Wikipedia:Reference desk/Archives/Science/2006 December 1

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December 1

global warming

is Shutdown of thermohaline circulation like to happen in the next 100 years? Dragonfire 734 00:19, 1 December 2006 (UTC)

See shutdown of thermohaline circulation. Short answer: Is it something that we predict will happen in the next 100 years? No. Is it something that could happen? Yes. In my opinion, possible but not likely. Dragons flight 00:25, 1 December 2006 (UTC)

Not likely to shutdown, but it is likely to slow. by how much and what the effect will be is unknown, but Northern Europe will become colder and Labrador/Newfoundland wil become warmer.--John

I still don't understand how it could possibly shut down. The THC has lasted through ice ages and thick and thin. It only moves and has probably broken at times, but has it ever STOPPED? The ocean will never stop having currents, on all scales even up to the THC. X [Mac Davis] (DESK|How's my driving?) 05:09, 1 December 2006 (UTC)

Gulf_Stream#The_effect_of_global_warming mentions a research published in Nature that showed a weakening of the flow by 30% since 1957. 30% in just half a century. And more ice will melt, which would make it worse. But this is all still very sketchy. The problem is we may be heading for disaster and the indications are there, but we don't yet know how big a disaster it is and some see a reason in that to not do anything about the causes. And since such actions would cost us, those who don't know would rather believe the sceptics. It's russian roulette. We have strong indications that there a bullets in the gun, but we don't know how big they are or how many, so we take our chances and pull the trigger anyway. DirkvdM 09:00, 1 December 2006 (UTC)

The basic theory is that a sudden slug of fresh water from the melting of the northern polar regions could disrupt the flow. A recent article in New Scientist magazine seemed to suggest that this was unlikely, though, and I sure hope it doesn't happen. - Atlant 13:35, 1 December 2006 (UTC)

That happened several times before, like in Meltwater pulse 1A (which I will expand someday!), maybe during the Bølling-Allerød interstadial event, and also the Hudson megaflood at the end of one or two ice ages ago. Glacial dams broke around the Canadian shield. X [Mac Davis] (DESK|How's my driving?) 18:49, 1 December 2006 (UTC)

The planet has been siginificantly warmer and colder than it is now. I don't think there is any evidence that the circulation stopped in any of those periods. --Tbeatty 07:15, 2 December 2006 (UTC)

Stratified oceans and deep water anoxia/euxinia are well known occurences over geological time scales (many millions of years). Currents will always exist in the oceans, but overtuning circulation is apparently optional. If the meridional overturning circulation in the North Atlantic stopped it would significantly alter the intensity and orientation of surface currents. The degree to which this can occur in the present world is unclear, but most scientists believe Dansgaard-Oeschger cycles are related to changes in thermohaline circulation during the last glacial period. Dragons flight 20:27, 2 December 2006 (UTC)

RNA code

I am reading a paper doing a mtDNA study on blacktip sharks. The authors use primers which they give explicitly. One of the sequences starts AGG GRA AGG... Does the R stand for something like multiple bases, or is it (as my office mate suggested, a typo in the paper)? Thanks, --TeaDrinker 02:30, 1 December 2006 (UTC)

"R" refers to an unspecified purine nucleoside [1]. Cheers, David Iberri (talk) 02:47, 1 December 2006 (UTC)

Great, that's exactly what I was looking for! --TeaDrinker 02:50, 1 December 2006 (UTC)

Are flaxseed meal's omega-3 fattty acids adversely affected by cooking?

I looked at the article on flaxseed. This issue didn't seem to be addressed.

Thank you for your help! My father likes to bake bread with it, but I think you're better off consuming it raw. We hope you can help us resolve the question.

According to this, it is negatively affected by heat. As far as I know, all healthful oils are made less healthful by heating. Flax seed is good ground on cereal or salad, and flax oil can be used on salad, as an accent in soup, to dip bread in, etc. Anchoress 04:43, 1 December 2006 (UTC)

Flax seed makes good bread (are dads not always right?) The LNA and lignans are unaffected by cooking at 180°C (350F) for 2 hours. You can read about it at the Flaxseed Council of Canada site. Seejyb 09:22, 1 December 2006 (UTC)

Underwater/Undersea Colony

So lets say I wanted to build a dome like structure on the bottom of the ocean. I was reading that the chemicals in the air affected voices and health of the people in earlier experiments like this one, so my question is why can the air system be like that on the ISS?

well it all depends on air pressure. getting out of low pressure too quickly can initiate a fatal disease.--Records 07:39, 1 December 2006 (UTC)

Could you provide us with a link to what you were reading (about chemicals in the air in underwater domes) ? I would think that would result from using new components that haven't been properly aired out, especially plastic components. Also, the lack of air exchange underwater would tend to cause a build-up of chemicals in the air. A power source like a nuclear reactor could provide for all the oxygen needed, by the electrolysis of sea water (and all the water needed could be created by desalination). However, you can't have air that's 100% oxygen. The filler gas in the atmosphere is nitrogen, but that's not readily available under water. I can't think of another filler gas that's readily available, either. You could try filtering toxic chemicals out of the air, but you might have more luck with the reverse process. That is, filter the nitrogen out of the air and discard whatever's left. StuRat 08:16, 1 December 2006 (UTC)

I think this is missing the original poster's point. Note the reference to people's voices being affected. An underwater habitat must either have an extremely strong hull like a submarine, or else it must contain air at pressure comparable to the water pressure outside. Except it can't be normal air, because at such pressures it becomes toxic, so a suitable breathing gas mixture must be substituted. (And one trivial effect of this substitution is a change of voice.)

The reason this issue is not applicable to space habitats (or vehicles) is simply that they don't have to contain air at high pressure. Normal air at normal pressure will do. In fact, pressures lower than normal can be used (allowing the hull to be built more lightly) by increasing the proportion of oxygen: early US spacecraft used pure oxygen, until they found out the hard way how bad a fire hazard this was when the spacecraft was still on the ground and the pressure inside was therefore higher.

--Anonymous, 11:00 UTC, December 1.

Thanks for the interpretation. I didn't get that "chemicals" = "trimix or other gas mixtures". StuRat 11:29, 1 December 2006 (UTC)

Sorry I didn't even sign my question. I was watching a video about Jacques Yves Cousteau and it talked about him breathing in helium in his underwater habitat so him and his crew were affected in the voice and thier taste buds also. My Next question is, how thick would the hull have to be of my submarine habitat be if I wanted regular air pressure in my habitat? Thank You for all your previous answers to my question.68.120.231.137 00:01, 2 December 2006 (UTC)

If the hull is a solid sphere, with no doors or windows, not all that thick. Cameras can be used for outside views, so the no windows parts is OK. The no doors bit is a problem, though. Perhaps two hemispheres can be sealed together with the crew inside, then lowered into position, then pulled back up and unsealed. If you do have doors, they would need to be complex airlocks, not just the hole in the bottom of the hull that's sufficient in an unpressurized system. StuRat 09:50, 2 December 2006 (UTC)

Thank You StuRat.

You're quite welcome. StuRat 08:14, 3 December 2006 (UTC)

Universe - photon fraction

Can we say what percentage of the mass of the universe is in the form of photons? What with mass and energy being equal and all there should be a definite answer, yes? I suspect it must be very tiny though since it isn't typically listed in these sorts of diagrams [2]. I'm talking about all photons now, not just the CMBE. --Deglr6328 09:16, 1 December 2006 (UTC)

A quick googling and some rough calculation turns up the following.

First off, I wanted to find out the ratio of photons/atoms in the universe. According to this University of Oregon webpage, it's about 1.9x10⁹ to 1.

CMBR makes up enough of the photons observed that for a back of the envelope calculation it suffices to assume the rest is negligible, and excluding dark matter/energy the vast bulk of the remaining mass of the universe is from hydrogen. One atom of hydrogen weighs 1.67x10^-27kg. E=mc² tells us this is equal to 1.50x10^-10 J. The average wavelength of a CMBR photon is around 1.9x10^-3 m. Using E=hc/λ, this means you'd need 1.44x10¹² photons for every hydrogen atom to equal the total conversion energy of all the hydrogen in the universe. According to NASA, Hydrogen/Helium makes up around 4-5% of the matter/energy of the universe. So the combined energy of every photon makes up roughly 0.004%. Which is still far more than I'd thought. GeeJo ^(t)⁄_(c) • 10:49, 1 December 2006 (UTC)

Are these calculations for Invariant mass? --JWSchmidt 14:51, 1 December 2006 (UTC)

Yes, as long as you mean the invariant mass of the entire collection of photons, and not an attempt to add their individual invariant masses, which are all zero. This kind of question has plagued Talk:Photon, as I'm sure you can imagine. Melchoir 16:20, 1 December 2006 (UTC)

And bear in mind that the above comes from a few minutes of rough work by a chemistry undergrad and not a worked-through calculation by a physics professor :) GeeJo ^(t)⁄_(c) • 17:01, 1 December 2006 (UTC)

wow. interestintg that its in the thousandths of a percent. I can't say that I'm quite sold on the idea that the non-CMB photon fraction is negligible though. I mean even if the non-CMB photon flux is a millionth that of the CMB they should still be relevant, as a visible/UV photon is some ~ 10⁶ tmes more energetic than a microwave photon....--Deglr6328 21:28, 1 December 2006 (UTC)

True, but I had to pick a value for the wavelength to make the planck calculation, so after google failed to provide a source giving the absolute median of all wavelengths in under a minute or two of searching, I went for the best estimate. Like I said, it's a back-of-the-envelope calculation by a non-expert. I fully expect there to be at least one physicist reading this and wringing their hands in despair, and they're more than welcome to give it a better go. GeeJo ^(t)⁄_(c) • 00:57, 2 December 2006 (UTC)

I'm having trouble making this all fit in with what I read at antimatter, baryogenesis and CP-violation. It sounds like the popular theory is that the vast majority of the matter of the universe was converted into photons in the early universe when particles and anti-particles combined, or is that wrong? --JWSchmidt 00:48, 2 December 2006 (UTC)

If you read the link to the University of Oregon webpage I mentioned earlier, it actually discusses this very topic. In short, since an electron/positron reaction produces two photons, and the ratio of photons:matter particles is 1,900,000,000:1, you're perfectly correct in saying that a vast number of such reactions must have taken place. As an aside, they're actually working in the opposite direction of the above calculation, using CMBR density to work out the photon:particle ratio. GeeJo ^(t)⁄_(c) • 01:07, 2 December 2006 (UTC)

I guess I must have an unrealistic hope for a possible role played by conservation of invariant mass. I thought that if in the early universe there was a large amount of mass produced in the form of particle/antiparticle pairs and most of those pairs were converted into photons and there was conservation of invariant mass then the current universe might have to have more invariant mass in photons than in the small fraction of matter that escaped antiparticle annihilation in the early universe. Do the calculations earlier on this page take into account the momentum of photons? --JWSchmidt 02:02, 2 December 2006 (UTC)

Not bad, Geejo. Photons are closer to 0.0025% of the energy in the Universe. JWSchmidt, you may be interested to know that there once was a time (though brief) when there was more energy in radiation than in matter (the first few hundred thousand years), but the fraction in radiation has steadily declined as the universe cooled/expanded. Even so, the amount of energy in the cosmic microwave background is still enormous. Summed over the entire visible universe, it amounts to roughly 100 times the energy generated by all the stars that have ever burned. Which also explains why it is a good approximation to say that the only photons that matter to the calculation are microwave background photons. Dragons flight 04:25, 2 December 2006 (UTC)

Woo, got it in the right order of magnitude. The Fermi method works! GeeJo ^(t)⁄_(c) • 14:49, 2 December 2006 (UTC)

Just to be totally clear though, when you say "summed over the entire visible universe, it (the CMB) amounts to roughly 100 times the energy generated by all the stars that have ever burned" you're NOT just saying the number of photons in the CMB is 100 greater than the number from stars but rather that the number times the average frequency (times h) of the CMB is overall 100 times greater than the number times the average frequency for light emitted by stars.....right?--Deglr6328 08:23, 2 December 2006 (UTC)

Yes, total energy, not just number of photons. Dragons flight 20:31, 2 December 2006 (UTC)

Apropos of nothing, I thought I'd mention Cosmic latte, if only because I ran across it while checking for figures and it's such a cool (read: nerdy) thing to know :) GeeJo ^(t)⁄_(c) • 21:13, 2 December 2006 (UTC)

Palmistry 2

I didn't get much of a response to my last question [3], which I realized might be because I posted it over Thanksgiving. If you have any ideas, I'd love to hear them.

I'd like to ask something more specific, though. Does anyone know how I can get in contact with a doctor or medical specialist who would know the answers to these questions, or maybe a textbook? I don't really know where to start. I tried putting 'ask a doctor' into google, with limited results. I'm not even sure what specialty my questions would fall into, if there is one. Black Carrot 10:11, 1 December 2006 (UTC)

While I cannot answer your question directly, my thoughts for finding an answer would be: 1. Consult a forensic pathologist. If you are close to an academic institution that would be ideal, but a local police mortuary may give you direction on where to find a person to talk to. I do know that the description of hand markings was the subject of a lecture on forensics to students at our med school, but have no clue as to what the references were. 2. Some dermatologists have a specific interest in hands, and this interest is usually known to colleagues. 3. Hand surgeons are also known to have an interest in the appearance and use of the human hand, beyond that required for doing surgery. I have little doubt that amongst these you will find information and guidance for looking further. On the web you may find contact details for forensic pathology or human identification, dermatology and hand surgery, but I suspect that personal contact may be more productive. -- Seejyb 14:42, 1 December 2006 (UTC)

Try an occupational therapist or a hand surgeon. -THB 01:02, 2 December 2006 (UTC)

Why is that everything seems to be unionized these days?

What exactly do people have against a little ionizing radiation? It's discrimination really, ions are people too you know--13:48, 1 December 2006 (UTC)

I wouldn't consider it discrimination as the ions as such don't even exist until you ionize something. –mysid☎ 14:18, 1 December 2006 (UTC)

I'll charge right in and say that some people's views of ions are positive, and just about as many are negative. StuRat 14:51, 1 December 2006 (UTC)

For everyone who makes a charge, there is an opposite charge. Inevitably, the two come together, resulting in unionization.

Really shows that the word is a shibboleth for chemists when even with the phrasing of the question header directly pointing to discussing unions rather than ions, I still read it as the latter on the first pass. GeeJo ^(t)⁄_(c) • 18:50, 1 December 2006 (UTC)

"Unionized" is one of these English words with 2 pronunciations and 2 meanings. "Invalid" is anotherEdison 19:04, 1 December 2006 (UTC)

Organized labor and electricity jokes aside, isn't the proper word for something lacking ions 'deionized'? --Jmeden2000 19:54, 1 December 2006 (UTC)

Deionised implies that the something has had charge removed. Unionised implies it wasn't charged beforehand. Google shows "Un-ionized" has a fair number of hits in the Chemistry literature, with at least as many going for "unionized + ion" (to filter out unions), and then you have those who use unionised instead. So it appears to be a fairly common term (I've certainly used it in more than one lab report without losing marks.) GeeJo ^(t)⁄_(c) • 20:36, 1 December 2006 (UTC)

Because no one ever got around to ionizing things. -THB 01:00, 2 December 2006 (UTC)

Question about bottled water...

I`ve heard recently that it is unhealthy to refill empty bottles from bottled water, with water, and consume. Any truth to this? Dave172.163.70.157 15:31, 1 December 2006 (UTC)

There's nothing inherently unsafe about tap water that's been stored in a bottled water bottle. However, there have been studies to suggest that bottles which are repeatedly reused are very rarely cleaned sufficiently between uses. Consequently, they become a breeding ground for various pathogens; you can get a very hardy biofilm established. (Thorough cleaning – sufficient to remove or kill all the potential nasties – can be fairly difficult.)

If you want a reusable water bottle, you're much better off buying one designed for the purpose. (Nalgene makes some very durable ones.) Wash the bottle as soon after use as is reasonably possible. You want something with a wide enough mouth that you can reach in and wipe all the inner surfaces with hot soapy water. Rinse with hot water, and let dry before reuse. TenOfAllTrades(talk) 15:53, 1 December 2006 (UTC)

Remember though that if the bottle originally contained water and is refilled with water there is nothing for a biofilm to grow on.87.102.8.53 16:08, 1 December 2006 (UTC)

Sure there is. You can get a shot of contamination from a small amount of backwashed saliva. Microorganisms can also settle from the air, or be delivered by dirty fingers. From that small start, a colony of photosynthetic organisms can get going. Those photosynthetic organisms, if left to their own devices, provide snack food for heterotrophic organisms. It's an ecosystem in miniature, all fuelled by sunlight, the occasional shot of carbon dioxide when you open the cap, and trace minerals from your tap water. TenOfAllTrades(talk) 16:20, 1 December 2006 (UTC)

Wow! Would this biofilm be visible before it became potentially hazardous? Dave172.163.70.157 17:23, 1 December 2006 (UTC)

Not necessarily. TenOfAllTrades(talk) 17:28, 1 December 2006 (UTC)

Would refridgerating help keep the refilled bottles from contamination? Dave172.163.70.157 17:32, 1 December 2006 (UTC)

That would just slow it down. Try rinsing it with a weak bleach solution. That will kill any nasties inside. Be sure to get the screw threads on the bottle and cap, as those are favorite hiding places for them, and rinse thoroughly afterwards. StuRat 17:55, 1 December 2006 (UTC)

Yikes, I've been reusing for a long time with an occasional trip through the microwave filled with water until boiling occurs. Is that a safe practice? --hydnjo talk 19:39, 1 December 2006 (UTC)

I have found the heat can sometimes warp the bottle.

Yes - you are still alive? No vomiting etc?87.102.8.53 19:46, 1 December 2006 (UTC)

Nah, just some hair loss.  ;-) --hydnjo talk 20:15, 1 December 2006 (UTC)

The bottle caused this?87.102.8.53 20:15, 1 December 2006 (UTC)

At least a year ago, I saw an ultraviolet water bottle cleaner that claimed to kill all the bacteria in under 30 minutes. I wonder how long it took them to go out of business. --Kainaw ^(talk) 20:21, 1 December 2006 (UTC)

For what it's worth, I've been using the same gallon PETE container to store drinking water for the past year. Also, I refill it with NON-chlorinated reverse osmosis water. I only occasionaly rinse it out with hot water from the tap. Is it contaminated with bacteria? Yes, quite. I tested it myself! :) :) Am I worried? No. Gross? Maybe but I haven't been sick once in that time and I drink from it constantly. The type of bacteria that colonize things like water bottles either came from YOUR mouth to begin with or are weird oligotrophs that are rarely harmful to human health. If you are immunocompromized for some reason though, or you SHARE (yuck) the bottle with someone, well that's a whole different ballgame. Then I would definitely sterilize it regularly with bleach or some such. It's good to take reasonable precautions but there's no reason to be hyper-obsessive about bacteria. Remember, you have billions of them living all over your skin at this very moment. --Deglr6328 21:35, 1 December 2006 (UTC)

So the answer to the original question - is 'yes it's safe', or are there any other factors to be taken into account? eg do plastic bottles start to decay after some time leaching plastic into the water or something???87.102.8.53 22:01, 1 December 2006 (UTC)

Thanks for all your responses folks. Not sure if I should continue the practice of re-filling or not...I think I`ll be ok though. Thanks again. Dave172.163.70.157 22:04, 1 December 2006 (UTC)

Why don't you consider re-using the bottles for a limited period of time? It's better for the planet and cheaper. If you wash the bottle with soap and hot water and let it air-dry, bacteria should be minimized. Use a few drops of bleach if you're worried. As far as plastics leaching into the water, refilling it for a limited period of time is as safe as using new bottles. Don't heat it in the microwave or use boiling water as heat can cause some plastics to leach. -THB 00:54, 2 December 2006 (UTC)

One point I don't see mentioned above is the matter of whether you drink directly from the bottle. Assuming that you are concerned about bacteria from your mouth, they aren't going to get into the bottle if you only use it to pour water out into a glass. --Anonymous, 04:10 UTC, December 2.

I'm surprised that it hasn't been mentioned yet that apparently plastics that aren't meant to be reused shouldn't be reused, because they can break down and leach chemicals into the liquid or food contained within them. I'd be especially concerned about microwaving them. From what I understand, the safety of most disposable plastics is very borderline, and they are tested and approved only for a single use, without any over-building (safety with multiple uses, exposure to heat, microwaves, etc.) Anchoress 04:23, 2 December 2006 (UTC)

Shouldn't it stand to reason that if a plastic container is safe enough to drink the original contents out of after it has been sitting on the store shelf for who knows how many months then it should also be equally safe if you are drinking water or whatever that you just put in it? The leach levels of various volatile organic compounds from plastic containers is so absurdly low that it is absolutely not worth worrying about with possibly one exception. The exception may (and I heavily stress may) be the use of lexan/polycarbonate bottles such as in Nalgene bottles which leach out tiny amounts of bisphenol a an estrogen analogue. But then these containers were DESIGNED for reuse(!!) and at the levels found from such bottles even after numerous studies in several different countries there have been no restrictions or regulations on use for such products. Seriously, imnsho, worry about driving safely/wearing a seatbelt and not becoming one of the one million people who die every year in road traffic accidents, not the 5 parts per billion levels of possibly harmful chemicals from your plastic containers.--Deglr6328 09:17, 2 December 2006 (UTC)

I usually drink the refill within 12 hours or so. From all the responses so far, I think I`m pretty safe. I`m not going to worry about it. Thank you all. Dave172.163.70.157 10:29, 2 December 2006 (UTC)

Not necessarily. The plastic definitely ages; I left a bottle of water in my car for approximately five months, because I completely forgot about it, then one day, when I was really thirsty, I opened it... and let's say that "it tasted like plastic" was a severe understatement of the situation. While the water may accelerate the solution of the plastic, exposure to sunlight also has a damaging effect on the containers; but of more importance is that the taste will become intolerable, and that's why 18 truckloads of unused water bottles were thrown into a sewer following Hurricane Katrina.^{[www.freerepublic.com/focus/f-news/1549974/posts]} Titoxd^(?!?) 00:09, 4 December 2006 (UTC)

Bit worried about peoples suggestion to use bleach - if it's hypochlorite bleach then that can react with organic chemicals - chlorinating them - plastics aren't stable to bleach like glass is.83.100.253.51 14:48, 2 December 2006 (UTC)

Ithought the problem was supposed to be the leeching of chemicals fromthe plastic into water and subsequent ingestion? --Username132 (talk) 19:48, 2 December 2006 (UTC)

Channel Tunnel

Was there anything particularly difficult about constructing the Channel Tunnel? Or is it essentially the same as a much shorter tunnel, only longer? Auximines 22:55, 1 December 2006 (UTC)

The notable problems were not physical. See the construction section in the article. Consider that many people in the UK did not want a physical connection to the continental mass, that the tunnel links two countries, that it was privately financed and constructed. There was even a bankruptcy. The New York City Water Tunnel No. 3 is probably more problemmatic physically. -THB 00:58, 2 December 2006 (UTC)

Thatcher wanted this to become a showcase example of how big projects would be done better if undertaken by private parties. Boy, was she proven wrong. :) DirkvdM 10:26, 2 December 2006 (UTC)

It seems an obvious target for terrorism, as well, so that's another problem they need to protect against. StuRat 09:35, 2 December 2006 (UTC)

Why? DirkvdM 10:26, 2 December 2006 (UTC)

Why is it an obvious target ? Because a truck bomb that ruptures the tunnel could kill everyone inside it, cause significant economic disruption, and attack two nations at once. Isn't all this obvious ? StuRat 08:10, 3 December 2006 (UTC)

But why specifically the Chunnel? Any big structure is a good target for those purposes. One differnce would be the considerable economic cost, but I don't think that is a common goal for terrorists. So the Chunnel is nothing special in those terms. Anyway, it was built before the recent terrorism hype. DirkvdM 08:38, 4 December 2006 (UTC)

If they need to retrofit the Chunnel to be able to withstand a terrorist attack, that would be even more expensive. And to call terrorism "hype" is like calling AIDS "hype" when it was first starting, in the 1980s. It was largely ignored and allowed to spread, and now millions die from it every year, as a result. One advantage of the Chunnel as a target is that the water pressure would do most of the damage, all they would need to do is put a hole in it. StuRat 09:27, 4 December 2006 (UTC)

It had to be negiotated thro the undulating chalk layer. ie it wasnt just a point to point construction. Also it had to have the British and French working together (no comment) --Light current 22:08, 2 December 2006 (UTC)

That's true, but all long tunnels are likely to encounter some sort of difficult geology. I'm not saying it was easy, but I don't think it was unexpectedly hard.

One thing that was a big deal compared to shorter tunnels was the accuracy required. The undersea part of the tunnel was about 21 miles long and was bored from both ends towards the middle in order to reduce the construction time. They obviously couldn't use satellite navigation, nor could they use vertical boreholes to confirm the tunnel alignment. So they had to bore for more than 10 miles with a position error no more than a couple of feet, or else some expensive work would be required to correct things. They used lasers, of course, but even without the curves it wouldn't have been just a matter of pointing a beam down the tunnel and following it. First it would have to be aimed correctly; second, temperature variations in the tunnel would cause the beam to refract and the desired accuracy would not be achieved, so they had to correct for that too.

If you want to read about the project in great technical detail, the book to look for is Engineering the Channel Tunnel, edited by Colin J. Kirkland, published 1995, ISBN 0-419-17920-8. A university library or a large central public library would be the best places to look for it. A less technical book, which also goes into the history of the project and the political and financial issues, is Worlds Apart: Dreamers, Bankers, Engineers, and the Building of the Channel Tunnel also known (I think this is the North American title) as The Chunnel: The Amazing Story of the Undersea Crossing of the English Channel, by Drew Fetherston, 1997, ISBN 0-8129-2198-4.

--Anonymous, 06:10 UTC, December 3, 2006.

Why does increased estrogen cause post nasal drip?

Is it vasodilation like blood pressure medication or what?

This article makes me think that nasal epithelial cells may respond directly to estrogen. One effect of estrogen in epithelial cells is to regulate Nitric oxide synthase. Our article on erectile tissue fails to mention the fact that humans have erectile tissue in some parts of the nasal passages. It may be that during evolution there have been species for which effects of estrogen on nasal mucosa cells was important for reproductive behavior. --JWSchmidt 02:34, 2 December 2006 (UTC)

Further, its interesting to speculate of a possible relationship between olfactory function and hormonal changes during menstrution per that paper. Especially considering the McClintock effect. Rockpocket 06:45, 2 December 2006 (UTC)

Does spoilt soy milk contain Lactobacillus?

I want to know if soy milk that has gone bad contains the same bacteria (Lactobacillus) as cow's milk that has gone bad. I also wanted to know if cow's cream attracts the same bacteria as cow's milk when it has spoilt.

Thank you! --Bess

This sounds like a good science project. You might be interested in this article. --JWSchmidt 02:43, 2 December 2006 (UTC)