvious distinction between a "star" and a "planet" (or between a "planet" and a "rock") that no detailed definition was required. But as astronomers find all of these exotic objects out there that blur the boundary - they are faced with a linguistic nightmare. Hence they erect arbitary 'bright line' definitions that are never entirely satisfactory - but at least give you an idea of where to look up information and how to speak clearly to some particular audience. However, there is rarely any actual science involved in making these distinctions - it's mostly about how to define the term clearly without having to rewrite half a million textbooks. (Sadly - that's where they went wrong with Pluto.) So there isn't a scientific answer to your question - the answer is "well, that's how the words are defined"...it's unsatisfying - but true. SteveBaker (talk) 13:06, 23 June 2009 (UTC)[reply]
There wasn't really a good solution with regards to Pluto, though. The textbooks needed to be rewritten to remove Pluto as a planet, rewritten to add several other objects as planets or left inconsistent. Any of those options would have really annoyed a large group of people. --Tango (talk) 15:18, 23 June 2009 (UTC)[reply]

Talk:Liquid crystal display

There are accumulating unreplied remarks on that page and, of course, there is probably a bunch of you who could answer them. (is mainstream isn't it?) ~ R.T.G 22:32, 22 June 2009 (UTC)[reply]

Feel free to go there and recommend that people direct questions that are unrelated to the business of writing that article to us here at the science ref desk. But we shouldn't create little side-branches of the Ref Desk in odd little places like that. Article talk pages are intended to be forums where you talk about the business of writing about the article - they aren't really places for answering questions about the subject matter of the article. SteveBaker (talk) 22:58, 22 June 2009 (UTC)[reply]

I think they are mostly concerning the content of the article but they are also very technical posts and unanswered for some time (stuff like Mother glass and "Wasn't that invented by so and so?"). ~ R.T.G 00:14, 23 June 2009 (UTC)[reply]

A better place to note stuff like this about an article is probably the discussion page of the WikiProject that encompasses that article. Tempshill (talk) 01:31, 23 June 2009 (UTC)[reply]

The OP doesn't mention their own (speculative) question that has gone unanswered at Talk:Liquid crystal display. I have added a reply that I hope will satisfy. Cuddlyable3 (talk) 14:41, 23 June 2009 (UTC)[reply]

I think the lead was very technical and even wrong when I asked that question. Very good, Cuddlyable3, thank you. I believe that is the first response to a post in a year. ~ R.T.G 16:37, 23 June 2009 (UTC)[reply]

Special relativity and Emission theory

Does an observer move relative to the light cone? Special relativity says "Special relativity incorporates the principle that the speed of light is the same for all inertial observers regardless of the state of motion of the source.", and if an observer moves relative to the light cone, the speed of light is not the same for the observer. And as, if we slide the axis of the path of the observer to enable to regard the observer not moving, then the axis of the light cone is slided accordingly, and it turns out that the speed of light is fixed to the source (like in emission theory). But if an observer does not move relative to the light cone, the plane sharing simultaneity does not seem to tilt. Like sushi (talk) 23:18, 22 June 2009 (UTC)[reply]

The question doesn't make sense. A light cone is only defined for a specific event, that is a fixed point in space and time. If you are moving (or even if you're not - you'll at least be moving through time) then at each point you have a different light cone. It doesn't make sense to talk about moving relative to a light cone or not. --Tango (talk) 23:41, 22 June 2009 (UTC)[reply]

Maybe the use of the term is wrong. I meant by "light cone", the cone made by light from a source. And if there are numbers of observers in the same reference frame, the motion of the observers (the refrence frame) is notable.

Like sushi (talk) 00:18, 23 June 2009 (UTC)[reply]

I mean by "moving relatively to the light cone", that the axis of the path of the observer is not parallel to the axis of the cone.

Like sushi (talk) 00:37, 23 June 2009 (UTC)[reply]
So you don't mean the technical term? A "light cone" (well, a "future light cone", which is probably what is relevant here) in relativity is the region of spacetime that light emitted from an event can fill (it's not really a cone, it's the 3D analogue of a usual 2D cone). If that's not what you mean, you are going to need to be more precise about what you do mean. For example, are you talking about a cone is 3D space or 4D spacetime? --Tango (talk) 01:20, 23 June 2009 (UTC)[reply]
What I meant is a 4D one, though it can serve, in this case, even if it was 2D + time, or even 1D + time. And it is not "the region of spacetime that light emitted from an event can fill" but "actually is going to fill". And it is (as I thought you might be taking it) not from a point the observer goes through, but from a source apart from him.

And I repeat. I mean by "moving relatively to the light cone", that the axis of the path of the observer is not parallel to the axis of the cone.

Like sushi 01:34, 23 June 2009 (UTC)[reply]
In special relativity, the light cone does not have a unique axis. One of the consequences of relativity theory is that the light cone emanating from a given point in space-time is the same regardless of the velocity of the object that emits the light. No matter what the velocity, relativistic time dilation causes the light to look from the emitter's point of view like it's traveling away at constant velocity in all directions. Looie496 (talk) 04:32, 23 June 2009 (UTC)[reply]

(Edit conflict) (indent) The problem is that you can’t just ask if something is "moving", or talk about "the axis" of a light cone, without specifying which inertial frame of reference "motion" is defined relative to, and "the axis" of a light cone is defined in. To use a concrete example, suppose two spacecraft are moving away from each other at some constant speed v, where v is a sizeable fraction of the speed of light. Somewhere in the rough vicinity of the two spacecraft, a flashbulb goes off. Associated with each spacecraft is an inertial frame of reference such that in that frame of reference, the associated spacecraft is stationary, and the flashbulb goes off at the origin of the associated 4-D coordinate system.
The flashbulb going off is an event in spacetime. Associated with the flashbulb going off is a future light cone, which consists of the set of all events in spacetime such that light from the flash reaches that point in space at that point in time. Call the two spacecraft A and B, with associated inertial frames A and B. In inertial frame A, the future light cone associated with the flashbulb going off consists of all events (points in spacetime) such that r=c t, where r is the spatial distance from the flashbulb event as measured in inertial frame A, t is the time since the flashbulb event occurred as measured in inertial frame A, and c is the speed of light. In inertial frame B, the future light cone associated with the flashbulb going off consists of all events such that r’=c t’, where r’ is the spatial distance from the flashbulb event as measured in inertial frame B, t’ is the time since the flashbulb event occurred as measured in inertial frame B, and c again is the speed of light. The speed of light is the same constant value in both frames of reference.
The two observers agree as to which events are on the light cone, but they will disagree as to what the coordinates are of the events on the light cone. E.g., observer A might say that a given event on the light cone occurred 1 second after the flashbulb event, and is 1 light-second away from where the flashbulb event occurred. Meanwhile, observer B might say that the same event on the light cone occurred 2 seconds after the flashbulb event, and is 2 light-seconds away from where the flashbulb event occurred.
More importantly, although observers A and B agree as to which set of events are on the light cone, they do not agree as to which set of events are on the axis of the light cone. Observer A will say that the axis consists of all the events for which r=0, i.e., the world line of an object that was at the flashbulb event, and which is stationary as measured in inertial frame A. In contrast, observer B will say that the axis consists of all the events for which r’=0, i.e., the world line of an object that was at the flashbulb event, and which is stationary as measured in inertial frame B. The only event that observers A and B will agree is on the axis is the origin of the two coordinate systems.
In short, observer A will say that the axis of the light cone is parallel to spacecraft A, i.e, spacecraft A is not moving relative to the axis of the light cone, and spacecraft B is moving relative to the axis of the light cone. In contrast, observer B will say that the axis of the light cone is parallel to spacecraft B, i.e, spacecraft B is not moving relative to the axis of the light cone, and spacecraft A is moving relative to the axis of the light cone. It’s an exactly symmetrical situation, and neither observer is the "correct" one. Red Act (talk) 05:26, 23 June 2009 (UTC)[reply]

"the light cone does not have a unique axis" and "you can’t just ask if something is "moving", or talk about "the axis" of a light cone, without specifying which inertial frame of reference "motion" is defined relative to, and "the axis" of a light cone is defined in".

I see. Then the speed of light is the same for all the observers. And no observer moves relative to the light cone, or rather have an axis not parallel to the axis of the cone in the refernce frame of himself.

Thank you.

But as I tried to think about it, I would like to give this thought some space. Is it possible? For example, that an observer in a reference frame can have an axis of motion not parallel to the axis of the light cone in another reference frame, or something?.

Like sushi (talk) 06:20, 23 June 2009 (UTC)[reply]
I’m not sure I understand your question. As long as inertial reference frames A and B aren’t stationary relative to each other, then the world line of something that’s stationary according to observer A will for sure not be parallel to a world line that’s the axis of a light cone according to observer B, if that’s what you mean. Red Act (talk) 08:34, 23 June 2009 (UTC)[reply]

Well, come to think of it, if the observers have to have an axis of motion parallel to axes of light cones in all reference frames, then the axes of the light cones and (as the axis of a light cone is an axis of motion to at least one observer) of the motion have to be all parallel. That means no motion possible. The one I have come up with is only (a tiny bit) useful when trying to imagine the picture of a light cone and a path of an observer in a different reference frame (because I can recall the image I made for these posts, which hopfully can be used for other purpose).

Like sushi (talk) 08:54, 23 June 2009 (UTC)[reply]
Again, you have to be careful to always specify which observer you’re talking about, whenever you talk about any observation. And I’m having a hard time understanding your question, because I’m not sure what you mean by an "axis of motion". Do you mean the world lines traversed by objects which are stationary according to a given observer, or the world lines traversed by any object that’s moving at some fixed speed according to a given observer?

For a given observer, the axes of all light cones according to that observer, and the world lines traversed by all objects that are stationary according to that observer, are all parallel. Those lines all point in the direction that’s "forward in time" according to the given observer. All those lines are not, however, parallel to the world lines traversed by objects that are moving at some nonzero fixed speed according to the given observer, or parallel to the axes of light cones according to a different observer, or parallel to the world lines traversed by objects that are stationary according to a different observer. Red Act (talk) 10:41, 23 June 2009 (UTC)[reply]

I meant by an "axis of motion", the world lines traversed by objects which are stationary according to a given observer.

Like sushi (talk) 12:28, 23 June 2009 (UTC)[reply]

~~No. I think I have found another problem. That is when the observer is out of the light cone and eventually touches its surface. The first question now makes sense? or is it still faulty?~~ I am confused. Like sushi (talk) 10:18, 23 June 2009 (UTC)[reply]

An "observer" in special relativity actually refers to a whole inertial reference frame, and shouldn't be pictured as being one person sitting at one point, receiving light from all around. That's a common misperception among beginning students of special relativity.

The world line traversed by an object moving at some fixed speed (including 0) can certainly intersect a light cone that emanates from some event. For example, the time axis of an inertial frame can certainly intersect a light cone. And the time axes of various inertial frames are not in general parallel, if that's the question. Even if two inertial frames share the same origin, the time axes of the two inertial frames will point in different directions, as long as the two inertial frames are moving relative to each other.

Where's Steve Baker? He's good at explaining special relativity in a way that's understandable to beginners. Red Act (talk) 10:41, 23 June 2009 (UTC)[reply]

I have managed to get out of the confusion. All light cones assume axes parallel to the axis of motion of the observer in the reference frame of him. Like sushi (talk) 11:10, 23 June 2009 (UTC) Or do they not? Like sushi (talk) 11:15, 23 June 2009 (UTC)[reply]

It sounds like you might be thinking about the problem correctly. According to an arbitrary observer A, the axes of all light cones extend in the "forward in time" direction in spacetime, and hence are parallel to the world lines traversed by all objects which are stationary (according to observer A), which also extend in the "forward in time" direction. Those axes and world lines identified by observer A will also appear as being parallel to observer B, although they will not extend purely in the "forward in time" direction according to observer B. Furthermore, observer B will say that the world lines identified by observer A are for objects which are not stationary, and will say that what observer A has identified as being the axes of the light cones are not the actual axes of the light cones. Red Act (talk) 13:06, 23 June 2009 (UTC)[reply]

Sorry,I didn't notice Mr.or Ms. Red Act has written. The axes of all light cones according to that observer are parallel. So the contents of a light cone is always the same for any observer, i.e. the light cone occupies the same spacetime, and only difference is the coordinate system which gives the event the time and location? In fact, I have posted to the math desk to confirm that two points at which observers moving parallel to the source of the cone, are the same distance away, and in a plane with the same y (the spacial axis perpendicular to the direction of motion of the observer) and the light cone meet always make a line of the same tilt, if the velocity of observers are the same (in mathematical form). But I could not be answered somehow. (About for what reference frame, I think I didn't specify. I was thinking only in one reference frame.) If all planes sharing simultaneity is inclined at the same rate in any one reference frame, no matter from what plane you start, the resulting planes are the same if any numbers of observers travel for the same time in their common reference frame, and as such, with the same velocity. Is it that it does not matter if it's the section with the light cone or not, but "from and onto the same plane" and "along parallel lines", and if not we can not simply compare them? Like sushi (talk) 12:28, 23 June 2009 (UTC)[reply]

I can answer the first question in this paragraph easily: Two observers, A and B, will agree about what set of events constitute the events within a light cone, although they will label those events with coordinates differently. However, the two observers will not agree about what set of events constitute the axis of the light cone. Beyond the first question in your paragraph, I’ll have to think a bit to see if I can understand what you’re asking. Red Act (talk) 13:18, 23 June 2009 (UTC)[reply]
I'm afraid I have gone a little too wild. It does matter if it's the section with the light cone or not, and although "from and onto the same plane" and "along parallel lines" motion has always the same properties other than the starting point and end point, the problem is not that, but whether or not the shape made in the distorted coodinate system by the light cone is the same to the light cone in right coordinate system if the distorted coordinate system is transformed to the right one.

Like sushi (talk) 14:50, 23 June 2009 (UTC)[reply]

I think, in one reference frame, a tilted world line (I am not used to this term) of another observer moving relative to you which shows another axis of the light cone goes through the center of the ellipse which is the section of the light cone and the plane of simultaneity for that observer in the first reference frame. If that distorted cone (it is not distorted in outer cone though) can be transformed in to the right cone, making the right cone the distorted cone, then the reciprocity is shown. Like sushi (talk) 13:27, 23 June 2009 (UTC)[reply]

I’m falling asleep. I’ll have to respond to this this evening, if someone else doesn't step in and respond before then. Red Act (talk) 14:50, 23 June 2009 (UTC)[reply]

Did nobody link to Lorentz transformation? Look at it this way, Lorentz transforation is just rotation, but we don't live in euclidean geometry. In our geometry, no matter how you rotate a light cone it stays exactly the same. If you were to rotate a line, it would not. As such, you can't say it has an axis any more than you can say an infinitely long line has a midpoint. Look at the third picture from the top (the moving one) to see how Lorentz transforation works, and how it doesn't affect the light-cone. That animation is also moving through time, and the light cone is moving too. If I could find one without that, I'd show that. Just try to ignore the fact that all the events are moving backward. — DanielLC 15:42, 23 June 2009 (UTC)[reply]

I have noticed that the diagonal lines (the edges of the light cone in the plane y=z=0),are not affected by the transformation. And the outer cone is the same with and without the transformation. As I think (if it is arbitrarily set) the axis of the cone or the world line of the observer moving in respect to the right coordinate system goes through the center of the ellipse which is the section of the light cone and the plane of simultaneity for the distorted coordinate system, it just need to adjust the x-axis to make the distorted cone (of which the surface is not distorted) right.
But does the transformation to make the distorted cone the right one makes the right cone the distorted one with the opposite tilt? And does the y- or z- width of the ellipse section of the transformed light cone appears to be small than the radius of the circle section of the right cone with the centers at the same time in the reference frame of the right coordinate system? (I think that means if the observer regarding himself stationary measures the travel distance of light for the other observer moving relatively to him, in y or z in his right coordinate system, at the same time in his reference frame, it is less than his.)
(I think I have managed to understand , with the help of all of you, that the light cone is always the same if the coordinate system is adjusted to the right one, though the distance to the origin of the light cone in spacetime is different. The questions I am asking now is on the side of the original one, which was about if the shape of light cones, and thus the speed of light are always the same in all (right) coordinate systems, or for all observers who regard themselves at rest.)
Thank you very much for all of you! And I hope you will answer the side questions. Like sushi (talk) 23:39, 23 June 2009 (UTC)[reply]
Alhough it is difficult to imagine, caliculating Lorentz transformation,
$t'=\gamma (t-{\frac {vx}{c^{2}}})$
$x'=\gamma (x-vt)$
for t and x gives
$t=\gamma (t'+{\frac {vx'}{c^{2}}})$
$x=\gamma (x'+vt')$ .
So coordinate system A from perspective of B is coordinate system B from perspective of A just with the opposite v. It seems a light cone for A from perspective of B has just the opposite tilt of the light cone for B from perspective of A. (I changed the way of describing coordinate systems and light cones, accoring to (I hope) Mr. or Ms. Red Act's comment below. In the former way of writing, "the transformation to make the distorted cone the right one makes the right cone the distorted one with the opposite tilt.") Like sushi (talk) 06:42, 25 June 2009 (UTC)[reply]

I’m having a bit of a problem with some of the terminology you’re using. You talk about a "right" coordinate system vs. a "distorted" coordinate system, and a "right" light cone vs. a "distorted" light cone. There is no one "right" coordinate system, in either the sense of "correct" or "orthogonal". In general, whether two lines or two planes in spacetime are at "right angles" to one another depends on which coordinate system you are using. And there is no preferred or "correct" coordinate system, except that we are here limiting our discussion to inertial frames of reference. All inertial frames of reference are equally valid, in that the laws of physics are the same regardless of what choice of coordinate system they are expressed in. If you have two observers A and B moving relative to each other, the coordinate system used by A, which has axes that are all at "right angles" according to observer A, will not in general have axes that are at right angles according to observer B. And the coordinate system used by B, which has axes that are at right angles according to observer B, will not in general have axes that are at right angles according to observer A. When working with only two observers, it’s convenient to define the coordinates used by observer A such that the motion of observer B relative to observer A is parallel to one of observer A’s spatial coordinate axes (usually observer A’s x axis), and define the coordinates used by observer B such that the motion of observer A relative to observer B is parallel to one of observer B’s spatial coordinate axes (usually observer B’s x axis). That way, at least the two observers will agree that each other’s spatial coordinate axes are orthogonal. The two observers won’t, however, agree as to whether each other’s spatial coordinate axes are orthonormal, and won’t agree as to whether the "time" axis of an observer is at "right angles" to that observer’s spatial axes. Instead of "right" vs. "distorted", a better description would be coordinate system "A" vs. coordinate system "B", or quite commonly, the "primed" coordinate system vs. the "unprimed" coordinate system. However, which coordinate system is chosen to be labeled as being "primed" and which is chosen to be labeled as being "unprimed" is really an arbitrary choice.

Two parts of what you seem to be interested in pertain to the "axis" of a light cone, and the intersection of a light cone with a hyperplane of simultaneity. I think it’d be helpful to examine those two things mathematically from the point of view of two observers. Choose the origins of the two coordinate systems involved to be the event at the vertex of whatever light cone you’re talking about. Then choose the orientation of the two coordinate systems to be based on the motion between the two observers, such that the coordinate systems are in what the Lorentz transformation article calls the "standard configuration". I’ll adopt that article’s notation that there’s an observer O that uses the coordinates $(t,x,y,z)$ , and an observer Q that uses the coordinates $(t',x',y',z')$ . I’ll follow that article’s notation closely, but I’ll also take the additional step of choosing units of distance and time such that the speed of light is one, i.e., $c=1$ .

Observer Q would describe the light cone as being the set of all events such that ${t'}^{2}={x'}^{2}+{y'}^{2}+{z'}^{2}$ . Observer Q would consider the "axis" of the light cone to be the set of all events such that $x'=y'=z'=0$ . What observer Q considers to be a hyperplane of simultaneity is the set of all events such that $t'={t'}_{0}$ for some constant value of ${t'}_{0}$ . The intersection of that hyperplane of simultaneity with the light cone is the set of all events such that $t'={t'}_{0}$ and ${{t'}_{0}}^{2}={x'}^{2}+{y'}^{2}+{z'}^{2}$ .

Now we’ll express all of the above geometrical objects in terms of Observer O’s (unprimed) coordinates, by substituting the Lorentz transformation article’s expressions for the primed coordinates in terms of the unprimed coordinates into all of the above equations, and simplifying:

Observer Q’s description of the light cone, ${t'}^{2}={x'}^{2}+{y'}^{2}+{z'}^{2}$ , gets expressed in the unprimed coordinates as $[\gamma (t-vx)]^{2}=[\gamma (x-vt)]^{2}+y^{2}+z^{2}$ , which simplifies down to $t^{2}=x^{2}+y^{2}+z^{2}$ . Thus, what observer O considers to be the light cone for a given event is the exact same thing as what observer Q considers to be the light cone for the given event, and is expressed in the exact same way.

Observer Q’s description of what observer Q considers to be the axis of the light cone, $x'=y'=z'=0$ , gets expressed in the unprimed coordinates as $\gamma (x-vt)=0$ , $y=z=0$ , which simplifies to $x=vt$ , $y=z=0$ . Thus, what observer Q considers to be the axis of the light cone is different from what observer O considers to be the axis of the light cone, which is the set of all events such that $x=y=z=0$ .

Observer Q’s description of the hyperplane of simultaneity, $t'={t'}_{0}$ , gets expressed in the unprimed coordinates as $\gamma (t-vx)={t'}_{0}$ , which can alternatively be expressed as $t=vx+{t'}_{0}/\gamma$ . Since the right-hand side of this equation is not a constant, the hyperplane that observer Q considers to be a hyperplane of simultaneity is not a hyperplane of simultaneity according to observer O.

Observer Q’s description of the intersection of what observer Q considers to be a hyperplane of simultaneity with the light cone, $t'={t'}_{0}$ and ${{t'}_{0}}^{2}={x'}^{2}+{y'}^{2}+{z'}^{2}$ , gets expressed in the unprimed coordinates as $\gamma (t-vx)={t'}_{0}$ and ${{t'}_{0}}^{2}=[\gamma (x-vt)]^{2}+y^{2}+z^{2}$ . The first equation can be expressed as $t=vx+{t'}_{0}/\gamma$ , which when used to substitute for $t$ in the second equation leads after simplification to ${{t'}_{0}}^{2}={(x-t_{0}v\gamma )^{2}}/{\gamma ^{2}}+y^{2}+z^{2}$ . This is an ellipsoid, whose center is at $t=\gamma t_{0}$ , $x=t_{0}v\gamma$ , $y=z=0$ . This center point of the ellipsoid, as you seem to have guessed, is the same event that’s at the intersection of the hyperplane of simultaneity (according to observer Q), and what observer Q considers to be the axis of the light cone. Red Act (talk) 06:06, 24 June 2009 (UTC)[reply]

Thank you. Although I do not know much about the formulation of the things we are considering now, I could somehow follow the mathematical examination.

So, if I want to express what I called "right" coordinate system, "coordinate system A in coordinate system A", and for "distorted" coordinate system, "coordinate system A in coordinate system B" are prefered?

Like sushi (talk) 08:07, 24 June 2009 (UTC)[reply]

BDNF and Nuclear Accumbens

Does anyone know where I could find some information on micro-dissection techniques of the nuclear accumbens in California mice? (Peromyscus Californicus) I was also wondering what the significance of a Tyrosine hydroxylase antibody would be on localizing BDNF activity.(Specifically in the Nuclear Accumbens)
ArmyOfFluoride (talk) 01:20, 23 June 2009 (UTC)[reply]

For questions at that level of detail, your odds are better searching on Google Scholar than asking on Wikipedia. There are about half-a-dozen neuroscientists who hang out around here, including me, and I don't think any of us could address those questions. Regards, Looie496 (talk) 04:26, 23 June 2009 (UTC)[reply]

Come on, Looie... no harm giving it a try. ;-)

Tyrosine hydroxylase (TH) is one of the enzymes involved in production of dopamine. Neurons that are stained by the TH antibody (see immunohistochemistry) will be the dopaminergic neurons. I'm not sure if the antibody will stain just the neuronal cell body or also the axon terminals. The nucleus accumbens article tells us that "Dopaminergic input from the VTA (ventral tegmental area) is thought to modulate the activity of neurons within the nucleus accumbens." Brain derived neurotrophic factor (BDNF) is vital for nervous system development and a quick search on PubMed reveals several relevant articles [28][29][30] suggesting that BDNF is particularly important in dopaminergic pathways. If I tried to connect the dots here I'd say that the significance of finding TH antibody staining in the nucleus accumbens is probably a marker for BDNF release/activity and that you might see varying levels of staining under different conditions that activate/inhibit the dopaminergic system.

With regard to micro-dissection, I would expect that the neuroanatomy of the California Mouse is similar enough to typical laboratory mice that you could work out the technique using any good microdissection atlas. "The Mouse Brain in Stereotaxic Coordinates" [31] is a classic. --- Medical geneticist (talk) 14:14, 23 June 2009 (UTC)[reply]

June 23

iPhone Oleophobic coating

Wasn't sure if I should put this in science or technology. But it seems more chemstry related. The new iPhone 3GS screen has an "Olephobic" coating that claims to reduce fingerprints and ease cleaning. How does something like that work? Will I harm the coating if I install a screen protector film on top of it? --Navstar (talk) 00:42, 23 June 2009 (UTC)[reply]

Oleophobic means something like 'oil rejecting' - so I presume it rejects the oils in your fingerprints. Any water-based substance would do that - so it's not magic. Using a screen protector makes having this fancy screen kinda pointless - and it's actually quite possible that a regular screen protector might not stick to it if it uses oil-based adhesives. Sadly, our Lipophobicity doesn't help much. SteveBaker (talk) 03:09, 23 June 2009 (UTC)[reply]

The Hydrophobe article desribes the reverse situation pretty well. Just replace 'oil' everywhere you see 'water' and 'polar' where you see 'non-polar' and you'll get the idea. --Shaggorama (talk) 05:07, 24 June 2009 (UTC)[reply]

Driving upside down in a tunnel

How would this work? Are they talking about driving on the ceiling of the tunnel (ala Men in Black)? Presumably the driver would start on the road and then have to veer up the wall until they were on the ceiling and then veer back down? Is that what they are talking about? Is that conceivable possible? NotAHen (talk) 05:54, 23 June 2009 (UTC)[reply]

I don't think you'd have to be travelling 190mph to drive upside down, for a short distance of course. What they're probably talking about is the effect from the body, presumably the spoiler, pushing down on the car while driving at high speeds, essentially sticking it to the roof of the tube. That would be pretty damn cool mind you. 124.154.253.146 (talk) 06:30, 23 June 2009 (UTC)[reply]

The reference confirms that, stating that that it's the effect of the downforce, and now that I think about it, the whole car is going to have to contribute to the effect, not just the spoiler. 124.154.253.146 (talk) 07:17, 23 June 2009 (UTC)[reply]
Theoretically it's possible, but I wouldn't believe it till I see it. And I sure as hell wouldn't volunteer to test it. People have been trying to do that for years, often with fatal results. I doubt this one will turn out different. The effect of gravity would far outweigh any upwards force the spoiler (or even the entire car) may have.Drew Smith What I've done 08:48, 23 June 2009 (UTC)[reply]
Roller coaster trains travel upside down without gravity throwing them to the ground, and they are far from aerodynamic. True they also stay upside down only a short distance. I don't see either train or car driving through the Chunnel upside down.- KoolerStill (talk) 09:10, 23 June 2009 (UTC)[reply]
They do employ scientists (don't they?), so I don't think gravity would "far outweigh" the downforce (er...upforce) of the car - any scientist would spot such an obvious flaw. I'm not saying it would work - just that I'm not sure the problem would be as simple as that. Vimescarrot (talk) 09:56, 23 June 2009 (UTC)[reply]
Roller coaster trains generally have wheels which affix to the top and bottom of a rail to enable them to hang on when upsidedown. They're of little relevance to this discussion. --Tagishsimon (talk) 10:01, 23 June 2009 (UTC)[reply]

Aerodynamic downforce on a racing car can be much greater than its weight. www.formula1.com says "A modern Formula One car is capable of developing 3.5 g lateral cornering force (three and a half times its own weight) thanks to aerodynamic downforce. That means that, theoretically, at high speeds they could drive upside down." But still sounds extremely difficult to achieve in practice with any reasonable margin of safety. Gandalf61 (talk) 12:24, 23 June 2009 (UTC)[reply]
That's not really correct. The downforce only has to be enough to allow the tyres to exert 3.5g of lateral frictional forces - you don't need 3.5g (or even 1g) of downforce in order to do that. Although a formula 1 car may well have that much downforce - it's not numerically related to the lateral cornering forces. My old autocross car could produce 1g lateral at just 40mph - but it hardly had any down-force at that speed...it was all down to having wide, sticky tyres and suspension that's stiff enough to keep all four wheels planted flat onto the road. SteveBaker (talk) 12:52, 23 June 2009 (UTC)[reply]

It's not complicated - the shape of the body of the car (and all of it's spoilers and other aerodynamic features) are designed to push the car downwards against the road to get better grip at high speeds. If the amount of that force exceeds the weight of the car then it could be driven at that speed along the ceiling of a suitable building - held up by the force of the air against the body. This shouldn't come as much of a surprise - that's what makes an aeroplane fly. If you took a typical light aircraft (a Cessna or something) and mounted a set of wheels on the roof - you wouldn't be surprised that it could fly along with it's "roof wheels" rolling along the ceiling...held up only by the airflow over its wings...and that's what this car is (theoretically) able to do. It's body is an inverted wing-shape. How you'd get the car to do this in practice would presumably to be to have a few miles of nice straight concrete pipe - maybe 20' in diameter (think about that scene in "The Italian Job" when the Mini's are driving through the sewer - driving up the walls of the pipe). The car accelerates until it's going fast enough for the downforce to exceed it's weight - then the driver slowly steers to one side - the car gradually creeps up the side of the pipe and across the "ceiling" until it's completely upside-down. So long as he never slows down - the car should stick to the top of the pipe without problems. SteveBaker (talk) 12:52, 23 June 2009 (UTC)[reply]
...aside from the possibility of fuel and oil starvation, due to the pickups not being immersed. -- Coneslayer (talk) 14:06, 23 June 2009 (UTC)[reply]
Since the claim would be easy to demonstrate in a scaled wind tunnel model one may reasonably ask why that has not been done? Cuddlyable3 (talk) 14:10, 23 June 2009 (UTC)[reply]
Because (a) it's not particularly useful and (b) we have airplanes that do precisely this thing - so it's hardly very exciting or valuable science. However, it IS the kind of thing the Mythbusters could get interested in trying! SteveBaker (talk) 18:20, 23 June 2009 (UTC)[reply]

In the DVD extra documentary for the Italian Job, it's mentioned that in test drives, they managed to get a Mini to go right round the pipe, including upside down - just once, and couldn't reproduce it for the live run. Obviously that's a simple loop-the-loop, rather than sustained upside down driving, but the mention of the pipe-driving scene reminded me of this anecdote. AlexTiefling (talk) 14:33, 23 June 2009 (UTC)[reply]
Funny how people are overcomplicating things here. A car driving on the roof is simply flying, like an airplane. All that's needed is enough lift, which is a function of body shape and airspeed. Looie496 (talk) 16:15, 23 June 2009 (UTC)[reply]
Well, there's a bit more to it than that. As Coneslayer says, a car isn't usually designed mechanically (or, indeed, structurally) to work upside down. Remember that the reverse downforce/lift only acts on certain components of the car's bodywork - for most of the car's components, down is now up. I think at the very least you would want to do a static test first - start car and hang it upside from a crane to make sure nothing important falls off. Like the engine. Gandalf61 (talk) 16:28, 23 June 2009 (UTC)[reply]
It's certainly possible that things like fuel feeds would go dry - but if you actually wanted to do it - that wouldn't be hard to fix. SteveBaker (talk) 18:20, 23 June 2009 (UTC)[reply]

There is stuff about that it Formula_1#Cars_and_technology but it is unsourced. I couldn't find the right page on f1.com earlier. What page gave you that stuff about G-force Gandalf61? ~ R.T.G 16:56, 23 June 2009 (UTC)[reply]
It's here. Gandalf61 (talk) 19:15, 23 June 2009 (UTC)[reply]

We should probably link to this toy car that can drive across a smooth ceiling. It's surprising how little it takes to make that work! SteveBaker (talk) 18:20, 23 June 2009 (UTC)[reply]

For one, your fuel gauge will not work properly. I will probably read a full tank no matter what your actual fuel level is. Granted this is probably not critical, short term. 65.121.141.34 (talk) 18:24, 23 June 2009 (UTC)[reply]

Hmmm - tricky. On the one hand, while you are driving at 180mph along the ceiling, you'll probably have more on your mind than what the gas gauge is reading...and on the other hand, if you do happen to run out of gas while driving at 180mph across the ceiling, it may be a bigger concern than if you were more normally positioned at the time! :-) SteveBaker (talk) 23:58, 23 June 2009 (UTC)[reply]

yawning + tone

I recently noticed that I could perceive a very small lowering in tone through headphones during a yawn (i.e., while my mouth is gaping open, and my jaw is extended). Could there be some reason for this, or am I just imagining it? I have tried this a handful of times. 124.154.253.146 (talk) 06:26, 23 June 2009 (UTC)[reply]

I've noticed something similar, so it's not just you. DISCLAIMER: I am not a proffessional. What follows is a guess. My guess would be that somehow the act of yawning makes the muscles flex in such a way that they push against the inner ears slightly. That wold account for a change in pitch.Drew Smith What I've done 08:53, 23 June 2009 (UTC)[reply]

Structural diagram of the cochlea showing how fluid pushed in at the oval window moves, deflects the cochlear partition, and bulges back out at the round window.

I know exactly what you mean - but I very much doubt that it's shifting the pitch of the note. What I suspect is happening is that by changing the shape of the ear canal, you're causing the higher frequencies within the music to be filtered out - or attenuated in some manner - resulting in only the lower frequencies getting through unmolested. So if you had two simple sine-waves being played at different frequencies - then as you yawn, the higher frequency note would get a lot quieter - and you might percieve that as a lowering in frequency - when in fact the lower frequency note is unchanged. SteveBaker (talk) 12:58, 23 June 2009 (UTC)[reply]

Provoke a yawn (I do it by thinking of cricket but that's just me) while intoning a steady aaaaaaaahhh. You may hear the tone change as the size of the resonant cavity of the mouth changes. Cuddlyable3 (talk) 13:54, 23 June 2009 (UTC)[reply]
Sounds are detected by hair cells that line the cochlea, a spiral-shaped structure that is thick at one end and thin at the other. Each frequency causes a different part of the cochlea to vibrate, by resonance. The sensory cells are not directly frequency-sensitive, they only know that the part of the cochlea where they are located is vibrating. My guess is that when you yawn, you either stretch or compress the cochlea, and then a given sound causes the vibration peak to move to a slightly different location. Looie496 (talk) 16:12, 23 June 2009 (UTC)[reply]

Another possiblity (or likelyhood, even) is that during the yawn, you activate the second smallest muscle in your body, tensor tympani which moves the malleus away from your tympanic membrane. This also happens when you are exposed to a really loud noise or chewing. (The smallest muscle, stapedius is also in the middle ear). -- Flyguy649 ^talk 18:09, 23 June 2009 (UTC)[reply]

Thanks! That sounds likely (the part about the missing high frequencies and moving vibration peak), moreso because there's a very obvious reduction in volume. Sorry for making everyone yawn! 124.154.253.146 (talk) 05:41, 24 June 2009 (UTC)[reply]

office temperature requirements.

≈≈≈≈ Wanting to know the legal temperature that a working office should be, Anyone know? ≈≈≈≈

As long as it's not at a dangerous temperature I don't think there are any requirements... Whats the background for the question? Context is always good.Drew Smith What I've done 08:49, 23 June 2009 (UTC)[reply]

More important, you're asking about the laws where? What country, state, etc.? Also, this isn't a science question. I suggest starting over and asking on the Miscellaneous desk, giving more detail this time. --Anonymous, 09:07 UTC, June 23, 2009.

Thanks for the reply, Its in the UK. I work in an office where there are several air con units in our room, there is one directly above our part of the office and this constantly breathes down our neck all day long, leaving us with stiff necks and several other ailments, Its just not very pleasant, and maintence insist on switching it back on when we switch it off. I have research it and see that a room should ideally be between 22.7 - 24.4 C but can not find if there is a legal requirement.

According to "Workplace (Health, Safety & Welfare) Regulations 1992" applicable in the UK, the temperature is only required to be 'reasonable'. There is an additional requirement that employers should provide thermometers to indicate the working-place temperature. Richard Avery (talk) 09:36, 23 June 2009 (UTC)[reply]

The OP's stiff neck and other ailments, and their likely cause, would need to be diagnosed formally by a doctor if one wants the annoyance to be taken seriously. Wikipedia cannot do that. Before seeking a legal remedy it would be diplomatic to suggest to a superior that making a change to the workplace could increase productivity. Cuddlyable3 (talk) 13:48, 23 June 2009 (UTC)[reply]

I actually read recently somewhere that policy on my campus states that temperatures should not exceed 90F, but that's pretty hot and hard to achieve, and that's policy, not law. I don't think it reaches that when the AC's broken in the summer, so you probably won't have much luck arguing this case. --Wirbelwindヴィルヴェルヴィント (talk) 17:25, 23 June 2009 (UTC)[reply]

Really, your manager should care about this and find a solution. I don't think you need to reach for "ailments" — any manager should find a solution for an employee that's actually physically uncomfortable at work. What does your manager say? Tempshill (talk) 17:57, 23 June 2009 (UTC)[reply]

The manager's concern will be based on how many people are in the "our" group the questioner mentions. If it is one person, there is not much need for concern. If it is 20 people, concern rises. -- kainaw ™ 18:01, 23 June 2009 (UTC)[reply]

To answer the original question, the 1992 Regulations state that the minimum temperature for an office (strictly speaking, a workplace where the work is not manual) is 16 °C. You can even buy thermometers with this temperature specially marked. Unfortunately, this legislation was not written with air-con in mind. You can have an air-conditioned room in which the temperature oscillates wildly, causing great discomfort, while the average temperature is still correctly maintained. It is difficult to explain this to your boss, because all bosses are chosen from a genetic subgroup with thick hides. --Heron (talk) 21:03, 23 June 2009 (UTC)[reply]

Probably switching off that A/C would make the rest of the office unbearably warm. Did you check this before you repeatedly(I assume) turned off the A/C? APL (talk) 21:15, 23 June 2009 (UTC)[reply]

The manager agrees that it is too cold in the office and it is her who switches the A/C to a higher temperature (not warm air)/off but it is maintenance who come and turn it back on/the temperature back down. It's the whole office who agree that the temperature in the room is to low.

This is something I looked at a few years ago in connection with trying to show that people worked better at a comfortable temperature. But in fact there was very little about this and the bit I did find seemed to indicate you got more work out of people when it was slightly cooler than the recommended temperatures. Dmcq (talk) 09:50, 24 June 2009 (UTC)[reply]

Perhaps leave a note on the A/C asking maintenance to not reduce the temperature? Could just be a communication issue. 65.121.141.34 (talk) 13:20, 24 June 2009 (UTC)[reply]

In Essence is a Polar Shift of Magnetic poles - capable of being caused by Man through a Ultra-low Resonant Frequency?

I was fiddling with some science stuff and was thinking – if an ultra low frequency were directed to the mantle or core of the Earth, would it be possible for a non-geographical but a shift in magnetic poles? Now, I'm new to this field, so lamen's terms or explanations would be much appreciated.

Before I start doing any digging, is there any hint of evidence at all to this? Have we demonstrated that small magnets can have their polarities reversed through such means? In particular, a frequency of what? Does it need to be resonant (you left that out of the question proper)? Because otherwise it looks like some terms have been slapped together arbitrarily. — Lomn 12:12, 23 June 2009 (UTC)[reply]

This article points both to convection of molten iron in the Earth's outer liquid core driven by internal heat sources and to the magnetosphere driven by solar wind as responsible for the direction of the Earth's magnetic field. Considering the size of these forces may give pause to the OP's thoughts of changing it by shaking it. But who can say what might be possible when Dynamo theory quotes Albert Einstein who described the origin of the Earth's magnetic field as being one of the great unsolved problems facing modern physicists. Cuddlyable3 (talk) 13:34, 23 June 2009 (UTC)[reply]

Soft drink and obesity

Soft drink does not contain fat. Then how it causes obesity? DavidCop (talk) 12:38, 23 June 2009 (UTC)[reply]

Soft drinks are rife with calories (in this case, sugar), and the body typically converts unused calories to fat. — Lomn 12:46, 23 June 2009 (UTC)[reply]

(ec) Eating fat isn't what makes you fat. The body will convert any excess calories into fat. Soft drinks are high in sugar, that's where the calories come from. Eating lots of fat is bad for you because it damages your arteries (if memory serves, I can't find the relevant Wikipedia article, although I'm sure one exists), not because it makes you fat (although it will if you eat enough of it, of course). --Tango (talk) 12:47, 23 June 2009 (UTC)[reply]

(ec²) I read a British medical study a few years ago (it was probably a few years old when I read it) that found a correlation between drinking soft drinks (both regular and diet drinks) and obesity. It is a correlation, not a cause and effect. The lifestyle of drinking soft drinks is a lifestyle that includes increased caloric consumption and decreased exercise. So, you shouldn't use the phrase "causes obesity". -- kainaw ™ 12:50, 23 June 2009 (UTC)[reply]

Just thought to include a couple anecdotes: Mountain Dew is running an ad campaign now that it "fuels" gaming (especially World of Warcraft). Do you really need 220 calories to sit in a chair and play a video game. Also, if you've ever worked in a fast-food restaurant, you've taken the order: Two cheeseburgers with extra fat sauce, super-large fries, two apple pies, cookies, and a large diet Coke. -- kainaw ™ 12:54, 23 June 2009 (UTC)[reply]
Dude, it's the taste, not the diet-ness.... Tempshill (talk) 18:02, 23 June 2009 (UTC)[reply]
I've never understood people that like the taste of diet coke, it tastes far worse in my opinion... --Tango (talk) 18:56, 23 June 2009 (UTC) [reply]
Fun fact : Diet Coke uses the Coke II formula, not the Coca-Cola formula. APL (talk) 21:05, 23 June 2009 (UTC)[reply]
I'm in the UK. I don't think we've ever had anything with the Coke II formula. Our article doesn't seem to support your claim (although it makes some incomprehensible comments about diet coke, do you have a source? --Tango (talk) 22:45, 23 June 2009 (UTC)[reply]
Diet Coke was introduced first. Coke II was the diet coke formula with real sweetener. This statement appears unsourced in our Diet Coke article and it appears on snopes. I have read it other places as well, but that's all I feel like digging up at the moment. Perhaps the references at the snopes article can help. The Coke II article is a mess regardless. APL (talk) 23:33, 23 June 2009 (UTC)[reply]

If the definition of "large" in the fast-food restaurant in question is what it is in some, then that could still be a significant reduction in the total calories in the meal. --Tango (talk) 15:15, 23 June 2009 (UTC)[reply]

It should be noted that calories are a measurement of energy, thus aren't actually converted to fat. However soft drinks contain saccharides that can be converted to triglycerides, which are stored in adipocytes (which make up adipose tissue - colloquially known as fat). --Mark PEA (talk) 15:05, 23 June 2009 (UTC)[reply]
Indeed, I apologise for my imprecise language. My point was that it is the number of calories you consume that is significant, not where they come from. (Well, it's a little more complicated due to the body absorbing calories better in some forms than others, but it's a decent approximation to the truth, at least.) --Tango (talk) 15:15, 23 June 2009 (UTC)[reply]

In other words, gaining/losing weight does not need to be overly complicated. If you consume significantly more calories than your burn, you will likely gain weight. If you consume significantly less calories than you burn, you will likely lose weight. Yes, it is a lot more complicated if you want to make it an exact science, but the average person doesn't care about the exact amount of fat gain per calorie consumed. -- kainaw ™ 17:36, 23 June 2009 (UTC)[reply]

Toe-nails

I remember learning long ago (and, common sense confirms) that all of the parts of the human body serve some physical or biological function / purpose. The only part, I was told, that did not seem to fit into this model was the appendix. For years, scientists assumed it served no purpose whatsoever (at least, today ... as opposed to millions of years ago). (As a side note, I guess that modern science is now questioning this idea and has theorized on some functions that the appendix serves.) Anyway ... on to my question. I was thinking about the finger-nail, and I was puzzled about its function. After some thought, I was able to convince myself of a few things ... for example, peeling, plucking, pulling, grabbing, holding, scratching, and the like. Then, my thoughts turned to the toe-nail. I cannot for the life of me think of any purposes whatsoever that they serve. The only thing that I can (half-heartedly) think of ... is that they serve as an outer shell to "protect" the surface of the toe. But, that is hardly convincing to me. Does the toe-nail serve any function at all? Or am I missing something very obvious? I am referring to human beings, by the way. Thanks. (Joseph A. Spadaro (talk) 14:01, 23 June 2009 (UTC))[reply]

From our article, Nails act as a counterforce when the end of the finger touches an object, thereby enhancing the sensitivity of the fingertip, even though there are no nerve endings in the nail itself. Could the same apply to toes? Vimescarrot (talk) 14:35, 23 June 2009 (UTC)[reply]
It is also possible that our feet evolved from fully articulate appendages (like hands) and toe nail is just a hold over from that time. Livewireo (talk) 15:07, 23 June 2009 (UTC)[reply]
Toenails also give a small amount of protection to the end of the toes. Might not be much, but better then nothing. 65.121.141.34 (talk) 15:08, 23 June 2009 (UTC)[reply]
The human toenails are relics of claws that once were useful for climbing and fighting. Now that the foot is optimised for bipedal walking they serve only to slightly stiffen and protect the passive toes (and provide a refuge for fungus). Cuddlyable3 (talk) 15:19, 23 June 2009 (UTC)[reply]

It's not true that every part of the human body serves a purpose. The appendix is pretty useless, for example. Generally, every part served a purpose at some point in our evolutionary history (although there is no absolute requirement for that to be the case, things can just happen coincidentally), but it's not uncommon for that purpose to no longer be relevant. --Tango (talk) 15:21, 23 June 2009 (UTC)[reply]
See Vestigiality for details. --Tango (talk) 15:23, 23 June 2009 (UTC)[reply]

Questions of the form "Why is (some biological detail) there?" presume an intelligent plan rather than random evolution. A debate about who designed the human body went like this: It was designed by a mechanical engineer, for only he could have made all the wonderful joints. No, says another, it was designed by an electrical engineer for only he could have designed the complex wiring of the nervous system. No, says another, it was designed by a civil engineer, and a bad one at that, because no good civil engineer would lay a sewer pipe through an entertainment district. Cuddlyable3 (talk) 19:26, 23 June 2009 (UTC) [reply]
I think toenails would go the way of the Dodo bird if they didn't serve some purpose. Bus stop (talk) 19:46, 23 June 2009 (UTC) Bus stop (talk) 19:46, 23 June 2009 (UTC)[reply]
They may be, but this kind of stuff doesnt happen over night. The appendix stopped being relevant thousands of years ago and a vestigal tail is still observable in a fetus. Check back in about 10,000 years, our feet may be toe-nail free. Livewireo (talk) 20:42, 23 June 2009 (UTC)[reply]

Thousand of years? really? Dauto (talk) 22:26, 23 June 2009 (UTC)[reply]
Yes, really. Well, I don't think there is universal agreement, but it's certainly a popular theory that the appendix become pretty much useless when we changed to our modern diet, which happened maybe a few tens of thousands of years ago. --Tango (talk) 22:41, 23 June 2009 (UTC)[reply]
I'm not sure I buy that. By modern diet, do you mean cooked food? 71.203.58.148 (talk) 04:08, 24 June 2009 (UTC)[reply]
Not necessarily. It might be since the invention of agriculture. Control of fire goes back much further than that. I'm really not an expert on the function of the appendix! --Tango (talk) 13:22, 24 June 2009 (UTC)[reply]

They do serve a cosmetic purpose. Would you marry someone without toenails? A toe looks better with a toenail. Many features on humans make them more attractive, and so will tend to be retained across generations. Graeme Bartlett (talk) 22:33, 23 June 2009 (UTC)[reply]
You only think they are attractive because the lack of a toenail suggests something is wrong and something being wrong means the person won't make a good mate. --Tango (talk) 22:41, 23 June 2009 (UTC)[reply]

The thing about this evolutionary stuff is that it's not enough for something to be functionally useless for evolution to dispose of it. It has to materially REDUCE the ability of the creature to survive and reproduce...that's the only way that possessors of the "no toenails" gene can take over the world from the "with useless toenails" people. We do find that (for example) almost all animals that live in dark caves eventually evolve to lose their eyesight - but eyesight is an expensive thing to maintain - it's not just the eyeballs, it's muscles, eyelids, brain function. Without eyes, they need less energy - needing less energy, they can survive better. But I don't think toenails - which are dead material and grow at glacial rates need much energy. They simply aren't a disadvantage...so they won't get selected against. Toenails have been useless pretty much since we descended from the trees - we've had PLENTY of time to lose them - yet they are still here.

Another possibility - and a quite likely one IMHO - is that the exact same gene controls toenail and fingernail growth. Fingernails are incredibly useful. Perhaps we simply cannot lose our toenails without also losing fingernails - and thereby suffer such horrific disadvantages that the "no nails anywhere" gene is selected out whenever it pops up.

SteveBaker (talk) 01:30, 24 June 2009 (UTC)[reply]

Related question - are there any animals with toes but no toe nails? Jay (talk) 10:15, 24 June 2009 (UTC)[reply]

Alright people, you're missing it completely. Toe-nails keep the bones in your toes from breaking through the skin. The ends of the bones in your fingers and toes are sharp, and if you didn't have nails the skin around these sharp bones would be very prone to movement. The movement would, over time, wear the skin down and eventually tear. Thus, humans evolved fingernails and toenails.Drew Smith What I've done 04:35, 24 June 2009 (UTC)[reply]
Do you have a source for that? Vimescarrot (talk) 10:02, 24 June 2009 (UTC)[reply]
I'm glad I've got cheek-nails - to keep my cheeks from moving near my sharp teeth. Otherwise my teeth would obviously be sticking out the side of my head --Polysylabic Pseudonym (talk) 13:01, 24 June 2009 (UTC)[reply]

Toe nails can be trained to do what finger nails can. Mark Goffeney and Tony Meléndez might be using them to play the guitar, and Bill Wedekind might be using it for pottery. Jay (talk) 11:39, 24 June 2009 (UTC)[reply]

I'd like to point out that our article on the appendix has links to references that the appendix is not totally vestigial, but may contribute both to the immune system and to sustaining gut flora. Considering the high incidence (and mortality!) of appendicitis and peritonitis, it's hardly surprising that natural selection would otherwise allow it to remain. The comparison to toenails is not valid (especially since ingrown toenails rarely kill you...). Matt Deres (talk) 16:28, 24 June 2009 (UTC)[reply]

Maybe toenails are nature's first steel-toe boots. Bus stop (talk) 17:16, 24 June 2009 (UTC)[reply]

Something that occurred to me is that in addition to other possible reasons mentioned above, toenails may also serve as an honest signal of the health of an individual, since nails can present a recent health history to prospective mates. JSBillings 01:37, 25 June 2009 (UTC)[reply]

Possibly in a superficial way, but not as a reliable indicator. Many people have serious illnesses and perfect toenails, while I am perfectly healthy and have a disgusting looking ingrown toe-nail (that needs another surgery, I might add).Drew Smith What I've done 06:34, 25 June 2009 (UTC)[reply]

Landing on the Moon

It seems like landing on the Moon is an insanely complicated process (ie no atmosphere to slow you down). In the future if civilians were able to fly there via a commercial flight would there be a safer method of ensuring you don't plummet into the ground at 14 km/s? TheFutureAwaits (talk) 16:23, 23 June 2009 (UTC)[reply]

A space elevator is an option, I believe. (If memory serves, it wouldn't need to be as strong as one on Earth, but would need to be much longer - I'll look that up in a moment.) Several redundancies in your propulsion system would reduce the risk substantially, as it does on airliners today. I guess you could design a landing pad that in some way cushions the impact, either directly with lots of springs or something, or by slowing the descent of the landing craft before it makes contact via big magnets or something. I don't know of any serious proposal along those lines and I'm not sure it is necessary. --Tango (talk) 16:30, 23 June 2009 (UTC)[reply]
My memory would appear to be accurate. We have an article on the topic (of course!): Lunar space elevator. --Tango (talk) 16:33, 23 June 2009 (UTC)[reply]

Hmm according to the article that's not the best option: "One disadvantage of the lunar elevator is that it may not be able to carry human passengers. The rate at which cargo is transferred would be too slow, normally taking weeks to reach its destination.[2] Humans would be able to get there faster by using rockets to and from the moon." I'm wondering if there's some method by which you could make powered landings safer. On the Earth the atmosphere slows you down as you lose altitude but on the Moon you GAIN speed. TheFutureAwaits (talk) 16:52, 23 June 2009 (UTC)[reply]

One of the entries into the Google Lunar X Prize was for producing a rocket that could fly (50 or 100 meters) into the air, fly sideways for another specific distance, and land gently in a small moon landscape replica. Only one (on this particular occaision) managed it but it was really careful. I doubt, IMO, it was going over 14 miles per hour at touchdown (was it?). ~ R.T.G 16:53, 23 June 2009 (UTC)[reply]
The OP said 14 kilometres per second. (Although I'm not sure why - the Moon's escape velocity is only 2.38 km/s so that's the fastest you could hit unless you actually thrust in the wrong direction.) You need to be careful interpreting the results from the Lunar X Prize - it took place on Earth, so everything was scaled to compensate for the higher gravity. You may need to multiply the landing speed by 6 or something to get the lunar equivalent, I'm not sure. --Tango (talk) 17:46, 23 June 2009 (UTC)[reply]
The Lunar X prize stuff doesn't relate to landing from orbit - it's only about hopping around on the lunar surface. SteveBaker (talk) 18:11, 23 June 2009 (UTC)[reply]

As I said, redundancies in your propulsion system is probably all you need. If you have more descent engines than you strictly need you can afford for one of them to fail. Add some redundancies to the control system as well, and you should have a pretty safe lander. Airbags could be deployed in an emergency (I don't think they would be very good for routine landings, they would make getting out afterwards a little tricky). You could eject in little capsules with airbags, perhaps? --Tango (talk) 17:46, 23 June 2009 (UTC)[reply]

Just as a note, it's not clear that the lack of atmosphere makes lunar landings more complicated. An unpowered craft has no option to glide, true. On the other hand, there's no issue with heat of re-entry, there are no crosswinds, there's no need for a minimum safe flying speed, there's no need for designs that emphasize aerodynamics over capacity, and so forth. As noted above, you'd want redundancies in your critical systems, but that's a requirement for conventional aviation already -- much less the sort of safeguards that are required for spaceflight. I expect the safety considerations for commercial lunar travel will strongly resemble, in principle, the same considerations the airline industry uses today. — Lomn 17:54, 23 June 2009 (UTC)[reply]
Generating 1/6th of a g for the sustained amounts of time you need to land isn't really challenging - look at the tiny engines that got the apollo moon landers from the lunar surface back up into orbit. The majority of the mass of the system will be fuel - so having multiple rocket motors for redundancy is the obvious way to go. I also don't agree with the OP that the landing process is insanely complicated. Rockets are relatively unsophisticated machines - there isn't a whole lot to go wrong compared to (say) the engines on a 747. The problem with apollo was that every pound that had to be launched from the moon back to the earth had to be launched in one single craft in the opposite direction first. For sustained lunar colonies, a much better approach is to do what they did in the 2001 movie - which is to have separate craft for getting you out of the earth's gravity well that can concentrate on one really huge explosive push...versus the more sustained, but gentle push you need to get down onto the moon. SteveBaker (talk) 18:11, 23 June 2009 (UTC)[reply]
Just to make it clear, NASA is moving strongly in the direction of 2001. The Constellation program divides up cargo launch, crew launch, trans-lunar injection, and lunar landers as more-or-less independent systems. The problem (and discrepancy from 2001) is that reuse is minimal. Unfortunately, this will be a hard problem to crack. In order to re-use a special-purpose lunar craft (say, the one for Earth/Moon orbital transfers), you have to re-fuel it. Until there's a viable space-based fuel supply, the only option to re-fuel is to launch fuel from Earth. As Steve notes above, this is inefficient. However, it's comparatively cheap to launch a rocket engine along with that fuel supply. Rather than design a refueling system with all the additional risk it entails, we opt to launch the entire set of hardware repeatedly. — Lomn 18:48, 23 June 2009 (UTC)[reply]
Any permanent lunar colony should have its own fuel supply. All the plans I've seen involve finding somewhere with plenty of water ice that can be split into hydrogen and oxygen (a.k.a. rocket fuel) using solar power. --Tango (talk) 18:52, 23 June 2009 (UTC)[reply]
Indeed - the moon is a tricky problem. If indeed there is water ice in sizeable deposits in deep polar craters (where they would always be shaded from the sun and water from cometary debris could collect over billions of years) - then it makes sense to go there. With ample water and sunlight, we can make oxygen, drink the water, grow food and make rocket fuel and hopefully have electricity to spare. A long-term base would be able to figure out what other stuff could be extracted from the lunar soil - with the hope that metals could be extracted and solar panels mass-produced. If the amount of water there is large enough, this could be a very useful thing. But if there is little or no water there - then going to the moon is always going to be a hideously difficult and expensive proposition. The only reason to go there then is if there is something amazingly valuable there. There is a possibility that certain rare helium isotopes are to be found there in large quantities that would make building fusion reactors a much more reasonable proposition - so mining helium and shipping it back to earth would be a profitable reason to go there - despite the insane costs involved. But bootstrapping ourselves up to the point where we could have massive earthmoving and refining facilities there is an exceedingly difficult thing...I doubt we'll ever do that. SteveBaker (talk) 23:51, 23 June 2009 (UTC)[reply]
I think recent missions have confirmed the presence of significant amounts of water ice on the moon, although I don't know if they've confirmed it is accessible. He-3 is only useful if someone figures out how to make a fusion reactor that produces more energy than it uses - I'm optimistic, but there isn't really any reason to believe we'll get that worked out any time soon. The far side of the moon is a good spot for radio astronomy, although I'm not sure that will justify a manned mission (a space telescope at Earth-Moon L2 would work pretty well, by my calculations) it could contribute towards justifying one. If there is plenty of accessible water then it could work well as a waystation to the rest of the solar system (you only need to launch the fuel from the Moon, not the Earth). --Tango (talk) 01:46, 24 June 2009 (UTC)[reply]

Venus Flytrap care

I recently purchased a Venus Flytrap. It is a really fascinating plant and so far it has trapped a couple of flies. I have done some research on these plants, however,my question is for anyone who has experience in caring for flytraps...specifically, how much food do they need? Is it possible for them to eat too much? I have actually fed it a housefly which it eagerly trapped, but I am wondering if that is a habit I should avoid. thanks and cheers, 10draftsdeep (talk) 20:24, 23 June 2009 (UTC)[reply]

Overfeeding can be harmful for VFTs although how much that is will depend on the size of the plant, though the article says that digestion takes about 10 days to complete. You actually don't really need to feed it at all as it is still a plant and will photosynthesize for almost all of its needs. I assume you have already read the article we have? 65.121.141.34 (talk) 20:52, 23 June 2009 (UTC)[reply]
Photosynthesis is how the plant get's its calories. The traps are to supplement the nutrients brought up by the roots. VFTs do well in poor soil because they're not dependent on the soil to provide nutrients. APL (talk) 20:54, 23 June 2009 (UTC)[reply]

Warning : Anecdotal evidence follows

I've owned a flytrap for several years. After several failed attempts to keep one alive, I started watering this one only with distilled water. It's been alive for about six or seven years now.They're supposedly very sodium sensitive, so I recommend it if you're in an area that has too much salt in the water supply.

Otherwise, it is possible to overfeed them. Each trap can only close an average of two to four times before the entire leaf dies. (Smaller traps seem to be able to survive more closings than larger ones.) So "teasing" the plant just to watch it move is absolutely not advised. If you kill off all the leaves at the same time, either from over-feeding, or "teasing" or whatever then it will have a difficult time recovering.

They can survive just fine with no bugs at all, but I've found that a few bugs a month seems to make them grow faster.

Many people say that you need to hibernate them in the winter, by placing them in a fridge. I've never bothered. I just keep mine on the windowsill, it dies back a little in the winter but never completely. (Some people do report that their VFT dies off entirely in the winter, but still recovers in the spring. So if your plant goes brown around October, don't throw it out until at least June.) APL (talk) 20:54, 23 June 2009 (UTC)[reply]

It takes them roughly ten days to digest, however they will not need to be fed "meat" for another week after they are done digesting. They are very sensitive to sodium (as APL said) and potassium. Again, photosynthesis gives the plant most of it's calories. Do not, however, "hibrernate" your VFT. They are tropical plants, and in the wild they don't experience much of a "winter".Drew Smith What I've done 04:29, 24 June 2009 (UTC)[reply]

Ahem. Tropical?? This looks rather like the Carolinas (US) to me (native habitat in red) and we do get winter there.71.236.26.74 (talk) 06:59, 24 June 2009 (UTC)[reply]
VFT is native to tropical and sub tropical rainforests. You're pic is inaccurate.Drew Smith What I've done 08:08, 24 June 2009 (UTC)[reply]

The VFT article states that "Although it has been successfully transplanted and grown in many locales around the world, it is found natively only in North and South Carolina in the United States, specifically within a 60 mile radius of Wilmington, North Carolina" (and uses a similar map to show distribution). Is this totally wrong, then? --Kurt Shaped Box (talk) 10:25, 24 June 2009 (UTC)[reply]
Yeah, according to Insectivorous plants‎ by Charles Darwin, VFT is native to south american tropical rainforests. As far as I can tell, Home Depot invented the whole "native to the carolinas" thing to sell more VFT's in the states.Drew Smith What I've done 11:54, 24 June 2009 (UTC)[reply]
Oh dear. If you're correct on that (and I have no reason to doubt you), then that false claim has been present in some form in the article since 2003!... --Kurt Shaped Box (talk) 11:59, 24 June 2009 (UTC)[reply]

It also appears to be all over the web now! --Kurt Shaped Box (talk) 12:12, 24 June 2009 (UTC)[reply]

Do you have a more recent source to that effect?

Personally, I would be very surprised if VFTs evolved somewhere without seasonal variation. APL (talk) 13:04, 24 June 2009 (UTC)[reply]

(outdent.) Oh good. I was right. Thank goodness. I hate being wrong.

From "Insectivorous Plants" by Charles Darwin.

Chapter XIII : DIONAEA MUSCIPULA.

(Emphasis Mine.)

"THIS plant, commonly called Venus' fly-trap, from the rapidity and force of its movements, is one of the most wonderful in the world.* It is a member of the small family of the Droseraceae, and is found only in the eastern part of North Carolina, growing in damp situations. The roots are small; those of a moderately fine plant which I examined consisted of two branches about 1 inch in length, springing from a bulbous enlargement. They probably serve, as in the case of Drosera, solely for the absorption of water; for a gardener, who has been very successful in the cultivation of this plant, grows it, like an epiphytic orchid, in well-drained damp moss without any soil. The form of the bilobed leaf, with its foliaceous footstalk, is shown in the accompanying drawing (fig. 12)."

Frankly, I'm ashamed of Charles Darwin for being suckered by Home Depot's conspiracy to sell more potted plants. :-) APL (talk) 13:10, 24 June 2009 (UTC)[reply]

Very odd. My copy clearly has "south american tropical rainforests" where your's has "eastern part of North Carolina". I can upload a picture of it if anyone really wants to see it. I have no doubt that my copy is defective, but I believed it for the longest time...Drew Smith What I've done 13:23, 24 June 2009 (UTC)[reply]

Could it be that your copy is a later edition (or an earlier one)? --Kurt Shaped Box (talk) 13:33, 24 June 2009 (UTC)[reply]
I have no idea. It's a few years overdue from the library in Maryland, and has no edition number, and the copyright page is either non existant, or ripped out before I got it...Drew Smith What I've done 13:55, 24 June 2009 (UTC)[reply]

To see venus fly traps in action, go to http://video.google.com/videoplay?docid=2802047796785763024
GlowWorm.

File:Insectivorous Plants Drew's copy.jpg

Drew, could you upload an image of your text passage? This would be a rather odd "error" in a book, and seems intentionally inserted, by whoever printed it. And I'm really astounded for what reason anyone should insert such a factual error in a copy of Darwin's text. --TheMaster17 (talk) 15:07, 24 June 2009 (UTC)[reply]

You'll probably have to open the file to be able to read anything, but there it is.Drew Smith What I've done 15:52, 24 June 2009 (UTC)[reply]

Googling for the phrase "and is found only in the eastern part of North Carolina, growing in damp situations" brings up this link "Insectivorous Plants" by Charles Darwin - so this is obviously not uncommon. Weird! SteveBaker (talk) 18:18, 24 June 2009 (UTC)[reply]

The copy in Project Gutenberg also says North Carolina. SteveBaker (talk) 18:29, 24 June 2009 (UTC)[reply]

I'm no expert, but I would bet money that the "North Carolina" version is more accurate to reality, regardless of whichever Darwin actually wrote. VFTs respond too well to seasonal variation to have evolved in a rain forest.

My theory is that Darwin was working from a sample sent to him from some other naturalist and somehow got confused about where it came from, then he corrected it in subsequent printings of his book.

My theory doesn't completely explain Drew's book, however. Does he unknowingly have a rare first edition? Or did some subsequent reprinting use the original un-corrected manuscript? APL (talk) 19:12, 24 June 2009 (UTC)[reply]
Interesting. A google search for Drew's version turns up nothing at all. I was hoping it would at least turn up somewhere discussing revisions to the book. APL (talk) 19:26, 24 June 2009 (UTC)[reply]

Interesting. This is something that someone in the know about VFTs (do we have any certified carnivorous plant experts here?) should probably look into. I wouldn't discount the possibility that the version you have may be the 'corrected' one. I think I'll ask over at Wikipedia:WikiProject Carnivorous plants. --Kurt Shaped Box (talk) 16:31, 24 June 2009 (UTC)[reply]

Anyone got a first edition at home to solve this one once and for all? 65.121.141.34 (talk) 18:52, 24 June 2009 (UTC)[reply]
Who would have thought that my hungry little plant would result in an investigation of Mr. Darwin? :-) Also, thanks for the responses. cheers, 10draftsdeep (talk) 20:00, 24 June 2009 (UTC)[reply]

Hi, all. I'm responding here from the note at WT:CPS. The copy of Drew's book is certainly in error. The only native populations of Dionaea are in North Carolina. There are also some naturalized populations in the Florida panhandle that come from seed spread there intentionally. I have no idea where Drew's copy comes from; is there a title page at all? Anything to indicate what edition, reprinting, etc. this would be? The correct sentence states North Carolina: 1875 London version (large pdf, page 301 of the pdf), 1875 New York version (large pdf, page 303 of the pdf), the 1888 London version that was revised by Francis Darwin (image, not a large file), and even the 1876 German version (image link). I'd like to know more about Drew's book, where it came from, when it was written, but I doubt we'll ever know why this phrase was changed. I'm exceedingly interested, though. Historical fraud? An attempt at humor? Who knows... Thanks for giving WP:CPS a heads up on this one. Interesting... Rkitko ^(talk) 21:16, 24 June 2009 (UTC)[reply]

I also note that Drew's book appears to be hand typeset, and the typesetting is different (longer length of each line) than any of the editions of Insectivorous Plants that I've ever seen. It may have been an unauthorized reproduction? --Rkitko ^(talk) 21:25, 24 June 2009 (UTC)[reply]

As I said before, it's a few years overdue back to a library in maryland, is missing the copyright page (or never had one), and mentions no edition number. I can't find anything that mentions when it was printed, though I must note that the pages are already much older than my 1960's copy of boxcar children, so it's at least 50ish years old...Drew Smith What I've done 05:34, 25 June 2009 (UTC)[reply]

Height and Growth

What behaviorial and environmental factors affect a person's height during growth? What is the relationship between sleep and growth? Deltawk (talk) 21:37, 23 June 2009 (UTC)[reply]

Check out Human_height#Determinants_of_growth_and_height. --Tango (talk) 22:35, 23 June 2009 (UTC)[reply]

What is the mechanism for air leaking from car tyres?

My wife and I have almost identical cars - bought new on the same day from the same car dealership. They both have run-flat tyres with tyre pressure monitoring and they are both about 4 months old.
Yesterday, the low pressure tyre pressure warning light tripped on my wife's car - and it turned out that three out of four tyres were quite low on air...so she pumped them up and reset the tyre monitor and everything seems OK today. Except that, this morning, my car showed a low pressure warning - and all four of my tyres were down to around 20psi (they are supposed to be 33psi).
The thing is that while the two cars are of identical age and near-identical type - they are driven totally differently. I push mine quite hard - my wife is doing a great "little old lady" impersonation. I drive 40 miles a day - she probably does more like 10 - although we both take 360 mile road-trips every few weekends in order to visit my son - so my milage is about twice hers.
So is the rate of air leakage merely dependent on things that these cars have in common - which would make this be an entirely expected thing? Or should I be concerned that some annoying person is letting the air out of our tyres? (Neither car is garaged right now).
What is the mechanism that allows the air to escape? I'd kinda imagined that hard cornering might affect the seal between tyre and wheel...but with one car flung into corners with extreme enthusiasm and the other driven very gently indeed - that doesn't seem to be the case.
Any ideas? SteveBaker (talk) 23:27, 23 June 2009 (UTC)[reply]

I believe that for tires in good condition the mechanism for air loss is essentially the same as the reason that balloons go flat: air diffuses through the rubber over time. Tires, being much thicker and more durable than balloons taks months to go flat as opposed to days for the typical party balloon, but I would guess the same principle applies. Of course, old and abused tires may have actual cracks in the rubber which could significantly accelerate the process. Dragons flight (talk) 00:01, 24 June 2009 (UTC)[reply]
That certainly fits that both cars lost pressure at almost identical rates...these are practically new tyres and they're "run-flat" so they have super-thick side-walls in order to support the weight of the car as they deflate. SteveBaker (talk) 01:12, 24 June 2009 (UTC)[reply]

Don't dismiss the possibility that it could just be a coincidence. --Tango (talk) 01:36, 24 June 2009 (UTC)[reply]
I certainly wouldn't dismiss coincidence...but the rate of air loss doesn't seem like a particularly random process...so that's not the most obvious explanation. SteveBaker (talk) 14:58, 24 June 2009 (UTC)[reply]
Gradual air loss probably isn't random, but running over nails in the road is. (You would have probably noticed a large puncture, but it could be something fairly small. Have you checked the pressure since pumping them up? --Tango (talk) 16:09, 24 June 2009 (UTC)[reply]
There are no obvious punctures - and the automatic tyre pressure warning system hasn't complained about low pressure - and it's been more than a day. They also didn't go all the way flat - there was about 20psi in each. So I don't think it's a rash of punctures (just as well - those runflats are hard to repair and they cost a small fortune to replace!) SteveBaker (talk) 18:03, 24 June 2009 (UTC)[reply]

In the short term, (i.e. a few years) the tires will wear evenly, and get flat at roughly the same time. As time progresses your tires will take a lot more permanent damage, and by the time the cars are ten years old your tires will deflate significantly faster than hers. It won't be too serious, but it will be annoying.Drew Smith What I've done 04:25, 24 June 2009 (UTC)[reply]

Based on my life experience of about 12 cars and the amount of times I have had air loss from tyres, I think you should think about tampering. The chances of one tyre losing air spontaneously and with careful driving are quite low: the chances of three tires losing pressure at the same time seem to me to be extremely low without some form of deliberate intervention. Richard Avery (talk) 06:28, 24 June 2009 (UTC)[reply]

Tires tend to loose air faster in warm weather. Since you are in Texas and it's summer it's bound to be nice and toasty. Your wife's car and yours are also most likely exposed to the same temperatures. Don't have any source, but IMHO air leakage occurs more through the valve than permeating through the walls. BTW I was surprised how much less often I had to inflate tires in Europe than in the US (south). --71.236.26.74 (talk) 06:43, 24 June 2009 (UTC)[reply]
It's certainly insanely hot right now - we've had a couple of 103 degF days recently. But doesn't the heat cause the air to expand and INCREASE the pressure? SteveBaker (talk) 14:58, 24 June 2009 (UTC)[reply]
Probably yes, but wouldn't this higher pressure lead to even faster diffusion of the air through whatever route it is taking (walls or valve)? As far as I remember my physics training, this should be the case. --TheMaster17 (talk) 15:10, 24 June 2009 (UTC)[reply]

Heat will expand air and increase pressure, which helps the tire lose air more quickly if it is indeed migrating out through the rubber. 65.121.141.34 (talk) 15:08, 24 June 2009 (UTC)[reply]
Well, perhaps - but wouldn't that just put the pressure back to where it usually is (albeit with less air)? We might expect an abrupt drop in pressure when the air temperature drops - but this is summer in Texas...it hardly even cools off at night! SteveBaker (talk) 18:03, 24 June 2009 (UTC)[reply]

But hang on a minute, I thought the original issue was the difference in tyre pressure in the two identical cars. Any external effect might be expected to show the same results on both cars, so if the temperature is thought to be to blame (I can't for the life of me see why. After 7 years living in southern Spain where summers temperature regularly reached 110F I never had a single problem with low tyre pressure) surely both cars should show similar problems. Seems to me we are looking for a cause that affects Steve's car but not his wife's. Or have I got this wrong? Richard Avery (talk) 19:57, 24 June 2009 (UTC)[reply]
I don't think you understood the question. The two cars DO produce identical results - suspiciously identical given how differently they are being driven on a daily basis. If the air loss is only due to weather, rubber composition, age, etc - then I shouldn't be surprised that the low pressure warning systems on the two cars triggered within 24 hours of each other...but I find it hard to believe that driving style/speed/etc and number of miles driven has absolutely zero impact, which makes me suspect that some idiot has been letting air out of our tyres for some stupid reason. SteveBaker (talk) 22:38, 24 June 2009 (UTC)[reply]
Ah, Yes, Always read the question carefully before attempting your answer. Richard Avery (talk) 06:03, 25 June 2009 (UTC)[reply]

(unindent)In my opinion driving styles and miles driven must have an influence: Driving more (and faster) would heat up the tires for a longer time, speeding up diffusion. And I think we all agree that whatever route out the air is taking, diffusion is the mechanism. So Steve, I think you have a malicious neighbor ;-) --TheMaster17 (talk) 08:07, 25 June 2009 (UTC)[reply]

June 24

basements

what building has the most basements?

Well, I don't know for sure - but it's very likely to be one of the tallest buildings - you have to go down deep to anchor the thing - hence lots of basements. SteveBaker (talk) 01:05, 24 June 2009 (UTC)[reply]
Hard to say, but tall does not correlate with deep. The height of buildings in Manhattan is directly related to the availability of Manhattan schist at a conveniently shallow depth. However, Grand Central Station and its associated tracks would be a contender in area, if not in number of levels. Acroterion _(talk) 01:10, 24 June 2009 (UTC)[reply]

The car park under Bloomsbury Square in London goes down seven levels. I'd guess that any building with extensive car parking or mass transit underneath would have a large number of subterranean levels. Acroterion _(talk) 01:41, 24 June 2009 (UTC)[reply]
The Petronas Twin Towers in Kuala Lumpur have the deepest foundations of any building in the world, at 120 metres, with improved ground another 30 to 40 metres below that. The foundation barrettes support the concrete slab which holds the buildings. I cannot find how much of the depth is "basement" in any traditional sense. All attention seems to have gone to the above-ground section of the buildings. - KoolerStill (talk) 02:23, 24 June 2009 (UTC)[reply]
Those foundations are pilings or caissons, neither of which contain (or are able to contain) living space, as they depend on being surrounded by earth for their strength. Acroterion _(talk) 03:57, 24 June 2009 (UTC)[reply]

The winner may turn out to be some building hardened against nuclear attack. Like the Pentagon or Cheyenne Mountain. APL (talk) 02:35, 24 June 2009 (UTC)[reply]
Wouldn't that count more as a bunker rather than a series of basements? - KoolerStill (talk) 03:49, 24 June 2009 (UTC)[reply]

Bunkers tend to be single-level caves mined horizontally into the side of a mountain, as it's easier to haul waste that way and cheaper to stay on one level. Cheyenne Mountain and the MoD facilities at Corsham are examples of this type. The Pentagon doesn't have much of anything under it by all accounts because it's nearly at sea level already. Some of the most extensive basements I've encountered are associated with sports facilities like Madison Square Garden, which need extensive utility space. There's not a lot of point in going down very far under a building with habitable space, as it's hard to get in and out for any useful purpose, as well as dark, wet and expensive. Building codes also discourage it as it's hard to rescue people and fight fires in multi-level underground structures.

Some of the deepest underground spaces, apart from mines, are underground hydroelectric power plants, but they're not usually more than a couple of levels in all, just big cavernous rooms. For mines, see Western Deep Levels. Acroterion _(talk) 03:57, 24 June 2009 (UTC)[reply]
My guess would be some sort of military project, or possibly a lab for extremely hazardous materials. There are unclassified military buildings who's "basements" already go down alot farther than most comercial buildings. The nature of what goes on in those buildings is usually still classified though.Drew Smith What I've done 04:21, 24 June 2009 (UTC)[reply]

Another not-so-classified military option is a missile silo. They go down pretty far. While the central silo has no floors, there are many floors surrounding it. -- kainaw ™ 12:35, 24 June 2009 (UTC)[reply]

The OP asked about basements, and we're just guessing around tallest buildings. It turns out the Petronas Towers have only 4 levels of underground parking, no more than many much smaller buildings.

This is not a basement, but is going to be very deep (and may be the trigger for the question). "Far below the Black Hills of South Dakota, crews are building the world's deepest underground science lab at a depth equivalent to more than six Empire State buildings — a place uniquely suited to scientists' quest for mysterious particles known as dark matter.[32] - KoolerStill (talk) 08:36, 25 June 2009 (UTC)[reply]

Transformer

What is the difference between real & ideal transformer?

It seems to me to be a homework question. Still, I can tell you ideal transformers have their mutual coupling constant, k=1. Practically, its less than 1. Also, there is some core losses as well as leakage associated with a real transformer. 59.93.180.203 (talk) 06:00, 24 June 2009 (UTC)[reply]

Have you looked at the article transformer? Ideal ones don't have a size whereas for instance a real one that was big might have a sign saying 'danger of death' Dmcq (talk) 12:00, 24 June 2009 (UTC)[reply]
A real transformer transfers electrical energy from one circuit to another and an ideal transformer turns from a car in to a giant robot. Livewireo (talk) 13:52, 24 June 2009 (UTC)[reply]

This Image

I got this image: image. It shaws a lightened up road, and the caption says "Luminous traces of a truck convoy in the evening". Can anybody explain that? 59.93.180.203 (talk) 05:57, 24 June 2009 (UTC)[reply]

Yeah. In the evening or at night you need to open your camera shutter for a rather long time, so that enough light hits the film. During that time the trucks move a considerable distance, so each headlight leaves a ribbon of light on the film. That is what you are seeing. Think of it as an extreme case of the motion blur. --Dr Dima (talk) 06:06, 24 June 2009 (UTC)[reply]

And we do have a page for the Motion blur, of course :) --Dr Dima (talk) 06:11, 24 June 2009 (UTC)[reply]
That kind of photography has also been used for stars, with some pretty breath taking results.Drew Smith What I've done 06:27, 24 June 2009 (UTC)[reply]
There are even some star-streaks in the sky on the OP's image. DMacks (talk) 06:53, 24 June 2009 (UTC)[reply]

Thanks, all that pretty much explains this.218.248.80.114 (talk) 07:58, 24 June 2009 (UTC)[reply]
By the way, the usual term for this sort of photograph is a time exposure. Usually anything longer than about a second is included in the term. --Anonymous, 22:30 UTC, June 24, 2009.

Increasing oxygen on Mars

Lets say we want to terraform Mars. What would be the best way to increase the amount of oxygen on Mars? ScienceApe (talk) 06:37, 24 June 2009 (UTC)[reply]

Take a gander at Terraforming of Mars#Building the atmosphere. Clarityfiend (talk) 07:15, 24 June 2009 (UTC)[reply]
Basically - there is oxygen locked up in the soil as iron oxides - and in CO2 in the air - and possibly in all of that mysteriously 'missing' water. The CO2 could be converted to oxygen relatively easily by dosing the atmosphere with green algae or something and letting photosynthesis do the rest. However, turning the CO2 in the atmosphere into oxygen would cause the planet to lose what little greenhouse effect it already has. What we really need (at least initially) is more CO2 to warm the place up. So this presents something of a problem. Anyway - the article Clarityfiend points to covers it nicely. SteveBaker (talk) 14:52, 24 June 2009 (UTC)[reply]
Yeah, getting the atmospheric pressure and temperature up to acceptable levels is likely to be the hard part. Once you've done that you can get the oxygen fairly easily, relatively speaking. --Tango (talk) 16:03, 24 June 2009 (UTC)[reply]

You also have the problem of keeping the atmosphere you do create around Mars since it does not have much of a magnetic field with help prevent the atmosphere from being eroded from solar pressure, or solar winds or somesuch. 65.121.141.34 (talk) 15:06, 24 June 2009 (UTC)[reply]
That's only a problem on a geological timescale, I believe (or, at least, timescales of a few hundred years). If you can get the atmosphere there in the first place, you should be able to top it up enough every few hundred years to prevent a problem. --Tango (talk) 16:03, 24 June 2009 (UTC)[reply]

I thought we just had to somehow activate the mysterious alien machine!!!

But that took a whole 30 seconds to terraform Mars...and I'm not that patient. StuRat (talk) 00:52, 25 June 2009 (UTC) [reply]

What is this wood coloured Insect called?
I found this insect in bushes what is it called.yousaf465'
File:Unkown Insect.jpg

Looks like a Walking stick to me. -- Aeluwas (talk) 08:06, 24 June 2009 (UTC)[reply]
Incest? Must be native to alabama or west virginia...Drew Smith What I've done 08:11, 24 June 2009 (UTC)[reply]
You know, prejudice against Southern whites is still prejudice.

As you ought to know, there's only one safe target for bigoted jokes, and that's the French :-) --Trovatore (talk) 08:37, 24 June 2009 (UTC)[reply]
I think you'll find it's the Americans. Algebraist 11:51, 24 June 2009 (UTC)[reply]
I recall reading that a particular joke on the stupidity of (US of) Americans worked well in most parts of the world due to a general low opinion of Americans, and also worked well in America because Americans presumed it was about those of the "other" half of the US. --Polysylabic Pseudonym (talk) 13:21, 24 June 2009 (UTC)[reply]

I think this is a mantis, not a phasmid ("walking stick"). The grasping forelimbs are clearly visible in the upper image. --Dr Dima (talk) 08:45, 24 June 2009 (UTC)[reply]
Dr dima you jogged my memory. That is a female Archimantis monstrosa.Drew Smith What I've done 10:04, 24 June 2009 (UTC)[reply]
Was it a female ? Oh I already released it into wild. You may compare the size with that of petri dish.yousaf465'
Actually, looking at the petri dish (assuming it's standard sized) this is probbly the mostrosa's smaller cousin. Still, I think it is definitly female.Drew Smith What I've done 05:36, 25 June 2009 (UTC)[reply]

Wikipedia talk:WikiProject Moon

The last response to a post on the moon project was aimed at a bot in 2008. Sometime in 2007 some guy answered himself, and before that is in the archives. ~~ R.T.G 09:51, 24 June 2009 (UTC)[reply]

And? We can't provide pyschological help any more than we can provide phyisical medical advice.Drew Smith What I've done 09:56, 24 June 2009 (UTC)[reply]

I'm sorry, what are you saying? Can you provide any information about the results of the Chang'e 1 mission? ~ R.T.G 12:20, 24 June 2009 (UTC)[reply]
The Chang'e 1 article appears to cover the mission outcome sufficiently to my eye. What, specifically, are you asking about? — Lomn 13:01, 24 June 2009 (UTC)[reply]

Ok. That does appear to be true. Do you have a reference question?

Incidentally, I'm not sure about this this. Is it appropriate to advertise the RefDesk on other parts of Wikipedia? I'm not sure that I've ever seen that done before.APL (talk) 12:51, 24 June 2009 (UTC)[reply]
Generally, that kind of un-asked-for advertising is frowned upon - it's off-topic for the article's talk page and that's "A Bad Thing". But if someone posts a question to an article-space talk page that relates to the subject matter of the article - rather than relating to the writing of the article itself - then it would not be inappropriate to quietly suggest that people might get a better and more timely answer by asking it here. SteveBaker (talk) 14:46, 24 June 2009 (UTC)[reply]

Um, I don't know what to say about recommending the refdesk to people. (it was a project page, no answers in two years, the moon) Myself particularly, I was hoping to clear up the results of the search for water on the Lunar ice article but I do suppose that contacting members of the project directly would produce good results (which I have done now). Please, if you can tell me how the Chang'e 1 results went in relation to the water search please do (especially with a reference for the Lunar ice article). ~ R.T.G 17:28, 24 June 2009 (UTC)[reply]

Ah, I see. In the absence of claims that Chang'e found ice (something I would expect to be big news), I would assume there were no findings of significance -- which should not be confused with proving a lack of ice. Various news stories on LCROSS discussing the uncertainty of lunar ice support this premise. — Lomn 17:47, 24 June 2009 (UTC)[reply]
I thought something like that as well but it would good if they reported it, even as inconclusive and we could just update the article. I can't just change it to say "they musn't have found any" but there seems to be nothing around about the details. ~ R.T.G 13:46, 25 June 2009 (UTC)[reply]

FWIW, I've tagged the project as {{inactive}}, as it obviously is at present. --Kurt Shaped Box (talk) 17:43, 24 June 2009 (UTC)[reply]

Do Genetically Modified Crops Have Larger Yields?

I am wondering if there is evidence of GM crops yielding larger harvests than non-GM. Unomi (talk) 10:52, 24 June 2009 (UTC)[reply]

They can, if they're genetically modified to produce higher yields. Or they can be GMed for some other purpose, such as pest resistance, in which case they would also probably have higher yields as they aren't constantly eaten. Other cases, for example most pure science GM projects, yield is not the purpose of the GM, so often have much lower yields/growth rates/etc.Aaadddaaammm (talk) 11:48, 24 June 2009 (UTC)[reply]
Can you point to sources affirming higher crop yield? GM crops are in wide circulation it seems? Unomi (talk) 12:42, 24 June 2009 (UTC)[reply]
Our article on genetically modified food contains some information on the distribution of GM crops in various parts of the world; for example, "In the US, by 2006 89% of the planted area of soybeans, 83% of cotton, and 61% maize were genetically modified varieties". Gandalf61 (talk) 12:50, 24 June 2009 (UTC)[reply]
Right, what is interesting is that there is no mention of benefits, I would assume that the point of GM crops would be yield improvements or other form of economic benefit, it is not clear from the article if such a benefit exists? Unomi (talk) 14:54, 24 June 2009 (UTC)[reply]

A quick Google survey finds a couple theories. One is that GM crops fare poorly in the US. Another is that GM crops boost yield in India. The latter suggests that GM crops show an advantage in areas where pest control is less prevalent. US farms might see a GM benefit by foregoing pest control at the expense of yield -- depending on the numbers, this may be desirable environmentally and/or economically. I haven't searched for firm info along these lines, though. — Lomn 15:03, 24 June 2009 (UTC)[reply]

Apparently GM crops are bred for herbicide or insect resistance at the cost of yield[33]. Of course if insects eat the higher yielding non-GM crop, you have perhaps lower yield yet. Or if the crop is choked with weeds, the yield goes down. The non-GM crops could be sprayed with insecticide, but that is not the greenest world either. I doubt that agribusiness and farmers want to plant GM crops just for fun. Edison (talk) 19:12, 24 June 2009 (UTC)[reply]

negative mass in general relativity

The Schwarzschild solution for the spherically symmetric vacuum Einstein equations formally exists both for positive and negative mass (for negative mass no horizon forms, and the curvature singularity at the center is naked). Negative mass solutions are excluded as unphysical. My question is: is the exclusion of negative mass solutions just an "experimental fact", or do such solutions cause some intrinsic inconsistency in general relativity? My question refers both to Schwarzschild solutions (i.e. solutions to the vacuum Einstein equations) and to non-vacuum solutions which asymptotically (for large radius) behave like a Schwarzschild solution with negative mass.XYZsquared (talk) 12:23, 24 June 2009 (UTC)[reply]

You may be interested in our article on exotic matter, which includes the concept of negative mass. We note that negative mass violates Einstein's "positive energy" condition, but that the condition is not required for the theory to hold together mathematically. As such, the exclusion of negative mass can be considered for now an experimental fact, though work has been and is being done to investigate the possibility of its existence. — Lomn 13:11, 24 June 2009 (UTC)[reply]

Naked singularities are something of a problem. There isn't a great deal of evidence for the cosmic censorship hypothesis, as far as I know, but if it doesn't hold we have some pretty big questions still to answer ("What does a singularity look like?" being the main one, I guess). --Tango (talk) 13:18, 24 June 2009 (UTC)[reply]

Does alcohol kill germs? Does silver?

Hello, there are some people around here arguing about alcohol in the Lord's supper, specifically about historical practices. Some assert that when a common cup was used, the combination of alcohol in the wine and silver in the chalice was successful in killing germs and there was thus no danger of spreading the influenza through Communion. Others, however, claim that this is absolutely false, and that the alcohol in a cup of wine is insufficient for the preventing of disease. Can anyone help me out here? 65.210.65.50 (talk) 15:05, 24 June 2009 (UTC)[reply]

AFAIK, only nanoparticle silver has anti-microbial properties, bulk solid silver does not. Eating or drinking from silverware will certainly not prevent disease all by itself. Strong wines (20% alcohol) could be alcoholic enough to have some inhibitory effect (the limit of wine strengh arises from yeast no longer being able to grow at such concentrations), but disinfectant alcohol is 70%, so 20% could easily leave viruses or spores intact.Yob Mod 15:22, 24 June 2009 (UTC)[reply]
It's false. There is enough alcohol in wine to have an effect, but the effect is far too slow to kill viruses before the cup is passed from one drinker to another. Any possible effect of the silver would be much slower yet. Looie496 (talk) 15:25, 24 June 2009 (UTC)[reply]

Both arguments are only half-correct (and half-wrong). Wine contains antibacterial compounds, which are separate from the alcohol. The compounds come, originally, from the grapes. So, as with most benefits of wine, it is a benefit of grapes. We just like to ignore grapes because we can't get drunk eating grapes. (Googling for a reference...) How's this? -- kainaw ™ 15:26, 24 June 2009 (UTC)[reply]
A discussion recently (since the swine flu outbreak) noted that some churches are using wine with higher alcohol content with the "common chalice" and others are giving only the bread, or are using individual cups. Intinction, or dipping the wafer in the wine, is another approach, but some slobs allegedly get their fingers in the wine, and Lord knows where that finger has been. Wiping the cup between sippers seems like window dressing, given the backwash done by slobs. Edison (talk) 18:44, 24 June 2009 (UTC)[reply]

Even in nano-particle sized chunks, there is no evidence for the medical efficacy of silver (see Colloidal silver) - but this isn't just another 'quack medicine' scam - there is a particularly nasty problem for people who get suckered into taking the stuff on a regular basis: Argyria - which turns your skin permenantly a particularly ikky shade of blue/purple. The scammers are also selling gold colloids - neglecting to mention Chrysiasis - which also turns your skin blue. SteveBaker (talk) 02:20, 25 June 2009 (UTC)[reply]

It should be noted that silver compounds, such as silver sulfadiazine, have established efficacy in the topical treatment of infected burns and ulcers, and in prevention of infections (central venous catheters, for example, are often coated with silver sulfadiazine, which reduces risk of infection by 35%) and that this has nothing to do with ingestion of elemental silver or with chalices - other than being a possible source of misunderstanding. - Nunh-huh 02:31, 25 June 2009 (UTC)[reply]

Returning to the OP's original question - I don't see that there is a problem here. Either you're using blind faith to get your head into the whole Sacramental union thing - in which case you're supposed to mindlessly believe that the wine is literally (not 'figuratively') transformed at that moment into the blood of Christ (it definitely says that in at least four or five places in the Bible)...which I'd presume was unlikely to harbor too many nasty bugs...or perhaps you think it's just particularly nasty wine - in which case there is really no point in bothering with the ceremony at all. Either way - a few flesh-eating bacteria should be no problem for you. SteveBaker (talk) 03:38, 25 June 2009 (UTC)[reply]

Sabre wolf

I can't find a article on the sabre wolf animal that is now extinct! Does it exist under another name or is there another article? 82.203.3.4 (talk) 15:33, 24 June 2009 (UTC)[reply]

Do you mean http://en.wikipedia.org/wiki/Tasmanian_wolf ?

Hmm, never heard of a sabre wolf. Kurten & Anderson Pleistocene Mammals of North America also does not list anything that's even remotely similar. Or do you mean Dire wolf? --Dr Dima (talk) 17:26, 24 June 2009 (UTC)[reply]

Sabre-toothed tiger? Livewireo (talk) 18:26, 24 June 2009 (UTC)[reply]
Sabre Wulf?? Exxolon (talk) 21:16, 24 June 2009 (UTC)[reply]

General scientific magazines - like Science and Nature

What is the point of magazines like Science and Nature? Most people - if not all - won't understand the most articles, will they? Why don't serious scientist only read "their" scientific magazines. On the other hand, easily explained science like that of Scientific American could be more of a help for many people, since many of its articles are generally accessible.--Mr.K. (talk) 17:54, 24 June 2009 (UTC)[reply]

I rarely understand the technical details of articles in Science or Nature, but I still enjoy reading them. As long as you have a solid grounding of science in general, you can get something out of most of the articles. I find it interesting to see how research is done in fields I know little about, as well. --Tango (talk) 18:02, 24 June 2009 (UTC)[reply]

And just because someone has a doctorate in say astrodynamics, does not mean that they might not also be interested in seeing what new discoveries have been made in biology, or chemistry. 65.121.141.34 (talk) 18:07, 24 June 2009 (UTC)[reply]

These journals are great for scientists to see what really are some of the current/most important research topics happening in other fields than one's own, and science isn't as compartmentalized as the public thinks ("materials scientist" vs "biochemist", etc.). DMacks (talk) 18:16, 24 June 2009 (UTC)[reply]

Well, they've been making money pretty solidly for a LONG time - there's certainly a market for them somewhere. They aren't as unapproachable as you might first think...and they are a great way for specialised scientists to get a smattering of what's going on outside their fields. SteveBaker (talk) 00:45, 25 June 2009 (UTC)[reply]

Another Venus Flytrap question

Is it really true that venus flytraps are only truly native to an area surrounding a prehistoric meteorite impact crater in North Carolina? --90.241.27.96 (talk) 19:48, 24 June 2009 (UTC)[reply]

This is being discussed in-depth at the previous question and does not need to be re-posted. — Lomn 19:58, 24 June 2009 (UTC)[reply]

Sorry. I should have made it clearer. My question is in relation to the theories that the venus flytrap is of nonterrestrial origin which mention the fact that the VTF's natural range is in a radius around a certain meteorite crater. I wanted to know if this crater actually exists where they say it does. Thanks. --90.241.27.96 (talk) 20:06, 24 June 2009 (UTC)[reply]

I am not seeing anything about North Carolina in our meteorite article. The idea that Venus flytraps are of extraterrestrial origin is not likely to be found with merit in a respectable scientific community unless there is some other evidence supporting the theory. 65.121.141.34 (talk) 20:19, 24 June 2009 (UTC)[reply]

Flytraps are absolutely terrestrial. They are related to other existing carnivorous plants in the Droseraceae. The word "Venus" comes from the goddess, not the planet.

This seems to be a common rumor, though. The Straight Dope covered this once. APL (talk) 20:57, 24 June 2009 (UTC)[reply]

There is no doubt that these plants are related to all other life on earth - nothing weird going on there. The question about North Carolina comes about from a crazy-looking contradiction between versions of a particular book. It's already being discussed above - and I respectfully ask that THAT part of the question continues to be answered up there rather than splitting the thread in a confusing manner. SteveBaker (talk) 22:21, 24 June 2009 (UTC)[reply]
He's asking about the commonly held, but rarely documented belief that they are found near a meteor crater only. I have heard this, and can neither prove it true or false. However, I can say that it is a terrestrial plant, and if there is a meteor connection it can be explained by the extra nutrients a meteor may have provided.Drew Smith What I've done 05:39, 25 June 2009 (UTC)[reply]

Converting Contour Maps to Height-Map Data

I have a lot of contour maps (geographic maps of elevation), which are unfortunately images in "standard" formats like JPEG. Many of them are clean images, in the sense that they are only white backgrounds with black lines for elevation contours; and some text for the height markers. My desire is to turn these into data files, roughly a series of x,y, and z coordinates. Is there a good software utility for converting them to a data format suitable for data processing? My current plan involves a lot of manual labor (manually gray-scale filling between the contours, and then converting the grayscale image values to an easy-to-use CSV file or something); but this will be painful. It seems like this task must have been encountered before and automated.... are there standard approaches I'm unaware of? Nimur (talk) 20:47, 24 June 2009 (UTC)[reply]

I've seen lots of software for converting height info to contours, but never anything in the reverse direction. It would be a p.i.t.a. to write a program to do it, but certainly not impossible -- you might try the Computing Desk if you don't get any response here. Looie496 (talk) 21:03, 24 June 2009 (UTC)[reply]

Why bother? NASA has a free download of elevation data for almost the entire planet at spectacular precision. (See Shuttle Radar Topography Mission) They offer height data every 30 meters in the USA and every 90 meters elsewhere. You can download the data from their website here: http://dds.cr.usgs.gov/srtm/

The information you can get from even a pristine contour map would likely be vastly inferior...but you don't have pristine maps - you have JPEG - which is a horrible format for anything other than your family photo collection and Internet porn! I'm a programmer who does stuff like this for a living - and what you're proposing would be a very VERY last-ditch emergency, no other way to do it, kind of a thing...with not much hope of success. You can probably use standard image processing techniques to 'vectorize' the data (although because it's JPEG - you won't get great results) - then write software to make sure that every vector connects either to a single other vector - or to the edge of the map...and that vectors never cross each other. Your map will certainly not meet either criteria - so you'll have to build some heuristics to fill in the gaps. For contour lines that touch the edge of the map - you have to figure out which side of the line is higher and which is lower. and make a loop from them by connecting up a 'fake' contour that goes around the edge of the map. When that's done, you have a set of irregular polygons - one for each closed contour 'loop'. Once you have that, you can write more code that 'rasterizes' the contours from the lowest to the highest in order - filling in the interior of the polygon with height values equal to the height of the contour. Finally, you'd probably want to run a smoothing pass to get rid of the 'steppy' appearance of the resulting data.

But please - this is an utter pain in the butt - each one of those steps is fraught with special cases...when there is a vertical cliff and all of the contours smoosh together...when the vectoriser gets confused by JPEG-induced noise...when you can't determine whether one contour 'loop' represents a hollow or a peak. Just consider the simplest possible map which has a single 100' contour that goes from east to west across the width of the map...with 100% perfect software. How do you know whether the north half of the map is over 100' or the southern part? You can't! And that's the simplest imaginable case.

So - consider using the NASA data. SteveBaker (talk) 22:11, 24 June 2009 (UTC)[reply]

In rough terrain, SRTM data often has a vertical uncertainty of +/- 5m at 90% confidence (in some cases worse). There are many applications where I would trust carefully produced, locally surveyed maps to be more accurate than SRTM. SRTM is great stuff for filling in huge swatches of the Earth that have never been studied in depth by people on the ground, but depending on the application and the level of accuracy needed it may not be up to the task. (As an aside, getting +/- 5m precision while measuring from 300 km away and traveling 7 km/s is still a stunning technical achievement.) Dragons flight (talk) 22:48, 24 June 2009 (UTC)[reply]

I understand what you're saying about the lack of precision of the NASA data - and you are right in saying that a good contour map may be better - but contour maps, scanned into JPEG and converted back into elevation data doesn't come into the category of "carefully produced". The problems won't just be small precision issues - they'll be things like a hole in the ground as deep as Mount Everest is tall...in the location where Mount Everest should be! SteveBaker (talk) 00:21, 25 June 2009 (UTC)[reply]
Steve, all the above points are exactly why I was hoping to avoid writing my own software. JPEG and image-processing algorithms are usually a bad combination. Also, as you mention, the problem is underdefined/undersampled by very nature. Unfortunately, the maps I have are moon elevations (so the Space Shuttle survey is out), and I can't find higher resolution data sets than these maps. I may have to do a lot of manual data entry, because it doesn't seem like there's a good algorithmic way to do it. Thanks for your inputs. Nimur (talk) 01:55, 25 June 2009 (UTC)[reply]
Most of the problems Steve mentioned can't be fixed by software, so it doesn't matter if you write it yourself or not. It's going to be very labour intensive correcting all the mistakes and filling it the gaps that the software can't work out, even if you use the best software reasonably possible. --Tango (talk) 03:15, 25 June 2009 (UTC)[reply]

OK - it would have helped a lot if you'd said it was the Moon at the outset! There is online lunar elevation data too: http://onmoon.jpl.nasa.gov/ is the NASA site. We know for sure that your maps weren't carefully prepared by an army of guys with theodolites...so there is no doubt that your contour maps must have been generated from "DEM" (digital elevation data) maps originally - and you can't possibly "win" by reverse-engineering contour maps back into DEM format again! There have been so few elevation surveys of the moon and AFAIK, their results are all publically available...there is no way you can do better than grabbing the best thing from the web - probably in DEM, GeoTiff or 16-bit PNG format - which can all be easily converted into whatever form you want. The spatial resolution is something like 1km to 2km per pixel - which isn't great...but your contours can't possibly be any better - and I can guarantee that they are worse because any time you do anything whatever to this kind of data, you "damage" it. This paper [34] explains what data there is and where to get it from. The 'CEPS' program at the Smithsonian have people who you can talk to by email to request specific data from these various projects if you can't easily find it online. (Try http://www.nasm.si.edu/ceps/staff/sandre.cfm for example). SteveBaker (talk) 03:22, 25 June 2009 (UTC)[reply]

The source in question is the Apollo 17 landing site survey data (and similar for other landings). From what I can tell, these contours were hand-drawn, guided by stereo-photographic and preliminary radar soundings. The accuracy claimed is 10 meters in elevation, and "whatever" ("1:25000", apparently accurate to a few meters per pixel) in latitude-longitude (the scale is not actually easy to tell). Fortunately, this particular project is a "hobby" side-project, and the particular use of this historical data source is more of an homage to the missions than a scientific necessity; however, I will definitely be checking out the lunar surface surveys you linked, which probably do have better data for my needs. Thanks again, Nimur (talk) 03:49, 25 June 2009 (UTC)[reply]

What reference do they use for moon elevations since it does not have a sea level? 65.121.141.34 (talk) 13:00, 25 June 2009 (UTC)[reply]

Uranus dark spot

What is Uranus dark spot for? Is it a cycle storm happens once every 20 years. I just know Uranus dark spot is weaker than Saturn's Great White Spot. Is Neptune's Great Dark Spot a permanent storms, or it goes away once now and then. Is Saturn's Great White Spot happens every 10 years?--72.219.133.45 (talk) 21:04, 24 June 2009 (UTC)[reply]

If Uranus didn't have a dark spot in the center, then I'd be worried. :-) Butt seriously, the difficulty in answering your questions is that, unlike the Great Red Spot on Jupiter, most of the other similar formations can't be viewed from Earth, but only by the occasional passing space ship. Since this gives us very few data points, it's hard to say how old each spot is or exactly how it works. Hopefully, in the future, we will be able to put a permanent satellite in orbit about each planet, which can then relay pictures to us detailing the development, longevity, and nature of each cloud formation. StuRat (talk) 22:52, 24 June 2009 (UTC)[reply]

Can the Ref Desk really not manage to answer a question about Uranus without making that extremely unoriginal and immature joke? --Tango (talk) 23:19, 24 June 2009 (UTC)[reply]

Perhaps we'll have to wait until it is renamed Urectum.-- kainaw ™ 00:22, 25 June 2009 (UTC)[reply]

Yes - but we're going to have to give StuRat extra credit for delicately weaving illicit medical advice into the answer.SteveBaker (talk) 00:41, 25 June 2009 (UTC)[reply]

The fact that every single gas giant we've ever looked at closely enough has had one of these spots suggests that they are a necessary consequence of the physics of such objects. Given how different in size, thermodynamics and composition they all are - this strongly suggests that the spots can't go away for long without being regenerated. SteveBaker (talk) 00:41, 25 June 2009 (UTC)[reply]

True enough, and even the Earth's hurricanes, although of much shorter duration, need to regenerate several times each year to dissipate heat from the oceans. It's interesting that such storms can last for at least centuries, in the case of the Great Red Spot. Perhaps some are even permanent, having existed since shortly after the host planet formed. StuRat (talk) 02:04, 25 June 2009 (UTC)[reply]

Alanine

This is the structure of alanine as given by Lehninger's Principles of Biochemistry:

COO^- | NH₃⁺---C---H | CH₃

However, most other sources give the structure of alanine as:

COOH | NH₂---C---H | CH₃

I realise this is exactly the same thing but I wonder what does the difference in notation represent (i. e., does one notation emphasise a particular property of alanine?). What's the difference between the two notations? Thanks in advance to anyone who can help. --Leptictidium (mt) 21:13, 24 June 2009 (UTC)[reply]

I only have a basic knowledge of chemistry, so I'll let someone else fill in the gaps, but what's shown there is a zwitterion, a substance which can act as bases and acids depending upon the conditions they're in, and all amino acids including alanine display this property. I'll let someone else explain in more detail, though. Regards, --—Cyclonenim | Chat 22:00, 24 June 2009 (UTC)[reply]
From what I remember of my biochemistry class (which isn't much, even though it was barely 3 months ago...how sad) is that the charges on the COOH and the NH₃ depend on the pH of the solution they are in. I think the first structure you showed is at body pH, pH 7, and the second structure is at one of the extremes of the pH scale, but unfortunately I can't remember which one. 129.65.201.234 (talk) 00:12, 25 June 2009 (UTC)[reply]
Our amino acid article talks about the zwitterionic form of these molecules. The hydrogen on the COOH part is acidic, the nitrogen of the NH2 part is basic, and acids and bases react with each other. The exact conditions under which each of these is the preferred structure depends on solvent primarily and maybe other things in the solution, but not strictly the pH for these simple cases. The total acid/base effect is balanced in the molecule itself rather than a net gain or loss of hydrogen ions. DMacks (talk) 01:00, 25 June 2009 (UTC)[reply]

Rice keeps sticking to non-stick cooker.

Should I be concerned? Imagine Reason (talk) 22:35, 24 June 2009 (UTC)[reply]

Is it an old non-stick cooker? The non-stick coating doesn't last forever. --Tango (talk) 23:17, 24 June 2009 (UTC)[reply]

And you might well ask where the non-stick coating goes. Unfortunately, you may end up eating most of it. StuRat (talk) 00:39, 25 June 2009 (UTC)[reply]

I was under the impression the non stick coating mostly wears off due to abuse like scrubbing and dishwashing. Sifaka ^talk 01:05, 25 June 2009 (UTC)[reply]

Yes, but some of it still gets into your food. I don't think there is much you can do about that. --Tango (talk) 02:38, 25 June 2009 (UTC)[reply]

Avoiding non-stick pans should significantly decrease your consumption of non-stick coatings. :-) StuRat (talk) 03:02, 25 June 2009 (UTC)[reply]
True, but it also significantly increases the amount of washing up you need to do! --Tango (talk) 03:09, 25 June 2009 (UTC)[reply]

You might try adding a little oil to the rice. BTW, what type of rice cooker is it? just-emery (talk) 01:19, 25 June 2009 (UTC)[reply]

I've seen plastic bags designed to line crock pots (food only touches bag). I've also seen (semi)-prepared foods in plastic bags that you cook by placing in a pot of boiling water. In either case, the food doesn't contact the cooking vessel. Now a rice cooker is higher temp than a crock pot since the water actually boils, and even higher still since IIRC it uses the rise in temp once the water is mostly evaporated to signal "done". So need to make sure the plastic is stable at operating temp & time. DMacks (talk) 02:56, 25 June 2009 (UTC)[reply]

Incedentally, non-stick coatings are pretty inert, undigestible stuff. Any tiny bits that end up in your food pretty quickly end up with the rest of the inert, undigestible stuff you eat; which is to say the toilet. I would not be concerned about that. But yes, after 5-10 years, nonstick pans need to be replaced... --Jayron32.talk.contribs 03:30, 25 June 2009 (UTC)[reply]

Happiness and children

Have any longitudinal studies been performed to determine whether initially childless couples who have children become happier compared to couples that adopt or remain childless? Have any of them followed the parents until the children reached adulthood? Neon Merlin 23:11, 24 June 2009 (UTC)[reply]

This Newsweek article discusses a 2006 study which claimed that "parents have significantly lower marital satisfaction than nonparents". That's not exactly measuring "happiness", though, and the study says it swung the other way on "feeling a greater sense of purpose and meaning in their lives", where the parents won. (The Newsweek article is written in the first person and I think it's inaccurate in a couple of its descriptions of what's in the study, if my memory of other descriptions serves. Here is another description of the study. I haven't found the actual study.) Another point I remember from a few years ago when this was originally reported: I believe it claimed that marital satisfaction decreased additionally with each additional child, until the dissatisfaction plateaued at the 4th child ... I think. Tempshill (talk) 02:18, 25 June 2009 (UTC)[reply]
The study is here. Algebraist 02:22, 25 June 2009 (UTC)[reply]

Technically, all couples are "initially childless" - but I presume you mean people who have a lot of trouble conceiving a child or completely fail to do so - who later have medical intervention or adopt in order to get a child. This would be a tough study to do because you need a control group who fail to do so - yet who were equally happy right up to that point in their lives. The studies mentioned above are just comparing families with and without children and that's an entirely different matter. The people who strive so hard to have children when it's very difficult may well suffer greatly increased stress - or they may benefit from the 'bonding' experience of working towards this shared goal...which makes them a very different bunch of people from the ones who merely choose not to have children and those who got pregnant easily. There are an awful lot of variables to control for - beyond the fact of being childless or not. It's easily possible, for example, that the couples who are initially very unhappy fail to push through the arduous process (not to mention, cost) of medically assisted reproduction - and perhaps they might be turned down for adoption simply because they are unhappy and thereby deemed unsuitable. Perhaps poorer people are less likely to be able to adopt or have medical help...you could easily end up merely comparing rich people with poor people and come to a conclusion that is actually more to do with money than children. Such a study would be hard to do fairly. SteveBaker (talk) 02:58, 25 June 2009 (UTC)[reply]
Do they have to be initially childless? Couldn't they have children from previous relationships? Vimescarrot (talk) 08:40, 25 June 2009 (UTC)[reply]

The funny thing is that many couples have children to save the marriage. --Mr.K. (talk) 10:37, 25 June 2009 (UTC)[reply]

June 25

inverse metal

I am trying to start a new article on Inverse metal but I cant seem to find many sources. here is one: http://www.sciencedirect.com/science...21a8092c95ac67 "This material is probably an inverted metal with the deuterons moving in the field from the stationary electrons, which gives a predicted interatomic distance of 2.5 pm, close to the measured value. Thus, we prove that an ultra-dense deuterium material exists."
here is another: http://www2.chem.gu.se/staff/leif_holmlid.html
I was hoping that one of you might actually know about this subject or at least be able to find a good reference for it. just-emery (talk) 01:07, 25 June 2009 (UTC)[reply]

The article has now been redirected to Ultra-dense deuterium. just-emery (talk) 01:55, 25 June 2009 (UTC)[reply]

The redirect is now listed for speedy deletion, if anyone's interested. Tempshill (talk) 02:02, 25 June 2009 (UTC)[reply]

evolution books

Does anybody have any recommendations on a book covering the topic of evolution that is intended for general readers?

The Selfish Gene. Tempshill (talk) 02:03, 25 June 2009 (UTC)[reply]
On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life is supposed to be very good, though I have not read it. Algebraist 02:05, 25 June 2009 (UTC)[reply]

I agree with Algebraist (and I have read it) - get it straight from the man himself - Charles Darwin's book is remarkably readable. and you can read it online or download it for free. It doesn't cover the role of genetics and DNA because that stuff hadn't been discovered by then. For specific details on the order that things happened - how and why - with particular emphasis on the path that ultimately leads to humans, I'm fond of reading Richard Dawkin's book "The Ancestor's Tale". His other famous book on the subject "The Blind Watchmaker" is also very approachable to the layperson. SteveBaker (talk) 02:44, 25 June 2009 (UTC)[reply]
If you are looking for a basic introduction masked behind a work of fiction I would check out Next by Michael Chrichton(sp?)Drew Smith What I've done 06:36, 25 June 2009 (UTC)[reply]
Darwin is a good writer, but he is very defensive and thus proceeds at a snails pace. He also is not yet aware of DNA and the actual mechanisms of inheritance and variation. For a general audience, I would recommend a book that covers the modern synthesis. Dawkins also writes very graceful English. The Blind Watchmaker is more accessible than The Selfish Gene. I also liked The Ancestor's Tale, but it's a very different take on the topic. --Stephan Schulz (talk) 11:07, 25 June 2009 (UTC)[reply]

gravitational intensity of a moving body

If a body were moving near the speed of light would the intensity of its gravity be greater or less in the forward direction than in the rear direction? -- Taxa (talk) 05:24, 25 June 2009 (UTC)[reply]

Neither. The field is symmetric in the forward and reverse directions. -- BenRG (talk) 08:56, 25 June 2009 (UTC)[reply]

matlab how to

okay great scientists sitting over there ...plz any one help me.i am required to show coordinates(x,y) of points in my plot in matlab .how should i get it.
Sameerdubey.sbp (talk)

There is a button at the top of the plot window that does exactly that. The button is called "Data Cursor". You click it and then click one of the data points on the plot; the coordinates of the data point then appear in a rectangular box next to the point. To remove, hit Delete key. --Dr Dima (talk) 07:28, 25 June 2009 (UTC)[reply]

thanks a lot Dr.dima.Can you suggest me some good book on matlab .if i belong to MECHANICAL ENGINEERING TRADE.

how to optimize

which optimisation procedure is used in optimisation of heat transfer problems.i want to optimize one dimensional heat transfer. Sameerdubey.sbp (talk)

Please elaborate. Normally, the word "optimization" refers to finding a maximum of a function of one or more variables on a given domain under given constraints. Heat transfer is a phenomenon, not a mathematical function. What is it that you want to optimize? If you want to learn about optimization algorithms in general, you can start with Simulated annealing, gradient descent, and Nelder-Mead method. --Dr Dima (talk) 07:40, 25 June 2009 (UTC)[reply]

Gasoline and water

If I soaked a paper towel in water, then got as much gas on it as I could, would the towel burn? I know gas and water don't mix, so I wasn't sure, but I didn't think it would be a good idea to try to find out myself :-) 24.93.116.128 (talk) 14:18, 25 June 2009 (UTC)[reply]

^ Mary V. Solanto (July 1998). "Neuropsychopharmacological mechanisms of stimulant drug action in attention-deficit hyperactivity disorder: a review and integration". Behavioural Brain Research. 98 (1): 127–152. doi:10.1016/S0166-4328(97)00175-7. PMID 9708845.

^ Shimano, Eido T. (1991). Points of Departure: Zen Buddhism With a Rinzai View. Livingston Manor, NY: The Zen Studies Society Press. p. 152. ISBN 9780962924606.

[Solanto1998-1] Mary V. Solanto (July 1998). "Neuropsychopharmacological mechanisms of stimulant drug action in attention-deficit hyperactivity disorder: a review and integration". Behavioural Brain Research. 98 (1): 127–152. doi:10.1016/S0166-4328(97)00175-7. PMID 9708845.

[shimano-2] Shimano, Eido T. (1991). Points of Departure: Zen Buddhism With a Rinzai View. Livingston Manor, NY: The Zen Studies Society Press. p. 152. ISBN 9780962924606.

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