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July 23

See-through ?

All of us have heard about a pair of spectacles that can supposedly enable one to see people naked even when they are not naked i.e. see-through their cloths. Do such things exist for real ? Jon Ascton (talk) 01:24, 23 July 2010 (UTC)[reply]

Backscatter X-ray body scanners at airports. J-u-s-t a bit bulkier than spectacles though. Clarityfiend (talk) 01:31, 23 July 2010 (UTC)[reply]

And the other kind, millimeter wave scanner. 213.122.51.122 (talk) 01:38, 23 July 2010 (UTC)[reply]

That's a fairly common joke in the United States. They are not real - and I question how you could think they could be real. About a year ago there was a big thing about modifying digital cameras to allow you to barely see through certain fabrics. I don't know if it was actually real, though. --mboverload @ 01:32, 23 July 2010 (UTC)[reply]

Yeah, mboverload, that rings a bell! Is it right that certain kind of digital cameras can be modified to become "x-ray" ?

I have read about applications for mobile devices that make it possible to see thru the clothes. Even saw a demonstration video of such application. Twilightchill t 03:56, 23 July 2010 (UTC)[reply]

The modification that you asked about involves removing the infrared (IR) filter in a camera. It doesn't really give you X-ray vision, but some fabric that's opaque to visible light is not so opaque to infrared, and a digital camera with the IR filter removed may see through it. ~~I've seen a pretty dramatic demonstration in which a modified camcorder saw through two layers of dark-colored trash bags, as if they were transparent.~~ --98.114.146.237 (talk) 04:36, 23 July 2010 (UTC)[reply]

Oops, my mistake. The dramatic demo I was referring to was actually done using some kind of thermal imager, not a simply modified camcorder. --98.114.146.237 (talk) 04:54, 23 July 2010 (UTC)[reply]

Under the right lighting conditions - and with the IR filter removed from a digital camera (removed...not added!), it is possible to see IR light that is passing through some kinds of thin fabric. It's exceedingly tricky though - and it wouldn't (yet) fit into a pair of spectacles. However, there are many YouTube videos that claim to demonstrate this effect. A camera that's designed to be sensitive to just the right IR frequencies can see "heat" (well, technically, the IR radiation that comes from hot objects) coming from the body through even moderately thick clothing - but because warm air is trapped between clothing and body - you don't see a clear outline of the skin because the difference in temperature between different parts of the body is much greater than the difference between skin and trapped warm air - so you see something through the clothing - but it's not remotely like watching someone who is naked! SteveBaker (talk) 13:14, 23 July 2010 (UTC)[reply]

The night-vision/x-ray trick often requires adding a IR-pass filter, (ie: A filter that looks opaque-black to the naked eye, but is crystal clear to IR) and running the camera in "night vision" mode in bright sunlight.

Some cloth is remarkably transparent to this kind of photography, almost like saran wrap. But that's rare. Most cloth looks about like you would expect.

(The best cloth I've seen to demonstrate this effect is the black cloth covers used in front of certain large (older?) speakers. It's amazing. Looking through the camera you'd swear someone took cloth off your speaker.) APL (talk) 15:25, 23 July 2010 (UTC)[reply]

A cheap webcam with the IR filter removed will make a bottle of Coca-Cola seen transparrent and allow you to see objects placed behind it. Most clothing however is quite opaque to IR. --NJR_ZA (talk) 13:52, 27 July 2010 (UTC)[reply]

Wikipedia has an article on everything. Acroterion _(talk) 04:00, 23 July 2010 (UTC)[reply]

Amazing! The same man invented both X-Ray Specs and Sea-Monkeys. Where oh where is his Nobel Prize? Clarityfiend (talk) 18:22, 23 July 2010 (UTC)[reply]

How does the cut-off frequency in the photoelectric effect support the photon theory of light?

It doesn't really explain in the article photoelectric effect.--115.178.29.142 (talk) 02:55, 23 July 2010 (UTC)[reply]

If light only had wave-like properties, one would expect a gradual drop-off in the effect. The sudden stopping of the effect under a certain frequency indicates that light energy is quantized, rather than continuous, with regards to frequency. If light were just a continuous wave, then as electrons accumlated energy, they would eventually accumulate enough to be knocked free of their orbitals. Higher energy light would remove electrons faster, and lower energy light would remove them slower, but light of any energy should work, since a continuous energy model would imply that the light is able to accumulate on the electrons until they are knocked free. The sudden cut-off below the threshold frequency indicates that it isn't a continuous wave of light which is "energizing" the electrons, rather it is a single particle of light which is energizing a single electron; below the threshold frequency, no single photon has enough energy to excite the electron to leave its orbit. Since this is a particle-like behavior, it confirms the particle nature of light. --Jayron32 03:02, 23 July 2010 (UTC)[reply]

ammonia and baking soda

can u mix ammonia and baking soda ? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 03:32, 23 July 2010 (UTC)[reply]

yes.77.86.76.47 (talk) 03:54, 23 July 2010 (UTC)[reply]

Sure. You can mix anything. Just place them together. I suspect nothing much exciting will happen, as ammonium bicarbonate is just as soluble as sodium bicarbonate, so you'll just get a basic solution with sodium, hydroxide, bicarbonate, and ammonium ions floating around. --Jayron32 03:57, 23 July 2010 (UTC)[reply]

It won't react dangerously; actually the baking soda will neutralize the ammonia to form ammonium carbonate (provided the ammonia is in solution form.) --Chemicalinterest (talk) 11:25, 23 July 2010 (UTC)[reply]

will it form ammonium carbonate as a gas or a solid? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 17:36, 23 July 2010 (UTC)[reply]

Liquid household ammonia (smelly) will react with sodium bicarbonate to form a mostly odorless ammonium carbonate. It is probably dissolved in the liquid. BTW, sodium carbonate is produced too. See ammonium carbonate for more details. --Chemicalinterest (talk) 17:54, 23 July 2010 (UTC)[reply]

isint ammonium carbonate used as smelling salts? how will it be odorless? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 20:58, 23 July 2010 (UTC)[reply]

Hang on , carbonate is much more basic than ammonia, so the reaction above and below doesn't happen:

NH₃ + HCO₃^- >> NH₄⁺ + CO₃^2-
Explanation:
[HCO3-] <> [H+] + [CO3--]   K = 4.8x10^-11 [1]
[NH4+] <> [H+] + [NH3]  K= 5.7x10^-10
So the equiilibrium constant for the reaction:
[HCO3-] + [NH3] <> [NH4+] + [CO3--] is 3.8x10^-11 / 5.7x10^-10 = 0.07

Ammonia solution and sodium hydrogen carbonate combined stays mostly completely as ammonia, sodium ions, and bicarbonate ions. Ammonium carbonate is not produced.

~~Smelling salts is Ammonium chloride~~ Oops, smelling salts are ammonium carbonate, and do smell, but they're not produced by mixing ammonia and bicarbonate of soda . 77.86.82.77 (talk) 21:21, 23 July 2010 (UTC)[reply]

I was just going to correct you. So you are saying that the equilibrium tends to lean toward the bicarbonate and the ammonia rather than the ammonium and the carbonate? --Chemicalinterest (talk) 21:28, 23 July 2010 (UTC)[reply]

Yes.77.86.82.77 (talk) 21:42, 23 July 2010 (UTC)[reply]

0.07 ... that's a pretty significant equilibrium constant actually. And if he uses diethylamine or something ...ooh. John Riemann Soong (talk) 05:52, 24 July 2010 (UTC)[reply]

18 and acne normal?

Is it? --190.178.174.60 (talk) 05:03, 23 July 2010 (UTC)[reply]

We cannot give medical advice. If you have concerns about your acne, you should see a qualified physician, likely a dermatologist. Wikipedia has articles on Adolescence and Acne vulgaris. However, any specific problems you may be having should be discussed with the proper doctor. --Jayron32 05:06, 23 July 2010 (UTC)[reply]

~~Tut, Jayron32. You know this isn't a request for medical advice; it's a request for medical information. 190 is not asking for advice or anything involving a diagnosis.~~ As our Acne vulgaris article states, the condition often lasts into adulthood, often disappearing after the early twenties but sometimes remaining into the thirties or beyond. There are some very effective treatments for it — for which, of course, you need a doctor's advice. Comet Tuttle (talk) 07:01, 23 July 2010 (UTC)[reply]

Of course this is a request for medical advice. Do you really think the OP is asking out of idle curiosity? The OP wants us to diagnose whether they have an underlying condition or if this is just regular teenage acne, which we certainly cannot do. The information you and Jayron have provided should be useful, but if the OP wants anything more specific to their case they need to see a doctor. --Tango (talk) 09:15, 23 July 2010 (UTC)[reply]

The above conversation makes me laugh. To answer the question, it's not abnormal, but still undesired. See a doctor and you can discuss options to clear it up. Regards, --—Cyclonenim | Chat 09:53, 23 July 2010 (UTC)[reply]

You can't know if it is normal or not because you haven't seen it. That is one of the reasons why we don't give medical advice. You don't have anywhere near enough information. --Tango (talk) 11:04, 23 July 2010 (UTC)[reply]

Hm, I see your point. You're probably right; I've stricken my tutting above. Sorry. Comet Tuttle (talk) 17:04, 23 July 2010 (UTC)[reply]

Doh.. Acne vulgaris aka 'teenage acne' is a common disease in teenagers. There are other forms of acne some more servere, others about the same - if you have acne it's a medical condition which a doctor (or possibly pharmacist) can help with.

As the article acne vulgaris says

Acne occurs most commonly during adolescence, affecting more than 96% of teenagers, and often continues into adulthood.

77.86.82.77 (talk) 21:34, 23 July 2010 (UTC)[reply]

smoking and the liver

what is the effect of smoking on the liver? 84.153.200.39 (talk) 09:54, 23 July 2010 (UTC)[reply]

According to Health effects of tobacco#cancer it causes liver cancer. --Chemicalinterest (talk) 11:29, 23 July 2010 (UTC)[reply]

Actually the article just says (uncited) there is "some evidence" that it contributes to "increased risk" of liver cancer. That's a considerably more precise and less straightforward statement than saying it "causes" it. The liver cancer article doesn't mention anything about smoking or tobacco — the primary causes of liver cancer are elsewhere. --Mr.98 (talk) 12:57, 23 July 2010 (UTC)[reply]

As a pure layman here, I'd note that small cell lung carcinoma, which is caused by smoking, is pretty likely to metastasize, and if it does so into the bloodstream then the cancerous cells may end up in the liver, as the liver performs its blood-filtering function, and the smoker ends up with metastasized lung cancer growing in his liver. He's in pretty bad trouble by then anyway. Comet Tuttle (talk) 17:02, 23 July 2010 (UTC)[reply]

but does the liver process nicotine from the blood (and additives) as it does alcohol? Or do other organs (kidneys etc) do that? 85.181.51.2 (talk) 19:22, 23 July 2010 (UTC)[reply]

This site claims that 80% of nicotine is broken down to cotinine by the liver. Comet Tuttle (talk) 04:37, 24 July 2010 (UTC)[reply]

immune system

would the body function better without an immune system, assuming viruses and bacteria etc didn't exist —Preceding unsigned comment added by Catapiie99999 (talk • contribs) 10:18, 23 July 2010 (UTC)[reply]

I think I see where you're going with this, and I guess the answer would be 'yes'. There's a cost involved in having an immune system. Were such a system unnecessary, then organisms could be relieved of its cost. Whether or not that amounts to "better" is a value judgement. --Tagishsimon (talk) 10:22, 23 July 2010 (UTC)[reply]

Except that the immune system doesn't just respond to microbial invasion - it also kills cancerous cells. See cancer immunology. Equisetum (talk | email | contributions) 10:59, 23 July 2010 (UTC)[reply]

...and without bacteria, we'd have no gut flora and be in deep trouble for that reason. When you have to take a large dose of antibiotic, this can kill off a lot of gut flora - causing diarrhoea and all sorts of other unpleasant digestive problems. (Trivia: There are 10 times as many bacteria in your gut than there are human cells in your entire body - and 60% of your poop is dead gut bacteria!) Also, consider that the "Seneca Valley Virus" has been found to kill some kinds of cancer cells vastly more effectively than chemotherapy - and without the associated toxicity.[2] Since we don't yet fully understand the role of viruses - this kind of result suggests the possibility that we'd be unable to survive without them. Over the very long term, periodic additions of viral DNA into our DNA drives evolution - so eliminating them could also cause problems over very long timescales. SteveBaker (talk) 12:55, 23 July 2010 (UTC)[reply]

See Seneca Valley virus-001. -- 110.49.205.195 (talk) 00:27, 25 July 2010 (UTC)[reply]

Bacteria and viruses are not the only things that our immune system protects us from either. There are also fungi and molds that can be harmful to people. Also, without bacteria, the world would be very different because things would not really decay in the manner they do today, so there would probably be dead plants and animals everywhere. Googlemeister (talk) 13:29, 23 July 2010 (UTC)[reply]

Not to mention the fact that without microbes ruminant digestive systems wouldn't function, the nitrogen cycle would be seriously out of whack, and leguminous plants, temperate trees and many corals would have serious problems due to the lack of their respective microbial symbionts (Rhizobium, mycorrhizae and Symbiodinium respectively); but I digress. Equisetum (talk | email | contributions) 13:53, 23 July 2010 (UTC)[reply]

I'm not sure if this is the immune system per se, but if you get a splinter or something your body will often kick it out. I don't know if that's caused by associated infection, though. --Sean 15:52, 23 July 2010 (UTC)[reply]

The real cost of an immune system isn't the energy expenditure or whatever -- that's quite minimal. The adaptive immune system is supported by a ridiculously small number of memory cells. The real cost is autoimmune disease. In fact, I wonder what white blood cells evolved from -- I somehow get the idea that they evolved from a rather maverick predecessor, what with slipping between interstitial spaces and ambushing bacteria hiding in deep tissue. Like a spy movie almost. John Riemann Soong (talk) 16:15, 23 July 2010 (UTC)[reply]

evolution of the mammalian red blood cell

Are there any nonmammalian ancestors whose RBCs lacked nuclei? What was the main advantage of the loss of nuclei -- deformability, speed, or being unable to be infected by viruses? John Riemann Soong (talk) 16:06, 23 July 2010 (UTC)[reply]

Also the amount of oxygen 30 trillion RBCs can carry astounds me. When we run and become out of breath, but not so much that we start running anaerobically, I suspect the limiting factor is not actually oxygen transport, but decreased blood pH and rising CO2 levels. Also what is it that makes your chest feel painful? We don't feel light-headed or dizzy, so we must not use that much oxygen when running, right? John Riemann Soong (talk) 16:11, 23 July 2010 (UTC)[reply]

Paternosters

Are there any paternosters with fewer than six cabins? --84.61.131.18 (talk) 16:38, 23 July 2010 (UTC)[reply]

No idea, but thank you for the question -- I had no idea such a thing as a paternoster ever existed. Looie496 (talk) 17:49, 23 July 2010 (UTC)[reply]

No idea either, but since the number of cabs seems to be equal to, or greater than, two times the number of floors served, you'd be talking about one for only two floors. One wonders what the point would be. Deor (talk) 20:37, 23 July 2010 (UTC)[reply]

entry of gold nanoparticles into the cell nucleus

My boss tells me that when gold particles are tagged with DNA and incubated with cancer cells, over 50% of them can be seen inside the nucleus (versus the 2-10% I've been seeing when they are coated with just carboxylate groups).

Originally I thought the only way for these things to get inside the nucleus was during mitosis when the nuclear membrane dissolved and reformed around some of the particles.

However, my boss says that active transport of gold particles into the nucleus is possible. But it surprises me that it can be done so easily (and statistically favourably) -- since wouldn't cells want to curb the introduction of foreign DNA as a safeguard against viruses? Or is this some mechanism left over from our bacterial days? Previously I thought maybe when the nuclear membrane, DNA-carrying gold simply got "tugged" by the forming nucleus inside the membrane, thinking the DNA was one of its own. John Riemann Soong (talk) 17:27, 23 July 2010 (UTC)[reply]

Custom color urine

What is the mechanism as to how asparagus can your urine green, and beets can turn it red? How can we make artificial compounds such that, when consumed, will produce any color of urine we desire?--70.122.112.145 (talk) 17:33, 23 July 2010 (UTC)[reply]

Several tablespoons of concentrated food coloring? --Chemicalinterest (talk) 18:02, 23 July 2010 (UTC)[reply]

Colored urine means that there is some compound that is not metabolized by the body, but is excreted via the kidneys. Most compounds are metabolized into base elements, but some are not and are excreted unchanged (or are partially metabolized, and the metabolite is excreted). The compound doesn't necessarily have to be colored, but can react with something in the urine to make it colored. What specifically is in beets and asparagus I don't know. Eating too many carrots can cause carotenemia which makes a person orange (the skin). And silver can cause Argyria, which turns skin grey, there is also Chrysiasis from gold the turns skin blue or gray, and lycopenodermia from tomatoes which is deep orange. Presumably there are others, but I don't know them offhand. Ariel. (talk) 20:54, 23 July 2010 (UTC)[reply]

Doan's pain pills (Magnesium salicylate) were at one time treated with an indigetible blue dye (methylene blue, IIRC) which would turn your urine distinctively blue. This was so you'd know when it was safe to take more pills. --Jayron32 04:52, 25 July 2010 (UTC)[reply]

Mg + H2O

Can magnesium burn under water? --Chemicalinterest (talk) 18:02, 23 July 2010 (UTC)[reply]

Yes, it can. However, it is not easy to do. If you burn magnesium and dunk it in water, the water will cool the magnesium and make it stop burning. However, if you put an effort into limiting the cooling effect of the water, you will see that the magnesium will continue to burn. -- kainaw ™ 18:45, 23 July 2010 (UTC)[reply]

Discounting the cooling effect of water, what is the oxidizer under water that is strong enough to burn Mg metal? --Chemicalinterest (talk) 19:08, 23 July 2010 (UTC)[reply]

Could it be the oxygen from the water?? Edison (talk) 20:07, 23 July 2010 (UTC)[reply]

Just the water itself. Even cold magnesium is oxidizing enough to reduce water to hydrogen (and magnesium oxide). The reaction is slow at normal temperatures, but would certainly work if there were already a heat source to get it going. Physchim62 (talk) 20:11, 23 July 2010 (UTC)[reply]

How can an oxidizing agent reduce?. I was wondering about the tightly bound H⁺ ions in water, whether they were the oxidizing agent, but even more reactive metals do not actually burn under water, the H₂ burns above water. --Chemicalinterest (talk) 20:39, 23 July 2010 (UTC)[reply]

As I understand the alkali reduction reaction, the magnesium (or other alkali metal) drags oxygen out of the water to form magnesium oxide, and/or magnesium hydroxide, releasing energy and hydrogen. Hydrogen, plus heat, then undergoes a second ("unrelated") reaction with the free oxygen (O2) in the air, yielding flame (and resulting in water vapor). If this reaction is correct, the flame can't exist underwater - all that will happen is formation of warm water and hydrogen bubbles. I recall performing an experiment in a chemistry lab some years ago (WP:OR) where we used this process to isolate pure H2 (trapping gas under water). Can somebody find a source that says otherwise? The MG + H2O reaction will yield MgO (or Mg(OH)2) + H2 + heat, but no flame; and the H2 will bubble up to the surface (by which time it is probably too cold to ignite). Nimur (talk) 20:47, 23 July 2010 (UTC)[reply]

Isn't it just a redox reaction involving the hydrogen and magnesium? The oxygen is along for the ride (H/Mg exchange on the O in a molecular sense). Lots of metals do this at various rates, sometimes requiring added heat, pH changes, or other initiators to get a noticeable reaction rate. More active metals (potassium) don't require being ignited to cause the reaction. DMacks (talk) 18:00, 24 July 2010 (UTC)[reply]

As pointed out - it does - but the cooling effect of the water tends to halt the reaction. On the other hand the reaction with steam works always (even with no air) - in fact even iron reacts with steam and glows like it is burning. Aluminium reacts even better. I think there are videos on youtube of both of these.83.100.252.126 (talk) 03:58, 25 July 2010 (UTC)[reply]

It should be pointed out that Magnesium does burn readily in both pure carbon dioxide and pure nitrogen (forming Magnesium Carbonate and Magnesium Nitride, respectively). It's one of the rare substances that does. You can look up YouTube videos or Magnesium burning in Dry Ice; its quite cool. I've seen it live in person, and its always interesting. If it were molten magnesium, it may react readily with water. Molten iron will react with water to form iron oxide/iron hydroxide, and liberate hydrogen gas. --Jayron32 04:40, 25 July 2010 (UTC)[reply]

heat and rain

What is the highest recorded temperature on earth while it is raining? Googlemeister (talk) 19:29, 23 July 2010 (UTC)[reply]

My guess would be 100F. --Chemicalinterest (talk) 19:34, 23 July 2010 (UTC)[reply]

Why? Vimescarrot (talk) 19:46, 23 July 2010 (UTC)[reply]

I suspect the highest temperature would be even higher than 100 degrees; if a storm is triggered by a cold front displacing a warm front with thermal inversion in the fronts, then the temperature at ground level as the rain began would be just as hot as it was before the rain arrived. I guarantee you that even somewhere with relatively pedestrian weather like New York City will have had the occasional 100+ degree day that suddenly turned into a thunderstorm, and during the early part of the storm, it would measure above 100 degrees. —ShadowRanger ^(talk|stalk) 20:29, 23 July 2010 (UTC)[reply]

It can easily be way above 100 when the rain starts, but it won't stay that way for long. Note that if the rain water itself was above 100, you could easily get heatstroke from being out in it, because your body would have no effective way to cool itself. Rain water in fact never gets anywhere close to that hot. Looie496 (talk) 20:53, 23 July 2010 (UTC)[reply]

You would only have heatstroke if you were out in it for a significant amount of time. Your average hottub water can easily be 105F, and you people are often in that water up to their neck. Googlemeister (talk) 21:01, 23 July 2010 (UTC)[reply]

The temperature can be hotter than 100F during thunderstorms around the start of the monsoon season in the Indian subcontinent, the Sahel and parts of the Middle East and even in Southern China. ~A H 1^(TCU) 22:57, 23 July 2010 (UTC)[reply]

What do you retain from textbooks read years ago?

I've read a lot of textbooks in my time, I still do. If you do not recall the contents word for word, then what is the form of the knowledge that gets imprinted in your memory? How do words on the page get transformed into knowledge (which you may not even remember from which textbook or lecture it comes from) which you may make use of many years later? Do even books read ten years ago leave a trace on the brain? 92.15.3.219 (talk) 19:32, 23 July 2010 (UTC)[reply]

You probably still know your basic math and English skills. --Chemicalinterest (talk) 19:36, 23 July 2010 (UTC)[reply]

Psychologists have distinguished between "Semantic memory," which is things you maintain as part of your general knowledge, without linking it to a particular book, lecture, TV documentary, or life experience, versus "Episodic memory," which is in fact linked to such a specific source. Certainly we may remember in some cases a particular textbook, lesson, encyclopedia article, TV documentary or personal explanation whereby we learned a particular nugget of knowledge. Edison (talk) 20:06, 23 July 2010 (UTC)[reply]

This is merely an anecdote, but I was recently asked a question about a particular part of history. I could recall the exact layout of the page it was on in my high school textbook, but could not for my life remember what the sentences actually said. ?EVAUNIT^{神になった人間} 06:44, 24 July 2010 (UTC)[reply]

Yes, I have a similar peculiarity of memory in that I can often remember where on a page I read the information, but I cannot read the page. People with true photographic memory can (disputed claim). Most of your knowledge, however, is a synthesis of what you have read - processed by your brain to become understanding and recalled in a different form. Dbfirs 07:24, 25 July 2010 (UTC)[reply]

Katana

Would it be feasible to block bullets with a katana, or even slice them in half? (With enough training, of course.) --138.110.206.99 (talk) 19:46, 23 July 2010 (UTC)[reply]

I suppose it might be theoretically possible, if the bullet was extremely soft lead, and you basically fired the bullet at the edge of the katana. But no, no matter how much training you have, you can't move a sword fast enough or precisely enough to get it in the way of a bullet moving at several times the speed of sound. You might be able to move the sword into the path of the gun while someone was aiming (extremely difficult, but possible), but if they adjust the angle of the shot by fractions of a degree, your sword will be out of place, and human reaction times aren't fast enough to correct. And of course, even if they don't change their aim intentionally, the slight changes in angle triggered by the force they exert pulling the trigger, the recoil, etc., all combine to make it effectively impossible. —ShadowRanger ^(talk|stalk) 20:09, 23 July 2010 (UTC)[reply]

I should point out that this would depend greatly on the structural integrity of the katana, and even a good katana would probably be irreparably damaged. A lot of things marketed as katanas are just plain stainless steel; hard, but brittle, and would likely shatter if hit by a bullet. Traditional katanas have more flexibility, but the edge is still hardened steel and would suffer badly. —ShadowRanger ^(talk|stalk) 20:15, 23 July 2010 (UTC)[reply]

Here is some video of shooting a sword edge-on in laboratory conditions, and here is a guy who tried it in the real world. An important thing to consider is that you can't see bullets. For fun, take the fastest a human can move a limb (the fastest baseball pitch is probably close), the speed of a .22 bullet, and the width of your body you want to protect and see how far away you'd have to see the bullet to get your hand to the right place in time. --Sean 20:19, 23 July 2010 (UTC)[reply]

All I have to say is: Awesome links. —ShadowRanger ^(talk|stalk) 20:25, 23 July 2010 (UTC)[reply]

I don't understand japanese - was that a copper, lead, plastic or tungsten bullet? They're all different aren't they? 77.86.82.77 (talk) 20:55, 23 July 2010 (UTC)[reply]

Its just a name; see katana for details. The OP was probably asking about a normal bullet. --Chemicalinterest (talk) 20:58, 23 July 2010 (UTC)[reply]

I meant in the video linked above - what was the bullet made of?77.86.82.77 (talk) 21:43, 23 July 2010 (UTC)[reply]

So if the Japanese guy had Superman quality reflexes and held the sword in front of him just so, it would have split the bullet into two pieces which would each have hit him. Two small wounds instead of one big one, and less kinetic energy due to what was absorbed by the sword. A possible improvement. Holding an iron skillet, an anvil a sadiron or a manhole cover between oneself and the shooter might be preferable. Edison (talk) 01:35, 24 July 2010 (UTC)[reply]

In the video, it was indicated the bullet was made of lead. --Kusunose 04:42, 24 July 2010 (UTC)[reply]

How hot is it really?

The meteorologists are telling us it will be 96 degrees F (36 C) with heat indexes over 100 F (38 C) today in North Carolina. What they almost never tell us is that this is totally unrelated to being out in the sun. How much hotter would it be out in the sun, and would the heat indexes also have an effect on that?Vchimpanzee · talk · contributions · 19:53, 23 July 2010 (UTC)[reply]

Where do you live? I have very similar temperatures here in New Jersey. --Chemicalinterest (talk) 20:41, 23 July 2010 (UTC)[reply]

I updated my original question.Vchimpanzee · talk · contributions · 20:50, 23 July 2010 (UTC)[reply]

I think the heat index is just taking into account the humidity; the sun would be determined by several more factors, such as the color of your clothes, how much you sweat, how much wind there is, how much shade you are in, how much exertion you do, how you are positioned in relation to the sun, etc. --Chemicalinterest (talk) 20:56, 23 July 2010 (UTC)[reply]

I knew that, but in general, if someone is out in the sun, does anyone know how much hotter that makes it?Vchimpanzee · talk · contributions · 20:59, 23 July 2010 (UTC)[reply]

It's so variable that there's no point in trying to say anything. Did you ever see one of those pictures of somebody frying an egg on a hot sunny sidewalk? Looie496 (talk) 21:02, 23 July 2010 (UTC)[reply]

Surface temperatures are measured in the shade because the thermometers would give inaccurate readings in the sunlight. For example, the air temperature (often measured in Stevenson screens, which can still have an error of a few degrees) could be 35°C but the thermometer under intense sunlight could read 45°C or even 50°C. ~A H 1^(TCU) 22:28, 23 July 2010 (UTC)[reply]

It's impossible to say anything about the temperature "in the sun" in general. The difference in air temperature between sun and shade is negligible, since convective and turbulent movements of the air will quickly equalize any temperature gradient. However, when you place a thermometer in the sun, it invariably spikes by several, if not dozens of degrees. Why is this?

It's because an opaque object such as a thermometer or your skin will absorb certain wavelengths of light from the sun; this will heat the surface of a thermometer or your skin by some significant amount. Because this varies strongly among different objects made of different materials and of different colors, it's impossible to make a general statement about how hot it is "in the sun". I suspect the color of your skin greatly affects how hot your skin actually gets. Would certainly make for a good science project! (with the proper sunscreen, of course :D) -RunningOnBrains^(talk) 05:17, 24 July 2010 (UTC)[reply]

add that the body is a self-regulating temperature system, so the effects of direct sunlight on the body change the perception of temperature without actually changing the surface temperature of your body significantly. It's much like watching ice melt: ice melts faster when the temperature is hotter, but the surface temperature of the ice (by definition) never strays far from 32° Fahrenheit during the entire melting process. --Ludwigs2 06:10, 24 July 2010 (UTC)[reply]

This article - and the articles that it links to - may answer your question: Apparent temperature. Mitch Ames (talk) 09:10, 24 July 2010 (UTC)[reply]

peppers

what is inside of a pepper, a gas or air? and how does it get in their?--Horseluv10 20:40, 23 July 2010 (UTC) —Preceding unsigned comment added by Horseluv10 (talk • contribs)

Pepper skins are not airtight. The gas inside wouldn't be 100% ordinary atmosphere, but it would be pretty close. (Small differences in CO2 concentration, presence of a bit of ethylene, higher concentration of water vapor, etc.) Looie496 (talk) 20:48, 23 July 2010 (UTC)[reply]

that's a really smart question. 92.230.65.204 (talk) 20:55, 23 July 2010 (UTC)[reply]

What's smart? That air is a gas already? :o --Chemicalinterest (talk) 20:59, 23 July 2010 (UTC)[reply]

I think it is a pretty good question. What's surprising to me is that the inside is neither solid nor liquid. Why did the pepper even bother to grow larger than necessary to actually deploy its seeds? Does the air-space somehow improve the seeds' chance of growing, does it serve some other evolutionary purpose, or is it just a vestigial artifact of the way that pepper biology forms its plant-tissue structure? Nimur (talk) 21:45, 23 July 2010 (UTC)[reply]

It is hard to explain something like that by random change... Oh no... Not another fight --Chemicalinterest (talk) 21:59, 23 July 2010 (UTC)[reply]

The point being, it's probably cultivated that way. Artificial selection, as opposed to natural selection. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:00, 23 July 2010 (UTC)[reply]

The bell pepper is a member of the Solanaceae family, also known as the nightshades. Another member of that family is the tomato. If you imagine a tomato with all the parenchyma-y goop inside gone, you've got something not unlike a pepper. Check this picture for a visual comparison. And given the variety of tomatoes (beefsteak, cherry, plum etc) no doubt a lot of cultivation has gone on for peppers too, like Bugs has said. Brammers (talk/c) 07:59, 24 July 2010 (UTC)[reply]

This homework sheet provides a possible rationalisation of the large size of peppers, although it doesn't give any sources so handle with care. Brammers (talk/c) 08:02, 24 July 2010 (UTC)[reply]

(EC) It seems most likely to me the size & shape of the fruiting body relates to it's purpose, to attract birds. (The same is believed for the colour after all, as it is for most brightly colour fruits.) To put it a different way, to claim that it's larger then necessary to actually deploy its seeds is most likely wrong, it isn't anymore then a watermelon is. The fact that there's no liquid or solid inside likely arises somewhat from the evolutionary history and also the fact it isn't needed as the external skin already provides enough for the birds that eat it. After EC: Of course as BB has mentioned we also need to distinguish from completely naturally occuring chillis and those that have been cultivated at some stage in their hisotry, which can be rather difficult for something which has been cultivated as long as chillis have... Nil Einne (talk) 22:02, 23 July 2010 (UTC)[reply]

? Do wild, non-cultivated peppers have the air gap ? 77.86.82.77 (talk) 22:15, 23 July 2010 (UTC)[reply]

I would expect some although I have my doubts we'd see the very large sort of things like some modern capsicum for example. These [3] [4] [5] have some discussion of wild capsicum including some pictures. Bear in mind as I mentioned above determing if something has been influenced by cultivated varieties is usually rather difficult even with genetic analysis. In this case the refs all suggest the history has not even been well studied anyway. Nil Einne (talk) 22:33, 23 July 2010 (UTC)[reply]

"Locular gas composition pepper" seems a reasonable search and produces this [6] which might have the answer, but I can't read it..83.100.252.126 (talk) 22:45, 23 July 2010 (UTC)[reply]

How did dinosaurs mate?

Those big tails would have been hard for the females to curl out of the way, and their multi-ton weights would have made problems for the male mounting (especially in cases like the brontosaurus and brachiosaurus). The little forearms of the tyrannosaurus would have made it hard for the females to get down on her "elbows" and for the males to "hold on". And in the case of the stegosaurus, well, between the weight, the spines, and the big tails, they pretty much hit the anti-mating trifecta. 71.161.45.103 (talk) 22:49, 23 July 2010 (UTC)[reply]

Short answer: although we can draw inferences from the strategies of various modern reptiles and from birds (which technically are dinosaurs), we don't really know; for example, soft tissues like penises are almost never preserved by fossilisation, and although it's commonly assumed that (male) dinosaurs didn't have them, some of them may have (just as some modern birds do and some don't).

The question is addressed in more detail by some professional biologists and palaeontologists here, on the 'Ask a Biologist' website. 87.81.230.195 (talk) 23:20, 23 July 2010 (UTC)[reply]

Interesting article here : The Straight Dope : How did Dinosaurs Have Sex? APL (talk) 06:19, 24 July 2010 (UTC)[reply]

I believe some broken bones in dinosaur tails are ascribed to the problems they had mating. They obviously went n for S&M :) Dmcq (talk) 14:14, 24 July 2010 (UTC)[reply]

Is it bad that the first thing I thought of was this? so nia^♫♪ 14:33, 24 July 2010 (UTC)[reply]

That would depend on the flavour of the jello. 87.81.230.195 (talk) 14:40, 24 July 2010 (UTC)[reply]

Mating under water would obviate the weight issue. Cuddlyable3 (talk) 15:59, 24 July 2010 (UTC)[reply]

Dinos did not live in water, so mating there would be odd. If you are thinking about Ichthyosaurs or Plesiosaurs, those are not dinosaurs; if you are thinking about Sauropoda, know that those are old ideas of them living in water. QFL 24-7 ^{bla bla bla ¤ cntrb ¤ kids ¤ pics} 21:39, 24 July 2010 (UTC)[reply]

Many of the larger sauropods are believed to have lived much of their lives in or near water, even though they didn't swim. Their enormous size is believed to have made living on dry land difficult. This is not settled theory; there are others that claim that their structure would have made breathing and maneuvering in the water difficult. But there are some credible theories that some of the largest dinosaurs did live a partially aquatic lifestyle. Also, be careful asking "how did dinosaurs mate". Its like asking "how do mammals mate". Dinosauria was a massive, diverse clade which existed for hundreds of millions of years (and still does, in the form of birds). There was likely a huge diversity in the manner in which dinosaurs mated, considering they ranged in size from the perhaps 60-meter long Amphicoelias to some that were only a meter or smaller. They were two-legged or four-legged, and came in two very different types of hip configurations (Ornithischia and Saurischia). Making definitive statements over how such a diverse group of animals may have behaved is practically impossible. --Jayron32 04:32, 25 July 2010 (UTC)[reply]

Check here and corresponding link... the "in or near water" is old ideas that have been refuted as much as the lumbering, small-brained, cold blooded side of Dino lure. QFL 24-7 ^{bla bla bla ¤ cntrb ¤ kids ¤ pics} 04:48, 25 July 2010 (UTC)[reply]

Hmm, they're still small-brained, aren't they?--91.148.159.4 (talk) 22:02, 26 July 2010 (UTC)[reply]