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August 11

Influenza

Besides death, can influenza among native people, who lack the immunity, lead to blindless or eye damage?

Google "blindness influenza". I got:

BLINDNESS AS AN IMMEDIATE SEQUELA OF INFLUENZA: RECOVERY

www.ncbi.nlm.nih.gov › Journal List › Br Med J › v.1(3189); Feb 11, 1922by SE Denyer - 1922

BLINDNESS AS AN IMMEDIATE SEQUELA OF INFLUENZA: RECOVERY. Stanley E. Denyer. Full text. Full text is available as a scanned copy of the original print ...

Reversible blindness in optic neuritis associated with influenza ...

www.ncbi.nlm.nih.gov/pubmed/453752by HD Perry - 1979 - Cited by 22 - Related articles

A patient is reported in whom bilateral optic neuritis developed following ...

Bilateral optic nerve atrophy and blindness following swine influenza

www.ncbi.nlm.nih.gov/pubmed/7103325by KL Macoul - 1982 - Cited by 6 - Related articles

μηδείς (talk) 09:32, 11 August 2011 (UTC)

Airport and weather station identfiers

Looking at weather observations and forecasts for the Dodge City, Kansas NWS office, I see Medicine Lodge, Kansas referred to as KP28. I'm used to locations being given their 3 or 4 letter identifier based off of the airport in town (for example, KSLN/SLN for Salina, KS, KSMF/SMF for Sacramento, etc.), but Medicine Lodge's airport appears to be identified as K51. Another example of a city that seem to have an odd identifier like this is Eureka, Nevada (KP68) with an airport identifier of EUE or 05U. As far as I knew, all US ASOS/AWOS stations were either co-located with airports (hence the name "Automated airport weather station") and given that airport's identifier or else located in a climatologically important location (for example [1]) and given a related, still alphabetical identifier (as the example was). This brings up two mysteries to me: 1. Why do Medicine Lodge and Eureka's airports (and a couple others I found that don't have an associated weather station) have identifiers with numbers in them (I thought it was common practice for them to be all letters), and 2. Is there some systematic way of assigning weather station identifiers like P28 and P68 that I haven't heard of, or were they probably randomly assigned? Ks0stm ^(T•C•G) 07:21, 11 August 2011 (UTC)

See location identifier. Three letter ID codes are IATA airport codes, four letter codes are usually ICAO airport codes. All US airports and weather stations are assigned FAA location identifiers consisting of three or four letters and numbers. For large airports, the FAA id is generally chosen to match either the IATA or ICAO designation, but many small airports don't participation in either standard. These smaller airports generally receive FAA codes with numbers in them (though all codes have at least one letter). IATA codes are generally assigned on a first-come, first-serve basis by request (but only to airports above a certain size). Frequently the code is somehow related to the airport's name. ICAO codes are partially systematic: the first letter designates the country or region, the second letter usually corresponds to the first letter of the city / county the airport was located in at the time of the assignment. The last two letters are assigned in some other way I'm unsure of (by request, probably). By convention, ICAO ids may never be reused. I have no idea what process the FAA uses in assigning numbered ids. Dragons flight (talk) 19:03, 11 August 2011 (UTC)

florida homes

do homes in Orlando, fl have insulation — Preceding unsigned comment added by Von1235 (talk • contribs) 10:27, 11 August 2011 (UTC)

I suppose yes. Insulation is not just to insulate you from the cold outside. It's also meaningful to isolated A/Ced rooms from the heat outside. — Preceding unsigned comment added by 88.14.196.229 (talk) 11:48, 11 August 2011 (UTC)

In order to answer your questions completely, please let us know why you assume that there are any homes in the United States that do not have insulation. Building codes have been in place throughout the United States for a very long time and they uniformly require insulation to protect the house from both cold and heat. -- kainaw™ 12:49, 11 August 2011 (UTC)

Certainly houses throughout the U.S. are insulated. Whether or not homes are insulated depends on what the person's home is. People who live in their car, or under a bridge, do not have insulated homes. Pais (talk) 12:57, 11 August 2011 (UTC)

You might not find insulation in houses in Hawaii, but other then that, I would expect most houses in the US to have at least some insulation. At Pais, around here, we call people who live in a car or under a bridge homeless. Oh, and any house with electricity will have electrical insulation. I assumed above you are talking about thermal insulation. Googlemeister (talk) 12:59, 11 August 2011 (UTC)

need some explanation about electrical transformers

there are many types of transformers using in electircal power system ,,,at what bases it is selected is there any site to refer,,,i need application of the transformers which having different type of connections... — Preceding unsigned comment added by Rajivelectrical (talk • contribs) 14:15, 11 August 2011 (UTC)

The article Transformer will help you. Cuddlyable3 (talk) 19:33, 11 August 2011 (UTC)

How is commercial-scale vacuum-sealing done?

Like with spaghetti jars, for instance. There's a slight vacuum there because the first time you twist it open, the metal lid pops up. At the part of the factory where they put the lids on, how do they get that bit of air out right before the lid goes on? Do jarring factories do their lidding in a depressurized section? 20.137.18.50 (talk) 16:20, 11 August 2011 (UTC)

see Canning the can is sealed with its contents hot, vacuum develops as it cools--Digrpat (talk) 16:26, 11 August 2011 (UTC)

ec)Jars typically develop a slight vacuum because they are filled and closed in a hot state. As they cool down, the air volume in the little bubble at the top reduces and some of the water vapor in the air condenses, leading to the development of a small vacuum. You get the same effect if you make preserves yourself and close the jars with the typical rubber seal/glass lid while hot. --Stephan Schulz (talk) 16:37, 11 August 2011 (UTC)

constellations and their relationship to spiral arms.

Are some constellations in other spiral arms and others outside of spiral arms.

I notice that some arms have names such as Norma or Perseus, are the constellations in there or is it that we are using the constellation as a pointer?

Please don't start off your post with "constellations are random .....etc", I am trying to visualize our place alongside them in relation to the arms and its very confusing. :) — Preceding unsigned comment added by 92.30.186.14 (talk) 17:47, 11 August 2011 (UTC)

First, it doesn't make sense to discuss the location of constellations within 3D space, as they are 2D projections without depth. However, regarding the stars that make up the constellations: most stars visible to the unaided eye are within our spiral arm; some visible stars are in other arms and some in interarm space. Thus, I expect that most major constellation stars will have a similar distribution. The Orion–Cygnus Arm is 3500 by 10000 light years in size; only Eta Canis Majoris (3200 ly distant) approaches potentially being located elsewhere on the list of the 90 brightest stars from Earth. As for naming the arms of the Milky Way, they are general references to direction -- one looks through the 2D windowpane of Constellation X to observe some object at arbitrary distance. — Lomn 18:02, 11 August 2011 (UTC)

Also, I don't think all of the points in constellations are single stars. Some may be star clusters, nebulae, or entire galaxies. StuRat (talk) 19:08, 11 August 2011 (UTC)

We're using the names of the constellations to label the spiral arms. If you consider that the constellations were identified and labelled long before the spiral nature of the galaxy was discovered, this should be reasonably obvious. --TammyMoet (talk) 19:17, 11 August 2011 (UTC)

Arms and their direction in relation to our location inside the Milky Way. Note direction of faint lines radiating from where the Sun is.

Constellation Andromeda. Galaxies are the red ellipses, M31 is Andromeda Galaxy, the smaller red ellipse is M33, the Triangulum Galaxy of the constellation Triangulum

Constellations are random...

Kidding. :P But yeah, yes and no.

Like Lomn said, constellations are basically 2d projections of objects in 3d space. Don't think of constellations as a single group of stars close together. They're not. They can be millions of light years away from each other, thus judging 'our place alongside them' by looking at them is basically useless for determining our actual spatial location. In the constellation Andromeda for example. One of its member 'stars', formerly known as n And, is Messier 31 - better known as the Andromeda Galaxy. And obviously the Andromeda Galaxy is not within the spiral arms of this galaxy. Others are Omega Centauri and Triangulum Galaxy.

You're correct though that they are named because they are close to or intersecting a particular constellation. Not in the literal sense that they pass through a constellation, but in the relative sense in that you can see them where you can make out the pattern of a particular constellation. That is actually how we usually convey the location of something in space, because constellations are basically fixed and won't change for thousands of years, if at all (unlike planets). e.g. People telling you that NGC 1333 is in the Perseus Constellation basically mean that you can see NGC 1333 by looking at the general direction of where Perseus is. Also notice how astrologers will say "Mars is in Sagittarius" or something like that, basically meaning that Mars is passing through an area of the imaginary projected sky where Sagittarius is.

However, again this is completely relative to our point of view. Move to a far enough star and this method basically becomes useless. The Perseus arm would not anymore be near the constellation Perseus, for instance. In fact we wouldn't actually see the constellation Perseus at all. It's constituent 'stars' would be scattered all over the sky, depending on how far you went from the Solar system.

I highly recommend you watch the Powers of Ten video.-- Obsidi♠n Soul 19:58, 11 August 2011 (UTC)

While most of this is good information, I need to nitpick a bit. No stars we can resolve with the unaided eye are "millions of light years away", and I don't think any extragalactic objects visible to the naked eye appear star-like (the brightest quasar is more than 6 magnitudes too dim). --Stephan Schulz (talk) 20:43, 11 August 2011 (UTC)

Heh, I meant the Andromeda Galaxy of course (2.54 million light years away), which yes was formerly seen as a star (Andromeda Galaxy#Observation history), as was Omega Centauri (by Ptolemy and Bayer). All of the deep sky objects I've mentioned are visible to the naked eye. I was driving the point of how even if the 'stars' are grouped in a constellation, that doesn't automatically mean they are near each other.

However, note how I placed quotation marks on 'stars' - meaning the constituents of a constellation as we've traditionally perceived them, not actual stars. I debated whether to call them points or something, heh, I have no idea what you'd call the members of a constellation. Elbows of Orion? :P -- Obsidi♠n Soul 21:27, 11 August 2011 (UTC)

This page notes that SN 1987A (a supernova, and therefore a single star) was visible to the naked eye (third magnitude!) at its peak. That was out in the Large Magellanic Cloud, 168,000 light years away (so not quite the "millions" we're hoping for, but still quite a respectable distance). In principle, a bright supernova in a nearby galaxy (Andromeda, Triangulum, etc.) could also be a naked-eye object for a few days; for just a little while the most distant naked-eye star could be "millions" of light years distant.

In a similar vein, the gamma-ray burst GRB 080319B peaked at a visual magnitude of 5.8, and should have been visible to the naked eye for roughly 30 seconds before fading from view. If anyone had been looking in the right place at the right time, they would have seen light from an object 7.5 billion light years away: more than two thousand times the distance to Triangulum, the usual most-distant naked-eye object. For a very brief period, these bursts could give us a view of the most distant stars—at least, assuming that our association of these events with supernovae is correct. TenOfAllTrades(talk) 03:28, 12 August 2011 (UTC)

Badger Diet Question

Does the American Badger ever eat chickens or ducks? Pinguinus (talk) 17:59, 11 August 2011 (UTC)

Badgers will eat pretty much anything they can grab. So, some badger at some time certainly ate a chicken or a duck. However, this is out of the norm. Badgers tend go after burrowing animals. Chickens and ducks don't tend to burrow. -- kainaw™ 19:34, 11 August 2011 (UTC)

Tides

Does the moon's gravity affect the land mass at all, given that it attracts the water on Earth? Aquitania (talk) 19:13, 11 August 2011 (UTC)

Yes. I believe there is a land tide of about 1 meter. Cuddlyable3 (talk) 19:30, 11 August 2011 (UTC)

See Earth tide. Dragons flight (talk) 19:32, 11 August 2011 (UTC)

Also note that tidal forces on the land create heat in the Earth's interior, along with radioactive decay. This keeps the interior molten, which in turn supports the Earth's strong magnetic field, which deflects the solar wind, preventing the atmosphere from being blown away. StuRat (talk) 00:18, 13 August 2011 (UTC)

Black hole and stellar evolution

How is black hole treated as part of stellar evolution? How do scientists arrive at the conclusion? Aquitania (talk) 21:21, 11 August 2011 (UTC)

I would look to the WP article for Stellar Evolution on Black Holes as a start. Essentially, when a star runs out of fuel there is nothing to counteract gravity pulling it together. Depending on the total mass (and whether it goes supernova) gravity overcomes various nuclear forces. For the heaviest star, it forms a black hole. What specifically were you looking for? Black holes are also important in Galaxy Formation. Rosilisk (talk) 21:46, 11 August 2011 (UTC)

To answer in a slightly different way: scientists first realised that black holes ought to exist because the mathematics told them so, including that some stars ought, by the maths, to collapse into black holes at the end of their lives (black holes can also arise by other causes). Then they went looking for evidence of such black holes and eventually found it, confirming the theories. {The poster formerly known as 87.81.230.195} 90.197.66.65 (talk) 23:56, 11 August 2011 (UTC)

It has been hypothesized that material which falls into a black hole emerges on the "other side" as a new Big bang. The idea is neither verifiable nor falsifiable. Cuddlyable3 (talk) 10:30, 12 August 2011 (UTC)

state of a dissolved solid (chemistry)

When a solid dissolves in a liquid, is it considered a change of phase? Is the dissolved solid a liquid? In that case, does the solvant cool down to provide the energy for melting? — Preceding unsigned comment added by 90.28.53.74 (talk) 23:10, 11 August 2011 (UTC)

The solution, considered as a whole, will have the state of the solvent. The solute is usually described as being whatever phase it would be if it weren't dissolved (eg. the salt in salt water is referred to as being a solid and the carbon dioxide is referred to as being a gas), but they don't really have their own phase. They are just part of the solution. I'm not sure about the thermodynamics of dissolving, but it looks like this is the article you need to read: Enthalpy change of solution (I haven't read it myself, so I'm not sure how accessible it is). --Tango (talk) 23:57, 11 August 2011 (UTC)

One thing to remember is that the "three phases" of matter are like the "five senses" or the "four tastes" or other such lists; just as in reality you have many more than five senses, and you can detect more than four tastes, and of course there aren't just the three phases of "solid-liquid-gas". The "three phase" model is used as a heuristic or pedagogical model; designed to give a basic introduction to the lay person or as a means to build upon for students so that they can "add" to the model later in their education and create a more complete picture. In reality, the "three phases" system breaks down pretty easily once you start considering the edge cases, and there are a LOT of edge cases. The problem of solutions is actually pretty easy, but how does one correctly classify colloids like gels and aerosols and things like that? What about glass, which has long presented problems for proper classification? The reality is that matter does not just exist in three phases, and if you can allow your thinking to be expanded beyond that restrictive model, it will allow you to form a more complete picture of how matter is organized. --Jayron32 12:41, 12 August 2011 (UTC)

Thanks for your answers, really helpful! — Preceding unsigned comment added by 90.28.53.74 (talk) 00:56, 13 August 2011 (UTC)

energy savers

are energy savers injurious to health? — Preceding unsigned comment added by 175.110.242.217 (talk) 23:46, 11 August 2011 (UTC)

What sort of 'energy saver' do you have in mind? There are several different things that term might refer to, and we don't have an article on any of them under that title. {The poster formerly known as 87.81.230.195} 90.197.66.65 (talk) 23:59, 11 August 2011 (UTC)

I'm going to take a wild stab in the dark and guess the OP means Compact fluorescent lamp. If that's the case, the health effects have a separate article Fluorescent lamps and health. But the short answer is no, CFLs are not particularly bad for you. Vespine (talk) 00:04, 12 August 2011 (UTC)

Well, my idea of energy saving is curling up in bed with a nice book and a lovely cup of hot chocolate. And that's a lot less potentially injurious than, say, skydiving. Myles325a (talk) 01:41, 12 August 2011 (UTC)

August 12

Pogo stick on trampoline

I was wondering what would happen if you tried to trampoline on a pogo stick. Could it be an Olympic Sport? And what about if you put all four corners of the trampoline on pogo sticks? And put a platform under that and have more pogo sticks under it at the corners? And so on. Could you go into orbit like that? Btw, awaotnmpi, what ever happened to pogo sticks? I've seen push scooters and hula hoops go in and out, and back in, but I've never seen pogo sticks come back. Kangaroos use a natural analog of pogo sticks to bounce around. It's actually very efficient. Do any other animals use pogo stick technology? Myles325a (talk) 01:37, 12 August 2011 (UTC)

Nowadays they're probably considered unsafe. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:05, 12 August 2011 (UTC)

I'm also pretty sure you couldn't get into orbit on trampolines and pogo sticks, lol... Both have weight and friction, i suspect once you got to about 3-5 trampolines and pogo sticks, they would stop "adding" to the effect, i.e., the trampolines/pogo sticks on the bottom wouldn't even leave the ground. Vespine (talk) 02:30, 12 August 2011 (UTC)

Come to think of it, in effect you're creating a big Shock absorber. Vespine (talk) 02:47, 12 August 2011 (UTC)

The effect would depend entirely on if you could get the trampoline and the pogo stick into resonance. If the two were not in resonance, it would probably do nothing interesting. If they were in resonance, you could likely bounce quite high. Until you came down and smashed your skull open, that is. --Jayron32 02:53, 12 August 2011 (UTC)

What a fascinating image. μηδείς (talk) 20:47, 12 August 2011 (UTC)

Pogo sticks are always coming back in, and most children I know in the 7-10 age group have had a go on one. The problem is that, like many toys, they're now perceived as belonging to a younger and younger age group, and pogo sticks are tricky things for the very young. So you can get easier versions designed for younger children, which only increases the perception of them being aimed at younger children. 82.24.248.137 (talk) 09:19, 12 August 2011 (UTC)

A request for consideration of pogo-on-trampoline as an Olympic sport should be addressed to Jacques Rogge, President of the International Olympic Committee corporation, Lausanne, Switzerland, where I am sure he will be intensely interested. Cuddlyable3 (talk) 10:25, 12 August 2011 (UTC)

Pogo sticks come in, and then they go out, and then they come in, and then they come out... Plasmic Physics (talk) 14:06, 12 August 2011 (UTC)

It's been done. Not exciting. Cuddlyable3 (talk) 19:43, 12 August 2011 (UTC)

Hard sandpaper grinding wheel

I'm looking for a sandpaper grinding wheel with a grit close to the hardness of diamond dust, but hopefully far cheaper. Any ideas ? 68.79.97.98 (talk) 04:53, 12 August 2011 (UTC)

I believe Corundum sandpapers are widely available: though not cheap, they are surely cheaper than diamond sandpaper would be. {The poster formerly known as 87.81.230.195} 90.197.66.65 (talk) 05:18, 12 August 2011 (UTC)

Thanks. Anything between that and diamond ? 68.79.97.98 (talk) 05:22, 12 August 2011 (UTC)

Yes, the article Mohs scale of mineral hardness gives some examples, including rhenium diboride, tantalum carbide, titanium diboride, boron nitride etc but I've never seen these made into "sandpaper". What are you trying to sand down? The main problem is usually not in the hardness of the abrasive, but in the glue that holds it to the "sandpaper". An alternative to corundum is Silicon carbide (carborundum), but I'm not sure whether it is any harder than corundum. Dbfirs 06:40, 12 August 2011 (UTC)

I'm trying to sand down rubies (corundum), so need something harder than 9.0 on the Mho's scale. Cubic boron nitride seems to be hard enough, and does appear to be used in grinding wheels. I've not been able to find a place to buy it yet or a price, though. Any help would be much appreciated. 68.79.97.98 (talk) 07:04, 12 August 2011 (UTC)

Drat, I just found the price of cubic boron nitride powder, and it seems to run about 2.5x that of synthetic diamond. 68.79.97.98 (talk) 07:18, 12 August 2011 (UTC)

Surely if you're trying to abrade rubies, it would be far easier to use an appropriately composed grinding wheel or similar solid tool rather than sandpaper? Have you thought of finding a local engineering shop and having an informal chat with someone about what you're trying to achieve? They might be able to suggest a better approach. {The poster formerly known as 87.81.230.195} 90.197.66.65 (talk) 07:30, 12 August 2011 (UTC)

Yes, grinding wheels are more appropriate. I e-mailed 3 people who are contacts for local lapidary clubs (South-Eastern Michigan), but got no responses. Ideally I'd like to find a place where I can rent or borrow the necessary equipment, but I've had no luck. 68.79.97.98 (talk) 07:43, 12 August 2011 (UTC)

This search found a plethora of sellers of diamond grinding wheels. Cuddlyable3 (talk) 09:51, 12 August 2011 (UTC)

This editor has been on the RefDesks a number of times: he is currently trying to find a way to turn the ruby rod from a laser into a set of jewel-cut rubies so he can sell them. Looie496 (talk) 15:08, 12 August 2011 (UTC)

Not quite. I'm trying to grind them into hemispherical cabochons, not cut them into faceted stones, and I intend to give them away, not sell them. (I've concluded I can't make a profit, but these might make a nice "homemade" gift.) 68.79.97.98 (talk) 18:37, 12 August 2011 (UTC)

A difficult endeavor without proper training. Googlemeister (talk) 15:21, 12 August 2011 (UTC)

Yes I noticed that. Since as GM said, it already sounds like a difficult endeavor, I wonder whether the OP has considered using the gemstones which may or may not be diamonds to help cut the rubies? Perhaps manufacturing a home made grinding wheel would be a useful additional task? Nil Einne (talk) 17:36, 12 August 2011 (UTC)

No, that wouldn't work, as diamond dust is needed for grinding, and it wouldn't make much sense to pulverize diamonds to make dust for grinding. Instead of a grinding wheel, I plan to do the reverse, and put the ruby rod in a drill chuck. This should allow me to avoid the flats which are almost inevitable when using a grinding wheel. While this should assure it is circularly symmetrical when viewed from the end, there's still the issue of how to ensure a circular 5 mm radius profile, when viewed from the side. Ideally I'd have a 5 mm radius circular "bowl" coated with fine diamond dust for this finishing work. Can anyone find anything like that ? 68.79.97.98 (talk) 18:41, 12 August 2011 (UTC)

Cabochons are said to be prettier elipsoidal than spherical. Cuddlyable3 (talk) 19:37, 12 August 2011 (UTC)

Perhaps, but they wouldn't fit in the ring where I intend to mount it. 68.79.97.98 (talk) 20:15, 12 August 2011 (UTC)

Are you sure about that? [2] & [3] suggests diamond dust does in fact normally come from pulverised diamonds. Some may arise from the bits and pieces left over that are too small for anything else but I'm guessing traditionally low quality diamonds were indeed pulverised and used to make diamond dust because there wasn't otherwise enough of the left over bits and something had to be done with the lower quality diamonds. Nowadays in the era of cheap synthetics I suspect natural diamonds aren't used much but since the things may or may not even be diamonds I don't know if that applies. Nil Einne (talk) 07:30, 13 August 2011 (UTC)

The "diamonds" are large, faceted stones. Even if simulants, they would still be worth more than the dust which could be generated from them. Furthermore, I have no method available to pulverize them, and, if not real, they might well be softer than ruby, making their dust useless for grinding them. 68.79.97.98 (talk) 12:10, 13 August 2011 (UTC)

Anti-aging

Is it possible to maintain skin like a young person after the age of 50? Will it is possible in the near future to look like a young person even after 60 with the development of anti-aging medicine and life-extension technologies? --HHH000xyz (talk) 07:51, 12 August 2011 (UTC)

Not sure how near it is, but genetic engineering could be used to grow replacement skin from your own stem cells. The problem, though, is replacing your own skin with this skin, which would require surgery, leave scars, etc. Repairing your own skin might be less traumatic, but also less effective, due to cumulative genetic damage. If we could find a way to replace not just a segment of the genetic code in each skin cell, but the entire genome (or else locate and repair the damaged locations in each DNA strand), then that approach might work. StuRat (talk) 08:00, 12 August 2011 (UTC)

Alternatively, is it possible to change community attitudes so that a few natural wrinkles don't bother people? HiLo48 (talk) 08:03, 12 August 2011 (UTC)

If you're talking about sexual attractiveness, I'd say you'll never get more than a minority to consider wrinkles sexy. This is because they are an age marker which makes it apparent that this person is beyond their prime reproductive years, and millions of years of evolution have shaped us to desire people who are able to help us pass on our genes. On the other hand, if you're talking about people from whom we "seek wisdom", wrinkles might indicate they are more likely to have enough experience to provide good advice, with the possible exception of advice about sunbathing (I wonder if old vampires get wrinkles :-) ). StuRat (talk) 17:02, 14 August 2011 (UTC)

It is possible now to skin a young person and freeze the skin. The skin will look the same for hundreds of years. Cuddlyable3 (talk) 09:47, 12 August 2011 (UTC)

Are you male or female? It's harder for females because of the effect of oestrogen on the skin: as production switches off after the menopause, the skin naturally becomes thinner and more translucent. Men don't have such problems.--TammyMoet (talk) 11:32, 12 August 2011 (UTC)

Biologically speaking, we've always known that there is a way to get fresh new skin out of old people: just combine sperm and eggs and let them do their thing... So it's definitely possible to get fresh new skin again, the only question is how to actually do it. But obviously nobody has licked this problem yet. Wnt (talk) 14:48, 12 August 2011 (UTC)

As I understand it, the stiffening of the skin results mainly from the formation of advanced glycation end-products due to glycation of collagen -- in other words, due to cross-linking of the collagen fibers that mainly give skin its mechanical strength. These deterioration end-products are very stable, and there is currently no good way of removing them or preventing them from building up over time -- researchers are working on a variety of things, though. Looie496 (talk) 15:22, 12 August 2011 (UTC)

Circuit training

What does circuit training do and how effective is it as part of a strength/mass building and endurance improvement programme? Thanks. Clover345 (talk) 12:17, 12 August 2011 (UTC)

See Circuit training. --Jayron32 12:32, 12 August 2011 (UTC)

relativity of time

Velocity of light is medium dependent.Then how can relativity in time be proved on its basis.being medium dependent it will travel at different speeds in different media. Suppose there exists a huge mass of water in between path of light being observed by us. If we are unaware of such mass, the change in wavelength observed can be wrong? — Preceding unsigned comment added by Shubahmdiwe (talk • contribs) 15:27, 12 August 2011 (UTC)

If the light passed through a huge mass of water, we would be able to tell by spectrum analysis. thx1138 (talk) 15:33, 12 August 2011 (UTC)

Um, well, if the light passed through a huge mass of water, we would be able to tell by seeing a huge mass of water where the light is coming from. Looie496 (talk) 16:11, 12 August 2011 (UTC)

What do you mean by "relativity in/of time"? What change in wavelength are you talking about? --Tango (talk) 18:39, 12 August 2011 (UTC)

I guess the OP refers to astronomical Redshift as change in wavelength. For a long time the observed speed of light in (what we thought was) a vacuum was explained by an all-pervasive medium called Luminiferous aether, not water. But trying to interpret the Michelson-Morley experiment's negative result persuaded Einstein that the Luminiferous aether idea was unworkable and instead he gave us the Theory of relativity. Cuddlyable3 (talk) 19:08, 12 August 2011 (UTC)

The frequency of light (or any other wave) doesn't change when it passes from one medium to another. The only effect in known physics that can cause a uniform frequency shift is the Doppler effect. The wavelength does change when entering a medium, but it changes back when leaving it. -- BenRG (talk) 17:04, 13 August 2011 (UTC)

Instantaneous travel

Since the Lorentz factor increases without bound as you approach c, could you not theoretically travel anywhere in the observable universe seemingly instantly (from the viewpoint of the traveller) provided you could go fast enough? --Goodbye Galaxy (talk) 18:57, 12 August 2011 (UTC)

No. Cuddlyable3 (talk) 19:09, 12 August 2011 (UTC)

The word 'instantly' is going to give you trouble here. As a traveler approaches the speed of light, their percieved travel time decreases substantially. However, only at the speed of light limit would the trip be perceived as instant. The traveler would perceive the universe to be shrunk in their direction of travel (also by the Lorentz factor I seem to remember). All sorts of complications arise when one is coming back, because their velocity must change. This is discussed in the Twin paradox article. Rosilisk (talk) 19:12, 12 August 2011 (UTC)

Also, Unless you are willing to go past 1g of acceleration to get to c, it is going to take you about 350 days to get up to speed, and the same to get back down to a stop, the majority of that time not seemingly instantaneous. Googlemeister (talk) 19:20, 12 August 2011 (UTC)

Sorry, when I said "seemingly instantly" I meant to the average human. I'd call anything less than a second "seemingly instant," but yes, that should have been more clearly defined. 1 second to get to the Andromeda. --Goodbye Galaxy (talk) 20:11, 12 August 2011 (UTC)

As far as I'm concerned, that's theoretically possible. Getting up to that speed, of course, is completely unfeasible with any imaginable technology. However, speed could be calculated that would allow the traveler to perceive such a fast travel. If you're keen to get an exact number, I could crunch it out. Rosilisk (talk) 20:25, 12 August 2011 (UTC)

To traverse the 2.5 million lightyears to Andromeda in one second, you need to travel at a gamma factor of 7.88*10^13. At that speed, the cosmic background radiation photons that are colliding with the spacecraft will have a typical energy of 100 GeV. If all the energy from these photons is abosorbed by the spacecraft, the total power per unit area is approximately 2*10^22 Watt/m^2. Count Iblis (talk) 00:00, 13 August 2011 (UTC)

Googlemeister's calculation that you can get up to the speed of light in a time of c / 1g = 350-ish days is incorrect. In order to keep from getting squished like a bug, you need the 1g to be proper acceleration, not acceleration as measured in the Earth's (or sun's) reference frame. As your speed relative to the Earth increases, 1g of proper acceleration becomes equivalent to an increasingly smaller acceleration as measured in the Earth's reference frame, such that you can never actually reach a speed of c.

An object moving with constant proper acceleration like that is said to undergo hyperbolic motion. More details about hyperbolic motion is discussed at Rindler coordinates.

A trip which starts out at rest on Earth, accelerates at a constant 1g proper acceleration halfway to the Andromeda galaxy, then decelerates at a constant 1g proper acceleration for the other half of the trip, will take about 28.6 years of proper time. Plug the 2.5 million light-year distance to the Andromeda galaxy into the "Long Relativistic Journeys" calculator here. Red Act (talk) 00:32, 13 August 2011 (UTC)

The math is simple. If you accelerate from rest at a uniform acceleration a, then after a proper time of τ, you'll be at coordinate position (a (cosh aτ − 1)) and coordinate time (a sinh aτ). Solving the first one for τ, to go a distance d takes a proper time of (1/a) cosh⁻¹ (1 + d/a). With factors of c back in, that's (c/a) cosh⁻¹ (1 + dc²/a). More "realistically" you have to accelerate half way and decelerate the other half, in which case it takes (2c/a) cosh⁻¹ (1 + dc²/2a). Coincidentally, c/g, where g is Earth gravity, is very close to one year, so at one gee acceleration it takes (2 years) cosh⁻¹ (1 + d / 2 light years). For large arguments, cosh⁻¹ is very close to ln (natural log), so for large distances that's τ = (2 years) ln (d / 2 light years). Plug d = 2,500,000 light years into that and you get τ = 28 years. There are two problems that make this impossible in practice: lack of fuel and the fact that space isn't empty (see Count Iblis's post re the second one). -- BenRG (talk) 16:52, 13 August 2011 (UTC)

libya

why dont Apache helicopters in libya seem to have the same cameras that they did in iraq that highlight people in white like this http://www.youtube.com/watch?v=G3CnpGwsFL8&feature=related

That's an infrared camera used for night-viewing. The video you saw from Libya was likely taken during the day, when infrared isn't necessary or as useful, since people tend not to be any hotter than the background in Libya during the day. StuRat (talk) 19:13, 12 August 2011 (UTC)

no it was at night — Preceding unsigned comment added by Von1235 (talk • contribs) 19:48, 12 August 2011 (UTC)

It would help if you could link to the video in question. One possibility is that the background was the same temperature as the people, which would make them no longer "glow" on an infrared camera. It being summer in Libya, I'd expect this to be the case. If the background was hotter than the people, they would appear darker (although some cameras might have the ability to invert brightness to make them appear brighter again). StuRat (talk) 20:10, 12 August 2011 (UTC)

heres 1

http://www.telegraph.co.uk/news/worldnews/africaandindianocean/libya/8556413/Night-strikes-by-French-Tigre-helicopters.html — Preceding unsigned comment added by Von1235 (talk • contribs) 13:31, 14 August 2011 (UTC)

OK, that just doesn't seem to have close-up images where you could make out individual people (I think I may have seen some, but they could also just be poles at that resolution). Interestingly, it does show the operator inverting brightness a couple times. StuRat (talk) 16:55, 14 August 2011 (UTC)

Rationale against antistars and antigalaxies

I have read (and yet admittedly not understood) many responses to this question, and yet I don't seem to see a clear reason why we (as in most particle physicists) think that all of the antimatter was completely destroyed shortly after the big bang. The best reasoning I saw is here http://en.wikipedia.org/wiki/Baryon_asymmetry#Regions_of_the_universe_where_antimatter_predominates , however it seems to me easy to speculate that, especially since galaxies may move apart faster than the speed of light, and also that through years (billions of them) of interaction that if there were regions of anti-matter dominated space, or an antimatter galaxy, that the 'average density of intergalactic space' is less here and that matter and antimatter were no longer interacting. This would leave, say, an antimatter galaxy with similar gravitational effect and light production as other galaxies, and perhaps a potential solution to the Baryon Asymmetry problem.

My question is, IF this were the case, and there was an antimatter galaxy with no matter-antimatter cancellation front, would we be able to detect it? Would its emission spectrum be different? Would it cause perhaps some other noticeable difference, or would it be completely indistinguishable from a normal galaxy without a cancellation front? — Preceding unsigned comment added by Ehryk (talk • contribs) 19:19, 12 August 2011 (UTC)

An anti-galaxy would be identical to a normal galaxy. But I don't see how the cancellation front could be avoided. It's also not easy to explain how the matter would have gotten separated from the anti matter since they are normally produced in pairs. The Baryogenesis article talks about the three conditions necessary for the observed asymmetry to form. These conditions were first stated by Andrei Sakharov and are called Sakharov conditions.

1. Baryon number B violation.
2. C-symmetry and CP-symmetry violation.
3. Interactions out of thermal equilibrium.

Dauto (talk) 05:26, 13 August 2011 (UTC)

Not seeking for answer, but explanation

prolate spheroid for explanation by medeis

Why do atoms have a cone (or paraboloid) shape under electron microscope(Do you have any answers but"it's just the way it is"?)?--Irrational number (talk) 19:42, 12 August 2011 (UTC)

I believe it is not the electron microscope, but the Scanning tunneling microscope which can resolve atoms. Perhaps our article about them or some of the sources cited in that article will provide an explanation. Jc3s5h (talk) 19:50, 12 August 2011 (UTC)

that's right, scanning tunneling microscope, that's what I meant...--Irrational number (talk) 19:54, 12 August 2011 (UTC)

I looked in that article but didn't see anything cone shaped. Dauto (talk) 05:12, 13 August 2011 (UTC)

Neighboring atoms form chemical bonds with each other; this can cause the electron clouds to develop a distinctly non-spherical appearence. An STM just probes the overall electronic structure of the entire material; the bonds cause the electron cloud to "spread out" a bit, which could kinda, sorta, maybe be interpreted as a roughly "conical" shape. You don't see a bunch of isolated spheres; but then again you shouldn't. --Jayron32 05:18, 13 August 2011 (UTC)

You mean it could be the effect of the microscope itself?"observer effect"?(and Dauto,there are no cone-shaped in the article, but I suggest a google search,too like [[4]])--Irrational number (talk) 14:40, 13 August 2011 (UTC)

If you read that article you just cited, it itself contains citations of earlier articles; you could likely find the information you seek by following those trails. Or you could read the very same article you cited, since it provides a nice explanation for the cone shapes. --Jayron32 17:17, 13 August 2011 (UTC)

Sorry, but there wasn't any information about what I wanted in the very same article, but I'll read the references... — Preceding unsigned comment added by Irrational number (talk • contribs) 18:30, 13 August 2011 (UTC)

The image is generated by the reflection of particles which are presumed to travel in straight lines. If you were looking down from above on a beachball upon which you were dropping tennisballs, you would only detect tennisballs which bounced back up at you from the upper surface of the beachball. Tennisballs that hit the lower surface would not be able to come back around the "equator" of the beachball, so their lower surfaces would remain obscure. Basically the conical appearance reflects the fact that there is no way, given the size of the observed particles and the probes being used to see them, to view the underside of the atoms. μηδείς (talk) 19:21, 14 August 2011 (UTC)

That's very very far indeed from my reading of Scanning tunneling microscope. Do you know what you're talking about, or are you making it up? --Tagishsimon (talk) 19:25, 14 August 2011 (UTC)

What particularly do you take exception to, my use of analogy? No, the atoms aren't beachball-like spheres with discreet surfaces. But if you had to guess what a beachball in a dark room looked like by dropping tennisballs on it and recording the scatter pattern you would get something that looked like the results you get from this type of observation with the what I would call egg-crate like appearance caused by the relative indelicacy of the probe compared to the observed object. That's not objectionable to you, is it? (You could also imagine trying to guess the shape of a rack of billiard balls in the dark by running a whiffle-ball bat over them.) μηδείς (talk) 21:30, 14 August 2011 (UTC)

In particular: the reflection of particles analogy, and the suggestion that what is measured is only that which is directly beneath the tip of the probe. I read the article to say that changes in current are being measured (which admittedly is a function of electronics) and I imagine that the current changes in relation to the substance happening to be close to the tip rather than merely beneath it. --Tagishsimon (talk) 22:35, 14 August 2011 (UTC)

Okay, I see what you mean. I was trying to leave it simple and visual by saying that you can't distinguish the underside of the atoms with the type of probe being used. To emphasize what you are specifying, you could imagine the image as a graph of the vertical area of the atom under the probe. Imagine an atom as a spherical tomato on a cutting board. You will cut it into a large number of thin slices while holding it upright on the board. Each slice will slide down to the board, so that, viewed from the side, the middle slice will still have the same height, while the slices on each end will drop down to the cutting board. The mass of slices will go from being a sphere to a shape with a flat bottom and a rounded peak of a top. You will now end up with something that looks from the side like the long half of a plastic easter egg shell with its flat surface on the cutting board, half of a prolate spheroid. This will approximate the long upper half of a plastic easter egg. Hence the "cone" shape you see. μηδείς (talk) 00:43, 15 August 2011 (UTC)

small desalinization plant cost

I would like an example of the construction cost of a desalinization plant for a small town (around 1,000 people using ocean water as the input). Location and power consumption of that plant would also be informative. Googlemeister (talk) 20:47, 12 August 2011 (UTC)

I imagine that would greatly depend on the technology used, which in turn would depend on the location. If you are on a vacant coast in a desert area, I would think a rather inexpensive solar-powered desalination system could be used, where water flows in at high tide, is heated by sunlight and evaporates, then cools at night and condenses for collection. If, on the other hand, you are on the coast of Antarctica and need it to work in winter when both sunlight and fuel might be scarce, and you need to pump it from a depth below where ice forms, then you might need to build a nuclear reactor. StuRat (talk) 00:25, 13 August 2011 (UTC)

You might be interested to read about Reverse Osmosis Water Purification Unit and Reverse osmosis plant. Dbfirs 16:49, 13 August 2011 (UTC)

The hourly cost of second-hand smoke?

Is it possible to do a back-of-envelope calculation of the hourly cost of secondhand smoke? It'd be much appreciated. 66.108.223.179 (talk) 23:05, 12 August 2011 (UTC)

Hourly cost to who? Looie496 (talk) 23:29, 12 August 2011 (UTC)

According to a site that offers medical advice, to which you will not see a link here, in Scotland 850 to 950 deaths were the result of the exposure to second hand smoking among non-smokers in 2000. Since the site also sells a homeopathy product it must be very reliable. Cuddlyable3 (talk) 23:55, 12 August 2011 (UTC)

Another joke ? You really need to add a smiley so people won't take you seriously by mistake. StuRat (talk) 00:20, 13 August 2011 (UTC)

Deaths of people older than about 50 lead to savings for society. Count Iblis (talk) 00:35, 13 August 2011 (UTC)

That rather depends upon the manner of death, no? I was under the impression that ridiculous measures taken to extend things by a couple of weeks, days, or hours was a huge burden on the health service. Am I mistaken? Egg Centric 00:44, 13 August 2011 (UTC)

Smokers have had the cost worked out (typically they take more from the health service – which is a different situation in countries with a free-at-the-point-of-use system). This says that people in the US have to spend $10 billion in medical bills and lost work. Some of that money stays in the system, depends what sort of 'cost' you want. That's £6.1 billion/year; 5 to 6 pence (8 to 10 cents) per person per day. Grandiose (me, talk, contribs) 11:09, 13 August 2011 (UTC)

One also has to consider the lower life expectancy, leading to less pension payments. Count Iblis (talk) 16:32, 13 August 2011 (UTC)

I've seen that $10 billion figure, but it didn't occur to me to do such a calculation. Thank you. 66.108.223.179 (talk) 20:12, 13 August 2011 (UTC)

'Av a go at interpreting this liver function test

Medical advice question collapsed
The following discussion has been closed. Please do not modify it.
Strictly hypothetical of course. I really shouldn't have to point out that it's not a request for medical advice for a real case because that would be nuts... but I do anyway, just so we're all on the same page Results: Serum total bilirubin level: 7 umol/L (normal range 1-17) Serum total protein: 72 g/L (normal range 64-83) Serum albumin: 48 g/L (normal range 35-50) Serum globulin: 24 g/L (normal range 18-36) Alk Phos: 94 u/L (normal range 40-129) Serum ALT Level: 96 u/l (normal range 0-40) high Serum gamma GT level: 179 u/L (normal range 5-60) high (Serum electrolytes, glomerular filtration rate, and blood glucose level avaliable on request) Please indicate your level of expertise! Even I'm capable of clicking on each individual article and considering an indicator in isolation - although not necessarily of coming to a conclusion... other than the hypothetical patient really ought to drink less! Egg Centric 00:42, 13 August 2011 (UTC) P.S. I just looked at this and it really does look like I'm soliciting medical advice and/or some kind of homework. I absolutely promise that I am not. I can't think how to rephrase the question, without utterly altering it. And I am not a medical student, nor have I ever been one. I knew some medical students at university but they are doctors now. Not sure what else I can say! Egg Centric 00:49, 13 August 2011 (UTC) P.P.S. There is a very good reason I am using those specific numbers, but it's a long story that's a bit silly. Suffice to say it is certainly not from any real liver test. Egg Centric 00:51, 13 August 2011 (UTC) You can say that you are not requesting medical "avice" all you want, but what you are asking for is an interpretation of a medical test, which requires additional information in order to provide accurately. It would be irresponsible for us to speculate about possible explanations for the values you have given, since it would be impossible for us to know all of the relevant details. In any event, you have already linked to several articles that discuss the possible explanations for different elevated levels. That's about the best you can ask of an encyclopedia; we should not provide a more detailed discussion of this specific scenario. --- Medical geneticist (talk) 10:32, 13 August 2011 (UTC) Just as a matter of basic bandwidth, you're not likely to get a diagnosis out of these numbers - you're looking at two abnormal results and trying to assess the likelihood of a vast number of possible genetic diseases, infections, injuries, toxins, blockages, and tumors. A medical history is doubtless important to make a guess, and any guess might mean more tests to confirm it. But as a matter of personal understanding, which should encourage such a patient to obtain appropriate medical attention, the first thing to understand is that alanine aminotransferase (ALT) is an intracellular protein.[5] So when it turns up in high levels in the blood, it means that somewhere in the liver, cells are getting physically busted open and releasing their contents. The same source indicates that GGT is a confirmatory, nonspecific test for liver troubles. Note that serum bilirubin can give an indication when the bile duct is blocked, and albumin gives some indication of the overall function of the liver when chronic disease is present. Wnt (talk) 12:09, 13 August 2011 (UTC)

August 13

'Av a go at interpreting this liver function test

Medical advice question collapsed
The following discussion has been closed. Please do not modify it.
Strictly hypothetical of course. I really shouldn't have to point out that it's not a request for medical advice for a real case because that would be nuts... but I do anyway, just so we're all on the same page Results: Serum total bilirubin level: 7 umol/L (normal range 1-17) Serum total protein: 72 g/L (normal range 64-83) Serum albumin: 48 g/L (normal range 35-50) Serum globulin: 24 g/L (normal range 18-36) Alk Phos: 94 u/L (normal range 40-129) Serum ALT Level: 96 u/l (normal range 0-40) high Serum gamma GT level: 179 u/L (normal range 5-60) high (Serum electrolytes, glomerular filtration rate, and blood glucose level avaliable on request) Please indicate your level of expertise! Even I'm capable of clicking on each individual article and considering an indicator in isolation - although not necessarily of coming to a conclusion... other than the hypothetical patient really ought to drink less! Egg Centric 00:42, 13 August 2011 (UTC) P.S. I just looked at this and it really does look like I'm soliciting medical advice and/or some kind of homework. I absolutely promise that I am not. I can't think how to rephrase the question, without utterly altering it. And I am not a medical student, nor have I ever been one. I knew some medical students at university but they are doctors now. Not sure what else I can say! Egg Centric 00:49, 13 August 2011 (UTC) P.P.S. There is a very good reason I am using those specific numbers, but it's a long story that's a bit silly. Suffice to say it is certainly not from any real liver test. Egg Centric 00:51, 13 August 2011 (UTC) You can say that you are not requesting medical "avice" all you want, but what you are asking for is an interpretation of a medical test, which requires additional information in order to provide accurately. It would be irresponsible for us to speculate about possible explanations for the values you have given, since it would be impossible for us to know all of the relevant details. In any event, you have already linked to several articles that discuss the possible explanations for different elevated levels. That's about the best you can ask of an encyclopedia; we should not provide a more detailed discussion of this specific scenario. --- Medical geneticist (talk) 10:32, 13 August 2011 (UTC) Just as a matter of basic bandwidth, you're not likely to get a diagnosis out of these numbers - you're looking at two abnormal results and trying to assess the likelihood of a vast number of possible genetic diseases, infections, injuries, toxins, blockages, and tumors. A medical history is doubtless important to make a guess, and any guess might mean more tests to confirm it. But as a matter of personal understanding, which should encourage such a patient to obtain appropriate medical attention, the first thing to understand is that alanine aminotransferase (ALT) is an intracellular protein.[6] So when it turns up in high levels in the blood, it means that somewhere in the liver, cells are getting physically busted open and releasing their contents. The same source indicates that GGT is a confirmatory, nonspecific test for liver troubles. Note that serum bilirubin can give an indication when the bile duct is blocked, and albumin gives some indication of the overall function of the liver when chronic disease is present. Wnt (talk) 12:09, 13 August 2011 (UTC)

Space shooting

Would it be possible to fire a gun in space ? — Preceding unsigned comment added by 124.253.128.87 (talk) 06:38, 13 August 2011 (UTC)

Yes. Why not?--Shantavira|^{feed me} 07:09, 13 August 2011 (UTC)

But note that using it in a weightless environment would propel you backward, and, if you didn't have the barrel aligned with your center of gravity, would also impart a spin to your body. This would make a second shot difficult. StuRat (talk) 07:17, 13 August 2011 (UTC)

I thought firing a gun required something to ignite. Would that be possible in the absence of oxygen? Pais (talk) 07:40, 13 August 2011 (UTC)

Yes, Pais, that's what I meant... — Preceding unsigned comment added by 124.253.128.87 (talk) 07:47, 13 August 2011 (UTC)

I don't believe the ignition of gunpowder requires any additional oxygen beyond that present in the gunpowder already. See Gunpowder#Combustion_characteristics. StuRat (talk) 08:01, 13 August 2011 (UTC)

Well, there is this - Soviet laser pistol - though I seriously doubt it ever existed. (I know next to nothing about firearms, but, well, you don't have to be a theoretical Physicist to know that time is not cubic.--Shirt58 (talk) 08:08, 13 August 2011 (UTC)

The Soviets did test a gun on a space station - after the cosmonauts had safely left it, though. See Almaz#Defense measures. 75.41.110.200 (talk) 21:01, 13 August 2011 (UTC)

Potatos strapped to the wrist

This is going to sound really strange, but can you break your wrist by tying potatos to it for 8-12 hours then hitting it? I'm not looking to try it! Chemistrydegreebutnojob (talk) 07:33, 13 August 2011 (UTC)

I would think you could break your wrist by hitting it even without first tying potatoes to it, if you hit it hard enough. Pais (talk) 07:41, 13 August 2011 (UTC)

The stories I've read and heard about involve hitting with a spoon after sleeping with potato slices tied to the wrist. I just wanted to know if there was any scientific basis for this and whether it was likely to workChemistrydegreebutnojob (talk) 11:45, 13 August 2011 (UTC)

In that case, no. Plasmic Physics (talk) 11:53, 13 August 2011 (UTC)

I'd say that depends on the spoon. I've seen wooden spoons that make a pretty good Hanbō (e.g. [7]), and they can break a wrist easily. It's unlikely that the potatoes have any effect on this, though. --Stephan Schulz (talk) 12:57, 13 August 2011 (UTC)

Potato slices tied to wrist? Hitting with spoons? If there was a polite version of WTF, I feel this would be a good occasion to use it... 86.179.3.8 (talk) 13:38, 13 August 2011 (UTC)

Potatoes have nothing to do with how much force it takes to break the wrist. Plasmic Physics (talk) 14:35, 13 August 2011 (UTC)

They have as much to do with it, as the stars has to do with predicting a good investment. Plasmic Physics (talk) 14:37, 13 August 2011 (UTC)

Though if enough people thought that the stars could predict a good investment, it might create a self-fulfilling prophecy and work, at least for a while. Googlemeister (talk) 14:33, 15 August 2011 (UTC)

I cannot help but wonder where one might find stories about sleeping with potato slices tied to the wrist. Wanderer57 (talk) 14:47, 14 August 2011 (UTC)

Oddly enough, a simple Google search potato wrist break spoon gets many hits of people asking about this (or could it be the same person trying to start an urban legend?). I haven't found any claim that it is true. PrimeHunter (talk) 21:32, 14 August 2011 (UTC)

That seems very plausible. One or more bored students spamming lots of message boards trying to start some urban legend. 86.160.84.240 (talk) 11:56, 15 August 2011 (UTC)

• I feel like the following points need to be made:

• Deliberately breaking your own wrist is an extraordinarily stupid idea.
• Whether you strap a potato to it first or not.

Beeblebrox (talk) 21:39, 14 August 2011 (UTC)

escape velocity

What is the escape velocity for a galaxy? --DeeperQA (talk) 10:53, 13 August 2011 (UTC)

How big is the galaxy, what is its mass? Plasmic Physics (talk) 11:50, 13 August 2011 (UTC)

And escaping from what? Nyttend (talk) 11:52, 13 August 2011 (UTC)

It is the escape velocity from the most dense planet, unless there is a Black hole that you can't escape. Cuddlyable3 (talk) 12:20, 13 August 2011 (UTC)

No, the galaxy has a significant pull, and indeed it is hard to escape: according to escape velocity it would take 525 m/s from the Earth to escape the Milky Way, nearly 50 times what it takes to escape the Earth's gravity (though of course there are stars to stop and refuel at in the Milky Way's case). Wnt (talk) 12:30, 13 August 2011 (UTC)

For the Milky Way galaxy, in this youtube clip, physicist John C. Mather estimates ~1000 km/s. This is a lot more than the 525 km/s that the escape velocity article says, citing an article written in 1987. The reason for the discrepancy is, as Mather says, we're not very sure about how massive the Milky Way is, and estimates have steadily increased over the last few decades. This touches upon this 2010 question, which also depends on galactic mass estimates and discusses Wikipedia articles citing old papers. -- Finlay McWalter ☻ Talk 12:50, 13 August 2011 (UTC)

A few thoughts:

1) Unlike a planet or star, a galaxy really can't be treated as a point mass, meaning the location and direction would significantly impact the escape velocity.

2) We probably need to define "escape", too. Since the times involved are very long, would it count as having escaped if the universe expands more quickly than the rocket falls back towards the galaxy ?

3) Does finding the Lagrange point between the Milky Way and one of it's small satellite galaxies count as having "escaped" ? How about between the Milky Way and Andromeda ? StuRat (talk) 17:45, 13 August 2011 (UTC)

(1) is true, but becomes irrelevant once we've left the galaxy, so it might make the most sense to talk about the escape velocity of a galaxy at its edge (just as we usually talk about the escape velocity of a planet at its surface). (2) isn't really true - cosmological effects are pretty insignificant at the galactic level. There isn't really any expansion within, say, the Local Group (it's gravitationally bound). If you want to talk about the escape velocity of a galactic supercluster, then you may need to take it into account, but even then it will be minor. As for (3), I suppose galaxies will have L-points with each other, but just reaching an L-point doesn't do anything. You need to enter the right orbit at that point. It would take a hell of a lot of thrust to get from a near-escape trajectory to a periodic orbit around a galaxy. --Tango (talk) 18:45, 13 August 2011 (UTC)

How does dark matter affect an objects velocity needed to "escape" from a galaxy? Isn't it simplistic to just look at the gravitational attraction of the masses of ordinary matter on a galaxy? Isn't there something peculiar about the rotational velocity of the outer spirals of galaxies? Edison (talk) 19:52, 13 August 2011 (UTC)

It increases it because it contributes to the total mass of the galaxy. The thing is, we can calculate a galaxy's mass by looking at the orbital velocities of stars in it, as well as by working out how much mass just the matter we can see ought to have, and as you say the higher-than expected velocities observed demonstrate that dark (i.e. unseen) matter (which may be exotic or may be, at least in part, ordinary matter we can't see merely because it's cold and dark) is present (which is how it was detected in the first place). {The poster formerly known as 87.81.230.195} 90.201.110.213 (talk) 20:59, 13 August 2011 (UTC)

Bear in mind that a spherical shell of mass around you exerts no gravity. Someone ten miles from the center of the Earth, if possible, would feel the gravity of a 10-mile iron ball. Unlike the normal matter of the galaxy, the dark matter is at least roughly spherical, and makes up most of the mass. So however far you go out from the center, things feel the gravity of a mass that increases with the radius, so they're always orbiting at roughly the same rate. But this means that it's not really known quite how far you have to go out before the total mass you feel pulling you back in stops increasing - which in turn determines the escape velocity at that point. Wnt (talk) 00:49, 14 August 2011 (UTC)

Measuring atomic mass

How is atomic mass measured? Mass–energy equivalence tells me that nuclear binding energy is found by measuring atomic mass and subtracting the AMUs for the protons and neutrons, Atomic mass tells me that it's done with mass spectrometry, and Mass spectrometry tells me a lot of things about the process, but as far as I can see, it doesn't tell me how it works. Could I have just a simple layman's explanation please? I'd like to improve the atomic mass article by the addition of such an explanation to its "Measurement of atomic masses" section. Nyttend (talk) 12:06, 13 August 2011 (UTC)

May be you should read the article again. Everything you need to know is in there. Read in particular the section Mass spectrometry#Mass selection. Let us know if don't understand anything. Dauto (talk) 12:25, 13 August 2011 (UTC)

Barycenter

In a 2-body system, does the barycenter coincide with the L1 Lagrange point if, and only if, the masses of the two bodies are equal, or do other variables also figure in ? StuRat (talk) 17:59, 13 August 2011 (UTC)

The "if" is definitely true. If the two bodies are of equal mass then the barycentre and L1 point will be at the equidistant point on a line joining them, by symmetry (they are both always on the line joining them and, since there is no way to distinguish the bodies you can't work out which would be closer, so they must be the same distance away). The "only if", I'm not so sure about, but I think it will be true. The barycentre is always closer to the heavier object (it's distance to each object in inverse proportion to their masses), while I think L1 is always closer than the lighter object. --Tango (talk) 18:55, 13 August 2011 (UTC)

What Tango said is correct. The two points only coincide if the two objects have identical masses

... reply above by Dauto at 00:27, August 14, 2011

The formula for the L1 point is not simple. If $f$ is the fraction of the separation of the masses to L1 from the larger mass, and $b$ is the fraction to the barycentre, then $b={\frac {m}{(m+1)}}$ where $m$ is the ratio of the masses (small/large), and $f$ is given by $(1-f)^{2}-mf^{2}-f^{2}(1-f^{2})[(1+m)f-m]=0$ (assuming circular orbit).

I don't think there is an algebraic proof, but graphing the functions should show that $f=b$ is only possible when they are both a half. There might be a more elegant proof, but I don't know it. Dbfirs 08:25, 14 August 2011 (UTC)

It can be shown algebraically, assuming your equations above are correct (which I didn't check). Since we require$f=b$, we substitute $b={\frac {m}{m+1}}$ for $f$ in $(1-f)^{2}-mf^{2}-f^{2}(1-f^{2})[(1+m)f-m]=0$ to give, after a little algebraic simplification, ${\frac {1-m^{3}}{(m+1)^{2}}}=0$. That equation can only hold when the numerator $1-m^{3}=0$, the only real solution of which is $m=1$. (The complex solutions $m=-{\frac {1}{2}}\pm i{\frac {\sqrt {3}}{2}}$ are of course nonphysical.) Red Act (talk) 17:22, 14 August 2011 (UTC)

Thanks, I missed that -- in fact I was very lazy and didn't check because I knew there was no algebraic solution to the quintic in "f" for the L1 point. Apologies for the faulty assumption. Dbfirs 21:49, 14 August 2011 (UTC)

Thanks for the replies. So that was a "yes", as "In a 2-body system, the barycenter coincides with the L1 Lagrange point if, and only if, the masses of the two bodies are equal", right ? StuRat (talk) 21:39, 16 August 2011 (UTC)

Compound movements workout

Are compound movements - chest press, squat, dead lift etc the ony way to build muscle mass? Are machines and other free weight isolation exercises not as effective? Clover345 (talk) 18:01, 13 August 2011 (UTC)

Walking, running, jumping and climbing have done it for most of human history, long before the invention of exercise machines that people can sell you for a profit. HiLo48 (talk) 21:35, 13 August 2011 (UTC)

Isolation is useful if you want to develop one muscles group, and not others. Why would you want to do this ? Perhaps if one muscle group seems to need more work than the rest. Otherwise, I'd think good overall exercise, such as swimming, would be in order. StuRat (talk) 23:39, 13 August 2011 (UTC)

Thanks Stu. Yes, I forgot swimming. HiLo48 (talk) 23:52, 13 August 2011 (UTC)

predicting toppling

hi, i want to know how can we determine at what angle a body will topple. for example, if i'm leaning back on a chair, at what angle will i topple? — Preceding unsigned comment added by 117.192.193.90 (talk) 18:29, 13 August 2011 (UTC)

An object will topple when its centre of gravity is no longer over its base. So, for you leaning backwards on a chair, that will be when the centre of gravity of you and the chair is behind the back legs of the chair. --Tango (talk) 18:58, 13 August 2011 (UTC)

thank you tango, but what do you exactly mean by 'over its base'. also is it possible to define it mathematically, in terms of toppling moments and restoring moments? what forces will constitute each of these moments? thank you — Preceding unsigned comment added by 117.192.193.90 (talk) 19:07, 13 August 2011 (UTC)

By "base", I just mean the bit of it that should be on the ground. For a chair, that's the area between the four legs. Once your centre of gravity is not over the area between the legs, you will topple. You can view it mathematically by considering the force of gravity acting vertically down from the centre of gravity and the reactant force from the ground pushing up vertically from the points that are in contact with the ground. If those forces aren't in line with each other, there will be a moment. If gravity acts through the base (ie. the centre of gravity is over the base), then the moment will be to tilt the object so the the base touches the ground. If gravity doesn't act through the base, the moment will cause the object to topple. (This is much easier to explain standing in front of a blackboard! Sorry if I'm not making it clear.) --Tango (talk) 21:36, 13 August 2011 (UTC)

Yeah, as long as the base is flat (or concave) and the edge of the base is rigid you can just consider the outline from directly above--if the center of gravity is within that outline it will be relatively stable. The higher the center of gravity is and the close it is to an edge the less stable it will be in the face of wind or someone bumping it. If you define the parameters and ask at the math desk someone will likely give you some relevant formulae. μηδείς (talk) 22:15, 13 August 2011 (UTC)

More generally, a stationary rigid object resting on a horizontal plane and subject to no forces except for a vertical gravitational force will be unstable if the orthographic projection of the object's center of gravity onto the horizontal plane lies outside of the convex hull of all parts of the object which touch the plane. Red Act (talk) 02:13, 14 August 2011 (UTC)

Sounds definitive. Like that formulation "convex hull"--very efficient way of expressing a complex abstraction. μηδείς (talk) 02:48, 14 August 2011 (UTC)

... and the toppling or restoring moment is just the weight multiplied by the horizontal distance between its line of action (a line vertically down from the centre of gravity) and the pivot (the line joining the points of contact of the two chair legs still on the floor). This will be toppling if outside the "complex hull" (wrong side of the pivot) or restoring if inside (right side of the pivot). If your feet are on the ground, or you are holding on to something, then there are other forces contributing to the moment. Dbfirs 06:49, 14 August 2011 (UTC)

thank you guys, you guys are simply superb — Preceding unsigned comment added by 117.192.202.79 (talk) 18:20, 14 August 2011 (UTC)

Stomach anatomy

Hello. What part of the stomach lies approximately 1 inch above the belly button? Thanks. Leptictidium (mt) 20:13, 13 August 2011 (UTC)

Lots. Depending if you mean inside or outside or how picky you are at exactly how far the inch is. See Abdomen.-- Obsidi♠n Soul 20:52, 13 August 2011 (UTC)

Note thay the umbilicus is a fixed part of the abdominal wall, while the contents of the abdominal cavity are not fixed with respect to the abdominal wall, and do move about within the individual, not to mention individual variations. That said, compare the figures that I've copied. I would place the imbilicus at an inch ore two below the plane labeled d in the image to the left. This would imply that coils of small intestine are a good candidate, or possibly the Transverse colon. The great omentum may also extend down to this reagion, and be the closest anatomical structure within the abdominal cavity to your point of interest . --95.34.139.175 (talk) 21:13, 13 August 2011 (UTC)

Abdominial cavity

Male torso

200 proof alcohol sale and consumption

While on the last portion of my annual Israel summer dig/trip, I purchased the infamous Perfect 95 (Israeli Everclear) with the intention of using it as lighter fluid (My dad actually took a sip of it and was not well afterward). This plan worked, as it always does, to great affect, and got me we wondering. I read that 95% alcohol is the highest ethanol content one can purchase in the realm of simple-distilled alcohol. There are other methods of course that would allow one to get pure ethanol, but does anyone use these methods to make a commercially available beverage? I guess my question is, is there any publicly available pure ethanol spirit sold anywhere in the world? I am a teetotaller btw, so I have no intention of drinking it, as a result any jokes will most likely fall flat. Sir William Matthew Flinders Petrie | Say Shalom! 20:16, 13 August 2011 (UTC)

You can buy absolute ethanol for your chemistry lab. In the US it has a liquor tax stamp, because obviously it can't be denatured. Whether a supply house would sell it to an individual I don't know.

Despite the stamp, it could be risky to use it for beverage purposes, because benzene is used as part of the purification process, and trace amounts could remain. I have no reference for that; just going off what I've heard. --Trovatore (talk) 20:20, 13 August 2011 (UTC)

I don't believe there is any beverage that is 100% alcohol. It would taste terrible and be very dangerous. Everclear really isn't safe either, it's pretty much made for college kids to make horrible punch drinks in garbage cans and watermelons. I've never met anyone over the age of 25 who would even consider purchasing it. Beeblebrox (talk) 20:22, 13 August 2011 (UTC)

190 proof alcohol has other uses. For example some people pour it over cherries and let them sit for some weeks or so to preserve them. I make no claims as to how safe this is. --Trovatore (talk) 20:26, 13 August 2011 (UTC)

The US gov is very paranoid about people getting alcohol through any means they can't tax you a great deal on. If it's denatured, they might if you can produce good credentials I'll bet. Ah well, I'm 21 so no worries then. :p Sounds about right. I only use it for lighter fluid (and hell is it effective). Though as you say it is very dangerous, if you pour for too long on an open flame, said flame will race up into the bottle as my digmates found out last year (Then again, someone lost a finger on that dig as well after he tried to catch a low-thrown mini-boulder on a ledge, so some of our newbies weren't the brightest bulbs, especially the ones who actually drank that crap). What about using it as a disinfectant? Sir William Matthew Flinders Petrie | Say Shalom! 20:39, 13 August 2011 (UTC)

Note that 95% ethanol forms a positive azeotrope where distillation does nothing to change the ratio of ethanol to water in the vapor. For commercial scientific use 95% ethanol is substantially cheaper than 100%. Also I think there's that nagging question of what chemical process is used to remove the last 5% of water from the ethanol and whether there is a risk of contamination with something unpleasant. But the main point is nobody is going to a lot more for 5% more alcohol unless they're doing chemistry. Wnt (talk) 00:43, 14 August 2011 (UTC)

See also Ethanol purification. --Ouro (blah blah) 14:16, 14 August 2011 (UTC)

Cute little Israeli Rodent which I cannot identify

I meant to post my above question last night, so apologies for the two-for. Anyway, this little fella has been walking around the hotel portion of our kibbutz. My dad and I have been wondering what he is. Clearly a rodent, and appears to be blind. He is out during the day and the night, but seems to favour the night. Doesn't seem outwardly vicious at all and appears to be either a herbivore or insectivore. Anyone want to help me identify this fellow? Sir William Matthew Flinders Petrie | Say Shalom! 20:18, 13 August 2011 (UTC)

It's a hedgehog, not a rodent. Looks really bad off--look at the sores on the legs. How awful. See here. μηδείς (talk) 20:23, 13 August 2011 (UTC)

Ah, see that's what I told my dad first, but he thought it was another animal. Poor little guy, I wonder what did that. Thanks! I will get him some watermelon tomorrow. Sir William Matthew Flinders Petrie | Say Shalom! 20:40, 13 August 2011 (UTC)

If it's native to Israel (and not a transplant from somewhere else), it's likely to be a Southern White-breasted Hedgehog or a Desert Hedgehog. The Long-eared Hedgehog is also native to the area, but the critter in your picture doesn't look like the ones in the article. Pais (talk) 20:44, 13 August 2011 (UTC)

Desert is unlikely as the map shows the range only being in the Judean Desert and the Negev. I am in the Western Galilee, Kibbutz Lohamei HaGeta'ot to be specific. I doubt the little fella could have made it up here what with all the cars and roads that would squish him (of course a kibbutznik could have brought him up here from one of those areas). Sir William Matthew Flinders Petrie | Say Shalom! 20:52, 13 August 2011 (UTC)

Watermelon is almost nutrient free except for water (which I am sure he'll want) and not too much sugar per volume. I'd suggest some little scraps of meat, some peanut butter. You really should check on line since I am just guessing--there are tons of fan sites--but he's an omnivorous insectivore, so don't starve him on a rodent diet. You might take him to a vet who might suggest euthanizing him but will have the best advice, obviously. μηδείς (talk) 22:10, 13 August 2011 (UTC)

A pet store or fishing shop will probably have crickets, or better, earthworms or mealy worms. Some egg might work as well. Keep in mind they do transmit diseases and I am curious if rabies might be a risk. μηδείς (talk) 22:19, 13 August 2011 (UTC)

And hedgehogs are not really rodents. Googlemeister (talk) 18:44, 15 August 2011 (UTC)

Rabies in hedgehogs is extremely rare (only one case I've ever found - but it was a similar hedgehog from Budapest). Salmonella is the primary concern for human contact with hedgehogs. There are many cases of that. Also, hedgehogs anoint themselves with various things they find as they travel. So, it isn't uncommon for a wild hedgehog to be covered in various toxins. -- kainaw™ 18:50, 15 August 2011 (UTC)

Does it exist a Pyrenean Isthmus?

I am interested in doing some work which includes The Pyrenees, but not only the mountain system itself, but its surroundings too (valleys, rivers, oceans, territories, etc.). It has always appeared to me that The Pyrenees and its surroundings are a large isthmus who separates the Iberian Peninsula from the Western European continent, but when i look for references i can not find any.

I tried the link for isthmus in Wikipedia, but besides saying that isthmus is "....a narrow strip of land connecting two larger land areas usually with waterforms on either side", it never mentions or considers a Pyrenean Isthmus, as such. I believe it is an important subject to include such European territory as an isthmus due to its significant value in regard to its demography and several other factors.

I know that today, such isthmus is shared by two countries (Spain and France), but also i am aware that in the past, was shared by other different countries or their equivalent, without diminishing its importance.

I guess the clue here is on the term "narrow strip of land"....how narrow has to be a strip of land to be considered an isthmus?

I shall be looking forward for some help in this respect. Thanks in advance. — Preceding unsigned comment added by 86.196.220.164 (talk) 21:13, 13 August 2011 (UTC)

I doubt there's a hard limit on how big an isthmus can be before it's no longer an isthmus, but whether or not the Pyrenees can be labeled an isthmus shouldn't impact a discussion of the landform's importance to Western Europe. Note also that the Pyrenees are shared amongst three present-day nations: France, Spain, and Andorra. — Lomn 21:32, 13 August 2011 (UTC)

You get 59 hits for "Pyrenean Isthmus" including a blog with that name asserting an identity for the people living between the Ebro and the Garonne. Is that your blog? You get 55 hits for "Iberian Isthmus" which seems to be used in a scientific rather than cultural manner. μηδείς (talk) 22:02, 13 August 2011 (UTC)

Fernand Braudel writes, in The Mediterranean and the Mediterranean World in the Age of Philip II (volume 1), of four great European isthmuses: "It [Europe] is intersected by a series of north-south routes, natural isthmuses that are still decisive influences on exchanges today: the Russian isthmus, the Polish isthmus, the German isthmus, and the French isthmus." He describes each at length. The Russian isthmus being from the Baltic to the Black and Caspian Seas, the Polish from the Baltic to the Balkans and the Bosphorus, the German from the Baltic & North Seas to the Adriatic and Tyrrhenian Seas, and the French from "Rouen to Marseilles". He's clearly picking these specific "isthmuses" out for being important routes of trade, migration, etc, more than just for being "narrow strips of land". He also mentions west-east "routes" in the Iberian peninsula, including "Barcelona to Navarre", which is close to the notion of an isthmus at the Pyrenees. Braudel's focus on linking trade routes and isthmuses doesn't work for the Pyrenees themselves. Still, it is an example of the term "isthmus" being used with a very broad meaning. Pfly (talk) 05:56, 15 August 2011 (UTC)

Thanks you for your respective answers. Absolutely true! How could i have forgotten Andorra, being that i live there part of the year....and probably is due to the habit of considering this small country as one of those that form part of the Pyrenean Isthmus as a whole, not partially. On the other hand, among those 59 hits that one of you mention above, i have come across with a few new ones, with different opinions about the same subject which i find quite interesting; and yes, the blog mentioned is mine. And finally, but not least, it would be interesting to dicuss if the so called "French isthmus" (Rouen-Marseille) could be considered as such, even considering it as a "linking trade route", or even more, considering it as a larger trade route than the strip of land existent between the Atlantic and the Mediterranean (Pyrenean isthmus). I am not trying to push the concept that a Pyrenean isthmus should be considered as such in Wikipedia, but like me, there could be other people who would not know to consider it as such "officially" by the writers and authors of Wikipedia, or not. I believe, this matter should be left well defined in the article about isthmus, by you all and me, but i do not know the procedure to follow to make it happen. Thanks for your attention and effort.

Origin of viviparous fishes

Why some fishes are viviparous? --195.74.79.17 (talk) 21:49, 13 August 2011 (UTC)

If you're asking about the difference between viviparous and ovoviviparous when they obviously both give birth to live young: 'True' Viviparity is when nourishment is given to the embryo other than from its own yolk, the embryos are not covered in membranes. It comes in two flavors - Histotrophic viviparity (literally 'tissue-eating') is when the embryo eats other embryos or other eggs to gain nourishment while inside the mother (cannibalism). Hemotrophic viviparity ('blood-eating') is when the embryo gets its nourishment directly from the mother's own nutrients (like in placental mammals). Ovoviviparity is when the eggs are retained inside the body of the female until they develop fully but do not receive nutrition from the mother (basically they still lay eggs, but they do not let it out of their bodies, hence why they seem to give birth to live young when they hatch).

If you're asking about why they developed the ability to give live birth, that's a more difficult question to answer as it has evolved multiple times separately. Overall, it just might be that lower number of offsprings but greater survival rates is more advantageous than the hit and miss spawn-by-the-millions of egg-laying fishes (though the assumption that viviparous fishes bear less young has been challenged). Especially since fishes which [independently] evolved viviparity do not revert to egg-laying, suggesting that it is advantageous in some way (with the exception of some elasmobranchs which might have reverted, probably because their eggs are very well-protected anyway). Others propose that adapting to a pelagic mode of life may have been important (harder to lay eggs in the open ocean). Still other theories factor in internal fertilization which encourages fiercer sexual selection pressures (sexual conflict), offspring evolving to get more from their mothers since they are propagating mostly her genes anyway (fetal-maternal arms race). etc. No one really knows for sure. *shrugs* Some of those pressures may have also played a role in the evolution of external parental care, even if they aren't viviparous (e.g. mouthbrooding in cichlids, nest-building in sticklebacks, etc.)

See also:

• Life-history correlates of the evolution of live bearing in fishes (Goodwin et al., 2011)
• Evolutionary Origins of Viviparity in Fishes (Blackburn, 2005)
• Parent-Offspring Conflict in the Evolution of Vertebrate Reproductive Mode (Crespi & Semeniuk, 2004)

Lots more papers about it really. Try searching in Google Scholar. -- Obsidi♠n Soul 22:57, 13 August 2011 (UTC)

(ec) Because they are able to survive. See the section Fish#Reproductive method. By far the majority of known fish are oviparous i.e. the eggs develop outside the mother's body. Relatively few have evolved vivaporous reproduction the mother retains the eggs and nourishes the embryos. This gives survival advantages such as continual maternal protection of the embryo and the need for males to compete before mating occurs. For the female to carry the embryo to term, a structural requirement is a placenta. Cuddlyable3 (talk) 23:09, 13 August 2011 (UTC)

If viviparity is more advantageous, why such fishes constitute a minority and aren't positively selected against?--195.74.79.17 (talk) 00:15, 14 August 2011 (UTC)

They were. Again, those which did evolve viviparity did not revert (again with the possible exceptions of one or two elasmobranch lines, I haven't checked reptiles/birds). Also note that evolution is not a straight line, those that did develop viviparity were 'branches', moving on to produce wholly viviparous lineages but not affecting the rest. Lesser fecundity also made sure that even with higher survival rates, they really can't push oviparous species to extinction. The survival of their genes is more assured, but they aren't exactly going to explode in population numbers soon. It also helps if you consider that all higher vertebrates are their descendants (not directly though). In reptiles, viviparity again independently evolved multiple times. It stuck in placental mammals, who took parental care and viviparity to an extreme. Most extremely even, in humans, and we are the most successful species aren't we? -- Obsidi♠n Soul 00:42, 14 August 2011 (UTC)

It's a matter of r and K selection. Small animals like mice are subject to high predation and cannot invest too much in any one child or risk losing it. They have many large litters. Big animals like elephants can invest alot in one child who will have a higher chance of survival and can develop to a more mature physical state before leaving their mother. More than four tiny baby elephants born at once would hard to feed and corral yet much easier for lions to kill.

Which strategy, r (rate) or K (investment), is better for a species depends on many things. Rate selected species are weeds, they can quickly invade new territory when an opportunity arises but are selected out of established territories where you find it hard to get a foothold. Investment selected species can live as the stable dominant organisms of a large, complex, patchy, spatially variable, yet cyclically regular territory. While r selected animals scatter, K selected animals can have culture.

Viviparity is a K selected trait. The young are fewer but much better developed. Since the two strategies have tradeoffs--the K selected species has all its few eggs in one basket, the r selected babies are out of the nest and often depend on mere chance in numbers to survive--no one such strategy is best. μηδείς (talk) 02:00, 14 August 2011 (UTC)

Awesome explanation. Though to be fair, there can be oviparity too with significant investment (like simply laying a very large heavily armored egg, or dedicated parental care), as in the case of dinosaurs (hadrosaurians most famously), and of course, the modern dinosaurs - birds. And some of the largest animals come from tiny planktonic paralarva - giant squids, who still spawn them by the millions. All in all, evolution is really too complicated to pigeonhole neatly. μηδείς' explanation is probably the best in showing how the business of reproduction are really just different strategies all aimed at propagating the genes of the parents. It's a cutthroat game. Like manufacturers producing competing products, some cheap but easily breakable, some expensive but durable. Humans won the jackpot with sentience, but he was already armed with billions of years of genetic weaponry, some unexpressed and laying dormant for future use. BTW, OP has this anything to do with Polycotylus? :P Interestingly, that one seems to be a common thing shared by large pelagic air-breathers - extinct archosaurians, ichthyosaurs, mosasaurs, and plesiosaurs (mammals can perhaps be discounted as viviparity is the default). Though why it hasn't evolved in extant marine birds and reptilia is puzzling. Perhaps they're still too attached to land, too early in their evolution, or simply can't squeeze in a niche in the current pelagic marine ecology (thus being restricted to shorelines, they still can access land and thus have no need to be viviparous), or something. Sea snakes are though. -- Obsidi♠n Soul 03:08, 14 August 2011 (UTC)

Yes, but in the case of fish eggs I can't imagine any large armoured ones unless you look at the elasmobranchs which tend toward live birth or at the mouth brooding cichlids where the father serves as the large armoured part--and they lay no where near the number of eggs as do oviparous non-brooders.

Live bearing is the advantage of the mammals and the bearing of precocious young is what allows bats to fly and whales to swim. Marsupial whale babies would drown in the pouch. The problem with Penguins and sea turtles switching to live bearing is that the intermediate stage, young born quickly from a weaker egg, is less adaptive than young born well developed from a thick shell. There's no way to get over the hump in between the two strategies. μηδείς (talk) 04:09, 14 August 2011 (UTC)

Yeah. The sea is far more hostile than their land habitats, and penguins and sea turtles aren't exactly equipped to defend their young against predators. Unless they find a relatively benign ecology somewhere where they might slowly lose the necessity for land incubation and thick-shelled eggs, they can't really make the leap to viviparity. The oviparity of extant archosaurians is a trickier question. Why didn't they? Though while modern archosaurians don't bear live young, their extinct exclusively marine flipper-limbed counterparts might have (no evidence, possibly yet, though). It does seem to be a chicken or egg question. Did viviparity give air-breathers the edge to become truly marine and to reach large sizes, or did large sizes and a completely marine lifestyle force viviparity? Probably a little of both.-- Obsidi♠n Soul 16:18, 14 August 2011 (UTC)

Yes, I was thinking that you could probably get ovoviviparity in cold-blodded sea turtles with a relaxation in selection pressure. But an insuperable problem birds face is the oxygen demands of their high metabolism. A chick born into the water would have to be highly developed, like a post-molt juvenile, not just a newly hatched chick. But in emperor penguins, comparable in size to seals, whose eggs are incubated for 64 days, it would be hard to maintain the chicks oxygen needs inside the body as it developed from fertilised egg to newborn. Let alone to sustain it in the body for the two months it spends as a nestling and the months it spends as a crecheling until it is ready to molt and enter the sea. And of course whales can feed their newborn young with milk, while penguins would have a hard time regurgitating food to their young in the open ocean. I am afraid that for birds you simply can't get there from here. A shame, as I always loved Dougal Dixon's porpins.μηδείς (talk) 21:44, 14 August 2011 (UTC)

Leptictidium Cretaceous

Did Leptictidium live during the Cretaceous? Pinguinus (talk) 22:44, 13 August 2011 (UTC)

We can only base possible geologic time ranges on the earliest fossils known. According to our article Leptictidium, no. It existed during the Middle Eocene of the Paleogene period, Cenozoic era. Specifically from the Late Ypresian to the Middle Bartonian ages (50 to 35 million years ago). The Cretaceous period ended 61.7 million years ago, which was around 11.7 million years before the first known fossils of Leptictidium.-- Obsidi♠n Soul 00:28, 14 August 2011 (UTC)

Deep sea fish and rupture of something (I guess)...

Been watching fishing shows on TV again. These guys were fishing in deep water in the South Pacific and they pulled up a couple of big fish (from memory, I think they were Hāpuku) from the depths. When brought to the surface, these fish had something that belonged on the inside sticking out of their mouths, all ruptured and grossly inflated - it was a pink, basketball-sized lump of flesh. I think this was some sort of decompression injury caused by the sudden change in water pressure (I've read about that happening to fish, but I've never seen it before) and it was obviously fatal. Does anyone know what manner of tissue or organ this would be? An inside-out stomach? --Kurt Shaped Box (talk) 23:38, 13 August 2011 (UTC)

Probably the swim bladder, but it in turn could push out other stuff. It's called barotrauma. It's discussed in both Swim bladder and Catch and release#Deep sea fishing and catch and release.-- Obsidi♠n Soul 00:15, 14 August 2011 (UTC)

Thanks very much. That sounds like it. --Kurt Shaped Box (talk) 20:25, 14 August 2011 (UTC)

We have this same issue with rockfish here in Alaska. If you catch one when fishing for halibut you pretty much have to keep it per [8]. Beeblebrox (talk) 20:55, 14 August 2011 (UTC)

Yeah, the anglers on TV were pretty much 'oh crap, we'd better move on from here - I hate bringing these up' - they'd caught them one after the other in short order while fishing for something else. --Kurt Shaped Box (talk) 21:08, 14 August 2011 (UTC)

August 14

Brownian ratchet (again)

Hi, looking at the article Brownian ratchet, it seems to me that if the cog wheel and pawl, as well as the structures fixing them in place, were made out of a hypothetical material that was completely rigid on an atomic scale in the face of thermal noise, then the device would work as advertised in violation of the laws of thermodynamics. Is that true? Do the laws of thermodynamics in themselves make the existence of such a material impossible then? 86.160.83.115 (talk) 01:24, 14 August 2011 (UTC)

No, it would not work in that case. Since thermodynamics is nothing more than information theory applied to Nature, the best way to see through paradoxes like this one, is to translate it in terms of information. Although it may not always allow you to actually do detailed computations, for that you may need to consider the detailed dynamics (which in this case involves rather complicated non-equilibrium thermodynamics).

So, if a molecule strikes the wheel in the right way, it will move, pushing the pawl. But the pawl (assumed to be rigid) will then oscillate. This motion can cause the wheel to move backward. This motion, being a consequence of the molecule striking it, contains the information that a molecule made the wheel move earlier. For the device to work as advertised, you need to get rid of this information. But the fundamental laws of physics forbid you to erase information completely from the universe. The best you can do is dump the information from the unwanted place (the pawl) to somewhere else. For this to happen by itself requires dissipation of the energy, but that won't happen in thermal equilibrium. Count Iblis (talk) 15:29, 14 August 2011 (UTC)

A closely related way to see through this, is to consider time reversal symmetry. Under time reversal a final state will evolve back to an initial state, which implies that the final state contains the information present in the initial state. If you consider the process that moves the wheel in the right directon, then you can see how the wheel would move in the wrong direction by applying time reversal to that process. In thermal equilibrium, both processes occur with equal probability. Count Iblis (talk) 15:47, 14 August 2011 (UTC)

The "Why it fails" section of the article explains that the machine fails because "a ratchet and pawl small enough to move in response to individual molecular collisions also would be small enough to undergo Brownian motion as well. The pawl therefore will intermittently fail by allowing the ratchet to slip backward or fail by not allowing the ratchet to slip forward." Is this explanation incorrect or incomplete? If it is correct and complete then why would my magic material not eliminate the (relative) Brownian motion of the pawl and the cog, thereby preventing the ratchet from slipping? 109.153.232.146 (talk) 20:50, 14 August 2011 (UTC)

If you assume that the pawl doesn't dissipate energy, then it will flutter hence and forth and that will make the set up to fail to work. So, te given explanation is incomplete. It's similar to the old arguments puporting to show why Maxwells Demon fails. While these analyses are technically correct, they are sort of "Straw Man arguments", i.e. they make assumptions and then one shows that the set up fails, but that is then due to the assumptions that are made. Then, if you make a different assumption, like you did here, it seems that the thing really can work.

Like in case of Maxwell's Demon, the fundamental reason why this doesn't work was given by Landauer: you can't erase information, at best you can move it, and there is an entropy cost to be paid for that (so that won't happen in thermal equilibrium).Count Iblis (talk) 21:20, 14 August 2011 (UTC)

Thanks. The need for the pawl to dissipate energy may be a way forward for me to understand why my proposal would not work. Unfortunately the "information" argument is beyond me; I don't even begin to understand how it's relevant. If you think the article's explanation is incomplete and ever have the time and inclination to improve it then I'm sure that would be appreciated by readers. 109.153.232.146 (talk) 21:53, 14 August 2011 (UTC)

The article explanation is fine. You seem to think that your rigid material would be immune to Brownian motion. It would not. Dauto (talk) 21:57, 14 August 2011 (UTC)

The article said (before I fixed it) "a ratchet and pawl small enough to move in response to individual molecular collisions also would be small enough to undergo Brownian motion as well" [sic]. That makes no sense. "Movement in response to individual molecular collisions" is Brownian motion. I think the OP was misled by that sentence and imagined a device that's immune to one but not the other. -- BenRG (talk) 22:37, 14 August 2011 (UTC)

My idea was that the rigid material would be immune to "internal" Brownian motion affecting the positions of the pawl and cog relative to one another. I did not imagine the rigidity would prevent the whole assemblage from jiggling about in unison if hit, say, by air molecules. 109.153.232.146 (talk) 00:21, 15 August 2011 (UTC)

The latter IS Brownian motion. The first is thermal agitation. Brownian motion is the apparently random jitter of objects due to the action of molecules on them. Dauto (talk) 01:33, 15 August 2011 (UTC)

Oh, thanks, I think I have been misunderstanding this. I was imagining that the slippage was due to relative motion between the pawl and cog caused by this "thermal agitation", but in fact the whole assemblage jittering about even in unison would jiggle the pawl and allow the ratchet to slip? That seems to make sense; is that right? I guess any spring/gravitational force strong enough to defeat this would also stop the cog rotating in the desired direction? 86.160.84.240 (talk) 11:46, 15 August 2011 (UTC)

Are hummingbirds territorial?

We have three or four ruby-throated hummingbirds which frequent our backyard bushes and feeder. Lately, one female seems to be hanging around longer than most. She will spend most of the day perched or resting in a weiglia bush which is aboutr 20 feet from the feeder. When another humingbird attempts to use the feeder, whe will leave her perch and chase off the "intruder". Is this normal behavior? JDBakerJdbaker5 (talk) 01:44, 14 August 2011 (UTC)

Yes, extremely. Given their high metabolism, food is a very high value localized commodity for hummingbirds. It's half the fun of watching them. μηδείς (talk) 01:48, 14 August 2011 (UTC)

We have three feeders, none visible from the others, arranged around the house, and probably at least 6-8 hummingbirds in the neighborhood. They're constantly chasing each other in circles around the house from feeder to feeder. It appears that all get enough food, but the behavior is typical of ruby-throated hummingbirds. Other species seem to be less territorial. Acroterion (talk) 13:29, 14 August 2011 (UTC)

If they were colonial and had stings like bees they'd be frigging terrifying. (Reminds me of monsters from A Case of Conscience and Beowulf's Children. μηδείς (talk) 19:25, 14 August 2011 (UTC)

Using gene therapy to change physical characteristics

Is it theoretically possible to use gene therapy to change physical characteristics like... hair or eye color? Something like that? ScienceApe (talk) 02:16, 14 August 2011 (UTC)

It certainly is, but the symptoms of the infection and the reactions that might occur could be like having the symptoms of HIV and the pox or viral meningitis at the same time. A certain percentage of human obeistiy is likely caused by viral infection. Keep in mind that many traits depend on development, so, for instance, once you've reached adulthood and your bones have stopped growing, a gene for a bigger body frame won't do anything. You will not be the one you want to have such methods tried on first. Read Michael Crichton's Next and its afterword. Read the brilliant Dark Benediction by Walter M. Miller.μηδείς (talk) 02:58, 14 August 2011 (UTC)

Yes. However, note that the characteristics wouldn't change in a few seconds or minutes, like in your average bad sci-fi movie. More likely they would change as the hair or eye pigment is naturally replaced, so over the course of weeks or months. In the case of hair, this might lead to a "bad dye job" period with different colored roots. They eye color might also be somewhat unattractive when midway between the two colors. StuRat (talk) 03:08, 14 August 2011 (UTC)

How massive?

How much mass must an asteroid have to have a large influence on tectonic activities when striking earth?--Irrational number (talk) 10:32, 14 August 2011 (UTC)

I wrote a Spanish article a bit related: es:Crust tsunami (video). emijrp (talk) 10:58, 14 August 2011 (UTC)

Created a stub: Crust tsunami. emijrp (talk) 11:13, 14 August 2011 (UTC)

thanks... a bit more?:D--Irrational number (talk) 13:09, 14 August 2011 (UTC)--Irrational number (talk) 13:09, 14 August 2011 (UTC)--Irrational number (talk) 13:09, 14 August 2011 (UTC)

I can find no sources either at GoogleBooks or GoogleScholar that even mention "crust tsunami" - where have you seen the term used apart from the video? Mikenorton (talk) 21:03, 14 August 2011 (UTC)

I think Emijrp mis-heard what was on the video. The announcer says crest tsunami, not crust tsunami. At least I think that's what he says. That term doesn't seem to show up on Google Scholar either; it may have been just a nonce term. --Trovatore (talk) 08:55, 15 August 2011 (UTC)

Can anyone answer my question...?--Irrational number (talk) 08:23, 15 August 2011 (UTC)

Well, the Spanish source, taken for what it is, says "centenares de kilometros" which means "hundreds of kilometers", which certainly would splash the crust. Anything that big won't leave witnesses. Leaving aside the reliability of the sources, the Spanish article specifies crust tsunami, whereas crest tsunami simply makes no sense in the context. μηδείς (talk) 15:57, 15 August 2011 (UTC)

See "Meteor Pelting May Have Triggered Plate Tectonics" μηδείς (talk) 16:01, 15 August 2011 (UTC)

I'm not sure how much support that idea has, but it is interesting that the onset of subduction (and thereby plate tectonics) has recently been dated to 3 billion years ago from the observation of inclusions in diamonds [9]. Mikenorton (talk) 17:14, 15 August 2011 (UTC)

Time it takes solar system to orbit around the galactic centre.

I have read a lot of articles that tell me that its 225 million years.

I would like to know how astronomers have measured this, also does this mean that the deep sky objects will "move" into other areas of the sky ?

thx :) — Preceding unsigned comment added by 92.30.186.14 (talk) 12:15, 14 August 2011 (UTC)

The movement of stars in the night sky relative to each other and very distant objects is called proper motion. That's caused by the relative motion of the stars and our solar system. The estimate of the length of a galactic year (and it's a pretty rough estimate) is got by measuring the distance to the centre of the galaxy (see cosmic distance ladder for how distances are measured), using that to estimate the length of the Sun's orbit and then measuring the speed of the sun through the galaxy to get how long it will take to complete one orbit. I'm not quite sure how the orbital speed is measured, though... it's easy enough to work out how we're moving relative to nearby stars, but they are also orbiting the centre of the galaxy, so that doesn't help much. See Sun#Motion and location within the galaxy for some more details. --Tango (talk) 13:45, 14 August 2011 (UTC)

One has to identify objects that belong to the halo of the Milky Way, not the disk. The halo shows no net rotation, so one can determine the Sun's velocity relative to the mean of these objects. Candidates are globular clusters and so-called high-velocity stars. If one plots their velocity vectors, they show an asymmetric distribution with a centroid at around −220 km/s (so-called "asymmetric drift"). --Wrongfilter (talk) 18:15, 14 August 2011 (UTC)

Identify (?) bomb

Bomb? (click to expand)

This is from RAF Cowden, an aerial bombing test range, possibly a bomb. But is it actually a bomb or something else? (I didn't take the photograph so I don't know the scale but it must be ~1.5ft long) - looks odd for a bomb.. What is it? Thanks. Imgaril (talk) 16:40, 14 August 2011 (UTC)

It is quite possibly an older aerial bomb which has lost its tail fins. I'd watch my step in that area. Beeblebrox (talk) 21:03, 14 August 2011 (UTC)

Such things are common in former artillery ranges, even those which supposedly have been "cleared." In the U.S. at least one has been turned into a park (Tobyhanna State Park in Pennsylvania) which issues warnings about finding old ordnance to visitors.

Compare the images on this page. Possibly the front half of a practise bomb. Nanonic (talk) 23:47, 14 August 2011 (UTC)

This is what's called a shell, which may or may not carry an explosive payload which might be called a bomb. (The mistake would be analogous to showing a picture of an envelope and calling it a letter. An envelope is not a letter and may or may not contain a letter.) What sort of shell this is I haven't a clue. μηδείς (talk) 01:34, 15 August 2011 (UTC)

Thanks - Nanonic's images of the 'BDU-33' nailed it - looks the same - (though I though the one here looks bigger).Imgaril (talk) 02:06, 15 August 2011 (UTC)

Fly stickers - do they work?

Got myself a recurring fly/midge problem in my kitchen bin this summer. Those coloured, flower-shaped window stickers that claim to kill flies (that you can find really cheap on eBay). Do they really work as well as is claimed? --Kurt Shaped Box (talk) 20:24, 14 August 2011 (UTC)

Taking out the garbage works great. Looie496 (talk) 21:26, 14 August 2011 (UTC)

Sounds like a cuter version of flypaper, which works fine but is not at all pleasant to look at. Beeblebrox (talk) 21:29, 14 August 2011 (UTC)

Naw man, I *do* take out the garbage when the bag is full. However, I have loads of flies in my bin again about a day later when there's very little in there (just some mandarin peel and a couple of apple cores today - opened bin to drop in pizza box and flies erupted). I'm not sure where they're coming in from. They're not regular houseflies - these are much smaller (maybe 4mm long). --Kurt Shaped Box (talk) 21:36, 14 August 2011 (UTC)

Almost certainly part of the Drosophila family attracted by, err, mandarin peel and apple cores. Nothing an appropriately sized seagull couldn't sort out, I'll be bound. I've used the window stickers to try to kill other sorts of flies: no joy. --Tagishsimon (talk) 21:41, 14 August 2011 (UTC)

Seagulls, hehe. μηδείς (talk) 21:47, 14 August 2011 (UTC)

I wish that this bird was my gull-friend. --Kurt Shaped Box (talk) 21:52, 14 August 2011 (UTC)

There may be something else attracting them, a lingering smell in the bin perhaps? Keeping in mind that many bugs find their food almost entirely by smelling for it, you may want to consider scrubbing the inside of the bin with bleach or something. Even if you can't smell it, they apparently can. Beeblebrox (talk) 21:43, 14 August 2011 (UTC)

Yes, almost certainly fruit flies, given the examples. If you eat a lot of fruit, you might consider throwing the cores and peels and whatever outside immediately. They're biodegradable anyway :P -- Obsidi♠n Soul 21:46, 14 August 2011 (UTC)

I moved to Georgia (US) last summer from parts further north and both this and last summer I've had a similar problem with fruit flies in the trash. Once they take hold it's hard to get rid of them. If there's any sort of food waste in the trash they're back with in a day or two of taking out the garbage. One thing I've found that helps a lot is to scrub out the trash bin. The flies lay eggs on the inside of the lid and inside of the bin itself (outside of the bag). You'll see a lot of fly maggots hanging out here (the eggs themselves are hard to see). Cleaning the bin is not guaranteed to fully eradicate them, depending on how thorough you are, but it will at least keep the numbers in check. I haven't heard of those stickers so I don't know if they work. I did read online that you can make a trap with vinegar and some detergent, and it was completely ineffective. Rckrone (talk) 22:13, 14 August 2011 (UTC)

Keep garbage (kitchen waste, as opposed to trash) in the freezer until you take it to the curb. μηδείς (talk) 22:19, 14 August 2011 (UTC)

Freezer is one option. Garbage disposal is another. Flushing is a third. Putting them in the outside trash is a fourth. A sealable "slop jar", such as an old coffee tin, is a fifth option. There's just no need to leave fruit fly food out in your home where fruit flies can get to it. StuRat (talk) 23:35, 14 August 2011 (UTC)

As for your current population, one method which can work is to leave out plates filled with lemon-scented (hand) dish-washing detergent. The lemon scent attracts them, and the detergent traps and kills them. StuRat (talk) 23:38, 14 August 2011 (UTC)

Keeping everything in the fridge or freezer, including grain food from the pantry and food scraps from the garbage (assuming, as in NYC, garbage disposals are illegal or you have a septic tank) will work against mice, rats, house flies, fruit flies, roaches and A Flock of Seagulls. Flushing helps too but leaves a mess between kitchen and toilet. μηδείς (talk) 00:51, 15 August 2011 (UTC)

Thanks for the tips, guys. I've never ever had this problem before. Sure, I've had insects get in my house (who hasn't?), wasps nests, flying ant day crap, etc. but never an infestation of the little bastards on this scale. --Kurt Shaped Box (talk) 00:59, 15 August 2011 (UTC)

I'd guess the core of the problem is that a pregnant female found it's way to your rotting garbage. StuRat (talk) 03:01, 15 August 2011 (UTC)

I had a problem with fruit flies and those stickers were very helpful (they become more effective once a few flies are stuck to them - that seems to attract other flies more than the smell). The other thing I found useful was a vacuum cleaner. I would use it to literally suck them out of the air. It took several weeks to get rid of them completely, but they're gone now. --Tango (talk) 11:34, 15 August 2011 (UTC)

August 15

Why are humans physically weak?

It seems to me that humans, compared to animals of similar weight and size, are quite weak. Especially taking into account the fact that we live in an advanced civilization were food containing the right amount of nutrients is served on time, we can get enough rest etc. etc., while animals cannot assume that they'll have the optimal amount of food every day.

Also we need to do quite a lot of exercise to be fit, while e.g. gorillas are much stronger than humans, even though they eat and sleep all day long. Count Iblis (talk) 00:12, 15 August 2011 (UTC)

Who needs physical strength when our brains allow us to coordinate our violence and use pointy sticks ? Warning - a very violent video, though it's the best example that I can think of that demonstrates man's (even those men that some would dismiss as 'primitives') utter superiority over far stronger animals. --Kurt Shaped Box (talk) 00:33, 15 August 2011 (UTC)

(Edit conflict) We don't depend on our strength for survival as a species, our cognitive ability has usurped that position. We used to be stronger not so long ago, you can see a record of decrease in masculinity and bone density only as recently as 1000 years ago. Plasmic Physics (talk) 00:37, 15 August 2011 (UTC)

The video isn't particularly good as an example, as the voice over is used to make the sociological points (rather tacky ones at that), rather than the cinematography or contents. As far as I can tell it also shows different people (dress, number of people, hunting styles) hunting different animals in different ways in different terrain. Some of the shots are obviously out of sequence. And it requires more than a little elementary reading to observe the role of mutual aid in hunting here due to its obscuration. Wouldn't Kropotkin's Mutual Aid—despite its methodological problems and age—make this point better? Fifelfoo (talk) 01:49, 15 August 2011 (UTC)

Kurt's linked movie incongruously shows hunters with primitive spears and wearing obviously machine-made short trousers. Why in such a large crowd has no one thought of using a bow and arrows which would save a lot of running? These are posed movie scenes using many extras not all of whom own spears or do more than jiggle them. ~~

Starvation seems to have been rampant in our past, such that we've evolved to use as little energy as possible. Thus we only develop big muscles when our body detects a need for them, that is, when out current muscles are overtaxed. StuRat (talk) 00:41, 15 August 2011 (UTC)

Exactly. μηδείς (talk) 00:47, 15 August 2011 (UTC)

Let's forget about the big brains for a second, just for the point of argument. In terms of physical fitness (from an evolutionary standpoint), there is a lot more than just "strength". Gazelles are not very strong, compared to a cat of the same size. But that's because they are optimized (by evolution) for speed. Some animals are clearly optimized for raw strength. Humans, taken from a purely physical view, and throwing out the lazy excesses of modern life, are optimized to be somewhat mediocre in strength (not at all "weak" — consider that humans whose lives rely on physical strength, like professional athletes, are actually pretty strong), mediocre in speed (we don't run terribly fast), but we are great at endurance. Check out the Man versus Horse Marathon for example — even horses, which we think of as being great draft animals (and are only as great as they are because we bred them for thousands of years), are pretty poor compared to humans over long hauls. We're great long distance runners. We have way more endurance than the gazelle like animals who can conjure up huge amounts of speed but not for very long. We fit a specific evolutionary niche, even without the brains (which can't be left out, in the end — your evolutionary niche changes once you can hunt in packs, use weapons, etc.). We are also terribly versatile — our body is great at regulating temperature and dealing with very different climates, which is something that a lot of very strong or very fast animals do not have. Having tons of extra muscle mass would not only require a very different type of diet (more reliably protein rich than we had for most of our evolutionary history) but would reduce that endurance advantage. I don't want to tell a "just so" story, but it seems rather clear that we have long occupied a very different type of evolutionary niche than, say, a gorilla, or even a chimpanzee. The particular primates we have evolved from all look like creatures that survived on endurance, adaptability, and intelligence, none of which are particularly served by gigantic muscles. --Mr.98 (talk) 01:46, 15 August 2011 (UTC)

Yes, the points of endurance and human eye-hand and other types of co-ordination (which are also highly important for speech) are quite important. Imagine an orangutan ballet. μηδείς (talk) 02:16, 15 August 2011 (UTC)

Even more-so than eye-hand coordination is simply the intricacy of control of the hands and fingers in general. Humans are capable of some rather minute and complex hand and finger control. Even ignoring the problem of figuring out music in general, I'm not sure you could teach a chimpanzee to play halfway decent electric guitar, or to stitch a quilt, or anything like that. I'm not sure that any other animal has the motor control that humans do over their fingers. --Jayron32 02:53, 15 August 2011 (UTC)

Yes, I was negligently vague in saying just eye-hand co-ordination. We also have amazing coordination of our faces and vocal apparatuses. Speech is essentially a sort gesture transfreed to the mouth. Another thing to consider is that we can transfer learned modules from one organ to another, for instance signing our signatures, which we have only ever practised with our fingers, to a pen held by our lips or our toes. That's actually quite amazing and something no animal can really copy. μηδείς (talk) 03:18, 15 August 2011 (UTC)

That's quite a formidable wall of text you people have conjured up, so forgive me if I'm echoing a previously stated point: Who needs strong muscles when you have the knowledge to smith a sword? --Σ _{^talkcontribs} 03:37, 15 August 2011 (UTC)

Because big muscles are required to wield the sword, of course. StuRat (talk) 03:50, 15 August 2011 (UTC)

Smithing a sword is actually a pretty recent innovation from an evolutionary standpoint. It's not what got us through those thousands of years before civilization really started up. The real human innovations are being able to organize themselves in groups, be extremely adaptable, and have lots of fine motor skills. High tech (which metal smithing counts as) is pretty cool but didn't play any real role in our evolutionary history, except for the fact that it allowed a few groups of humans to kill out a bunch of other groups of humans. --Mr.98 (talk) 15:06, 15 August 2011 (UTC)

Well, actually you do see heavier musculature in areas like New Guinea and Subsaharan Africa where physical competition between equally armed males is more important for reproductive success. Males in New Guinea tribes that still practice intertribal warfare can have the same chance as male chimps, about 30-35% of dying in violence. To the victors go the ladies. See the well written and researched Before the Dawn. μηδείς (talk) 03:46, 15 August 2011 (UTC)

I agree entirely that the strength of humans is really underestimated by most here in this thread. Humans whose life depends on their raw strength (rare in any state of "civilization") are pretty formidable creatures. They couldn't arm wrestle with a full grown chimp, but they are not indefensible weaklings. The fact that all its takes is a spear to hunt lions says something quite profound about the abilities of humans to be pretty dangerous even without a huge amount of technological augmentation. Stone age man was a pretty formidable animal, as the record of megafauna extinction shows. --Mr.98 (talk) 15:06, 15 August 2011 (UTC)

I feel this thread is going somewhat off track when talking about all the things humans are good at. This would only be relevant if they were somehow mutually exclusive with being strong. I don't see how having dexterity in the fingers precludes strength, for example. We should instead focus on the disadvantages of strength. The two I've seen mentioned so far are the energy requirements and the need to eat meat on a regular basis. StuRat (talk) 03:48, 15 August 2011 (UTC)

Well, and the fact that hypertrophy in certain areas leads to hypotrophy in others. (There's a Somebody's Law about that in developmental biology, but I forget who.) Big muscles do compete with big brains and other sorts of costly development. Heavy musculature didn't lead to Neanderthal dominance Given we interbred, and the gracile form succeeded, that likely says alot. You can't look at just musculature and judge its value on its own. Biology doesn't work that way. You have to look at other tradeoffs like long distance stamina and human memory and coordination (which are interrelated) to make any holistic sense. Otherwise, by itself, cost no object, bigger muscles will obviously be beneficial. μηδείς (talk) 04:05, 15 August 2011 (UTC)

The endurance running hypothesis is probably the favoured reason for why we are not built for strength. Look at the winners of the marathon event and you'll see what's optimal for persistence hunting where one man can hunt down and kill an antelope with a stone. Wolves are the other main persistence hunters, they have a bit more speed and use teeth instead of stones but have less persistence. Dmcq (talk) 12:48, 15 August 2011 (UTC)

So would it be safe to assume that other apes don't have anywhere near the endurance that humans do, and that the distance covered by the ape army in Rise of the Planet of the Apes is pretty unrealistic? (Because otherwise the film is very plausible!) —Akrabbim^talk 14:22, 15 August 2011 (UTC)

It is a fact that other apes do not have the body structure or musculature to endure long distance upright walking, let alone the endurance for long marches. Apes revert to knuckle walking about as quickly as we revert to flat footed from tippy-toe walking.No ape other than Oliver (chimpanzee) has ever been documented as adopting an upright stance as a matter of habit, hence speculation as to his unique species status. As for plausibility, that depends more on the ignorance of the audience than the accuracy of the artwork. For example, those who know nothing of physics might accept the notion that there could be such a thing as "red matter" which could in the most recent Star Trek movie be used to create a black hole. But any knowledge of gravity and the types of substances that exist show the idea to be ridiculous, not to mention the idea that a supernova of one star could immediately destroy a planet in another system over as was done to Romulus. I have not seen the new Apes movie (the first remake was dreadful) so maybe I am wrong, but given what I know about the creators I don't find it plausible that it will be plausible. μηδείς (talk) 15:47, 15 August 2011 (UTC)

Thanks everyone for the replies so far. Reading all the replies, what is still an issue is more or less what StuRat wrote above about why physical strenght would have to come a the expense of physical strength. Of course, having an extremely muscular body build may not be comaptible to being able to perform well at long distance running, while the latter ability may have been important for us in the past. Now, it seems to me that humans are more susceptible to become "couch potatoes" when they don't exercise a lot while a gorilla can just eat and sleep all day long. As suggested above, that has to do with the human body adapted to deal with famines. Count Iblis (talk) 17:23, 15 August 2011 (UTC)

Guinea pigs and motion sickness

According to author Mary Roach in the book Packing for Mars (2010), guinea pigs do not suffer from motion sickness. Why is this? Viriditas (talk) 06:21, 15 August 2011 (UTC)

Googling "guinea pigs motion sickness" brings up several research papers that suggest this is untrue.--Shantavira|^{feed me} 07:41, 15 August 2011 (UTC)

I think Roach means to say that guinea pigs don't suffer from motion sickness in zero-g. In any case, I'm not seeing anything showing they suffer from motion sickness like other animals. Viriditas (talk) 10:11, 15 August 2011 (UTC)

A key point is probably 'what do you mean by motion sickness in zero-g'? If you mean something that really is motion sickness that occurs in zero-g environments, then there's no to think any animal which gets motion sickness won't get it. This ref [10] ([11]) supports the conclusion that what you call 'zero-g motion sickness' or is also (and more commonly) called space (motion) sickness or space adaptation syndrome is indeed a form of motion sickness. That being the case, there's reason to think animals which get motion sickness aren't going to get zero-g motion sickness. However the ref also suggests it's still something that is poorly understood (in terms of what causes it).

While there has been a fair amount of research, I don't find much evidence it's been that well observed in animals in space. A lot of research treats space motion sickness as a form of motion sickness, so use methods to stimulate it. Notably from a few quick searches, I can't find any refs discussion space motion sickness in dogs or guinea pigs or mice. However, it has evidentally been observed in monkeys [12].

BTW [13] mentions guinea pigs and rats are a poor model for ('normal') motion sickness since they don't vomit (leading to dogs and monkeys being the most commonly used ones). The earlier ref on space motion sickness also mentions this for rats and rabbits. Evidentally Suncus murinus can be made to vomit and do get motion sickness including vomitting [14]. Cats have also been suggested as models [15], including for zero-g maneuvers in parabolic flight, although I presume that's a poor model if you believe space motion sickness is unique, since the maneuvers would generally induce motion sickness ala Airsickness anyway hence Vomit Comet. (I should mention I didn't read the article as I don't have access to the archives [16].)

From [17] and [18], I gather antiemetic drugs are one of the targets to try and prevent or reduce space motion sickness, which isn't surprising since it's perhaps one of the worse symptoms. Some experiments relating to space motion sickness have used guinea pigs [19] (admitedly a rather long time ago) and more recently rats [20] which would seem odd if the researchers did not believe they could get space motion sickness.

All this leads me to conclude there's no reason to believe guinea pigs don't get space motion sickness. They don't vomit, so are often a poor model for motion sickness, unless you use a more sophisticated system, although this still won't work if one of you specific targets is vomiting. But it seems to be usually accepted (as Shantavira said) they do get ('normal') motion sickness e.g. [21] [22] [23]. As hinted at earlier, other non-emetic species like rats [24] [25] also seem to be considered to show motion sickness (the first ref on space motion sickness also mentions this in general). This old article [26] doesn't entirely agree, but that just seems to relate to the lack of vomitting. If you follow a similar definition then the answer is obviously, no they don't get motion sickness including space motion sickness. (IMO a more logical POV is they do get motion sickness but it isn't as bad as in some other animals due to the lack of vomitting.)

BTW one of the key signs of motion sickness in non-emetic animals appears to be pica and immobility (from the first ref but I think I also read it elsewhere) although there are also other symptoms like those relating to food and water intake, urination and defacation.

Also I would point out from what I've seen (and as is hardly surprising), that at the current time most research on space motion sickness is targetted at ways to reduce and prevent it, as well as trying to understand it, ultimately for humans. The well-being of pet or research guinea pigs in space may be a minor concern but isn't the biggest concern (by which I mean researchers probably aren't going to spend great amounts of time studying space motion sickness in guinea pigs so they can work out what harm it is doing except to study the effects in general or to prevent their experiments being screwed up by sick guinea pigs).

P.S. I just found [27] which does mention space motion sickness in rats.

Nil Einne (talk) 14:55, 15 August 2011 (UTC)

What leaf is this?

can anyone tell me what leaf this is?Accdude92 (talk) 06:39, 15 August 2011 (UTC)

It look quite a lot like basil (Ocimium basilicum). Richard Avery (talk) 07:07, 15 August 2011 (UTC)

(e/c) Most probably basil (possibly an Ocimum basilicum cultivar).

But we can't really know for sure without other info. Where is it from? Can you describe the odor? Do you have pictures of other parts of the plant? Can you describe the flowers? How large is it?-- Obsidi♠n Soul 07:18, 15 August 2011 (UTC)

Quantum mechanics/many-worlds

If I understand correctly, then the many-worlds interpretation of quantum mechanics implies (among other things) that for every quantum mechanics experiment performed, there is a universe created that observes every possible result, e.g. if an experiment is performed, and a particle is measured that can be in state A or state B, then there will be a universe in which the outcome is A, and a universe in which the outcome is B. Does this mean that there would be a universe in which the results of every single quantum physics experiment ever would be consistent with a wholly deterministic (i.e. not probabilistic) theory of quantum mechanics? Like, as in, all the scientists in that universe (justifiably) think if you set up x equipment in y configuration and perform a measurement, then you will always get z result without fail, and they all have no idea what 'superposition of states' means? --superioridad ^(discusión) 11:33, 15 August 2011 (UTC)

Yes. When scientists do experiments they usually look at what the probability of such an outcome is given the theory they are testing (eg. classical mechanics) and if that probability is very low (less than 5% is common, although some fields use much lower values) then they reject the theory and try and come up with something else. Just because there is a less than 5% chance of something happening obviously doesn't mean it can't happen, so there is always a possibility of incorrectly rejecting a correct theory. Since it's possible for that to happen once, it is also possible for it to happen every time. Under many-worlds, anything that is possible happens in some universe, so if many-worlds is correct there must be universes where no-one has ever noticed a quantum effect. The "density" of such universes in the multi-verse would be extremely low, though. --Tango (talk) 11:40, 15 August 2011 (UTC)

No. When repeating the experiment, the longer the uninterrupted run of outcomes A (or B) the rarer the universe. An infinite run is unobtainable due to the finite time to measure (frequency of measurements) and lifetime of that universe. NB: The "rarity" or low probability of a universe is irrelevant if you are in it. This one is probably one of the rare ones. Cuddlyable3 (talk) 12:10, 15 August 2011 (UTC)

The example given isn't well specified, because you have a continuum of superpositions of the form cos(theta)|A> + sin(theta)|B>. Then you could assume that for every theta there only has been one outcome (A or B), and this similarly generalized for more complicated superpositions. This is then equivalent to replacing the Born rule probability by a probability function that can only take the value of either zero or one. But then, you can't observe interference effects anymore, so you don't reproduce classical phenomena correctly, like refraction of light, sound waves etc. etc. Count Iblis (talk) 15:32, 15 August 2011 (UTC)

I think there could be such a universe (with a bit more specification), but I don't think there would be any scientists in it to carry out experiments. The existence of life as we know it depends on the principles of thermodynamics, which would completely break down in that universe. (The laws of thermodynamics are statistical, not directly physical.) Looie496 (talk) 16:13, 15 August 2011 (UTC)

Also note that quantum effects aren't only measured or observed by humans in experiments, quantum states collapse everywhere due to a wide variety of phenomena. Alternate universes would be created unimaginably often in the Many-worlds interpretation. Many academics do not lend much credibility to the interpretation. Rosilisk (talk) 16:39, 15 August 2011 (UTC)

Rckrone (talk) 17:14, 15 August 2011 (UTC)

You just have one big static multiverse, the state of this satisfies the equation H|psi> = 0. The splitting doesn't happen on the level of the multiverse, it's just what you get when you focus on a particular component of |psi> in the basis of "pointer states", apply the operator exp(-i H t) and then expand what you get again in that pointer basis. Count Iblis (talk) 17:34, 15 August 2011 (UTC)

I don't understand that, but you mentioned "splitting", and a couple of people spoke of universes being "created", and those are both conceptual pitfalls. The universes in the many worlds interpretation are equivalent to instants of time: therefore they don't change, or age, or have a point in time at which they are created or split apart. They are points in time, and pre-exist. Perhaps, though, that's what you just said? 81.131.26.155 (talk) 09:17, 16 August 2011 (UTC)

For the record, I meant things behave only in a seemingly deterministic manner in certain experiments (through sheer chance), not in all cases (i.e. everyday quantum interactions that happen constantly go on as usual). But, of course, as has been mentioned, you wouldn't be able to reproduce classical effects properly if you counted them as "quantum mechanics" experiments. But if classical physics (say, diffraction of light) works, and more fundamental, particle-physics-oriented stuff demanded a deterministic, non-probabilistic explanation, (suppose, for example, that the double-slit experiment, when done with a single particle emitted at a time, gave results that could be predicted deterministically) would everyone just be completely mystified as to how to explain physics? --superioridad ^(discusión) 05:05, 16 August 2011 (UTC)

Growing catnip

I have got a packet of seed of Nepeta cataria, when and where should I grow it. — Preceding unsigned comment added by 182.178.218.76 (talk) 13:33, 15 August 2011 (UTC)

It is not very demanding, but likes full sun in damp, uncompacted soil. It commonly grows as a weed along ditches and streambanks. Plant in the early spring, as soon as the soil thaws. Or you can start the plants indoors and transplant outdoors in mid-spring. If conditions are right, the plant will continue to grow in the same place for many years. Be careful where you plant it, because catnip can become quite an aggressive and invasive weed. Dominus Vobisdu (talk) 14:24, 15 August 2011 (UTC)

And we should also mention the obvious: Grow it where cats can't get to it, or you will likely find the plant ripped up by the roots and dirt all over the place. StuRat (talk) 17:13, 15 August 2011 (UTC)

can I grow it in the current season ? — Preceding unsigned comment added by 182.178.185.63 (talk) 08:08, 16 August 2011 (UTC)

That depends on what season you're in, winter or summer. Plasmic Physics (talk) 08:31, 16 August 2011 (UTC)

manual

is there a COMPLETE list of army and cia manuals here — Preceding unsigned comment added by Von1235 (talk • contribs) 14:09, 15 August 2011 (UTC)

Would the U.S. Army and CIA interrogation manuals article be of any help? —Akrabbim^talk 14:28, 15 August 2011 (UTC)

We also have Category:Handbooks and manuals and Category:Military training books, if that leads you to any other information you may be looking for. —Akrabbim^talk 14:38, 15 August 2011 (UTC)

There is also Army Knowledge Online (and DKO for the consolidated services; similar resources for other services) but you don't have access unless you are in the Army, (or other branch of the United States armed forces); or, certain types of contractors or liaisons, or other special category. Even if you have access to AKO, it's implausible to expect a complete listing of all manuals for the Army; the institution is huge, and there are lots of subject or domain-specific expertise documents that would be irrelevant to most users. Regarding the CIA, there are lots of resources available online at the CIA website. Most of these manuals will bore the average person to tears. ("Manual for operation of telephone in Ghana Field Office"). What sort of manuals are you looking for? You probably want to start with FM-1, "The United States Army", which you can download free of charge, without needing to log in, from the United States Army website. Then, consider reading FM-3, "Operations." You can buy reprints of these manuals at almost any book retailer. You may find them to be disappointingly dry reading-material. Nimur (talk) 16:57, 15 August 2011 (UTC)

Also, the CIA and US army are constantly revising existing manuals and creating new ones, so maintaining currency on more then a single field would require a major time commitment. Googlemeister (talk) 18:08, 15 August 2011 (UTC)

transformed circuit drawing for all electrical component

please send me the above mentioned subject drawing — Preceding unsigned comment added by 210.212.4.187 (talk) 14:32, 15 August 2011 (UTC)

I don't understand what you are asking for. Looie496 (talk) 16:09, 15 August 2011 (UTC)

I suspect, based on your request, that you found one of our over 3.7 million articles and thought we were affiliated in some way with that subject. Please note that you are at Wikipedia, the free online encyclopedia that anyone can edit, and this page is for asking reference questions about science topics.--Shantavira|^{feed me} 16:20, 15 August 2011 (UTC)

You may find what you want in the article Circuit diagram. Cuddlyable3 (talk) 17:50, 15 August 2011 (UTC)

Human survivability envelope on a newly discovered planet

I am trying to come up with the range of human compatible requirements for colonizing a distant planet or moon. I am thinking of places where humans are not going to need more equipment for survival then is commonly used on earth for long periods (central heating, clothes, sunblock, not SCUBA equipment or radiation suits). So I have thought up a list of things humans would require of a planet and would like to know what ranges people can handle long term (more then 20 years). Critical things to look at would be...

Gravity. Obviously 1g on earth.

There night be a wider range here than you'd think. Probably not more than 1.1 or 1.2 g, but on the low side we might be able to survive quite low gravities, with the proper exercise to save bones and muscles from atrophy. StuRat (talk) 20:05, 15 August 2011 (UTC)

Radiation. Background radiation on earth varies on location, but I think 0-10 miliseverts a year is typical

Oxygen. Earth has 21% O2 at sea level with a standard pressure of about 101 kPa. Human habitation at high altitudes can be down to about 50-60 kPa.

Our article Breathing gas says humans can survive partial O2 pressure of 16-180kPa, but don't know about long term.

Temperature. Humans live in a temperature range with extremes of -100 up to 130 deg F, though we prefer a more mild climate and have special needs at extreme cold. Telling against this is the expensive equipment at Antarctic science bases.

Lack of atmospheric toxins. Mostly concerning volcanic activity.

Obviously humans need water, but how much depends on the environment they are in.

So what kind of ranges for these variables can humans take for the long term? Googlemeister (talk) 18:34, 15 August 2011 (UTC)

Atmospheric pressure is another important parameter. You would also ideally want a planet with a similar day/night cycle to earth. Lack of hostile native lifeforms is a plus! --Goodbye Galaxy (talk) 19:53, 15 August 2011 (UTC)

You should have a good background in Larry Niven's Known Space. One recurring theme of his is the interesting consequences of a space colonization program that send colonist ships to worlds, Jinx, Plateau, We Made It, where robots have found a point habitable to humans. μηδείς (talk) 19:58, 15 August 2011 (UTC)

One other thing to mention is food. If we are to grow our own, we'd need sunlight, around 1% carbon dioxide in the air, and soil with all the necessary minerals and no toxins/poisons (or water with all the necessary minerals, and no toxins or poisons, if we are to grow food there). StuRat (talk)

Adverse airborne bacteria et al.? 16th century explorers might have brought smallpox and others to South America, there could be nasty stuff awaiting us on other worlds as well. --Ouro (blah blah) 07:53, 16 August 2011 (UTC)

1% CO2 seems pretty high if the pressure is what it is on earth. Here we only are around 0.04% CO2 (400ppm). Sunlight would be needed to grow food though unless there is some kind of natural species that survive without it that we could eat. Googlemeister (talk) 20:20, 15 August 2011 (UTC)

Thanks, for the correction. StuRat (talk) 20:31, 15 August 2011 (UTC)

Also, this planet can't have bad weather, like the 1000 mile an hour winds of Jupiter. And there can't be a constant barrage of meteors, as would be common in many new star systems. StuRat (talk) 20:19, 15 August 2011 (UTC)

An ozone layer, or some means of blocking UV light, seems important not just for people but also for any food we grow (plants or animals). StuRat (talk) 20:35, 15 August 2011 (UTC)

Our planet's axial tilt, which gives us seasons, and large moon, which, along with the Sun, gives us tides, are necessary for some plants and animals, but I'd guess we could survive without them. The partially molten core, on the other hand, is important in maintaining a strong magnetic field, which deflects the solar wind enough to allow for a thick atmosphere to remain. StuRat (talk) 20:41, 15 August 2011 (UTC)

How can I get rid of Acetone in my car

A few weeks ago I applied Acetone on my car windshield. The vapors and fumes got so bad that it irritated my body and eyes. I will roll down the windows to air it out but its still there.

I tried almost everything. I even bought a car purifier but that didn't work. Please help me. Does anybody have any helpful suggestions?

It seems like the whole car is infected. How can I get rid of the fumes and vapors of Acetone in my car? — Preceding unsigned comment added by 174.111.55.161 (talk) 20:17, 15 August 2011 (UTC)

Something doesn't make sense here. Acetone is volatile, so should have all evaporated in short order. I suspect that something else must have been mixed with the acetone. Can you check the ingredients list, maybe an odorant was added ? The only other thing I can think of is that the acetone decomposed some of the materials it contacted, and they are now giving off that odor. Does the odor come from the paint, windshield, or where, exactly ? StuRat (talk) 20:24, 15 August 2011 (UTC)

Thanks for your comments StuRat. I didn't read the product before I used it, made a mistake. I threw away the Acetone can. The odor comes mainly from the windshield. — Preceding unsigned comment added by 174.111.55.161 (talk) 20:28, 15 August 2011 (UTC)

Acetone is pretty volatile, so the best strategy is simply to air out the car as much as possible. You're probably also hypersensitve to the smell of acetone since you had a bad experience with it, and you're reacting a bit more strongly than you normally would. That's a normal reaction, and it should wear off soon. Time and air are the best solutions to both problems. Trying to mask the smell would probably make matters worse, and there is nothing that you can use to "absorb" the acetone. Just keep airing it out and not using the car for a few days, and things should return to normal. As StuRat said, there is the possibility that some other ingredient besides acetone is to blame, or that the acetone reacted with the coating on your windshield to produce a noxious product. However, I think that temporary hypersensitivity is the most like reason for your discomfort. Dominus Vobisdu (talk) 20:33, 15 August 2011 (UTC)

(EC) For the record, gasoline will do the same thing if it gets spilled in your car, so keep the gas can in the trunk. For the acetone, don't car windshields have plastic layers in the middle? I know that acetone will react with several different kinds of plastic so if you had a crack or chip in your windshield, acetone could have gotten to the plastic, and reacted with it to form a less volatile, longer lasting odorous compound. The same could happen if it got on other plastics in the car, like the dashboard. Beyond that, the only other things I can think of is to get some fans to blow air through the car while you have it parked to try and remove all the smell you can. Be prepared though, that there is a chance the smell will never fully go away. Googlemeister (talk) 20:38, 15 August 2011 (UTC)

OK, time to list some desperate measures:

1) You could replace the windshield.

2) You could sell the car to somebody with little sense of smell, like a smoker. StuRat (talk) 20:56, 15 August 2011 (UTC)

Or, a little less radical, take it to a body shop and let them bake the car in the oven for a few hours. With the windows down, of course. Dominus Vobisdu (talk) 21:50, 15 August 2011 (UTC)

I wonder if you got some water with a few drops of something like eucalyptus oil or lavender oil and gave the hard surfaces of the inside of the car a good rub down with it.. Might be worth a try. Vespine (talk) 00:53, 16 August 2011 (UTC)

what is the function of the iPhone's 3GS 6R8 coil?

It's this thing that relays power to the LCD display...but I'm curious why this seems to short out first upon water damage (or why coils tend to short out), and why use a coil at all? Is it an inductor? Why would you need an inductor -- surely everything in the circuit board is DC? elle _{vécut heureuse} ^{à jamais} (be free) 22:05, 15 August 2011 (UTC)

Any LCD screen has a backlight to illuminate it. I don't know about in an iPhone, but for laptop LCDs, the backlight is a fluorescent bulb that runs on high-voltage AC current, so maybe the coil is part of a CCFL inverter. Rckrone (talk) 22:45, 15 August 2011 (UTC)

I thought that too but then thought surely all phones these days use LEDs for illumination? However I'm having trouble finding a confirmed source and there are several forums which don't seem to come to a confirmed conclusion as to whether the iPhone uses LED or CCFL backlight. I have found the 6R8 coil for sale on fleabay and it says that it is a part used in the repair of dead or dim backlight, but I'm not 100% sure if that confirms the backlight must be CCFL or that there is some other exotic LED circuit using a coil. . Vespine (talk) 00:47, 16 August 2011 (UTC)

August 16

Relativity and Bernoulli

If I were moving in a car with the window open, and released a piece of paper very close to the open window, which way would the paper move? --Σ _{^talkcontribs} 00:54, 16 August 2011 (UTC)

I don't think relativity is relevant at the speed most of us drive, and I've never seen anything released from a car window move in any direction other than backwards, except when there was a forwards wind of greater velocity than that of the car. How can Bernoulli change this? Dbfirs 01:27, 16 August 2011 (UTC)

Augh, I could've clarified (as I always seem to be unable to do). If I were moving in a car with the window open, and released a piece of paper very close to the open window, would the paper fly outside or stay in the car? Bernoulli states that a fluid moving at high speeds has a lower pressure (or something along those lines), so if I were in the car watching, the paper should fly out, as relatively, the air outside the car is moving faster. But if an observer outside the car were watching the experiment occur, relative to him, the air in the car should be the faster fluid, and the paper should stay in the car. Does the paper leave the car or stay in it? --Σ _{^talkcontribs} 01:34, 16 August 2011 (UTC)

The only thing that matters is the speed of the air on either side of the paper; it has nothing to do with who is observing it. Both the person inside the car and outside the car would note that the speed of the paper is essentially moving the same speed as the air inside of the car, and that the air outside of the car is moving faster than the paper. Bernoilli's principle is about the air speed relative to the two sides of a surface; both observers will arrive at the same result for that relationship. --Jayron32 01:40, 16 August 2011 (UTC)

In my experience, airflows around an open car window are somewhat turbulent, but there tends to be a dominant current of air forcing itself into the car (generally towards the rear of the window), and another forcing itself back out again (generally towards the front of the window). So the short answer is that it will depend whereabouts in the plane of the window you let go of the paper. It'll either fly backwards inside the car, as Dbfirs suggested, or else it will be sucked out. As also noted, relativity has nothing whatsoever to do with it. --Tagishsimon (talk) 01:47, 16 August 2011 (UTC)

I depends on the wind speed and direction relative to the car, the speed of the car, the contour of the car. The contour of the car determines the aerodynamics. Close to the car, a pressure differencial exists pushing the piece of paper outward by a certain amount. The piece of paper has a high surface area to weight ratio, so is majorly affected by air resistance. This means that relative to the ground, both the car and piece of paper will continue forward, although the piece of paper will have a high deceleration, and move outward from the car. Relative to the car, the piece of paper will be moving back, out and down. A wind speed and direction, complicates this. Plasmic Physics (talk) 02:18, 16 August 2011 (UTC)

Although special relativity certainly isn't useful in this problem, I think the OP might be referring to Galilean relativity, which does have some pertinence here. Red Act (talk) 03:01, 16 August 2011 (UTC)

Yes, apologies for misunderstanding the question (it was the early hours of the morning here). I've observed all of the behaviours described above, and turbulent airflow makes it very difficult to predict which one will actually happen at any particular position, but the probability of the paper initially moving outwards increases as you adjust the starting position further from the stationary air (relative to the paper) in the car. To achieve the opposite effect with greater probability, one would need to throw the paper backwards so that it was stationary relative to the outside air, then the faster airflow would be (on average) inside the car. As mentioned above, turbulence makes the actual behaviour very complicated and almost impossible to predict without a very complex computer model. If the paper initially moves out, it very quickly decelerates to approximately the speed of the outside air, then the moving air inside the car can draw it in again because the inside pressure is then lower relative to the paper, by Bernoulli's principle. Has anyone ever recorded the behaviour on a high-speed video camera? It would be interesting to see it in slow-motion. Dbfirs 06:40, 16 August 2011 (UTC)

Strength of Immune System for healthy adult from 2010 versus 1810

Have the medical / hygiene advances made in the last 200 years led to relatively weaker immune systems for modern humans? Would a healthy Londoner from 1810 have a better IDS than his 2010 counterpart? If we sent the 2010 Londoner back to 1810 in our theoretical time machine, would he be in greater peril than if we brought our 1810 guy forward? I'd put my money on the 1810 guy simply because he's healthy is a much worse environment, but he would lack vaccinations... are there scientists who study this sort of "historical immunodefense development"? The Masked Booby (talk) 02:57, 16 August 2011 (UTC)

But we today are descended from people who survived the Spanish flu and polio epidemics of the 20th century. It's not an obvious call. HiLo48 (talk) 08:05, 16 August 2011 (UTC)

@Masked: I'd put my money on the 1810 guy, too, but for completely different reasons. The prevalence of infectious diseases is much, much lower today than it was in urban London in 1810. Smallpox doesn't exist anymore, and polio is virtually wiped out, too. Cholera, typhys, typhoid fever, tuberculosis, and a host of other bacterial and fungal diseases which were once rampant are now a lot less common, so the transfered 1810 individual would have to deal with fewer infections than the transferred 2011 individual. Nutrition nowadays is much better than what it was for the average Londoner 200 years ago. Same with health care, which was little more than beads and rattles compared to modern medicine. The 2011 individual would be placed in a seething brew of noxious microbes with little hope of effective treatment. The only advantages he would have are the fact that he has been inoculated against some microbial diseases, and that he comes from a population which, as HiLo48 has said, represents the survivors of 200 years of epidemics and pandemics. Dominus Vobisdu (talk) 08:24, 16 August 2011 (UTC)

Heat and salty taste perception

I've noticed that French fries and other foods which have a distinct salty taste when fresh and hot lose some of that flavor when allowed to cool (more so when refrigerated than when left at room temperature). Why does this happen? 69.111.78.166 (talk) 03:28, 16 August 2011 (UTC)

Two things:

1. Substances must be soluble to be tasted. Solubility of most solids and liquids increases with increasing temperature; as does the rate at which they dissolve, so hot foods will dissolve more readily in saliva than cold foods, speeding the rate at which your tastebuds will pick them up.
2. Most of what people attribute to taste is actually smell; the nasal passages are connected to the mouth via the pharynx, and lots of your sense of taste is actually picked up by your olfactory sensors in your nose. Vapor pressure is directly related to temperature; so warmer substances form vapors more than colder ones do, meaning that more of the vapor will be detectable, and thus provide more intense flavors than if the food were colder. Note that while salt doesn't readily form a gas, you can "smell" salt because it does form a sort of aerosol whereby tiny particles of salt can become dispersed in the air; and this process is also temperature dependent.

Does that help? --Jayron32 04:09, 16 August 2011 (UTC)

energy and matter

How can energy and matter be equivalent when matter has gravity and energy does not? --DeeperQA (talk) 03:40, 16 August 2011 (UTC)

What makes you think that energy does not exert gravitational attraction? --Jayron32 04:00, 16 August 2011 (UTC)

Oh, and just to correct something you said. Energy and matter are not equivalent. It is energy and mass which are equivalent. See Mass–energy equivalence. Mass is merely one property of matter. --Jayron32 04:01, 16 August 2011 (UTC)

(ec) It's only in Newtonian gravity that energy doesn't contribute to gravity. In general relativity, all forms of energy contribute to gravity. In more technical terms, in the Einstein field equations, all components of the stress–energy tensor contribute to the curvature of spacetime. If you view Newtonian gravity as an approximation to general relativity, by assuming that only mass contributes to gravity, one basically is assuming (among other assumptions) that only the T⁰⁰ component of the stress–energy tensor is non-negligible. Red Act (talk) 04:22, 16 August 2011 (UTC)

Uterine fibroids

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

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

--Jayron32 04:00, 16 August 2011 (UTC)

galactic orbits

Going by the measurements of the spirals of the stars orbiting the center point of a galaxy do the orbits of the stars comply with Kepler's laws of planetary motion and if so can it be determined if the orbits are elliptical? --DeeperQA (talk) 08:48, 16 August 2011 (UTC)

See spiral galaxy. Plasmic Physics (talk) 09:21, 16 August 2011 (UTC)

Kepler's laws are strictly valid only for the two-body problem, where both bodies are point masses. A galaxy is not a point mass but has an extended mass distribution with more or less complex structure. Therefore the laws of planetary motion do not hold for stars in galaxies. In particular, the orbits are not elliptical and they are not even closed, meaning that a star does not return to the same point after one rotation. The rosetta orbit is closer to what the stars do in galaxies. Note that the one place where we can actually observe stellar orbits over full periods is at the Galactic centre and there the orbits are indeed ellipses and comply with Kepler's laws. This is strong indication that the mass in this region is dominated by a point mass, i.e. a central black hole. But this is true only at the very centre, but not in general. --Wrongfilter (talk) 09:52, 16 August 2011 (UTC)

Also see galaxy rotation curve. Gandalf61 (talk) 09:54, 16 August 2011 (UTC)

Dishwashers and salt

If I use the top of the range, all-singing all-dancing diswasher tablets, do I still need to load my dishwasher with salt?

I've never heard of loading a dishwasher with salt. Is that the custom in some places? Where? HiLo48 (talk) 10:36, 16 August 2011 (UTC)

See Dishwasher salt. Per this, you should still add salt to the separate container if you are using those combo tablets, as it is used by the machine's water softener. --Kateshortforbob _talk 10:42, 16 August 2011 (UTC)

I'm still interested in where? Is this an American thing, with Americans assuming that the whole world is just like them? I'm in Australia, a high school teacher teaching kids about salinity right now. No-one in their right mind would think of adding salt to the environment here. And our dishwashers work fine. My dishes come our clean. Are you sure it's necessary? HiLo48 (talk) 10:46, 16 August 2011 (UTC)