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August 3

Crescent Moon illumination

I was just watching the crescent Moon (it's about an hour before sunrise here), and I noticed that, while I could see the sunlit crescent, I could easily see the dark part of the Moon as well. The thing is, the edge of the Moon on the dark, non-lit part seemed to be brighter than the center. Is it due to the Moon geography (lighter/darker parts), or due to some real effect? Thanks 208.80.154.136 (talk) 02:25, 3 August 2013 (UTC)

I think most likely what you are seeing is Mach bands (an optical effect). Looie496 (talk) 02:31, 3 August 2013 (UTC)

Yeah - I second that - it's a classic example of a mach band...essentially just an optical illusion. SteveBaker (talk) 05:34, 3 August 2013 (UTC)

Thanks, makes sense. 78.0.225.163 (talk) 20:51, 3 August 2013 (UTC)

Also note that the reason you can see the dark part at all is due to earthshine, that is, sunlight which reflects off the Earth to the dark side of the Moon, and then back to us (I can't help but think of the pinball opening credits at the start of 3rd Rock from the Sun). StuRat (talk) 22:16, 3 August 2013 (UTC)

Airliner emergency exits

Every commercial airliner I've ever been on had emergency exits of some type with clear instructions on how to open the door in case of a crash. Usually, if you're sitting in an exit row, the hostesses even come and instruct you on how to open it in case the pictographs aren't clear. Do these emergency exits only open if the plane is stopped on the ground? Could criminals/terrorists open the doors in flight for bailing out, or just for the chaos caused by loosing cabin pressure? 202.155.85.18 (talk) 03:25, 3 August 2013 (UTC)

According to this, you can't open them while the cabin is pressurized since they have to swing in. Dismas|^(talk) 03:31, 3 August 2013 (UTC)

Some of the ones I've seen don't swing at all. Pulling the lever actually detaches the door like a manhole cover, and then you throw it outside the aircraft, so I don't think pressure will hold those on. 202.155.85.18 (talk) 03:43, 3 August 2013 (UTC)

Do they go straight out or do you have to pull them in and then push them out lengthwise? Dismas|^(talk) 04:07, 3 August 2013 (UTC)

I think they just fall outside, but my hostess on that flight was from Thailand so she spoke a bit funny and maybe they do come in first. Googling around a bit I found that a new trend it apparently outward swinging doors that avoid having to pull the door inward against a throng of desperate passengers in fear for the lives. These are locked electronically in a fail-open arrangment. 202.155.85.18 (talk) 04:38, 3 August 2013 (UTC)

These say there is no possibility of opening them in flight.[1] [2] Apteva (talk) 04:49, 3 August 2013 (UTC)

Re. the overwing exits (which are the ones that "detach like manhole covers"), they DO have to be pulled INWARD to open -- so, in fact, cabin pressure WILL prevent them from opening. 24.23.196.85 (talk) 00:41, 4 August 2013 (UTC)

Supposedly most of them must come inwards slightly to unlatch then they pop outwards. This prevents them from opening at altitude.

I dunno if they also have other locking mechanisms that stops you from popping them open.

This wasn't always the case. Check out D._B._Cooper.

And also check out Door#Aircraft_doors, which lists four cases where the doors were opened during flight.

APL (talk) 07:23, 3 August 2013 (UTC)

All four of those doors were cargo doors, not passenger doors. Dan Cooper (D.B.) (not likely his real name) specifically chose that aircraft because it was the only type that you could parachute from, because it had a rear door. He asked the pilot to depressurize the plane so that the door would open. Whether he survived is unknown, but some of the money was recovered years later, on the beach. An unreferenced statement in our article says that instead, "The crew soon noticed a subjective change of air pressure" when the read door was opened. I will look for a reference to change that. Apteva (talk) 17:17, 4 August 2013 (UTC)

That line isn't surprising. I'll bet it's true. You can notice a change in air-pressure when you open a car window on the highway. (On some cars anyway. It has to do with air-flow around the car.) APL (talk) 00:30, 6 August 2013 (UTC)

Of course if the door opens outwards then the cabin pressure won't help. CambridgeBayWeather (talk) 07:27, 3 August 2013 (UTC)

Yes, a smaller aircraft is easier to open the door, but not easy. That one was not supposed to be possible to open. Apteva (talk) 17:17, 4 August 2013 (UTC)

A few weeks ago, I was up front in an Bonanza when my door popped open. (Our pilot was fidgeting with the door because he thought the seal was leaking, and "pop" it went). The cabin is unpressurized, and we were only starting our climbout, some 3500 or 4500 feet over the San Jose hills. But the airflow kind of wedged the door into a steady-state configuration, cracked at an exact angle so that air rushed into the cockpit and held the door fixed. Now, we were only going about a hundred fifty knots, but let me tell you: there was no amount or force that I could exert against the air pressure to move the door in either direction - not to open it any wider, nor to slam it shut. It was held exactly at the steady angle that the airflow dictated it should hang at. High-velocity air acting on a few square feet of door can easily generate hundreds of pounds of force.

The Bonanza's door swings outward, and is notorious for popping open in flight; the rushing air slamming my face was about the loudest air I've ever heard, and I was pretty glad I didn't have to land the aircraft. A few times, my Citabria's door has popped open, but I can usually slam it shut without effort, or slow to fifty miles per hour and slip it to get the door to close on its own; or my backseat passenger/co-pilot takes care of it for me. Because the Citabria flies so much slower, and the door hinge is a lot simpler, it has never been an issue to close in-flight. But we had to make the call to land the Bonanza with the door open (or continue on with the wind blasting me for another forty minutes or so). We landed at KLVK, and the tower didn't even acknowledge anything out-of-the-ordinary.

This is yet another good reason why pilots are legally required to keep their seatbelts fastened at all times; and shoulder harnesses must be fastened for takeoff and landing (FAR 91.107). Everyone thinks it's really stupid when the pilot falls out of an aircraft. Nimur (talk) 08:24, 3 August 2013 (UTC)

Slipping a plane at 50 knots? I hope this is at 1000 feet AGL or higher, and that you're current on spin recovery! 24.23.196.85 (talk) 00:44, 4 August 2013 (UTC)

Yessir, and compliant with 91.119 (minimum safe altitudes) and all other applicable regulations. As a pilot of a conventional gear, aerobatic aircraft - and one without flaps - we slip all the time - it's a normal operation as part of every crosswind landing, whereas a lot of Cessna pilots (and even my pal with the Bonanza) tend to treat the slip as an emergency-landing-procedure only, and crab it in every time. I have to know how to slip without stalling - it's a maneuver that gets checked as part of my tailwheel type rating (FAR 61.31(i)(1)(i)). But it'd be hard to spin even if I wanted: when I'm soloing, I'm way under maximum gross weight, well inside the aerobatic envelope, and the Citabria usually stalls (power off) at just about forty (40) miles per hour (mph, not knots, on our airspeed indicator). 50 mph with power gives me plenty of margin, especially because the buffeting onset of a stall is so obvious at those low speeds - everything starts rocking and rolling and the stick goes limp - long before the pitch-over, and long before I lose altitude. And remember - you cannot spin unless both wings are in a full stall. With engine power, it's sometimes not possible to pitch the Citabria to the stall (I just keep... pitching up and climbing. Fortunately, on the checkrides, there's always gonna be some extra dead weight in the back seat).

My door's popped open once in the pattern, in a climbing turn to crosswind at just about 400' absolute altitude, and on that instance my CFI in the backseat closed it for me. One other time I recall, the door popped open while I was by myself at around 3000 feet MSL somewhere over the foothills near Skyline Boulevard. If you read the Airmen Practical Test Standards, we're supposed to be able to handle these sorts of "reasonable distractions" without panic or loss of control of the aircraft. It's probable that my CFI opened our door on purpose, on at least one occasion, just to check if I could handle a "realistic" distraction and maintain safe flight. He's definitely created more serious distractions: most memorably, he tried to take my eyes off the runway at short final by tapping me on the shoulder to point out a P-51 downwind in the pattern on the other runway. He later told me it really was a real P-51 and that I missed a pretty rare sight. I was unable to ever verify independently.

The point of all this side-story, as pertains to the original question: a door opening in flight does not need to be an emergency. In fact, a door falling off in flight is not even an "emergency" or an "incident" according to the legal definitions of those terms, as specified in the FARs or the NTSB safety regulations. Now, an airliner at 30,000 feet with a pressurized cabin is not equivalent, obviously, to a small general aviation aircraft. For one thing, passengers require supplemental oxygen if the door opens and the cabin depressurizes. Even still, that scenario is neither an emergency nor an incident, unless the pilot in command believes the open door jeopardizes the safe outcome of the flight. Nimur (talk) 02:36, 4 August 2013 (UTC)

Thanks for the clarification. For my part, all of my flight training was in the faster and heavier Cessna 172, which starts to mush at 55 knots with flaps up (although it can fly as slow as 40 with them down) and has a safe landing speed of 65 knots -- which is why I thought 50 would also be close to a stall in your case. 24.23.196.85 (talk) 01:04, 6 August 2013 (UTC)

The small emergency exits operated by passengers are plug doors so they cannot be opened by a human being when the cabin is pressurized. To be opened on the ground, the passenger must open the door inwards and then dispose of it. This is best done by moving the door to a horizontal position, rotating it through 90 degrees so it will pass easily through the exit, and then throwing it out onto the wing or onto the ground. (In some genuine emergencies, conscientious passengers have passed the door back to other passengers in the cabin, out of concern that throwing the door outside onto the ground will damage it. However, this is misguided because in an emergency when the cabin is to be evacuated the value of this small door is insignificant.)

In an unpressurized aircraft, it would be possible to open the small emergency exit in flight. Dolphin (t) 05:25, 4 August 2013 (UTC)

Where do kangaroos come from and what are they made of?

I don't mean Australia and meat, but in an evolution sense. Do we know what common grandparents they share with each of the mammals they sort of look like (goat, possum, human, rabbit, etc.)?

I've tried Googling, but only find archaeological and zoological stuff (I don't really trust those guys). I don't understand genetic terms enough to Google efficiently, but I can mostly understand them in context once I have them (same with French). A push in the right direction would be nice, if nobody has a definitive answer. InedibleHulk (talk) 06:12, 3 August 2013 (UTC)

Does Marsupial#Evolution help? Ghmyrtle (talk) 06:54, 3 August 2013 (UTC)

Macropodidae, the taxonomic Family (biology) of kangaroos may also be of interest. Try also "zoological stuff" at "Macropodidae (kangaroo)". The Paleobiology Database. Australian Research Council. 2011. The evolutionary split between mammalsplacentals(us) and marsupials (kangaroos) was apparently 160 million years ago, as near as we can tell so far. See New York Times, August 24, 2011 "A Small Mammal Fossil Tells a Jurassic Tale", and Daily Mail (UK), 19 November 2008 "Kangaroos 'are closely related to humans', scientists claim". "Kangaroos: Biology of the Largest Marsupials" page 6, dated 1995 so out of date now. --220 of ^Borg 14:45, 3 August 2013 (UTC) Corrected! --220 of ^Borg 06:29, 4 August 2013 (UTC)

Quick clarification/correction. Marsupials *are* mammals. Certified, paid-in-full, card-carrying mammals. The distinction you wish to draw between marsupials like kangaroos and possums and other mammals like humans, goats, rabbits, dogs and elephants is the difference between marsupials and placentals. (Here we should also mention monotremes, which are also true mammals, but are considered neither marsupials nor placentals.) - I agree, though, that looking at (modern) taxonomy, as refelected in the trees given in most taxonomic articles, is probably the best way to get a sense of how closely related things are, and what sort of diversity you get from the common anscestor. -- 71.35.121.78 (talk) 17:42, 3 August 2013 (UTC)

Whoops, IANAZOS! (I Am Not A Zoologist Or Similar!) Corrected! Thank you 'IP 71.' --220 of ^Borg 06:08, 4 August 2013 (UTC)

Another correction: Our common grandfather with kangaroos is apparently 150 million years old, not 160. Not sure if that was a typo, or if there was something in that Google book I didn't see (says I reached my viewing limit, which is apparently zero). Strange to hear it was about 80 million years before we split from mice. Can't judge a book by its cover, I guess. InedibleHulk (talk) 05:53, 4 August 2013 (UTC)

Actually, I suppose either could be considered a good enough guess. I see the first link went with 160. Ten million years seems like a long time, but it's small, percentage-wise. I'm sure the exact answer doesn't end in round zeroes, whatever it is, but we'll never know the exact one. InedibleHulk (talk) 06:05, 4 August 2013 (UTC)

Do marsupials carry their cards in their pouches ? :-) StuRat (talk) 22:13, 3 August 2013 (UTC)

The kangaroos native to the Greater Nottingham area of the UK (!) apparently do. -- Jack of Oz ^{[pleasantries]} 22:34, 3 August 2013 (UTC)

Naturally, they don't have wallets, though they can be made into wallets. (and coin purses) --220 of ^Borg 06:08, 4 August 2013 (UTC)

Yes, I recall Craig Ferguson using a kangaroo's "coin purse" as a prop on his show. :-) StuRat (talk) 22:03, 5 August 2013 (UTC)

Thanks, people. It all helps. These creatures have baffled me for long enough! InedibleHulk (talk) 05:45, 4 August 2013 (UTC)

What part of your brain is "You"?

Is there a section of your brain that contains nothing but your knowledge that you are you? — Preceding unsigned comment added by 174.65.3.227 (talk) 06:50, 3 August 2013 (UTC)

There doesn't seem to be any one part of the brain responsible for the sense of self (despite what popular science books often tell you, for most tasks, activity is spread to some extent in pockets across the brain, and the precise pattern can vary from person to person and even thought to thought). Nevertheless, neural basis of self has a lot of information you'll probably find interesting. Smurrayinchester 06:58, 3 August 2013 (UTC)

You may also be interested in the philosophical mind-body problem. SemanticMantis (talk) 13:59, 3 August 2013 (UTC)

I recommend Consciousness#Neural_correlates which covers this exact issue. SteveBaker (talk) 14:17, 3 August 2013 (UTC)

Maybe interesting in this context: persons with split-brain . In some situations two identities seem present, for example one half slapping the other half's hand when it interferes during a test. http://www.legiontheory.com/split-brain.html Ssscienccce (talk) 15:39, 3 August 2013 (UTC)

• Your question is a category mistake. Most people equate themselves with their consciousnesses (potential and active) which is not a physical part of your brain like a neuron, but a relationship between your body and the world. This is in a similar way metaphysically that your bank account balance is not a drawer, but a relationship between you and your bank. "You" are an emergent phenomenon of your body. μηδείς (talk) 20:52, 3 August 2013 (UTC)

As I read it, the question is asking whether there is a part of the brain responsible for the sense of personal identity. It's a difficult question, partly because we have no real understanding of the way our brains assign identity to parts of the world in any respect. Looie496 (talk) 21:11, 3 August 2013 (UTC)

There are parts of your brain, which, if destroyed, will cause you to lose your selfhood in some sense, such as the ability to make command decisions with your frontal lobe, or your ability to make new memories or recall old ones. But these are all parts or faculties of your self. Even Terri Schiavo still has a certain self after the trauma she suffered. μηδείς (talk) 21:22, 3 August 2013 (UTC)

I've pondered this for years, mostly in the form of worrying whether this part, if it exists, will be absorbed by a tree's roots after I die. I don't ever want to even be vaguely aware that I'm wood for the foreseeable future. That's still all I know for sure. InedibleHulk (talk) 06:12, 4 August 2013 (UTC)

There isn't a shred of scientific evidence that would support your concern; i.e. once you have decomposed, there is no scientific evidence that your consciousness persists. The rest is religion and superstition, not science. -- Scray (talk) 13:26, 4 August 2013 (UTC)

Before even that. Electrical signals through the brain are what makes thought possible. The definition of death in most parts of the world is "brain death" - defined as the time when no electrical activity is detected in the brain. At that point, there can be no more consciousness. So you'll certainly be unaware of anything beyond that point. Think of it like a computer (which is what your brain mostly is) - when you turn off the power, all of the programs stop running. Even though the computer is still fully functional - without power, it can do no work. Same deal with the brain. SteveBaker (talk) 14:07, 4 August 2013 (UTC)

Thanks for the assurance, but maybe I should have been clearer. I'm not talking about my "self" as my thoughts, memories and self-image. I'm fairly certain that's erased. But there's some reason "I" am locked to this particular body rather than you or the next guy (or your's or the next guy's). Maybe associating with just one brain is an automatic consequence of having/being that complete brain. But maybe the awareness is only the piece the consciousness (or whatever mysterious senses trees have, if any) is built around (like a computer's non-volatile memory), as essential and recycled as the pieces that give physical form to new life. The lack of evidence for this is somewhat comforting, but the lack of proof against it leaves me wondering. No big deal, I guess. I won't remember worrying about it, anyway. InedibleHulk (talk) 08:48, 6 August 2013 (UTC)

Yes, but from the computationalist point of view, you could still argue that you will always find yourself subjectively alive in the World as it existed before you died. If what we are is the program that the brain is running and if the hardware doesn't matter, then you can look at the World as it exists now and say that some machine is executing some particular program, but you can also apply the time evolution operator to the entire World and argue that the World as it is exists now is a scrambled version of the World that existed yesterday, so there are then machines that execute different programs which are experiencing yesterday's World. Count Iblis (talk) 15:41, 4 August 2013 (UTC)

Or just "No". SteveBaker (talk) 21:46, 4 August 2013 (UTC)

What is "your knowledge that you are you"? If you mean the learning of a name, perhaps you can rummage about in the hippocampus for it. The argument can certainly be made that you aren't you from a different time in your life, either physically or mentally, and that you merely have access to some memory of your former selves. In the opposite direction, all people may be instances of the same algorithm, manifestations of a common atman. In addition to these things I entertain a fringe theory of the soul as related to a progression of parallel universes; but parallel universes are not subject to scientific investigation. Wnt (talk) 20:40, 5 August 2013 (UTC)

You have two insulae, one on either side of the brain. Each is buried at the bottom of a deep, almost horizontal fissure that separates the temporal lobe (the large region above your ears) from the rest of the brain. Most of the brain's cortex {the wrinkled gray matter containing the nerve cell bodies) lies on the surface of the brain hemispheres, but the insulae are "islands" of cortex, buried deep within each hemisphere. "Insula" is Latin for "island".

This "insular" cortex seems to be involved in awareness/consciousness. Five or six years ago I noticed a report of some brain-scans, where the researchers inflicted mild pain on the subjects, which, as usual, activated the anterior (front) and middle portion of each insula and the other parts of the pain network - the pattern of brain regions that is activated by pain. Then the researchers presented something so interesting to the subjects that they were temporarily distracted from the pain. As the subjects lost consciousness of the pain, the anterior insula activity returned to the default level.

AD (Bud) Craig proposes that this area is the key to consciousness, and so self-consciousness. In this 2011 interview he discusses his theory, as explained in his (very difficult) much-cited 2009 paper. --Anthonyhcole (talk · contribs · email) 21:37, 5 August 2013 (UTC)

One article of interest might be Philosophical zombie (that's what a fully functioning "human" without consciousness would be called). You might also wish to read some blog posts (many linked from [3]) by Edward Feser (red link - I wonder if he would be notable in sense of Wikipedia:Notability..?), where, in effect, he explains why your question makes no sense. At least from perspective of Aristotle and St. Thomas Aquinas. --Martynas Patasius (talk) 22:11, 5 August 2013 (UTC)

R/C control of a 12v drive motor

I am working on a cart that I would like to operate by R/C. It would drive ,reverse and steer hopfully using hobby R/C transmitter and reciever. The current draw for the driver motor is 11 amps. This is to much current for the receiver contacts. So, I need a way to vary the drive motor speed, reverse this motor as well as control the motor that would handle the steering. If this is feasible, I would like to know the following:

1. What type of relays (drive & steering) are needed?
2. Should the relays be of a latching type?
3. can you reccomend relay part numbers that might be used? — Preceding unsigned comment added by Campy2 (talk • contribs) 13:24, 3 August 2013 (UTC)

I wouldn't use relays...those are ON/OFF devices and to drive this thing in a reasonable fashion, you'll need analog controls.

The simplest "do it yourself" way to do this if you are clueless about electronics is to rig up a rotary potentiometer to control speed and to use an R/C servomotor to turn the knob...that avoids any complicated electronics and reduces the problem to a mechanical matter.

It's hard to comment on steering without knowing how this machine steers - are you doing skid-steering (by having one motor for the wheels on one side of the cart and a separate motor for the wheels on the other side) or are you turning the wheels as you would on a car? The former is fairly easy because you just need two speed controllers and you don't have complicated linkages to rig up.

This gizmo (for example) provides two 20Amp motor drives at anywhere from 7v up to 30v and can be controlled from an R/C receiver. At $175, it's not cheap...but it's a one-stop solution that solves all of your problems in one go. That's just the first one that Google turned up - I'm sure there are many robotics parts vendors making and selling such things - so you should probably shop around for a cheaper one.

SteveBaker (talk) 14:14, 3 August 2013 (UTC)

Chinese shops are cheap, which may also reflect the quality, but still.. http://www.hobbyking.com is one, there's also a search engine for such sites: http://chinaprices.us/ give in "speed controller 20A" and you get a listing of sites with the component , price and conditions. Starts at $8.13, shipping included. Obviously not so versatile as the one Steve mentions; only one motor, max 16v and 20A continuous or 25A peak and needs an R/C receiver.. Ssscienccce (talk) 15:59, 3 August 2013 (UTC)

Usefulness and accuracy of racialist website

http://www.geocities.ws/racial_reality/race.html This site, is it's racialist view true to current science? I'll quote part of the above page below:

"Anti-racist PC agendas and the American Anthropological Association's recent confirmation of the unity of the human species have led to the belief that race is a socio-political invention that promotes racism. An ironic accusation since the denial of the science behind race is what's politically motivated."

The above site is also claiming that there is aside from genetic a morphological basis for race and that race has a taxonomic significance, it also holds that the works of Carleton S. Coon are very relevant to the understanding to race. — Preceding unsigned comment added by 76.68.41.170 (talk) 13:42, 3 August 2013 (UTC)

See our articles Scientific racism and Race and genetics. AndyTheGrump (talk) 13:49, 3 August 2013 (UTC)

Will do, but any comments on just the above site? — Preceding unsigned comment added by 76.68.41.170 (talk) 13:53, 3 August 2013 (UTC)

Wikipedia would not consider a geocities site a reliable source. SemanticMantis (talk) 14:01, 3 August 2013 (UTC)

Is the information on said site good though? — Preceding unsigned comment added by 76.68.41.170 (talk) 14:03, 3 August 2013 (UTC)

The website does not present a balanced view of the current perspective on the issue. AndyTheGrump (talk) 14:08, 3 August 2013 (UTC)

Would you say that the site uses good sources? — Preceding unsigned comment added by 76.68.41.170 (talk • contribs) 14:15, 3 August 2013‎

Cherry-picking sources to supposedly prove a point is never good. AndyTheGrump (talk) 14:18, 3 August 2013 (UTC)

There's also one question I have about the above site's claims, are Mongoloid, Caucasoid, Negroid, Australoid and Capoid actual viable taxa? — Preceding unsigned comment added by 76.68.41.170 (talk) 14:29, 3 August 2013 (UTC)

They are not recognised as such. AndyTheGrump (talk) 14:30, 3 August 2013 (UTC)

Does race have a taxonomic basis then? — Preceding unsigned comment added by 76.68.41.170 (talk) 14:47, 3 August 2013 (UTC)

No. AndyTheGrump (talk) 14:50, 3 August 2013 (UTC)

• It's an oversimplification to deny the validity of anything that has to do with race. A look at Y-DNA haplogroups and Mt-DNA haplogroups show that humans do separate roughly into African and extra-African populations. Of the extra-African populations, some retain early traits (Negritos, Australians, New Guineans). Earlier old-adapted groups exist in Siberian and the Americas. In the Eurasian west blond hair and blue eyes arose, probably due to sexual selection, while in the east the epicanthic fold perhaps arose for the same reason. Continental and subcontinental populations will have distinctive blood types and markers [4] and resistance for various diseases such as tuberculosis and malaria. None of this is false, although little of it is very important, and its implications are only statistical, with a huge amount of variation and exception. The problem academically is the overreaction on the left to prior invalid political arguments made on the right. Luigi Luca Cavalli-Sforza's work on the correspondences between genetics and language is impeccable, Carleton Coon's work is rigorous, if merely descriptive and speculative. He's certainly a must read if this sort of topic interests you. And it does interest a lot of people, in the same way people collect rocks or figurines; people are fascinated by variation and classification. μηδείς (talk) 17:22, 3 August 2013 (UTC)

• Does the site claim that any particular race is superior to the others? If so, then it's automatically bogus. The pre-emptive quote "Anti-racist PC agendas..." is particularly telling. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:50, 3 August 2013 (UTC)
  • Our taxonomy article says, "Taxonomy is the academic discipline of defining groups of biological organisms on the basis of shared characteristics and giving names to those groups." The name of our own group is the species Homo sapiens. Anyone in the species with functional reproductive systems can mate with an opposite-sex member of that group likewise having a functional reproductive system, and that mating will produce another member of Homo sapiens. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:56, 3 August 2013 (UTC)

Taxonomies don't really work well at a below-species level, since branching implies genetic isolation, and true isolation is speciation, while our models have multiple migrations with at least three into the Americas, various ones back into Africa by pastoralists (all the Way down to the Zulu of the Cape by way of the Nile, across the Sahel, and down the slave coast. Europe was invaded by the PIE peoples from the Eurasian Steppe followed by the Huns/Bolgars/Turks/Mongols out of Central Asia. The latter groups also invaded China Korea and Japan in various waves. So strict taxonomies are very much vague approximations. μηδείς (talk) 20:37, 3 August 2013 (UTC)

• I'm not sure if you want the site reviewed or just that page. That page is about results from [5] (online at the author's site) and obviously you'll get more respect quoting Science than quoting "Racial Reality website". But skimming the website's page I didn't notice them saying anything too outrageous - we know that you can tell what race someone is by looking at them, and the same is going to be true if you do AMOVA on their genes. It crushes what is almost a strawman - the claim that race is purely a fiction. This isn't really something that is actually believed; it is more the result of some well-meaning people saying factual things to dismiss the role of race without clarifying the things that give it some meaning, and other well-meaning people summarizing that down without realizing what was being left unsaid. To be clear, you can tell what race some people are by looking at the shape of their skull ... which would seem to imply different brains ... the problem is, phrenology never worked. It's by no means obvious why it never worked - given how easy it is for a small injury to cause major disability, you'd think that any variation in the brain is super important. Yet in practice there are huge internal variations including having large portions outright missing that can have no obvious effect on the person's intelligence or behavior. When brains are consistently smaller (women) the function is no different even on average. The uniformity of human general intelligence is one of the great mysteries of science. Wnt (talk) 05:00, 4 August 2013 (UTC)

Is it true that Carleton Coon's work is still useful in the study for race? Also, isn't Peter Frost's hypothesis is not more popular than others (IIRC)? And if there is an answer to this, how many races are there based only on biology, and how they are delineated, and can looking at DNA tell one their race. Also, since race does exist, can it mean different traits in different races, such as intelligence or capability? Most of these questions are related to things asserted on the site. — Preceding unsigned comment added by 76.68.41.170 (talk) 16:44, 4 August 2013 (UTC)

Coon's work predates the genetic study of human populations. For that reason it is of interest now historically, in the same was as the work of Georges Cuvier or John James Audubon. His data may still be of some interest. His theories were never tested or refined against the genetic data started to become available the decade he died. He shouldn't be quoted now as a theoretical authority. μηδείς (talk) 17:37, 4 August 2013 (UTC)

So does craniofacial studies of Coon hold any water in current scientific field? — Preceding unsigned comment added by 76.68.41.170 (talk) 18:30, 4 August 2013 (UTC)

See Carleton S. Coon. Personally, I don't have the patience to figure out his implications and their role in political development; my feeling is that if Mawr had a good word for it, it wasn't bad science, but of course, having genome sequence from many individuals really matters. Wnt (talk) 19:32, 4 August 2013 (UTC)

You mean Mayr. You don't get better than a recommendation from him. μηδείς (talk) 19:46, 4 August 2013 (UTC)

Cranio-facial studies provide data. One can then say certain features are typical of and make a certain population distinct. To abstract from such studies and posit a theory of the origins of the white race is just that, theorizing. Some current data agree with Coon in various aspects--whites apparently do have Neanderthal admixture (but so do all extra-Africans). Mediterraneans do form a coherent wave out of the Middle-East according to Cavalli-Sforza. But reams of other new data have no place in his theories--for example, the PIE peoples are a late introduction into europe, and if one identifies them with the true whites one use modern data to say Mediterraneans invaded their land. It is not really helpful to keep asking if he is authoritative. Topics like this require years of broad study--neither acceptance of an authority figure nor ideological dismissal. Ignore the man and look at the data. μηδείς (talk) 19:46, 4 August 2013 (UTC)

What ideological dismissal? I asked the question on a scientific basis, would you say that his data would be good proof for the existence of race? And if his racial theories are actually proven in some fashion. — Preceding unsigned comment added by 76.68.41.170 (talk) 22:09, 4 August 2013 (UTC)

I did not accuse you of dismissing things based on ideology, I suggested one not do it. Race is a concept whose usefulness depends on how you define it and in what context. If the coroner tells you the body was that of a black female between 18 and 30 you don't ask him to prove races exist; neither do you actually expect proof of the existence of races if someone tells you black people bear the Mark of Cain. μηδείς (talk) 17:18, 5 August 2013 (UTC)

But then what are the objective scientifically determined races? — Preceding unsigned comment added by 76.68.41.170 (talk) 21:05, 5 August 2013 (UTC)

Zyprexa interacting with vitamins.

Can Zyprexa interact with vitamins? Pubserv (talk) 18:32, 3 August 2013 (UTC)

It is a very simple matter to google that question; we are not medical experts, and if you have Zyprexa you have a doctor who prescribed it and a pharmacist who filled it, both of whom will answer your question. μηδείς (talk) 20:44, 3 August 2013 (UTC)

I don't have access to Google on my computer. Pubserv (talk) 08:26, 4 August 2013 (UTC)

Are you Cuban? What kind of people has access to Wikipedia but not Google? OsmanRF34 (talk) 12:04, 4 August 2013 (UTC)

No. Those people that have restricted access to websites. I hope I'm not the only one. Have, not has. Pubserv (talk) 19:11, 4 August 2013 (UTC)

No. It's has not have. This kind (of people) has access to something. OsmanRF34 (talk) 01:52, 5 August 2013 (UTC)

• I have encountered other WP editors with the same restrictions, e.g. access only at work, which allows WP but not Google. -- Scray (talk) 19:30, 4 August 2013 (UTC)

How does that work??? - is WP on a whitelist, or is Google on a blacklist? Is Ixquick allowed to them? How are they supposed to use the web at all without a search engine? Wnt (talk) 01:55, 5 August 2013 (UTC)

How? Do you need a search engine when you only have access to 4 sites/themes, like me? Pubserv (talk) 18:11, 7 August 2013 (UTC)

How much vitamin B6 for akathisia?

How many tablets are needed to relieve akathisia? Or how much? Pubserv (talk) 19:08, 3 August 2013 (UTC)

I"m sorry, we're not allowed to offer medical advice. SteveBaker (talk) 19:17, 3 August 2013 (UTC)

You need to see a doctor about that. Whatever he deems the right treatment to be, your doctor would recommend a dosage based on appropriate factors. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:01, 4 August 2013 (UTC)

I can't see a doctor. Pubserv (talk) 08:25, 4 August 2013 (UTC)

Then ask your pharmacist, they can also provide qualified advise, and they are free. OsmanRF34 (talk) 12:02, 4 August 2013 (UTC)

I can only see a psychologist, that's not a pharmacist, right? Pubserv (talk) 19:14, 4 August 2013 (UTC)

What kind of people has no access to a pharmacist? OsmanRF34 (talk) 01:54, 5 August 2013 (UTC)

They might at least have a clue, and could have a direct conversation with you about it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:59, 4 August 2013 (UTC)

See here. Count Iblis (talk) 19:36, 4 August 2013 (UTC)

I would advice you against trying this out yourself unless a qualified doctor prescribes it. I would not go to a farmacist unless you live in a country where they can be trusted to give qualified advice (in most of the Third World countries farmacies cannot be trusted, they are just interested in selling as much as they can). The potential problems that a doctor will have to look into are the following. The dose you need to take is of the same order as the dose where toxicity symptoms can start to manifest itself if you were to use this long term. Also, for long term use, even if you take large but not extremely large near toxicity level dosages, you should normally not do that for any specific B-vitamin (with the exception of B12) and instead use a vitamin B-complex. The different B-vitamins have a similar structure and if you take a large dose of one, your body will increase the excretion of not just that one but also of other B-vitamins, causing you to be come deficient in these other B vitamins, even if you get normal dosages of these other B vitamins via your food.

These are just some potential problems that a doctor will have to verify are not going to be relevant in your case during the course of some specific treatment. Count Iblis (talk) 13:18, 5 August 2013 (UTC)

What's a "farmacist" -- a farmer who grows medical herbs? 24.23.196.85 (talk) 04:46, 6 August 2013 (UTC)

• Our article has a section Vitamin_B6#Toxicity - I would say this and especially the sources it cites are advisable to read if you're contemplating any B6 treatment, with or without a doctor's help. (The sourcing is still weak in places...) Wnt (talk) 20:26, 5 August 2013 (UTC)

August 4

# of days Medicare pays in rehab

My friend was told Medicare would pay only up to 20 days in rehab. Is this new? It used to be 30 days.```` — Preceding unsigned comment added by 71.232.189.242 (talk) 01:14, 4 August 2013 (UTC)

I believe that is true, and then it pays 80% out to 100 days. But I may be wrong. Bubba73 ^{You talkin' to me?} 01:43, 4 August 2013 (UTC)

It's probably worth pointing out that there is more than one country in the world with a health scheme called Medicare. And, not surprisingly, they're not all the same. HiLo48 (talk) 02:27, 4 August 2013 (UTC)

Yes, but it is unlikely that someone from Massachusetts would be interested in any program from outside the U.S. --Jayron32 03:08, 4 August 2013 (UTC)

North America (USA & Canada) plus Australia, at least use 'Medicare'. (National Health Service(NHS) in England) --220 of ^Borg 06:52, 4 August 2013 (UTC)

Missed Medicare Resources in Hong Kong. --220 of ^Borg 07:23, 4 August 2013 (UTC)

In Canada it is only called medicare in New Brunswick. TFD (talk) 07:31, 4 August 2013 (UTC)

Bee-eater pic

In this picture of a European bee-eater, what's that butterfly it's holding in its beak? 24.23.196.85 (talk) 05:55, 4 August 2013 (UTC)

Looks like Vanessa cardui. What you see are mostly the undersides of the left fore- and hind-wing. --Dr Dima (talk) 01:49, 5 August 2013 (UTC)

Thanks! I prob'ly should've known this -- it's one of the most common lepidopterians in the world (better known as the Painted Lady). BTW, does anyone know whether it's toxic like the Monarch? I've checked the article, and it says nothing about that. (It does say in the Bee-eater article that the bird avoids certain toxic insects, but doesn't say which ones -- only that it (obviously) doesn't avoid bees, which are also quite toxic.) 24.23.196.85 (talk) 05:31, 5 August 2013 (UTC)

No definitive reference found either way, but in 45 years of active interest in lepidoptery, I've never seen it suggested that this or related species in Great Britain are significantly poisonous to birds. {The poster formerly known as 87.81.230.195} 212.95.237.92 (talk) 14:10, 5 August 2013 (UTC)

...and the mere existence of that photo strongly suggests that these birds don't avoid them! SteveBaker (talk) 15:28, 5 August 2013 (UTC)

Presuming, of course, this bird isn't suicidal, stupid or visually impaired. From the frequency other species crash into my clearly dirty windows, I'd say "seems to suggest". InedibleHulk (talk) 09:36, 6 August 2013 (UTC)

It could also be that the Bee-Eater is immune to certain toxins found in certain butterfly species (the article says it's immune to bee and wasp venom, so it could also be immune to butterfly toxins). If so, it's not the only species to have this kind of immunity -- the Black-headed Grosbeak, for example, can even eat the highly toxic Monarch butterfly without harm to itself! 24.23.196.85 (talk) 01:23, 7 August 2013 (UTC)

posthumous fatherhood from culled sperm

Is it possibe to make a dead man father children through Testicular sperm extraction? Pass a Method talk 12:34, 4 August 2013 (UTC)

That process requires live sperm, so it will be progressively less successful as the sperm die following the death of the man. The time from death until there are no viable sperm will depend on many conditions, including the condition of the testicles at the time of death. This search for direct answers was unrevealing. -- Scray (talk) 13:22, 4 August 2013 (UTC)

Was the sperm extracted before or after death? A dead man can have previously donated sperm the normal way, and had it properly frozen. The thawed sperm can then be used to posthumously conceive a child. --Jayron32 01:54, 5 August 2013 (UTC)

Would a man who froze to death and stayed that way be a candidate? InedibleHulk (talk) 09:38, 6 August 2013 (UTC)

I suspect it would depend on how he got that way. Generally sperm banks freeze the stuff really quickly in liquid nitrogen or something. A very slow freezing might somehow damage the material - or freezing to the wrong temperature might be an issue. I'm not 100% sure about that - but it's certainly a potential problem. SteveBaker (talk) 16:39, 6 August 2013 (UTC)

Is it possible to study human language development

Is it possible to study human language development by filming a human from birth to death and recording down all visual and audio signal that a human has come across in their lifetime. This capability must surely be possible with the budget of a large country like USA. The source of data will be useful for scientists for hundreds of years to come to analyse the psychological development of a human. So why was this not initiated? Surely the scientist around the world can easily obtain funding to perform the experiment. It cannot be because of privacy because the data(film) will never be released to the general public. 220.239.51.150 (talk) 15:38, 4 August 2013 (UTC)

Sure it's possible, it just isn't very practical (not to mention that it raises a plethora of ethical questions). Anyway, the ref desk really isn't the place to speculate on such things... 70.112.97.77 (talk) 16:18, 4 August 2013 (UTC)

Bear in mind that a year of film takes a year to watch. Looie496 (talk) 16:28, 4 August 2013 (UTC)

Almost certainly the technology exist to make it technically possible. (I even recall a science fiction story where everything and everyone was recorded 100% of the time.) But, as IP 70. says, it raises ethical questions. Would any parent consent to a child being filmed 24/7 from birth? Humans tend to find privacy pretty important Sounds a bit like The Truman Show --220 of ^Borg 16:54, 4 August 2013 (UTC)

The technology to record that much stuff is too recent to have been used to record an entire human lifetime...so no, it can't possibly have happened. It has, however, been done for shorter periods quite recently. For example, this excellent TED talk discusses recording all of the activity in an entire house as a child goes from birth to being able to talk. He tracked every single time his child made a noise when water was involved and got a beautiful series of audio snippets that showed how the child went from having no speech to being able to say the word "WATER" perfectly. SteveBaker (talk) 21:45, 4 August 2013 (UTC)

Classic link there from Steve, but it should be noted that it's the researcher's own child, so he has a lot more leeway. Raising a child so you can keep a camera on it for its whole life, so you can use it to extract data, sounds more like the subject of a Jodi Picoult novel than a real research experiment. If you did it at a university, you would have to go through an ethics committee, and they would be likely to block it, I would assume. Privacy is absolutely an issue, because at least the researchers would need to have access to the data, and they do not enjoy unfettered access to anyone's private world. They are not the CIA, after all, nor even anything close. The child, upon reaching almost any age, would have the right to withdraw consent, and that would simply make it pointless. Also it would have to be followed through by different researchers. I would say any research like this is a long way off. IBE (talk) 13:32, 5 August 2013 (UTC)

How would that help much in studying language development? Every parent in the world has a good idea of what their child hears, from the moment of birth to early childhood. That knowledge doesn't give them any insight on how the brain is structured, how sound is processed, the role of nature vs. nurture, whether a universal grammar exists, whether a critical period exists for language acquisition, etc. A better experiment would be to deprive a child of any language and see if they can still a language after childhood. This "forbidden experiment" has been done before, and the answer seems to be no: see Genie (feral child) and Victor of Aveyron. --Bowlhover (talk) 08:11, 5 August 2013 (UTC)

I think there is something to be gained by careful observation over time - and being able to go back and note carefully how speech transitions from one phase of development to the next would be valuable. For example, my son started off saying single words - then went to beautifully, grammatically correct phrases - then seemed to take a step backwards and start saying grammatically incorrect phrases before eventually correcting those errors and becoming fluent. The reason for this is that the first grammatically correct phrases were being memorized in one chunk - like they were a single word. Only later did he start trying to form new phrases - and having to actually master grammar. This tells us all sorts of interesting things - but having noticed that change, I was unable to go back and see how it started. There is no doubt in my mind that having a record of everything the child ever said would be useful in understanding the stages of development. But as Been Emotional said - it's an ethical nightmare to do that. Sure, researchers would love to have all of the episodes of The Truman Show on DVD - but that's not going to happen. SteveBaker (talk) 14:17, 5 August 2013 (UTC)

It occurs to me that we should mention Lifelogging.

This is the idea that people might voluntarily record everything that happens to them (to at least some degree). Some of those people attempt to record everything they hear and see (including their own voices) - and often other data like body temperature, heart rate, blood pressure and so forth. I suppose that if they chose to make that vast pile of recordings available towards the ends of their lives, it might tell researchers quite a bit. The problem, again, is that this is a relatively new idea - and the technology to store all of that data and to capture it using a portable device is still non-trivial. Certainly it's becoming possible though. The Google Glass headset can record sound and video and stream it continually via your cellphone to some kind of "cloud" storage system. I'm not sure the battery life of headset and phone are yet good enough to record everything on a 24/7 basis without recharging issues...and there might be times when cellphone access was patchy or unavailable - but with spare batteries and an acceptance that some data might be lost - this is becoming plausible. Another issue is that this is something that's really only being done by adults - so it'll miss that person's childhood language development - having a child wear something like this from birth is clearly unreasonable. SteveBaker (talk) 15:26, 5 August 2013 (UTC)

Do boron exists in asteroids?

I want to make a science fiction story that is based on polywell reactors for space energy, and so because it uses aneutronic fusion its fuel is hydrogen and boron. There is a lot of hydrogen in space, from ice electrolysis, but I never find any reference to boron in space either in asteroids or other planets 140.0.229.26 (talk) 15:55, 4 August 2013 (UTC)

See this paper for a review of the data on boron abundance in meteorites -- the best source of evidence. The answer seems to be yes, but not in very high concentrations. Looie496 (talk) 16:25, 4 August 2013 (UTC)

Where does the element boron come from? A few physicists from University of Illinois have already fact-checked and veried some of the claims in our boron article. Like those professional physicists, I (as a non-practicing physicist) have not ever heard much talk about stellar nucleosynthesis of boron. (Compare, say, hydrogen-burning, lithium burning, nucleosynthesis production of sodium, or iron... these were all homework problems in one astronomy-related class or other, and the details stick in my mind!) But I remember no discussions about boron! This is apparently because boron isn't commonly made by stellar nucleosynthesis - at least not by the major reactions. Boron is made by a more esoteric process, spallation of lithium by high-energy cosmic rays. As such, it's going to be much more rare everywhere in the universe: on earth, in asteroids, in stars. Nimur (talk) 17:07, 4 August 2013 (UTC)

Are you sure you're not thinking of Beryllium? 202.155.85.18 (talk) 01:17, 5 August 2013 (UTC)

I frequently think about beryllium, but in the instance above, my thoughts, discussion, and the source I linked to were related to boron. Some of that discussion also applies to beryllium - which is commonly produced by cosmic ray spallation, because (like boron) production of beryllium by stellar fusion requires a very low-probability reaction. I found this website from the folks across the bay: "how did the various chemical elements of the periodic table form?" Nimur (talk) 03:07, 5 August 2013 (UTC)

I have nothing to add here. I just really like the phrase "I frequently think about beryllium". You should get that on a T-shirt, or in Latin on your coat of arms. APL (talk) 11:27, 5 August 2013 (UTC)

"Soleo cogitare beryllium" - sounds pretty good! SteveBaker (talk) 20:18, 8 August 2013 (UTC)

I'm getting a mental picture for your story: A team of 20 mules, in spacesuits of course, hauling one of those asteroids away. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:55, 4 August 2013 (UTC)

Seems good enough. It seems that the story will be like a huge evil company controlling all boron mines on earth and the researchers found out about boron on space so they are trying to escape from that evil company monopoly, ohh wait seawater have a lot of boron.... Is there any way to extract boron out of seawater? 140.0.229.26 (talk) 00:42, 5 August 2013 (UTC)

Yes, but it seems the reason for it is to make safe drinking water, not to get the stuff.[6][7] Clarityfiend (talk) 00:56, 5 August 2013 (UTC)

As a matter of fact, it's also possible to extract pure boric acid from seawater by means of liquid-liquid extraction with ethohexadiol (formula C₃H₇CH(OH)CH(C₂H₅)CH₂OH) or similar chelating agents; however, for economic reasons this is normally done with concentrated salt-lake brines rather than seawater. 24.23.196.85 (talk) 01:31, 6 August 2013 (UTC)

Fooling Archimedes?

The other day I got into a debate with a friend concerning the Archimedes Principle. I raised the point that in some circumstances a carefully constructed object could be devised to fool the test - the interior of the object could simply be a combination of materials of different densities that balance out to the target density; for example, a hollow (ie: air filled) gold plated cube with just the right amount of lead applied to the interior walls. It makes perfect sense to me, but my friend seems to think that I'm horribly mistaken. Can someone here help settle the debate? 70.112.97.77 (talk) 16:05, 4 August 2013 (UTC)

Gold (19.30 g·cm⁻³) is denser than lead (11.34 g·cm⁻³). AndyTheGrump (talk) 16:09, 4 August 2013 (UTC)

To expand: the problem given Archimedes was to determine if a solid object was made of gold. Lead is much less dense than gold. You would need something denser than gold as well as lead to make something with the same density as gold. What you are saying would be right in other circumstances but the thief would have had to use something like osmium or platinum with the lead, which they didn't have at the time and are extremely expensive. Dmcq (talk) 16:13, 4 August 2013 (UTC)

Sorry, yes, I really should have consulted the periodic table before posting! Okay, so assuming that some denser material were available then it would be possible. Thanks! 70.112.97.77 (talk) 16:27, 4 August 2013 (UTC)

Sure, fooling the Archimedes test that way does indeed work. With some simple assumptions like the cavity is located so it does not change the object's center of mass.

In the particular case of fake gold bars, type tungsten gold bar or fake gold bar into your favorite web search engine. Tungsten is so slightly lighter than gold that simple tests have a hard time detecting it. For fake gold you'll need a metal that is both heavier and cheaper than gold (the periodic table leaves you little choice there), and can't easily be told apart from gold (electric conductivity, behavior in electromagnetic fields (see metal detector), doesn't give off radiation, etc). And someone will quickly figure out how to detect cavities inside a gold bar if those start appearing on the market - tap it, if it rings like a bell, well, uh oh... 88.112.41.6 (talk) 20:29, 4 August 2013 (UTC)

Above was mentioned center of mass... but a proper fake should also preserve the moment of inertia! Two objects with the same center of mass, but different moments of inertia, behave very differently. Just by swinging a hollow metal sphere around a little bit, or rolling it around... we could measure a difference, even if its average density and center of mass were perfectly matched to another solid sphere of the same outer dimension. I'd wager a gold brick that most people could even "feel" the difference, without rigorously measuring it.

We could enumerate other physical properties we might test: any imperfection in mimicking the correct thermal capacity or thermal conductivity won't make it past a few really "low-tech" tests. Nimur (talk) 22:30, 4 August 2013 (UTC)

The density of tungsten is very similar to that of gold and the bar sounds about the same, an easy way to find if a bar contains tungsten is to use a strong magnet, gold is diamagnetic, it repels a magnet, whereas tungsten is paramagnetic and so is attracted. See [8] Dmcq (talk) 23:28, 4 August 2013 (UTC)

I don't think "Archimedes' Principle" is the phrase you're looking for. That describes a property of buoyancy, not the "Eureka" moment where he realized that an object displaces a volume of fluid equal to its own volume. (And then used that to calculate an objects density, thus proving it was made from gold.)

Perhaps that's the "horrible mistake" your friend believes you've made. I don't believe that you could construct an object that would defeat the Archimedes' Principal. APL (talk) 11:24, 5 August 2013 (UTC)

It wouldn't have been possible at the time of Archimedes to make something with the density of gold out of other materials but it is quite easy to do nowadays. That's what another contributor was saying above about searching for tungsten gold bar, people have been swindled using imitation gold bars. Dmcq (talk) 11:51, 5 August 2013 (UTC)

And of course Achemedes could have been fooled too if the object in question was hollow. His approach would say "This is not gold" - even though it might well be. SteveBaker (talk) 15:14, 5 August 2013 (UTC)

That wasn't Archimedes' task - he was trying to see if the king was being cheated. A hollow space would be just as damning as an admixture. (Though I have a feeling that in such situations, the real answer is, come up with a great experiment and describe it to further your reputation, then tell the king whatever result he wants to hear!) Wnt (talk) 18:21, 5 August 2013 (UTC) oops, that was stupid, nevermind - he'd have weighed the crown and if it were all gold, that shouldn't be punished Wnt (talk) 19:45, 5 August 2013 (UTC)

Dmcq, yes. But my point was that constructing such an object would not defeat the "Archimedes' Principle", it would defeat the gold-test that Archimedes invented while taking a bath. They're not the same.

Archimedes is famous for more than one thing. APL (talk) 22:19, 5 August 2013 (UTC)

What kind of insect is this?

Orthoptera on a basil leaf.

What kind of insect (an orthoptera, I suppose) could this be? It was found in Southern Germany, on a basil leaf. Thanks. --Edcolins (talk) 19:13, 4 August 2013 (UTC)

It must be a female speckled bush-cricket. Could somebody confirm? --Edcolins (talk) 20:01, 4 August 2013 (UTC)

Yes, speckled bush cricket, female from the ovipositor curving up at the back. Richard Avery (talk) 06:29, 5 August 2013 (UTC)

Thank you! --Edcolins (talk) 19:29, 5 August 2013 (UTC)

Resolved

August 5

CNC milling?

I've been running one of these 3D printers for a while now, making and selling various items, particularly decorative figurines and keyrings, and I'm wondering about trying this milling thing, opens up opportunities for all sorts of different materials. Thing is, I'm not too sure on what sort of machine I'd want, wondering at what the limits would be on these 4-axis machines, whether they would be able to carve the shapes I'd want or not. then again, would that not involve attaching the item to the machine in some way, leaving a clear mark on it? I realise I don't actually know how these machines work at all, would it be possible just to upload a 3D model file into one and leave it to do all the work, or are things more complicated with these?

213.104.128.16 (talk) 11:23, 5 August 2013 (UTC)

As far as leaving a mark where it's attached, yes, you would typically have some finishing work to do after it come off the machine, to grind/sand it down and polish it. StuRat (talk) 12:55, 5 August 2013 (UTC)

(I also have a 3D printer - and also a couple of laser cutters - and I'm about to get into 3D milling machines too - so I've done quite a bit of research into them).

There are basically two kinds of CNC milling machines - 3 DOF and 5/6 DOF. "DOF" means "degrees of freedom" and describes the number of ways in which the cutting head can move.

• A 3 DOF machine can move in three axes just like your 3D printer can - but it can't create undercuts because it's removing material from above, not building it up from below.
• A 5 DOF or 6 DOF machine can also tilt either the milling head or the workpiece (or sometimes both) to reach underneath overhangs...it can make some things that even 3D printers can't make...but even a 6 DOF machine can't make some things that a 3D printer can make because the cutting head is kinda large and can't make it into some small spaces. A 5/6 DOF machine is basically a robot arm holding an electric drill with a milling bit.

So to do most of what you can do with a 3D printer really requires a 5 DOF or 6 DOF milling machine...the snag is that those things cost an absolute fortune! Many tens or possibly hundreds of thousands of dollars. 3 DOF machines are vastly cheaper - and there are designs out there to let you make them for about the same cost as a 3D printer.

The term "4 axis" is a bit confusing. Sometimes it refers to a 3 DOF machine with the fourth axis being the rotation of the milling bit itself (which is cheating!)...rarely it means that this is a 4 DOF machine - which would be able to rotate the workpiece around one axis (like a lathe maybe) with a 3 DOF machine doing the cutting. That wouldn't get you much further than a straight 3 DOF machine. Almost certainly, if this is something costing under $10,000 dollars then "4 axis" really means "3 DOF".

To attach the workpiece to the machine generally involves clamping small pieces to the platform - which might not leave a mark - but does result in you having a block of material at the base of your object that can't be milled and may have to be sawed off by hand. For large sheet materials, some CNC machines have a vacuum table that holds the part in place. Those only work well for relatively large parts. Yet a third alternative is if you can drill a hole inside the base of the workpiece and thread a bolt into it. You can then clamp the bolt, do the milling, then unscrew the bolt at the end.

In terms of working with these machines - they are very much like a 3D printer - you can upload a 3D model and (with appropriate software to plan the tool paths) just set the machine running.

To mentally visualize what a 3 DOF CNC machine can do, imagine you had a small electric drill mounted in your 3D printer in place of the hot-end extruder. Now imagine you lower the Z table all the way to the bottom (or raise the head all the way to the top - depending on how your 3D printer works) - then put a solid block of plastic into the machine. Now, this hypothetical 3D printer could cut away material, one layer at a time by moving the head back and forth over the parts of the plastic that you don't want anymore - then raising the workpiece (or lowering the head) a fraction of an inch and doing it again. The process is kinda like 3D printing in reverse.

If you have a website someplace with pictures of the things you sell, I could quickly tell you which of them a 3 DOF machine could make.

SteveBaker (talk) 14:07, 5 August 2013 (UTC)

You could try one of the milling services on the web, just like there are 3D printing services. That would give you a good feel for what you can get done and the prices are fairly reasonable. Have you tried sintered metal 3D printing? Dmcq (talk) 15:26, 5 August 2013 (UTC)

If you want a number of the same you could try casting in metal. and of course if they can be made from sheet metal there's all sorts of other options. Dmcq (talk) 15:35, 5 August 2013 (UTC)

3D printers that can do sintered metal aren't cheap - they rely on high powered lasers, plasma arcs or something similarly expensive and dangerous to sinter the metal - and that's a very difficult problem for a cheap design. My two 100 watt (made-on-the-cheap) lasersaurs cost $8,000 each in parts alone - and 100 watts of laser power is nowhere near enough to do metal sintering. So unless you're making a LOT of money doing this, you'll be stuck with paying someone else to make the parts on a machine you'll never be able to afford!

I know of one guy who made a cheap(ish) laser-sintering 3D printer - but his machine sinters wax laced with carbon...hardly metal...but you could use his wax objects in a lost-wax casting process.

But if you're thinking about making molds and casting objects in metal then another approach is to make a two-part 3D-printed mold and use that to cast metal objects. Obviously you have to have relatively low melting point metals and do your printing with the highest melting point plastic your printer can manage...sadly ABS and PLA (which are the two plastics that most 3D printers use) both melt at around 220C - which is unfortunate because metals like tin and lead melt at temperatures at least that high - so the mold would melt and be useless. But there are a few metal mixtures that melt at much lower temperatures - yet at high enough temperature to be useful for things like jewellery and key-fobs - sadly, some of those are toxic, so you have to be careful. Field's metal might be a good choice - it melts at 62C - Woods_metal#Related_alloys gives a list that includes all of the low-melting-point metals that I know of.

Another option is to make the object itself in plastic, then make a synthetic rubber mold from it and cast using that.

If you're interested in materials other than plastic - but would like to stick with 3D printing, this stuff should be of interest. It's made from wood-pulp and formed into a filament with a binder that most 3D printers can melt. Printed objects look and feel like wood (although without any grain). Some people are investigating using 3D printers with two heads - one loaded with light colored wood filament and the other with a darker version of the same material - and actually printing fake grain into the objects they make.

Fun stuff! SteveBaker (talk) 16:04, 5 August 2013 (UTC)

I was thinking of them sending off to a service doing sintered metal like for a milling service, sorry I should have made that clear. I'd have thought buying any machines would need to be carefully justified compared to sending off to a service which specializes in doing the work. Dmcq (talk) 20:22, 5 August 2013 (UTC)

Yes, I agree that using a service that can print in difficult materials is a good option - but from the point of view of someone who is attempting to manufacture things for profit, using a service like that will sharply limit how much money you can make - they definitely aren't cheap. For the laser-cut stuff that we do, it would be about 20 times more expensive to have the product made by a service than making it ourselves. We could possibly use them for making prototypes - but unless a LARGE fraction of the final selling price is reflecting your design expertise, it's not a viable option. SteveBaker (talk) 16:35, 6 August 2013 (UTC)

Sounds good that wood material. Someone told me once they were going to use a wood effect paint and I thought they were joking - and they went ahead and got a nice wood effect with it! By the way for that wood material they can make it darker or lighter by using a higher or lower temperature when they melt it. Dmcq (talk) 20:38, 5 August 2013 (UTC)

Oooh! That's a really good idea. (Am ordering wood filament for my machine now!)...do you happen to know what temperature range is needed to produce a substantial change in color? SteveBaker (talk) 16:35, 6 August 2013 (UTC)

It says on the page you pointed to, you can range between 180°C and 245°C, [9] shows it is quite effective. Dmcq (talk) 17:45, 6 August 2013 (UTC)

Poison ivy for apes

Take a typical member of each great ape species and expose all of them to poison ivy. The human will get urushiol-induced contact dermatitis, but what about the others; are we the only species allergic to it, or will other apes also have problems? Neither article that I linked says anything about other species; I know that the plant doesn't cause problems for ruminants, but I know nothing about non-human primates. Nyttend (talk) 14:36, 5 August 2013 (UTC)

Having furry bodies helps them a lot. In order to get problems with poison ivy, it has to rub against your skin. A thick layer of fur makes that rather difficult - so I would expect that other great apes would have much less problems with the stuff than we "naked apes" do. The chemical involved (Urushiol) provokes an immune response that ultimately causes the symptoms. This article says "Deer and other animals can eat poison oak leaves without any apparent ill effect. Birds nest and find shelter in the plant. Only primates (humans, apes, chimpanzees, etc.) seem to have a reaction to poison oak." - so I guess you have an answer. SteveBaker (talk) 15:13, 5 August 2013 (UTC)

Drawback or limitation of modern synthetic theory of evolution or neo-Darwinism

What are some Drawback or limitation of modern synthetic theory of evolution or neo-Darwinism?

AmRit GhiMire 'Ranjit' (talk) 14:48, 5 August 2013 (UTC)

So, to be clear, you're talking about Modern evolutionary synthesis (which is also called "neo-Darwinism" and which is the way that evolution is understood in the last 50 years) - which (according to our article) "is still, to a large extent, the current paradigm in evolutionary biology."

The most obvious unresolved issue for me is abiogenesis. How did the first self-replicating molecule come about? Once such a thing existed, evolution became inevitable...but getting from "inert" chemistry to that is something of a leap. There are plenty of possible explanations - most of them plausible - but we don't know exactly which of them is true.

Our article Objections to evolution covers a huge array of objections that have been raised - but few, if any, are thought to be problematic by the vast percentage of scientists in the field - they are generally trivially easy to debunk using easily obtained evidence.

Evolution is one of the most solidly well-understood and verifiable theories in science - there really aren't "drawbacks" or "limitations" in the theory.

SteveBaker (talk) 15:06, 5 August 2013 (UTC)

I have to agree, there aren't really any drawbacks. There are disputes over the interpretation of such things as kin selection and selfish genes, but these are actually metaphysical disagreements--no one disputes the facts. Evolutionary psychology is ideologically controversial, but it's quite far removed from the modern synthesis itself. μηδείς (talk) 17:15, 5 August 2013 (UTC)

At least at the molecular level, the occasional impact of "Hopeful Monsters" shouldn't be dismissed entirely - things really do get abruptly reverse transcribed, recombined etc. to form dramatically new gene structures. Also, the theory doesn't really address the issue of heritable epigenetic change - the mechanisms making that possible are the products of evolution, but it means that the reaction norms of any given genotype are far more complex than previously imagined. Wnt (talk) 18:26, 5 August 2013 (UTC)

Who was Dr Price?

As a side issue to a question on the Language Desk, I found that the triple expansion engine (as used in the Titanic) seems to have been a British invention. According to History of British Shipping by Adam Kirkaldy, "Then Dr Price invented the triple expansion engine, effecting further economies in the consumption of fuel" (p.131). One was apparently fitted to SS Aberdeen (1881). Does anybody know anything about the ingenious Dr Price? His full name would be a start. Our Compound engine#History has a Spanish destroyer as the first in 1886, although it was built on Clydebank. Alansplodge (talk) 15:51, 5 August 2013 (UTC)

An article in The Quarterly Journal of Economics, "Substitution and Complementarity in Endogenous Innovation" (August 1993), discusses the rise of steam ships and cites:

• Harley, Charles K., "The Shift from Sailing Ships to Steamships, 1850-1890: A Study in Technological Change and its Diffusion," in Donald N. McCloskey, ed., Essays on a Mature Economy: Britain after 1840 (Princeton, NJ: Princeton University Press, 1971).
• Rosenberg, Nathan, Perspectives on Technology (Cambridge: Cambridge University Press, 1976). Ch. 11

I don't know whether either of these would mention Dr. Price, but they're the closest I come to any useful-seeming information so far. --some jerk on the Internet (talk) 21:00, 5 August 2013 (UTC)

I found many texts over the decades which parroted the line "hen Dr Price invented the triple expansion engine.." without any details. But the actual designer of the first successful triple expansion engine, used on the Aberdeen (1881) for high speed London-Capetown-Melbourne runs was "Doctor" Alexander Carnegie Kirk, See [http://books.google.com/books?id=m8TsygLyfSMC&pg=PA694&lpg=PA694&dq=the+aberdeen+1881+napiers&source=bl&ots=fXgwCpa8Kn&sig=A2yIROVbkJhIu-cUFElFlKDg-D4&hl=en&sa=X&ei=428AUqvXGurAyAHLloDAAQ&ved=0CFAQ6AEwBg#v=onepage&q=the%20aberdeen%201881%20napiers&f=false Biographical Dictionary of the History of Technology (2013) - Page 694. Maybe Price was one of his associates. Edison (talk) 03:52, 6 August 2013 (UTC)

Thank you both. I intend to put an entry on Timeline of steam power if nothing else. We already have an article, Alexander C. Kirk, which mentions the Aberdeen and her engines; how I didn't find it myself remains a mystery. One can imagine a muffled cry from the Aberdeen's engine room voice tube; "She cannae tak' much more Kirk!" ;-) Alansplodge (talk) 16:34, 6 August 2013 (UTC)

Epilepsy: is there a limit to how often seizures can be photoinduced?

The way I understand it, flashing lights, even TV episodes, can induce epilepsy - occasionally even first seizures in children who haven't previously experienced them. Yet epileptic seizures are typically followed by a postictal state where no seizure can be induced. What I'm wondering is, does the photoinduction actually increase the overall tendency to have seizures on a consistent basis, and if so how much, or does it just affect the timing of seizures? In other words, is there a sort of "fuel for epilepsy" that gets consumed during seizures, and the lights merely provide a "spark"? (I'm picturing a hopefully thought experiment where an epileptic al-Qaeda member is locked in subbasement 25 under Diego Garcia, in a cell with a stunning light show going day and night... by what factor are his seizures increased over the long haul?) Wnt (talk) 18:38, 5 August 2013 (UTC)

Yes, there is a sort of "fuel for epilepsy". Electrical activity in the brain depends on ion concentration differences between the interior and exterior of brain cells, and those differences run down during a seizure. Afterward they are slowly reestablished by ion pumps. And yes, seizures can increase the probability of future seizures, by means of a phenomenon known as kindling. That doesn't always happen, but it can. Seizures can be triggered in anybody by electrically stimulating the brain -- that's what happens in ECT -- but light will only trigger seizures in people whose brains are particularly vulnerable. I don't know whether there is evidence that experiencing light-induced seizures increases the probability of future seizures. Looie496 (talk) 19:04, 5 August 2013 (UTC)

Very good point about the kindling model! I suppose the question actually breaks down into two separate conditions: (a) whether photoinduction can be used (perhaps together with isoniazid, thiosemicarbazide, harman, pentylenetetrazole, 3-mercaptopropionic acid, and/or strychnine) to help induce first seizures in non-epileptics and perhaps even to "kindle" long term epilepsy, and (b) what its effect is on those who already have longstanding epilepsy. I was only thinking about the latter above, but of course, depending on the person either might be relevant. Wnt (talk) 19:27, 5 August 2013 (UTC)

Human decontamination

Hello everyone,

I was wondering what cleansing agents were used for human radioactive decontamination? Do they contain more tensioactive agents than normal soaps, or special chelating agents like EDTA to help remove metallic radionuclides? Or perhaps do they contain some abrasive agents (as suggests the term Abrasivstoff in Dekontafix) to help remove the dead layer of skin and along with it any surface contamination? Regards, 141.30.214.203 (talk) 19:15, 5 August 2013 (UTC)

While we didn't go into too much details during my basic training two decades ago, the mantra seemed to be lots of soap and lots of water. Granted, we were mostly taught about chemical decontamination - but no mention was made that nuclear decontamination would be done differently. WegianWarrior (talk) 19:24, 5 August 2013 (UTC)

A quick search turns up [10] which seems to prefer dermabrasives (I actually didn't read much of this, but it looks useful). Wnt (talk) 19:31, 5 August 2013 (UTC)

Thank you for this paper; it looks like many solutions exist depending on the nature of the contaminant: EDTA for ⁹⁹Tc^m, soft abrasives, foams, detergents, etc. Always a pleasure to read the Ref Desk. Regards, 141.30.214.203 (talk) 19:49, 5 August 2013 (UTC)

Deep space travelers beware

What are some of the little known dangers of deep space travel? Are we attempting to solve them now or is that on the back-burner as we focus on inter-planetary travel closer to Earth?— Preceding unsigned comment added by 65.64.111.126 (talk) 19:21, 5 August 2013 (UTC)

Health threat from cosmic rays, IRWolfie- (talk) 19:53, 5 August 2013 (UTC)

Also the deterioration of the human body in low gravity, and the inherent dangers of travelling in an inhospitable vacuum vast distances from any help or hope of rescue or resupply, while completely dependent on high-technology devices for survival. -- The Anome (talk) 19:56, 5 August 2013 (UTC)

See also Effect of spaceflight on the human body and Space medicine. Dominus Vobisdu (talk) 19:58, 5 August 2013 (UTC)

And this is just for interplanetary travel. Deep space, in the sense of interstellar travel, also has the disadvantage that it is currently impossible -- and may well forever be impossible -- to traverse these distances in a human lifetime, or much vaster timescales in the case of intergalactic travel. Even travelling to the Oort Cloud, just a single light-year away in our immediate solar neighborhood, would present a major challenge.

Other than the creation of faster than light travel or teleportation, possible hacks that conform to current physical knowledge which have been suggested to sort this out include generation ships, sleeper ships, "nearly as fast as light" ships which would exploit relativistic time dilation, and the use of von Neumann probes or starwisps to carry and re-create human life from stored information or biological material over the course of thousands, or millions, of years.

Each of these may or may not be possible, and would in each case carry risks of their own. Unless something drastic happens to the human race in the next thousand years, I would expect someone's going to try at least one of these in that time. -- The Anome (talk)

Oh, and also don't forget the psychological effects of long-term isolation of tiny groups of people. -- The Anome (talk) 20:23, 5 August 2013 (UTC)

Ah, yes. The dreaded SPACE MADNESS! "I have had this ice cream bar since I was a child. People always trying to take it from me. Why won't they leave me ALONE!!!!" (Now I've got a hankering for some chocolate covered raisins. Popping out to the store... be right back!) Dominus Vobisdu (talk) 20:32, 5 August 2013 (UTC)

Yep. Space Madness (see here for TVTropes' take on this), a.k.a. the Pain of Space in "Scanners Live in Vain". -- The Anome (talk) 20:52, 5 August 2013 (UTC)

You asked for little-known problems, but most people responded with well-known problems. Here's some that might be a problem from years in space:

1) Nutrition. We may not know about every vitamin and mineral humans need. It's possible there's something vital that we run out of after years without eating real food.

2) Exposure to chemicals. Materials in the ship might give off fumes as they age, which are not filtered out, causing long-term exposure hazards. The same is true of packaging leaching chemicals into the water and food.

3) Instead of isolation, people might have problems being stuck with the same group of people for years. For example, who is having sex with whom could cause some serious tensions.

4) Lack of elderly care facilities. In a multi-generational ship, what do you do with people too old to care for themselves, especially those with dementia ?

5) Too small of a gene pool. In a multi-generational ship, inbreeding will eventually be a problem unless, say, millions of frozen sperm and eggs are shipped with them to be used for reproduction.

6) Freezer burn. If food, sperm, eggs, or even people are frozen, then slight changes in temperature, over time, can cause degradation. StuRat (talk) 21:26, 5 August 2013 (UTC)

Solution for (4) and maybe (1) too: Soylent Green. Clarityfiend (talk) 22:35, 5 August 2013 (UTC)

There may be social problems with a multi-generational ship, too.

In books this is always represented as a total breakdown of civilization and people forgetting that they're on a ship, but it wouldn't have to be that drastic. What if the people who arrive at the destination know full well they're on a ship, but don't want to abandon their home by going down to the planet? (Imagine giving up your home and roughing it on an unknown world because your great-great-great-grandfather agreed to be a pioneer!)

That's just one example. Just about any kind of social breakdown we have here on Earth would be worse if it happened on a generational ship. APL (talk) 08:51, 6 August 2013 (UTC)

Genuine inquiry here: I remember one novel detailing exactly the first scenario you describe above; who else touched upon it? Snow (talk) 09:11, 6 August 2013 (UTC)

Have a skim through this. I can think of a couple offhand that also fit the scenario (Brian Aldiss' Non-Stop, David Lake's Walkers on the Sky, but it's a popular trope, and I'm not at home where I can reflect further and skim my collection (I'm at work and really should be doing some :-) ). {The poster formerly known as 87.81.230.195} 212.95.237.92 (talk) 13:01, 6 August 2013 (UTC)

Larry Niven's short story "The Long Way Home" is a variation of it. Clarityfiend (talk) 00:29, 7 August 2013 (UTC)

A risk I would worry about would be being passed by later, more advanced ships. This has been explored by a number of sci-fi writers, so maybe it's not all that "unknown", but it would sure suck to go through all that trouble only to get to the other planet and have people already there who tell you "Oh yea, We invented the Warp Drive about a week after you left." APL (talk) 08:51, 6 August 2013 (UTC)

Are you sure that's really the worst case scenario? Mightn't it be worse to hear that they invented it last week? Snow (talk) 09:50, 6 August 2013 (UTC)

One of the earlier treatments would be A. E. van Vogt's "Far Centaurus". Clarityfiend (talk) 00:31, 7 August 2013 (UTC)

Dust. No, seriously, very much a problem and one of my favourite examples of how poorly understood the rigors of space-travel are and how inadequately the complexities are treated in popular media and amongst amateur enthusiasts. There's a lot of matter out there and when you're traveling at the kinds of velocities that we would almost certainly be looking at for exploration beyond the solar system, it only takes a very, very small amount of it to annihilate a craft of any realistic proportions upon collision. As to your second question, much thought has been given to how we might tackle the herculean task of interstellar travel, with most of the better-regarded proposals originating from the middle of the last century and having been debated (with regard to which is most feasible) by engineers and scientists from a wide-array of disciplines ever since. However, as regards actual practical efforts (or indeed even efforts to generate general support for such a venture), your assumption is quite correct; the priority in terms of research an expenditure has been overwhelmingly on "local" space travel (and indeed, extremely local), and there's increasingly less support for even these efforts in terms of both public support in leading industrial nations and financial support from the governments of same. <tangent of questionable appropriateness regarding question> You know, every time I've ever heard the query "If you could have a conversation with anyone, living or dead, who would it be?", one of the names that always comes to the top in my mind is Carl Sagan, but at this point I don't think I could look him in the eye, we've all collectively dropped the ball so poorly as regards vision for the future of our species outside of Earth. </tangent> Snow (talk) 09:00, 6 August 2013 (UTC)

If you are a telephone sanitizer, the risks are well know, just not to you. See: [[11]]. Dominus Vobisdu (talk) 09:13, 6 August 2013 (UTC)

Which brings up the next little-known danger: forgetting where your towel is. - ¡Ouch! (^{hurt me} / _{more pain}) 09:36, 7 August 2013 (UTC)

There are also a possibly infinite number of unknown unknowns in Parts Unknown (might help to read the transcript in the description, but only maybe). InedibleHulk (talk) 09:51, August 6, 2013 (UTC)

On a generational ship, would there not also be a risk of a population explosion and therefore using up the resources too soon? 184.147.136.32 (talk) 11:20, 6 August 2013 (UTC)

Don't forget to pack all the microorganisms for your gut flora etc. 20.137.2.50 (talk) 12:57, 6 August 2013 (UTC)

Carl Sagan has pointed out that on the Earth you can find enough Deuterium to move the Earth itself all the way to Saturn's orbit. This can be done to deal with the Sun's gradual increase in brightness. Count Iblis (talk) 13:00, 6 August 2013 (UTC)

I fail to see what that has to do with the question which was asked. IRWolfie- (talk) 23:51, 6 August 2013 (UTC)

The implication (as I read it) was that the Earth itself could be a vessel capable of significant space travel, which affects some of e.g. StuRat's points. ManyQuestionsFewAnswers (talk) 22:04, 7 August 2013 (UTC)

August 6

Which human ancestors invented fire?

In the course of evolutionary history ,Which human ancestors invented fire?

AmRit GhiMire 'Ranjit' (talk) 00:26, 6 August 2013 (UTC)

Probably Homo erectus: see Control of fire by early humans. AndyTheGrump (talk) 00:30, 6 August 2013 (UTC)

And that would be "discovered how to use fire", not "invented". StuRat (talk) 00:39, 6 August 2013 (UTC)

Roasting, stewing, frying, and baking of food with fire could be considered "inventions," since at the time they were new and useful processes, resulting from happy accidents, or from observation and experimentation. Edison (talk) 14:47, 6 August 2013 (UTC)

There is also a distinction between those who used fire that they found in their environment (from forest fires, lightning, volcanoes, whatever) and those who created the means to make it from scratch. The latter would definitely be an "invention"...and I think that this is what we should probably be discussing here. SteveBaker (talk) 16:25, 6 August 2013 (UTC)

Type of solid

What is the term for a covalent network solid that melts by ionising? For example, -ABABA- → AB⁺ + ABA^-. Plasmic Physics (talk) 04:48, 6 August 2013 (UTC)

Generally, covalent network solids (like diamond, silicon, Bakelite, etc.) melt WITHOUT ionizing. Can you give an example of a covalent solid that ionizes as it melts? 24.23.196.85 (talk) 04:56, 6 August 2013 (UTC)

I'm certain that some of the hyperfluorinated metals exhibits this sort of behavior, though I can't seem to find a good example at the moment. Plasmic Physics (talk) 05:03, 6 August 2013 (UTC)

Metal fluorides are ionic solids, not covalent. 24.23.196.85 (talk) 05:42, 6 August 2013 (UTC)

Not generally, that is an over-simplification taught in secondary schools, just like "the conjugate of a weak base, is a strong acid" which is not strictly true either. See aluminium fluoride for an example of a covalent metal fluoride. Plasmic Physics (talk) 05:51, 6 August 2013 (UTC)

Correct, but AlF₃ breaks up into neutral molecules upon melting, not into ions. 24.23.196.85 (talk) 07:44, 6 August 2013 (UTC)

Indeed. However, I did not give it as an example of the substance in question, but only of a non-ionic metal fluoride. Plasmic Physics (talk) 08:36, 6 August 2013 (UTC)

Do any of the transition metal hexafluorides qualify? And ReF₇? Double sharp (talk) 07:45, 7 August 2013 (UTC)

None of the ones list on WP, or rhenium heptafluoride are covalent networks. Plasmic Physics (talk) 08:04, 7 August 2013 (UTC)

Struck out my question above Brain was not retrieving information properly – oops! Double sharp (talk) 08:43, 7 August 2013 (UTC)

Some sort of homoassociation of the parts? DMacks (talk) 05:56, 6 August 2013 (UTC)

Perhaps. Would it be a two step process, whereby the solid breaks into individual monomeric molecules, followed by their homoassociation? Plasmic Physics (talk) 07:05, 6 August 2013 (UTC)

It will be the other way around -- the solid will first break into neutral molecules, which may then self-ionize (but only to a small extent). 24.23.196.85 (talk) 01:41, 7 August 2013 (UTC)

No offense, but I'm certain that that is the same order as what I used. Plasmic Physics (talk) 02:18, 7 August 2013 (UTC)

Is solid oxonium hydroxide stable under pressure, or does it require an applied electric field? I wonder how the density would be different from ice. Plasmic Physics (talk) 07:14, 6 August 2013 (UTC)

Do you mean hydronium hydroxide (also known as dihydrogen monoxide)? If so, it is stable under pressure, but experiences melting point depression and requires supercooling to remain in solid form (it will melt under pressure otherwise). As for the density, it's the same as that of ice -- for obvious reasons! 24.23.196.85 (talk) 01:32, 7 August 2013 (UTC)

No, I'm not using a pseudonym (yes, pseudo-, not syno-) for molecular water. I'm talking about a legitimate salt of composed of discrete ions. Plasmic Physics (talk) 02:18, 7 August 2013 (UTC)

I ask because I know that an equilibrium shift can occur as a consequence of a change in pressure, I also know that this is only applicable to gases, as solids and liquids are incompressible. However, I also know that that last bit is only true for relatively small changes in pressure. Solids and liquids can actually compress under MPa pressures and higher. So, I wondered if MPa or greater pressures, could indeed shift the K_w away from water. Plasmic Physics (talk) 02:27, 7 August 2013 (UTC)

If you're looking for a solid composed entirely of H₃O⁺ and OH^- ions, you won't find it anywhere -- such a solid cannot exist because of energy considerations. Only in a plasma can water be completely ionized! 24.23.196.85 (talk) 04:11, 7 August 2013 (UTC)

I care to know what these energy considerations are - Gibbs, entropy, enthalpy, etc. (FYI I thought that the water decomposes into the elements before becoming a gas plasma.) Plasmic Physics (talk) 04:18, 7 August 2013 (UTC)

American plague

European diseases killed many native americans, why did not american diseases kill the europeans? — Preceding unsigned comment added by 128.214.48.186 (talk) 09:59, 6 August 2013 (UTC)

The Straight Dope tacked this thoroughly. 184.147.136.32 (talk) 11:28, 6 August 2013 (UTC)

This was discussed a couple of weeks ago - see Wikipedia:Reference desk/Archives/Science/2013 July 13#Natives. Clarityfiend (talk) 13:16, 6 August 2013 (UTC)

European diseases may not be the whole story. Count Iblis (talk) 13:49, 6 August 2013 (UTC)

In the Jamestown colony, most of the settlers died their first year. Lack of food was a cause, but they also died from malaria, dysentery and "fevers." The local germs may have been strains they had not encountered back in Britain. The river water may have been nasty, but so were many rivers in England. The local natives were likely not only living in healthier locations, but probably had more natural resistance to the local pathogens. Edison (talk) 14:39, 6 August 2013 (UTC)

Jared Diamond wrote perhaps the definitive work on this exact subject (at least as far as material that is accessible to a wide audience), if you're looking to understand the subject in detail. I recommend the book in any event as a must-read, but here's the long and the short of it - animal domestication. Most infectious diseases pass into the human population for the first time as a result of zoonosis and as Eurasians had been living in close proximity with their domesticated species for many thousands of years by the point of time in question, they had built a healthy collection of diseases, but also had steadily built immunities to the same, limiting their virulence. Native Americans, by comparison, had only a handful of domesticated species (only a very small portion of all species on the planet possess a social nature and other features which make them good candidates for steady and lasting domestication through the methods that are available to a non-technologically advanced people), which were not very well dispersed geographically and as such had not developed nearly as extensive a collection of diseases/immunities. Unfortunately for these peoples, they also lacked the immunities necessary to protect them against the diseases brought with Europeans, and even the pathogens that had relatively mild effects on their Eurasian hosts of this era could in some cases prove deadly to their new American hosts, to say nothing of a disease like small pox, which spread well in advance of the Europeans themselves. Snow (talk) 00:27, 7 August 2013 (UTC)

DNA questions

1. How many codons are there in a base pair?
2. What is the size in megabytes of the human genome?

--Czech is Cyrillized (talk) 23:46, 6 August 2013 (UTC)

One codon equals three base pairs, so there is 1/3 of a codon per base pair. Estimates of the number of base pairs in the human genome vary a bit due to technical reasons, but the most recent value I've seen is around 6.3 billion (in women, with two X chromosomes rather than an X and a Y). Since each base pair contains two bits of information, that yields slightly under 1.6 GB of information. Looie496 (talk) 00:11, 7 August 2013 (UTC)

You can download each chromosome (or those for any of 50 or 60 other species) here. If you grab the "GBK" file, you can unzip it and watch a sea of A's, G's, C's and T's scroll by. I was able to download the full set within a minute or so...and with compression - the whole thing fits comfortably onto a double-sided CD-ROM. You don't even need a DVD, let alone a BluRay disk. It's kinda humbling actually.  :-) SteveBaker (talk) 02:36, 7 August 2013 (UTC)

August 7

Creating a Faraday cage without matter.

Greetings!

I've been studying the concept of Faraday cages and how they contain energies from certain frequencies of the electromagnetic spectrum. I have a question, though, as to how this relates to the properties of visible light apropos human sight. To wit, certain materials—such as the acrylic used to make a woman's swimsuit—remain impermeable to wavelengths longer than 400 nanometers, even when wet. (Otherwise, why would she even wear it?)

I clearly understand the concept as it relates to matter. Nevertheless, I cannot help but wonder: Could one achieve a similar effect with energy, or some other immaterial substance? Namely, is there any method known to science that can create an immaterial, two-dimensional barrier though which Gamma Rays, X-Rays, and Ultra Violet can pass, but not Visible Light (or, for that matter, Infrared, Microwaves, or Radio)?

If so, how would somebody go about doing so, and what would the risks and implications (if any) would such a device entail? Thank you.Pine (talk) 03:47, 7 August 2013 (UTC)

Gravity perhaps? I'm visualizing an array of microsized blackholes in a vacuum. If the curvature of space-time can that be calibrated, it should allow only certain frequencies to pass. As for how to create such a device, I have no answer. Plasmic Physics (talk) 03:58, 7 August 2013 (UTC)

Pine, you seem confused about a couple of things. A faraday cage works by surrounding the protected area with electrical conduction paths (typically either wire mesh or conductive sheets). It works by forcing the electric field within to be such that no voltage can be measured or defined between any point on a object within, and any point on the inside of the shield. For any frequency not zero, subject to some practical limitations, faraday shields cancel out any external magnetic field because such fields will cause a circulating current in the faraday cage, which will set up another magnetic field equal and opposite.

Things that are not transparent, such as swimsuit cloth, are NOT faraday cages. Such things work by attentuation - as the electromagnetic waves (light) penetrate into the material, the interact with the material molecules and are converted to heat. Another example of attenuation is the absorption of light in pure water. The greater the distance into the water, the dimmer the light gets. This has nothing to do with faraday cage operation - pure water does not conduct electricity.

All manner of substances are available that attenuate visible, light, xrays etc. For xrays metals are commonly used. Lead is very effective. In medical xray rooms, good thick concrete walls are used to protect the operators.

What do you mean by "immaterial"? If you mean blocking radiation by use of more radiation, it cannot work, as energy can neither be created nor destroyed - only converted from one form to another - as in the converstion of light or radio waves into heat. Such conversion requires the use of physical matter. Faraday cages are by definition made of matter, which supplies the electrically conductive paths. If you mean "force fields" a la Star Trek, that's just science fiction nonsense.

1.122.160.132 (talk) 04:18, 7 August 2013 (UTC)

I noticed those confusions as well, however, I ignored the bulk of the query and only focused on the question actual at the very end. With regards to 'immaterial', I think that the OP is referring to 'not of matter'. Plasmic Physics (talk) 04:23, 7 August 2013 (UTC)

You're right, I am confused.

Somebody told me that the protective mesh on the door of a microwave oven acts as a Faraday cage allowing visible light (400 nm to 700 nm) to pass through, but not the microwaves themselves (12 cm, or so). i.e. One can see his food being cooked, without himself being cooked in the process.

Yes, by 'immaterial,' I mean something not of matter that would produce a similar effect, but would also block out the visible spectrum.

Does this violate the laws of thermodynamics? Or can it theoretically happen? Pine (talk) 04:35, 7 August 2013 (UTC)

No, nor really. If you take my above gravitational solution into account, you can deflect or absorb the unwanted frequencies. When microsized blackholes evaporate, they release only x-rays and γ-rays. Plasmic Physics (talk) 05:22, 7 August 2013 (UTC)

While one could argue about semantics, it is correct to say that the mesh in the door of a microwave oven acts as a sort of faraday shield in reverse, working with the magnetically doped door seal (positioned within just the right dimensioned metal parts) and the inner metal surface of the oven to keep the microwaves safely inside. (A true faraday shield is an enclosing electrically conductive surface that keeps outside energy getting inside.) The mesh is a good electrical conductor, and the microwaves set up circulating currents in it, causing the microwave enegery impinging on the mesh to be reflected back into the oven. The key to understanding this is that the microwave energy is reflected back in, not converted into heat as it passes through.

To eliminate radiated energy from a given region without the use of matter to do the conversion or reflection is not possible. It would indeed violate an important thermodynamic principle: As I said above, energy can neither be created nor destroyed, but only converted from one form to another - the so called First Law of Thermodynamics.

1.122.207.51 (talk) 06:05, 7 August 2013 (UTC)

Blackholes do not destroy energy, so no it does not. Plasmic Physics (talk) 07:21, 7 August 2013 (UTC)

KDKA's weakened radio signal

When my father was a child, he says KDKA (AM) was audible throughout the Eastern United States at night. The article Greg Brown (broadcaster) agrees it was audible ~175 miles away. Finally, I can confirm it too: as recently as 2004, I picked it up clearly in South Carolina.

But it is no more! Even in different parts of Central Pennsylvania, I can no longer hear it. Not even a small flicker even fades in. And it can't hold a candle up to the easily audible WBZ (AM) and KYW (AM).

What happened? I can't find anything written about a signal reduction. Magog the Ogre (t • c) 04:53, 7 August 2013 (UTC)

All three staions have similar frequency and power output, so in general, coverage should be about the same. What is your location now? Perhaps you are closer to WBZ than you are to KDKA.

In general though, AM distance reception is not what it was in earlier decades. The technology of modern solid state receivers with synthesised or digital tuning results in poor intermodulation performance - this results is weak signals being overiden by what appears to be white noise. Transistor radios made up to the 1980's and tuning with variable capacitors can be a lot better in this regard. Well designed tube radios better again. As well as that, with the increased use of electrical appliances of all kinds, there is more noise to drown weak signals out nowadays.

Local geology can affect reception. AM travels well over water and can be affected by monazite etc. HV powerlines also affect it.

Lastly, an anecdote: I once worked in a similar 50 kW AM "clear channel" station. Over a few years, more and more complaints arrived from distant (300 to 700 km) listeners that our signal was dropping. Eventually we realised that some villain was sneaking in to the unattended transmitter site and bit by bit digging up the copper earth mat and stealing it (a buried mesh of thick copper wire extending over several acres. As well as causing power loss in the ground, it altered the intended direction of radiation.

1.122.207.51 (talk) 06:23, 7 August 2013 (UTC)

Melting and boiling points of the heavy alkali metals

Caesium has melting point 28.44 °C; francium has melting point ~27 °C; ununennium is predicted (see the article's infobox) to have a melting point of 22–24 °C. Why are they so close to each other? (The lighter alkali metals have a more normal trend.) Can anyone offer a (relativistic) explanation?

The boiling points also behave similarly: Cs 671 °C, Fr predicted to be 677 °C(!), Uue predicted to be 655–669 °C.

(A lessened effect seems to occur in group 2; Ubn may at the high extreme have a melting point higher than Ba and Ra (why?), but everything else conforms to normal periodic trends.)

Standard Double sharp disclaimer: Please give sources if possible, because I want to include this into an article (in this case, alkali metal). Double sharp (talk) 07:43, 7 August 2013 (UTC)

Relative motion..

A driver was sent to traffic court for speeding. The evidence against the driver was that a policeman observed the driver's car alongside a second car at a certain moment, and the policeman had already clocked the second car as going faster than the speed limit. The driver argued, "The second car was passing me. I was not speeding." The judge ruled against driver because, in the judge's words, "If two car were side by side, you were both speeding." In this case, how to argue the case in term of physics in the favour of accused driver?

AmRit GhiMire 'Ranjit' (talk) 14:15, 7 August 2013 (UTC)

This sounds like a homework question aimed at testing your understanding of concepts and the articulation thereof, and unwarranted deductions based on flawed interpretation of wording. On the other hand, my experience of the legal system makes this kind of abuse of logic (often deliberate on the part of the practitioners manipulating the outcome, being protected by the shear weightiness of the process of fighting it) pretty standard in the application of "justice". — Quondum 14:24, 7 August 2013 (UTC)

As stated, the judges' decision is clearly wrong. You could be parked, stationary with another car passing you at the instant the policeman observed you. Your statement of the story is that the policeman observed the action "at a certain moment"...ie, over a period of zero elapsed time. Since the measurement of speed requires knowing the distance travelled over time, (even if it's distance travelled relative to another car) - having a zero-time snapshot tells you nothing whatever. If that were literally true then he has no clue how fast you were moving.

But if this is what the claim hinges on then it's a ridiculously fabricated situation - nobody could see an event like this in a literal instant.

In reality - a policeman doesn't get an instant, zero-millisecond snapshot picture of the event. He'd easily be able to tell whether the two cars were or were not going at the same speed from a one or two second glance...and if we trust his testimony then both drivers were indeed speeding and the judge made the right call. If we don't trust the police officer's testimony then all bets are off and we have no way to know whether the accused was speeding or not.

The only other possible inference (and one that this contrived story may be trying to elicit from you) is that the two cars might have been driving around a tight bend in the road - with the accused driver on the inside of the curve and the speeding car on the outside. Both cars could then remain side-by-side with the car on the outside of the curve traversing a longer distance than the one on the inside. Thus the outside car could be exceeding the speed limit while the inside car was not.

But that's one hell of a stretch. In any practical situation, the difference in speed would have to be tiny - probably less than the threshold of error that the police would allow for in using a speed gun. I don't buy it - if that's it, then in any practical situation, the driver is guilty as hell!

SteveBaker (talk) 16:58, 7 August 2013 (UTC)

Why no industrial scale production of human breast milk using transgenetic cows?

More than 25 years ago I thought that by now we would be living in a World where genetic modification of animals would have led to many applications. While you could expect that some predictions would turn out too difficult to realize, (e.g. genetically engineered pigs to grow human organs has faced problems due to retrovirusses), it's rather strange that almost nothing has changed in the food industry. So, what is preventing us to make progress with genetic modification of animals? Count Iblis (talk) 19:42, 7 August 2013 (UTC)

How do you propose getting human milk from a cow? ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:04, 7 August 2013 (UTC)

It's difficult enough convincing the population that tiny modifications in the genes of cereals are safe to eat, so can you imagine the reaction of mothers asked to feed their babies milk from cows with human udders? Research is continuing, but slowly. Dbfirs 21:18, 7 August 2013 (UTC)

Most abundant organic polymers

According to the respective articles, the #1 abundant organic polymer is cellulose and #2 is lignin (which apparently employs 30% of non-fossil organic carbon). Is there a longer list available (say, a top 10), particularly one with estimates for the global mass and the % of non-fossil organic carbon employed? List of most abundant organic polymers would be an interesting article... ManyQuestionsFewAnswers (talk) 22:27, 7 August 2013 (UTC)