Wikipedia:Reference desk/Archives/Science/2007 March 16

{{#hell-o ppl::: Secondary question: Could a seismic instrument of some sort detect an earth quake from a plane in flight? I imagine a precise radar altimeter or some sort of laser might possibly detect ground vibrations. There would be some severe signal/noise issues, as the airplane jostles through turbulent air. I can't imagine that acoustic waves would propagate to the height of the aircraft via the air, but would another technology work around that limitation? Nimur 00:51, 16 March 2007 (UTC)

I doubt it, because using a fast moving object as a frame of reference to measure something not as fast probably won't give you very good results. --Wirbelwindヴィルヴェルヴィント (talk) 03:11, 16 March 2007 (UTC)

Add to that the shakiness of a plane. Even an apparently smooth airplane ride would affect the seismometer a lot. − Twas Now ( talk • contribs • e-mail ) 04:19, 16 March 2007 (UTC)

Not that this is a particularly useful comment, but the vibrations on the plane might make the seismograph work better, check out dither. --Cody.Pope 07:03, 16 March 2007 (UTC)

The acceleration due to gravity can be measured by gravimeters in moving aircraft, but the accuracy is unlikely to be adequate to measure the tiny accelerations (compared to the whole earth's gravity field) caused by earthquakes. Also you would have to be directly over the earthquake precisely at the time the surface moved. Cheers Geologyguy 17:29, 16 March 2007 (UTC)

incandescent/florescent bulbs

Since incandescent bulbs emit 95% of the energy consumed as heat, wouldn't that make them more efficient in colder climates or winter. where it would spare the heating system extra work? Dan Oprisko (email removed) —The preceding unsigned comment was added by 70.174.95.114 (talk) 00:28, 16 March 2007 (UTC).

If the furnace were an electric heater, you are correct. If it were gas heat, which is somewhat more efficient, I think the increased heating due to the lightbulb would be less efficient than the gas it would replace. Nimur 00:48, 16 March 2007 (UTC)

PS I have removed your email address to minimize spam. Nimur 00:49, 16 March 2007 (UTC)

If you have a use for the heat, then sure, it's no longer "wasted", but you've done nothing to improve the efficiency of the conversion to light. Regardless of the type of light source, converting electricity to light is pretty inefficient so you'll always have some heat to heat a building with in the winter. Atropos235 00:52, 16 March 2007 (UTC)

I'm sure this has come up before so you mgith find better discussion if you search through the archives. Several points that were raised in addition to the ones mentioned are the fact that this heat is generated near the ceiling and so may not be particularly useful, the fact some of it is lost to the ceiling and probably others I can't remember Nil Einne 08:43, 16 March 2007 (UTC)

On a separate but related note, how does a device intended to generate heat have an efficiency of less than 1? I understand a gas furnace, where energy goes up the chimney, but electric heat should be very near 100% efficient, since all the energy consumed goes to heat? anonymous6494 18:08, 16 March 2007 (UTC)

An electric heater, when looked at by itself, is 100% efficient (well, give or take minor factors like radio emissions, but those are only a tiny fraction of a percent). The reduced efficiency comes when you consider the system as a whole: an electric generator is about 30% efficient at turning natural gas into electricity, and possibly as much as a third of that electricity is lost to heating the transmission wires. Electric heat only makes sense if the electricity comes from a non-combustion source, such as wind power, hydropower, or solar power. --Carnildo 20:03, 16 March 2007 (UTC)

If it isn't glowing, then what is it?

A recent question brought up the Magnet viewing film. This piece of film/paper undergoes a color change in the presence of a magnetic field. I created the article, and User:SteveBaker made the valid point that glowing requires energy. Does anybody know if the strip is actually emitting light, or if it is just undergoing a color change to a lighter shade of green? Is energy being absorbed from the magnet? Could that energy be converted to light? Nimur 00:54, 16 March 2007 (UTC)

From [1]

When a dc magnetic field is applied to the bonded film, the nickel particles congregate in alignment with the flux lines emanating from the dc magnetic source. This mass grouping together of nickel particles causes a darkened appearance to the film directly where the magnetic field is impinging on the film. As a result, an exact two-dimensional image or impression of the magnetic pole or pole pattern (if there are more than one) is produced. This image is easily erased once the film is removed from the magnetic source and the nickel particles are allowed to freely re-disperse within their gelatinous cells. A common bar magnet can be swiped across the film to ensure complete erasure of the previous image, or by reapplying the film to another magnetic source the new image produced will completely replace the old one.

Atropos235 01:08, 16 March 2007 (UTC)

There is already a stub Magnetic field viewing film. None of which really describes how the film works. I'm trying to find out who actually makes the stuff. --Zeizmic 16:31, 16 March 2007 (UTC)

The electricmotorsupplies.com article is apparently written by the manufacturer of the film, and says "magne-rite corp", so I try magnerite.com and find their website: http://www.magnerite.com/frm_tek.html I've been telling others how this film works, but I've *never* seen a written explanation of the optics. Personal knowledge: ferro-powder suspensions change brightness under b-fields because the field causes the powder grains to attract each other and align to form arrays of chains or filaments. Viewed from the side the filaments reflect light, and viewed from the end the filaments absorb light. When the magne-view film is placed upon a magnet, the poles appear dark, and the region between the poles appears bright. (Try viewing the bright regions through a polaroid filter?) --Wjbeaty 19:41, 16 March 2007 (UTC)

Fall in a barrel of water

Background: To my understanding injuries/death from a fall (of a human) of a considerable height result from the differences in deceleration of the different body parts on impact (i.e. legs break, because feet stopped and legs still have downwards speed).

Now what would happen if you would suspend (diving somewhere around the center of the water mass) yourself inside a large barrel of water and that barrel would be dropped?

Would it make a difference whether the top of the barrel was closed or not? —The preceding unsigned comment was added by Lukas.S (talk • contribs) 02:17, 16 March 2007 (UTC).

I thought it was because of the bouyancy of water. Even though water is fluid, the surface tension forever over the area of a human body takes considerable force to break, so I would think that because the barrel is the one penetrating the water, the human inside would suffer less damage. --Wirbelwindヴィルヴェルヴィント (talk) 03:09, 16 March 2007 (UTC)

hmm, curious question, you mean the barrel with water and human are dropped onto the round right? Not into water? If so then you have to remember that a breathing human is actually not as dense as water so being suspended in water and dropped, I don't know if that saves you from any impact, wouldn't you still feel exactly the same force since the water is de accelerating just as fast as you? There is a big difference if you jump into a body of (relatively) stationary water. Vespine 03:31, 16 March 2007 (UTC)

I'd guess that if you were kept submerged in an unbreakable tank of water, sealed to prevent it spilling out when weightless, and dropped you would not suffer any bone injuries like you would in an ordinary fall. However, beyond some threshold the compressible air spaces of your body would experience a shock too great and might turn into a bloody pulp. Very interesting question. atropos235 ✄ (blah blah, my past) 03:51, 16 March 2007 (UTC)

Thanks for the ideas. Wirbelwind, the idea was to drop the barrel onto land, not in water. The barrel is filled with water. So does anyone have an idea what height would be actually survivable? Escape barrels instead of parachutes? : )Lukas 04:00, 16 March 2007 (UTC)

To me, it seems that the question is whether or not the water resistance would reduce your deceleration enough after the barrel hit the ground for you to survive the impact. I dunno, but my physical intuition leans toward no. Clarityfiend 08:44, 16 March 2007 (UTC)

If something (you) is neutrally buoyant in the water, if it accelerates one direction or another, the object will not move. If subjected to extreme acceleration like in a centrifuge, denser objects will move down, while the air stays up, so neutral objects wouldn't go anywhere. Maybe you could try it...put a few ants or something in one centrifuge tube, then put a few ants in water in another... -- atropos235 ✄ (blah blah, my past) 16:01, 16 March 2007 (UTC)

The viscosity of the water will affect its dynamics, e.g. how much damping and deceleration it provides. It's almost like lots of springs are attached on all sides of the rigid body, and each one compresses and slows down the impact. More viscous fluid would equate to stiffer springs, while a less viscous fluid would require more space to compress (slow down the human). The proper tradeoff could be made to ensure the human doesn't get crushed. Nimur 18:03, 16 March 2007 (UTC)

Once upon a time a gasoline chain in USA (Shell I think) had a series of booklets on what to do to raise your risk of surviving various accidents, like you are in your car on the road & something happens and now you are in your car under water. I seem to recall that one of the risks was you are in an elevator, and suddenly it is going down very fast (something broke) ... in that case, the way to lower risk that at the bottom you will be converted into a lot of broken bones in jelly, is to climb up and get a hold of anything on the ceiling, so as to break your fall into several falls. If you not crushed by the collapsing elevator, you lose your grip on ceiling, then you land on mess below, bending your knees and rolling like a parachutist.

I think similar scenario here ... does the water around you cushion the fall? Do we have any details on folks who chose to ride over Niagra Falls in an unorthodox way? User:AlMac|^(talk) 20:18, 17 March 2007 (UTC)

Details? Survival rate is less than 100%...[2] Nimur 21:28, 17 March 2007 (UTC)

Real Population Density

This question is one I've researched a couple of times in my life and, for me, comes under the heading "Questions that seem important but I don't see a lot of attempts to answer it". Basically, the question is: what is the real population density of earth (or could be asked of a nation or area) given the amount of usable land and resources available? When I last tried to answer the question for the date 2050 AD, I assumed that the population would be 9 billion and the land area was 57,500,000 sq miles. This gave a crude density of 157/sq mi. However if only half the land is usable (not ice, rock, desert, etc.), then the density would double at 313/sq mi. So, different answers depending on assumptions about usable land area. If resources were taken into account, the answer would be more complex in that mere square miles of land would then become unit-areas of viability in some way of measuring that. So, anyone have any ideas on the topic, or know of interesting efforts to answer this? --Quark —The preceding unsigned comment was added by 71.58.57.171 (talk) 03:43, 16 March 2007 (UTC).

Very few parts of the world are totally inhospitable to humans, that is where they cannot be self-sustaining. The south pole is such a place, but if history has taught us anything it's that people are insanely good at adapting to virtually any environment. Native people live in Siberia where it's rarely above freezing. The Sherpa live miles above sea level in the Himalaya, where it isn't very kind either. Carrying capacity is the term that describes the theoretical limit, but this limit constantly changes, usually upward, due to innovations in technology, occasionally down, because of things like localized climate change (drought) -- atropos235 ✄ (blah blah, my past) 04:32, 16 March 2007 (UTC)

Okay, I hope for other thoughts on this, but will reply to this one. First, thanks for the Carrying Capacity link, it is relevant. However, the point made about man's ability to survive in harsh climates needs more thought: while people can survive in harsh climates with specialization and effort, the numbers of people that can do so is very limited. In most cases, resources come from outside and are thus not really good examples of man's adaptability. Examples of this are such cities as San Diego, Las Vegas, etc. Without money, food, and water brought in, they would shrivel away. The land will not support them. So we still have the need to associate resources, land, and population density. I suspect we (mankind) don't think well about this for psychological reasons. --Quark

I'm not sure that's a good way to look at things. After all, hardly anywhere on Earth is truly self-sufficient, we all import a few things we need from elsewhere. Japan, for example, is resource-poor in many respects, so should we write it off as "parasitic" or accept that they contribute in ways other than providing raw materials ? StuRat 21:22, 19 March 2007 (UTC)

Butter or Spread

I just learned that even though the spread I eat, country crock, says it has 0 trans fat, it could actually still have some because the FDA allows any product with less than 0.5 grams of trans fat to be declared trans fat free. I looked at the list of ingredients and sure enough it contains partially hydrogenated oils. I have been browsing the internet, and while I learned that trans fat is very bad so is saturated fat as well to a lesser degree.

So should I go with the spread that has between 0 and 0.5 grams of trans fat, 1.5g saturated, 2g monounsaturated and 3.5g polyunsaturated

or

butter, which is pure saturated fat? Which one is healthier? —The preceding unsigned comment was added by 74.134.146.52 (talk) 05:58, 16 March 2007 (UTC).

Another one where we seem to not know. I suggest [3] [Mαc Δαvιs] (How's my driving?) ❖ 06:46, 16 March 2007 (UTC)

How about some of these healthier versions: [4] ? Also, try using alternatives to butter and margarine, like olive oil. When I make mac & cheese, for example, I don't add milk and butter, but add spaghetti sauce or salsa, instead, along with some cooked broccoli, to make a much healthier, but still delicious, meal. StuRat 21:30, 19 March 2007 (UTC)

Singularity and the universe

Is the universe and the singulatity from which the universe came one in the same except for the singularity having no time or space and the universe having unlimited space and time? 71.100.9.74 06:36, 16 March 2007 (UTC)

No body knows anything that far back, or even can guess very well that far back. If we assume things your question does, the answer would still be "we don't know." [Mαc Δαvιs] (How's my driving?) ❖ 06:44, 16 March 2007 (UTC)

You might be interested in our articles on the Big Bang, as well as Timeline of the Big Bang--VectorPotential^Talk 16:18, 16 March 2007 (UTC)

Please note that the universe may not be "unlimited" in either space, time, or both, as well. Undoubtedly it's very large, and will last a long time, but the jury's still out on infinity. See Shape of the Universe. Spiral Wave 13:26, 17 March 2007 (UTC)

Oops! Half a reply. And Fate of the Universe too, I meant to say. Spiral Wave 15:46, 18 March 2007 (UTC)

Medical lifting and transfer devices

Hi I have been searching the internet for some information on 4 different lifting devices, I have not had any luck finding simple information in relation to these devices for my Uni asignment. The four de4vices are: Pivot board Transfer Board Transfer belt Mechanical hoist

I am required to explain the device and what it is used for If you can help it would be much appreciated. Thankyou Richelle Kent —The preceding unsigned comment was added by 58.170.80.92 (talk) 08:22, 16 March 2007 (UTC).

Have you tried looking into some sort of medical text? Nil Einne 08:48, 16 March 2007 (UTC)

You would need a specialized nursing text or article. All of the devices are to assist the transfer of immobile adult patients in and out of bed. The names should suggest the distinctive differences to you. alteripse 19:39, 17 March 2007 (UTC)

Physics graphs

In physics, what does the area under a gravity/height (above surface) graph equal to? Many thanks.<span —The preceding unsigned comment was added by Cuban Cigar (talk • contribs) 09:39, 16 March 2007 (UTC).

Perhaps others can help, but I'm not particularly sure what a gravity/height graph is. What are the units of the 'gravity' component? Acceleration? Force? Velocity? Nil Einne 10:26, 16 March 2007 (UTC)

No need i got the question answered-it seemed you multiply the gravity component by mass to make it force (f=mg). ThCuban Cigar 10:34, 16 March 2007 (UTC)anks.

We do have articles on Force (physics), and on Newton's Laws if that's at all helpful to you after the fact, and if you want to be three dimensional about it, ${\vec {F}}=m{\vec {a}}$--VectorPotential^Talk 16:10, 16 March 2007 (UTC)

Article of Faith in Evolution

Darwin present the theory of evolution in 1858. He said that offsprings of an animal inherit the characteristics of the parents. However in 1858, he does not know the mechanism for the inheritance.

Now, is it not possible to argue (in the year 1858) that the characteristics are given to the offsprings by an external force (ie will of God) and that there is no natural mechanism for inheritance at all between the parent and the offspring.

That is to say to believe in a natural mechanism of inheritance in the year 1858 would definitely require an article of faith.

Oh by the way. This is a philosophy of science question, not an evolution question. I'm not questioning the theory of evolution. 220.239.107.13 12:15, 16 March 2007 (UTC)

It has been stated many times by many people that a belief in evolution (even in modern times) requires a belief in a higher power, whatever you want to call it. It is too much to assume it happened just by chance. However, given the number of stars, the number of planets, the ones that could support life like ours, and the time period over which life was given a chance to begin, the chance of life not happening and evolution not starting is just as small. --Kainaw ^(talk) 12:54, 16 March 2007 (UTC)

Excuse me, but a belief in evolution does not require a belief in a higher power, just like believing that the earth spins around the sun doesn't require a belief in a higher power. It's pure science, and only a healthy view of science is needed. Also, I hate it when people say that it happened "just by chance". Evolution is not a random process, it's not like nature rolls a dice to determine how we function. There are billions of random mutations that do not persist because they are not advantageous. However, a few of them are (which you would expect, with so many mutations, some of them have to be good just by pure statistics), and they since they help the organism to survive they will over time be assimilated into more and more people. In that sense, evolution is highly non-random. Yes, there is a random component to it, but it is a very directed process.

As for the original question: it is true that the mechanism of inheritance wasn't fully understood until the Mendel, or even later when DNA was discovered. However, what Darwin saw was that there was some sort of inheritance process going on (and this isn't really a controversial thing, I mean I bet even creationists can agree that we generally inherit things from our parents, skin tone if nothing else) and that this contributed to natural selection. That's how science works, one guy says "I have this hypothesis about how stuff works. I believe that A, B and C would explain why X happens" So then people listen to him, and weigh his arguments, then they go out and test A, B and C. They either disprove it or give more credence to the theory. It doesn't require a supernatural faith, it just requires and understanding of science. Oskar 14:20, 16 March 2007 (UTC)

Wow! Great response. I just wonder if you actually read my comment. It is in the form "People say X. I feel that Y is an alternative point." Then, you come along and say "Excuse me, but X is wrong!" It makes me feel that you skimmed the first sentence and raced for the "edit" button. --Kainaw ^(talk) 14:50, 16 March 2007 (UTC)

Just a note that Mendel didn't really understand it either — he thought his laws were only a specific and rare instance of heredity; he did not generalize them as universal in function (and even then he had no appreciation, obviously, of the complexity of interactions between unit characters in creating all of the genetic diversity we know and love). This is one of the reasons it wouldn't have made much different if Darwin had actually read Mendel (the other is that Darwin's concern with heredity was based more in his understanding of embryology and recapitulation theory than it was in the strict division of somatype and genotype that we now consider requisite for thinking about heredity). Much of that did not get worked out until later in the 20th century. --24.147.86.187 14:51, 16 March 2007 (UTC)

You don't have to have complete knowledge of something to put something plausible forward about it. Newton didn't know how gravity worked when he explained his universal theory of gravitation, and he admitted as much. Did it matter? For his purposes — and the purposes of science until the early 20th century — emphatically no. The theory still worked for almost everything that was thrown at it, it provided good answers to questions of the time, and even today it is still highly applicable in all but extreme situations (very large distances, very large mass).

Not knowing every element of the world does not make a scientific theory faith-based — in fact, one never knows every element, even in apparently water-tight theories. (We don't even totally understand the mechanism of inheritance today — work on genetics and epigenetics is just as booming as ever, and new things come out every month or two which complicate the "standard" pictures given in bio textbooks.) And it is worth noting that there is faith and then there's faith — some leaps are greater than others. It takes less faith to believe that gravity won't suddenly reverse tomorrow (though, as Hume would point out, one cannot know that with any certainty) than it does to believe in most religious strictures (for which no prior history is verifiable and for which nothing can be in any way directly tested). Calling all of that equally "faith" devalues the term to the point of uselessness, both for the skeptic and the believer.

In any case, Darwin wasn't totally ignorant of heredity. He knew a few things just from observation of pigeon breeders; he wrote an entire book on heredity later. True, he did not have many of the elements we now consider vital for even a rudimentary theory of heredity, but for his purposes even a weak theory of heredity worked fine, without any pretense to knowing the exact mechanisms (which are, again, still not perfectly known). It is worth also remembering that the concern with accurate models of heredity was a much later concern (late-19th century, as opposed to the mid-19th century when Darwin was working on his theory); as with many things, the standards of what would be required for a "theory of evolution" changed over time. For Darwin it was important just to get some of the big ideas out there in a convincing manner in way which distinguished them both from people like Lamarck as well as people like Chambers. Taking science out of its historical context makes for anachronism specifically, and bad philosophy of science in general. --24.147.86.187 14:08, 16 March 2007 (UTC)

To the original question, concisely: it would of course have been possible to claim that. It is equally possible to claim that breathing isn't actually performed by the lungs, but by God directly infusing your blood with oxygen at the point at which your lungs are. And that God was actually seeing things for you, not your eyes and occipital lobe. So on, and so on. Anything can be explained with God, but that's not science. -- Consumed Crustacean (talk) 15:43, 16 March 2007 (UTC)

Darwin knew that his work was incomplete without a mechanism for biological inheritance. He did not expect anyone to take this "on faith". He did in fact suggest such a mechanism, called pangenesis, based on gemmules transported in the bloodstream, but subsequent experiments by Francis Galton showed that this proposed mechanism was incorrect. Even geniuses sometimes get things wrong ! Gandalf61 16:06, 16 March 2007 (UTC)

I suggest that you get a copy of The Growth of Biological Thought and start at Chapter 14. Mayr provides a history of the development of ideas about inheritance and places Darwin's ideas about evolution in that context. --JWSchmidt 18:04, 16 March 2007 (UTC)

Darwin in the last sentence of his "Origin of Species" book, credits the control of Evolution to God. So one in no way needs the doubts that you bring up to bring faith into the picture according to Darwin. Zeno333 05:53, 18 March 2007 (UTC)

"There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved." (first edition) --JWSchmidt 16:47, 18 March 2007 (UTC)

Parrots as artists...

I was just thinking back to something that was raised on the desk a few months ago when we were talking about the manual dexterity of some of the larger parrot species. I mentioned something about how birds such as macaws are capable of holding and manipulating pens, pencils and paintbrushes with their feet and there is no real physical reason why a macaw could not draw something if it wished to.

So, has anyone here heard of a parrot owner teaching their bird to draw or paint (or even just scribble on a piece of paper)? I'd be interested in seeing examples of 'parrot art', if such a thing exists (I do know that someone once taught an elephant to paint)... --Kurt Shaped Box 12:56, 16 March 2007 (UTC)

And chimpanzees Nil Einne 14:28, 16 March 2007 (UTC)

From a quick google I found this [5] (doesn't sound like something that would check their info very carefully but it's probably correct). No mention of parrots but sealions and orang utans. Admitedly the keywords I used were (animal that paint), I'd intended (animals that paint) but made a typo. Nil Einne 14:49, 16 March 2007 (UTC)

I don't know if you've seen the "painting elephants". What they call "painting" is the loosest sense of the word. It means, someone puts a bruch in paint and forced it into the elephant's trunk. Then, the elephant swings the brush around and they put a canvas in the path of the swinging brush to cause the brush to hit it. The end result is a smudge of paint on the canvas. I'm sorry - that isn't the end result. The end result is some tourist paying a lot of money for some paint smudged on a canvas so they can say they have a painting done by an elephant. --Kainaw ^(talk) 14:56, 16 March 2007 (UTC)

That's not altogether different from many pieces of modern art. -- Consumed Crustacean (talk) 15:46, 16 March 2007 (UTC)

I prefer Annie Sprinkle's breast art. --BenBurch 15:52, 16 March 2007 (UTC)

It seems to me it's more then a smudge and she supposedly signs her paintings [6] Nil Einne 16:25, 16 March 2007 (UTC)

Are seagulls dextrous enough to manipulate pens or paintbrushes? The webbed feet might be an obstacle... Nimur 18:09, 16 March 2007 (UTC)

I suppose that it would be physically possible for a gull to hold a paintbrush in its beak. Might take a while to train it to do anything with it though - anyone here got a hand-tame gull? ;) --Kurt Shaped Box 16:06, 17 March 2007 (UTC)

I thought its their use of their beaks, not their claws. I remember seeing somewhere that a parrot's mouth is like their hand. --Wirbelwindヴィルヴェルヴィント (talk) 20:39, 16 March 2007 (UTC)

Parrots (the large ones such as macaws, Amazons, cockatoos and African greys in particular) can use their claws to manipulate objects with a fine degree of precision in the same way as we use our hands (if you ever get the chance, watch a hyacinth macaw cracking Brazils and walnuts). Parrots do frequently use their beaks, mouths and tongues to check out objects though. --Kurt Shaped Box 16:06, 17 March 2007 (UTC)

Most other animals lack symbolic logic, which is needed for all representational art. Non-representational art (modern art), on the other hand (or paw, wing, claw, or fin), doesn't require any talent or skill, so any animal would be just as qualified as a world-renowned modern artist or the average kindergartner. :-) StuRat 21:46, 19 March 2007 (UTC)

Vision Question

I got a question about my vision. I am not color blind but I realized some time ago that one of my eyes sees darker than the other one (not a big difference). Anyone know anything about this? 70.48.255.223 14:00, 16 March 2007 (UTC)

Note wikipedians can't give medical advice. You should seek an appropriate professional if your concerned about your health or eyesight. Personally, I've found that one of my eyes seems to see colour slightler redder then the other. I'm also not colour blind but I do wear glasses because I'm near sighted and have different powers for each eye Nil Einne 14:40, 16 March 2007 (UTC)

No interested in medical advice, I am just wondering if anyone knows what's this called.70.48.255.223 15:22, 16 March 2007 (UTC)

Fine print. Rod cells are the ones that work in low-light conditions and when too many are lost it is called "night blindness". It's impossible to diagnose anything over the internet, if it's bothering you, ask an ophthalmologist -- atropos235 ✄ (blah blah, my past) 16:18, 16 March 2007 (UTC)

Small differences like that are quite common, and I guess it is not a medical "condition" really. One of my eyes sees redder than the other; my right ear hears worse than left; my right foot is a few millimeters longer than left. None of this is noticeable if you do not pay attention to it; but if you do, you notice a lot of things in your body that are almost symmetrical, but not precisely so. See also Symmetry_(biology) Ahtih 00:25, 18 March 2007 (UTC)

Yeah, my eyes do that too. My right eye sees white objects with a slight pinkish tint. (Maybe not) coincidentally, this eye is also weaker than the other when it comes to my glasses. --Kurt Shaped Box 00:41, 18 March 2007 (UTC)

Can eating carrots (since they have vitamin A) improve your vision? Not asking for medical advise, but I am just curious cause I heard it somewhere. And also I heard that if you wear glasses it decreases your vision and gives you headaches instead of improving it? Is any of this true? 69.156.55.58 15:36, 18 March 2007 (UTC)

Radio direction finding

what are the merits and demerits of radio detection finder??? —The preceding unsigned comment was added by Ambuj0542 (talk • contribs) 14:02, 16 March 2007 (UTC).

A radio detection finder is used to find the source of radio signals. If you want to find the source of a radio signal, then it is a good merit. If you want it to heat up your oatmeal, it won't do that very well, and therefore be what I assume you mean by demerit. --Kainaw ^(talk) 14:53, 16 March 2007 (UTC)

The demerits are probably that it costs money. Unless you work for someone who uses them I guess Nil Einne 15:02, 16 March 2007 (UTC)

RDFs also identify your orientation with respect to the radio source. Given two independent radio sources, you can triangulate. Note that as one rotates the receiving antenna, one usually uses the "null" in reception rather than the "peak" in reception as the null is sharper (better defined) than the peak. Non-directional beacons were used in this way by aircraft ADF (Automatic Direction Finding) equipment. RDF/ADF isn't nearly as accurate as other techniques, though, such as LORAN, VORTAC/DME, and, of course, GPS.

Atlant 16:03, 16 March 2007 (UTC)

I wonder if the 'demerits' that the question imagines are things like the problems Laser rangefinders, Radar and active Sonar have with giving away your position while you are searching for someone? In a military context, that's a bad thing. But if that is what the questioner is asking, it's not a problem. RDF is a 'passive' technique. No radio waves of any kind are emitted by the person doing the detecting. SteveBaker 16:23, 16 March 2007 (UTC)

Another demerit is that some simple "direction-finding" technologies are subject to false indications (see electronic countermeasures). Nimur 18:12, 16 March 2007 (UTC)

See Direction finding. Traditional radio direction finding used a loop antenna. It did not accurately indicate distance, only direction, and a signal from the "back of the loop" 180 degrees away could be confused with the correct direction. With 2 or more such locating stations an appropriate distance apart it is a simple matter to draw 2 lines on a map and pinpoint the source, except for issues such as reflection or dispersion of the signal. Edison 15:47, 17 March 2007 (UTC)

Is

Is it possible that life be nonwater based? For example, could we find life that is, say, ethyl alcohol based on another planet?100110100 16:20, 16 March 2007 (UTC)

Yes. It all depends on what nutrients and elements a body needs to survive.

I think the answer to this question is not known. Since we only know about one type of life, it is hard make a convincing argument one way or the other. I'd assume it is possible until someone gave me a good reason to believe otherwise. ike9898 17:33, 16 March 2007 (UTC)

See the article on Alternative biochemistry. -- Consumed Crustacean (talk) 17:35, 16 March 2007 (UTC)

See also definition of life for some discussion on "loopholes." Nimur 18:49, 16 March 2007 (UTC)

I'd say on Friday & Saturday nights there's a lot of ethyl alcohol based life on this planet... -- Scientizzle 20:20, 16 March 2007 (UTC)

This is a bit "out there" - but it's plausible: I expect that if it turns out that humanity is not alone in the universe that we will find that life is most commonly based around electronic or photonic systems - what we would calle 'Artificial intelligence' (AI). Our society has only been playing around with electronics for about 100 years and already we are close to making systems that are intelligent. Once we succeed in doing that, they will rapidly outpace our abilities. Robotic systems can colonise vast amounts of space because they can go into 'hibernation' - and large number of intelligent 'beings' can be stored as raw data in a very small volume and reinstalled into 'bodies' just as fast as an automated factory can crank them out when they arrive at their destination. Their intelligence can be tranmitted as a data stream at the speed of light. If the discovery of AI a common thing in the universe then it follows that "robotic" life will be vastly more common than biological life - and it does not rely on water. SteveBaker 13:06, 18 March 2007 (UTC)

Germination of mustard seeds and the effect pH has on the germination.

Hi i am just wondering what the optimum pH for the germination of mustard seedlings is and biologically speaking why this is. Any information on this matter would be greatly appreciated, Thanks in advance. —The preceding unsigned comment was added by 81.158.228.75 (talk) 17:46, 16 March 2007 (UTC).

The availability of nutrients to plants is partially dependent on soil pH. You might in interested in the article on Soil pH. I don't know about mustard seeds specifically. —Pengo 02:10, 17 March 2007 (UTC)

Cream separation

Hi, I'm currently doing a college assignment on milk processing (Cow's milk) but need assistance with the following please,

If whole milk fat content is 3.9% and when separated using a centrafugal separator to produce exactly 1 litre of fully skimmed milk with a fat content of 0.1% how much cream will i have and what will it's fat content be?

Any help will be much appreciated! Thank you. 195.92.168.166 17:57, 16 March 2007 (UTC)

This sounds like some algebra will help. If the original (unknown) volume is 3.9% fat, that means it is (100% - 3.9%) = 96.1% no-fat skim-milk. This total quantity is going to go into the 1 liter in the next part.

After separation, you get 1 liter of product. Of this, 99.9% is pure skim milk and 0.001% is fat. This means you have 0.999 liters of no-fat product, 0.001 liters of fat.

The amount of total material then is 0.999 / 0.961, ~= 1.0395 liters total whole milk. Of this, 1 liter ends up in the skim-milk, so 0.0395 liters ends up as cream.

Hopefully this explanation has made it more clear...

An alternative is to approximate the finished skim-milk as "100% pure" (since it is close). Then, you can solve as follows:

(1 L skim milk) / (Total Amount Whole Milk) = 96.1% -> Total Whole Milk = 1.0405; this yields 0.0405 liters of cream. This is less accurate but uses significantly less algebra, as well. The result is pretty darn close! Nimur 18:23, 16 March 2007 (UTC)

Plate Tectonics Question

OK, so let's pretend we have two plates undergoing oceanic-oceanic convergence, and the plate that is subducting carries a chunk of continental crust with it. Does the denser oceanic plate stop being subducted under and start subducting under the continental crust? Or does this create a stalemate for a few (in geologic time) years? - AMP'd 18:16, 16 March 2007 (UTC)

Happens all the time. The little hunk of floaty stuff stays on top, and either forms Japan, or gets tacked on to a continent. Google 'continental accretion' and 'geologic terranes'. --Zeizmic 19:04, 16 March 2007 (UTC)

Thanks. So does the continental crust still get subducted under? How fast does this new subduction happen? - AMP'd 19:49, 16 March 2007 (UTC)

No, the 'froth' of the world, which is composed of silicates, never goes back under. The only thing that goes under is cold oceanic crust, full of water. --Zeizmic 21:53, 16 March 2007 (UTC)

And 'polarity flips' such as AMP'd inquires about (the switch from one oceanic plate subducting, to the other) are also fairly common in complex places like the SW Pacific. And sometimes, bits of oceanic crust do get pushed upon continental crust (see Ophiolite) but it is not correct to think of that continental crust as subducting beneath the oceanic crust - the whole package, continental + slices of oceanic on top, stays high, just as Zeizmic says. All these processes take millions to tens of millions of years. Cheers Geologyguy 22:07, 16 March 2007 (UTC)

Alright, that was what I was talking about. Sorry if you all thought that I meant that the continental crust would subduct - I knew that it "floats" all along. - AMP'd 22:10, 16 March 2007 (UTC)

Racist biology

Hi folks, I wanted to ask you which are the medical conditions which have a racial predisposition.

I think your are misinterpreting the word racist here, nevertheless, many genetic diseases show a racial corrolation. For example, predisposition to sickle cell anaemia is associated with certain races, (that is to do with the geographic history of those people). Melanoma occurance also shows racial bias, but that is do to with skin colour, as is tuberculosis. Certain ethinic groups, like Pacific Islanders, are particularly predisposed to obesity (in combination with a Western diet). Rockpocket 20:17, 16 March 2007 (UTC)

Sickle cell anaemia and the obesity you mentioned are environmental factors which modeled the genetics of that particular population, not based on race as such. I was interested in condition like melanoma where the racial lack of melanin in caucasian doesn't protect the skin from radiation. I didn't understand how tubercolosis differs.

All genetic conditions are a result of genes interacting with environmental factors, there is no such thing as an entirely genetic disease. For example, in the absence of UV light (the environmental factor) there would be no difference in the predisposition for melanoma between caucasian and other races. Also, "race" as a concept really has nothing to do with melanoma predisposition. The corrolation is with skin tone, which is widely corrolated with race, but not a strict definition of race itself. Consider how an albino in Africa will have an extremely high risk of melanoma, yet they his non-albino brother will have an tiny risk. Being an albino doesn't change his race, but lacking melanin does change his risk. The concept of race in terms of genetics is an extremely controversial subject, there is some discussion on the subject here.

By the way, the risk of TB is also linked to skin tone, exposure to UV and vitamin D production. [7] Rockpocket 00:17, 17 March 2007 (UTC)

Don't forget that these things are also probabilistic — they tell you nothing about individuals, just averages over groups. --24.147.86.187 01:48, 17 March 2007 (UTC)

An interesting angle on sickle-cell anemia, which disproportionately affects people from Africa, is that it's actually a net benefit to a population. Asymptomatic carriers of the disease get some immunity from the African disease malaria, which outweighs the harm that actual sufferers of the disease contribute to the fitness of a species. Tay-Sachs disease, which disproportionately affects Ashkenazi Jews, was at one point thought to give some protection against tuberculosis, a popular disease in European ghettos. There are other population-specific diseases with up sides, but I can't remember them just now. --TotoBaggins 01:55, 17 March 2007 (UTC)

Interview

I wanted to email interview someone from your organization for an upcoming research paper for my sociology class, at the University of Houston Downtown. I am currently writing about alcoholism. I would like to quote some of your responses in my paper. Questions: What do you think the best means for prevention of alcoholism is? Have you personally been affected by alcoholism and how? How do you feel about new marketing ideas such as motion censored unrinal cakes in male restrooms at bars that tell talk and remind you to call a cab or a friend to drive you home? If you could help me it would be greatly appreciated!! —The preceding unsigned comment was added by 63.115.56.2 (talk) 20:16, 16 March 2007 (UTC).

3) I would be incredibly irritated by the nagging of a urinal cake, to say the least. Particularly if six of them are going off at once when the restroom is full towards the end of the evening. It's a clever idea, though. Could they measure the alcohol content of your urine and react appropriately? Could they focus the sound on the individual so it's less annoying for everyone else? --Sam F., 20:27, 16 March 2007 (UTC)

You might also want to be aware that we are not officially part of an organization. The Wikipedia Reference Desk is entirely staffed by volunteers. The Wikimedia Foundation is the closest thing to an official representative; but they are not at all involved in the content of the articles. Keep this in mind when quoting "wikipedia" - it is exactly as effective as an on-the-street interview. You might get a knowledgeable scientist, or maybe not; and you can't really tell for sure sometimes. Nimur 20:31, 16 March 2007 (UTC)

• What do you think the best means for prevention of alcoholism is?

Public awareness. If friends and relatives of the potential victim could spot the early signs and do something about it before it gets to a full-scale problem then the whole issue could largely be avoided. The problem is that our society doesn't see a problem with someone who drinks somewhat too often - but not so often that it's "obviously" beyond control.

• Have you personally been affected by alcoholism and how?

No.

• How do you feel about new marketing ideas such as motion censored unrinal cakes in male restrooms at bars that tell talk and remind you to call a cab or a friend to drive you home?

Those are for the avoidance of drunk driving - not alcoholism. But I would be very surprised if they had any effect at all. People who drive drunk are either unaware of the legal limits or firmly believe that they are fully in control of the vehicle when they are knowingly over the limit. They don't need "reminding".

I hope this helps. SteveBaker 12:57, 18 March 2007 (UTC)

• What do you think the best means for prevention of alcoholism is?

Identify the genes which cause it, then do routine testing and warn susceptible kids before they start to drink that, if they do, they will likely become alcoholics.

• Have you personally been affected by alcoholism and how?

Yes, my uncle was killed by a drunk driver.

• How do you feel about new marketing ideas such as motion censored urinal cakes in male rest rooms at bars that talk and remind you to call a cab or a friend to drive you home?

That's not enough, everyone driving away from a bar should be tested by cops and arrested if they are drunk. In the US, leaving a bar and driving a car should be considered probable cause to search the suspect's blood for alcohol. StuRat 23:16, 19 March 2007 (UTC)

Strong agree. Nimur 23:22, 19 March 2007 (UTC)

ET's map?

Hi. I am again asking a question. This image

seems to show a map of the stars known to the greys to contain possibly inelligent lifeforms. Many people claim that the Zeta Reticuli system are home to the greys, and the stars may be suitible for life. We know that Sol, or the sun, does contain intelligent life. 82 Eridani is quite similar to the sun, and has one of the highest known probablities of harbouring life. 86 Gliese has a confirmed planet, and is quite similar to both the sun and zeta reticuli. Alpha Mensae is a star similar to our sun and some of the other stars. All of these stars have articles except for one. Is it a coincidence, or do these stars all have potential for ET's? What do you think? Thanks. AstroHurricane001^{(Talk+Contribs+Ubx)} 21:03, 16 March 2007 (UTC)

Wikipedia is not the place for speculation. (Aliens use British spelling?) Clarityfiend 21:13, 16 March 2007 (UTC)

"Known to the greys"? A guess based on a single account? If you think there is a conspiracy, perhaps you should ask the people who started those articles if they're working for the aliens! Seriously though, you should be dubious of those probabilities for life, too, as they were compiled 25 years before we found any exoplanets and started learning what the real statistics are. 82 Eridani, for example, is metal deficient, making the presence of planets unlikely. Spiral Wave 13:41, 17 March 2007 (UTC)

But we don't know what aliens are like, they might not need metal :] HS7 20:37, 17 March 2007 (UTC)

I like the idea of gigantic hydrogen-based entities living in the atmosphere of gas giants. :) --Kurt Shaped Box 20:41, 17 March 2007 (UTC)

Well, we could have that I suppose! But then they wouldn't be greys... unless the greys have developed shape-shifting capabilities, hmm.... They may have trouble building spaceships out of hydrogen, helium and methane, though. Spiral Wave 15:26, 18 March 2007 (UTC)

What, you thought that nebulae were just the remains of dead stars? ;) --Kurt Shaped Box 21:43, 18 March 2007 (UTC)

Also, what is this map? Is it a two-dimensional projection of the locations of these stars? Clearly it is not the night sky as visible from earth, since it contains our own sun. It seems like it would be entirely useless to have a 2-dimensional projection for astronavigation, especially if the focal plane is seen from an arbitrary point in space which is obviously quite far out of the plane of the star systems of interest. Nimur 22:36, 17 March 2007 (UTC)

A 2 dimensional representation of a 3D map, drawn from memory by a victim of alien abduction, under hypnosis (apparently). --Kurt Shaped Box 22:44, 17 March 2007 (UTC)

How about changing the question to, could any of those stars support life? Also, FYI this is a map claimed to be the view of the nearby stars from a planet orbiting Zeta Reticuli 2, looking towards Zeta Reticuli 1, and I doubt it's entirely 2-dimentional. Thanks. AstroHurricane001^{(Talk+Contribs+Ubx)} 22:51, 17 March 2007 (UTC)

I suppose it depends on whether we believe that it is necessary for a star system to contain planets similar to our own in order to support life. --Kurt Shaped Box 23:14, 17 March 2007 (UTC)

Well, assuming it does, then it's perfectly possible that those systems contain planets. You don't even need planets "similar to our own", for example, a rocky moon around a gas giant may do just as well. However, for the three systems you mentioned explicity, at least, there have been no planets found yet. As I said before, 82 Eridani is the least likely, being metal deficient and probably population II. There's no reason why the other two couldn't though, and they represent fair candidates for planets; right mass, moderate or high metallicity, no short-period binary companions.

I want to add that we don't know what the statistics for the terrestrial/gaseous ratio is yet, though. It may be that systems without gas giants rarely form terrestrial planets - in which case, since nothing has been found there yet, it would be unlikely. Or there may be barely any correlation at all, in which case they'd be very promising. You'll have to wait until the Terrestrial Planet Finder and/or Darwin have been built. Spiral Wave 15:42, 18 March 2007 (UTC)

I still don't like this map. If it were from a planet orbiting ZR2, and it shows ZR2 on the map, that would mean it has to be drawn looking towards the daytime sun (i.e. during the day on the planet, looking towards Zeta Reticuli 2). Not only would it be HIGHLY seasonally variable (since the position of the sun with respect to the background stars changes during the course of a single year), it would be pretty impossible to see those stars behind the sun, (if the atmosphere is indeed diffusive to light, a requisite for earth-like biological life). Naturally we could go on dozens of hypothetical tangents about it, nitpicking every detail of the map, but the final conclusive answer is that this map is entirely fictional. Nimur 01:48, 18 March 2007 (UTC)

Determining Our Expressed Genes

Hi, what selects or determines which genes will be chosen to be the expressed genes? How does that work? —The preceding unsigned comment was added by 67.126.241.194 (talk) 21:21, 16 March 2007 (UTC).

Scientists are still learning about this, but you might want to see Gene expression. Johntex\^talk 22:23, 16 March 2007 (UTC)

As a starting point, read Gene expression, Intron, Exon. The mechanisms vary between organisms, simpler bacteria use "riboswitches", pieces of RNA, to control expression by shutting down expensive genes (ones that take lots of energy and resources) when they are unneeded; there was an article about it in the Jan 07 issue of SA. The question still isn't fully answered and one of the most intriguing in science. -- atropos235 ✄ (blah blah, my past) 22:33, 16 March 2007 (UTC)

Also note that different genes are expressed in different cell types and at different times during development. Presumably every single gene is expressed somewhere at some time. You may want to check the entries on Cell type, Cellular differentiation, and Developmental biology. Gorm 09:04, 17 March 2007 (UTC)

Transcription factors Aaadddaaammm 06:06, 18 March 2007 (UTC)