Wikipedia:Reference desk/Archives/Science/2006 October 14

Humanities Science Mathematics Computing/IT Language Miscellaneous Archives

The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions at one of the pages linked to above.

Space Shuttle: burn-up.....

Why doesn`t the Space Shuttle burn-up during it`s ascent?....The protective tiles aren`t in the line of "flight"? Also,,,ty for "answers" to Ballistics. 152.163.100.74 02:09, 14 October 2006 (UTC)

First off, it's not going very fast on the way up, at least where the atmosphere is dense. Also, it's oriented to minimize air resistance, unlike its descent, when it's aligned to maximize it in order to lose speed. Clarityfiend 02:40, 14 October 2006 (UTC)

If the same thrust was applied for decelaration on the way down as is needed for acceleration the way up, the shuttle would have comparable speeds at the same air densities and not get very hot. However, that would require carrying an awful lot of extra fuel – doubling the amount and then more because the extra fuel needed for later slow down must also first be brought up. So that is why air braking is used. See also our article Space Shuttle, in particular the section on Landing.  --Lambiam^Talk 08:25, 14 October 2006 (UTC)

The above has pretty much covered it, recently I read that the shuttle DOES in fact get quite hot on the ascent. The shuttle starts at a stand still and accelerates through an atmosphere that gets thinner as it gets higher so it doesn't get as hot as when it starts fast and falls into an atmosphere that gets thicker as it descends. But it's definitely included in the design. Vespine 04:44, 16 October 2006 (UTC)

Planetary rings

In our own star system, rings are only found around gas giants; is this just a coincidence, or are gas giants more prone and/or rocky planets less prone to having rings? Furthermore, could a habitable planet have a ring system? CameoAppearance ^orate 02:23, 14 October 2006 (UTC)

The gas giants have rings because they're more massive. Rings are created when space debris is ripped apart by the planet's gravity. Also, I see no reason why a habitable planet can't have a ring system (or why a planet with rings can't be habitable). --Bowlhover 02:48, 14 October 2006 (UTC)

I believe being torn between two gravitational sources, like the planet and another moon, is what typically breaks up a moon into a ring (or prevents a ring from forming a moon). StuRat 14:50, 14 October 2006 (UTC)

The solar wind is probably a major factor. According to the article, it's believed to be strong enough to have stripped Mars of a third of its atmosphere. Something as fragile as a ring wouldn't have been able to survive too close to a star. Clarityfiend 04:33, 14 October 2006 (UTC)

I would say the rings are less easy to blow away than the atmosphere, being composed of much larger particles and rocks. Therefore, the solar wind should have little effect on rings. StuRat 14:43, 14 October 2006 (UTC)

Hmmm...after further consideration, I declare myself a solar windbag. Clarityfiend 16:27, 14 October 2006 (UTC)

Two quotes from our article Planetary ring: "Pluto is not known to have any ring systems. However, some astronomers think that the New Horizons probe might find a ring system when it visits in 2015." "It is also felt that Phobos, a moon of Mars, will break up and form into a planetary ring in about 50 million years due to its low orbit." So astronomers even consider dwarf planets to be potential ring bearers.  --Lambiam^Talk 08:10, 14 October 2006 (UTC)

One theory about the formation of Earth's Moon (and the most popular one, I believe) is that it formed out of the debris left over from a collision, which first formed a ring and then the rocks in that ring pulled togeether to form the Moon. Of course, that ring was temporary, but what isn't? As a sidenote, the biggest gas giant with a ring in our solar system is the Sun itself, with the ring being the asteroid belt. Or is that essentially differnt? DirkvdM 09:33, 14 October 2006 (UTC)

Earth's Moon formed out of the debris left over from a huge collision between earth and another very large object. Also, you could say that all the suns orbiting bodies including the planets form a big ring. --Light current 11:35, 14 October 2006 (UTC)

The "huge collision" that you guys refer to is known as the Giant impact hypothesis. Since the Sun is essentially an immense gas giant, it follows the current "only gas giants have rings" trend. -- Plutor ^talk 15:36, 14 October 2006 (UTC)

stadium construction

What will be the approximate cost of construction of International Cricket stadium in terms of no. of spectators

It will depend on factors like location and size of the cricket pitch. Location would be extremely complicated since it will affect the cost of labour, local laws and legal requirements, cost of land etc Nil Einne 14:06, 14 October 2006 (UTC)

The cost in terms of number of specatators? What, is it supposed to collapse or something? DirkvdM 08:23, 15 October 2006 (UTC)

A cold

What is the best way to get yourself feeling fit enough to go out when you have a chest cold? No time for doctors-- I need to go out tonite!--Light current 10:53, 14 October 2006 (UTC)

Lots and lots of fluids (water, not soda), warm chicken soup, tea with honey, cough pastils in case you are feeling it in your throat. Refresh the air in the rooms you are in by opening the windows wide for a small amount of time, which is the way which works. Cup of hot chocolate, Calvin and Hobbes and a sofa, blanket, pillow and a scarf for safety does it for me. "Does it for me" doesn't mean it clears out the cold, it means that it makes me feel superb. 81.93.102.3 11:23, 14 October 2006 (UTC)

I take it "cough pastils" is Britspeak for cough drops ? If so, I recommend eucalyptus. Beware, though, that too many make your jaw fall asleep. StuRat 14:02, 14 October 2006 (UTC)

What about sleep?--Light current 11:35, 14 October 2006 (UTC)

You said you had no time for sleep! Over the years, with myself and the kiddies, I found that the standard approach works best: lots of sleep, fluids, and ibuprofen. The 'other' approach of ignoring the cold, taking symptom-reducers, and partying all night, has consequences. With a chest cold, the most likely effect is that it develops into pneumonia, which is a bitch. --Zeizmic 11:44, 14 October 2006 (UTC)

No, usually sleep has no time for me. Insomnia. However, when feeling completly shattered with a cold I can sometimes sleep as I have been doing the past 15? hours on and off. Feeling better now. I will be venturing out after food. THe cold has now mainly progressed to the head and is not as painful. Any advice on dealing with that one? 8-? --Light current 18:10, 14 October 2006 (UTC)

Take a large heat-resistant bowl or dish, fill it with 10cm (a couple of inches) of boiling water, add 1 to 5mL (a teaspoon) of eucalyptus oil, place your face over the steaming water, place a towel over head and bowl to trap the steam, breathe deeply in through your gurgling nose and out through your mouth. Expect to cough, expect to feel very refreshed afterwards. You can get eucalyptus oil where you are can't you? Sorry I'm a bit late for the tonight that passed a few days ago, but perhaps it's of use to someone somewhen. 203.22.236.14 10:36, 18 October 2006 (UTC)

Not too late. Ive still got a bunged up head. Im wondering if inhilation of Olbas oil in hot water would work. I have some of that. 8-(--Light current 13:54, 18 October 2006 (UTC)

Boiler Efficiency

I have read before that boilers produce waste steam as it functions as a HEAT SINK. So can we install economisers to extract heat from the steam in the heat sink and return that heat to main boilers,such that the temp of condensed water in the heat sink is slightly higher than surrouding areas, resulting in higher efficiency??

You should sign your name, so we can see if boiler questions exceed seagull-time. Boilers are really old and perfected technology. Any further attempt to squeeze more out of them has consequences. Also, boilers are under a raft of laws, ever since they used to blow up a lot in the early 1900's. --Zeizmic 11:49, 14 October 2006 (UTC)

They may be old but they are used everywhere( nuke power plants, submarines,ships)

do-it-yourself X-ray Crystallography?

What's the best way to build a homemade rig for getting Crystallographic data? Made out of household materials?172.149.83.128 13:28, 14 October 2006 (UTC)

Divine intervention? N.B. It depends on your crystal quality and what data quality you wished to obtain as well as which method you plan to use to solve the phase problem. However your best bet would be to use a synchrotron and therefore you'd need several kilometres of tunnelling for starters. With very good quality crystals 2 Ångströms resolution should be possible! Nil Einne 13:38, 14 October 2006 (UTC)

A basic x-ray crystallography machine sits on a table top and certainly doesn't require kilometers of tunnels. Rmhermen 21:38, 14 October 2006 (UTC)

No but that crap isn't going to give you the resolutions and quality you need to get published in Nature or Science :-P Plus what do you do if you have a small or weakly diffracting protein? Nil Einne 14:59, 15 October 2006 (UTC)

Your project sounds quite ambition but I could imagine that Debye-Scherer scattering may be in the reach of a skilled amateur. Maybe you want to read up on that subject. However, even for this, you need an X-ray tube, and if you manage to obtain one, remember that X rays arehazardous and potentially fatal. And they kill silently. Make sure you know enough about radiation safety to avoid endangering you or others before you even think about fooling around with such dangerous stuff. Simon A. 15:37, 14 October 2006 (UTC)

Isnt there some hazard to be aware of regarding X Ray reflection from certain surfaces?--Light current 18:13, 14 October 2006 (UTC)

homemade NMR?

What's the most effective way to build your own NMR probe out of old household electronics?172.149.83.128 13:29, 14 October 2006 (UTC)

The first thing you need is a very powerful electromagnet. To test if your electromagnet is powerful enough, I suggest you obtain a tank full of toxic gas, say hydrogen cyanide gas. Bring this to within say 6 metres of your electromagnet and turn it on. If you are still alive, you need a more powerful magnet. Hope this helps! Nil Einne 13:43, 14 October 2006 (UTC)

What he is trying to say is that the magnet needed for magnetic resonance must be huge; the smallest MRI scanner uses 0.3 Tesla magnets, which is about a thousand times the magnetic flux density of a powerful horseshoe magnet. Plus, in order to make it even slightly practical, you'd need to cool it with a liquid gas (nitrogen is most commonly used, I think). I'm not sure about making a probe with MRI. The magnet might be a bit less powerful, but it would still be absolutely massive, and probably therefore a superconducting magnet, and in order to make it shrinkable to probe size, would need a phenomenal cooling system. Laïka 14:10, 14 October 2006 (UTC)

Yes. Bringing a metal object anywhere near to a magnet used for MRI or NMR when it's on will likely result in the object being drawn to the magnet at fairly considerable force. Although I'm not sure whether the tank would actually break, possibly not AFAIK most oxygen tank incidents the tank doesn't break (but has killed by force) although with hydrogen cynide all you would need would be a minor leak and... It probably would have been better to recommend the guy wear several chains. Or perhaps put something put several knives on a table and then stand between the table and the magnet. BTW this link may be of interest to some [1] Nil Einne 14:38, 14 October 2006 (UTC)

Its a good question, so lets try this again...(yeah, yeah, yeah it uses a strong magnet....) What's the most effective way to build your own NMR probe out of old household electronics?

mass spectrometer?

What would you need to build a Mass spectrometer from junk sitting around the house?172.149.83.128 13:31, 14 October 2006 (UTC)

Again divine intervention might be helpful. Failing that, I don't suppose you happen to have a million dollars in cash lying around? This junk should give you a decent spectrometer. Nil Einne 13:46, 14 October 2006 (UTC)

But Nil, come on, don't discourage our young optimistic DIY enthusiast-troll unnecessaily. I'm sure you can get a simple second-hand beginner's synchrotron for less than $100,000, plus shipping, handling and installation. Simon A. 15:43, 14 October 2006 (UTC)

Mass specs are nowhere near that expensive. You can pick a basic one used for less than $10,000 and it doesn't require any supercooling or superconducting wires. Rmhermen 21:35, 14 October 2006 (UTC)

Oh sorry, I though we were still talking about synchrotrons. Actually, Froogle in fact lists suppliers for mass spectrometers, starting at US$500. Simon A. 08:59, 15 October 2006 (UTC)

And before Rmhermen corrects me on that, too: I know that one can build synchrotrons without superconducting magnets, but it's simply less cool to do so. Simon A. 09:00, 15 October 2006 (UTC)

Well it depends on what kind of mass spectrometry you want. I would suggest you start off with a fourier transform ion cyclotron mass spectrometer. You'd probably want a few different types but really for bio research nowadays you shouldn't leave home without a FTIC-MS (except that you're doing it at home so I guess you just should leave home and when you do leave home you probably shouldn't take it with you). BTW $100k for a synchrotron, are you joking? Try reading the synchrotron article... The smallest synchrotron I know (I don't know many) is Singapore's 0.7 GeV and I don't know how much it cost but I'm pretty sure it would have been in the millions [2]. But a protein crystallographer is going to want something like the 3.0 GeV Australian synchrotron [3] ([4]). To be fair, you're not going to need so many beamlines if you only want to do X-ray crystalography but if you've got the synchrotron why waste it? Nil Einne 15:30, 15 October 2006 (UTC)

RadioShack?

Does radioshack sell coils of super conducting wire?172.149.83.128 13:35, 14 October 2006 (UTC)

Very good news... Yes they do! Unfortunately they don't happen to sell the equipment you need for the near absolute zero temperatures for the wires to show superconductivity Nil Einne 13:49, 14 October 2006 (UTC)

Before you go and sink hundreds into gold-plated solidified-hydroxyl acid audio cables or whatever, you should read High-end audio cables. Basically, the quality of the cabling has no bearing on the sound quality, as the frequency of a wave being transmitted down the cable will be unaffected by any impurities found. You might hear a slight increase in volume from the cables, due a reduced resistance, but the effect is apparantly mainly synesthetic. Laïka 15:33, 14 October 2006 (UTC)

I'm afraid that you missed that the OP is going to build a synchrotron, mass spectrometer, or NMR apparatus in his backyard. Given that for all three of them, an extraordinary powerful magnet is the crucial part, having superconduvting wires is indeed the way to go. Now, there is the funny paradox that the best normal conductors such as gold do not get superconducting at all or only at ridiculously low temperature and even lower magnetic fields, while mediocre conductors get superconducting above liquid helium temperature. Hence, the classic is lead, and a niobium-tin-alloy is the state of the art. However, you cannot exactly buy this brittle stuff as wire. But we are all waiting for the obvious next qestion: Where do I get a cheap supply of liquid helium? Simon A. 15:58, 14 October 2006 (UTC)

Lead isn't brittle, it's relatively soft. StuRat 18:57, 14 October 2006 (UTC)

I know, but I was taling about the NbSn alloy. Simon A. 09:02, 15 October 2006 (UTC)

Isn't gold never a superconductor (as silver and I assume iron and steel since their ferromagnetic)? At least this is what the article says. Normal copper is not a good superconductor either because of impurities. Aluminium and tin are supposed to be superconductors however and from Google you can buy aluminium wire from radioshack. The tin or aluminium shield in coax wire should do too I guess... Alternatively how about solder? Sounds like it should be a superconductor (although don't know what temperature). In any case, I'm fairly sure you should be able to obtain a superconductor from radioshack as I mentioned (of course obtaining the equipement for the temperatures required is a different matter) Nil Einne 14:56, 15 October 2006 (UTC)

Isn't gold never a superconductor is right! Aluminium and tin? What? Since when did this happen? — X [Mac Davis] (SUPERDESK|Help me improve)07:44, 17 October 2006 (UTC)

synchrotron?

1) Can you buy a synchrotron on ebay? 2) Where would you keep it?--172.149.83.128 13:36, 14 October 2006 (UTC)

I happen to have a spare synchrotron lying around! I would list it on ebay except I think their system might crash with the success fee. In any case, given the extremely large success fee, how about we just negotiate and out of auction trade? I might be willing to part with mine for say NZ$500 million? It'll be best if you pick up (and yes I do accept cash on pickup although we'll have to visit the bank first). However if this is not possible for you, unfortunately it's a bit large to be couriered but I might be able to deliver it myself. Just add another say NZ$500 million and we have a deal. Of course, I do expect your payment before I arrange delivery. BTW, I do assume you already have the necessary space? As mentioned above you will need a lot of underground tunnelling. Just make sure you have say 50km and we're sweet! P.S. No PayPal or Western Union or escrow please. Again I don't want to crash their systems. P.P.S. The above IP address looks up to AOL. Explains some things I guess... Nil Einne 13:56, 14 October 2006 (UTC)

Maybe this has something to do with eBay's sponsored links on Google; among the amazing things eBay apparently sells are Photons and Plutonium, while Amazon is offering Angular Momentum. No sign of an eBay sponsored link for Synchrotrons, but there is an Amazon one [5]. Laïka 14:18, 14 October 2006 (UTC)

I wouldn't mind selling photons. I wonder what the starting bid should be? Maybe I could sell angular momentum as well but not so sure where I could get plutonium from... Nil Einne 14:43, 14 October 2006 (UTC)

I don't think these things would ship well... --Zeizmic 15:01, 14 October 2006 (UTC)

I can't help thinking the guy who talks about "An alternative to the $16 Photons" got a bit ripped off; the sun provides about 10²¹ of photons per sqaure metre a second for free. Paying $16 for each would bankrupt the entire planet in something like 1 E-24 s! Laïka 15:16, 14 October 2006 (UTC)

Well for the photos I just ship the maker. I mean if you were buying a er, motherboard, which one will you prefer. One motherboard or a device which produces motherboards? I'll go with the production device any day. Same thing with the photons... Alternatively, I could make the photos pick-up only. That way I meet them somewhere and give them the photons (finding a way to collect them is their responsibility) Nil Einne 14:48, 15 October 2006 (UTC)

New Dynamo Not Working Right

The groves on my dynamo wore away and the rubber that they were made from fell to peices so I replaced it with another. Originally, two wires went into the connections marked with an earth symbol (ignoring the two connection holes marked with bulb signals) and both the front and rear lights functioned. After swapping the dynamo for one with only two connection holes, the rear light no longer functions but the front light does. How could this be? --Username132 (talk) 14:00, 14 October 2006 (UTC)

It is not clear from your description how you have things wired up now.  --Lambiam^Talk 17:25, 14 October 2006 (UTC)

You have to tell first if the rear bulb is OK in itself : test it against some battery. -- DLL ^{.. T} 18:27, 14 October 2006 (UTC)

Electrical connections have a nasty habit of corroding over time. Perhaps when you put the wires back, the exact points of contact for the rear light were not clean metal but rather oxidized, high-resistance points? We're not talking about enough voltage to punch through any significant blockage. Or maybe it is a change in the required wiring from old dynamo to new.

Atlant 13:43, 16 October 2006 (UTC)

I figure out that my problem was that both wires should go to the same connection. I never really understood how the lighting worked but it seems that it uses the frame of the bike as one of the connections. I had the back light wired to the frame of the bike instead of the other connection provided. Thanks anyway! --Username132 (talk) 14:03, 16 October 2006 (UTC)

Speed of digestion

How long does it take for food to be digested by human beings, i.e. to go in one end and out the other? Clarityfiend 15:26, 14 October 2006 (UTC)

Now this sounds the perfect question for a science-at-home experiment. Have fun. But I'd say it depends a lot on what yiu eat, wouldn't you agree? Simon A. 16:02, 14 October 2006 (UTC)

Someone did experiments on this in the '60s?. They found that the transit time amongs African tribes was about 3-4 hours, whereas in the Western world it was more like 6 hrs. Hence the recommendation to eat more fibre like the African tribes did to avoid Western diseases. 8-)--Light current 17:35, 14 October 2006 (UTC)

Oh, I thought it was to avoid a pale skin.  --Lambiam^Talk 17:40, 14 October 2006 (UTC)

No: I dont think lots of fibre turns you black. However, excessive amounts may make you act like a horse.--Light current 18:37, 14 October 2006 (UTC)

• cough* *cough* racist! *cough* — X [Mac Davis] (SUPERDESK|Help me improve)04:45, 15 October 2006 (UTC)

This time, for a change, let me be the one to advise you to go see a doctor. DirkvdM 08:30, 15 October 2006 (UTC)

I Africans have such a healthy diet that we should copy it, then what are they complainig about? :) DirkvdM 08:30, 15 October 2006 (UTC)

I didnt know they were complaining about the diet, maybe just the quantity?--Light current 10:35, 15 October 2006 (UTC)

Anyone who claims their digestive process takes over a week is full of crap. :-) StuRat 18:41, 14 October 2006 (UTC)

Well maybe half full. THe bottom half we hope 8-(--Light current 18:45, 14 October 2006 (UTC)

I knew a guy who claimed that his digestion only took about half an hour. --WhiteDragon 17:59, 16 October 2006 (UTC)

Well, some things, like apple cider, can go right through you that quickly. StuRat 19:20, 16 October 2006 (UTC)

Yeah what this guy meant was that half an hour after eating something, he had to have a crap. Cause and effect? Yes and no, but what goes in does take time to travel the 33ft of intestines. Half an hour would be 1 ft/min or 1" every 5 sec! Plainly ludicrous unless you have dysentry--Light current 08:18, 17 October 2006 (UTC)

Right, that's just the new stuff pushing the old stuff out. The same thing happens with electricity in a wire. You put some electrons in one end and some fly out the other end. For those specific electrons to make it through the wire takes much longer, however. To prove the case to your friend, have him eat a can of corn and then "watch for the results". :-) StuRat 15:25, 17 October 2006 (UTC)

rainbow

does the rainbow look the same to everyone

Probably not; some people are colour blind. Or do you mean whether it depends on where you stand? As long as there are enough water drops around and you have the sun in your back, you should see a rainbow as an arc, centred around the point where the shadow of your head is and with an angular radius of about 42°. That is the same for every observer. As you move, the rainbow moves with you, just like your shadow. See further our article Rainbow. Finally, perhaps you mean the old conundrum whether you see the colour red the same as the next (not colour-vision challenged) person. Do you have the same subjective experience? That question is intrinsically unanswerable, and it can even be argued that it is meaningless. See further the article on the philosophical concept of "Qualia".  --Lambiam^Talk 17:36, 14 October 2006 (UTC)

No. From above it looks like a complete circle. See rainbow Hence you can never get to its end and find the pot of gold 8-(--Light current 17:38, 14 October 2006 (UTC)

Clotrimazole 1% Cream

Would it be safe to use this once or twice as impromptu treatment for oral thrush?

No, clotrimazole is available in lozenges for this purpose, ask your doctor about them. Note that oral preparations of clotrimazole need a prescription in part because they can have profound effects on the metabolism of other drugs. This drug is not normally absorbed through the skin, so it is safe to use, for example, on the feet without a prescription; but systemic (i.e. oral) use should be done under the supervision of a physician.Tuckerekcut 18:31, 14 October 2006 (UTC)

Contaminated drinking water

I have been involved with a situation this week, where a water sample taken from taps used for drinking was found to have "Rotaser" in the sample and the Water Supplier demanded that the water supply be turned off immediately. Can someone tell me what "Rotaser" is please. Thanks.

Perhaps you misheard the word protozoa. Are you from Boston?Tuckerekcut 18:34, 14 October 2006 (UTC)

How about rotifer ? StuRat 18:35, 14 October 2006 (UTC)

OK I'll have it well done with salad. 8-)--Light current 18:43, 14 October 2006 (UTC)

I received a phone call from the Water Supplier's Scientist who spelt the word out for me. I am from Kent in the UK, but I fancy Boston.

I suspect that the "scientist" is either incompetent or not really a scientist, and was just reading a misspelled version of "rotifer" to you. StuRat 15:22, 17 October 2006 (UTC) StuRat 15:17, 17 October 2006 (UTC)

Safe to say we don't know? Google brings up nothing.[http://www.google.com/search?num=20&hl=en&lr=&safe=off&q=Rotaser&btnG=Search — X [Mac Davis] (SUPERDESK|Help me improve)07:50, 17 October 2006 (UTC)~

Why does my stomach growl?

Little growls are common, but when I haven't eaten for about 12 hours (which is rare), my stomach makes a reeeallly long growl - like 5 seconds straight. I was just curious to know what exactly is going on down there... - R_Lee_E (talk, contribs) 19:25, 14 October 2006 (UTC)

Your new word for today is borborygmus. alteripse 19:32, 14 October 2006 (UTC)

Since the article doesn't actually answer the question, I'll make an effort: The sounds you hear in your belly are essentially sounds created from air bubbles pushing in the direction opposite the chyme (food) in your belly. Your intestines are like a long cylindrical baloon with both mushy food/poop and gas. The muscles lining the intestines are regularly squeezing in a rhythmic fashion (see Peristalsis), parallel to the lumen of the intestine. When the muscle squeezes the gas and chyme down toards the terminal end, the pressure builds up and two things can happen: either the chyme/gas can push further down the alimentary tract, or the gas can squeeze through the contracting muscles to relieve the pressure. The first case can happen until the chyme (poop) pushes against your anus (specifically the voluntary sphincter, the first area with voluntary control), but the latter case happens often too, and this causes bowel sounds. These sounds are more easily heard when they occur near the distal end of the alimentary tract, but they occur throughout, and can be auscultated with a stethoscope.Tuckerekcut 04:39, 15 October 2006 (UTC)

Could you also explain why the sound is much louder when the digestive tract is rather empty? Simon A. 09:04, 15 October 2006 (UTC)

I don't know but maybe because there's more gas? Nil Einne 14:44, 15 October 2006 (UTC)

Probably it is louder when there is less material in the tract for a few reasons. First, if there is less chyme, then the gas bubbles are large (whereas lots of chyme causes lots of small bubbles distributed through the intestines), so the individual noises will be louder, though longer in between. Also, the gas spaces themselves, being larger, will cause the sounds to seem louder through resonance. The latter case is not dissimilar to a sink emptying: when the sink is mostly full, the drain sounds are muffled by the rest of the water, but there is a loud "sink emptying sound" when the last bit of water swirls down the drain. Don't take this as fact, though, I'm really just guessing on this one.Tuckerekcut 18:44, 15 October 2006 (UTC)

Good idea, the comparison with the sink. That sounds convincing. Simon A. 20:25, 16 October 2006 (UTC)

Asian giant hornet

The article we have on this beastie states, "The stinger of the Asian giant hornet is about a quarter-inch (6 mm) in length, and injects an especially potent venom that contains an enzyme so strong that it can dissolve human tissue" and goes on to say "The venom is optimized to kill bees". Am I the only person to feel that there is an inconsistency with this? Why would it produce such potent venom when it would seem that a single well-placed sting with a venomless stinger of that length would likely incapacitate, if not outright kill, a bee? Or am I underestimating the hardiness of the insects? Vitriol 20:03, 14 October 2006 (UTC)

Interesting question. I'm no expert either, but I can well imagine that chitin is so hard that it is easier to dissolve it with a corrosive liquid than to pierce it. Note especially that in order to pierce a hard fabric, you need a substantial force. (Have you ever tried to push a needle through leather?) A hornet, even if it is a giant hornet, might be simply to light to apply this force without pushing itself away rather than piercing the victim's shell. And as far as well-placed is concerned: if the hornet and the bee engage in a dog fight they might not have the liberty to carefully place their stings. Simon A. 20:15, 14 October 2006 (UTC)

The word "inject" suggests that the exoskeleton is first pierced. I assume the venom has to act quickly, since a bee sting might still be fatal to the hornet.  --Lambiam^Talk 21:02, 14 October 2006 (UTC)

Bee stings don't really affect the hornet, in fact, only the native bees have found a way to kill it (see the bee ball in the article), the European honeybees that beekeepers initially used were just slaughtered by the giant hornet. The dog fight stuff is wrong too, the hornet raids the beehives. As for the asker's question, I don't know the answer. The above information comes from a program on Discovery I saw about them. However, I *think* saw the giant hornets kill small birds. And i believe some professor talked about being attacked as a child so I think the statement could in fact be correct. - Dammit 21:21, 14 October 2006 (UTC)

Building Audit

How do I conduct a building audit ? 219.95.213.170 22:05, 14 October 2006 (UTC)

Do you mean a structural inspection, a financial audit of the company that owns the building, or what ? StuRat 00:28, 15 October 2006 (UTC)

What kind of insect is this?

Hi, what kind of insect is this: http://static.flickr.com/100/269517767_fdf7e2009b_b.jpg http://static.flickr.com/96/269517764_b83e0f27e0_b.jpg Here someone says assasin bug (sometimes called a conenose) http://forums.dpreview.com/forums/read.asp?forum=1036&message=20460456 But ... I don't think that is correct. /Roland

It's not correct. Vitriol 22:59, 14 October 2006 (UTC)

I don't know and I doubt I can help but I suspect others could potentially be more likely to help if you could give details of where this photo was taken etc Nil Einne 14:41, 15 October 2006 (UTC)

It certainly doesn't look like an assassin bug, but it is definitely some sort of bug; you can tell by the ventrally retracted mouthparts. BenC7 01:11, 16 October 2006 (UTC)

Having said that, though, a number of insects are known to change colour in the early stages of their life. BenC7 01:15, 16 October 2006 (UTC)

Two questions about chemical reactions

1. The atoms in HCl and NaCl all have full outer electron shells in these constellations, so why does HCl react with, say, skin, and NaCl does not?

2. H2 and O2 have full outer electron shells, so why does 2H2 and O2 react to become water? Jack Daw 23:15, 14 October 2006 (UTC)

Do your own homework, please. Vitriol 01:06, 15 October 2006 (UTC)

this doesn't have a homeowrk ring to me, so here goes. 1.what you want is the page acid. HCl is an acid, because it is a source of "H⁺". this is the species that causes damaage to your skin. 2. full electron shells don't necessarily denote stability. things can be stable for a number of (rather complex) reasons, but here is a simplification. in the case of molecules like O2 the molecule can react to form molecules of lower energy, like the reaction with H2 to give water. so given the choice between the full shells of O in O2, and the full shells in H2O, the oxygen would much rather be in H2O. Xcomradex 01:23, 15 October 2006 (UTC)

1. What is it about hydrogen that makes it react with skin? Why isn't Na "loosened" from its bond with Cl to explode (as it says on the sodium article that it does on contact with water)? 2. They don't? So what's up with what you learn in school that "atoms want to achieve noble gas structure", is that oversimplified BS? Anyway, why, then, will a molecule of lower energy "rather" be formed? Jack Daw 02:40, 15 October 2006 (UTC)

sodium explodes because of the burning of the hydrogen formed:

2Na⁰ + H₂O -> H₂ + 2Na⁺ + 2OH^-

so compounds containing Na+ will not explode in the same way. The acid burns you by changing the pH of your skin, which causes denaturation. the Na+ ion does not change the pH, so doesn't burn you. your school-level simplification is exactly that, a simplification. you can have compounds with full electron shells undergoing reaction (eg. the noble gas xenon forms many compounds, such as xenon difluoride). and you can have molecules with unfilled shells that are quite stable (eg. the stable radical TEMPO). it is not a worthless concept, but it is not a hard and fast rule either. the entire universe is slowly winding down into its lowest energy state, these same rules apply to chemistry, and ultimately control what compounds are formed in chemistry. if you are interested in this sort of thing a few advanced level chemistry courses could keep you entertained for quite some time. Xcomradex 04:28, 15 October 2006 (UTC)

Thank you. Actually chemistry is my first alternative to med school. Anyway, I can once again conclude that pre-college education is simplified to a very frustrating level. Jack Daw 16:29, 15 October 2006 (UTC)

if those are your interests you should consider scrapping medicine, and doing medicinal chemistry. they're the guys who design and build new drugs. Xcomradex 21:27, 15 October 2006 (UTC)