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February 16

EMP and safe deposit boxes

(Note: I bumped this section down to February 15 even though it was initially posted on February 14 because I asked a whole bunch of new questions on February 15 and I wanted to make sure the questions were answered before this section ended up being archived and that people didn't overlook the section just because it was in an earlier day and assume that the questions had already all been answered.) —Lowellian (reply) 02:29, 17 February 2008 (UTC)[reply]

Would a typical bank safe deposit box form an adequate Faraday cage to protect electronic contents from an electromagnetic bomb? —Lowellian (reply) 00:02, 14 February 2008 (UTC)[reply]

Well I can't actually answer the question bear in mind your chance of getting access to your bank safe deposit box during the extreme chaos created by an electromagnetic bomb may be slim Nil Einne (talk) 06:54, 14 February 2008 (UTC)[reply]

Let's say it's electronics you want to get access to once the chaos calms down, so the question still stands, and I'd still like an answer if someone can give one. Also, your response did give me an idea for another question: would modern automobiles be able to start up after an EMP, or are they so dependent on electronics that they would be unable to do so? —Lowellian (reply) 12:50, 14 February 2008 (UTC)[reply]

A modern automobile would almost certainly toast after even a moderate EMP event. As it is, the police are learning to use devices that lay in the roadway and transfer an electrical transient to your car in order to stop you; this substitues (more safely) for the spike strips they now lay across the road to deflate all your tires.

A safe deposit box made of metal would probably provide pretty good protection against EMP. It all depends on how tightly the cover seals the box and how good and uniform is the electrical contact between the cover and the box; remember that a Faraday cage only works if the openings in it (including long, narrow slots!) are substantially shorter than the wavelength of the signal(s) you're trying to block.

Atlant (talk) 13:59, 14 February 2008 (UTC)[reply]

According to a recent documentary, you can make a car start after an EMP attack by replacing the solenoid. 206.252.74.48 (talk) 14:16, 14 February 2008 (UTC)[reply]

Very funny! Remember: after a nuclear attack, look for a car that predates any electronics fancier than an 8-track player.

Atlant (talk) 15:46, 14 February 2008 (UTC)[reply]

A safety deposit box generally is a thin metal box inside a thicker metal box inside a metal or reinforced concrete vault. This provides three levels of shielding against external electromagnetic fields, and should provide a respectable amount of shielding, but I have not seen figures on the strength of the hypothetical EMP so I could not attempt to calculate the field strength inside and compare it to the threshold for damage to electronics, magnetic media, etc. I'm surprised the folks who sell personal keychain radiation monitors [1] and iodine pills [2] do not advertise EMP safes for the home, perhaps welded from 1/2 inch ferrous metal. I expect that the avionics and communication equipment on military command planes and bombers are hardened to survive EMP, and they would not get off the ground if they had to be as solid as a safety deposit box installation. Edison (talk) 17:18, 15 February 2008 (UTC)[reply]

EMP-specific safes? Does that mean that ordinary metal home safes not secure against EMP? If not, then why not? —Lowellian (reply) 19:14, 15 February 2008 (UTC)[reply]

Many home safes seem to be plastic and concrete in large part, to deter theft and protect papers from fire. Older office safes are big steel boxes and it seems they would provide a great amount of shielding against external magnetic fields. I have seen nothing so far to convince me than a much thinner metal box would be inadequate. Edison (talk) 20:36, 15 February 2008 (UTC)[reply]

Another related question: websites I have seen about using aluminum foil or trash cans to construct Faraday cages usually recommend attaching a grounding wire to the makeshift cage. If, as suggested above, safe deposit boxes and metal safes without grounding wires may form adequate Faraday cages, why would the grounding wire be necessary on these makeshift cages? And does the grounding wire actually have to be stuck into the ground, as in the earth or soil? What if you can't leave the Faraday cage outside the house, then what do you do? (Besides sticking it in the soil of a houseplant vase? *wink* ) (Sorry for all these questions, but I don't know much about electrical physics.) —Lowellian (reply) 21:36, 15 February 2008 (UTC)[reply]

Whether a metal container is grounded or not should not affect its permeability to magnetic fields. Dissipating an electrical charge, such as from lightning is a different question. If current flowed through the container from a source to a ground connection, that might actually cause a magnetic field in the interior, if the current density was higher in one side of the container than in the other side. Aluminum foil would provide negligible magnetic shielding, but couod provide shielding against electric fields. I once used a coffee can as a Faraday cage to shield a large speaker magnet from causing distorted color in a TV picture tube. I have seen chicken wire used to provide a Faraday cage around a chamber where human subjects had electrophysiological recording of brain waves during perception experiments. No idea how either of these would fare against EMP. Edison (talk) 02:49, 17 February 2008 (UTC)[reply]

What about my general questions about grounding? How do you "ground" things inside the house without soil? —Lowellian (reply) 20:57, 18 February 2008 (UTC)[reply]

If the plumbing in your house is all-metal, you can ground something by wiring it to a cold-water pipe. --Carnildo (talk) 21:13, 18 February 2008 (UTC)[reply]

James Randy and Aliens

Anyone know if James Randy believes in Aliens? Malamockq (talk) 03:09, 16 February 2008 (UTC)[reply]

From his online bio] I get the idea that he does not believe that sentient technologically superior aliens have flown to earth in UFOs. I can't speculate on whether he thinks there is life, intelligent or not, elsewhere in the universe. Sifaka ^talk 03:50, 16 February 2008 (UTC)[reply]

Yea, the UFO thing is quite a bit different though. It's one thing if he thinks there might be life on other planets, it's another thing if they have actually visited us. Malamockq (talk) 21:51, 17 February 2008 (UTC)[reply]

You may want to see my somewhat OT comment here Talk:Unidentified flying object#What the hell is it going to take ... (please don't reply there tho) Nil Einne (talk) 17:26, 16 February 2008 (UTC)[reply]

Well, first, his name is James Randi, with an "i", not a "y". Secondly, to answer your question, it seems that he believes it's likely that there are other intelligent lifeforms out there in the universe, but that there is no good evidence so far that any aliens have ever visited Earth. For example, he has endorsed the SETI project in the past (see here). However, knowing Randi, he has probably never stated outright that he "believes in aliens" since he prefers solid objective evidence before making such a claim. -- Hi Ev 01:28, 18 February 2008 (UTC)[reply]

Probability speaking, it's far more improbable that Earth is the only planet in our universe to have life, than for life to exist on other planets. 64.236.121.129 (talk) 17:07, 20 February 2008 (UTC)[reply]

EMBRYOLOGY

Do you know some tacts to remember the steps of growth that ocurre in human embryo growth during the first 8 weeks? thanks —Preceding unsigned comment added by 201.220.222.140 (talk) 04:41, 16 February 2008 (UTC)[reply]

There aren't many tactics beyond just memorization. Embryology, Human embryo would help. Also search pubmed.org for reviews on human embryology. Wisdom89 _{(_T / ^C)} 04:45, 16 February 2008 (UTC)[reply]

You can find some embryology mnemonics here. Personally I usually have more trouble remembering the mnemonics than I do the information they're supposed to help you remember. - Nunh-huh 04:47, 16 February 2008 (UTC)[reply]

I'm in Nunh-huh's camp and despise most mnemonics (although I hate "pneumonics" even more ;-). In approaching topics that appear to need rote memorization, I usually first try to understand terms, how structures got their names, etc. Some examples from embryology might be the origin of the term morula (a bunch of cells resembling a mulberry), why it's called the ultimobranchial body ("ultimo-", last; hence, "last of the branchial pouch derivatives"), etc. Works great for me, but your mileage may vary. --David Iberri (talk) 20:08, 16 February 2008 (UTC)[reply]

physics/water barometer

the height of water in a water barometer is measured from the open atmospheric pressure end vertically to the under side of the J tube.

the question is - If the lower u loop end of the J is elongated to about sixty feet, what differance will it make to the barometer?

M.Krishnapillai —Preceding unsigned comment added by 124.43.251.138 (talk) 06:59, 16 February 2008 (UTC)[reply]

I'm not certain if I understand your question, but I believe that extending the open side of a water barometer will make no difference. Perhaps our article on barometers may help. (EhJJ)^TALK 22:32, 16 February 2008 (UTC)[reply]

You will be measuring the pressure of the air from a different point, Although the extra weight of the air in the tube will largely compensate, the difference in air pressure inside the tube and outside could be due to different temperatures, or humidities, or due to wind, sound etc. Graeme Bartlett (talk) 03:33, 18 February 2008 (UTC)[reply]

Cowling nozzle?

Watching mythbusters today, when they tried to make a jet pack with 2 props and cowling, they didnt get enough lift. I would've thought that to get more lift, you could focus the air more by creating more of a nozzle effect, by narrowing the diamter after the prop instead of having it the same all the way down. Is there a technical reason why they couldnt do this? —Preceding unsigned comment added by 59.100.252.244 (talk) 12:53, 16 February 2008 (UTC)[reply]

How much elecricity does an solar panal of a sq mts produce.

Hello i am thinking of making a paper presentation on a way of producing power by concentrating mirrors and i want to know how they fare with solar panals .I would also like to know about there efficiency,cost etc.--Man manoj1990 (talk) 13:09, 16 February 2008 (UTC)[reply]

The article on Solar_radiation contains a number of estimates of how much solar energy arrives at the earth. The article on photovoltaics has a discussion of efficiency. JohnAspinall (talk) 04:54, 17 February 2008 (UTC)[reply]

Positive and negative load tests

G'day, RefDeskers. I'm stuck with something. I have come across the phrases positive load test and negative load test with reference to railway sleepers. I'm not seeking to learn the methodology of such tests, this is irrelevant - what interests me is the relevance of the terms positive and negative here. How do both of these tests differ and why the differentiation? If anyone has any ideas, I'd appreciate them. Thanks and cheers! --Ouro (blah blah) 13:42, 16 February 2008 (UTC)[reply]

Try this paper http://ro.uow.edu.au/cgi/viewcontent.cgi?article=1321&context=engpapers (look at figure 1) - can this be the answer. (the loads are 'moments' ie torque..)?77.86.8.83 (talk) 13:58, 16 February 2008 (UTC)[reply]

Makes me scratch my head, this diagram you pointed me to... could anyone briefly explain further? --Ouro (blah blah) 14:49, 16 February 2008 (UTC)[reply]

A railway sleeper somewhat works like a beam in a framed building structure. Such a beam is subjected to pressure (positive) in the top part and tension (negative) in the bottom part. In a typical reinforced beam the concrety bits cope with the pressure whilst the steel reinforcement takes up the tensile forces.

I assume that sleepers, being subjected to 2 point loads at the locus of the tracks, have similar characteristics of positively and negatively stressed parts, which have to be mathematically analysed to provide steel reinforcement in the zones of tensile forces. The article from the Wollongong University seems to indicate that significant tensile stress is measurable in the top part of the middle section of the sleeper.

There is a stack of suitable articles under the lemma structural analysis. Prost, --Cookatoo.ergo.ZooM (talk) 01:53, 17 February 2008 (UTC)[reply]

Goodness me. But thanks for youe explanation, ZooM! --Ouro (blah blah) 09:27, 17 February 2008 (UTC)[reply]

Deep space travel - Voyager and Pioneer

Are the Voyger and Pioneer space probes travelling particularly fast? That is, would it be hard, using exisiting, proven technology, to make a similar space probe travel ten times as fast as these probes? ike9898 (talk) 14:33, 16 February 2008 (UTC)[reply]

"Voyager 1 is departing the Solar System at a speed of 39,000 miles per hour. Voyager 2 is departing the Solar System at a speed of 35,000 miles per hour." http://www.spacetoday.org/SolSys/Voyagers20years.html

I have literally no idea about this stuff so couldn't say with any authority if faster speeds are possible but i suspect that the pace these things are travelling is not something that is controllable/could be changed in any meaningful way by modern technology design. ny156uk (talk) 14:38, 16 February 2008 (UTC)[reply]

Oh and Pioneer details on that page..." Accelerating to a speed of 82,000 mph, Pioneer 10 passed by Jupiter on December 3, 1973. so my assumption about speed is obviously wrong. (http://www.spacetoday.org/SolSys/ThePioneers.html) ny156uk (talk) 14:42, 16 February 2008 (UTC)[reply]

(ec) Well, let's see. Voyager I is travelling at 17,2 km/s relative to the Sun, Voyager II is supposed to be travelling 10% slower, so say about 15,5 km/s, and Pioneer 11 is travelling at 11,6 km/s, and Pioneer 10 is unfortunately unreachable. Now, say we increase tenfold the speed of Voyager II, giving ca. 150 km/s. As I read, one of the Helios probes reached around 70 km/s, a current record for a man-made object. Deep Impact reached velocities in the low twenties per second. So, we're not quite there yet actually, but ion thrusters promise certain advances. Also, keep in mind that probes tend to rely not only on engines for their speed, but also gravitational slingshots. Hope I helped a bit. --Ouro (blah blah) 14:48, 16 February 2008 (UTC)[reply]

Voyager can cross the galaxy in like 60 years or something x_X :D\=< (talk) 04:52, 19 February 2008 (UTC)[reply]

can we reabsorb water from the bladder?

Once urine is in the bladder, can the body reabsorb it if it needs it? Say, if you were dumped into the desert with a full bladder would you be better off to 'hold it' so your body could use it later? 216.77.239.212 (talk) 15:05, 16 February 2008 (UTC)[reply]

The bladder is unable to reabsorb urine. If the bladder was able to reabsorb what would be the purpose of the kidneys, how could the kidneys control the hydration of the body is the urine was reabsorbed. One of the problems of an enlarged prostate gland is the inability to pass urine at will. This causes a build up of pressure in the bladder which if unresolved will result in back pressure on the kidneys. If you are in the desert with a full bladder it would be more sensible to pass the urine into a container and possibly seek a method to distil the water out for reconsumption. I'm assuming a certain desperation here. Richard Avery (talk) 16:23, 16 February 2008 (UTC)[reply]

Stillsuits! --Ouro (blah blah) 16:53, 16 February 2008 (UTC)[reply]

However, some people have survived without water by peeing and then drinking their own urine, yes urine is drinkable but at least it is your own urine. Hope this helps. Thanks. ~A H 1^(TCU) 17:27, 16 February 2008 (UTC)[reply]

Though there's only a limited amount of times that will work, of course, without an external water source. --98.217.18.109 (talk) 19:24, 16 February 2008 (UTC)[reply]

Maybe you should source this as from the little knowledge I have of extreme survival it is a bad idea to drink your own urine. On the impermeability of bladders, apparently there is a rise in cases of ruptured bladders in Europe that goes with the increase of the consumtion of beer and this especially for female drinkers as they have a smaller bladder. The scenario goes as follows: drink, to drunk to feel the need to pee, fall, rupture bladder. So if you drink beer, remember to pee! 200.127.59.151 (talk) 23:38, 16 February 2008 (UTC)[reply]

Drinking_urine#Survival APL (talk) 10:33, 17 February 2008 (UTC)[reply]

Seems unlikely 200.127, as drunk people with full bladders tend to just wet themselves. 79.66.116.27 (talk) 18:18, 17 February 2008 (UTC)[reply]

(unindent) thanks for this info, I wasn't really concerned about getting drunk and deserted in the desert. I did think though that the bladder membrane might be water permeable, which I think Richard answered, afaict. thanks Tim (talk) 00:23, 17 February 2008 (UTC)[reply]

A source is needed for the claim of females having smaller bladders. I have known females who could drink far more than males without needing to void urine. Edison (talk) 02:41, 17 February 2008 (UTC)[reply]

I don't know about smaller bladders but here is about overindulging [3]. 200.127.59.151 (talk) 18:48, 17 February 2008 (UTC)[reply]

toads and frogs can, however. Gzuckier (talk) 01:47, 21 February 2008 (UTC)![reply]

Reverse engineering in baking

I've found a type of bun, sold commercially, that is heavenly. It's cinnamon- and apple-flavoured, and I would like to know how I may proceed to make these on my own. They are awfully expensive - £4 for 8x bitesize. Can one reversely engineer these and find the recipe? Thank you immensely. 81.93.102.185 (talk) 16:53, 16 February 2008 (UTC)[reply]

Are maybe ingredients listed on the packaging? --Ouro (blah blah) 17:21, 16 February 2008 (UTC)[reply]

Beyond apple, sugar, apple-and-cinnamon fillings (detailed description) and the next 20 ingredients and E-substances, it doesn't lend much of a hint. I am wondering if actual tests can be done on the bun to show its amount of e.g. flour, eggs, everything. 81.93.102.185 (talk) 17:39, 16 February 2008 (UTC)[reply]

I guess one could try to estimate the ingredients from the results, but it'd be way more costly than buying them every day fresh. Oh, but if you have the ingredients and e-substances you're not that bad off. --Ouro (blah blah) 17:46, 16 February 2008 (UTC)[reply]

The proportion of the most basic ingredients (flour, eggs, water, yeast) is reasonably fixed, and a simple Google search for a recipe will yield satisfactory results (different will mostly affect the texture and consistency more than the flavour). A lot of those other ingredients, particularly the E numbers, are there because it's a commercial product - they're stabilisers and preservatives that are needed because it needs to have a factory-to-you time of a week or more. That's the big difference between stuff you bake at home and baked goods you buy from the supermarket - the home baked stuff takes incredible for the first 12 hours or so, but very quickly deteriorates. I think you'll get nice results just baking a basic bun with the normal basic ingredients. You might find that it doesn't taste appley-enough; if so, try making a reduction from apple juice and using that in place of some of the water the recipe calls for. -- Finlay McWalter | Talk 17:52, 16 February 2008 (UTC)[reply]

A recipe is more than an ingredients list. I'm no expert on baking, but I believe that the heavenliness (or lack thereof) of baked goods is based at least as much on technique as on raw chemical composition. No amount of reverse engineering, or mass spectrometry (or whatever) is going to tell you how finely or coarsely the shortening was cut in, or how long the dough was kneaded, or how long it sat between kneadings, or at what rate various amounts of liquids (some of which, of course, evaporated later) were added. For that, you're either going to have to suborn an employee at the bakery, or do lots of experimenting yourself. —Steve Summit (talk) 19:43, 16 February 2008 (UTC)[reply]

If the dough and sweet mix are separated in swirls, then the sweet mix will almost certainly contain apple or (even nicer) pear concentrate. Also, using apple varieties suited to cooking helps. I used to bake these. Polypipe Wrangler (talk) 21:22, 16 February 2008 (UTC)[reply]

You could always ask the bakery for the recipe: they might not consider it a trade secret. Of course, even if they give it to you, it might turn out to require equipment you don't have at home. [And then there's this hazard. :-)] --Anonymous, 22:19 UTC, February 16, 2008.

You might wish to seek out Saigon cinnamon, since it has greater aroma than other varieties in the baking. One source listed in the article is [The Spice House]. The cinnamon is the essence of the baked good, and compared to premium freshly ground spice, the spices sold in little jars or tins in the grocery store are pale imitations. [User:Edison|Edison]] (talk) 02:34, 17 February 2008 (UTC)[reply]

Why do some people turn green when they get sick?

I have searched the internet on this subject and not seen anything of use. Recently my daughter (white, slightly olive coloured skin) was ill and she definitely had a greenish cast to her skin. Our family are curious to know what causes the green colour. She was feeling dizzy so may have had blood drain from her face to the part of her body that needed help. Why is the resulting hue green? —Preceding unsigned comment added by 124.197.36.202 (talk) 20:29, 16 February 2008 (UTC)[reply]

We discussed green skin on the Miscellaneous desk last month (here and also here), but I guess we didn't consider the illness angle much. —Steve Summit (talk) 21:53, 16 February 2008 (UTC)[reply]

This confirms your observation in a turn of phrase "looking green around the gills" meaning someone looks like they're about to be sick[4] and google came up with green bile in the erm, vomit, but nothing about the skin's appearance except that it can refer to someone looking pale before they er (excuse me...) Julia Rossi (talk) 11:56, 17 February 2008 (UTC)[reply]

FWIW I reckon it is just reduction in blood. If you reduce the red component from skin colours they often turn greenish. --BozMo talk 12:56, 17 February 2008 (UTC)[reply]

February 17

Carbonyl reduced to Hydroxyl

I understand that reduction is a gain of electrons and oxidation is a loss of electrons. But I don't understand how when a carbonyl is turned into a hydroxyl it was reduced. To me the number of electrons stayed the same in the functional group before and after. There were no gains or losses of electrons. Could someone explain this to me? 128.163.224.198 (talk) 00:29, 17 February 2008 (UTC)[reply]

It's a reference to the oxidation state of carbon, specificially. Whereas previously the oxygen-bound carbon (in the case of a ketone) was considered to have an oxidation state of +2, it now has an oxidation state of 0. Someguy1221 (talk) 00:34, 17 February 2008 (UTC)[reply]

If you're dealing with biochemical (aqueous) systems, here's another way to think about it: To start with, you have the carbonyl and an available pool of H⁺ ions from the water. In order to go from the carbonyl to the hydroxyl, you have to add two protons and two bonds (one each to both the carbon and the oxygen). To make the bonds, you need four electrons (two for each bond). Two electrons come from the C=O double bond that you "break" into a single bond, so you need to add in an additional two electrons for the second bond. -- 128.104.112.47 (talk) 19:13, 19 February 2008 (UTC)[reply]

Sleeping standing up

Are there humans who sleep standing up? I think that leaning on a corner it would be feasible at least.217.168.1.250 (talk) 00:58, 17 February 2008 (UTC)[reply]

It's not possible without an adequate means of support.The Updater would like to talk to you! 01:03, 17 February 2008 (UTC) —Preceding unsigned comment added by WikiHaquinator (talk • contribs) [reply]

If I can sleep sitting up, or sitting at my desk at work, I can probably sleep leaning against something. But unlike cattle, I do not believe humans can lock their knees and sleep while standing unsupported. Micronaps would occur if a person were sleep deprived long enough, but they would jerk as they started to fall. Edison (talk) 02:33, 17 February 2008 (UTC)[reply]

I could see it happening if someone had some sort of back problem that prevented him/her from laying down, with supports of course. Clarityfiend (talk) 04:56, 17 February 2008 (UTC)[reply]

Astronauts of course can sleep in any orientation, but in orbit there is no differential apparent force on a person distinct from that on the space craft, so there is no up/down. That said, astronauts do have preferences for which way in their sleeping bags they lie (head/feet up/down) but this is just preferences to which way the tethers and zips are orientated to them. Still it does look somewhat bizarre seeing one astronaut giving a video linkup tour of their living quarters, to then see one of there colleagues unzip from a sleeping bag in an opposite orientation. David Ruben ^Talk 13:28, 17 February 2008 (UTC)[reply]

Well, we would not stand unsupported, so we don't have to lock our knees. Imagine that you are on a corner facing it. You can lean your knees and lean your head on the corner. I'll try this at home and come back to you. 217.168.3.246 (talk) 20:35, 17 February 2008 (UTC)[reply]

(OR warning). It's possible to fall asleep standing up, but you tend to wake up fairly soon! A kind of semi-doze can be maintained for some time while clinging to one of those handle-strap things on a bus or train. And I've seen children soundly asleep clinging to a parent's leg or similar. And, of course, there are somnambulists who manage the whole upright thing quite well. Gwinva (talk) 22:01, 17 February 2008 (UTC)[reply]

Electron microscope staining

hey,

Is it possible to stain cells for observation under electron microscope? The Updater would like to talk to you! 01:02, 17 February 2008 (UTC)[reply]

It is not necessary to stain a cell for veiwing with an electron microscope. The cell must be coated with a thin layer of metal (Usually gold I think) to reflect the electrons so an image can be created. It may also be helpful to see electron microscope. --Zrs 12 (talk) 01:27, 17 February 2008 (UTC)[reply]

Variable Speed of Light

I was recently reading a scientific paper written by one of my teacher's uncles on his theory about light having a varying instead of constant speed. First, he set some units: $9.8m/s^{2}=1\,\!$ , by Newton's equation $F=ma\,\!$ and defining $9.8m/s^{2}\,\!$ as the acceleration $m=F/g\,\!$ . Also, defining gravity is $L/s^{2}\,\!$ in which $L=9.75m/s^{2}\,\!$ . He then says therefore, $m={\frac {F}{1}}$ so $m=F\,\!$ . Then he says Length is L, mass is F, t is time, and so $c={\frac {L}{t}}$ . He says work is mass multiplied by Length and energy is the rate of performing work so Newtonian energy is $E={\frac {mL}{t}}$ . He then says using the relativity equation $E=mc^{2}\,\!$ we need to define mass. Since Newtonian mass is ${\frac {Et}{L}}$ the relativity equation is as follows: $E=\left({\frac {Et}{L}}\right)\left({\frac {L}{t}}\right)^{2}$ . He says when simplified this equation shows time is Length. My questions are:

How did he get $c={\frac {L}{t}}$ (this appears to be just an assumption to me)
Is there anything wrong with his logic? and,
When I simplified the equation $E=\left({\frac {Et}{L}}\right)\left({\frac {L}{t}}\right)^{2}$ I distinguished between Einstenian and Newtonian energy and reformulated the equation to $E_{E}=\left({\frac {E_{n}t}{L}}\right)\left({\frac {L}{t}}\right)^{2}$ and when it was reduced I got ${\frac {E_{E}}{L}}={\frac {E_{n}}{t}}$ showing (it appears to me) that $L\neq {t}$ or at least $L=t\Leftrightarrow {E_{n}}=E_{E}$ for the fact that Einstenian and Newtonian energy are different. Who is correct? Does $L=t\,\!$ in fact?

Thanks, Zrs 12 (talk) 01:54, 17 February 2008 (UTC)[reply]

Showing ${\frac {E_{E}}{L}}={\frac {E_{n}}{t}}$ : ${\begin{aligned}E_{E}&=\left({\frac {E_{n}t}{L}}\right)\left({\frac {L}{t}}\right)^{2}\\&={\frac {E_{n}tL^{2}}{Lt^{2}}}\\&={\frac {E_{n}L^{2}}{Lt}}\\&={\frac {E_{n}L}{t}}\\\end{aligned}}$ ${\begin{aligned}\textstyle {therefore}\\\end{aligned}}$ ${\begin{aligned}{\frac {E_{E}}{L}}={\frac {E_{n}}{t}}\\\end{aligned}}$

Zrs 12 (talk) 05:14, 17 February 2008 (UTC)[reply]

ATTENTION: I accidentally put (L/t²). Now it's correct as (L/t)². Sorry. Zrs 12 (talk) 03:31, 17 February 2008 (UTC)[reply]

The theory starts out with gibberish, because if

9.8m/s^{2}=1\,\!

, then in dimensional analysis length equals time squared, which is nonsense. Edison (talk) 02:30, 17 February 2008 (UTC)[reply]

Anything else? (Remember, he is trying to prove that the speed of light is variable so maybe length does equal time squared?) Zrs 12 (talk) 02:56, 17 February 2008 (UTC)[reply]

Except that he didn't prove that length equals time squared, he just sort of declared it, and this seems to form the basis of the rest of the proof. Someguy1221 (talk) 03:19, 17 February 2008 (UTC)[reply]

Ok, thanks. What about the part where I showed

L=t\Leftrightarrow {E_{n}}=E_{E}

? Did I do this correctly or did he? In other words, did I reduce correctly? --Zrs 12 (talk) 03:24, 17 February 2008 (UTC)[reply]

The whole thing is basically gibberish. It's the mathematical trappings of high school physics without any of the physics. It's hard to know how to respond to your questions because you might as well be analyzing Star Trek technobabble. Have you correctly followed the procedure for realigning the tachyon compensators? Well, maybe, maybe not; only your teacher's uncle can say. -- BenRG (talk) 20:36, 17 February 2008 (UTC)[reply]

This is too physics heavy even for the likes of me ;) kidding. Seriously though, the only time the speed of light is not constant is when it passes through a medium, any medium that is not a vacuum. At least that's the extent of what I know regarding this. That's really all I can say about the above since it's mostly mathematical vomit. That's not a personal attack. It's just a really convoluted way to ask a question. Wisdom89 _{(_T / ^C)} 20:58, 17 February 2008 (UTC)[reply]

Not to defend the uncle (I neither know nor care about the above), but 1. there are variable speed of light theories put forward by competent physicists, so dismissing that aspect of it a priori is a little presumptive, and 2. the simple manipulation of simple equations to reach unintuitive results has been done successfully before by none less than Einstein (the 1905 papers on special relativity are basically this—taking a few very well-known equations and trying to make them be compatible with each other in ways that hadn't been done before, specifically combining Galilean relativity with the axiom of a fixed speed of light in a vacuum, and the rest basically falls out from there), so that's not a great reason to dismiss it either. The original derivation of E=mc^2 does not use complicated physics at all; special relativity as a whole is extremely simple "high school" math (Einstein's emphasis was on axioms and concepts; he had to learn a lot of math before he could generalize the theory, however). However it is unlikely that one's uncle is going to do better than Einstein in that game, which would for me be a pretty strong a priori source of doubt, though it is no proof. --98.217.18.109 (talk) 21:40, 17 February 2008 (UTC)[reply]

The first warning sign that something dubious is going on is the use of

g

, the local gravitational acceleration at the surface of the earth, in a theory about light. Any theory about light has to account for the fact that light travels throughout space (i.e. we see stars). Why would the behavior of light throughout the universe depend on the local amount of gravity at the surface of the third planet orbiting an unremarkable G-class star, in the Orion arm of the Milky Way Galaxy? JohnAspinall (talk) 00:47, 18 February 2008 (UTC)[reply]

I kind of thought so. He had but 56 semester hours of math in college. Also, he is a chemical engineer, not a physicist, so it doesn't really suprise me that it seems to be "gibberish". Thank you all, Zrs 12 (talk) 00:33, 18 February 2008 (UTC)[reply]

Engineers of various sorts seem to be the ones behind a lot of this kind of speculation. Physics department around the country have "crank files" of people who write in to dispute or put forward various theories; engineers, in my experience in reading these files (which I have done on a few occasions), seem to go for this stuff the most. I imagine it has to do with their type of education—something that makes them feel quite technically competent but they actually lack a lot of the lower-level understanding that is superfluous for their profession. But that might be an exaggeration. --98.217.18.109 (talk) 02:49, 18 February 2008 (UTC)[reply]

Does your uncle happen to have some underlying reason to want the speed of light to be variable? Wanting to arrive at a desired result can certainly lead people to accept some tortured logic. --Sean 14:52, 18 February 2008 (UTC)[reply]

I haven't a clue. (He's my teacher's uncle) Anyway, this very well may be the case. However, in his memo on the subject, there was no indication of this. This could possibly be the case though. Zrs 12 (talk) 23:10, 18 February 2008 (UTC)[reply]

Speculative Science Question

I was watching a Twilight Zone episode,A Kind of a Stopwatch, the other day. In it, a man gains the ability to "stop time." Objects freeze in midair, people don't move, and none of it affects him. My question is this: If such a thing were possible, then wouldn't he die? Would he be able to breathe the "stopped" air molecules? Would he be able to walk through said molecules? —Preceding unsigned comment added by 192.136.22.4 (talk) 02:04, 17 February 2008 (UTC)[reply]

I can't believe I'm answering this......it's a narrative fiction, you're supposed to just accept the premise as a given, and not examine it too closely, lest you ruin the story. Nevertheless, as I recall it, the protagonist is able to move objects, even though the objects don't move under their own force. So he ought to be able to breathe, eat, move, etc. - Nunh-huh 02:11, 17 February 2008 (UTC)[reply]

Actually, if he has reset the velocities of all the air molecules to 0, there would no longer be any air pressure, and he would not be able to breathe. When you breathe in, you are simply expanding the volume of your lungs and permitting the air molecules to move into a new location. He would need to push the air into his mouth. — BRIAN0918 • 2008-02-17 16:15Z

Yeah just accept sci-fi. In Star Wars sound can be heard even though there is no medium through which sound waves can travel. Zrs 12 (talk) 02:15, 17 February 2008 (UTC)[reply]

Seen this before. There is an old (say 1970) Arthur C Clarke story where a jewel thief is given a device which stops everything more than a couple of metres away from him (or accelerates everything closer). That kind of works a bit. The story is interesting because it begs the question what would you do if you had all the time in the world. Crime? Revenge? Assasination? Sadly once you become a parent the only answer has to be "sleep". --BozMo talk 07:45, 17 February 2008 (UTC)[reply]

Except you'd still suffocate in your sleep since you'd basically be in a 2 metre bubble of air which would run out of oxygen :-P Nil Einne (talk) 18:53, 17 February 2008 (UTC)[reply]

When Isaac Asimov wrote the novelisation of Fantastic Voyage he addressed some of the basic physics which the screenwriters hadn't troubled with - for example (IIRC) when they're running out of air they tunnel into the lungs to get some, but in the book he actually had them shrink the air from the lungs. --ColinFine (talk) 21:31, 17 February 2008 (UTC)[reply]

Reading a more realistic sci-fi story some time ago, I've seen a solution for this kind of problem: the protagonist had to hold his breath while he was using his superpower. This way, the whole story was a bit more balanced, he could use his "power" only for around a minute. The power was to pass through matter and/or become invisible, but this "solution" can also be applied to the power of slowing down time. --V. Szabolcs (talk) 18:50, 18 February 2008 (UTC)[reply]

Yeah, has any one heard the story of how nothing exploded into everything and then life some how started from nothing. That means spontanious generation. Pretty far out huh!

Use of Opiates in the treatment of psychiatric disorders in women!

Question is about medical/chemical applications re wife's treatment. This questioner is reminded: Do not request medical or legal advice. Any such questions may be removed. If you need medical or legal advice, do not ask it here. Ask a doctor, dentist, veterinarian, or lawyer instead. See your doctor. Julia Rossi (talk) 08:49, 17 February 2008 (UTC)[reply]

I'd like to add that if you do not agree with your wife's psychiatrist, you (as a couple) could consult a different psychiatrist. Generally, if you get a few "no, we don't do that" responses from several unrelated physicians, it's probably the best way to go (versus asking a bunch of non-medically trained, anonymous volunteers on the internet). Also, feel free to read our article on hydrocodone if you'd like to be an "educated patient", but use that information only to help you ask your doctor the right questions. (EhJJ)^TALK 21:16, 17 February 2008 (UTC)[reply]

absorption

Intensity of light decreases with the rise in concentration of the liquid through the light passes through: please explain this in detail.Jskirankumar (talk) 09:34, 17 February 2008 (UTC)[reply]

Beer's law. Someguy1221 (talk) 09:44, 17 February 2008 (UTC)[reply]

Photoreceptors

Hi all I am usure as to how a rod/cone cell become hyperpolarised. I know that when a photoreceptor such as a rod is resting K+ ions leak out of the inner segment and Na+ ions diffuse in through the outer segment. When a rod is stimulated the Na+ channels close but the Sodium/Potassium pump continues to pump Na+ ions out and K+ in. I'm not sure how this makes the charge go from -40mv to -70mv. Hope this makes sense and please correct me if anything I have written is wrong! —Preceding unsigned comment added by 172.207.224.229 (talk) 10:49, 17 February 2008 (UTC)[reply]

If I'm not mistaken, the channel lets 3 Na+ go out and then 2 K+ in. So in net total, +1 goes out of the cell, and the inside of the cell becomes more negative..206.240.25.247 (talk) 13:34, 17 February 2008 (UTC)[reply]

When rods are stimulated by photons, the signaling mechanism that is elicited activates cGMP phosphodiesterase which depletes and inacticates cGMP, stopping the depolarization due to sodium ions influx. Since the resting membrane of the cell is closer to the equilibrium potential of potassium, the cell hyperpolarizes. Wisdom89 _{(_T / ^C)} 20:42, 17 February 2008 (UTC)[reply]

Why is there more static electricity in dry weather?

I wonder. 206.240.25.247 (talk) 13:30, 17 February 2008 (UTC)[reply]

I think the water vapour can bring the static electrictiy away. Visit me at Ftbhrygvn (Talk|Contribs|Log|Userboxes) 14:09, 17 February 2008 (UTC)[reply]

How does that work exactly? 206.240.25.247 (talk) 14:11, 17 February 2008 (UTC)[reply]

From reading several articles on electrostatic discharge, it seems that humidity tends to limit the electrostatic buildup because it makes surfaces slightly conductive, which provides a path for separated charge to recombine. (See [5] for a list of links on ESD. [6] contains animations of the process of tribocharging, in which surfaces of dissimilar materials become charged after contact, friction/pressure, and then separation. [7] explains the connection between humidity and "return current".) --71.175.22.137 (talk) 15:05, 17 February 2008 (UTC)[reply]

See the section "Simple experiments" in the Static electricity article. The preface notes that a humid atmosphere provides a conducting path for the rapid neutralization of static charge... --hydnjo talk 19:50, 17 February 2008 (UTC)[reply]

absortion1

why does the distance that the light travels through the material also effect the intensity of the light when the concentrator is constant? I shall be thankful for your convincingJskirankumar (talk) 16:45, 17 February 2008 (UTC) explanation[reply]

Assuming that the medium is homogeneous (i.e. uniform), you'd expect light to be attenuated by the same amount every time it travels through a unit distance in the medium. For concreteness, let's say

(intensity of emergent ray) = α × (intensity of the incident ray).

After traveling

L

unit-length layers of the medium, you'd expect the emergent ray to have an intensity of

\alpha ^{L}

× (intensity of the incident ray).

--71.175.22.137 (talk) 17:38, 17 February 2008 (UTC)[reply]

If a helium filled airship wants to gain altitude...

How does it do this? Lift is determined by how much helium gas it has, so how can they make it fly higher, when they are already at a given altitude? Malamockq (talk) 20:21, 17 February 2008 (UTC)[reply]

The density of a gas can be decreased through heat - this would allow the craft to gain altitude. Wisdom89 _{(_T / ^C)} 20:32, 17 February 2008 (UTC)[reply]

So similar mechanism to a hot air balloon then. Thanks. Malamockq (talk) 20:44, 17 February 2008 (UTC)[reply]

Yup, you got it. Wisdom89 _{(_T / ^C)} 20:54, 17 February 2008 (UTC)[reply]

No, that's wrong. They couldn't burn anything inside the helium bag because anything they piped into the bag to burn, as well as its reaction products, would be heavier than helium and would weigh the ship down. Heating the outside of the bag is theoretically possible but it would be slow to act since the heat won't transfer efficiently to the mass of helium. And the remaining choice, an electric heater inside the bag, would require a heavy power source.

There are actually three solutions that were used in the heyday of airships (whether hydrogen- or helium-filled, doesn't matter).

The first and simplest is that when you take off, you carry something heavy on board as ballast, and when you want to make the airship lighter, you drop it. If you've seen pictures of hydrogen or helium passenger-carrying balloons, you'll note that the passenger gondola is typically ringed with sandbags. (You drop the sand, not the whole bag!) With an airship the preferred ballast is water for several reasons: it's cheap and widely available; it can be loaded with a pump and a hose; nobody will mind much if some of it lands on them; and it can be used to supply the onboard washbasins and recaptured (into a second set of ballast tanks) from the drains. The Graf Zeppelin, for example, carried about 12 tons of water ballast. (If they started to run low on ballast, this would be an emergency situation the same as running low on fuel, and they would land as soon as possible to replenish it.)

The second way is the same way that an airplane does it: by pointing the nose higher or by moving control surfaces in the tail. Of course, this only works when the engines are exerting enough force to keep the vehicle moving forward at sufficient speed.

I slipped up here. The use of the tail control surfaces, as in an airplane, would be for the purpose of pointing the nose higher, not to provide increased lift directly (since it would be off-center). Pumping ballast toward the rear of the airship would be a second way to lift the nose. --Anon, 06:02 UTC, Feb. 19.

The third way is to burn some fuel, assuming that something like ordinary gasoline or diesel fuel is used. Of course, this is slow to act, but you have the burn the fuel anyway to keep moving. Now most airships have used a single type of fuel and no way to burn it except in the engines, so they had little control over this way of affecting their weight, but the Graf Zeppelin was an exception. It carried two types: Blau gas, which was a propane-based gas mixture about the same weight as air, and gasoline. If it was desired to make the airship gradually lighter, they would burn gasoline in the engines; if not, they would burn Blau gas.

Source: The Golden Age of the Great Passenger Airships: Graf Zeppelin & Hindenburg by Harold G. Dick with Douglas H. Robinson, 1985, Smithsonian Institution, ISBN 0-87474-364-8.

--Anonymous, 23:35 UTC, February 17, 2008.

Interesting, I had a feeling this was the case. For example, if the airship was filled with hydrogen, it wouldn't be very smart to try and heat it, considering it is flammable. Malamockq (talk) 02:37, 18 February 2008 (UTC)[reply]

It is possible to heat helium without igniting it. One doesn't have to use a direct flame or combustion. Just saying. Wisdom89 _{(_T / ^C)} 09:38, 18 February 2008 (UTC)[reply]

I know that, but in airships they can also use hydrogen. Heating hydrogen to make it gain altitude prolly isn't a good idea, nor how they do it. Malamockq (talk) 16:39, 18 February 2008 (UTC)[reply]

Question : Why is it not possible to change the buoyancy of one of the gasbags by pumping the gas into and out of rigid tanks? APL (talk) 01:14, 19 February 2008 (UTC)[reply]

I think this has been discussed before, in an extreme form. If you could really do that, you wouldn't need any gas -- you'd just evacuate the tanks and off you go floating into the wild blue yonder. But no one knows how to make taks that rigid, without adding more weight than the weight of the gas. Your suggestion seems like a compromise somewhere in the middle -- my guess is it won't work either, for the same reason, but I haven't tried to run the numbers. --Trovatore (talk) 01:30, 19 February 2008 (UTC)[reply]

On second thought maybe I misread your question. I thought you wanted to make the gasbags themselves rigid. Maybe you're saying, when you want to lose altitude, pump some of the helium into a tank so that the bag partially deflates. I suppose that works in principle. Would probably use a lot of energy though, and it might be awkward to have the size of the bag change in flight. --Trovatore (talk) 02:47, 19 February 2008 (UTC)[reply]

Yes, that is what I was asking. I was not asking about the mythical Vacuum Blimp. I was asking about slightly deflating the gasbags without completely venting the hydrogen. Seems like depending on the type of airship, it wouldn't be that awkward to have the bag change in flight. Even if you completely deflated a gasbag on a Zepplin the envelope would presumably stay the same shape. APL (talk) 04:18, 19 February 2008 (UTC)[reply]

Well, I'm no airship engineer; I can't say whether there's some way the idea could be made to work (better than the alternatives). But I would note that there's still an uncomfortable tradeoff: If you make the tanks small, then in addition to having to make them very strong, you'll have to supply a lot of energy to compress the gas into them (integral of pressure wrt volume). Whereas, if you make them big, they'll be heavy, and you have

to lift them with the gas you're planning to put into them. --Trovatore (talk) 04:54, 19 February 2008 (UTC)[reply]

Sanity check: Either A) the gasbag is rigid (doesn't change size), in which it has a constant volume, and moving mass (with weight) between the gasbag and a similar rigid pressure tank doesn't change the total volume of the system, or total mass either, so there is no effect to overall bouyancy. Or, B) the gasbag is NOT rigid, meaning that as you pump gas into it, it expands to keep the same pressure as the outside air. Which means that as gasbag total mass increases, the total volume increases, too. Again, you don't gain anything.

The only way to gain something is to either change total airship volume, while keeping mass constant, or change total airship mass, while keeping volume constant. Note that hot air balloons do the latter - they heat the air, which expands out the bottom, making the whole balloon mass less while keeping the volume the same => it will rise. To descend, just let it cool off. The air will contract, and more are will come in the bottom, for more mass at the same volume.

The "right way" would certainly be to have rigid gasbags that we could pump down to a vacuum while they kept their size/shape, but that means a lot of structural strength, which, ahem, would make them too heavy to lift. -SandyJax (talk) 17:29, 19 February 2008 (UTC)[reply]

No, you missed a point in alternative (B): It's true that the weight of bag-plus-gas is increasing, but the weight of storage-tanks-plus-gas is decreasing by the same amount (not counting relativistic effects :-). So you do in fact gain buoyancy when you move gas from the rigid tanks into the inflatable bag, and decrease buoyancy when you move it the other way. Whether this is a good, or even feasible, design, is another question, but it does work in principle. --Trovatore (talk) 20:29, 19 February 2008 (UTC)[reply]

SandyJax, I think you misunderstood. I was suggesting changing the total displaced volume of the airship by inflating and deflating the gasbags while recapturing the gas in pressurized, rigid holding tanks for reuse, keeping mass constant. (total displaced volume should not be confused with total enclosed volume when talking about rigid frame ships like Zeppelins.) However, Trovatore has satisfied my curiosity by convincing me that my idea would require some pretty heavy equipment that would probably take up a pretty large percentage of the airship's carrying capacity. APL (talk) 05:38, 20 February 2008 (UTC)[reply]

Absolute frame of reference

According to the special theory of relativity there is no absolute frame of reference. But something bothers me. The kinetic energy of an object is 1/2 m v^2

For an object of 2 kg.

To get from 0 m/s to 1 m/s requires 1 joule of energy.

to get from 100 m/s to 101 m/s requires 201 joules of energy.

So why can you measure the amount of energy required to increase the velocity of the object by 1 m/s and thus calculate how fast the object is travelling on the absolute frame of reference (which special relative claims that it does not exists).

202.168.50.40 (talk) 21:39, 17 February 2008 (UTC)[reply]

To increase the momentum of an object in one direction, you must also increase the momentum of some other object in the other direction (conservation of momentum). You cannot directly observe the energy given to either one; you can only observe the energy given to both. And this energy doesn't vary by reference frame. This is true in classical mechanics too, so for simplicity I will not deal with relativity, and give an example in one-dimensional classical mechanics:

Suppose you have two masses

m_{1},m_{2}

stuck together, moving at speed

v_{0}

. Then you have an explosion that imparts a momentum

p

to both of them in opposite directions (let's say it accelerates

m_{2}

in the positive direction and

m_{1}

in the negative direction). Then

m_{2}

will be traveling at speed

v_{0}+{\frac {p}{m_{2}}}

and

m_{1}

will be traveling at speed

v_{0}-{\frac {p}{m_{1}}}

. Now let's compute the difference in total kinetic energy of the objects before and after:

{\frac {1}{2}}m_{1}\left(v_{0}-{\frac {p}{m_{1}}}\right)^{2}+{\frac {1}{2}}m_{2}\left(v_{0}+{\frac {p}{m_{2}}}\right)^{2}-{\frac {1}{2}}m_{1}v_{0}^{2}-{\frac {1}{2}}m_{2}v_{0}^{2}

={\frac {1}{2}}\left(m_{1}v_{0}^{2}-2pv_{0}+{\frac {p^{2}}{m_{1}}}+m_{2}v_{0}^{2}+2pv_{0}+{\frac {p^{2}}{m_{2}}}-m_{1}v_{0}^{2}-m_{2}v_{0}^{2}\right)

={\frac {1}{2}}\left({\frac {p^{2}}{m_{1}}}+{\frac {p^{2}}{m_{2}}}\right)

Notice that this increase in total kinetic energy is not dependent on the initial velocity

v_{0}

. --Spoon! (talk) 23:38, 17 February 2008 (UTC)[reply]

Pitch Drop experiment

The most famous version of the experiment was started in 1927 by Professor Thomas Parnell of the University of Queensland in Brisbane, Australia, to demonstrate to students that some substances that appear to be solid are in fact very-high-viscosity fluids. Parnell poured a sample of pitch into a sealed funnel and allowed it to settle for three years.

Considering how long it takes for pitch to flow. Exactly how long did it take for Prefessor Thomas Parnell to pour the pitch sample into the funnel? 202.168.50.40 (talk) 22:56, 17 February 2008 (UTC)[reply]

According to this, he heated the pitch before pouring it in - so I assume it didn't take that long. --Kurt Shaped Box (talk) 23:15, 17 February 2008 (UTC)[reply]

How clever! —Keenan Pepper 00:30, 18 February 2008 (UTC)[reply]

You've seen our article about the Pitch drop experiment, right?

Atlant (talk) 01:52, 18 February 2008 (UTC)[reply]

Sudden tics when drowsy?

Sometimes, especially in class, if I am leaning back and attempt to sleep, parts of my body will suddenly tense. This is really uncomfortable, and I'd very much like to sleep without this happening. Is there a good article on this muscle behaviour? 81.93.102.185 (talk) 23:18, 17 February 2008 (UTC)[reply]

Perhaps you might consider attempting to sleep somewhere else than in class? You probably want to read hypnic jerk and myoclonus, but if you want more than that, please see a doctor, because medical advice is not allowed here. --Anonymous, 23:47 UTC, February 17, 2008.

I doubt that this is a medical issue so I'll provide my insight and two cents. What you are experiencing are most likely hypnic jerks upon entering into stage one of non-REM sleep. Also, strange sensations when falling asleep might be a sign of sleep paralysis, which is completely benign. Wisdom89 _{(_T / ^C)} 09:36, 18 February 2008 (UTC)[reply]

Who would win?

In a fight between a Predator and a Terminator, which would be more likely to win? --81.79.122.2 (talk) 23:40, 17 February 2008 (UTC)[reply]

Not only does this ask for speculation, it is not a science question. --Anon, 23:48 UTC, Feb. 17.

Sounds like a great idea for a movie proposal. And you get to decide! Someguy1221 (talk) 00:23, 18 February 2008 (UTC)[reply]

Predator by a mile - even though this isn't a legitimate science question. One blends into the environment and preys on a victim, while the other loafs around blindly. If you want to liken it to something in nature, how about a preying mantis verses a spider? Wisdom89 _{(_T / ^C)} 00:27, 18 February 2008 (UTC)[reply]

But human Arnold beat a Predator so therefore clearly a robot Arnold must destroy a Predator. —Preceding unsigned comment added by Shniken1 (talk • contribs) 01:21, 18 February 2008 (UTC)[reply]

You do have to remember that a Predator, while probably of approx. equal strength and speed to a Terminator, is only slightly less vulnerable to gunfire/edged weapons/fists and feet than your average human. A Terminator can absorb significantly more damage and still keep coming. If the Predator cloaked, the Terminator would probably be able to calmly track its vague outline against the surroundings (and get a target lock) just fine. --Kurt Shaped Box (talk) 01:34, 18 February 2008 (UTC)[reply]

In the AVP movies, Preds usually wear bullet proof armor on their bodies. Does a pretty good job of deflecting bullets. Terminators are still more durable despite that though. Not nearly as agile though. Malamockq (talk) 02:42, 18 February 2008 (UTC)[reply]

The Predator might come out on top if he figured out what the humans obviously seem unable to when fighting Terminators - namely that plugging away at a cyborg's heavily-armoured head and torso is *very* ineffective and instead concentrated on shooting its spindly legs out from under it. Once crippled, the Pred could take his sweet time and concentrate plasmacaster fire on the Terminator from a distance, until he managed to damage something vital. --Kurt Shaped Box (talk) 16:35, 18 February 2008 (UTC)[reply]

See answer #4 here, and substitute the strings "Predator" and "Terminator" as appropriate. —Steve Summit (talk) 01:48, 18 February 2008 (UTC)[reply]

They are evenly matched. It's all up to the writers. That's what makes "vs." stories interesting. Pitting two evenly matched opponents against each other. Having Predator vs. Galactus, wouldn't make much sense for example. Malamockq (talk) 02:40, 18 February 2008 (UTC)[reply]

Despite the speculation comment, the opinions have come thick and fast :) In the latest Requiem AVP movie, the predator takes off his armour to experience an honourable fight to the death with his opponent, much like you see in the martial arts movies where the guy who has just disarmed the other guy, throws his sword away as well. So I suppose in the predator's mind, his opponent was a respected and worthy one. Sandman30s (talk) 12:26, 18 February 2008 (UTC)[reply]

Ten bucks on Terminator. Humanity shall prevail. --Ouro (blah blah) 13:02, 18 February 2008 (UTC)[reply]

Just ask Google [8] :P --V. Szabolcs (talk) 15:35, 18 February 2008 (UTC)[reply]

February 18

Tube guitar amplifier humming/rustling sound problem

Hello, perhaps this should be in miscellaneous but it deals with the internal components of an amplifier and speaker. Yesterday I purchased a Peavey Classic 30 guitar amp, a 30-watt all tube amp with one 12" speaker, 3 preamp tubes and 4 power tubes. It sounds fine except for a few quiet rattles: sometimes the amplifier makes a very low pitched crackly rustling sound that kind of sounds like the wind blowing. It is peculiar because it happens whether my guitar is plugged in or not, and it is at the same volume no matter what the volume of the amp is. I've turned it up very loud and I've turned the volume as low as possible and the volume of this little crackling hum has not changed at all. It's very quiet and I only hear it while playing quietly or not at all but while the amp is still on. Does this problem sound familiar to anyone, if so, does anybody know what causes it and, most importantly, how to fix it? NIRVANA2764 (talk) 02:11, 18 February 2008 (UTC)[reply]

Is it a bug or a feature? I thought it was little quirks like that that made tube amplifiers attractive in the first place... —Steve Summit (talk) 02:56, 18 February 2008 (UTC)[reply]

Try "tapping" the power tubes one at a time to see if any tube "responds" as sometimes a tube can become microphonic and generate unwanted background noise. Seems like a fine piece of equipment that you've gotten, have fun and good luck! --hydnjo talk 05:51, 18 February 2008 (UTC)[reply]

Googling suggests that the Classic 30 has a spring reverb: analog reverbs are always prone to hum (from transduction and interference). Does the hum persist if you take the reverb out of the circuit (assuming the amp has a "reverb on/off" button) as opposed to just turning the reverb knob down? Depending on its design, a spring reverb can sometimes act as an antenna, capturing unwanted RF interference from neighbouring devices. Try turning off everything electrical nearby (TVs, monitors, fans, AC units, and transformers in particular). If you can't be sure the reverb is off (as opposed to just dialled down) whack the amp (gently) - a whacked spring reverb makes a horrible noise like an explosion in a scrapyard. -- Finlay McWalter | Talk 15:23, 18 February 2008 (UTC)[reply]

I've never seen that sound so eloquently described! --hydnjo talk 15:39, 18 February 2008 (UTC)[reply]

I tend to agree with that as well. Especially since I've heard both that amp sound and an explosion in a scrapyard in real life. 206.252.74.48 (talk) 20:27, 18 February 2008 (UTC)[reply]

Hydnjo is right. I know that sound, too. There is a schematic diagram here. You have a transistor or two in there, you know. I would try freeze spray on Q2, being careful not to break a tube with it or electrocute myself (tube amps bite hard). You can pull tubes one at a time (unplugging the amp and letting it sit awhile between pullings) to narrow down the circuit the noise is coming from. Don't pull an output tube. Freeze capacitors one at a time and listen. It might be normal for this amp. --Milkbreath (talk) 16:56, 18 February 2008 (UTC)[reply]

Besides microphinics in tubes, the connection between the tube pins and the socket can be imperfect due to dirt or corrosion. With the power off, wiggling the tube in the socket or removing and replacing a few times may 'wipe" the contack and improve the noise level. Volume controls are another suspect. They can be cleaned with appropriate spray (power off)or replaced. Connects and things that plug into them are the third area where imperfect contactor frayed wiring can create noise. Edison (talk) 19:55, 18 February 2008 (UTC)[reply]

Hmm. Sounds like brown noise to me caused by a noisy output stage —Preceding unsigned comment added by 79.76.226.64 (talk) 03:46, 21 February 2008 (UTC)[reply]

Since the op states that the noise is not affected by the volume control then, the noise is most likely contributed by the power amplifier section (not the preamp). (I am assuming the noise has been shown not to be coming from the reverb amp, but this could easily be checked.)

From the circuit diagram here , it appears the main voltage amplification (a few thousand times) in the power amp is provided by V3A,B (a 12AX7 double triode). I would investigate initially in this area. I'm sure I used to hear tales in the old days of faulty grid leak resistors causing noise problems. These resistors are R48 and R47 (both 1 Mohm). You could initially try tapping these gently with an insulated tool to see if they are microphonic. (Remember there are lethal voltages in this circuit). If they are noisy, then replacement of these may be in order (especially if they are carbon composition types which are known to be noisy anyway). —Preceding unsigned comment added by 79.76.226.64 (talk) 13:50, 21 February 2008 (UTC)[reply]

bug/insect identification

Can someone tell me which bug this is? http://farm3.static.flickr.com/2411/2272801999_ed19224b97_o.jpg It was about the size of a dime or a nickel. This is the underside: http://farm3.static.flickr.com/2119/2272814521_32f6c5f0b5_b.jpg Sorry for the blurriness. Thank you. --Rajah (talk) 04:08, 18 February 2008 (UTC)[reply]

Looks like a member of the Pentatomidae family. They're called shield bugs or stink bugs. This one might be the Brown marmorated stink bug, but many of the species in this family look similar. Sancho 05:51, 18 February 2008 (UTC)[reply]

Thanks! --Rajah (talk) 13:05, 18 February 2008 (UTC)[reply]

Volume of solution

Does the volume of water change when NaCl is added to it? What about solutions in general? Does the volume of solution change when solute is added to solvent? Kushal 13:06, 18 February 2008 (UTC)[reply]

In general, the volume of a solution changes when solute is added. That's why, for example, a molar solution is always prepared by putting the solute in the flask first, rather than starting off with a known volume of solvent and adding the solute. MrRedact (talk) 16:40, 18 February 2008 (UTC)[reply]

Yes, the volume of water changes when dissolving solutes as (in your example for instance) the NaCl displaces water molecules. Wisdom89 _{(_T / ^C)} 18:49, 18 February 2008 (UTC)[reply]

By changing, I think you mean increase, it's important to realize that there some solutes which will decrease the volume of the solution. This is a particular chestnut of many physical chemistry courses. --Rajah (talk) 02:21, 19 February 2008 (UTC)[reply]

Sorry I can't find a reference, but I remember that it was either a solution of water and small amount of alcohol added or vice versa. In at least one of the cases, you can show that the volume of the solution decreases, because the solute and solvent are attracted to one another and pull the molecules closer together. --Rajah (talk) 02:50, 19 February 2008 (UTC)[reply]

And a followup point is that I would think, but am not sure, that if you can increase or decrease a solution volume by adding solute, then sometimes when you add a solute (or combination of solutes), the volume of the solution will remain the same. --Rajah (talk) 02:51, 19 February 2008 (UTC)[reply]

So, in no case involving a single solute and a single solvent does the solute just go in the intermolecular space of the solvent? I mean, if the solute were to go in the intermolecular space of the solvent, the volume would not change, would it? Kushal 17:57, 19 February 2008 (UTC)[reply]

It would be rare that the solute would be small enough and the spaces between the solvent molecules large enough and the interactions between the solute and solvent molecules be net-zero-effect. Things usually don't "just fit in and that's the whole story", but there could certainly be a net zero change in volume (balance of all interactions). Consider that if there's a (relatively) large space between solvent molecules, that means there's a strong (repulsive) force between them, so there's probably going to be a strong interaction (of uncertain direction) between those molecules and a solute molecule wedged between them. Cage-like molecules (cryptands, crown ethers, buckyballs) would be interesting exceptions: solute fits inside a single "solvent" cage, but it's perhaps rigid and so cannot change size/shape when the solute is present vs absent. Though it depends on how one defines "solvent" a bit. DMacks (talk) 19:28, 19 February 2008 (UTC)[reply]

Thank you very much. Kushal 11:22, 21 February 2008 (UTC)[reply]

I want an stream eletric generator to produce 80000 units of current annually

I want an stream eletric generator to produce 80000 units of current annually which is run by an cocentrated solar type stream producer.please help me. —Preceding unsigned comment added by 58.68.95.56 (talk) 14:16, 18 February 2008 (UTC)[reply]

Like - help you how? --hydnjo talk 14:40, 18 February 2008 (UTC)[reply]

Units of current annually? You might be able to phrase your question more clearly if you first study our articles on solar energy and Electrical Units.--Shantavira|^{feed me} 14:55, 18 February 2008 (UTC)[reply]

And SI electromagnetism units. --hydnjo talk 15:13, 18 February 2008 (UTC)[reply]

80,000 Amperes of current would require extraordinarily large conductors coming off the generator windings as well as in the windings. 80,000 kilowatt-hours per year would only require the generator to produce 9132 watts average (naturally it would have to produce much more than this during the hours the sun is shining). Before you issue bid specifications or begin construction, you should familiarize yourself with the units of measurement of electric power. Edison (talk) 19:51, 18 February 2008 (UTC)[reply]

See Russ Rowlett's pages on units of measurement: definition 6 for a "unit" is "in Britain, another name for the kilowatt hour, which was formerly called the Board of Trade unit." And by the way (to be picky) the man was Ampère but the unit is ampere without a capital letter. --Anonymous, 21:37 UTC, February 19, 2008.

claustrophobia

I am trying to find out if anxiety about being in a situation where escape might be difficult is also claustrophobia. eg being on an island or a large boat, not involving small enclosed spaces or panic attacks. thanks —Preceding unsigned comment added by 97.96.181.252 (talk) 15:38, 18 February 2008 (UTC)[reply]

I would have a look at the phobias article. Also, the DSM-IV is a good reference guide, which mentions anticipation of events. -- MacAddct  1984 ^{(talk  contribs)} 16:28, 18 February 2008 (UTC)[reply]

The Merck Manual points out a website called The Phobia List, which lists hundreds of phobias. I tried searching for "escape" and several related terms, but no hits. Based on a Google search I did earlier, it does seem that claustrophobia includes the cases you mentioned (that is, any event in which one could not escape). Sorry, I'm not an expert. (EhJJ)^TALK 17:51, 18 February 2008 (UTC)[reply]

Also take a look at agoraphobia, maybe. --Ouro (blah blah) 19:04, 18 February 2008 (UTC)[reply]

inclined planes

If you put a sledge on a steep enough ramp, it'll slide down.. but where is the horizontal component coming from? Is it electromagnetic, from friction? If I had never seen something roll I don't think I'd ever have guessed a horizontal component would appear :D\=< (talk) 16:56, 18 February 2008 (UTC)[reply]

There are two forces on the sledge. There is gravity, and there is the force of the ramp pushing back on the sledge. Ignoring friction (for a moment, I'm just trying to keep it simple), the force of the ramp pushing back on the sledge is perpendicular to the surface. Which means, since the ramp is tilted, it has a horizontal component. JohnAspinall (talk) 17:05, 18 February 2008 (UTC)[reply]

There's a nice diagram at the inclined plane article. Sancho 17:13, 18 February 2008 (UTC)[reply]

Yes, the force is electromagnetic, at the molecular level. The molecules of the surface exhibit a net positive force against the molecules of the sledge -- static friction. Once the angle is sufficiently steep, gravity overcomes static friction and dynamic friction comes into play. -Arch dude (talk) 04:25, 20 February 2008 (UTC)[reply]

Blindness versus deafness

Have any scientific studies been done on the following questions and, if so, what did they conclude?

Which is "worse" or "harder" ... which is "better" or "easier" ... to be blind or to be deaf?

Which is "easier" ... which is "harder" ... to be born blind ... or to have sight and then subsequently lose it?

Which is "easier" ... which is "harder" ... to be born deaf ... or to have hearing and then subsequently lose it?

For lack of better words, I use the terms easier / harder / better / worse to generically mean ... the ease/difficulty a person has adjusting, getting by, everyday living, accomodating, adapting, etc., in a world today where most people are not deaf or blind ... physically, mentally, socially, psychologically, etc. Thanks. (Joseph A. Spadaro (talk) 17:33, 18 February 2008 (UTC))[reply]

I doubt the first question is even a matter of studies- its' obviously far harder to be blind than the be deaf :D\=< (talk) 18:19, 18 February 2008 (UTC)[reply]

Well, I don't know. There is a story (which I haven't tracked down but is referred to here) that Helen Keller would have preferred to have her hearing back instead of her sight if she could have only one: "... because when you lose your sight, you lose things. When you lose your hearing, you lose people." Also, "The problems of deafness are deeper and more complex, if not more important, than those of blindness. ... Deafness is a much worse misfortune. For it means the loss of the most vital stimulus – the sound of the voice that brings language, sets thoughts astir and keeps us in the intellectual company of man." Of course, this was before the internet and texting. --Milkbreath (talk) 19:11, 18 February 2008 (UTC)[reply]

Also the phrase "tis better to have loved and lost then to have never loved at all" may provide answer to the second query. Although similarly so could the lines "if i hadn't seen such riches I could live with being poor" from James Sit Down...I guess it depends on an individual's perspective. I recall reading a story about a man who had been blind from birth, was getting rather old and was gardening with his wife, helping to turn over the soil when his eyes focussed and he saw for the first time - bold yellow flowers. The most beautiful thing, the flower he had loved that his wife had described on many occasions was the first clear vision of his life. A nice story I always thought, but i'm not sure if vision can just 'return' like that? ny156uk (talk) 18:50, 18 February 2008 (UTC)[reply]

My impression from the recent Gallaudet University presidential succession controversy is that if you don't learn sign language as a mother tongue, you may have trouble integrating fully with other deaf people, just as an adult who goes to a foreign land might never overcome the language barrier. --Sean 19:16, 18 February 2008 (UTC)[reply]

Considering that 80-90% of the average person's sensory information comes from sight, it's probably more difficult to be blind than deaf. —Lowellian (reply) 20:59, 18 February 2008 (UTC)[reply]

There are ranges of degree for both deafness and blindness. Total deafness is, as I understand, quite rare. Also, if we are talking about being born or becoming deaf or blind at an early age, then for most of history and to the present in parts of the world, deafness is far worse. See Prelingual deafness and History of the deaf -- until surprisingly recently in history being prelingual deaf (total or profoundly deaf), meant never learning language and never acquiring symbolic thought. This is far far worse a fate than being blind in any form. But as I said, profound prelingual deafness is rare compared to most kinds of hearing impairment. Still, since the question didn't specify I thought I would point out this example in which being deaf is worse than being blind, no contest. A book that explores this particular topic in some detail is "Seeing Voices" by Oliver Sacks. Pfly (talk) 04:38, 19 February 2008 (UTC)[reply]

If you never even develop symbolic thought that's not such a bad fate.. it might be pretty confusing but you don't know what's going on or that you can't think properly. Same as those quotes above, you wouldn't know or care what you're missing. Also it reminds me of the Futurama episode where the professor gives a martian monkey superintelligence and it's smart enough to see that knowing things sucks and it was happier in the jungle, so it takes off its brainwave hat and returns to the wild as a stupid monkey :D\=< (talk) 05:04, 19 February 2008 (UTC)[reply]

For humans there is no wild to return to. Not having language does not mean you not want to be among other humans, to have social feelings and emotions, etc. If your needs were taken care of by kind loving people, then perhaps it would not be so bad. The norm, however, for most of history, was isolation, abuse, scorn, and such like. Pfly (talk) 00:17, 20 February 2008 (UTC)[reply]

Thanks for the great input. Much appreciated! (Joseph A. Spadaro (talk) 01:04, 24 February 2008 (UTC))[reply]

Non-foaming shampoo on first wash, explosion of foam second wash.

Can someone explain what's going on here? When I wash my hair in morning, the first shampoo does not foam up at all. But after rinsing and applying a second dose of shampoo, my hair explodes with lather. --70.167.58.2 (talk) 17:35, 18 February 2008 (UTC)[reply]

Lather, rinse, repeat... ;-) hydnjo talk 17:55, 18 February 2008 (UTC)[reply]

I'm not 100% sure, but I guess it's caused by saturation. The first time you apply shampoo it will mostly solve in the water and attach too the fat in your hair, but the second time most of the fat is already washed off and the water already saturized, preventing the extra shampoo from solving and thus creating foam. - Dammit (talk) 18:00, 18 February 2008 (UTC)[reply]

For this reason, i usually first take a smaller amount of shampoo and do a quick scrub and rinse through all my hair to get the bulk of the oil out, then I take a little more and have a longer and more satisfying leathering scrub. Vespine (talk) 00:36, 19 February 2008 (UTC)[reply]

Hair oils. The oils prevent it from lathering up the first time, but after they are washed away, then a nice foam can arise. bibliomaniac 1 5 00:51, 19 February 2008 (UTC)[reply]

Note also that lather is affected by the hardness of the water. If there is a lot of Ca2+ in your water supply it may not be as easy to form a lather, obviously unless you go somewhere else with softer water you won't notice this though.

Shniken1 (talk) 02:25, 19 February 2008 (UTC)[reply]

Fundamentally, oil neutralizes soap or detergent. In the first case, most of the soap/detergent is neutralized, but it removes all of the oil from your hair. On the next application, no oil remains, so all of the soap or detergent is un-neutralized and is available to form bubbles. -Arch dude (talk) 04:15, 20 February 2008 (UTC)[reply]

Newtonian Physics

I'd like to start a space program with an objective of sending a manned expedition to Mars. The major caveat of the expedition is that I wouldn't want any of my planners or engineers to use General Relativity. I'd like the entire mission to run on the assumption that Newtonian physics is the physics of the universe. Will my crew be safe?Sappysap (talk) 18:44, 18 February 2008 (UTC)[reply]

Since I assume you're actually a world leader starting such a program and not just a student doing homework or something, I'll give you a very practical answer. Putting people on Mars is an enormous undertaking that will require the best engineers in the world. These are pragmatic and careful people who will simply refuse to be involved in such folly as to risk lives, billions of dollars, and their own reputations on something like running a space program on long-discredited science. Sorry, George. --Sean 19:27, 18 February 2008 (UTC)[reply]

Isn't space travel mostly Newtonion Physics these days? What does relativity have anything to do with launching a rocket, slingshoting it near another body of mass, and then landing on Mars? 206.252.74.48 (talk) 20:24, 18 February 2008 (UTC)[reply]

Well, or more to the point: would any of the speeds, forces, etc. that they would be experiencing come to the point where Newtonian physics wasn't a good enough approximation? GR generally only becomes a significant factor when you are talking about very high gravities, very high densities, very fast speeds. I'm not sure if anything involved in a Mars landing using modern technology would require relativistic effects to be factored in; the Newtonian might be good enough. --98.217.18.109 (talk) 20:51, 18 February 2008 (UTC)[reply]

Or not! I'd factor in anything that I knew about even if it only affected the margins. --hydnjo talk 21:13, 18 February 2008 (UTC)[reply]

Hydnjo's comment is well stated. Newtonian physics provide a very good approximation of actual orbital mechanics for present space travel. However, when you're talking about billion-dollar programs, it's sheer hubris to ignore a better approximation. Risk management is a very important part of space exploration, and excessive approximation is bad risk management. — Lomn 21:43, 18 February 2008 (UTC)[reply]

You should probably avoid anything that takes precise timing measurements on radio signals like a GPS does, and also design your computer systems so that they can gracefully handle any minor discrepancies in time-keeping. (Especially compared to ground-based clocks.) 72.10.110.107 (talk) 22:05, 18 February 2008 (UTC)[reply]

I disagree. Timing is everything! --hydnjo talk 23:37, 18 February 2008 (UTC)[reply]

Incorrect textbook?

My textbook on geography states:

“

If Earth did not rotate on its axis - creating day and night - only the half facing the Sun would receive solar energy. ... The half of the planet facing away from the Sun would always be dark and cold.

”

I agreed with this statement until the word always; if the Earth did not rotate, at least at some point, the other side would be exposed to the Sun's energy within the year. Is this correct? --~~MusicalConnoisseur~~ Got Classical? 19:30, 18 February 2008 (UTC)[reply]

I agree with your assessment of their wording. They may have been trying to describe tidal locking. --Sean 19:50, 18 February 2008 (UTC)[reply]

Yes, but nowhere in that paragraph does it mention tidal locking (though that idea did enter my mind). Its topic is a totally hypothetical situation - if the Earth did not rotate, period, unlike the moon. --~~MusicalConnoisseur~~ Got Classical? 20:13, 18 February 2008 (UTC)[reply]

Well, the side of the Earth that is not facing the sun is dark and cold(er). Nobody said that side ever stayed over the same geographic location. —Preceding unsigned comment added by 206.252.74.48 (talk) 20:55, 18 February 2008 (UTC)[reply]

Yeah, I agree. As it reads, there's nothing wrong with the statement in the textbook, since it doesn't specify that the side facing away from the sun is always the same part of the Earth. —Lowellian (reply) 21:01, 18 February 2008 (UTC)[reply]

It's a textbook. They get things wrong. Don't hold them to the same standards as Wikipedia. Considering some of the anti-Wikipedia articles linked to in the In the News section of the Wikipedia Signpost (not necessarily today), no one else does. — Daniel 21:14, 18 February 2008 (UTC)[reply]

It's a classic frame-of-reference question, isn't it? When we say that an orbiting body "doesn't rotate", do we mean that it always keeps the same face towards the body it's orbiting, or that it always keeps the same face towards 0° longitude in the "fixed" frame of the body it's orbiting?

Supposedly there was an ancient Greek philosopher whose lifelong, quixotic quest was to find students who had not been "brainwashed" otherwise by his peers, and teach them that the moon does not rotate as it revolves around the earth... —Steve Summit (talk) 23:09, 18 February 2008 (UTC)[reply]

A rotating reference frame is non-inertial. From any inertial frame, a body with a tidal lock is rotating. — Daniel 00:30, 20 February 2008 (UTC)[reply]

Is it physically possible...

To die from the loss of the will to live?

Assuming that the person doesn't commit suicide, eats properly, sleeps properly, does not OD on medicine, and is perfectly healthy in every way...

could it happen?

Thanks!

❦ECH3LON ❦ 23:41, 18 February 2008 (UTC)[reply]

I doubt that anyone would respond by saying "that's impossible". --hydnjo talk 23:49, 18 February 2008 (UTC)[reply]

I think most normal people would not have the ability to will themselves to death, or in this cases unwill themselves from life. There are many people, for example in jail that wish they could will themselves to death, but they still usually have to resort to more physical measures. Don't hear too many cases of death by lack of will to live. On the otherhand, it seems quite common with old couples that seem to keep them selves going, but once one dies the other soon follows, seemingly having "lost the will to live".. Vespine (talk) 00:32, 19 February 2008 (UTC)[reply]

...But, similar to the idea of hypocondriacs and the Nocebo effect, if it is possible to have a disease that is self-procured, then surely, isn't it possible to have that same "illness" kill someone? I'm not sure if this complicates the question though. ❦ECH3LON ❦ 02:30, 19 February 2008 (UTC)[reply]

Of course, everyone has many diseases at any given time, which are wiped out by our immune system before they become noticeable. So, all that's necessary to die from disease is to suppress your immune system to the point where the diseases win the battle. I'm not sure if this is possible, but it might serve an evolutionary purpose, if individuals which no longer contributed to the survival of the group were to have killed themselves in this way, thus enhancing the chance that others in the group carrying their genes would survive. StuRat (talk) 09:38, 19 February 2008 (UTC)[reply]

Kurdaitcha might be of some interest. In these cases, the person doesn't just decide of their own volition to give up the will to live, it's externally imposed; but the effect is the same. We need a better article (or any article) on Pointing the bone, so I can't say how widespread this practice was or, indeed, if it's still practised at all. -- JackofOz (talk) 23:31, 19 February 2008 (UTC)[reply]

So...It's like the horror story 'The Candidate by Henry Slesar in which the main character is told of a way to kill people by using wishes, or willpower, and then later die of "Natural Causes"?

That's interesting...❦ECH3LON ❦ 00:46, 20 February 2008 (UTC)[reply]

February 19

About time dilation and planet habitation

I've been wondering about the effects of time dilation on planets orbiting at different velocities around a star. My question is this: if Planet A is orbiting around its star at say twice the velocity of Planet B, does time pass slower on Planet A in relation to B? Also, if you're sitting stationary in a solar system, does time pass slower on an orbiting planet in relation to you? There's probably some weird gravitational dilation that I'm not taking into account here, but I'm really aching to find out the answer to this, so any help will be greatly appreciated. --Closedmouth (talk) 04:10, 19 February 2008 (UTC)[reply]

Yes to both, but not significantly. See the Lorentz factor for the underlying math. — Lomn 05:08, 19 February 2008 (UTC)[reply]

The question doesn't really provide sufficient information to say for sure that time passes more slowly on the surface of planet A. Besides the orbital speeds of the planets, you also need to take into account the rotational speeds of the planets as of where the observers are, as well as differences in gravitational time dilation between the two planets. MrRedact (talk) 07:32, 19 February 2008 (UTC)[reply]

Orbiting objects are always accelerating. Accelerating things are not really in the realm of special relativity. General relativity has Gravitational time dilation, which indeed says that time in lower gravitational potential (closer to the star) runs slower. --131.215.220.112 (talk) 12:09, 19 February 2008 (UTC)[reply]

The time dilation effect would most likely be insignificant. All objects that are traveling at different speeds experience the phenomenon, but it goes unnoticed. A good example is a traveler on a jet airliner. They experience a minute and insignificant time dilation with respect to observes on the ground. Wisdom89 _{(_T / ^C)} 18:37, 19 February 2008 (UTC)[reply]

The above statement that "accelerating things are not really in the realm of special relativity" is overly general. This is a common misconception about special relativity vs. general relativity.

Special relativity works just fine for dealing with rapidly moving, accelerating objects in the absence of gravity, such as a charged particle in the presence of an electromagnetic field, or a spaceship that's not near an astronomical body, that's accelerating due to thrust from its engines. For example, see Hyperbolic motion (relativity), which deals with an accelerating object, but only uses special relativity.

It's only when dealing with a curved space-time, i.e., when dealing with gravity, that you need to use general relativity. This particular problem does indeed require general relativity, but that's because gravity is involved, not just because acceleration is involved. MrRedact (talk) 00:22, 20 February 2008 (UTC)[reply]

Thanks, guys. Most interesting :) --Closedmouth (talk) 12:58, 20 February 2008 (UTC)[reply]

Aircraft carrier design

Current US aircraft carrier design features two runways, one for launches and one for landings. Would it be possible to put the launch deck below the landing deck to dramatically reduce the length of a carrier ? One potential problem with this would be ventilation, as the jet engines on the planes burn large quantities of oxygen and put out large quantities of exhaust. Perhaps this could be dealt with by having open sides and ends on the launch deck (with steel columns supporting the landing deck, of course), massive exhaust fans, maximizing the use of catapults, and only going to full jet engine thrust at the final moment of launch (I visualize the launch sequence being fully automated, with no pilot interaction until the plane is airborne). Besides the smaller size, other advantages of such a setup might be the ability to launch in harsher weather conditions and less reduction of launch capability due to bombs dropped on the deck from above. Does this approach seem feasible ? StuRat (talk) 09:30, 19 February 2008 (UTC)[reply]

My first thoughts are:

Airplanes and concrete runways tend to be heavy
Runways tend not to work so well with steel supports sticking out of them

:D\=< (talk) 11:42, 19 February 2008 (UTC)[reply]

The additional launch decks ("second flying-off decks") are actually mentioned in the aircraft carrier article, in the aircraft carrier#Hurricane bow section. The article makes it sound like a bad idea, but provides no explanation. I would think that the main problem with such a configuration would be that the planes are taking off too close to the water. An increased threat of flooding would also be a concern. Besides, the carrier size is not crucially dependent on the takeoff strip size. It may well be (I am not sure) that the area and volume requirements on hangars and depots are more important for carrier design; in that case, placing launch deck below the landing deck is counterproductive. Cheers, --Dr Dima (talk) 11:41, 19 February 2008 (UTC)[reply]

Takeoff height and hangar volume are easily solved -- build the second deck higher. I expect, though, that Froth has hit on the problem -- how do you support the upper deck without interfering with flight ops? Topside, aircraft wings can overhang as needed, which an interior flight deck wouldn't permit. On that alone, you're losing a great deal of usable area.

Additionally, the angled-deck design isn't simply one of "two runways". It's perhaps more important as "runway plus storage". The angle allows for safe execution of landings, with the allowance for an aborted landing attempt where the plane returns to full power, with other aircraft stowed forward on the usual launch area. There they can be refuelled, rearmed, and otherwise quickly maintained without introducing the additional bottleneck of the aircraft elevator. — Lomn 14:48, 19 February 2008 (UTC)[reply]

Are, I wonder, flight decks the way of the future in any form? The current crop of aircraft carriers under construction now are probably the last that will feature full complement of human-operated aircraft. The next generation will surely have drone fighters (and probably fighter-bombers and attack/bomber aircraft). It's not clear how this will affect shipboard operations (and it'll probably be another generation before they fully figure that out). It's quite possible that launch systems for drone fighters might move to a rocket-cartridge system (like that used for naval TLAMs now, leaving the flight deck only for recovery and (for those navies that operate them) for other aircraft like tankers and ELINT aircraft. For a carrier that only hosts small agile hardy fighters (which can take the high forces associated with rocket-launches and "giant butterfly net" landings) it's quite possible the flightdeck will shrink or maybe even disappear altogether. -- Finlay McWalter | Talk 15:13, 19 February 2008 (UTC)[reply]

It all depends on what type of plane you want on the carrier. The British carriers are already much smaller (see figure to right for a comparison) since they use the Sea Harrier. David D. (Talk) 15:27, 19 February 2008 (UTC)[reply]

This is kind of a misleading statement. You seem to be insinuating that the British carrier is better. It isn't. It's a lot worse in fact. Bigger aircraft carriers, hold more aircraft, and thus can project more power. 64.236.121.129 (talk) 19:33, 19 February 2008 (UTC)[reply]

The converted cruisers: Glorious, Courageous, and Furious all had small, auxiliary flight decks below the main deck over the forecastle which could launch Fairey Flycatcher fighters. They were too small to operate the aircraft of the '30s and '40's and were converted to gun decks during later refits.—eric 16:38, 19 February 2008 (UTC)[reply]

Thanks for all the info so far. As for the issue of the steel columns interfering with flight ops, in a fully automated system the pillars could be only slightly farther apart than the widest wingspan, since the pilot doesn't need to navigate between them. If this didn't provide sufficient support for the upper flight deck (recovery deck), then arches could be used between the columns (this might require increasing the height a bit, though). As for reducing usable area, aircraft wings could still extend out over the edge of the carrier, between the columns. It would also be helpful if a system were used where the planes could be moved sideways to quickly get them onto the runway from a storage slot on the side. StuRat (talk) 18:34, 19 February 2008 (UTC)[reply]

The "usable area" point I wanted to make was one of launching. Note, for instance, that a Nimitz carrier's two forward catapults are set far enough to the sides that the wings overhang. Putting the catapults on a lower deck would likely force launch ops to a single catapult (I concur that otherwise you can trim the clearance margins). — Lomn 19:33, 19 February 2008 (UTC)[reply]

On an other note, see past dreams of grandeur with Project Habakkuk. 200.127.59.151 (talk) 22:38, 19 February 2008 (UTC)[reply]

...which inspired the 'mili-habbakuk' as a unit for measuring impracticability.—eric 23:04, 19 February 2008 (UTC)[reply]

The British design already has separate launch/recovery. Because they are using the Sea Harrier they typically (or at least optionally) recover planes by vertical landing. Also carriers are rarely launching and recovering at the same time. The problem is not the need to do both at once, but the equipment for each - the catapaults and arrestor hooks. If memory serves the Harrier-based design needs neither. DJ Clayworth (talk) 16:11, 21 February 2008 (UTC)[reply]

The Hall Voltage in Ionic Fluids

I've derived a formula to find the Hall voltage of a flowing ionic fluid:
$V_{H}={\frac {-IB/d}{ne}}.$

Current = charge passing through area cross section per second $I=vAne$
Where the ions in solution have charge -1, are traveling at velocity v through area A, and there are n ions per unit volume.
Substituting, $V_{H}={\frac {-vAneB}{ned}}$
$V_{H}=-vwB$
where w is the width of container.
Is this correct - the voltage depends only on the velocity, width of container and field strength? Why doesn't concentration of ionic solution make any difference?
In practice, does it make any difference with different ionic solutions / concentrations (due to grouping of ions/mobility), if so how will concentration affect voltage?
Also, I need to setup a strong magnetic field - does it matter if the field is not uniform and how can I arrange electromagnets to give a uniform field over about 0.2m²?
Does the choice of electrodes matter? Thanks --90.241.222.228 (talk) 10:12, 19 February 2008 (UTC)[reply]

I'm assuming this is a followup to a previous question about the Hall effect. Your question, "Why doesn't concentration of ionic solution make any difference?" is a good one. Remember this voltage was derived on the basis of an equilibrium between Lorentz force (from the magnetic field) and electric force (from the charge buildup). The concentration of ions will affect how fast you approach the equilibrium, but once the equilibrium is there, the net sideways force on any new moving charge is zero, regardless of how many other moving charges are around it.

I am not any sort of expert on Hall sensors, but I would guess that small variations in the magnetic field would be balanced by small variations in the charge buildup, and the resulting equilibrium would be "near" the equilibrium of a perfectly uniform field, making your answer "near" the real values. None the less, a nice uniform field can only help you. The classical way to get a fairly uniform magnetic field is to use a Helmholtz pair. JohnAspinall (talk) 16:05, 19 February 2008 (UTC)[reply]

Thanks. Is there any way of predicting how changing concentration will affect how fast equilibrium is reached? Can you suggest any other area to investigate other than changing concentration / ions in solution / speed / field strength? —Preceding unsigned comment added by 90.241.222.228 (talk) 21:08, 19 February 2008 (UTC)[reply]

You've already mentioned mobility. Mobility will determine how fast the ions "drift", to build up the charge separation. The drift velocity from the Lorentz force will work the same way as for the electrical force. I will guess that mobility will be independent of concentration, for low concentrations at least, so if you wanted to change the mobility, you might have to change the ionic species. Don't forget that (since the fluid is electrically neutral, on average) there may be a positive and a negative ion moving (in opposite drift directions) and they will (in general) have different mobilities. I would suggest a little searching on how mobility is measured. JohnAspinall (talk) 15:26, 20 February 2008 (UTC)[reply]

Supermagnet

A strange question just popped into my head. What if someone, with incredible technology or magic (basically the same thing) developed a monopole electromagnet with incredible strength? I had a similar discussion with a friend a while ago and she said that a strong enough magnet could tear electrons away from all the atoms in its range. Would this make such a silly device applicable as a superweapon? What horrifying effects would such a device have on matter, if any? 206.252.74.48 (talk) 17:17, 19 February 2008 (UTC)[reply]

I'm sure I've read a science fiction story about a scientist that invented a monopole magnet and submitted a paper about it, and then suddenly found himself being shadowed by agents from at least one government. I'm sorry that I don't remember the title or author. APL (talk) 17:35, 19 February 2008 (UTC)[reply]

At a given point in space, the magnetic field produced by a magnetic monopole would no different from the field produced by a dipole or any other distribution of "magnetic charge". The difference is in the global geometry of the field, not the quality of the field itself. So the effects of an incredibly strong monopole magnet on materials would be the same as those of an incredibly strong (but otherwise ordinary) dipole magnet. —Keenan Pepper 18:09, 19 February 2008 (UTC)[reply]

That is a good point, so just ignore the monopole part with this question. I want to know what the effects would be. 206.252.74.48 (talk) 18:28, 19 February 2008 (UTC)[reply]

Except that a monopole field would be felt over much longer distances. — Laura Scudder ☎ 20:13, 19 February 2008 (UTC)[reply]

Right, that's the only relevant difference in this context: a monopole field falls off as the inverse square of the distance rather than the inverse cube. —Keenan Pepper 04:25, 20 February 2008 (UTC)[reply]

So, I think the question boils down to "What are the effects of very strong magnetic fields on matter?". In that case, the answer is "nobody knows, exactly", but we can say a few things. For example, the field wouldn't "tear electrons away" from atoms, because magnetic fields do no work, and tearing an electron away from an atom requires work. However, as Magnetar#Magnetic field says, a very strong magnetic field (10 gigatesla) would rip your body apart because of the diamagnetism of water, and stretch atomic orbitals into thin needles.

I'm actually going to the open house of the National High Magnetic Field Laboratory in Tallahassee tomorrow, so I'll ask this question and post any interesting replies here. —Keenan Pepper 15:57, 20 February 2008 (UTC)[reply]

Actually, I believe the only reason a magnetic field can do no work is because there are no monopoles. — Laura Scudder ☎ 22:03, 20 February 2008 (UTC)[reply]

True: if monopoles exist, then a magnetic field can do work on monopoles. But it still can't do work on normal matter (such as the electrons being discussed here) that lacks magnetic monopole charge. --mglg_(talk) 23:21, 20 February 2008 (UTC)[reply]

You're forgetting that once we accept monopoles, we have to consider magnetic current loops. They should do work on electric monopoles. — Laura Scudder ☎ 03:35, 21 February 2008 (UTC)[reply]

Yes, a monopole current loop can create an electric field, which of course can do work on electric charges. But that fact has nothing to do with the question of whether a magnetic field can do work on electric charges (which it can't). For the magnetic-field question it is irrelevant how the magnetic field was generated, so the existence or non-existence of monopoles doesn't change anything. --mglg_(talk) 16:59, 21 February 2008 (UTC)[reply]

So, when an electric current creates a magnetic field, the current is actually doing the work, but if a magnetic current created an electric field, the electric field is doing the work? — Laura Scudder ☎ 00:48, 22 February 2008 (UTC)[reply]

(This off-topic sub-thread is getting out of hand long, but here goes:) Of course the work ultimately originates in whatever made the monopoles move in the first place. But the question wasn't about the ultimate source of the energy, but about whether the magnetic field can do (or convey, if you want) work on electric charges. You said above that you "believe the only reason a magnetic field can do no work is because there are no monopoles" (my emphasis), so you clearly do agree that a field can be considered to do work. In the monopole current loop case it is not the magnetic field that is doing any work, but the electric field. Using your analogy, if a normal electromagnet is used to lift a piece of iron, you would not say that it was the electric field of the electrons in the coil that was doing the work, would you? It is the magnetic field that does the work. That said magnetic field is generated by moving electric charges is beside the point. (Over and out.) --mglg_(talk) 04:34, 22 February 2008 (UTC)[reply]

When my foot falls asleep

I know that when my feet "fall asleep", it's because there's not enough circulation to it. One question, though: when that happens, what causes the "tingly" feeling, as if I'm being poked by little pins or having little electrical shocks? Nyttend (talk) 21:29, 19 February 2008 (UTC)[reply]

It's not just that you're cutting off the circulation to the cells and tissue of the limb, but also you're physically preventing nerve impulses from entering the CNS and vice versa. This causes the neurons/nerves to fire erratically after the pressure is released. Wisdom89 _{(_T / ^C)} 21:35, 19 February 2008 (UTC)[reply]

See Paresthesia. —Steve Summit (talk) 14:16, 20 February 2008 (UTC)[reply]

MATERIALS/CHARATERISTICS (Homework?)

LOOK,GUYS sorry I used the f word. When,I last posted this question but that`s a testament to How I much I need it answered. Just,tell Me The Measurements and Charateristics of a balloon going across a room. —Preceding unsigned comment added by Yeats30 (talk • contribs) 23:56, 19 February 2008 (UTC)[reply]

Homework much?Zrs 12 (talk) 00:21, 20 February 2008 (UTC)[reply]

Perhaps you could rephrase your question? Something like:

I deeply regret posting previous homework questions under false pretence and undertaking plagiarism in using these responses to dishonestly complete my homework. I promise not to do it again. Furthermore, I will not get upset with you, the Wikipedia Reference Desk volunteers, if you are not willing to aid me in continuing the aforementioned. Nevertheless, I request your assistance in understanding the concept of how to measure and characterize a balloon crossing a room. Sincerely, The "Physics Magazine" Guy

Honestly, we'd like to help you. We just don't want to get yelled at for not being willing to help you cheat. (EhJJ)^TALK 01:07, 20 February 2008 (UTC)[reply]

I like the way you phrased that EhJJ. Furthermore, I agree. Zrs 12 (talk) 01:18, 20 February 2008 (UTC)[reply]

I don't care if this might be a homework problem, I'm willing to help you anyway. The most important measurements and characteristics of a balloon going across a room are as follows:

1) Since the balloon is (usually) a prolate spheroid, it's important to consider the balloon's various radii of curvature, which will generally be on the order of 4 diopters.

2) The balloon's modulus of elasticity, assuming a rubber balloon, would be in the range of 0.01 to 0.1 GPa, if there were only a small strain. However, due to the balloon’s relatively large stress, the nonlinearity of the balloon material's stress-strain curve must be taken into consideration. Therefore, you’ll need to use the strain tensor for large deformations, which is

\varepsilon _{ij}={1 \over 2}({g_{ij}-g_{ij}^{(0)}})

3) Since the balloon is in motion across the room, it will undergo a relativistic length contraction. The amount of this effect is given by the formula

L'={\frac {L}{\gamma }}=L\,{\sqrt {1-v^{2}/c^{2}}}

4) It's important to take into consideration the balloon's de Broglie wavelength, so that interference effects can be computed as the balloon travels down various hallways and through windows and doorways. The balloon's de Broglie wavelength is given by

\lambda ={\frac {h}{p}}={\frac {h}{\gamma mv}}={\frac {h}{mv}}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}

I hope this was helpful. MrRedact (talk) 01:32, 20 February 2008 (UTC)[reply]

Oh! I thought of another very important characteristic of a balloon going across a room: the balloon’s relative static permittivity. I don’t know how such an important measurement could have slipped my mind; you’d have a heck of a hard time trying to figure out the balloon's capacitance without it! According to our article, the relative static permittivity of rubber is about 7. MrRedact (talk) 01:59, 20 February 2008 (UTC)[reply]

Would time dialation not be an important factor as well? Zrs 12 (talk) 02:18, 20 February 2008 (UTC)[reply]

Don't forget isotopic analysis. Any helium 3 that may happen to be in the balloon will contribute more to buoyancy than your regular helium 4 will. --Anon, 02:50 UTC, February 20/08.

Not true...the He-3 nuclei weigh less than He-4, but that's because there are fewer particles in those nuclei. They're lighter but also smaller and you can thus fit more into a given balloon volume. On average the gas still weighs the same per volume. That's a simple result of the ideal gas law: constant density of a gas regardless of what gas it is. DMacks (talk) 03:00, 20 February 2008 (UTC)[reply]

Are they really smaller? Yes, the nuclei are slightly smaller, but the nucleus is orders of magnitude smaller than the atom anyway. AlmostReadytoFly (talk) 08:47, 20 February 2008 (UTC)[reply]

...Besides which, the ideal gas law assumes pointlike atoms.AlmostReadytoFly (talk) 09:13, 20 February 2008 (UTC)[reply]

I agree, DMacks is wrong. The ideal gas law gives constant molar volume of a gas, not density. Helium-3 would indeed contribute more to the buoyancy. —Keenan Pepper 15:44, 20 February 2008 (UTC)[reply]

Sorry, forgot we were keeping the answers "literally correct" not "completely obvious bullshit":). Helium is small enough that lots of quantum effects and/or other weirdness happens. He-3 liquid density is about half that of He-4. DMacks (talk) 18:02, 20 February 2008 (UTC)[reply]

Also, there may by oxygen, nitrogen, etc. Furthermore, there will constantly be helium passing through the balloon into the atmosphere due to the pressure inside; there may even be some quantum tunneling (although probably not much).Zrs 12 (talk) 02:54, 20 February 2008 (UTC)[reply]

You guys are neglecting impulse and delta-v. The balloon is operating as a rocket, but in an atmosphere. IF he balloon were released in a vaccuum, we could neglect many of the effects mentioned above. However, assuming a vaccum will have important consequences for the delta-v. -Arch dude (talk) 03:58, 20 February 2008 (UTC)[reply]

Fuel efficiency of a Hot Air Balloon (and other questions)

If one would travel with a Hot Air Balloon from Texas to Florida, how would the fuel efficiency compare to a typical passenger airliner or personal jet? How safe is Ballooning compared to other forms of air travel? Malamockq (talk) 23:59, 19 February 2008 (UTC)[reply]

Hot air balloons are only safe when used under some rather specific conditions, like slow, steady winds and relatively flat ground (or water) which is clear of trees, buildings, and other obstructions. When used by a trained balloonist in airspace clear of aircraft, under those conditions, balloons can be fairly safe for short distances. Note, however, that balloons only go where the prevailing winds blow them, which makes them quite useless for general transportation. As for fuel economy, it's probably better than aircraft when measured on a per hour per passenger basis, but worse when measured per mile per passenger. StuRat (talk) 07:49, 20 February 2008 (UTC)[reply]

February 20

what would you call a small mountain range

Like Potrero Hills specifically, this is regarding a dispute on the wording of navegation disambiguation tag at the top of the similarly named neighborhood Potrero Hill, San Francisco, California. It's sloppy to say for the potrero hills see potrero hills, but one user believes that it should not state, the minor mountain range see potero hills, because they don't count as a minor mountain range, so is there some other term which could be found mutually agreeable. hill range? minor range?Boomgaylove (talk) 04:39, 20 February 2008 (UTC)[reply]

~~Here's a topo map of the feature.—eric 05:25, 20 February 2008 (UTC)~~[reply]

scratch that, those Potrero Hills are about 30 miles away, southeast of Fairfield.—eric 06:14, 20 February 2008 (UTC)[reply]

You mean this? Certainly the word moutain does not spring to mind if that is where you are talking about. I would have thought range would be used to describe huge area. For the disambigution why not just say See Potrero Hills for East Bay Regional Park? David D. (Talk) 05:42, 20 February 2008 (UTC)[reply]

what east bay regional park??Boomgaylove (talk) 13:26, 20 February 2008 (UTC)[reply]

All parks in the East Bay are managed by the Easy Bat Regional Park district. I assume this one is too? I could be wrong. David D. (Talk) 17:20, 20 February 2008 (UTC)[reply]

Apparently its not one of their parks. http://www.ebparks.org/parks David D. (Talk) 17:38, 20 February 2008 (UTC)[reply]

I see the disambiguation at Potrero Hill, San Francisco, California currently reads For the Potrero Hills in Richmond, California, see Potrero Hills. What's wrong with that? David D. (Talk) 05:48, 20 February 2008 (UTC)[reply]

it's not a park at all dummy =PBoomgaylove (talk) 22:59, 21 February 2008 (UTC)[reply]

It's redundant, and the first part where it says potrero hills, in the {{Other|what it is|article title}} format is not within precedent or commom usage of that template.Boomgaylove (talk) 13:26, 20 February 2008 (UTC)[reply]

You don't have to use the template. David D. (Talk) 17:20, 20 February 2008 (UTC)[reply]

How about "bluffs"? —Preceding unsigned comment added by Boomgaylove (talk • contribs) 13:27, 20 February 2008 (UTC)[reply]

The're not bluffs, the're hills. David D. (Talk) 17:20, 20 February 2008 (UTC)[reply]

You're bluffing! (Sorry, it's in my contract). 206.252.74.48 (talk) 19:44, 20 February 2008 (UTC)[reply]

On a side note, what would you call an edit war over this and related topics? —Steve Summit (talk) 13:59, 20 February 2008 (UTC)[reply]

"Over the top"? "Over the hill and a long way off"? "Over here, over there...", "Mountains or molehills", "A summit, how high"? ; )) Julia Rossi (talk) 10:50, 21 February 2008 (UTC) Okay, I give up, it must be "a summit conference".[reply]

Does the human brain have limits?

Does the human brain have "limits"? Is there only "so far" that it can go? For example, is it humanly possible, say, for a person to memorize an entire phone book? Or, are there some things just impossible / out of range for the human brain? Thanks. (Joseph A. Spadaro (talk) 07:11, 20 February 2008 (UTC))[reply]

Try photographic memory. This article led me to Ben Pridmore who holds the official world record for memorizing the order of a randomly shuffled 52-card deck in 26.28 seconds. Not exactly the phone book but pretty impressive. David D. (Talk) 07:23, 20 February 2008 (UTC)[reply]

Googling around a bit, this page seems to give an accurate scientific answer about this. The answer is not of course how much information is stored during a person's lifetime (ranges from hundreds of megabytes to many gigabytes), but how accurately he can recall that information. This is where a computer has a great advantage. Another interesting question is the difference between factual and visual information. As we know, computers need a great deal more storage for multimedia - so do the still and moving images that we keep in our brain also require more "storage space"? Even these blur over time, as the brain needs to refresh its pathways to older information, stored in a complex neural network of neurons (10 billion) and synapses (trillions or quadrillions). Sandman30s (talk) 15:12, 20 February 2008 (UTC)[reply]

Daniel Tammet memorized pi up to 22,514 digits in just over five hours. He also knows 11 languages and learned Icelandic in a week. -- MacAddct  1984 ^{(talk  contribs)} 15:10, 20 February 2008 (UTC)[reply]

According to something i heard on Paul Harvey's Rest ofthe story, the creator of Bingo (US) enlisted the help of a math whiz who manually came up with thousands of cards with all the different permutations, but wound up going insane because of it; so, that might be a good place to startr as far as a "limit." Sorry, I don't remember the name. (That, of course, was the days before computers.)209.244.30.221 (talk) 15:47, 20 February 2008 (UTC)[reply]

The brain is a physical device, so it certainly has limits. You might find Seth Lloyd's famous paper Ultimate physical limits to computation to be informative on the upper limits of the brain's capacities even if it was optimally configured for data storage (which it certainly isn't, as all my lost pens will attest). --Sean 18:09, 20 February 2008 (UTC)[reply]

No, there are no limits to the human brain. You can do anything if you put your mind to it. 64.236.121.129 (talk) 19:48, 20 February 2008 (UTC)[reply]

I do wish that was true, but so far I haven't managed to bend a single spoon using just thought. All my attempts at unaided flight have failed as well. 206.252.74.48 (talk) 20:50, 20 February 2008 (UTC)[reply]

Tell that to Deep Blue. APL (talk) 21:08, 20 February 2008 (UTC)[reply]

It's possible for a human to do anything that's physically possible; but not all humans can do all physically possible things. A person without legs cannot walk (defined as the action of moving by the use of legs), but people with legs can. A person born without eyes cannot see, but people with eyes can. The question is, what is the limit of physical possibility. Before Roger Bannister, it was considered very unlikely that a human could run a mile in 4 minutes. Now, that's considered a pretty ordinary achievement among athletes. But can a human run a mile in 2 minutes? Most would say no. But you never know. -- JackofOz (talk) 21:52, 20 February 2008 (UTC)[reply]

Jack, you finish there with the understatement of the year. Does anyone think a 2min mile is possible? The 100m WR is currently 9.74 s. Assumingly Asafa Powell could keep going that would equate to a 2min 36.8. The 200m WR is 19.32 s. Assuming Michael Johnson could keep going that would equate to a 2min 35.5. So even a relay of the best sprinters in the world could not beat 2 min. In this case I think it safe to say that Homo sapiens will never break 2 minutes for the mile. :) David D. (Talk) 22:04, 20 February 2008 (UTC)[reply]

Ah, but what kind of assumptions are you making? Surely it would be possible to run a 2-minute mile on a planet with a different gravity? Mars, perhaps, or the Moon.--Eriastrum (talk) 22:25, 20 February 2008 (UTC)[reply]

I would imagine you'd run a bit slower if the gravity is too low, as you'd end up putting too much of your energy into go up and not forward. Also, you'd need to have some sort of contained atmosphere, as doing a 2 minute mile in a bulky space suit might be tricky. -- MacAddct  1984 ^{(talk  contribs)} 22:37, 20 February 2008 (UTC)[reply]

I have a better idea - redefine the mile. Chris16447 (talk) 23:31, 20 February 2008 (UTC)[reply]

If you're only talking about their being a limit, I can tell you that a 0.00000537 second mile is impossible. It's slightly faster than the speed of light. The OP was talking about you're mind, so using 10⁵⁰ bits/s/kg from Sentience Quotient, and a mass of 3*10⁵² kg from Orders of magnitude (mass), I can tell you that you can't process more than 3*10¹⁰³ (3,000 googols) bits per second. — Daniel 23:33, 20 February 2008 (UTC)[reply]

Apparently, the human brain has no limits as to the amount of conceit, anthropocentrism, and human exceptionalism it is capable of. MrRedact (talk) 02:11, 21 February 2008 (UTC)[reply]

Is it too late to ask if a 2min mile's possible if the athletes were running on a downhill slope with a tail wind? I mean do we have to stick to track conditions in this hypothetical?Julia Rossi (talk) 10:56, 21 February 2008 (UTC)[reply]

Well in that case we might as well define it as freefall. How fast can a sky diver dive a mile? But I'm not sure that is relevant to the original allusion to Bannisters impossible feat. David D. (Talk) 18:44, 21 February 2008 (UTC)[reply]

Thanks. Good discussion. But ... uhhhh ... can a person memorize a phone book or not? (Joseph A. Spadaro (talk) 14:45, 21 February 2008 (UTC))[reply]

Well, the point of a lot of this discussion was to emphasize that it's very hard (if not impossible) to give a clear "no" answer. In the absence of a confirmed "yes", all that's left is "maybe". Has anybody done it? No. But could they? Maybe. — Lomn 16:22, 21 February 2008 (UTC)[reply]

That depends on how big the phone book in question is. My old (1990) Guinness Book of World Records lists Gou Lan-ying of China as having memorized over 15,000 phone numbers. Tom Morton has memorized over 16,000 phone numbers. Akira Haraguchi holds the record for memorizing pi, at 100,000 digits, which is the number of digits in about 14,285 7-digit phone numbers. There do exist phone books for small towns with fewer phone numbers than that. But can a human memorize the 180,000,000 phone numbers listed on whitepages.com? No way. MrRedact (talk) 18:46, 21 February 2008 (UTC)[reply]

Strange Picture

Look at this picture of the A380. http://i.l.cnn.net/cnn/2008/BUSINESS/02/20/airbus.ap/art.airbus.afp.gi.jpg

The right wing looks short but the left wing looks very long. Has this picture been delibrately modified? Is it a real picture? 122.107.226.136 (talk) 12:54, 20 February 2008 (UTC)[reply]

I agree it looks odd, but I think it's a real picture. Since the near wing is pointed towards the camera, it is foreshortened. Since the far wing is perpendicular to the camera, its full length is emphasized.

Part of the surprise is just due to how very far the wings on modern planes are swept back -- they don't stick straight out from the fuselage by any stretch of the imagination. —Steve Summit (talk) 13:34, 20 February 2008 (UTC)[reply]

Also, since we're kind of viewing the plane from above, consider that dihedral is also contributing to the close wing's foreshortening. jeﬀjon (talk) 13:37, 20 February 2008 (UTC)[reply]

It is probably related to this illusion, where the image gets flattened when taking photos with a zoom lens. -- MacAddct  1984 ^{(talk  contribs)} 15:05, 20 February 2008 (UTC)[reply]

Do you think so? I wouldn't have said that had anything to do with it. The issue here isn't that depth is compressed, it's that the wings are at different angles to the viewer and so they look like they have different lengths. At best, I'd say that we're used to the closer wing looking bigger from our personal up-close experience, so when we see a long-lens shot, we subconsciously compensate a bit in the opposite direction. I'd think that's pretty minor, though; I'd think most people see as many photos of planes as they see real up-close planes. jeﬀjon (talk) 15:46, 20 February 2008 (UTC)[reply]

Are the A380's wings actually horizontal? If they slope up from the fuselage, this could explain it a bit. -mattbuck (Talk) 10:20, 21 February 2008 (UTC)[reply]

They do slope up, as seen here, though not as much as some other types of planes. Check out the definition ofdihedral. jeﬀjon (talk) 13:41, 21 February 2008 (UTC)[reply]

That A380 is ginormous. I just want to point that out to anyone who doesn't notice. 64.236.121.129 (talk) 19:48, 20 February 2008 (UTC)[reply]

This is quite an interesting exercise. If I'd been shown the photo for 10 seconds, without any commentary, and then asked to draw it as accurately as I could from memory, I'd have made the wings roughly equal in size. My brain instantly recognised that the a/c was banking, and compensated for the apparent difference in the length of the wings. To me, there was nothing "odd" about it; the wings were of equal length, obviously. It was only when I looked at it closely that I realised the left wing in the image is actually almost twice as long as the right. I failed to distinguish between the image of the a/c, and the a/c itself (based on my prior knowledge of the symmetrical shape of a/c). Teaching people how to reproduce what they actually see and not what their left-brain logic tells them "must be there" is covered in various places, such as Betty Edwards's Drawing on the Right Side of the Brain. This left wing-right wing photo is an excellent metaphor for that whole area of study, so thank you, 122.107.226.136. -- JackofOz (talk) 21:36, 20 February 2008 (UTC)[reply]

Spots

Request for diagnosis removed. The identification of a medical condition is the textbook definition of "diagnosis", and saying "I'm not asking for a diagnosis" does not change this. Follow up with your doctor if concerned. — Lomn 16:09, 20 February 2008 (UTC)[reply]

First robin in February?

Okay, my mom's in NE Ohio, and she swears that a few days ago, she saw a robin at the bird bath. Is it really normal for them to be up here this early, and if so, why is there the thing about them being the first sign of spring - it is not springlike here. I could understand if it were, say, 65 Fahrenheit and had been in the 50s a few days in a row; then animals can be fooled.209.244.30.221 (talk) 15:56, 20 February 2008 (UTC)[reply]

It happens. There's a map here that shows robins in February in the USA. Some even overwinter; I've seen them deep in the Pine Barrens in January. See these folks for everything robin. --Milkbreath (talk) 16:16, 20 February 2008 (UTC)[reply]

Last weekend was the Great Backyard Bird Count, and I had robins and bluebirds (unusually early) in southwestern PA. I know they were also reported on a lot of lists in Pittsburgh. You can pull up results for her area at the GBBC website, to see if others reported robins—this year, it wouldn't surprise me. You can also try eBird to get annual charts of birds' comings and goings for a particular area. -- Coneslayer (talk) 16:21, 20 February 2008 (UTC)[reply]

I saw lots in January here in Colorado, but I think they stay all winter, since it warms back up pretty regularly. Seems to be supported by our range map, which also shows Ohio in the year round range. — Laura Scudder ☎ 22:28, 20 February 2008 (UTC)[reply]

As to your second question, I think it's robins singing, not just being spotted, that is supposed to be a sign of spring. — Laura Scudder ☎ 22:35, 20 February 2008 (UTC)[reply]

I feel I should point out that range maps like the one here are pretty coarse, and the range will vary over time and from year to year. Also, not every single area within the green will hold a robin year-round; there are micro-climates and the like that limit their ability to overwinter. You can imagine the green breaking up and going patchy as it approaches the yellow. --Milkbreath (talk) 10:27, 21 February 2008 (UTC)[reply]

Meerkats

I can't find any thing that will tell me when Meerkats where first discovered here on Earth, can someone please help. Thanks, Megan —Preceding unsigned comment added by 69.133.3.155 (talk) 19:15, 20 February 2008 (UTC)[reply]

It depends on what you mean by "discovered". If you mean by humans, then the answer would be a million or so years ago when Homo sapiens first evolved in Africa, where the meerkat is native. If you mean in a formal scientific sense, then it was in 1776 when the species Suricata suricatta was first described by Johann Christian Daniel von Schreber.--Eriastrum (talk) 19:49, 20 February 2008 (UTC)[reply]

I believe they have yet to be discovered on planets other than Earth, but I could be wrong. Gwinva (talk) 00:34, 21 February 2008 (UTC)[reply]

Menstruation and lunar cycle

Is there any scientific theory - no matter how offbeat - explaining why the lunar cycle and human menstruation cycle are approximately the same length? Or is it just complete coincidence? TheMathemagician (talk) —Preceding comment was added at 19:39, 20 February 2008 (UTC)[reply]

yep, it's pretty much coincidence. - Nunh-huh 19:56, 20 February 2008 (UTC)[reply]

The whole thing is controversial, but see our articles menstrual cycle and culture and menstruation.--Eriastrum (talk) 20:06, 20 February 2008 (UTC)[reply]

(ec) I think this is a good paper on the idea. If you search google, you'll find the idea of a link between lunar and menstrual cycle to be a common one (and has quite a few papers published on it). According to the article I linked to, there is no statistically significant evidence of a link between the lunar and menstrual cycles. Although a number of much earlier papers argued otherwise, the linked paper suggests those previous studies suffered from problematic sampling. The paper also argues that claimed evidence of a similar concept, that women who live together will have similar menstrual cycles, suffered from a flawed statistical analysis. Someguy1221 (talk) 20:13, 20 February 2008 (UTC)[reply]

Wait a minute. There are two different questions here. As someguy points out the idea that the menstrual cycle coincides with the lunar cycle is bogus. However, the original poster just asked about the length of the menstral cycle being about the same length as a lunar cycle (28 days). The length of the menstral cycle might (remote possibility here) have evolved originally under the influence of the lunar cycle. After all a number of marine organisms are linked to the tidal (lunar) cycles.--Eriastrum (talk) 20:32, 20 February 2008 (UTC)[reply]

Actually, women in non-western countries tend to have longer cycles - 4 months long for some I think. It's a coincidence nothing more. Heck, western cycles aren't often 28 days - they're roughly that, but often longer. -mattbuck (Talk) 21:06, 20 February 2008 (UTC)[reply]

While 28 days is commonly given as the average length, the normal range is 21-35 days, so it is hard to confirm any link with a lunar cycle. Gwinva (talk) 00:41, 21 February 2008 (UTC)[reply]

Mattbuck, do you have a reference for the 4 month thing (as in, a population where that's normal)? That seems implausible to me. --Allen (talk) 04:35, 21 February 2008 (UTC)[reply]

He almost certainly meant 4 weeks long. —Preceding unsigned comment added by 79.122.42.134 (talk) 10:04, 21 February 2008 (UTC)[reply]

"4 months long for some" may mean "for some women" rather than "for some countries." I mean, I can't read Matt's mind, but that would certainly be possible. Someguy1221 (talk) 10:13, 21 February 2008 (UTC)[reply]

Nope, I meant 4 months. It was in New Scientist a month or two ago. -mattbuck (Talk) 10:19, 21 February 2008 (UTC)[reply]

Were you by chance referring to this article on artificially lengthening the menstrual cycle? I didn't see anything else remotely relevant in the more recent issues. Someguy1221 (talk) 22:41, 21 February 2008 (UTC)[reply]

Electric Flux Units

Electric Flux is measured is Nm² /C. If a Netwon-meter is a joule and a joule/coulomb is a volt, can it be stated that flux is measured in volt-meters? If not, why? 21:15, 20 February 2008 (UTC)

It can. Electric field can be measured in volts/meter, and flux is field times area, so you get units of (V/m)(m²)=Vm. --mglg_(talk) 21:40, 20 February 2008 (UTC)[reply]

Becoming a Spaceman

How does one become a spaceman? What kind of training/education is required? 64.236.121.129 (talk) 21:46, 20 February 2008 (UTC)[reply]

See [9]

Make a good chunk of money, wait a few years, then book your flight. Clarityfiend (talk) 22:12, 20 February 2008 (UTC)[reply]

NASA are hiring. Angus Lepper^{(T, C, D)} 22:47, 20 February 2008 (UTC)[reply]

Hehehehhe "Frequent travel may be a requirement"... Can I catch the bus? Shniken1 (talk) 05:07, 21 February 2008 (UTC)[reply]

Actually, I think they have to do an awful lot of public relations travel. A NASA astronaut who never gets gets to fly on a mission may still have to do many school visits, ect. I know this only because my workplace has been trying to arrange for an astronaut as a guest speaker for several years. ike9898 (talk) 15:05, 21 February 2008 (UTC)[reply]

Also, an astronaut training for the International Space Station will train in Houston, Florida, Canada, Russia, Germany and Japan, at the very least. anonymous6494 04:14, 22 February 2008 (UTC)[reply]

Science Fair (Quantum Dots)

I am in the science fair this year and am at a complete loss as to what to put in my "future" section. (A future section tells real-life applications for the experiment you performed.) I did an experiment in which I had to find the wavelength of 4 samples of indium phosphide quantum dots when shown a λ=405nm LED. Then, I had a formula in which I used the wavelength of the light fluoresced by the quantum dot sample to relate the wavelength of fluoresence to the radius of the quantum dot. As I said, I am at a complete loss as to how to apply this (relating the radius and wavelength) in a real-life application. I asked the chemistry teachers at school and they can't think of one either. Any suggestions are greatly appreciated. Thanks, Zrs 12 (talk) 22:47, 20 February 2008 (UTC)[reply]

Many food substances are colloids, for example milk has droplets of fat in them. In Homogenised milk the droplets are made to be in a certain range of sizes. If they are too big you will get cream rising to the top of the milk. The size of these droplets can be investigated via light scattering.. Many other products use the same theory..

Not really a future application as it is already happening. Shniken1 (talk) 01:54, 21 February 2008 (UTC)[reply]

It doesn't have to be a future application. Just any application past, present, or future. I, personally, haven't a clue as to why the choose to call it "future". I think it's because you also must put things in that section which could be done to improve the experiment (in the future if you did it again). Thank you for your suggestion :-); much appreciated. -- Zrs 12 (talk) 02:04, 21 February 2008 (UTC)[reply]

I hear Dippin' Dots are the ice cream of the future. -- MacAddct  1984 ^{(talk  contribs)} 02:53, 21 February 2008 (UTC)[reply]

....Ok? Zrs 12 (talk) 14:32, 21 February 2008 (UTC)[reply]

He was just trying to be funny (and succeeded, in my opinion). However, I will not call any ice cream the "ice cream of the future" until it is unmeltable, never sticky, and tastes exactly like whatever you want it to taste like. 206.252.74.48 (talk) 18:21, 21 February 2008 (UTC)[reply]

I think eating whatever you want it to be may be the better option here. Why eat bacon-flavoured ice-cream when you can eat bacon itself? It also doesn't melt, isn't sticky (well mostly), and tastes exactly like bacon. --antilived^{T | C | G} 03:30, 22 February 2008 (UTC)[reply]

Yes. I know he was trying to be funny but that didn't pertain to what was being discussed. It just seemed random to me. Zrs 12 (talk) 23:14, 21 February 2008 (UTC)[reply]

February 21

Environmental Effect of Al Gore

Often, in criticism of Al Gore, I hear people say something along the lines of "Oh, he's such a hypocrite. He preaches about saving the environment while he himself flies around in his private jet."

Which led me to approach this quantitatively... say Al Gore traveled in a private jet from New York to Los Angeles and back. During the trip, he spoke to 500 people and convinced them to switch the light bulbs in their household to energy efficient light bulbs. Would the positive effect of people switching their light bulbs outweigh the pollution from the trip, or vice versa?

I'd like to see someone work this out. If they do, I ask that they state any assumptions they make. (How much power the jet uses, average household power usage, the change in wattage from the switch of light bulbs, etc.) 04:57, 21 February 2008 (UTC)

Allow enough time and certainly the power savings win out -- you're comparing a one-time cost to an ongoing improvement. This, however, addresses a straw man. It's not "Gore educates the world via private jet or not at all" but "Gore flies on a private jet or Gore flies a regular airliner". — Lomn 05:03, 21 February 2008 (UTC)[reply]

Well vaguely, let's see. A Gulfstream jet gets ~1.2 miles per gallon, and he's traveling of order 5000 miles round trip, so he uses ~4000 gallons of fuel. Jet fuel has an energy density of ~125 MJ / gal, so he used of order 500 GJ of energy. Assuming he convinces 500 people to reduce their energy consumption by 150 W each (equivalent to replacing ten 60-W bulbs with CFLs, assuming each bulb is run 8 hours a day on average) then that is a net savings of 75 kW. In which case, the energy cost of the plane trip will be recouped after 75 days. Environmental impact is generally proportional to energy cost modulo small multiples depending on how the energy is generated, so for the scenario you suggest, Al looks okay. Of course, it is probably pretty generous to assume Al gets 500 new converts every time he talks, and flying on a commercial airliner is still almost certainly more efficient regardless. Dragons flight (talk) 05:29, 21 February 2008 (UTC)[reply]

Incidentally, the best commercial airlines, fully loaded, can get as good as 30 miles per gallon per person, and hence use only about 5% of the energy per person as transporting a single person by small private jet. Dragons flight (talk) 05:35, 21 February 2008 (UTC)[reply]

Good point. I'll change the question slightly. Lets say a person (for the sake of bringing politics out of it, but thats probably too late) flies from New York to Los Angeles and back every week, and that they manage to get 500 people a month to switch. 05:15, 21 February 2008 (UTC) —Preceding unsigned comment added by Pakiprince7135 (talk • contribs)

This question seems irrelevant in all kinds of ways. First of all, the resources actually consumed by Gore, or any other individual human being, are negligible on a planetary scale. His jet could get 0.01 miles to the gallon and it wouldn't matter per se. Secondly, a celebrity like Gore doesn't primarily influence people by talking directly to them. Everything he does is symbolic. Politicians don't talk to individual voters just to get their votes, they do it to get the votes of people who see or hear about the conversation and start to think of the politician as a man of the people. If Gore acts hypocritically, or more to the point if he seems to act hypocritically, he'll lose followers. That's why he shouldn't waste jet fuel, not because the energy usage of the world's small population of celebrities makes such a difference in the grand scheme of things.

Also, a given amount of energy in jet fuel is worth more than an equal amount of energy in burning light bulbs, because petroleum is a much more precious resource than energy sources in general. -- BenRG (talk) 13:48, 21 February 2008 (UTC)[reply]

The entire discussion above is missing the critically important point that Al Gore always buys a carbon offset every time he flies, so that the CO₂ and other greenhouse gasses produced due to him flying are balanced out by CO₂ reduction measures elsewhere. Al Gore is very meticulously carbon neutral. MrRedact (talk) 19:10, 21 February 2008 (UTC)[reply]

Except that carbon offsets are bunk when used in that way. And can even be bunk otherwise too, if not carefully handled. 79.74.0.57 (talk) 00:30, 22 February 2008 (UTC)[reply]

Could you please explain why you think carbon offsets are bunk when used to offset air travel? I'm not asking to start an argument; I'd genuinely like to know. My girlfriend wants to take a trip to Machu Picchu that I'm not too keen on, but my global warming argument against going is getting shot down by the availability of carbon offsets. The whole tree planting variety of carbon offsets does seem of dubious value, since it seems to me like forest land is pretty much a fungible commodity -- if you plant and protect trees in one part of the planet, without reducing the demand for land, forests will just be destroyed in another part of the planet, instead. But it seems like it's hard to deny the value of more modern types of carbon offsets, like donating to a renewable energy project that wouldn't otherwise be developed, thereby not only reducing CO₂ production, but also reducing the consumption of our limited supply of fossil fuels. MrRedact (talk) 02:08, 22 February 2008 (UTC)[reply]

Dragon is pessimistic assuming that it saves only 15 watts to switch from a 60 watt incandescent to a comparable compact fluorescent. The CFL would use 13 to 15 watts, per GE [10] for a saving of 45 to 47 watts per bulb or at least 450 watts per person if he operates 10 bulbs. Edison (talk) 20:10, 21 February 2008 (UTC)[reply]

This depends on the climate lived in. If you're heating your house, switching to CFLs will require you to use more heating to keep the house at the same temperature, since there will be less heating from the bulbs. Add to this that if lightbulbs are switched off when you leave a room, an incandescent bulb only heats the rooms you are using when you are using them (unlike central heating). If you live in Florida, switching to CFLs probably makes sense and could indeed save many watts. If you live in a cooler climate, it's less clear cut. 79.74.0.57 (talk) 00:30, 22 February 2008 (UTC)[reply]

As I said, I'm assumming the lighting in your home is only on about 8 hours a day. Do you run all the lights in your house when you are away at work or asleep? Hence 450 / 3 is 150. Dragons flight (talk) 00:38, 22 February 2008 (UTC)[reply]

Redact, if Al Gore flew on an airliner, it would cost him less and he could buy more carbon offsets. The only reason you'd be able to use carbon offsets to justify something is if you could only afford them because of the action you took. This requires the environmentally friendly action to be more expensive, but it's almost always cheaper. — Daniel 23:21, 21 February 2008 (UTC)[reply]

Explain about the working of nMOS super buffers in VLSI?

Can you help me?

I am Joshy Karanath from India. Now I am studying B-Tech [ Electronics & Communication ] at Ihrd College Of Engineering, Poonjar , Kerala.

Now I need help from you. Please give me the explanation or tell me about the link from where I can get this information. The topcs are given below.

1. "Ion Implantation process" in VLSI. (with figures)

2. Working of "Super Buffer" in VLSI. (Inverting type nMOS super buffer)

3. Detailed Explanation in "Second Order MOS device effects in VLSI" (all the five effects with figures)

4. Fabrication Process in "BiCMOS" in VLSI (With Figures)

Thanking you,

Joshy Karanath.

Apologies if this is rude of me, but I have reformatted your question to make it easier to read. No content has been changed, simply formatting and capitalization. I am sorry that I cannot help with your request, but I hope someone else can TheGreatZorko (talk) 11:29, 21 February 2008 (UTC)[reply]

Rabbit skeleton conservation

Which is the best way to conserve the skeleton of a dead rabbit so it does not disintegrate, while at the same time promoting flesh decay in the quickest and most hygienic manner? -- 83.56.190.69 (talk) 11:20, 21 February 2008 (UTC)[reply]

Would putting the corpse into a weak acid, and then transfering it to some sort of embalming fluid, such as formaldahyde work?

Out of curiosity what is this for? What is stopping you stripping the flesh and then simply preserving the skeleton? TheGreatZorko (talk) 11:32, 21 February 2008 (UTC)[reply]

Yes, I would be inclined to boil bunnikins if all you want are its bones. Of course you will need some way to reassemble the bones correctly and join them together. A museum might have some useful advice on how to do this.--Shantavira|^{feed me} 13:43, 21 February 2008 (UTC)[reply]

Note that this will smell pretty bad. Ventilate! --98.217.18.109 (talk) 13:50, 21 February 2008 (UTC)[reply]

Flesh eating ~~beatles~~ beetles are what commercial companies that do this kind of use according to "Dirty Jobs". Zrs 12 (talk) 14:30, 21 February 2008 (UTC)[reply]

Flesh eating beatles? I knew rock-and-roll was evil! DJ Clayworth (talk) 15:54, 21 February 2008 (UTC)[reply]

Haha. Sorry, it was early. That better? Zrs 12 (talk) 23:11, 21 February 2008 (UTC)[reply]

Well, with AC/DC, rolling stones, and lead zepellins around, how could anyone doubt rock-and-roll was dangerous? 206.252.74.48 (talk) 16:07, 21 February 2008 (UTC)[reply]

19th century anatomists wouold sometimes place a skull or skull with some flesh attached in a perforated metal cage and sink it in a pond for a year or so to deflesh it. Museums clean bones of some animals with insects. Edison (talk) 20:02, 21 February 2008 (UTC)[reply]

I don't think we should be answering this question. He could be abusing animals for all we know. Malamockq (talk) 02:52, 22 February 2008 (UTC)[reply]

press machine

hi, pls tell us that which press machine(ie: 5 ton, 10 ton)should be used for cutting a CRC sheet of thickness of 0.5mm,which should not damage both tool&diePnengineers (talk) 11:34, 21 February 2008 (UTC)[reply]

CRC??--Shantavira|^{feed me} 12:56, 21 February 2008 (UTC)[reply]

CRC in this context is probably "Cold Reduced Coil steel". Also known as "cold rolled steel" (see cold rolling). It's not on the dab page, but probably should be. You would need more than 5 or 10 tons, maybe something like 30 tons, but it's years since I did anything like that and you really should contact a company that sells or hires such equipment; they would be able to advise you. Neıl ☎ 14:23, 21 February 2008 (UTC)[reply]

starch vs. sugar

Is there any real difference, from a nutrition or health standpoint, between consuming a given amount of calories from sugar vs. starch? ike9898 (talk) 14:58, 21 February 2008 (UTC)[reply]

Not really, no, not if you're talking calories. However, because starch is an enormous polysaccharide of glucose, and sugar (i'm assuming you mean table sugar) is a disaccharide of glucose and fructose, they will be digested into mono and disaccharide subunits for absorption in the small intestine in the same manner. Ultimately, the individual sugars will be metabolized differently when taken up by the cells, or the liver will end up processing them into glucose. Wisdom89 _{(_T / ^C)} 16:32, 21 February 2008 (UTC)[reply]

Probably most relevant to your question are the concepts of glycemic index and insulin index. These relate to how your body reacts to the consumption of equal amounts of different sugars (as far as changes in postprandial blood glucose/insulin levels are concerned, respectively.) Some people (including many doctors/dietitians) believe that there are important health benefits of a low glycemic/insuin index diet, including the South Beach diet and, to some extent, the Atkins diet, among others. (EhJJ)^TALK 16:41, 21 February 2008 (UTC)[reply]

The glycation activity of fructose (50% of sugar) appears to be much greater than that of glucose (100% of starch). Frankg (talk) 16:54, 21 February 2008 (UTC)[reply]

Aren't starch and sucrose both converted to glucose before being used by cells? Other than the greater tooth decay due to sugar and the higher glycemic index of sugar, what is the difference between consuming 200 calories a day of sugar or 200 calories a day of starch as paret of the diet, so far as long term health, weight gain, or the ability to do work? Edison (talk) 20:01, 21 February 2008 (UTC)[reply]

"Other than ... the higher glycemic index of sugar..." There's your answer. Hello diabetes! And other things. What did the Romans ever do for us? 79.74.0.57 (talk) 00:25, 22 February 2008 (UTC)[reply]

Is the universe 100% logical and 100% consistent 100% of the time?

Is the Universe always logical and consistent, so that anything that FOLLOWS LOGICALLY from something else is in fact going to BE THAT WAY, with no exceptions, ever, in the history of the universe??? —Preceding unsigned comment added by 79.122.42.134 (talk) 16:20, 21 February 2008 (UTC)[reply]

No. I think what you're asking about is called Determinism, and it's how scientists used to think the world worked, but quantum theory isn't deterministic. AlmostReadytoFly (talk) 16:24, 21 February 2008 (UTC)[reply]

You may also want to read Deterministic system (philosophy) (EhJJ)^TALK 16:26, 21 February 2008 (UTC)[reply]

Surely determinism is the totally different position that everything that happens, happens because it follows logically (from earlier events and general laws) that it must happen? The answer to the OPs question is yes, but this is a property of logic, not the universe. In strict logical terms, no event's happening ever follows logically from any other set of events, and if something doesn't happen despite following from true facts and general laws, then the laws were false. Algebraist 16:39, 21 February 2008 (UTC)[reply]

I think the OP is looking at things a little too anthropocentrically. What seems logical and consistent to us might be very different to what is "truly" logical. While it ~~may seem like~~ is circular logic, everything that happens in the universe occurs due to natural laws and it is consistent because it's occurring in nature according to natural laws. If it didn't, one might assume some outside, supernatural force is acting upon it, or our own understanding of natural laws needs revision. -- MacAddct  1984 ^{(talk  contribs)} 18:45, 21 February 2008 (UTC)[reply]

Can you give me an example of something that MUST follow, but nevertheless empirically at least once in the history of the universe hasn't? I'm thinking of examples like: If you put drop three apples into an empty a basket there MUST be three, the Universe would have to be illogical or inconsistent to return a basket of 2 apples for no reason... Has stuff like that ever happened? (Like in dreams). —Preceding unsigned comment added by 79.122.42.134 (talk) 17:16, 21 February 2008 (UTC)[reply]

We could only answer whether each of us individually has ever had this experience, but can't answer if something like this has ever happened. There aren't enough observers to check that the universe has been consistent 100% of the time. Sancho 18:40, 21 February 2008 (UTC)[reply]

Essentially, let's say the universe has a set of rules called R, and we have an approximation of those rules called A (also known as Science). What you're asking is if R has ever contradicted itself (if the universe has broken its own rules). The problem, is we don't even know what R is. We can only tell when R contradicts A and then we adjust A to match our observed R. There are PLENTY of examples of R contradicting our (at the time) A (think relativity, quantum mechanics, virtual particles, etc.), where we had to change A. Theoretically, however, R always applies and can not contradict itself. (EhJJ)^TALK 19:04, 21 February 2008 (UTC)[reply]

That was a much more logical and elegant way of putting it than my ramblings! -- MacAddct  1984 ^{(talk  contribs)} 19:06, 21 February 2008 (UTC)[reply]

Speaking of apples in baskets, it reminds me of a physics joke: "The physics department is having a party at a professors house. Initially, there is no one in the house. Two professors enter the house (it's a small party). Afterward, three professors leave the party. Finally, one returns to the party. How many professors are in the house? None!" (2-3+1) = 0 This might seem illogical and contradictory, but that's how the universe works! (That is, from what I've been told. Maybe someone with more physics background can elaborate). (EhJJ)^TALK 19:15, 21 February 2008 (UTC)[reply]

Maybe an anti-professor entered the house. That would be logically indistinguishable from a professor leaving it. DJ Clayworth (talk) 20:12, 21 February 2008 (UTC)[reply]

If three walked out, then the initial observation that there was "no one in the house" was incorrect. I like the joke on the Mathematical joke page better. But this isn't about jokes, this is serious business, and the fact of the matter is that we know nothing. Who knows, maybe the universe isn't made up of quarks. Maybe everything is made up of universes, and our universe is a quark in another universe, ad infinitum. What is light is actually infinitely fast but it leaks into another dimension at a certain speed and gets instantly replaced by light from yet another dimension? What if time is actually tangible? How about liquid gravity? Multiverses! Stuff that exists only if people look at it! I'm not crazy! 206.252.74.48 (talk) 20:18, 21 February 2008 (UTC)[reply]

The other problem with determinism is that it isn't that something follows from something else, it's that everything follows from everything else - nothing in the universe is a truly closed system (except possibly the universe itself), and so even if you had all the rules at your disposal you would find it impossible to make 100% accurate predictions as that would require knowing the exact properties of everything in the universe at one time - even being accurate to a thousandth of a percent could become an error of a thousand percent in the long run, thanks to chaos theory. Confusing Manifestation(Say hi!) 22:24, 21 February 2008 (UTC)[reply]

Two problems: quantum theory is often nondeterministic. Read up if you are interested in details, but there are times that things seem to happen for no good reason and there is no way to predict exactly when they will happen. And it's not an issue with our knowledge of things; they seem to actually be indeterminate at a base physical level. Creepy, no? Einstein found the idea disgusting but it seems to be the case. Second problem: no non-trivial system of logic can be entirely complete and consistent, a priori. See Gödel's incompleteness theorems for the full proof, but it's pretty hard stuff to make sense of from the get-go. Nevertheless it seems to hold up well; to sum it up, as one webcomic artist I enjoy recently did: "Formulations of number theory: Complete, Consistent, Non-trivial. Choose two." --98.217.18.109 (talk) 22:56, 21 February 2008 (UTC)[reply]

Being controlled by quantum randomness is in a way worse than being controlled by predictable determinism...(to me personally) 199.76.153.227 (talk) 00:54, 22 February 2008 (UTC)[reply]

Building a voltaic stack

I have been trying to build a voltaic stack for a science fair project. I have been using dime and pennies, all from after 2000, and blotter paper soaked in a vinegar-salt solution. I have used up to ten cells. I am connecting the stack by copper wire to an LED, but it will not light up. Does anyone know why or what I am doing wrong? —Preceding unsigned comment added by 70.253.160.19 (talk) 20:34, 21 February 2008 (UTC)[reply]

Do you have access to a voltmeter? The reason to ask is the following: there are two or three kinds of problems possible here.

Your stack might be working, a little, but unable to put out the amount of current required by the LED.
Your stack might be generating no voltage at all.
You might be wiring the LED backwards. The "D" in LED stands for diode; it will only conduct in one direction.

A voltmeter would let you see which it is. Once you know what kind of failure mode you have, you can start looking for likely causes. If it's the first kind, voltage but not enough current, you should look for high resistance in your circuit. Start by cleaning the coins well. If it's the second kind of problem, look for an unwanted current path. If your electrolyte (the vinegar-salt solution) allows current to flow along any path other than the series order of the cells, then you might have a short circuit. Finally, a voltmeter will allow you to detect which is the positive end of your stack, and confirm which way the LED will conduct. JohnAspinall (talk) 20:55, 21 February 2008 (UTC)[reply]

If we use D=dime, P=penny, and B=vinegar/salt blotter paper, does your stack look like this:

DBPDBPDBPDBP (4 stacked cells of Dime-Blotter-Penny each)

or like this:

DBPBDBPBDBPBDBPB (Dime-Blotter-Penny-Blotter-Dime etc, which will generate nothing except heat)

-SandyJax (talk) 21:18, 21 February 2008 (UTC)[reply]

Body wastes H2O?

Does the body not waste significant amounts of water, when we exhale? If I took a walk in the desert, surely I'd fancy to not let go of all the water in my body, but rather keep it circulating. Why is it treated like a waste product? 81.93.102.185 (talk) 20:41, 21 February 2008 (UTC)[reply]

The values for obligate water loss in humans are fairly well established. The minimum insensible water loss is about 800 ml per day; of this, about 400 ml per day are lost via evaporation from the skin, and about 400 ml per day are lost via expired air. These minimum values would obviously be exceeded in the heat of the desert in the midst of exertion.

Humans are not particularly well-adapted for desert life (nor is there any particular reason we should be, as by and large we don't live in deserts). The kangaroo rat does a much better job, both in terms of concentrating its urine, and in terms of reducing water loss through the lungs. :). - Nunh-huh 21:32, 21 February 2008 (UTC)[reply]

Humans evolved in tropical Africa, which was wetter at the time than it is now. 98.199.17.94 (talk) 02:09, 22 February 2008 (UTC)[reply]

February 22

What else is there?

As a non-physics type reflecting on the "What exactly is a magnetic field" thread of Feb 15, when a person asks whether something's animal, vegetable or mineral, what else is there? How close is energy (like a force field) to being matter – can you say that? Julia Rossi (talk) 04:21, 22 February 2008 (UTC)[reply]