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March 4

What was the goal of the Wright Brothers?

The wright brothers created a heavier-than-air air craft, but did they have a goal behind it? Did they imagine a world in where aircraft would be a form of transportation? Thanks. —Preceding unsigned comment added by Legolas52 (talk • contribs) 00:45, 4 March 2008 (UTC)

See Wright brothers. They were not the first to get a heavier-than-air craft to fly. They were focused on creating a steering system to make fixed-wing flight manageable. They succeeded. At the time, many people thought the future would be full of people flying around in small aircraft. Even in the 50's and 60's, it was imagined that personal airplanes were just a few years away. So, assuming that the Wright brothers didn't imagine a world full of airplanes would be very unconvincing. -- kainaw™ 02:55, 4 March 2008 (UTC)

It's pretty amusing how many countries consider one of their own to be the inventor of true flight, simply by adjusting the lever on what constitutes true flight. Once in casual conversation a Brazilian mentioned to me that Alberto Santos-Dumont invented the airplane with as much surety as most Americans say the Wright brothers did so.  :) --Sean 13:09, 4 March 2008 (UTC)

Yes, and New Zealand always trots out Richard Pearse. First flying machine makes interesting reading. Deciding who was "first" and determining it by control, or power, or distance is missing the point. The fact is no one person invented the aeroplane; there was a lot of parallel development late 19th/early 20th C, all of which, in small ways or large, contributed to the development of the modern aeroplane. As to why: well, everyone since Icarus has wanted to fly. Gwinva (talk) 20:22, 4 March 2008 (UTC)

Correct me if I'm wrong, but I believe nature was the inventor of true flight. We took a hell of a long time to catch up!206.252.74.48 (talk) 15:50, 4 March 2008 (UTC)

I flew just fine when I was a small fruit bat. In fact, I often bragged about my ability to zip from place to place in near complete darkness. Then there was that whole evolution thing and it's been downhill ever since. -- kainaw™ 04:04, 5 March 2008 (UTC)

No, things started going downhill after gravity was invented. 206.252.74.48 (talk) 21:50, 5 March 2008 (UTC)

I've always thought that at least part of the Wright Brothers' goal was to make a better income with airplanes than with bicycles. Pfly (talk) 08:10, 6 March 2008 (UTC)

Glow-in-the-dark cats

Where on Wikipedia may I read an article about South Korean glow-in-the-dark cats?--The Fat Man Who Never Came Back (talk) 01:17, 4 March 2008 (UTC)

I would like to see pictures as well.--The Fat Man Who Never Came Back (talk) 01:18, 4 March 2008 (UTC)

It's not on Wikipedia, but I found an article and pictures. [1] Someguy1221 (talk) 01:21, 4 March 2008 (UTC)

Thanks to you!!!!!!!!--The Fat Man Who Never Came Back (talk) 01:44, 4 March 2008 (UTC)

You probably want to look into bacterial transformation (BT), green fluorescent protein (GFP). -- MacAddct  1984 ^{(talk • contribs)} 02:01, 4 March 2008 (UTC)

How about glow-in-the-dark pigs? [2] Sandman30s (talk) 14:35, 4 March 2008 (UTC)

The death of Betelgeuse

I am a fan and ardent reader of Wikipedia, especially the science pages. My question is: why is it so controvertial to discuss the imminent demise of Betelgeuse and what that means for humanity in the Wikipedia article?

Firstly, it is a celebrity star. It is one of the largest stars in the known universe; if it replaced Sol in our solar system, it would reach out almost to Jupiter. This red supergiant is very close, only a few hundred light years away, and it is the very shoulder of Orion: a star that surely each and every one of us can thank for untold choices made by our ancestors in its bright contenance.

Secondly, it is dying. Yes, it's only a few tens of millions year old but it's burning up very large atoms at the moment and there is no doubt that this utterly massive star is at its utter breaking point.

Thirdly, there is an extremely high probability that it will undergo a type II supernova. Perhaps it already has. It's possible, and not all that improbable, that tomorrow night the sky will be a canvas to the most spectacular (and anticipated!) supernova we've ever known. The sky will have a new full moon. The brightness will last for months and maybe even a few years, being visible even in broad daylight.

Orion will lose a shoulder, and a new moon will be born.

This isn't mysticism. It's not astrology. It's likelihood. Surely part of the point of Science is to inspire new generations by presenting facts that captivate. I understand turning down entries to articles that are outlandish though technically possible. But there are an undeniably strong contingent of articles out there that point to the supernova of Betelgeuse and what that implies for the landscape of the sky each and every one of us look upon. Sappysap (talk) 02:02, 4 March 2008 (UTC)

Quick answer - Wikipedia is not a crystal ball and Wikipedia is not a repository for original research. And for good measure, don't use weasel words.

Slightly longer answer - information in Wikipedia has to be verifiable with citations to reliable sources. Even in articles on mathematical subjects (at least the ones that have been labelled good or even featured, like 0.999...) use only information that can be referenced, even in the case of proofs which follow from known axioms. So if Betelgeuse is going to go supernova in the next million years, find a reference for it! If "some scientists say" something, say who. If something "may" happen, put a couple of citations next to it - one that says why it might happen, and one that says why it might not. And, as much as possible, make sure that those references are ones that have some degree of reliability - Physics Review is good, New Scientist is ok, a letter to the Washington Post is out of the question. Confusing Manifestation(Say hi!) 02:17, 4 March 2008 (UTC)

Fantastic use of buzzwords. Hands down, grats for that. But I don't think you have any grasp of the science of supernovae. I'm quite sure you did not research a single lick into why this particular star is unstable. When you want to present yourself as an authority, at least have the audacity of fact to support you. Sappysap (talk) 02:27, 4 March 2008 (UTC)

You asked a question about Wikipedia, Confusing Manifestation explained the issues within Wikipedia. You did not ask anything about the star, only about why things work like they do in Wikipedia. Confusing Manifestation did not attempt or pretend to present themself as an authority on supernovae, or say anything about the science of them. I suggest you reread what was written, perhaps apologise for jumping on someone trying to help you (rather than simply pointing you to the Help Desk where questions about Wikipedia are more properly addresses) and hopefully see that the answer to your question ("why is it so controvertial to discuss the imminent demise of Betelgeuse and what that means for humanity in the Wikipedia article?") has been thoroughly provided. Skittle (talk) 02:40, 4 March 2008 (UTC)

And, to add one more note to Confusing Manifestation's answer: Wikipedia is not a message board. Articles are not a good place to discuss anything. They are for referenced and encyclopedic content. If you want to discuss a possible supernova, go do a supernova message board. I'm sure there are hundreds of possible ones to choose from. -- kainaw™ 02:50, 4 March 2008 (UTC)

Thanks guys. I just needed the publicity. I'm sure the article will be looked at and revised. Just glad this post is still hereSappysap (talk) 02:53, 4 March 2008 (UTC)

I must say that this is a very unusual way of having an article improved. It sure gave me a good laugh. --Bowlhover 03:36, 4 March 2008 (UTC) —Preceding unsigned comment added by Bowlhover (talk • contribs)

Hey, the whole purpose of the reference desk is to improve the quality of the articles, although we treat the purpose as to answer questions! Graeme Bartlett (talk) 05:53, 4 March 2008 (UTC)

I doubt such an event can outclass the Great Collapsing Hrung Disaster of Gal./Sid./Year 03758. 206.252.74.48 (talk) 16:23, 4 March 2008 (UTC)

What is a Hrung, and why should it choose to collapse there, particularly? --Trovatore (talk) 01:29, 5 March 2008 (UTC)

I'm afraid I can't explain that one. Ix talk 15:47, 6 March 2008 (UTC)

Photosynthesis question

I'm doing a sheet of 5 photosynthesis-related problems and I think I've gotten all of them except for 1, which has me totally stumped: "The photosynthetic rate of aquatic plants in a test tube can be determined by collecting and measuring the amount of oxygen that gases out of the water. If bicarbonate, the source of CO₂ for aquatic plants, is added to the water, the rate of oxygen evolution increases. If CO₂ is fixed by the Calvin cycle but oxygen is evolved by the light reactions, how can an increase in CO₂ supply increase the rate of oxygen evolution?" If anyone could point me in the right direction, I'd greatly appreciate it. Thanks, anon. —Preceding unsigned comment added by 70.18.18.201 (talk) 04:33, 4 March 2008 (UTC)

You need to consider the ratio of NADPH/NADP⁺. How does it affect the rate of photolysis? How does the concentration of carbon dioxide affect the ratio? David D. (Talk) 05:12, 4 March 2008 (UTC)

Be mindful in the future that the reference desk is not an appropriate place to seek answers to obvious homework questions. Wisdom89 _{(T / ^C)} 05:16, 4 March 2008 (UTC)

I find homework questions perfectly acceptable on the reference desk. The top of this reference desk has a guideline stating:

"Do your own homework. The reference desk will not give you answers for your homework, although we will try to help you out if there is a specific part of your homework you do not understand. Make an effort to show that you have tried solving it first."

User:70.18.18.201 has not asked for answers and he showed that he tried solving the photosynthesis problem himself, so I see no problem with him asking for help here. --Bowlhover 05:41, 4 March 2008 (UTC)

Not only is there no problem with the question, there is no problem with the answer either. David D has not done the homework for the questioner, but provided him/her with hints and links to help him do it himself, as per guidelines. SpinningSpark 07:09, 4 March 2008 (UTC)

Don't totally misunderstand me. I wasn't admonishing anyone for providing the answer or asking the question. I was just alerting the user to the fact that such questions could be construed as such, and that editors at the reference desk will abstain from answering questions of that nature - in case he/she wasn't aware. It was more of just be careful in the future kind of thing. Wisdom89 _{(T / ^C)} 00:30, 5 March 2008 (UTC)

It's not particularly helpful to indulge in hypothetical philosophical discussions about reference desk procedure with questioners. Best just to get out of the way and let the question be answered, if you don't care to answer it yourself. "Do your own homework" is a means of "biting the newbie" that has been too often tolerated here. - Nunh-huh 02:49, 5 March 2008 (UTC)

Equivalent of menstruation, but in men

Is there such a thing? Do men have cyclical hormonal changes?Mr.K. (talk) 12:10, 4 March 2008 (UTC)

No, there is no monthly cycle in men. Yes, men have cyclical hormonal changes, but they are diurnal, with testosterone levels slightly higher in the morning. But it's a daily cycle, and there's no cycle in men that's longer than a day. As men age, their testosterone levels become lower, but again, that's not a cyclical change, but one due to senescence. - Nunh-huh 12:24, 4 March 2008 (UTC)

Closest I can think of is accidental bloodletting, aka 'accidentally' cutting your finger while chopping vegetables, accidentally falling of your bike and scraping up your knees and elbows, accidentally getting clipped in the face with a hockey stick. Vranak (talk) 21:30, 4 March 2008 (UTC)

Depends on what you mean by equivalent. A nocturnal emission is somewhat equivalent- the body is casting off leftover stuff it wanted to use for reproduction. Friday (talk) 21:33, 4 March 2008 (UTC)

That's not very eqivalent. That only happens if you are aroused while sleeping. Dreaming about having sex, or thinking about having sex. That sort of thing. 64.236.121.129 (talk) 15:33, 5 March 2008 (UTC)

The OP is asking about hormonal cycles, not regular bleeding. Mr K, Chronobiology and Circadian rhythm might interest you.

The OP is asking about the equivalent of menstruation in men. Vranak (talk) 01:04, 5 March 2008 (UTC)

A couple decades ago, I made a non-scientific empirical observation that the severity of acne in a male teenager varies on an approximate monthly basis. It's suggestive of a monthly hormone cycle, but I haven't seen anything written about the phenomenon (if it has been verified to exist). =Axlq 01:40, 10 March 2008 (UTC)

The Human Ship of Theseus thing...

You hear all the time people saying that the cells of your body get completely replaced every 7-10 years or so, questioning the identity over time of human beings by invoking the Ship of Theseus paradox. My question is this: that's just plain BS, isn't it? I mean, sure, some cells do get replaced all the time (skin cells, most obviously), but the cells that play a role in determining who you are, what your identity is, that's your brain-cells, and they don't get replaced, right? I've always been taught that when you hit puberty, you have as many brain cells as you're ever going to have. So doesn't that pretty much blow that little brain tickler clear out of the water (not the general paradox, but as applied to human beings)? 83.250.207.187 (talk) 13:26, 4 March 2008 (UTC)

brain cells might/can regenerate - see brain cell, also why assume they don't?87.102.44.156 (talk) 14:51, 4 March 2008 (UTC)

Some cells are rarely replaced, neurons being an excellent example of one such cell type. However, even in those cells, many of the molecules that compose it are regularly replaced or recycled. For example, the plasma membrane in many cells, again including neurons. The short answer is this: nope, no BS here. – ClockworkSoul 19:44, 4 March 2008 (UTC)

If every cell is replaced by its exact duplicate then the sum of its parts (you) will be exactly the same. Environmental and dietary factors will move you towards, away from, or equidistant to good health. Vranak (talk) 21:23, 4 March 2008 (UTC)

Identity is a complex topic, so to say that it depends entirely on a tangible, precise group of cells or molecules (or to imply that changing the cells changes the identity) makes many profound assumptions. Philosophy of mind may provide some insight. Nimur (talk) 07:03, 5 March 2008 (UTC)

Insects in vegetables?

Hi. I am asking this on behalf of a friend who is a vegetarian. I've heard in various places that the Food and Drug Administration (and in Canada too) allows a maximum number of insect body parts in certain vegetables. Can I get some stats on how many insect body parts are allowed in certain vegetables? I also heard that ant eggs are allowed in peanut butter. In fact, one time I discovered some tiny yellow-brown insects in (homemade) soup (cooked). Now, some people may think it's gross, but it is just extra protein, but for strict vegetarians this may be a problem. Can you give me some stats for Canada, and is there an article on this? They shouldn't spray the vegetables with pesticides to get rid of the bugs, because that might make us sick (which is why I always wash my fruit [except bananas]). Does organic vegetables have more or less maximum insects, or is the limit identical? Please provide some statistics for Canada and which vegetables and other food froducts are most likely to contain insect body parts. Thanks. ~AH1^(TCU) 18:42, 4 March 2008 (UTC)

Its name completely escapes me, but there is a wax secreted from an insect that is used to replace the natural wax coating of apples. It often contains parts from the insect itself. 206.252.74.48 (talk) 19:38, 4 March 2008 (UTC)

Beeswax is often used for coating fruits & veggies. --Sean 20:00, 4 March 2008 (UTC)

While that is true, I'm thinking of another wax created by an insect. The fact that I can't recall its name is really bugging me (no pun intended, seriously). 206.252.74.48 (talk) 20:08, 4 March 2008 (UTC)

Google led me to here http://www.geocities.com/perfectapple/apple_wax.html so check out shellac.87.102.44.156 (talk) 21:22, 4 March 2008 (UTC)

Yep, that's the one! Thank you. 206.252.74.48 (talk) 13:33, 5 March 2008 (UTC)

http://www.cals.ncsu.edu/course/ent425/text18/food.html for canada recommend contacting the canadian equivalent of the 'ministry of food and agriculture'87.102.44.156 (talk) 19:43, 4 March 2008 (UTC)

To get you started, the maximum permissible quantities of insect (and other) bits in foods are specified by the FDA as food Defect Action Levels (DALs). The FDA DAL Handbook is online here: [3]. Canada's rules are probably somewhere on the Canadian Food Inspection Agency website: [4]. TenOfAllTrades(talk) 19:58, 4 March 2008 (UTC)

There are also standards for grain crops foreign matter (mostly stones and insects) that permit them at low levels as it is not practical to perfectly sort them.Polypipe Wrangler (talk) 22:15, 4 March 2008 (UTC)

I suppose it is probably not worthing saying that trying to eat a vegetarian diet without accidentally digesting insects at some level is going to be impossible. Insects are everywhere and they eat everything and it's a fact of life that some of them are going to get sucked up into the food processing apparatus every once in awhile even if you are doing it by hand! Personally I think there are more pressing moral and ethical issues in the world than whether or not you eat a few ants, assuming the objection is moral/ethical (as they pose no real nutritional benefit/deficit). --98.217.18.109 (talk) 14:10, 5 March 2008 (UTC)

• There is now an article on FDA's publication about food contaminants: The Food Defect Action Levels. — Reinyday, 01:36, 14 March 2009 (UTC)

quantity required of trypticase soy agar to test water for fecal coliform

Hi. How much trypticase soy agar is required to test water sample for fecal coliform?Sarah Orlowski (talk) 18:49, 4 March 2008 (UTC)

Thanks, Sarah Orlowski

I'm not sure how anyone could possibly answer the question as put; the quantity of medium you need would depend on the number of samples you're going to test, and on the lab protocol you're using for the testing (I also wonder why you're using trypticase soy agar vs MacConkey medium - unless you're making your own selective medium, in which case again quantity depends on the recipe you're using. - Nunh-huh 02:44, 5 March 2008 (UTC)

BBC Bird Question

In every early morning quiet scene in a British costume dramas, they'll show the protagonist looking pensively over the landscape for whatever reason. Then 4 times of 5, they'll throw in a soundbite of some English bird with a very shriekish call. It's supposed to set the ambiance or something. For instance, you hear it in the beginning of Part 4 of the 1995 version of Pride and Prejudice as Darcy looks over the moors. What is that bird?160.10.98.106 (talk) 19:57, 4 March 2008 (UTC)

Looking in my Collins Bird Guide and having listened to P&P a little, I think you might be hearing the goshawk. Most hawk screams are perfect for punctuating the wildness of an outdoor scene. According to Collins, there aren't many species of raptor in Derbyshire, only the goshawk, the sparrowhawk, the hen harrier, and Montagu's harrier. --Milkbreath (talk) 20:50, 4 March 2008 (UTC)

In the U.S., we use a Red-tailed Hawk scream as the avian version of the Wilhelm scream. -- Coneslayer (talk) 20:54, 4 March 2008 (UTC)

March 5

Avoiding the Nazi Swastika

While I was researching PETN looking for more efficient ways for the atoms and their connections to be drawn I became aware of the potential to draw this molecule in the pattern of a Nazi Swastika and that was before I read that the molecule was invented in Germany and patented by the German government and that the Homeland of the Nazis was Germany. Are there any other molecules that can be redrawn as a Nazi Swastika and if so what are they? Just curious in an odd sort of way.

Is this really science related? Wisdom89 _{(T / ^C)} 00:26, 5 March 2008 (UTC)

More so that art related.

It kinda looks like a swastika in a 2d diagram as shown in the article. But in reality, the 3d structure of the middle carbon is different. Looking straight from above, you wouldn't see the "swastika". The middle part will look like a plus sign. If you look at it sideways, or from the plane of the molecule, the middle part looks like a seesaw. The point is that the swastika is invisible in the 3d structure.128.163.116.74 (talk) 01:19, 5 March 2008 (UTC)

Chemists have a way of describing this - you are looking for a molecule with C_4h symmetry.. (point group) - because of its 3 dimensional structure PETN doesn't actually have this symmetry.87.102.85.28 (talk) 15:09, 5 March 2008 (UTC)

Tetraethyl lead could be drawn as a swastika , but as above in 3D it doesn't have this structure.87.102.85.28 (talk) 16:03, 5 March 2008 (UTC)

Lots of metal-centered things do have square-planar geometry though...just gotta find the right ligand/metal combination. Maybe tetraethyl platinum, or Pt(OH)₄? DMacks (talk) 18:01, 5 March 2008 (UTC)

Pt(OH)₄ sounds promising since hydrogen/oxgygen bonding interactions would tend to cause the H's to point towards the O's in the plane of the molecule, does it exist?87.102.85.28 (talk) 18:14, 5 March 2008 (UTC)

Pt(OH)₄ exists both as a neutral Pt(IV) compound and apparently also as the Pt(II) dianion. Lots of known chemistry, but I can't find structural data. Many uses involve adding additional ligands and many 4-small-legand complexes of Pt are square-planar, so my SWAG is square-planar at Pt. I hadn't thought of the H-bonding helping the arms stay in the correct orientation, good idea! DMacks (talk) 18:38, 5 March 2008 (UTC)

rodents with large binocular field of view

Hi everyone. A simple question, but the search yielded nothing for some reason. The question is: are there any rodent species with a decent binocular field of view (FOV)? Most rodents have eyes set far off to the sides of the skull, hence the FOV of both eyes overlap only over a small angle (a few degrees AFAIK) in front of the animal. That, of course, makes sense: rodents have a large number of predators to watch out for, and therefore large coverage, even monocular, is more important than binocular vision. Still, do you know which rodent or lagomorph species have a relatively large binocular frontal FOV? Thanks in advance. --Dr Dima (talk) 06:44, 5 March 2008 (UTC)

Ferrets? They have eyes close to the front. —Preceding unsigned comment added by 84.68.70.170 (talk) 01:15, 6 March 2008 (UTC)

Ferrets aren't rodents. They're carnivores, who eat rodents, among other things. Mattopaedia (talk) 02:36, 6 March 2008 (UTC)

If it had this binocularity, would it still be a rodent? Julia Rossi (talk) 07:08, 6 March 2008 (UTC)

Yes, Julia, I think it would. AFAIK, defining features of Rodentia are the particular anatomy and physiology of teeth, jaws, and palate. A small binocular frontal FOV is not a defining feature of rodents, as it also occurs in Lagomorpha. Still, thank you for an interesting thought. --Dr Dima (talk) 20:00, 6 March 2008 (UTC)

relative calcium absorption into bones compared to teeth

I've read somewhere that 99% (or some other very high percentage) of calcium absorbed into your body is in your teeth, while only 1% goes to your bones. Can anyone verify this? Mitchell Cain (talk) 08:26, 5 March 2008 (UTC)

This paper states that 99% of the body's total calcium is in bone (but I suspect they are using "bone" to mean "bones and teeth", as prior animal studies use the figure 99% for bones & teeth). I don't find a reliable source differentiating teeth vs bones (but this retailer of calcium says teeth contain 1% of total body calcium, which seems reasonable: the calcium content of tooth and bone are similar (by weight), and all your teeth taken together weigh considerably less than all your bones taken together.) So I suspect that either you misunderstood what you read, or it was just plain wrong. - Nunh-huh 10:01, 5 March 2008 (UTC)

Another way of looking at it is that the human body is about 1.5% calcium by weight, so a 150-lb person would have about 2¼ pounds of teeth in her head, which seems rather high. --Sean 14:30, 5 March 2008 (UTC)

Physics

Can Kgf be used as a unit for Force in place of Newton. To be specific if I say that an aircraft wieghs 6000 kgf, does it mean 6000 N or 6000 x 9.81 N? Shary249900 (talk) 13:52, 5 March 2008 (UTC)

The latter is closer to correct. 6000 kgf = 9.80665 m/s² x 6000 kg = 543999 N. See kgf. jeffjon (talk) 14:04, 5 March 2008 (UTC)

Free protons? Free neutrons?

Free electrons are described as electricity. What would free protons and free neutrons be described as? 64.236.121.129 (talk) 15:37, 5 March 2008 (UTC)

How about dangerous?

Seriously though, a free proton is an ion of Hydrogen, that is a Hydrogen atom that's lost its electron. You can get neutron radiation, but other than that neutrons don't tend to hang around on their own. They decay into protons. —Preceding unsigned comment added by AlmostReadytoFly (talk • contribs) 15:55, 5 March 2008 (UTC) Damn! SineBot doesn't give you much chance! AlmostReadytoFly (talk) 15:56, 5 March 2008 (UTC)

Did you really think you could beat a robot? 206.252.74.48 (talk) 16:22, 5 March 2008 (UTC)

(ec) While electric currents definitely do involve electrons (well, usually), the situation is much more complex than a bunch of free electrons wandering down a wire. Signals in a metallic wire travel much faster (close to the speed of light) than the individual electrons that carry the current (drift velocity about a millimeter per second). (See also speed of electricity). The very same electrons that are 'free' in the sense of being able to move in a conduction band down the length of a wire don't just fall out the end of the cable when you unplug it—they're bound.

A 'free' electron – one not bound to other matter – might be called a cathode ray in some contexts, or a negative beta particle in others. Really though, a 'free electron' wandering about with relatively small kinetic energy is usually described as just that—a 'free electron'.

As an aside, when I saw the section header on this question my first thought was that there was some sort of giveaway of particles going on. Cheers! TenOfAllTrades(talk) 16:27, 5 March 2008 (UTC)

Whereas I thought someone was scrounging :P AlmostReadytoFly (talk) 16:32, 5 March 2008 (UTC)

There used to be a donut shop near UC Berkeley called the "Neutron Bakery" (no doubt a name left over from an earlier period of nuclear enthusiasm). I tried to convince the then-current owner once that they should give away some donuts for "no charge" but they didn't get it. Sigh. --98.217.18.109 (talk) 17:03, 5 March 2008 (UTC)

I absolutely hate it when a great joke falls through like that. You have my deepest sympathy. 206.252.74.48 (talk) 19:46, 5 March 2008 (UTC)

I mean free protons and free neutrons. Not binded together. A Hydrogen atom that lost an electron still has a proton and a neutron. I'm talking about free protons and free neutrons, unbinded. 64.236.121.129 (talk) 16:26, 5 March 2008 (UTC)

No it doesn't usually. A Deuterium atom (which is a type of Hydrogen atom) has a proton, a neutron and an electron, but most Hydrogen has only a proton and an electron. If it loses the electron, all you have is a free proton. AlmostReadytoFly (talk) 16:32, 5 March 2008 (UTC)

Your standard hydrogen ion is just a proton, as above. Deuterium (a comparatively rare isotope) is the proton+neutron combo. 199.209.144.218 (talk) 16:30, 5 March 2008 (UTC)

There are free protons in the solar wind. But we don't encounter free protons and free neutrons in "everyday life", because their presence is an indication that there are some high energy nuclear processes happening - it takes much more energy to dislodge a nucleon from a nucleus than it does to free an orbital electron. If you find free protons or neutrons flying around, you should probably stand well back. Gandalf61 (talk) 16:40, 5 March 2008 (UTC)

So a free proton is just ionized hydrogen? Ok. What about free neutrons? 64.236.121.129 (talk) 16:56, 5 March 2008 (UTC)

Neutron radiation, as mentioned above. They decay into protons. AlmostReadytoFly (talk) 16:59, 5 March 2008 (UTC)

Yup, as denoted H+ - that's essentially what a proton is. Wisdom89 _{(T / ^C)} 17:49, 5 March 2008 (UTC)

You have to be careful when using H+ because most of the time it is used when in H+ is in water where it is actuall more like H3O+ or H3O+.(H2O)3 or other funky complexes that aren't really fully understood, H+ is just an easy way of treating protons that are loosely bound. Certainly though if you heated HCl gas up you would get free protons. --Shniken1 (talk) 22:43, 5 March 2008 (UTC)

Oh also there is research that I've heard of that uses carbon nanotubes to transport protons to be used as electricity. The direction of Electric charge is actually defined as the direction a positive charge would travel not a negative charge (electron), this because it was defined before the electron was discovered.--Shniken1 (talk) 22:48, 5 March 2008 (UTC)

The sweet taste of deuterium

Does heavy water taste differently from ordinary water? ----Seans Potato Business 18:13, 5 March 2008 (UTC)

I'm not sure about the taste, but I know it can kill you if you drink it. 64.236.121.129 (talk) 18:16, 5 March 2008 (UTC)

That's not exactly true. I just drank it as part of a crazy experiment for which knowledge of my body composition is required. It tasted sweet, but I wonder if that's something else I'm tasting... ----Seans Potato Business 18:18, 5 March 2008 (UTC)

Drinking too much is toxic. 64.236.121.129 (talk) 18:24, 5 March 2008 (UTC)

Heavy water#Toxicity_in_humans says "for a poisoning, large amounts of heavy water would need to be ingested without significant normal water intake for many days to produce any noticeable toxic effects", so it's only really toxic under highly improbably circumstances. Regular water is too, for that matter. --Sean 18:39, 5 March 2008 (UTC)

Well, I think it's a little different. It says on that article that heavy water given to rats to drink for a week, died. If you drink it on a regular basis, it's toxic. You really want to mess with something that might kill you? 64.236.121.129 (talk) 18:46, 5 March 2008 (UTC)

Such experimentation is fairly common. Inhaling helium or sulfur hexafluoride to change the pitch of one's voice is fairly common, even among those who understand the risks, because the associated risk mitigation is also well-understood. Not that I personally am gung-ho to start slurping deuterium, mind you. — Lomn 18:54, 5 March 2008 (UTC)

In all fairness, Helium is non-toxic. It's only dangerous if it displaces oxygen. 64.236.121.129 (talk) 19:09, 5 March 2008 (UTC)

Risk is risk. Do you put toxicity into a special category of risk? If so, why? --Trovatore (talk) 19:25, 5 March 2008 (UTC)

Categories are made by scientists on these matters. 64.236.121.129 (talk) 19:41, 5 March 2008 (UTC)

Discussing risk is entirely a matter of severity, dependent on magnitude and time of exposure. The issue of risk is by no means binary (i.e. toxic vs. non-toxic), and such models are only presented as guidelines so the average Joe doesn't have to figure it out. Bottom line, too much of anything will kill you; too little of some things will also kill you. Once we know the time/concentration needed to cause illness, continuing to argue over the meaning of "toxic" is utterly pointless. Someguy1221 (talk) 19:46, 5 March 2008 (UTC)

How does this contradict what I said? 64.236.121.129 (talk) 21:25, 5 March 2008 (UTC)

"If you drink it on a regular basis, it's toxic. You really want to mess with something that might kill you?" Someguy1221 (talk) 23:53, 5 March 2008 (UTC)

Risk is risk? Won't the actuaries be surprised! --Sean 20:54, 5 March 2008 (UTC)

Would they? What do they think risk is, if not risk? Silly banter aside, the point is that when comparing small risks, the fact that one of them is from toxicity rather than, say, asphyxiation, or car crashes, or whatever, does not make it autmatically more objectionable. --Trovatore (talk) 20:58, 5 March 2008 (UTC)

There is little in the scientific literature on the taste of heavy water, but a few publications exist. There is a public account from Time magazine (4 February 1935) describing Klaus Hansen of the University of Oslo as the first person to consume concentrated heavy water. He consumed "two teaspoons" of heavy water, and reported the experience thus [5]:

"I lifted the beaker to my lips. Immediately I felt a burning dry sensation in my mouth and then I could feel nothing. First my mind became excited and impressed with a feeling of crisis.

I had some shock. Then I said to myself, 'Be quiet—you are simply going through a minor experience.' Then it was all over. I could see, hear, breathe, feel and walk just as before."

The guy was probably just nervous, however. In a letter to Nature (15 March 1935) Harold Urey (recipient of the 1934 Nobel in Chemistry for demonstrating the existence of heavy water) reported on his own experiment. It involved two subjects who each tasted one cubic centimeter of distilled water and an equal volume of heavy water. This test was blinded—a third person outside the room prepared the samples. The final conclusion was that "pure deuterium oxide has the same taste as ordinary distilled water."

A 1976 paper in Experimental Biology and Medicine (CP Richter, "A study of taste and smell of heavy water (99.8%) in rats", 152(4):677-684) describes the odor of heavy water as "faint" in its abstract ([6]), but the full article isn't online. (The abstract also states that "Rats did not taste heavy water", but it is unclear from the context whether it means that the rats were incapable of tasting a difference, or that they chose not to drink heavy water because of a perceived odor.) TenOfAllTrades(talk) 19:18, 5 March 2008 (UTC)

(ec)According to Effects of Heavy Water on Living Cells, Science, Vol. 86, No. 2243, p. 587-588, December 24, 1937, heavy water "seems to exhibit to some people mild and varying differences in taste from ordinary water. He gives a citation to this of K. Hansen, Klin. Wochenschr., 14: 1489, 1935. I'm not quite up to hunting down that citation, but it's something...Someguy1221 (talk) 19:21, 5 March 2008 (UTC)

Helium is actually dangerous because it displaces CO2, which prompts the body to breathe. You will not feel like you need to breathe but you do need to. Heavy water is only toxic when it displaces normal water in cells where it can change the folding of proteins due to weaker hydrogen bonding. (There may be some adverse effects by replacing the extracellular fluid with heavy water but these would be minor in comparison and/or I cannot think of any ATM). But back on topic, I cannot see a reason (other than psychological) that heavy water would taste different--Shniken1 (talk) 22:37, 5 March 2008 (UTC)

To be fair, heavy water could taste different for the same reason that it is toxic at high concentrations. The extra neutron doubles the mass of the hydrogen nucleus, which affects the kinetics of biochemical reactions. In principle I could see exposure to concentrated heavy water affecting the (normally water-equilibrated) taste receptors on the tongue, and generating a response that way. TenOfAllTrades(talk) 01:00, 6 March 2008 (UTC)

One could imagine that heavy water taste identically to normal water but that the difference in the hydrogen bond affect chemical reactions where water take place or the binding of water to other molecules. That way, it could affect taste but only if mixed with something else. But this is just an idea. —Preceding unsigned comment added by 129.241.215.226 (talk) 08:26, 6 March 2008 (UTC)

I have learned that was I drank was 99% heavy water with nothing else added and it tasted very much different. Given samples of regular water and heavy water, I could differentiate between them both every time. Of course this is original research, so I can't fix the article on this basis (which claims absence of difference of taste). You should know however, that I assert that this statement is incorrect. In case it matters, it made me extremely dizzy (I needed to drink 200 mls) and I didn't like it. --Seans Potato Business 20:39, 6 March 2008 (UTC)

Did you know it was heavy water? Taste is probably the most suggestible of the senses. I had this impressed on me in college when I told a girl which Sweet Tarts I liked best and worst, and she challenged me to tell one from another without looking at them. Couldn't do it at all. But I still like the green and purple ones best. --Trovatore (talk) 20:41, 6 March 2008 (UTC)

Yes I did, and I believe that knowledge had nothing to do with it. If someone wants to include me as a subject in a properly controlled scientific experiment and any associated expenses will be covered, then I'd be happy to take part. The taste was very distinctive and not remotely subtle. --Seans Potato Business 22:22, 6 March 2008 (UTC)

I read somewhere that alcohol makes the room appear to spin because it reduces the density of the fluid in the inner ear, and that if you drink heavy water it increases the density and the room spins in the other direction. I was never sure whether to believe it or not, but is that what you meant by dizzy? Eve (talk) 22:48, 6 March 2008 (UTC)

The room was spinning, yes, although I don't know what direction... counter-clockwise? Of course it only seems to spin with my eyes closed, otherwise it spun a bit and went back very quickly over and over. ----Seans Potato Business 17:10, 7 March 2008 (UTC)

Yep! The article on alcohol explains the spinning sensation and eye movement, although doesn't mention the heavy water effect. But it makes sense. Eve (talk) 18:17, 7 March 2008 (UTC)

Have you also tried drinking distilled water? Once you remove the dissolved minerals, the dissolved gases, and similar things from it, ordinary water tastes pretty awful. --Carnildo (talk) 23:09, 6 March 2008 (UTC)

Maybe it was the absence of minerals that made it taste distinctive. I don't know where it came from or how it was treated. Never tasted distilled water before. --Seans Potato Business 17:10, 7 March 2008 (UTC)

Is it true the Wright brothers were mocked?

I heard people made fun of them, and didn't believe that they could achieve what they were trying to build. Is this true? 64.236.121.129 (talk) 18:30, 5 March 2008 (UTC)

Quite so, including well after their first successful flights. Our article on the Wright Brothers notes their efforts to avoid the "circus" of reporters that surrounded early flight attempts. I consider the most interesting example to be that laid out in the "public showing" section, which notes that fully five years after the brothers' original success, the French media still referred to them as "bluffeurs". — Lomn 19:00, 5 March 2008 (UTC)

It was true with many early pioneers of powered flight. Richard Pearse's story in particular is quite a sad one. Grutness...wha? 23:59, 5 March 2008 (UTC)

Color of hemoglobin

What determines the absorption spectra of hemoglobin and its derivatives? Why is HbO bright red and Hb purplish red? --Eleassar ^{my talk} 20:09, 5 March 2008 (UTC)

Here's a little. Hemoglobin#In_history_and_art David D. (Talk) 20:19, 5 March 2008 (UTC)

technically it comes from crystal field theory as the Fe species changes in oxidation state oxidation state the splitting between energy levels changes, changing the optical absorption range, and thus color. 193.60.95.72 (talk) 00:51, 6 March 2008 (UTC)

Not according to the wikipedia article. It says it is the Porphyrin. David D. (Talk) 01:15, 6 March 2008 (UTC)

You haven't 100% understood that, both are true. (Don't answer questions you're not qualified to..)87.102.74.217 (talk) 09:59, 6 March 2008 (UTC)

Huh? I didn't answer the question. I point to the wikipedia article. How about a source for your info and then the article can be improved. David D. (Talk) 10:23, 6 March 2008 (UTC)

easy guys, don't fight. The crystal field theory is modeling the interactions between the Fe ion and the porphyrin. Its not a bare Fe ion floating around... those ARE the ligands interactions that define the color. Furmanj (talk) 18:54, 6 March 2008 (UTC)

Thanks for the replies. --Eleassar ^{my talk} 14:55, 6 March 2008 (UTC)

Nanomedicine

Hi guys... whow do you think the future scenario of nanomedicine is going to be? only the rich and famous having the benefitts? everyone? only the insured? only citizens of the developed countries? will it not be available at all but to a select few who will become supermen of some sort and rule the world?...--Cosmic girl (talk) 22:09, 5 March 2008 (UTC)

I think as with most technology it will be expensive and basic initially - once processing techniques and development comes into play the price will drop, the technology will advance and the consumer base will broaden. I don't expect super(wo)men over-night... maybe 2 nights.Boomshanka (talk) 01:08, 6 March 2008 (UTC)

March 6

Beer and bowel movements

It never fails: After a long night of beer drinking, you have to pass a bowel movement (or several) the next morning. This happens to many people I know. What causes this? Does beer have some kind of laxative effect? I've searched around on the web and not found a satisfactory answer (various answers contradict each other). Thanks! 210.239.12.85 (talk) 01:28, 6 March 2008 (UTC)

Ethanol has a direct effect on urine output by inhibiting Antidiruetic hormone - with regards to bowel movements however, when you excessively drink that much you are actually creating an osmotic diarrhea effect. Wisdom89 _{(T / ^C)} 01:31, 6 March 2008 (UTC)

Thanks for the reply, but I'm not sure I understand you. What is an "osmotic diarrhea effect"? Thanks! 210.239.12.85 (talk) 02:34, 6 March 2008 (UTC)

Osmotic diarrhea is diarrhea caused by non-resorbable solutes within the bowel. These solutes pull water into the lumen of the bowel, and diarrhea results. Our article on diarrhea mentions this, but doesn't go into much more detail. - Nunh-huh 02:39, 6 March 2008 (UTC)

D'Oh! Edit conflict. I was going to say much the same thing, but point the dear reader to osmosis and osmolarity to explain how water gets pulled into the bowel. Since its non-resorbable there's only one way for it to go.... grog-bog! Mattopaedia (talk) 02:45, 6 March 2008 (UTC)

Osmotic diarrhea. Just another reason for me not to drink. HYENASTE 21:18, 6 March 2008 (UTC)

Drinking. Just another reason to learn to enjoy osmotic diarrhea. - Nunh-huh 08:00, 7 March 2008 (UTC)

Quick physics questions

This isn't homework or anything, just stuff that stemmed from a discussion me and a friend were having. So, objects accelerate at the same speed regardless of mass(right??), but will the heavier one eventually gain more speed? —Preceding unsigned comment added by 166.217.186.49 (talk) 01:30, 6 March 2008 (UTC)

Yes, you're right about the acceleration. But, nope, the only time the speed would be different is if the objects you're comparing have a difference in their aerodynamics. Wisdom89 _{(T / ^C)} 01:33, 6 March 2008 (UTC)

(ec) In general, objects do not accelerate at the same speed. Newton's Second Law of motion states that F=ma, or force equals mass times acceleration. Therefore, for two objects experiencing the same force, the heavier one will accelerate less. Where you're probably getting confused is with gravity. For gravity, the amount of force one body exerts on the other is proportional to their masses. So for gravitational acceleration towards a given object (say the earth), the force exerted on a massive object will be more than that on a lighter object - in fact, it's proportional to the mass. With the force being proportional to mass, and the acceleration due to that force being inversely proportional, the mass terms cancel out, and the acceleration due to gravity is independent of mass. Now acceleration is simply the rate of change of velocity. This relation has no dependence on mass. Two objects starting from the same initial velocity, and experiencing the same acceleration will always have the same final velocity, no matter how long the acceleration lasts. Although they have the same speed, they will have very different energies, though. Kinetic energy (the energy of motion) is equal to 1/2 * m * v². Although the velocity (v) is the same, the mass (m) of the heavier object is greater, giving it greater kinetic energy. (This is why a bowling ball hurts more than a marble, even when dropped from the same height). -- 128.104.112.47 (talk) 01:45, 6 March 2008 (UTC)

Just a comment, I suppose I just assumed that the user was referring to acceleration due to gravity in his/her question. Wisdom89 _{(T / ^C)} 02:49, 6 March 2008 (UTC)

Ah, thanks alot, I was indeed referring to gravity. And you actually answered what we were originally discussing, about more massive objects having greater gravity and if that would effect the speed at which they "fall", or are attracted(Gravity works both ways in that sense, right? that both objects are attracted to each other, just the less massive one is the one that moves). —Preceding unsigned comment added by 166.217.186.49 (talk) 03:15, 6 March 2008 (UTC)

In the simplest case, a two-body system, both objects will move towards their combined centre of mass. But, in the case of, say, a system consisting of the Earth and a basketball, said combined centre of mass would be a few millimetres away from the Earth's centre of mass, and the amount the Earth gets accelerated is so small that if you just shift to a frame of reference where the Earth doesn't move, there's no detectable difference. When the two bodies are of similar mass, it becomes more noticeable (this is actually how most planets outside the solar system have been discovered, more or less). Confusing Manifestation(Say hi!) 04:57, 6 March 2008 (UTC)

So the general answer to the question is that, for two geometrically identical bodies differing only in mass, the lighter body will gain the greater speed in free space (without other gravity), but the heavier one will gain greater speed if they fall in air under Earth's gravity (because the identical air resistance is a greater proportion of the weight of the lighter body). Only under Earth's gravity in a perfect vacuum will they fall at the same speed. dbfirs 08:57, 6 March 2008 (UTC)

As a quick reminder of the magnitude of the Earth's mass, the presence of a basketball on the Earth's surface shifts its centre of mass by about one two-thousandth of the radius of a proton. Algebraist 15:40, 6 March 2008 (UTC)

Horizontal Pressure Gradient

Hello. Why is there a fast wind when the lines of constant (equal atmospheric) pressure are close together? Thanks in advance. --Mayfare (talk) 01:42, 6 March 2008 (UTC)

When isobars are close to each other, that means that a high and low pressure regions are close to each other. Air (like all gases) would prefer to equalize pressure, so the air from the high pressure region rushes toward the low pressure region. The reason you get a faster wind with close isobars versus distant isobars is the same reason water flows faster down a steep hill than down a gentle slope (where you have close topographical lines versus distant topographical lines). Note that even though the air wants to move from high pressure to low pressure, the wind doesn't always make a straight line path, due to the Coriolis effect. -- 128.104.112.47 (talk) 01:54, 6 March 2008 (UTC)

Bitter chemical in broccoli

I overheard a casual discussion the other day that two fellow students were having in the lounge. Apparently there is a bitter tasting chemical in broccoli and some other foods that is only detectable by ~20% of the population. In their chemistry lab, they had the opportunity to apply this chemical to a stick and press it onto their tongues to see which of them were sensitive to this chemical. Does anyone have an idea what the chemical was? The articles on supertasters and broccoli didn't yield any answers. BigNate37_(T) 01:47, 6 March 2008 (UTC)

Does bitter (taste) have the answer? --Tardis (talk) 01:56, 6 March 2008 (UTC)

You know I didn't even read that section, and the first hit of my broccoli-chemical-bitter Googling took me to the taste article where I promptly learned of umami for the first time. Taking a look, it's likely phenylthiocarbamide, although the ratio seems to be the inverse of what I heard. That's easily attributable to a miscommunication of that interesting yet trivial detail, though. Thanks! BigNate37_(T) 02:04, 6 March 2008 (UTC)

I don't think its PTC. I can taste PTC, yet I don't find broccoli bitter. HYENASTE 05:27, 6 March 2008 (UTC)

I don't know about you, but broccoli bitterness doesn't taste like PTC. When it's well cooked, I don't taste any bitterness, but when it's badly cooked, I find it unpalatable. PTC on the other hand tastes god-awful. bibliomaniac15 I see no changes 06:03, 6 March 2008 (UTC)

Asparagus has a similar property where it produces methyl mercaptan in everybody's urine, but only a certain percentage of the population can smell it. It's interesting how natural selection allows these kind of sensory deficits on the unimportant margins, but ensures that almost everyone can detect an onrushing sabre-toothed tiger. :) --Sean 13:51, 6 March 2008 (UTC)

Also, Harold McGee's masterful On Food and Cooking says the broccoli harshness comes from isothiocyanates metabolized from glucosinolates (page 321 in this edition). --Sean 14:02, 6 March 2008 (UTC)

Then there's the bitter zucchini (eggplant, cucumbers and varieties of summer squash) thanks to Cucurbitacin E which I take it, is unmissable, not a matter of conditions, but a rogue compound (?) and not nice to the point where local authorities wanted to round them up.[7] Could everyone taste that? Julia Rossi (talk) 22:55, 6 March 2008 (UTC)

Regarding glucosinolates, vegetables, and genetics, here's another article for you to check out: [8] It appears to be what you are referring to. Dforest (talk) 04:58, 7 March 2008 (UTC)

Chemical compositions of some animal products/byproducts used in early warfare

I am currently working on Early thermal weapons, following a discussion some days back about the use of boiling oil and quicklime during sieges. In my final section I'm trying to show how the weapons were later developed or have modern equivalents (eg Arabic Greek fire had naphtha which is now used in napalm). Anyway, I have discovered some intriguing uses of animal products. Horses' hooves, egg yolks, and pigeon and sheep droppings were used in incendiary mixtures. What chemical/property would these have which is desirable in explosive/incendiary mixtures? (Are pigeon and sheep droppings as useful as guano??) In addition, some folks besieged by the Romans drove them off by burning chicken feathers, producing such a noxious smoke the Romans had to abandon their mining attempts. What's going on here? Gwinva (talk) 03:42, 6 March 2008 (UTC)

Animal dropping may be high in nitrate eg guano - which will cause more vigorous burning, they may also produce an unpleasent smoke when burnt.

Egg yolk i'd guess are there to make the liquid more sticky.

found this http://www.tennessee.gov/environment/tn_consv/archive/PrescribedFire.pdf "Native Americans practiced chemical warfare. Bundles of Poison Sumac or other poisonous plants were burned upwind of the enemy, having severe effects on the attacking force." similar to chemical weapons, I've heard of similar examples using burning plants containing alkaloids to similar effect eg henbane , deadly nightshade

Burning feathers/hair really stinks - as everyone knows - imagine a lot of it - I'd retreat - at least temporarily...compare tear gas87.102.74.217 (talk) 12:19, 6 March 2008 (UTC)

Some may be covered in Chemical_weapons#History87.102.74.217 (talk) 13:40, 6 March 2008 (UTC)

Horse hooves make glue, of course, which is unrefined gelatin. All sorts of excreta would be useful in making potassium nitrate, and I guess that any chemical reaction tending that way would enhance the combustibility of a mixture containing it. --Milkbreath (talk) 20:39, 7 March 2008 (UTC)

Familiar PTC flavo(u)r

Inspired by the broccoli question from above. Does anyone who can sense phenylthiocarbamide agree that it tastes a lot like earwax? HYENASTE 05:06, 6 March 2008 (UTC)

What does earwax taste like?--Shantavira|^{feed me} 08:42, 6 March 2008 (UTC)

And given what it likely tastes like, do two earwaxes taste the same? Julia Rossi (talk) 12:43, 6 March 2008 (UTC)

There's only one way to find out:

"We have to learn again that science without contact with experiments is an enterprise which is likely to go completely astray into imaginary conjecture." — Hannes Alfven (from Experiment)

AlmostReadytoFly (talk) 15:24, 6 March 2008 (UTC)

Shantavira, surely you have enough ears and fingers to determine this for yourself. HYENASTE 21:22, 6 March 2008 (UTC)

Aromatic Hydrocarbons and PVC or Polyethylene

I see from the article on polyethylene that "Polyethylene (other than cross-linked polyethylene) usually can be dissolved at elevated temperatures in aromatic hydrocarbons, such as toluene or xylene, or chlorinated solvents, such as trichloroethane or trichlorobenzene." Does anyone know what "elevated temperatures" are meant and whether polyethelene is safe to use as a container for aromatic hydrocarbons (Heptane, Hexane, Toluene, Xylene) at room temperature without degrading the container or contaminating the hydrocarbons? Similarly I'd like to ask the same question in relation to pvc, Polyvinyl chloride and enquire which would be the better to use?

Thanks AllanHainey (talk) 08:34, 6 March 2008 (UTC)

Can't give you the temperatures.

In chemistry PE is not a suitable container for hydrocarbons because of contamination, nor is a PVC container - at least if you wish to keep the liquid free from contamination. This is important for some chemical processes..

However it can be used. The higher the molecular weight of the polymer the better. Some petrol cans are plastic.

You might want to compare high density PE and low density PE87.102.74.217 (talk) 09:56, 6 March 2008 (UTC)

You best choice would be glass, also PVA or similar coatings can act as a hydrocarbon barrier in some cases.87.102.74.217 (talk) 11:26, 6 March 2008 (UTC)

Thanks, I'm asking in relation to a the material a siphon should be made of for siphoning these hydrocarbons - all I've seen available is PE & PVC. AllanHainey (talk) 11:45, 6 March 2008 (UTC)

If you're syphoning for say a car or to be mixed into some paint etc then you should be ok as long as the material you use is specified ok for petroleum. HDPE should be ok, LDPE not ok. PVC is different because it sometimes contains plasticisers which are easily dissolved.

The big problme comes when doing analytical work because even a small amount of dissolved plastic can mess up the process later on.

Even HDPE can swell up when exposed to organic solvents.

I can only suggest you use a pipe that is clearly stated to be safe to use with the liquid you are using87.102.74.217 (talk) 12:13, 6 March 2008 (UTC)

Ostrich fossil range

What is the fossil range of Struthio camelus? I mean only this species, not the entire Struthio genus. Thanks. -- Leptictidium (mammal talk!) 11:57, 6 March 2008 (UTC)

From Ostrich#Evolution - "The earliest fossil of ostrich-like birds is the Central European Palaeotis from the Middle Eocene, a middle-sized flightless bird that was originally believed to be a bustard. Apart from this enigmatic bird, the fossil record of the ostriches continues with several species of the modern genus Struthio which are known from the Early Miocene onwards." -- MacAddct  1984 ^{(talk • contribs)} 14:15, 6 March 2008 (UTC)

Thanks, but that still refers only to the genus Sruthio, not to the species S. camelus. Struthio may date from the Miocene, but S. camelus itself may have appeared later on. -- Leptictidium (mammal talk!) 15:27, 6 March 2008 (UTC)

Oh, I apologize, I read that as "I mean not just this species, the entire Struthio genus." The exact opposite of what you meant.... v_v -- MacAddct  1984 ^{(talk • contribs)} 16:35, 6 March 2008 (UTC)

Atmospheric (unit) vs. Bar (unit)

If bar is barometric pressure, then why is it not equal to atmosperic pressure? A bar = 14.504 psi, but the atmosphere is defined as 101,325 Pa which = 14.696 psi —Preceding unsigned comment added by 160.84.253.241 (talk) 14:21, 6 March 2008 (UTC)

See Bar (unit) it is about the same as atmospheric pressure, not exactly the same..87.102.74.217 (talk) 14:54, 6 March 2008 (UTC)

Kylstron or RF cavity

What is the large copper ball, I understand that the copper tube is an RF cavity used in particle accelerators, and had assumed therefore that the copper ball was some form of klystron, however, it seems unlike any other klystrons I have seen, and also on Howstuffworks an diagram (thoguh specificalyy of SLAC) implies that some depth of earth is recquired to be between the klystron and the actual RF cavity, this would imply that it having it so close would cause some sort of problem. So is it a klystron, or is it simply some sort of addition to the RF cavity.

Also why is it important that the klystron is seperated from the beam line by such a depth? —Preceding unsigned comment added by 81.140.151.57 (talk) 17:09, 6 March 2008 (UTC)

Synchrotron radiation

does anyone have some good resources on the maths of Synchrotron radiation, on sorts of things as the energy lost by a certain energy particle when forced through a known radius and length bend, and also the intensity, frequency of the synchrotron light. thanks —Preceding unsigned comment added by 81.140.151.57 (talk) 17:14, 6 March 2008 (UTC)

This topic is woefully under-linked and under-covered in wikipedia. Griffith's Electrodynamics is an excellent textbook reference which has all the answers on this topic. However, there is some information on wikipedia. The article Brehmsstrahlung has some information, but for some reason, no information about radiation due to charges accelerating perpendicularly to their velocities (perhaps I'll try to remedy that in the future). The article Cyclotron radiation (which is radiation specifically from a charge in a magnetic field) is probably closest to what you're looking for, but it isn't very detailed, and there is no derivation. Feel free to come back here if you want more specific help. --Bmk (talk) 17:47, 6 March 2008 (UTC)

One good book is Rybicki & Lightman, Radiative Processes in Astrophysics (ISBN 0471827592). It's ridiculously expensive per ounce, so maybe try a university library. It's a standard text in astrophysics and shouldn't be hard to find. -- Coneslayer (talk) 18:25, 6 March 2008 (UTC)

I found this it is useful, but seems very specific to electrons, it be used for any particles?(what consant is K, is it the invers of the permiability of free space or something) —Preceding unsigned comment added by 81.140.151.57 (talk) 09:13, 7 March 2008 (UTC)

That gives the formula for an electron accelerated perpendicularly to its velocity. It can easily be generalized to any charged particle by taking e to be the charge of the particle. --Bmk (talk) 04:27, 11 March 2008 (UTC)

Perigee

At what time of year does the moon reach perigee? Autumn? —Preceding unsigned comment added by 71.174.25.42 (talk) 17:33, 6 March 2008 (UTC)

The article Orbit of the Moon has a lot of information about this type of thing. The "anomalistic month" is the time from one lunar perigee to the next. The anomalistic month is only 27.6 days, so the moon reaches perigee just about 12 times a year. Does that answer your question? PS: If you're curious about what perigee looks like, the moon at perigee appears 14% wider than the moon at apogee! --Bmk (talk) 17:54, 6 March 2008 (UTC)

Also, since Earth's solar year and the moon's revolutionary period are not locked into integer multiples of each other, the "season" varies from year to year. Incidentally, this is why some cultures (e.g. Jewish calendar, Islamic calendar) have calendars which do not fit well at all into a 365-day solar year. Nimur (talk) 19:40, 6 March 2008 (UTC)

What is "Free-space Laser Communication"?

Hi! I want to know about "Free Space Laser Communication". I have tried searching it on the internet, but nothing valuable could come out....I need to know it from scratch....from the very beginning. And please plrovide all details possible of what is it, why do we use it, and how is it done etc. Please help me out. Please. ~~~~

Our article on the subject is Free Space Optics. The key bit of this -- "Free Space" -- indicates that there is no solid medium through which the communications are routed (versus the optical fiber used in fiber optics). — Lomn 19:01, 6 March 2008 (UTC)

You may find the phrase "wireless optical communication" more useful when searching. This textbook appears to be the standard introduction, but it may presume some intermediate level communication theory. Nimur (talk) 19:46, 6 March 2008 (UTC)

I should note that my terminology includes non-laser systems, such as IrDA. If you're not clear on what a laser is, you should read that article too! Nimur (talk) 19:51, 6 March 2008 (UTC)

March 7

multivitamins smell bad?

Why do most multivitamin tablets smell so bad?--Sonjaaa (talk) 01:16, 7 March 2008 (UTC)

Usually the B vitamins are responsible for the smell of multivitamins. [9][10] Dforest (talk) 01:48, 7 March 2008 (UTC)

Obvious follow up question: Why? The entries makes no mention of odors or smells. --70.167.58.6 (talk) 22:36, 9 March 2008 (UTC)

Smelly wet dogs

Why do dogs smell worse when they're wet? When they are dry they usually smell fine, but when they get wet a very distinctive, "wet-dog" odor that seems to permeate everything (it's quite stinky in my opinion) and I was wondering why exactly this happens. Thanks! --71.98.14.31 (talk) 23:48, 6 March 2008 (UTC)

According to the following study, some amount of change in odor results from the different partition coefficients when water is added to the hair. However, "the variety of differences indicates a probable chemical or biochemical reaction on the hair." Compounds Responsible for the Odor of Dog Hair Coat This appears to suggest that an increase in bacterial activity is a likely culprit. Dforest (talk) 05:20, 7 March 2008 (UTC)

Does an OH group make a molecule polar

Does an -OH make a molecule polar? Thanks. —Preceding unsigned comment added by Legolas52 (talk • contribs) 05:48, 7 March 2008 (UTC)

It almost always would as the H atom develops a positive charge and the O atom has lone pairs of electrons with a negative charge. Examples re water ethanol hydroxylamine hydroxyl glycerol glucose. All these are polar. Graeme Bartlett (talk) 08:45, 7 March 2008 (UTC)

For very large molecules, such as cholesterol or free fatty acids, hydroxyl and carboxyl groups can make one end of the molecule polar and while the other remains non-polar (this combination is known as being amphipathic). This is especially important in biological cell membranes. (EhJJ)^TALK 12:31, 7 March 2008 (UTC)

The only way a molecule could be non-polar and have OH groups is if the OH groups were arranged symmetrically around a centre of inversion - can't think of an real example of this maybe something like HO-CC-OH (triple bond in middle)87.102.83.54 (talk) 12:46, 7 March 2008 (UTC)

Must ... resist ... polar ... HO-HO-HO ... joke. --Sean 15:16, 7 March 2008 (UTC)

In addition to the doubtful non-polarity of HOCCOH (ethyne glycol) should it even exist (the angle between O-H bonds can freely rotate, ruining the perfectly zero dipole moment), if you're discussing polarity to guess something's solubility in water, you also have to consider hydrogen bonding. A chemical capable of making hydrogen bonds (by having hydrogens on fairly electronegative atoms, or lone pairs on electronegative atoms involved in fairly polar bonds) will generally be miscible with water even in the absence of a dipole moment. It will just generally suck at dissolving salts. Someguy1221 (talk) 15:33, 7 March 2008 (UTC)

definitely not. Its certainly possible to stick OH groups in a non-polar molecule. Not common, but thats not a safe rule to go by either. Furmanj (talk) 01:22, 8 March 2008 (UTC)

Depending on the chemistry of the rest of the molecule, it could or could not, as Fur indicates above. However, a hydroxyl group will give the compound resident/local polarity due to hydrogen bonding with aqueous solution/polar solvents. Wisdom89 _{(T / ^C)} 03:09, 8 March 2008 (UTC)

Tumors

Do all malignant tumours neccessarily lead to cancer? Why or why not?

Disclamier: This is neither for a competition nor for homework. —Preceding unsigned comment added by Invisiblebug590 (talk • contribs) 08:25, 7 March 2008 (UTC)

Any tumor that is malignant is, by definition, cancerous. If a tumor is not cancerous it is benign. Some benign tumors will develop into cancer. Someguy1221 (talk) 08:33, 7 March 2008 (UTC)

Neat answer. Richard Avery (talk) 08:43, 7 March 2008 (UTC)

On the other hand, not all malignant tumors lead to death. Our watchful waiting article doesn't specifically mention this, but that strategy can often be the best one for an elderly patient with relatively non-aggressive prostate cancer (as mentioned in that article here).

Atlant (talk) 13:04, 7 March 2008 (UTC)

conservation of energy

suppose a balloon is kept in air so that it rises and both it's kinetic as well as potential energy increases. how is the Conservation of Mechanical Energy conserved here ? --scoobydoo (talk) 12:19, 7 March 2008 (UTC)

Its potential energy may increase but at the same time a corresponding but heavier equal volume of air is descending and the potential energy of the air is decreasing. --BozMo talk 12:29, 7 March 2008 (UTC)

Expanding on BozMo's explanation: if the balloon has mass m₁ and the equivalent volume of air has mass m₂ then the net upwards force on the balloon is (m₂ - m₁)g. If the ballon ascends a distance h then it will be travelling at a velocity v where v²=2(m₂ - m₁)gh/m₁. At the same time, a mass m₂ of air has been displaced downwards by a distance h. So we have

Kinetic energy gained by balloon = m₁v²/2 = (m₂ - m₁)gh

Potential energy gained by balloon = m₁gh

Potential energy lost by displaced mass of air = m₂gh

so k.e. gained by balloon + p.e. gained by balloon - p.e. lost by displaced air = 0 and we have conservation of energy. Gandalf61 (talk) 16:30, 7 March 2008 (UTC)

WARFARIN USE

Medical question removed
If you would like to know about warfarin, click on the blue link. But Wikipedia does not give out medical advice. If you are concerned about a friend or relative's medication, I would highly suggest you direct your questions to the prescribing doctor. Someguy1221 (talk) 16:00, 7 March 2008 (UTC)

Metal specs

what is the differance between a vascomax300cmetal and a maragin300c metal? 65.218.254.135 (talk) 18:52, 7 March 2008 (UTC)RUBEN

Vascomax appears to be a registered trademark name for maragin steel see http://www.maraging.com/maraging.html

Is there some reason that prevents you typing 'vascomax' or 'maragin' into a search engine?87.102.93.198 (talk) 11:08, 8 March 2008 (UTC)

somatic cell hybrid panel

Chromosome mapping of the DRM gene A somatic cell hybrid panel (Oncor) was hybridized with a 32P-labeled 1.2-kb human 5) DRM cDNA fragment according to the manufacturer’s protocol.

What is a 'somatic cell hybrid panel'? ----Seans Potato Business 19:56, 7 March 2008 (UTC)

My guess is dot blot panel of DNA from different rat or mice cell lines which include known portions of human chromosomes. The cell lines would be made by fusing human cell lines with mice/rat cell lines by somatic hybridisation. David D. (Talk) 21:45, 7 March 2008 (UTC)

graphite

when i took a stick of graphite and wraped wires on ech end and sent a current through it it began smoking and it looked wet. but it wasn't melting, was it? wat was it doing? —Preceding unsigned comment added by Steweydewey (talk • contribs) 23:59, 7 March 2008 (UTC)

Thermal_oxidation? Did it get hot? The smoke was likely solid carbon dust in a flow of CO and CO2 coming off. If you did the same thing in a vacuum or under an inert gas this wouldn't happen. Furmanj (talk) 01:08, 8 March 2008 (UTC)

Are you sure it was pure graphite? If you used a pencil lead, then it probably contained powdered graphite mixed with clay and glue. The glue would have melted and smoked. --Heron (talk) 14:24, 8 March 2008 (UTC)

March 8

sodium azide

wat are the exact steps in making this? do u mix the chemicals in water,ect. —Preceding unsigned comment added by Steweydewey (talk • contribs) 00:04, 8 March 2008 (UTC)

please read sodium azide first. Furmanj (talk) 01:09, 8 March 2008 (UTC)

Just a word to the wise. If you plan on actually making sodium azide, please be careful with it. Wisdom89 _{(T / ^C)} 03:10, 8 March 2008 (UTC)

ok,ok but can i get measurments?? —Preceding unsigned comment added by 76.14.124.175 (talk) 05:56, 8 March 2008 (UTC)

Despite its common use in airbags, sodium azide appears to be a fairly toxic substance that requires careful handling. If your only resource for relevant information is Wikipedia, then you probably shouldn't be trying to make it. Gandalf61 (talk) 10:10, 8 March 2008 (UTC)

It's not just fairly toxic. It's highly toxic, and death can (and has) occurred with the ingestion of as little as a milligram. Seriously, don't mess with this stuff. – ClockworkSoul 19:27, 8 March 2008 (UTC)

The Massive Multiverse Question

I'm not a nuclear physicist in any way but there is something that I can't shake from my mind. The multiverse. Is the Multiverse purely a hypothetical concept or is it something that exists (or could exist) in reality? I understand that everytime I make a decision, whether to turn left or right for example, a new universe is born. This seems bonkers to me, billions of people spawning trillions of universes. Is this really possible? I guess my question is... Is the multiverse theory something that just fits the equations and balances out the maths or is it a true, physical possibility for the reality that we live in? Do the multiverses ever overlap? Could I ever meet myself? I have a feeling that this question is a bit of an argumentative mine field. Any help and explanation (in simple terms!) would be greatly appreciated. Kirk UK —Preceding unsigned comment added by 87.242.131.156 (talk) 00:22, 8 March 2008 (UTC)

what makes you think that this existence is so unique? Or even real? This might make it even worse, but i'll point you to uniqueness and well defined. I know thats somewhat obscure but keep in mind your frame of reference to reality Furmanj (talk) 01:16, 8 March 2008 (UTC)

The many-worlds interpretation is just one possible interpretation of quantum mechanics, most do not create other universes. Basically, at this point, it's purely hypothetical, but is favored among those who think the laws of physics are deterministic (i.e. you can't have a simultaneously "half-alive/half-dead cat", it's either 100% dead or 100% alive, depending on your universe). As for "overlap" or traveling to other universes, I believe that the answer currently is almost definitely not (they're referred to as "non-communicating" parallel universes), but until we know whether it's true or not I don't think it can be ruled out entirely. That brings us to whether it's real or not, and at this point we don't know, and it may be that we never know, but I don't think that will keep us from looking. Hope that helps! -- HiEv 01:57, 8 March 2008 (UTC)

An example I saw a while back at some talk (where I freely admit I was not paying much attention) was ripples in a pool of water. There is the "big bang" as a rock hits the smooth surface of the water. Each ripple emanating from the center is a "world" that exists on its own. The further form the center, the further along the timeline it progresses. Pick a point in time (a specific distance from the center) and watch it. The ripples go past one after the other. Each one is a separate "world" and each one can have completely conflicting choices. So, at a specific point in time you may choose left, you may choose right, you may not exist at all. It depends on which ripple you are talking about. That's about all I picked up from the talk. Perhaps someone else knows what the guy was talking about and can explain it better. -- kainaw™ 02:07, 8 March 2008 (UTC)

I guess you've seen our article on the Multiverse hypothesis? Julia Rossi (talk) 06:12, 8 March 2008 (UTC)

The idea that we are "creating" universes with every choice we make is really quite silly. I think this idea comes from people misunderstanding one way of viewing multiverses in that one could see the differences as differences in choices made. Of course, the infinite number of universes with no life and therefore no possibility of "choices" would still be ifferent from each other and so the real differences between universes has to do with the playout of random events (both microscopic and macroscopic), which then affect choice. — Ƶ§œš¹ _{[aɪm ˈfɻɛ̃ⁿdˡi]} 09:28, 8 March 2008 (UTC)

solar or wood what is best for hot water

Why fire wood water heater is better than solar in winter and rainy season —Preceding unsigned comment added by Joseph-d-alappat (talk • contribs) 03:05, 8 March 2008 (UTC)

Well, since you're discussing specifics, consider how the conditions (rainy or windy) can effect wood heat and solar power. Wood just burns, and solar power is most effective in direct high-angle sunlight. — Lomn 06:15, 8 March 2008 (UTC)

Siamese communication

I have a Siamese cat. Like every other Siamese I know, he has three states: sleeping, eating, and meowing. He has the typically large Siamese vocabulary and expresses himself almost constantly when people are in the room. Obviously, he's doing it to communicate something to us (he doesn't meow at the chair when I'm not there, for example). What I was wondering was - do Siamese cats owned by deaf people meow less? Do they learn that talking doesn't work and try communicating in other means? Besides idle curiosity, it might also shed light on feline intelligence. Matt Deres (talk) 03:28, 8 March 2008 (UTC)

I would test that theory some how. good question. But never underestimate animal intelegence —Preceding unsigned comment added by 76.14.124.175 (talk) 05:58, 8 March 2008 (UTC)

It's not just siamese cats that miaow a lot. One of mine, who is just some form of moggie (probably british shorthair tuxedo cat) likes to miaow a lot, and you can have conversations with him. I have no idea what I'm saying, but he seems to enjoy them. -mattbuck (Talk) 17:24, 8 March 2008 (UTC)

My parents have a cat (generic short hair black cat) that has a toy that is just feathers on the end of a stick. She now picks it up in her mouth, drags it to one of us, drops it, and meows until one of us plays with her. -- MacAddct  1984 ^{(talk • contribs)} 19:52, 8 March 2008 (UTC)

My cats meow when they want food (or are otherwise unhappy), but otherwise seem to talk to each other and not to me. However, there doesn't seem to be much variety in their conversation: it's mostly "where are you?" as best I can tell. --Tardis (talk) 00:02, 11 March 2008 (UTC)

Schrödinger Equation

Can someone please give me an example of the Schrödinger equation with each step, please? Thanks, Zrs 12 (talk) 04:39, 8 March 2008 (UTC)

I'm no scientist, but → Schrödinger equation. --~~MusicalConnoisseur~~ Got Classical? 06:57, 8 March 2008 (UTC)

If you wanted an example of a solution to Schrödingers equation for a specific system, then perhaps the easiest to understand is Particle in a box. You can find a list of Wikipedia articles with analytical solutions for other geometries here. SpinningSpark 14:15, 8 March 2008 (UTC)

How Halbach array works ?

is it necessary for all the magnets of a halbach array to be of same strength ? iwe know every magnet have two poles but in cace of halbach array, the law is violated ; what's the explanation of strange behaviour of halbach array ? —Preceding unsigned comment added by Shamiul (talk • contribs) 05:43, 8 March 2008 (UTC)

See our Halbach array article. It does not mention different strengths, so I would assume that, yes, the magnets in the array are all the same strength. We also have an article on the Halbach cylinder. Gandalf61 (talk) 09:50, 8 March 2008 (UTC)

The Magnet article explains that magnets can have any number of poles, except one, so the Halbach array does not violate anything. Refrigerator magnets are common examples of multipole magnets. --Heron (talk) 13:42, 8 March 2008 (UTC)

what mathematician (von neumann? erdos?) strongl argued for preemptive annihilation of Russia?

What famous mathematician campaigned during the cold war for a preemptive annihilation of russia via nuclear weapons, based on Game theory? Citation? —Preceding unsigned comment added by 79.122.0.69 (talk) 13:55, 8 March 2008 (UTC)

According to the von Nuemann article he was in favour of a pre-emptive strike to prevent the USSR developing nuclear weapons. However, Game Theory is not mentioned in the article. SpinningSpark 14:30, 8 March 2008 (UTC)

Yeah I'd go with Von Neumann. He was very hawkish, and remember that he died while the US still had a massive nuclear lead over Russia. --98.217.18.109 (talk) 14:57, 8 March 2008 (UTC)

As for a citation, Steven Heims says Von Neumann as an advocate of preemptive war at least around 1950 (when, as I note, it was still feasible, as the USSR only had a bomb or two ready to go), in his book John Von Neumann and Norbert Wiener: From Mathematics to the Technologies of Life and Death. --98.217.18.109 (talk) 15:58, 8 March 2008 (UTC)

It was definitely von Neumann, who had a special hatred of Communists due to his background. He's widely quoted as saying "If you say why not bomb them tomorrow, I say why not today? If you say today at 5 o'clock, I say why not one o'clock?" (refs). Note also that at the time there was a careful distinction made between preemptive war and preventive war, with the latter more extreme position being von Neumann's. Curtis LeMay had similar feelings, along with many other deeply fearful and pessimistic people of that scary new era. --Sean —Preceding unsigned comment added by 69.134.115.242 (talk) 17:21, 8 March 2008 (UTC)

Note that Von Neumann later changed his position. I can't remember the details, but I believe the talk I heard this in to be similar to this (which I can't get to work). Algebraist 17:48, 8 March 2008 (UTC)

Von Neumann's position changed to support of the MAD strategy as the USSR capabilities increased and first strike started to look more dangerous. SpinningSpark 19:21, 8 March 2008 (UTC)

radiation protection

i wnat to design a radiography department in a health care centre wat kind of radiation protection measures should i use and why should i use themRowin.r (talk) 14:34, 8 March 2008 (UTC)rowin.r

I've got to assume here that this is not a practical question (because no one would be given such a job who didn't know about how to do it), but is probably some sort of homework or assignment question. Look at your course materials; any answers we give will probably not be the ones your teacher is looking for. --98.217.18.109 (talk) 14:55, 8 March 2008 (UTC)

We have an article on radiation protection you might want to look at. Bear in mind that only some of the ideas in the article would be applicable to a radiology department. SpinningSpark 17:22, 8 March 2008 (UTC)

Red-eared sliders?

Hi. A friend had wanted me to ask, is it safe to put together two red-eared sliders of different age (eg. one a few months old and one three years old)? What about gender? How much space do they need, if you put two together? Thanks. ~AH1^(TCU) 17:32, 8 March 2008 (UTC)

Quoth this site (used as a reference in our red-eared slider article) [11]:"A hatchling should never be added with adult turtles because of accidental or intentional injuries. Only turtles of a generally similar size with similar habitat requirements should be together in a confined enclosure. "

The site also has other information on keeping red-eared sliders, including this on space: "A guideline to determine this size used by many keepers, as a minimum, is 10 gallons of tank per each inch of shell length (refer to SCL for correct shell measurement). Therefore, a single adult RES will require anywhere between a 90 to a 120 gallon tank."

AlmostReadytoFly (talk) 19:26, 8 March 2008 (UTC)

Blueshifted stars?

Hi. What are all the known blueshifted stars (ones with a negative radial velocity)? This is not homework. Should we have an article such as "list of blueshifted stars" or "list of stars with a negative radial velocity" or "list of stars with decreasing distance"? Thanks. ~AH1^(TCU) 17:37, 8 March 2008 (UTC)

That would be one humungous list, mostly filled with redlinks (does that mean the articles are receding from Wikipedia?). Clarityfiend (talk) 18:02, 8 March 2008 (UTC)

Exploration of the Universe (Abel, Morrison, Wolf) lists 16 amongst the nearby stars. As there are several blue-shifted galaxies out there, the total number of blue-shifted stars is going to be uncatalogable. However, if you would like the data from the tables in this book for an article, drop a note on my talk page and I will provide it. SpinningSpark 18:12, 8 March 2008 (UTC)

There are several blueshifted galaxies? Which are they and are they in the local group? Thanks. ~AH1^(TCU) 18:34, 8 March 2008 (UTC)

According to AMW, the galaxies in the local group with negative radial velocity are; NGC6822, NGC185, NGC205, M32 (NGC221), IC1613, Andromeda galaxy (M31) and M33 (NGC598). As I said, if you want all the figures (velocities, positions etc) for an article, let me know. SpinningSpark 18:48, 8 March 2008 (UTC)

hi guys, I'm just someone else but can you tell me why it's not the case that half of all stars are blue-shifted? it's a toss-up between red and blue shifted, right? There aren't any that aren't shifted are there, by however little.... —Preceding unsigned comment added by 79.122.0.69 (talk) 18:36, 8 March 2008 (UTC)

Not so. The majority of the red shift is caused by the expanding universe and increases with distance dramatically, see Hubbles law. It is only a bit of nearby (local galaxies) local stuff that can be blue shifted and not completely swamped by the universal expansion. SpinningSpark 18:42, 8 March 2008 (UTC)

(edit conflict, my cordless mouse is so f***ed up and slow)Hi. Well, the universe is expanding, so especially the far-away stars and galaxies are moving towards us. Parts of the milky way movement are uneven. It's also likely that if two stars are moving in 3D space in the same direction that most of them will move away from us. Also, I was right that Andromeda and Triangulum are blueshifted! So in an expanding universe, blueshifted galaxies, even close-by ones, mean that they might merge with us, as in the case with Andromeda and Triangulum. Blueshifted stars will soon be redshifted anyway, because they will soon reach minimum distance from us and move away. Redshifted stars will likely continue to be redshifted as they continue to move away. Thanks. ~AH1^(TCU) 18:47, 8 March 2008 (UTC)

Image search related question

Is there any algorithm that search image using image has been develop? For example I would like to search apple image so I'm using an image of apple to find the image that I want. If it has could you provide with some useful links? Thanks. roscoe_x (talk) 18:32, 8 March 2008 (UTC)

yes. what language are you using? —Preceding unsigned comment added by 79.122.0.69 (talk) 18:39, 8 March 2008 (UTC)

Wait, are you saying you want to search for other similar images based on a source image? If so, then I'd say no, or at least I'm not aware of any such search algorithm existing currently. The problem is that computers are really terrible at image recognition at this point, so a computer's idea of "similar" isn't much like a human's idea of "similar". I doubt any search using current technology would do exactly what you're looking for. There is Google Image Search which allows you to search for images using words, but that's not quite the same thing. -- HiEv 19:41, 8 March 2008 (UTC)

Note that to a computer a picture of an an apple is just something round-ish and red. It won't know it's a fruit and it won't know it's edible and it won't know that there are green ones too, or sliced ones, or anything else. It doesn't have the complex range of associations that a human would have. You'd probably as likely find a beach ball in response to your query as another apple. --98.217.18.109 (talk) 20:35, 8 March 2008 (UTC)

I use C, C++, and Java. But I don't intend to develop such a program. I just want to know the algorithm. Every object has pattern, the apple only a sample. The application might be used in finding finger-print, facial recognition, or maybe other useful things. roscoe_x (talk) 01:20, 9 March 2008 (UTC)

You should start with our article on computer vision. If you're looking for a single algorithm to recognize an apple, you're going to be disappointed; computers are dum. That said, here's something neat: take a Google Image Search like say, http://images.google.com/images?q=wikipedia, and add '&imgtype=face to your query: http://images.google.com/images?q=wikipedia&imgtype=face. Neat! Maybe if someone gives you a better answer than me, Google will hire you to implement imgtype=apple. :) --Sean —Preceding unsigned comment added by 69.134.115.242 (talk) 03:00, 9 March 2008 (UTC)

O well that's very cool too. I've check 10 pages and they all giving me correct results. And what amaze me is no mistake and the search result could gives different facial expressions. Do you know the basic? Are they using edge detection? I understand if its classified. Thanks. roscoe_x (talk) 13:37, 9 March 2008 (UTC)

One thing I would think computers could do at this point is find the same image, perhaps at a different scale or color depth. This alone might be useful, if you have a small, greyscale pic and want a large color version of the same thing. Perhaps different cropping, aspect ratios, mirror images, image formats, etc., could also be accommodated. Some of the same technology used to compare fingerprints could be used here. This technology could then be put to use to solve one of the greatest frustrations facing mankind, how to use a nude pic of a celebrity with their naughty bits blacked out to find the original. :-) StuRat (talk) 18:19, 9 March 2008 (UTC)

See OPTIMOL. This is a project out of Princeton that builds a set of images based on a couple of "seed" images of the object class of interest. Sancho 18:54, 9 March 2008 (UTC)

Characteristics of skin Types

I am trying to find the characteristics of the skin type of chinese skin and also black skin. I am learning about skin and the differences of there skin types, other than the colour I cant find anything else. Please help me do my college research. I have done european and asain. but the other two I cant find anywhere on the internet. Beechview (talk) 18:41, 8 March 2008 (UTC)

Hair follicles are part of the skin, so any differences in hair type would also technically be differences in skin type. Beyond that, I don't know. If you look hard enough for differences and can't find them, you could conclude that scientists may not be aware of any. --Allen (talk) 19:03, 8 March 2008 (UTC)

But even if there are no differences beyond skin color and hair texture, there's still a lot to be said on the subject of human skin color. You may also be asking too much of categories like "Chinese skin" and "black skin"... it's really all a big continuum, as the map at human skin color suggests, with a lot of variation at all scales. --Allen (talk) 19:12, 8 March 2008 (UTC)

FYI - If you've done Asian skin then you've already done "Chinese skin", since China is a part of Asia. -- HiEv 19:44, 8 March 2008 (UTC)

Asia is a large group of different people. The OP most likely meant a specific group, such as Japanese. Because he is referring to the skin, I am reminded of one of Bruce Lee's movies where the Japanese refer to the Chinese as "sick yellow men of China" - referring their skin tone. Of course, China itself has a wide variety of people in height, weight, and skin color due a long history of being invaded and, for the most part, absorbing the invaders into the collective whole of the country. -- kainaw™ 02:54, 9 March 2008 (UTC)

Hi. Here's a link if you want to know about the invasion of China and related matters during world war II (warning: potentially disturbing content). Thanks. ~AH1^(TCU) 23:52, 9 March 2008 (UTC)

Adding salt to boiling what-have-you

If adding salt lowers the boiling temperature, why not just cook the stuff at that lower temperature (say 90 or 95 degrees or whatever it may be). What's so special about making the water boil around the potatoes? I think they'll soften just fine at 90 or so sans bubbles. ----Seans Potato Business 18:51, 8 March 2008 (UTC)

Adding salt doesn't lower the boiling point of water; indeed, it doesn't significantly affect the boiling point at all. (The boiling point will be elevated very slightly – less than one degree [12] – with the quantities of salt typically used in the kitchen.)

The addition of salt may, however, affect the flavour or texture of the cooked food. TenOfAllTrades(talk) 19:09, 8 March 2008 (UTC)

Adding salt elevates the boiling point (colligative), which means that the water boils at a higher temperature which means your spaghetti cooks faster.--Mmoneypenny (talk) 00:40, 9 March 2008 (UTC)

No, as Ten points out, the amount of salt added to, say, a pot of water to cook spaghetti in, is not enough to cause any appreciable degree of boiling point elevation. The idea that salt is used in cooking to manipulate the boiling point is simply a wide-spread misconception. The salt is added for taste. If you added enough salt to make a significant difference in boiling point, the food would be so salty it would be inedible. Any (marginal) increase in boiling point from the pinch of salt that's actually used in cooking is incidental and unimportant. - Nunh-huh 05:10, 9 March 2008 (UTC)

It is certainly true that adding salt to a pan of hot, but not quite boiling, water can suddenly produce a rolling boil. Of course, this may possibly be less to do with the salt in solution lowering the boiling point and more to do with the salt crystals providing nucleation sites for the steam to form. SpinningSpark 01:18, 9 March 2008 (UTC)

Adding salt is a lot to do with food colour too. Try purple sprouting brocoli in two pans one with one without salt: the difference is very striking. --BozMo talk 08:25, 9 March 2008 (UTC)

If the addition of salt produces a rolling boil, then the pot of water was actually already above the boiling point of water—at least at the bottom of the pot. Water in the bottom of the pot can become slightly superheated; this process is aided by two factors. First, if the pot is particularly smooth, there will be few nucleation sites around which bubbles can form. Second, if the water is fairly deep and/or is unstirred, hot water can be trapped at the bottom of the container; the weight of the water on top slightly elevates the pressure at the bottom of the pan and thereby also slightly elevates the boiling point.

Agitating the liquid in the pot (to bring hot water to the surface) or providing nucleation sites for bubble formation will both encourage sudden, rapid boiling. Adding salt can drive both processes. (Incidentally, this is one reason to use extreme care in heating mugs or cups of liquid in the microwave. An apparently not-quite-boiling cup of liquid can suddenly boil violently when disturbed: [13], YouTube video.) TenOfAllTrades(talk) 16:39, 9 March 2008 (UTC)

March 9

Animal behaviour

I've read that chimpanzees are pretty violent and often rape and murder one another, and that dolphins kill for fun, although they kill big fish and not other dolphins. Humans are obviously prety violent what with our murdering and our warfaring, so my question is this: discounting territorial disputes, does propensity for violence increase with intelligence among animals? I mean with average species intelligence, not individual cases. And I mean 'senseless' violence rather than mating/food etc related. Thanks 81.96.160.6 (talk) 04:54, 9 March 2008 (UTC)

"Senseless" violence in animals is not really senseless. Just because we don't completely understand the motivation of the animals, does not mean that there is not good biological reasons for it. With regards to chimps that kill and rape, it may be a dominance behaviour, used to establish roles in society. I think its difficult to generalize but among mammals increasing intelligence is generally associated with less violence, since more intelligent animals tend to develop strategies of co-operation and exist in complex social structures. These tend to defuse aggression, rather than stimulate it. Male mice, for example, will robustly attack any other male mouse that happens to wander into his territory. When another guy comes into your house, (I expect) you don't attack him on sight. Rockpocket 09:12, 9 March 2008 (UTC)

If he comes in through the window, uninvited, I sure do. :-) StuRat (talk) 18:01, 9 March 2008 (UTC)

Hi. Remember that chimps have a ⅓ murder rate, meaning that one in three of all chimps become murdered at some point in their lives. Also, sometimes bottlenose dolphins will bully, attack, and kill Dall's porpoises. It may be hard to believe, but that "smile" of a dolphin is actually a threat. Occasionally but very rarely, dolphins might attack humans as well. Chimps are seven times stronger than humans. Humans ususally don't go on these "senseless" attacks because we are generally more civilized and have a code of laws. In fact, some consider the cimps' fighting and killing of monkeys a form of politics. Hope this helps. Thanks. ~AH1^(TCU) 14:36, 9 March 2008 (UTC)

It could be argued that "murder" or the killing of your own species or of other species is part of human behaviour. There are people that train in wrestling and forms of martial arts - it seems to be part of human nature to be capable of this, and in an animal system where it's survival of the fittest and you need to dominate to find a mate, it's part of nature. Humans have similar behaviour - we have sports, and many people do fight (even mock fight) and try to dominate other people physically - of course even psychologically, verbally and sexually. Rfwoolf (talk) 18:50, 9 March 2008 (UTC)

But the mouse does have motivation: it's territorial. I'm not saying it's right, but I mean really killing for fun, like dolphins apparently do. Where there is really no gain. The chimps thing works: social gain is really an intelligence related thing so killing for that sort of maybe demonstrates a link. It just dosn't seem that many "stupid" animals go round getting their kicks from murder. 81.96.160.6 (talk) 19:41, 9 March 2008 (UTC)

DNA sequencing

It seems that before a DNA sequence is sequenced, it is cloned into a plasmid for amplification in bacterial cells, then the plasmid is cut for sequencing. Why can't PCR be used to amplify the DNA for sequencing? ----Seans Potato Business 08:58, 9 March 2008 (UTC)

You can sequence a PCR product also. The problem, though, is that the thousands of amplicons may contain slightly difference sequences due to PCR error which can result in a messier read. Cloned sequences are more likely to be homogeneous. If you want to do something with the DNA after you determine the sequence then you clone it first (since you can't be sure which of the many PCR amplicons you have sequenced), but if you just want to determine what you have amplified, then you can sequence the PCR product without cloning it first. Rockpocket 09:16, 9 March 2008 (UTC)

Generally speaking, a plasmid is not cut before sequencing. In fact, invariably the plasmid is purified and left intact before sequencing with a primer. However, as stated above, one can always sequence a PCR product. And just as a note, PCR and sequencing are fairly similar. There is an extension reaction that needs to take place before the gel fluorescence is read by automated sequencer. Wisdom89 _{(T / ^C)} 14:38, 9 March 2008 (UTC)

Energy

Which of these..(radiation, conduction, convection)...does heat from the sun reach the earth?? —Preceding unsigned comment added by Cassiesirevatarax (talk • contribs) 10:03, 9 March 2008 (UTC)

The answer is in the first sentence of the Sunlight article. --Heron (talk) 10:52, 9 March 2008 (UTC)

Firing on all pistons

What engines can be configured to fire on less than all pistons? ----Seans Potato Business 10:21, 9 March 2008 (UTC)

See Variable displacement and Active Fuel Management. --hydnjo talk 11:52, 9 March 2008 (UTC)

Your internal combustion engine can often work on less than the full number of cylinders, when a spark plug or lead goes bung. Graeme Bartlett (talk) 13:21, 9 March 2008 (UTC)

Would this be damaging to the engine? ----Seans Potato Business 22:28, 9 March 2008 (UTC)

No, but allowing an unburned fuel-air mixture to reach the catalytic converter will cause the converter to overheat and sometimes igniite fires in the surrounding materials. Backfires may also occur in the exhaust system and these can blow apart weak points.

Atlant (talk) 16:32, 10 March 2008 (UTC)

It's not generally a good thing efficiency-wise, because those cylinders are still getting dragged along for the ride while they're not providing useful power. Still, displacement on demand is being actively used and developed by Chrysler among others. Forced induction is a competing approach, from the other direction- this lets you have a small engine that "gets bigger" under load, rather than a big engine that gets smaller under light load. Friday (talk) 16:38, 10 March 2008 (UTC)

Which Australian native frog?

Which Australian native frog in the East coast region of NSW makes a sound like a piece of wood going clunk or "clock" against something? It's small and brown and turns up in metropolitan Sydney. Julia Rossi (talk) 10:32, 9 March 2008 (UTC)

Could it be the pobblebonk? Adambrowne666 (talk) 12:20, 9 March 2008 (UTC)

Thanks Adambrowne, pobblebonk gives the eastern banjo frog so I'm assuming when they say it sounds "like a plucked banjo string" means in an non-tuneful, "pock" way for percussive effect. Any banjo players confirm that? Julia Rossi (talk) 21:28, 9 March 2008 (UTC)

Quantum Mechanics: Operator and Eigenvalue

For a given wave function $\psi (x)$ of a particle at position $x$, the momentum $p$ of the particle is the eigenvalue of (1)

${\hat {P}}\psi (x)=p\psi (x)$ (1)

where

${\hat {P}}=-i\hbar {\frac {\partial }{\partial x}}$ (2)

For example, if the wave function of a particle is

$\psi (x)=\exp \left(i{\frac {p_{0}}{\hbar }}x\right)=e^{i(p_{0}/\hbar )x}$ (3)

, the corresponding momentum $p$ will be

$-i\hbar {\frac {\partial }{\partial x}}e^{i(p_{0}/\hbar )x}=pe^{i(p_{0}/\hbar )x}$ (4)

$-i\hbar \cdot e^{i(p_{0}/\hbar )x}\cdot \left(i{\frac {p_{0}}{\hbar }}\right)=pe^{i(p_{0}/\hbar )x}$ (5)

$p_{0}e^{i(p_{0}/\hbar )x}=pe^{i(p_{0}/\hbar )x}$ (6)

$p=p_{0}$ (7)

Therefore, the momentum of the particle (3) is $p_{0}$. But does it make sense to say the coordinate $x$ of the particle (3) is the eigenvalue of (8)? It seems that we will always get $x={\hat {X}}$ if we replace (3), or any other wave function, into (8)!

${\hat {X}}\psi (x)=x\psi (x)$ (8)

Justin545 (talk) 11:05, 9 March 2008 (UTC)

I think the problem you are running into here is Heisenbergs uncertainty principle which states that there is an unavoidable minimum uncertainty in the product of the momentum and position observables;

$\Delta x\Delta p\geq {\frac {\hbar }{2}}$

If you claim to know with certainty that the momentum of the particle is $p_{0}$ then the position must, of necessity, be completely indeterminate. There is a similar relationship between other pairs of observables, such as Energy and Time. SpinningSpark 13:17, 9 March 2008 (UTC)

Uncertainty principle aside, most wavefunctions are not eigenvectors of most Hermitian operators. In fact no proper (normalizable) wavefunction satisfies ${\hat {P}}\psi (x)=p\psi (x)$ for any p. An equation like ${\hat {A}}\psi =a\psi$ is not meant to be solved for a as a function of ψ, it's meant to be solved for ψ as a function of a. Most wave functions won't be in the solution set, but they'll be expressible as a sum of elements of the solution set. If you like you can think of Hermitian operators like ${\hat {P}}$ as an odd way of specifying an orthogonal basis with a real number attached to each basis vector. -- BenRG (talk) 15:50, 9 March 2008 (UTC)

It turns out what I did was just replace the solution, or the basis, (3) into (1) according to the reply. I also forgot the position of a particle is uncertain, it is good to recall Heisenberg's uncertainty principle. I just did some ridiculous generalization and thought that the operator ${\hat {X}}$ can be used as (8) which is similar to (1) :p But it seems the operator ${\hat {X}}$ is useless except it is only used to calculate the mean value $\langle {\hat {X}}\rangle =\int _{-\infty }^{\infty }\psi ^{*}(x)\left[{\hat {X}}\psi (x)\right]dx$ - Justin545 (talk) 03:37, 10 March 2008 (UTC)

how do astronauts refer to spacesuits

The wiki space suit article is great, but I wonder if astronauts call them 'space suits' also, or use an abbreviation or colloqialism to refer to them. Can anyone enlighten me? Thanks Adambrowne666 (talk) 12:17, 9 March 2008 (UTC)

Normally, they'd just be space suits, although there are a number of different types, so astronauts probably just call them by their name - the Advance Crew Escape System Pressure Suit (commonly called the ACES) and the Extravehicular Mobility Unit (the EMU) are the two used on most American missions, for example. Russian space suits (Скафандр) are all named after types of bird: the Yastreb translates to "Hawk" for example. Laïka 16:12, 9 March 2008 (UTC)

Thanks, Laika - I like your space-themed name, btw. Adambrowne666 (talk) 22:48, 9 March 2008 (UTC)

Chemistry

Give an octahedral complex containing an optically active ligand? —Preceding unsigned comment added by Minmoy mld (talk • contribs)

Sounding like homework: so the complex may or may not be optically active, but the ligand is? Many of the biomolecules that incorperate a metal may be like this. cyanocobalamin is one example. Graeme Bartlett (talk) 13:18, 9 March 2008 (UTC)

A gamma ray burst extinction scenario

(Bolded questions) I have been reading up on the GRB articles for fun. Not so fun are the theories about some random GRB making us all extinct, in effect at least. My question is not about what is a good idea or not to help prevent the earth from taking damage, but if it is possible to build a kind of screen that could absorb the rays on earth's behalf, shielding earth, and most importantly what material would suffice? The disc, made of whatever we would harvest from other planets, would have a diameter a bit greater than that of earth. It's placed at a good distance from earth (in the hundreds of thousands, or millions of kilometers), and to make matters worse, would need to somehow follow earth's orbit around the sun. Assume of course, that we know exactly where the GRB is likely to come from (which isn't entirely unrealistic). Are there, for the sake of adding meat to this question, any serious discussions within scientific groups how to best protect earth against a GRB? 81.93.102.185 (talk) 13:17, 9 March 2008 (UTC)

The "screen" would probably need to be several metres thick to provide any useful protection. But let's suppose, for simplicity, we make a disk the same radius as the Earth but just 1 metre thick. This would require the same amount of matter as a sphere about 60 km in diameter - something about the same size as a small moon of Jupiter. Now remember that the hypothetical asteroid that may have wiped out the dinosaurs is estimated to have been only about 10 km in diameter. I think the risks caused by having such a massive object anywhere near the Earth's orbit would be much greater than the GRB risk that it was protecting us from. Gandalf61 (talk) 15:09, 9 March 2008 (UTC)

Hi. Well, it might be possible if you could somehow put the object in free-fall around the Earth. Now, an object that big would weigh roughly 5x10¹⁴ tons if I calculated correctly, so it would be pretty hard for it to get off the Earth in the first place, unless you assemble it in space, which would take decades and trillions of dollars for something that probably won't happen anytime soon anyway. Global warming is a much more immeinent risk. Also, if it were free-falling around the Earth, then you would have to know all the GRBs years in advance so that the disk could be positioned correctly. In reality, we probably wouldn't know about a GRB until the instant it hits us, because in order to detect it, we would need access to the radiation, unless you set up probes around the solar system, which might give us just a few hours' warning (or not, because for the time the signals from the probes would have gotten to us, the probe would have been destroyed and the GRB would ahve already hit us). This again would take decades and trillions of dollars. It's also pretty hard to tell when a particular part of the sky or star is about to go GRB, as when we see the star exploding, if it is releasing a GRB, it would have already hit us by the time we detect the light from the supernova. Also, if that disk hits Earth, its impact would be spread across the Earth, but can you imagine a metre-thick material crashing towards Earth at 15 km per second (9 miles per second) on every part of the half of the Earth? Sure, parts of it might burn up, but large fragments would still land all over the Earth, and there's another trillion dollars wasted. Besides, if an asteroid hits that disk? It's going to break if it's only a few meters' thick. Also, an average single gamma ray will be blocked by 10 km roughly of air, but with relativity and zillions of rays, anything can happen. It usually isn't a problem unless the ray is directly pointed at us or if a large supernova explodes very nearby. Hope this helps. Thanks. ~AH1^(TCU) 15:44, 9 March 2008 (UTC)

To get to the end part of the question, no, there are no serious discussions in the scientific community to protect Earth from a GRB. As noted by the responses above, it's impossible short of some sort of Dyson sphere. However, there is one agreed-upon method to protect humanity from a GRB -- extrasolar colonization. — Lomn 17:45, 9 March 2008 (UTC)

Wouldn't a more realistic way to protect humanity be for us to live underground ? This would also have the advantage of providing protection from the far more likely scenario of a nuclear war. Environmentalists would be happy as underground living means less energy used for heating and A/C and the surface could be reclaimed and used exclusively for farms and nature. StuRat (talk) 17:56, 9 March 2008 (UTC)

Unless you can move the entire ecology (or at least a fully self-sustaining portion thereof) underground, the GRB is still going to fry life on the surface. — Lomn 22:07, 9 March 2008 (UTC)

Nuclear reactors could provide power almost indefinitely. Greenhouses could maintain plant life. Animals could be bred and slaughtered... -- 81.98.253.215 (talk) 22:35, 9 March 2008 (UTC)

Aren't you concerened about a mine shaft gap, though?

Atlant (talk) 16:36, 10 March 2008 (UTC)

Hi. How would extrasolar colonization help protect against GRBs? They are probably just as likely to hit that extrasolar planet as on Earth. Also if we were to create a dyson sphere then we would have become so technologicly advanced that we would have destroyed our own ecosystem and then we would have to colonise other planets. Thanks. ~AH1^(TCU) 23:45, 9 March 2008 (UTC)

It's simply a matter of not having all one's eggs in one basket. You're entirely correct that any planet is vulnerable. — Lomn 18:24, 10 March 2008 (UTC)

How long does a GRB last? If less than a few hours, I'd submit that about half the Earth will be naturally shielded by miles of earth/Earth.

Atlant (talk) 16:37, 10 March 2008 (UTC)

As I understand it, it's not the immediate deaths from irradiation that make it an extinction threat, but the atmospheric changes it would cause. But there's not likely to be one close enough to us to matter anyway; as I recall it would have to be within about 500 light-years, and there just aren't any candidates within that sphere. There's more risk, I'd say, that we'll destroy our ozone layer ourselves. Minor planets, on the other hand, remain a genuine threat. --Trovatore (talk) 19:00, 10 March 2008 (UTC)

A gamma ray burst lasts seconds, not hours, and from the sources I have seen, a direct hit from a burst 8,000 light years away could cause changes in the atmosphere, but this is obviously theoretical. Jehochman ^Talk 19:19, 10 March 2008 (UTC)

Another birdsong?

Hi. This morning at around 8am (because of DST), I heard another birdsong. This time it was about -12C outside at sunrise, after a major snowstorm that dumped 25cm of snow and created 3 ft drifts. Anyway, it sounded like it was coming from a tree. First there were either one or two or three whistle-like notes, then six or seven flatter notes that sounded like a mix between a chirping bird's chirp, a pigeon's coot, and an owl's hoot. So for example: Whree? Whree? woo-woo-woo-woo-woo-woo-woo. The entire call lasted just over three seconds. It is sometimes repeated once every ten seconds maybe. I don't think it's an owl, and aren't owls nocturnal anyway? Any idea what it might be? I live in southern Ontario. Thanks. ~AH1^(TCU) 14:27, 9 March 2008 (UTC)

Your description doesn't match exactly, but listen to the call of the mourning dove here and let us know if that's it. Most owls are nocturnal, but not all. --Milkbreath (talk) 14:47, 9 March 2008 (UTC)

Hi. No, that probably isn't it. The one I heard had more ooos and sounded less mournful. The first note I heard did not rise up so suddenly. The ooos I heard did not lower in pitch as they were sung, they stayed constant. Also, the one I heard was a bit higher in pitch, and there was often more than one starting note. By the way, I think I have heard that mourning dove song somewhere, and now I know why they call it the mourning dove. Thanks. ~AH1^(TCU) 15:27, 9 March 2008 (UTC)

I don't think I know from personal knowledge what bird you've got there, but I'm trying to find it. The call of the saw-whet owl comes close. The northern pygmy-owl is diurnal and has a call like yours, except in the reverse order. A nocturnal bird will call in the daytime sometimes. --Milkbreath (talk) 16:19, 9 March 2008 (UTC)

Tortoise speeds

The common stereotype is that tortoises are slow animals. Form what I have observed from my german tortoise, this does not seem the case. For their size, ad the weight of their shell, the seem to have a relatively good speed. Does anyone have some outside input on this? —Preceding unsigned comment added by Gbgg89 (talk • contribs) 16:55, 9 March 2008 (UTC)

I would call tortoises slow, yes. Saying "for their size and weight of their shell they are fast" misses the point, in my opinion. That's like saying "may car is fast considering it's minuscule engine, poor gear ratios, and high mass". However, we can find other larger and armored animals which are much faster, like a rhino. I'd say the short legs are what slows tortoises down. Are tortoises fast enough to outrun any predators ? No, they must rely on their shell to protect them. Perhaps we should turn this around and conclude that they are slow because, due to their armor, they don't need to be fast to escape predators. StuRat (talk) 17:48, 9 March 2008 (UTC)

Ignoring WP:NOR, I would say the pet tortoise I have is not only slow because it cannot move quickly; it's also slow because it doesn't move much. It has an inactive life style and, except for eating, only very occasionally transports itself. --Bowlhover 04:52, 10 March 2008 (UTC)

How do astronauts swallow ?

Gravity seems to be an important factor in swallowing on Earth. I know I can't swallow when upside down and find it difficult when lying down. This is particularly true of difficult to swallow items like dry crackers. Related to this is the question of gastric reflux. This often happens to people while lying down, since they lose the gravity assist in keeping stomach acid in the stomach. Wouldn't this be even worse for astronauts, who always lack that assist while in orbit ? StuRat (talk) 18:08, 9 March 2008 (UTC)

Well, swallowing is largely due to peristalsis, which should be unaffected by orientation. In fact, in zero G, it ought to be easier to swallow than lying down or upside down in normal G, since you're not working against gravity, though harder than upright. -mattbuck (Talk) 18:25, 9 March 2008 (UTC)

That would explain how an astronaut's body would handle excretions too. Julia Rossi (talk) 21:35, 9 March 2008 (UTC)

Is it possible for someone of mixed race to be born transparent as a result? Why not?

Assuming the colors of his or her parents blend perfeclty, would it be possible to pick two such people that their son or daughter would (under the condition just specified) be born transparent as a result? Why or why not? I've tried to read our color article but it's a bit hard to take in all at once... —Preceding unsigned comment added by 79.122.37.156 (talk) 18:27, 9 March 2008 (UTC)

Not due to blood in the skin it would seem. Though this is based on a very rudimentary understanding of matters. Our article skin tone ny156uk (talk) 18:39, 9 March 2008 (UTC)

No. Skin cells are not transparent and in fact between people of different races they are almost identical with the main cause for difference in skin colour between these races being the saturation of melanin in ones skin, something dark skinned people have more of than white skinned people. Blood and other factors will always add colour to skin which is independent of race.PiTalk - Contribs 19:47, 9 March 2008 (UTC)

1. Colors of parents don't blend perfectly

2. Lighter skin is just an absence of melanin. There isn't a "transparent" option in skin, just a question of how much melanin. Total absence of melanin (see albinism) isn't transparent, it's just very very light.

3. You seem to be confusing additive color and subtractive color. Light is additive—it adds up to white; physical inks and dyes and melanin is substractive—it adds up to black. You can't mix white in a subtractive color system; white is the absence of color. --98.217.18.109 (talk) 19:46, 9 March 2008 (UTC)

When you look at a person's skin, the color you see is that person's phenotype. It's primarily determined genetically, but it's determined by a large number of genes (certainly more than six) which interact in complex ways. You can't determine exactly which genes (or alleles) a person has by looking at their skin. A child's skin color is determined by which alleles he inherits, and not by the skin color of his parents. It's not a matter of "blending" phenotypes, but of which alleles he inherits (at random) from his parents. There's no guarantee that the child's genes are those which have manifested in his parents. And there's no combination of genes that results in "transparency" in humans. - Nunh-huh 01:27, 10 March 2008 (UTC)

Of course some people claim to be transparent. With regard to skin, some animals are transparent, though I don't think we have an article about this.--Shantavira|^{feed me} 10:39, 10 March 2008 (UTC)

Tansparent animals are usually those that live in water. For things that live in air there is a big refractive index change from air to the flesh of the animal. Not only that but the skin on the surface is not completely smooth, and has air surrounding the dead cells. This results in light being scattered, and gives a white appearance. So if there is no colour in the skin, it will appear white. Light penetrating further in can be scattered by small organells etc, so that can give a bluish appearance. A human is so thick and full of light scattering, and coloured objects there is no way they will be transparent. Even the transparent animals are very small. Graeme Bartlett (talk) 22:36, 10 March 2008 (UTC)

Thermosynthesis & Radiosynthesis --

Definitions -

By these terms, I refer to processes similar to photosynthesis, but harnessing thermal or other radiative energy in the place of visible light.

Comment -

The natural origin of sucrose is living-plant photosynthesis, energized by visible light -- whereby (typically) sunlight, water and carbon dioxide (from the air) are reacted. I suspect that sucrose is an overall very efficient energy storage medium which is easily transported.

Question -

Does anyone know of any other radiant-energy process other than visible-light photosynthesis which can produce sucrose or some other simple, easy-to-handle hydrocarbon ? I suspect that such processes could possibly provide energy storage, transport and recovery mechanisms far superior to those based on hydrogen technology. 208.63.237.3 (talk) 18:45, 9 March 2008 (UTC) allenwoll

There are organisms that use chemosynthesis, but it is similar to photosynthesis as far as glucose creation is concerned. For storage, plants make polysaccharides, such as starch and pectin. Animals make glycogen and fat (a hydrocarbon). I'm not sure about your claim to a far superior mechanism, because burning oil is about as efficient as you can get using biological materials (as far as I know). The only problem is that this releases a lot of CO₂. Hydrogen fuel is an entirely different and efficient (albeit, slightly dangerous) way of storing energy. Generally speaking, if you're looking for high efficiency for storing and using energy, do not look at biological systems. They're good, but we already know of better. (EhJJ)^TALK 23:42, 9 March 2008 (UTC)

+++++++++++++++++++++++++++++++++++++++++++++

Regarding CO2 -- That is not an issue, since the manufacture of the sucrose used CO2 from the ait in the first place : no net change.

Regarding Storage & Transport -- A bag of sucrose looks pretty transportable and storable to me !! Starch is OK, too, but what would be the advantage ??

Regarding Biological SYSTEMS -- I wasn't considering LIVING systems, rather processes like what has become generally known as artificial photosynthesis.

Regarding Hydrogen -- The hydrogen storage/transport cycle is VERY inefficient at this time, as well as dangerous. So was that for acetylene at one time, but no more. But we are not there yet for hydrogen and may never get there, TBD.

"Know of better " -- What, then ??

+++++++++++++++++++++++++++++++++++++

. —Preceding unsigned comment added by 208.63.237.3 (talk) 00:03, 10 March 2008 (UTC)

Sucrose is not a hydrocarbon, but a carbohydrate (and the former would yield more energy per mass and per volume if burnt with oxygen, thus they are more efficient from a storage point of view; biological organisms also use fat, which are more efficient than carbohydrates but less efficient than hydrocarbons in this respect). As for other carbohydrate-producing processes, some fungi are suspected to use gamma radiation. Icek (talk) 03:51, 10 March 2008 (UTC)

++++++++++++++++++++++++++++++++++++++++

Thanks, Icek.

Let me rephrase -- I seek information on the potential existence of a process using thermal or other radiation to produce "optimum" chemical compounds from readily available, cheap and nominally non-toxic materials -- water, air (including carbon dioxide), etc -- "optimum" for energy storage and transport as well as for energy recovery. Such a process may or may not entail living organisms, but perhaps better not.

Whether the compound is a hydrocarbon, a carbohydrate or a fat -- or some other sort of compound altogether -- is, I think, irrelevant, except as to its potential performance toward the stated goal.

++++++++++++++++++++++++++++++++++++++++ . —Preceding unsigned comment added by 208.63.237.3 (talk) 05:09, 10 March 2008 (UTC)

Unfortunately, our article on thermosynthesis is just a single line. That said, there are some interesting hits if you Google search "thermosynthesis" [14], or take a look at PubMed. Unfortunately, I can't help you find industrial processes used for converting thermal energy directly in to chemical energy, as I only know of methods that involve an electrical energy intermediary step. Good luck! (EhJJ)^TALK 13:39, 10 March 2008 (UTC)

Query: Name of inedible string/fiber found in bananas?

I am a writer looking for the name of the inedible string/fiber that runs along the length of a banana (often left after the peel is removed).

I have been unable to find it anywhere.

Thanks in advance

Writerdog8 (talk) 20:34, 9 March 2008 (UTC)

I don't think any part of a banana is inedible? --BozMo talk 20:39, 9 March 2008 (UTC)

It seems to be part of the "pith" or inner rind inside the skin that takes a second stripping if you don't like it on the fruit. Julia Rossi (talk) 21:25, 9 March 2008 (UTC)

Its going to be equivalent to a leaf vein, or Vascular tissue, ie xylem and phloem. Graeme Bartlett (talk) 22:40, 10 March 2008 (UTC)

What plant are these people selling?

http://pics.livejournal.com/n0mad0/pic/0000gk7z --Sonjaaa (talk) 20:45, 9 March 2008 (UTC)

Russian "kale", perhaps? As here [15]. Julia Rossi (talk) 21:18, 9 March 2008 (UTC)

Lithium sunsets?

A co-workers claims to know why sunsets are pleasing to the eye. He claims that sunlight, when traveling through the large amounts of atmosphere (due to the sun's low angle relative to the horizon) somehow contains micro amounts of lithium that enter the eyes and makes the sunset watcher feel good. That sounds absolutely preposterous. Wouldn't landscapes then be encrusted with elemental lithium from the countless centuries of sunsets? Wouldn't particles of lithium be blocked by contact lenses, glasses, and sunglasses -- so only bare eyes could enjoy sunsets? --70.167.58.6 (talk) 22:26, 9 March 2008 (UTC)

You don't need to come with reasons why his idea is stupid. He needs to come up with ideas of why his idea isn't. Theresa Knott | The otter sank 22:28, 9 March 2008 (UTC)

Wiki doesn't have an article on everything, contrary to WP:WHAAOE: there's no article for chain yanking!

Atlant (talk) 16:40, 10 March 2008 (UTC)

How can sunlight contain lithium? Sunlight are photons and lithium are atoms. 122.107.151.153 (talk) 23:35, 9 March 2008 (UTC)

There is water on the exterior of the eyes, and when lithium comes into contact with it, it forms lithium hydroxide, hydrogen, and energy in the form of heat (an exothermic reaction). I don't know how lithium in the eyes would feel, and nor do I want to. Lithium hydroxide is highly caustic and the temperatures are hot enough to burn.

There won't be buildup of lithium on the ground, though, because any contact with water will cause it to immediately become lithium hydroxide and hydrogen. The hydrogen would escape to the very outer limits of the atmosphere, but does anyone know what will happen to the LiOH?

As for reasons why your friend's theory is ridiculous:

(1) Lithium cannot pass through the atmosphere without reacting with the oxygen and forming lithium oxide.

(2) How can the lithium pass through the atmosphere almost horizontally without falling due to gravity or stopping due to air resistance? What is propelling them?

(3) Why is it that the lithium only exists when the Sun is low on the horizon, and not when it's high in the sky? Ask your friend to explain this.

(4) Sunsets do not look any different through optical aid (your reason).

(5) Your friend was probably ascertaining your guillibility. --Bowlhover 01:04, 10 March 2008 (UTC)

According to him, the sunlight doesn't contain lithium, but carries/propels the lithium that's formed by some reaction between sunlight and low angle atmosphere. I guess these particles are being wisked into my eye carried on beams of sunlight. SO... just why are sunsets pleasant to look at? --70.167.58.6 (talk) 03:41, 10 March 2008 (UTC)

I'm guessing because they're beautiful. 206.252.74.48 (talk) 12:51, 10 March 2008 (UTC)

This week's meteor

Hi. I saw on the news that an astronomer reported that a meteor this week may have landed in Georgian Bay near Parry Sound, Ontario. Do we have either an article, a mention in an existing article, or a Wikinews article on this? Should this be mentioned somewhere perhaps in the meteorite article? Thanks. ~AH1^(TCU) 23:36, 9 March 2008 (UTC)

Well, I suppose it might warrant a mention, but meteorite impacts aren't really that rare, it's just we don't tend to notice them. -mattbuck (Talk) 01:06, 10 March 2008 (UTC)

I don't think this meteor is notable enough to be mentioned in meteorite. There is nothing extremely unique about this specific rock; it hasn't even been recovered yet. Many much more significant meteorites exist, such as ALH84001, suspected of containing Martian life, and the Kaidun meteorite, which could have come from Mars' moon Phobos. --Bowlhover 05:28, 10 March 2008 (UTC)

Hawking radiation emission rate inversely proportional to black hole mass - why?

The rate of Hawking radiation emission increases as the mass of the black hole decreases([[16]], second paragraph), what I don't understand is that if the emission method ([[17]]) is related to zero-point energy particles appearing and one half of the pair being captured, why is it that when the surface area of the event horizon would be greater for a larger black hole the Hawking radiation doesn't increase? To my lay understanding the probability of the particle capture would increase. 86.5.95.29 (talk) 23:51, 9 March 2008 (UTC)

Well, regardless of black hole size the ambient temperature goes to infinity as you approach the event horizon. The usual Hawking temperature is the limit at large distances. So I guess you could say that a larger hole emits less radiation because more of it gets pulled back in, although I don't know if that's a correct picture. -- BenRG (talk) 00:35, 10 March 2008 (UTC)

March 10

Circular Motion

Imagine that you swing about your head a ball attached to the end of a string. The ball moves at a constant velocity in a horizontal circle. Can the string be exactly horizontal? Why? - Thanks —Preceding unsigned 00:23, 10 March 2008 (UTC)

Is this homework? Try setting up the problem with a horizontal string and working out all the forces involved. (There aren't too many—gravity, tension, centripetal/centrifugal.) -- BenRG (talk) 00:38, 10 March 2008 (UTC)

The answer is "no", and the presence of a downward gravitational force vector should make the reason why obvious. =Axlq 01:55, 10 March 2008 (UTC)

Sure it can. The swinger just has to provide enough force to counteract gravity. Oops. Clarityfiend (talk) 02:25, 10 March 2008 (UTC)

No it can't as would be obvious if you draw and diagram and add the forces involved. Theresa Knott | The otter sank 05:21, 10 March 2008 (UTC)

Nitpick alert: the ball can't be moving at constant velocity either, though it may be moving at constant speed. Constant velocity requires travel in a straight line. AlmostReadytoFly (talk) 09:09, 10 March 2008 (UTC)

Energy Drink Death

First off, I know that drinking enough of anything can kill you.

My question is though, our article on Cocaine (drink) states that it contains 350% as much caffiene as redbull. That seems like a lot to me. How much caffeine can the human body tolerate? (I am very disinterested in killing myself, this is just curiosity) —Preceding unsigned comment added by 24.128.192.184 (talk) 00:35, 10 March 2008 (UTC)

Caffeine. Quote: "The LD50 of caffeine in humans is dependent on weight and individual sensitivity and estimated to be about 150 to 200 milligrams per kilogram of body mass, roughly 80 to 100 cups of coffee for an average adult taken within a limited timeframe that is dependent on half-life" Wisdom89 _{(T / ^C)} 00:51, 10 March 2008 (UTC)

Wouldn't the LD_Lo or LD_min be more appropriate than the LD₅₀ in this case? —Keenan Pepper 20:15, 10 March 2008 (UTC)

Hair loss (non-balding)

Hi. This is not a request for medical advice. I think I've heard somewhere that the average adolescent loses roughly 120 hairs a day. Is this true? We really should have an article on hair loss that does not redirect to balness, then. Is that why when I drop food on the carpet it gets covered with hair even if it has been vacuumed? When does hair loss of more than one hair a day usually begin at, then? On average, when is the first white, gray, or silver hair occur in an average person (head)? Do people lose skin hairs too (not caused by accidental pulling)? This is not homework. On average, approximately how many hairs would have been lost (on a person that is not born will to be bald) and how many white/gray/silver hairs would have developed by the time an average person turns 18, for example? Do common mammalian pets (eg. cats, dogs, rabbits, hamsters, gerbils, mice, rats, etc) lose hair as rapidly as humans or more rapidly? What colour of hair loses hair most rapidly and which least rapidly? What about de-melanined hairs? Thanks. ~AH1^(TCU) 00:49, 10 March 2008 (UTC)

These links should help you with your questions: [18],[19], [20]. Wisdom89 _{(T / ^C)} 00:54, 10 March 2008 (UTC)

Anyone who has ever owned a cat will tell you how rapidly and in vast quantities they lose hair. As for the carpet, it's probably a mixture of hair which wasn't picked up by the vacuum, carpet fibres and other random dust and detritus. -mattbuck (Talk) 01:02, 10 March 2008 (UTC)

What is naphtha?

Is it really the same thing as petroleum ether? If so, why aren't the articles merged? If not, what is the difference? What is the main meaning of naphtha when the term is used in modern English? --Sonjaaa (talk) 00:55, 10 March 2008 (UTC)

Petroleum ether is obtained from petroleum refineries as the portion of the distillate which is intermediate between the lighter naphtha and the heavier kerosene says the PE article, while Naphtha says it is referred to as PE. My guess is that naphtha is not the same, but that there is a blurred boundary. -mattbuck (Talk) 01:00, 10 March 2008 (UTC)

All the terms used by the petro-chemical industry for the various fractions produced by oil refineries are ill-defined chemically and always include a large range of alkanes which overlap quite considerably with neighbouring fractions. It is more of a relative order of fractions up the distillation column which defines the terms. SpinningSpark 08:02, 10 March 2008 (UTC)

Question

Why do scientists use animals' Latin names? 58.168.209.250 (talk) 01:17, 10 March 2008 (UTC)

Biological_nomenclature#Value_of_binomial_nomenclature --Sonjaaa (talk) 01:20, 10 March 2008 (UTC)

That doesn't answer why Latin in particular, or the historical reasons for it. The simple answer is that Latin used to be the lingua franca of science—the "neutral" language that scientists of all countries used when they wanted to communicate with one another (though by the 19th century it was French and German; today it is English). It was expected that all educated men (and it was primarily men who were allowed to participate in the republic of letters for a good long time) would know the language, whereas whether they would know English, French, Russian, Italian, Swedish, etc. was less likely. Thus a large number of the early major scientific publications were originally written in Latin as well—De revolutionibus orbium coelestium, Philosophiæ Naturalis Principia Mathematica, etc.

The practice of using Latin specifically for binomial nomenclature (those animal names you are thinking of: genus plus species, Homo + sapiens) goes back to Linneaus, the father of modern taxonomy, and has stuck every since. Standardizing nomenclature in a neutral, non-changing language was important to making sure that a creature in one part of the world was really the same (or similar) creature in another, even though they had radically different names in the local languages. --98.217.18.109 (talk) 01:45, 10 March 2008 (UTC)

I've always enjoyed the fact that "Linnaeus" is itself a Latinized Swedish name. I suppose as "Carolus Linnaeus" it would be fully binomial. - Nunh-huh 01:42, 10 March 2008 (UTC)

Well, again, it's the language Linnaeus himself published his major works in. He wrote the whole thing in Latin, name included. He practiced what he preached! The custom of using only the Latinized last name for "major" writers is quite old (think also Copernicus). Scientists already drop the Albert from Einstein quite often; imagine how that'll progress in two hundred years. --98.217.18.109 (talk) 01:45, 10 March 2008 (UTC)

Yes, it's not that he was unusual in adopting a Latin name (Paracelsus, Helvetius, etc.) but that it was in his case an amusing coincidence. - Nunh-huh 02:05, 10 March 2008 (UTC)

There is a second reason Latin was used - it is a "dead" language. It is not changing due to modern usage. So, the definition of a Latin word 100 years ago is the same definition today and will be the same definition 100 years from now. English (or any other modern language) doesn't have that luxury. Consider "urchin". What is that? Easy, a nasty street kid. Or, perhaps it is one of those prickly things in the ocean. Not long ago, it was a prickly little animal in British gardens. Before that, it was simply a vulgarity. Who knows what it will mean in another 100 years. It is a good thing we don't use it for scientific purposes since it isn't nice enough to pick one definition and stick with it. -- kainaw™ 17:04, 10 March 2008 (UTC)

Latin is mostly dead. But it is the official language of the Vatican, and that state's panel of Latin experts do formulate new words and constructions for things like "helicopter" and "hard disk" that the Romans knew not of. There are (or was) also available on CD the Elvis Presley classics, "Tenere me ama" ("Love Me Tender") and "Nunc hic aut humquaum" ("It's Now or Never"). - Nunh-huh 23:47, 10 March 2008 (UTC)

Biosphere ?

Many people claim that houseplants "cleanse the air", by removing particulates and carbon dioxide and adding oxygen. While this is certainly true to some degree, I'm of the opinion that the quantity of plants needed to do a significant amount of this would be far more than would fit in the home, based on plants having much slower metabolisms than people. So, I'd expect that if the biomass of people and pets in your home is 1000 lb, that you would need maybe 10,000 or 100,000 lb of plants to clean the air of the carbon dioxide and other waste products the people create. How can I calculate the actual ratio ? StuRat (talk) 01:24, 10 March 2008 (UTC)

Well, this would take some research - if you can come up with the amount of CO₂ used per day by plants, we could do a quick and dirty calculation. On the human side: average CO₂ content in inhaled air is roughly 383 ppm by volume, which is 0.0383%.

Average CO₂ content in exhaled air is 4.5% by volume. The difference (4.5% minus 0.0383%) would be 4.1%. So the CO₂ output from a human is 4.1% of the volume of inhaled (or exhaled) air.

The tidal volume (volume of a normal breath) of a human is about 500 mL. The usual respiratory rate varies between 12 to 20 breaths per minute. For our purposes, let's say 18 breaths per minute.

There are 1440 minutes in a day, or 25920 breaths per day. 25920 breaths of 500 mL each = 12960000 mL = 12960 liters per day. 4.1% of 12960 liters is 531 liters of CO₂ produced per human per day. There are 22.4 liters/mole of gas at STP, so 531 liters is 23.7 moles. There are 44 g/mole of CO₂, so 23.7 moles = 1043 grams of CO2, or roughly one kilogram, produced per human per day.

I think :) - Nunh-huh 02:02, 10 March 2008 (UTC)

Good work, now we need some info on the plant side. StuRat (talk) 03:15, 10 March 2008 (UTC)

You also need to account for the efficiency of the plant at converting CO2 to oxygen. I have read that plants are extremely efficient (95%[21]) at using light energy for this process. So even if plant metabolism is slower, it may be compensated by a more efficient CO2 to O2 conversion than a human's ability to produce CO2 from O2.

The amount of oxygen produced also depends on the light available. I had an aquarium containing hydrilla plants. When the sun shone on them, streams of oxygen bubbles would spew forth from the leaves. =Axlq 02:09, 10 March 2008 (UTC)

23.7 moles of carbon (C) is 284g, so the total carbon content of plant mass in your house must increase by 284g per day per human. If we assume that plants are reprented by the formula CH2O (sugars) it is 948g per person per day, but there are also phosphates and nitrogen that the plant takes in, so 1kg per day would be minimum...Which looks very unrealistic.--Shniken1 (talk) 02:31, 10 March 2008 (UTC)

Interesting approach. Aren't plants something like 95% water ? I wonder what percentage of their weight is carbon. If we figure 4% by weight, then one kilogram of carbon increase would mean 25 kilograms of plant mass increase. StuRat (talk) 03:15, 10 March 2008 (UTC)

Yeah water would make up significant amount of the mass of the plant so yeah the mass of the plant as a whole would have to increase a lot more than its carbon mass (depending on the plant), and as plants get bigger I would suppose that water would be harder to obtain (via transirpation) so it may be the limiting growth factor.--Shniken1 (talk) 03:52, 10 March 2008 (UTC)

I'd expect most of the water to be supplied by humans watering the plant, with the roots sucking it up from there. StuRat (talk) 23:55, 10 March 2008 (UTC)

Much of this depends on what you mean by cleanse the air. I would expect the impact on oxygen and carbon dioxide to be minimal unless you live in an air tight box. Transpiration is a likely reason for cleansing. Transpiration cools the air due to evaporation. It also adds moisture to the air. Both these could be beneficial inside a house. David D. (Talk) 18:55, 10 March 2008 (UTC)

---

Incidentally, the following link is in the "Biosphere 1, 2, 3, and J" section of our Biosphere article:

"Biosphere 3 (aka BIOS-3) - Experiment to be conducted starting Jan 2008 in the Gary C. Comer Geochemistry building at Columbia University's Lamont Campus in Palisades, New York."

However, when I follow the link, the article says:

"BIOS-3 was a closed ecosystem at the Institute of Biophysics in Krasnoyarsk, Siberia, in what was then the Soviet Union."

Which is correct ? StuRat (talk) 03:33, 10 March 2008 (UTC)

(after edit conflict) According to http://www.newton.dep.anl.gov/newton/askasci/1993/biology/bio027.htm, it takes around 353 plants to match the oxygen input rate that humans require. However, I have two concerns with the webpage:

(1) The webpage assumes that all oxygen breathed in that does not enter the inactive part of the lung (the "dead space") is absorbed. According to Breath#Composition_of_air, 15-18% of exhaled air is composed of oxygen by volume. For the 252 L/h of inhaled air that does not enter the dead space, and the corresponding 252 L/h that are exhaled, about 42 L is exhaled. Since 53 L/h of oxygen that does not enter the dead space is inhaled, this gives an hourly oxygen usage rate of 53-42=11 L/h. Assuming the plant calculations are correct, 76 plants would be needed.

(2) At the end of the webpage, the author states that "oxygen production decreases as carbon dioxide concentration increases". However, according to the photosynthesis article, the amount of CO2 plants take in is equal to the amount of O2 they output. Humans also necessarily expel as much CO2 as they breathe in oxygen, so if 76 plants provide enough oxygen to sustain a human, they also absorb enough carbon dioxide to keep the environment's CO2 level constant.

So 76 plants per person, and if we assume plants are 500 g on average, that's 38 kg/person. The plants would have to be properly maintained, of course, and cannot be allowed to grow; growth would mean a higher demand for CO2 than the humans can supply.

About BIOS-3: Most sources state that it was an experiment in the Soviet Union: [22][23][24]. Searching for "bios 3 'Gary C. Comer'" on Google yields only the Wikipedia biosphere article and mirrors of it. --Bowlhover 04:06, 10 March 2008 (UTC)

That seems like way too much oxygen production per plant kg. After all, a person weighs around 38 kg, and I have a hard time accepting that plants, with their far slower metabolisms, use CO2 at the same rate people use oxygen. Also, if the plant doesn't grow, where exactly does all the carbon go that it sucks out of the air ? StuRat (talk) 00:03, 11 March 2008 (UTC)

While it might matter for a biosphere, for your purposes as I understand them (the plant cleans up after the humans), it doesn't matter whether or not the plants grow. - Nunh-huh 00:44, 11 March 2008 (UTC)

How can you ever fall in a black hole?

Since time slows per the reference frame of an outside observer as an object approaches the event horizon, and 'freezes' at the horizon (thus the Russian term for black hole: 'frozen star'), how can a black hole ever increase in mass? This was once considered a flaw in the concept of black holes, but evidently was somehow resolved. However, I've never seen an account of how it was resolved. (And yes, I do understand that for an observer falling past the event horizon, supposedly nothing unusual would appear to happen - except that you'd think s/he'd witness the end of the universe.) — kwami (talk) 07:03, 10 March 2008 (UTC)

This question has been previously answered here [25] and probably many times before. However, I never felt satisfied with the answer given then, for the same reason given by Kwamikagami. If someone can elaborate, please do. SpinningSpark 08:15, 10 March 2008 (UTC)

I’m no physicist. But as the mass of the black hole increases, the event horizon will increase in radius and objects that previously were hovering on the edge will be enveloped. And objects don’t need to actually be at the center of the singularity to contribute to the black hole’s mass/gravitational effect. (This is just my speculation.) — Knowledge Seeker দ 08:33, 10 March 2008 (UTC)

But the BH can't increase in mass unless something crosses the event horizon in finite time in the external reference frame. — kwami (talk) 08:46, 10 March 2008 (UTC)

I’m not sure I agree with that statement. — Knowledge Seeker দ 08:51, 10 March 2008 (UTC)

How would it increase in mass, without mass being added to it? — kwami (talk) 08:54, 10 March 2008 (UTC)

Perhaps I should be more clear. I contend that a mass placed just outside the event horizon will increase the gravitational field/curvature of space (as it would anywhere) and that therefore a small volume of space which previously had almost, but not quite enough gravity to have an escape velocity greater than c (or equivalent formulation) now will; in effect, the combined event horizon around the two objects will be larger. (Again, speculation.) — Knowledge Seeker দ 08:57, 10 March 2008 (UTC)

A group of massive objects, act as if all their gravity were concentrated at thier center of mass. So from a distant observer's POV anything frozen at the edge of an event horizon would still contribute to the total mass of the black hole system. Does that resolve the problem? Theresa Knott | The otter sank 12:28, 10 March 2008 (UTC)

Does this mean that an unfortunate astronaut just outside the event horizon might be observed by a "local" observer (say, another astronaut also falling into the black hole) as not having quite reached the horizon, but that both might be "observed" by a distant observer to be within the event horizon (i.e. part of the black hole)? dbfirs 12:54, 10 March 2008 (UTC)

Hi. On a Discover magazine there's this guy named João Magueijo that has a theory called Varying Speed of Light (VSL). When he introduced this theory, one physicist said it really stood for "Very SiLly". However, according to this theory, time and the speed of light slow near a black hole and never allow anything to escape nor go in (after all, black holes are infinitely dense). Hope this helps. Thanks. ~AH1^(TCU) 14:22, 10 March 2008 (UTC)

As far as I know Magueijo's VSL theory is supposed to be an alternative to cosmic inflation, so it only matters in the very early universe and doesn't have any bearing on (present-era) black holes. -- BenRG (talk) 21:33, 10 March 2008 (UTC)

Objects can and do fall in. They only appear to stop at the event horizon. 64.236.121.129 (talk) 16:43, 10 March 2008 (UTC)

The objects may see themselves falling in. An outside observer sees the objects dim and disappear as they approach the Schwartzchild radius. An alternate theory Gravastar suggests that matter falling into a compact stellar object will appear to cool and form a Bose-Einstein condensate. One consequence of general relativity is that perception is affected by perspective. Jehochman ^Talk 16:51, 10 March 2008 (UTC)

64 and Jehochman, it’s not that Kwami’s really disputing whether they fall in or not (the phrasing of the heading, unfortunately, is misleading). His question is (as I understand it), essentially: If, from the reference frame of an outside observer, an object never passes the event horizon [due to time dilation], how/when will he observe an increase in the black hole’s mass? — Knowledge Seeker দ 18:11, 10 March 2008 (UTC)

If matter has fallen inside the event horizon, how can you get back any information about mass inside? If light can't get out, neither can any other sort of information. If an outside observer can never see anything cross the event horizon, then presumably from their point of view, nothing ever has. A sphere or shell of mass around a point will be indistinguishable to an outside observer from all that mass being located at the center point. There would be no observable difference on the force of gravity affecting an outside observer. There are a lot of contradictions if we assume the existence of black holes. This may mean that our black hole model is wrong. Jehochman ^Talk 18:16, 10 March 2008 (UTC)

I don't know that much about black hole dynamics, but I think Knowledge Seeker is correct. Certainly it's a mistake to think that infalling matter has to fall through the event horizon to add to the mass, because nothing that happens inside the event horizon can be relevant to physics outside. Whatever it means for "the black hole to gain mass", it has to involve only the physics outside the event horizon.

The event horizon is acausal; it will happily expand faster than light to engulf infalling matter. Here's a special relativistic analogy. I'll use 2+1 dimensional Minkowski space because it's easier to visualize than 3+1 dimensions and 1+1 isn't enough for this example. At time t = 0 pick some region of the xy plane and magically destroy everything there. There's then a region of spacetime (a collection of events) with t < 0 which is unobservable to anyone who survives past t = 0, because any signal that might have originated from those events was destroyed. For example, say you destroy everything in the circular region x² + y² < 1 light year². Then the unobservable region is a cone in Minkowski space whose apex is x = 0, y = 0, t = −1 year and whose base is the destroyed disc. If you destroy a square (|x| < 1 ly, |y| < 1 ly) then the unobservable region is a square pyramid. The boundary of the unobservable region is the event horizon. The event horizon is always a null surface because of how it was defined, but it may have "creases" which are not null. For example, in the square pyramid case you have corners which go from x = y = 0 at time t = −1 year to x = ±1 ly, y = ±1 ly at time t = 0; they're effectively moving at c√2.

Let S be the destroyed set. Then the observable region at time −t is $\bigcup _{x\in S^{c}}B_{ct}(x)$, where S^c is the complement of S and B_r(x) is the ball of radius r centered at x. Imagine S being eroded away from all sides at the speed of light as you go backward in time. Now say S is a sort of peanut shape, or an overlapping union of two circles. As you go back in time it will become a thinner peanut; then it will break into two teardrop shapes, with the pointy bits pointing toward one another; then the teardrops will shrink and become more circular until they disappear. Now run this forward in time: two expanding teardrops appear out of nowhere, extend toward each other faster than light, and merge. That's kind of what a black hole merger is like. The event horizon is not at all like a physical object obeying dynamical laws; it's a global property of the whole spacetime and it "knows about the future". In fact it's a theorem that the event horizons of two black holes that will eventually merge have the teardrop point on them from the beginning. That's for merging black holes, i.e. tossing one black hole into another, but I think tossing ordinary matter into a black hole works similarly. Whether any of this answers the original question I'm not entirely sure. This is a tricky subject. -- BenRG (talk) 21:33, 10 March 2008 (UTC)

I wonder if Knowledge Seeker might be on the right track: Once an object approaches a black hole close enough that their center of mass lies within the EH, does the EH then expand correspondingly? But this would happen while a small mass is still quite far from the EH, so it wouldn't be engulfed. (If you were to drop a sandwich into a Solar-mass black hole, it would hardly affect the EH at all, so we're left with my original question.)

It's not true that we can't know what's within the EH, only that no signal can be sent out. Fields extend beyond the EH, but any modulations of those fields would be red-shifted to a frequency of zero. However, with those fields we can still measure the total electronic charge, mass, and momentum (linear and angular). — kwami (talk) 22:23, 10 March 2008 (UTC)

Also, pace another comment, it isn't the case that the object just appears to slow down, due to some kind of optical illusion. It isn't light that slows down, but time itself. In the external reference frame, it really doesn't reach the EH. Thus the problem. — kwami (talk) 22:50, 10 March 2008 (UTC)

Intermolecular Forces

Can a molecule have hydrogen bonding, permanent dipole - permanent dipole and instantaneous dipole - induced dipole intermolecular forces acting upon it at any one time? 88.108.198.114 (talk) 17:38, 10 March 2008 (UTC) —Preceding unsigned comment added by 88.108.198.114 (talk) 17:37, 10 March 2008 (UTC)

Yes. something like liquid cholesterol would be a easy example to consider87.102.94.48 (talk) 17:45, 10 March 2008 (UTC)

True. Remember that molecules can be very very large (Protein), or even macroscopic (DNA), so different parts of one molecule can have completely different properties. --Bmk (talk) 17:59, 10 March 2008 (UTC)

Batteries in series vs. parallel arrangement

If one battery in a set is bad (low voltage), which arrangement is affected more? —Preceding unsigned comment added by 66.120.95.52 (talk) 19:22, 10 March 2008 (UTC)

Series. Voltages in series add, so a bad one will lower the voltage. In parallel, the remaining good batteries will try to supply whatever current it takes backwards through the bad battery to drop the supply voltage across it. If they can't supply enough current to do that, the voltage will fall, but if they can it won't, much. So a series arrangement is always immediately affected, and a parallel arrangement might not be affected very much at first. --Milkbreath (talk) 19:54, 10 March 2008 (UTC)

What bodily function is not possibel in space?

what bodily function is not possibel in space? —Preceding unsigned comment added by 89.243.182.3 (talk) 20:13, 10 March 2008 (UTC) - Please don't post in all caps, it comes off as yelling -- MacAddct  1984 ^{(talk &#149; contribs)}

pushing the Caps Lock key a second time? Thomprod (talk) 20:14, 10 March 2008 (UTC)

If you mean in a spaceship, all bodily functions are possible, but can get a bit messy. That's why they have special devices for going to the bathroom. -- MacAddct  1984 ^{(talk &#149; contribs)} 20:28, 10 March 2008 (UTC)

It hasn't been demonstrated that a child can grow in the womb in space. I'm not sure what people have thought about this though.Sancho 20:39, 10 March 2008 (UTC)

Larry Niven made a significant plot point out of this in his Known Space series. Pregnant women who lived in the Belt were required to live in a hollowed-out asteroid, called Confinement Asteroid, that was spun to provide centrifugal force in place of gravity. --Trovatore (talk) 20:53, 10 March 2008 (UTC)

Bodily functions remain intact, however, there can be serious muscular atrophy due to zero gravity unless the astronaut exercises regularly. Wisdom89 _{(T / ^C)}

One man's meat is another man's poison

Are there any spices with an unusually small difference between the standard amount used for flavoring and the minimum poisonous amount? Or with an unusually large difference between the LDLO and the LD50? --67.185.172.158 (talk) 21:11, 10 March 2008 (UTC)

I seem to rememeber that 2 nutmegs could be fatal...87.102.94.48 (talk) 22:21, 10 March 2008 (UTC)

I had to look these up: LD_Lo = Lowest published lethal dose and LD₅₀ = Median lethal dose. Mmmm, Eggnog with extra nutmeg! :-)) --hydnjo talk 01:51, 11 March 2008 (UTC)

Molecular Excitement

I know that molecular excitement (vibrations, oscillations - what is the correct term?) slows down as Temperature decreases - I'm thinking of a liquified gas in a tank - and increases as the Temperature rises, but what happens when the Pressure increases or decreases? What effect does Pressure have on Molecular Excitement?

P. Lamont —Preceding unsigned comment added by 72.39.249.249 (talk) 21:18, 10 March 2008 (UTC)

Temperature has the greatest effect on molecular rotation, pressure also influences this, through pressure broadening.--Shniken1 (talk) 22:54, 10 March 2008 (UTC)

Pressure can change the temperature, if you increase pressure, the substance is likely to contract, and work is done on it. This will add energy, and the temperature will increase. This head can be conducted out. Also if pressure increased so that the material is compressed to a white dwarf density, then the uncertanity principle will ensure a uncertain temperature and Degenerate matter exists. Graeme Bartlett (talk) 23:15, 10 March 2008 (UTC)

type 2 diabetes and hair loss

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

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

--Milkbreath (talk) 01:54, 11 March 2008 (UTC)

Seriously, you need to consult a doctor about this - we can't offer medical advice of any kind... Wisdom89 _{(T / ^C)} 01:47, 11 March 2008 (UTC)