Wikipedia:Reference desk/Archives/Science/2009 February 21

= February 21 =

moving charges
Do accelerating charges produce magnetic field ?? I thought any moving charge would do {biot-savart law} but a man tells me that only charges that move with uniform velocity produce magnetic field. Is it true ? --scoobydoo (talk) 05:43, 21 February 2009 (UTC)
 * No, it's not true. As our article on magnetic fields points out, all moving charges produce a magnetic field. A charge that is accelerating is moving and so produces a magnetic field. The gentleman you were speaking to may having been referring to the fact that the Biot-Savart law covers the case of a charge which is moving with a uniform velocity, i.e. one that is not accelerating. - EronTalk 05:58, 21 February 2009 (UTC)

Then,i suppose, the accelerating particle should produce time varying magnetic field?Do you know any such example ?? i've searched but can't find any example/application of a magnetic field produced by accelerating charges. Also i wanted to know whether biotSavart Law has any limitations,ie whether it can be applied in all situations.{like newton's laws of motion in inertial frames only}--scoobydoo (talk) 10:00, 21 February 2009 (UTC)


 * The article, Liénard–Wiechert potential, explains in horrible detail all the mathematics you need to calculate the the electric and magnetic potentials and fields due to a single moving charge with arbitrary velocity. These formulations are essentially representations of the conceptual bridge between Maxwell's equations and special relativity.  For any charge q with vector velocity v(t), you can derive an analytic expression for electric and magnetic potentials at all points in space at all times t.  The equations dictate the propagation of those fields through time, and implicitly contain a relative velocity with respect to the source particle.  Noting that the speed of light is constant, the speed of propagation of the fields is also constant; and this must be seen from all inertial reference frames via the concept of retarded time.  Nimur (talk) 13:46, 21 February 2009 (UTC)


 * I wondered why the last eight years seemed so long... the concept of retarded time explains it perfectly. arimareiji (talk) 04:23, 22 February 2009 (UTC)

thanks a lot--scoobydoo (talk) 04:45, 22 February 2009 (UTC)

by what year is the amazon rainforest expected to be completely logged/destroyed?
when's it gonna happen?Troyster87 (talk) 07:11, 21 February 2009 (UTC)


 * We cannot answer "When's it gonna happen?" because the Reference Desk is not a crystal ball. We do not foretell the future.  Go find some gypsy for fortune teller willing to take your money and ask him or her.
 * As for when it is expected to happen... That depends entirely on who you ask. Most people do not expect it to happen.  Others will tell you that it will be happen next week.  For somewhat sane opinions on the matter, see Deforestation of the Amazon Rainforest. --  k a i n a w &trade; 07:46, 21 February 2009 (UTC)


 * It may not happen at all because some areas may be kept as nature reserves or parks, and it may also recover before it's destroyed. More likely for it's complete destruction would be by something like climate change: too much heat or a severe ice age. Looking at the figures from the source of the above article, the mean average annual loss in Brazil from 1988/2006 was 18 122 km2 (344 317 2 / 19). In 2006 there was about 340 0254 km2 left, so at the average rate it would take about 188 more years, or in the year 2194 - tho that's not a good way of estimating because the unknown variables are too many. -- Jeandré, 2009-02-21t08:43z


 * A couple problems with just taking the current rate of deforestation and extrapolating that to determine when all the forest will be gone:


 * 1) As forest becomes more rare, it becomes more valuable, say as a tourist attraction, and thus there will be more incentive to keep it.


 * 2) A deforested are can become forested again. This can happen naturally to an area which is abandoned (let's say it was deforested during mining, then the mines all played out and everybody left).  Trees can also be intentionally replanted for future logging, to make a place more attractive to tourists, to stop soil erosion, etc. StuRat (talk) 19:34, 21 February 2009 (UTC)


 * And from the opposite side:
 * The "critical mass" aspect - surely no one would argue that a few square meters of "rainforest" can survive very long. The trouble is, no one knows where the dividing line lies between survivability and eventual extinction. See Population bottleneck.
 * Technology - Villagers getting firewood don't do nearly as much damage as a farmer clearing land don't do nearly as much damage as an airplane spraying defoliants. Which will predominate is variable, especially in the age of genetically-engineered crops.
 * Anthropogenic climate change, AKA global warming - a hundred years from now, plains may be coastland and rainforest may be plains. arimareiji (talk) 20:41, 21 February 2009 (UTC)


 * 3) I'd expect global warming to actually help, as forests will be able to grow where none were possible before, due to permafrost, such as northern Canada and Siberia. We could eventually get forests in Greenland, and maybe even Antarctica, some day. StuRat (talk) 21:28, 21 February 2009 (UTC)
 * Not impossible, but rather implausible. And Canada will not grow Amazon rainforest, no matter how much the climate changes ;-). --Stephan Schulz (talk) 23:02, 21 February 2009 (UTC)


 * Actually, the Amazon rainforest is widely predicted by computer models on global warming to collapse if global temperatures rise more than 2C (3.6F), and such a temperature rise is likely before 2100. Temperature and vegetation models both predict this, and some of this extra temperature rise in maps is depicted in our article, global warming. In at least one book I've read on GW (and I've read about a dozen by now), the prediction is that once global temperature rise exceeds 2C, a "firestorm", literally a wall of fire, would sweep across the Amazon basin from the northeast inwards, turning the region into desert. In another book, it depicted three possible scenarios in the 21st century: a) the collapse of the Gulf Stream; b) the collapse of the Amazon rainforest; or c) the release of methane clathrates from the seabed. The book claimed that "c)" was the least likely to occur this century, but if peliminary results from the AGU are correct, then the clathrates are already being released. I don't think deforestation will be quick enough to destroy the Amazon rainforest before that potentially happens. ~ A H  1 (TCU) 00:27, 22 February 2009 (UTC)
 * Dadgummit, why'd you have to not provide an explanatory link to AGU? :-) arimareiji (talk)
 * I believe this is it: American Geophysical Union. --Scray (talk) 04:08, 22 February 2009 (UTC)


 * "Widely predicted" is too strong. Some models show a catastrophic collapse of the rainforest this century (including the one pictured), but a majority of current models have it continuing to be present through 2100.  Eventually climate change may make that biome unsustainable, but there isn't a lot of agreement on how much warming must occur before that happens.  Dragons flight (talk) 19:35, 22 February 2009 (UTC)

Did Ross actually deserve his Nobel in 1902?
Grassi challenged the Nobel awarded to Ross,the India born doctor claiming he had a better claim!Does the wiki community agree?(Ramanathan) —Preceding unsigned comment added by 212.247.70.129 (talk • contribs) 06:57, 21 February 2009
 * Have you a source that we should look at? Cuddlyable3 (talk) 14:03, 21 February 2009 (UTC)
 * From the top of the page: "The reference desk does not answer requests for opinions..." There are other internet sites that are appropriate for discussing personal opinions.  The Reference Desk is for answering factual questions.  You may be interested in searching for internet forums where topics such as Nobel prizes or scientific claims are discussed.  152.16.59.190 (talk) 04:52, 22 February 2009 (UTC)
 * You might want to try your luck posting this question on the entertainment RD, here. Not only would you probably get a better answer, but the entertainment desk looks a little sparse; it could use an extra post or two.  -Pete5x5 (talk) 06:41, 22 February 2009 (UTC)

Scientists with distinguished contribution to literature
Apart from Bertrand Russell who won teh Nobel in literature are ther any other scientists who have distinguished themselves in this manner?(Ramanathan) —Preceding unsigned comment added by 212.247.70.129 (talk • contribs) 07:01, 21 February 2009


 * In what manner? As far as I know, no other scientist has won the Nobel Prize in Literature. But many scientists have also been successful popular writers. Richard Feynman has written two widely read collections of autobiographic sketches. Stephen Hawking has popularized his research very successfully, and so has Richard Dawkins. Vernor Vinge, probably best known for his acclaimed science fiction, is a computer scientist. Isaac Asimov was a biochemist and held a professorship, and E. E. Smith was a practicing food scientist. John Norman is a professor of philosophy (if you call this a science, and if you consider his writings literature). These are just some examples from my bookshelf (and this may give away too much about my reading habits ;-). --Stephan Schulz (talk) 11:20, 21 February 2009 (UTC)


 * Well Bertrand Russell did.and he was a scientist that is why I asked the question.And my colleagues tell me Omar Khayyam was another(Ramanathan)


 * Robert L. Forward - Famous physicist and sci-fi writer. There are a LOT more. SteveBaker (talk) 14:08, 21 February 2009 (UTC)


 * Stephen Jay Gould, evolutionary biologist and paleontologist, perhaps just a famous as a writer of philosophy, c.f. Rocks of Ages. Not a writer, but Alexander Borodin was notable both as a chemist (his work on aromatic compounds was seminal, right up there with Kekule) and as a composer (he was one of the Mighty Handful of 5 great Russian composers.  --Jayron32. talk . contribs  19:46, 21 February 2009 (UTC)
 * Carl Sagan -- The Demon-Haunted World, Cosmos (book), The Dragons of Eden, Contact (novel) and many more. --NorwegianBluetalk 22:17, 21 February 2009 (UTC)
 * And if mere physicians count - we have an entire article: Physician writer. Personal favourites: Oliver Wolf Sacks -- The Man Who Mistook His Wife for a Hat and P. C. Jersild: A living soul and The house of Babel (the latter two, regrettably redlinks, but available in English). --NorwegianBluetalk 22:44, 21 February 2009 (UTC)


 * Though I would hesitate to call much of the above "literature"... being a popular science writer, or able to write a witty autobiography, is not at all in the same class as a Nobel Prize in Literature... Ernst Mach, by contrast, was both a famous physicist, but perhaps an even more famous philosopher/author during his day, not writing up popular accounts of science, but making strong arguments about the nature of science and experience, to the point where none other than Lenin himself decided to denounce his work. Gould, Feynman, Dawkins—good writers, all, but their literary works are not exactly world-shaking... --98.217.14.211 (talk) 20:11, 22 February 2009 (UTC)
 * Chemist Primo Levi was a literary man. The Nobel prize in Lit isn't the only mark of distinction imo. Julia Rossi (talk) 10:53, 23 February 2009 (UTC)
 * C. P. Snow was well-regarded as a novelist, as well as being a physicist; he won the James Tait Black Memorial Prize, one of Britain's most distinguished literary awards and taught at Cambridge University. --Maltelauridsbrigge (talk) 11:48, 23 February 2009 (UTC)
 * Empedocles, Aristotle, Francis Bacon, Erasmus Darwin, Miroslav Holub. N p holmes (talk) 13:12, 23 February 2009 (UTC)

Hybrid eclipse: both annular and total at the same place?
"A hybrid eclipse (also called annular/total eclipse) transitions between a total and annular eclipse. At some points on the surface of the Earth it is visible as a total eclipse, whereas at others it is annular." -- Solar eclipse.

Is it possible to, from one specific place on Earth, see an annular eclipse become a total eclipse (or the other way) if standing at the correct place during a hybrid? -- Jeandré, 2009-02-21t11:14z


 * The only real option I can imagine is for an observer watching an eclipse (lunar or solar) at the moment of the solar supernova.  I assume the pleasure to be rather short lived.   --Cookatoo.ergo.ZooM (talk) 13:36, 21 February 2009 (UTC)
 * Our Sun is nowhere near big enough to go supernova, please read the articles you link to. --Tango (talk) 15:05, 22 February 2009 (UTC)


 * The answer is yes, and in situations much more common than that proposed by Cookatoo. There will be a very narrow region in the path of a hybrid eclipse where it transitions from total to annular (or vice versa).  At the midpoint of that region, two minutes of totality would be one minute of an actual total eclipse and one minute of an annular. &mdash; Lomn 14:42, 21 February 2009 (UTC)


 * The answer is "No." During an eclipse, at any one point on Earth, the Moon covers up a certain percentage of the Sun. Let us suppose the Moon is covering 99% of it, thus presenting an annular eclipse. In order for the eclipse to become total, one of four things (or a combination of them) would have to happen: (1) the Moon suddenly grew larger, (2) the Sun got smaller, (3) the Moon got closer to the Earth, or (4) the Sun got farther from the Earth. Since all four are impossible to the extent needed in the few minutes of an eclipse, it can't happen. B00P (talk) 11:20, 22 February 2009 (UTC)


 * The answer is "Maybe". In the region where a hybrid eclipse was transforming from annular to total, there has to be a gray area of some sort, where Baily's beads become more and more numerous around the sun, leading to ambiguity in defining it as annular or total. Not everything can be pigeonholed so easily :-D - Running On  Brains  21:30, 22 February 2009 (UTC)
 * And by "annular to total", I of course meant the other way around. - Running On  Brains  01:21, 23 February 2009 (UTC)
 * Well, yes, I did think of that knife-edge case - note that I specified 99%, not 99.9999% - but then where does one draw the line between annular and total? So, I'll grant that RunningOnBrains is correct, but still maintain that the answer is "no" in any meaningful way. B00P (talk) 06:03, 23 February 2009 (UTC)

Oh Jeez - what a lot of crappy answers! No, no, NO!! Think about the reason that some eclipses are annular and some are total. It is because the earth's orbit around the sun is not a circle. It's an ellipse. Hence at some times of year the earth/moon system is closer to the sun and at other times we're further away. Hence the sun appears to be slightly larger or smaller. Hence the moon sometimes completely covers the sun at the moment of 'totality' and at other times of the year doesn't completely cover it. It has absolutely nothing to do with where you are on the surface of the earth. It might seem that the moment just before or just after a total eclipse is "annular" - or if you are not quite in the path of 'totality' that it might seem to be 'annular' but in those cases, the ring of sunlight around the moon won't be a complete circle which is the defining feature of an annular eclipse. A true annular eclipse cannot precede or follow a total eclipse because the distance the earth travels around it's orbit is negligable over the few minutes of totality or annularity. QED. SteveBaker (talk) 14:08, 23 February 2009 (UTC)
 * Your FACE is a crappy answer. :-P - Running On  Brains  19:00, 23 February 2009 (UTC)
 * WP:NPA please. SteveBaker (talk) 23:31, 23 February 2009 (UTC)
 * WP:NIHEITSIUHTPOWYHBUH please. 79.66.56.21 (talk) 16:54, 25 February 2009 (UTC)

derivation of e = mc squared
please visit this link :

the e = mc2 has been derived in a very easy way. But my doubt is that the 'm' in the derived equation is actually the mass of the photon. It means that photons and hence, energy has mass. But how can you say that any mass has energy equal mc2? 1kg of gold costs a lot. But 1kg of any mass doesn't cost that much. A photon may have some mass equal to E/c2. But anything with mass m may not have energy equal to mc2. Please correct me if i am wrong anywhere. I have understood the derivation but i got this doubt. I also know that matter reacting with antimatter produces energy equal to mc2. Please explain my doubt.Also I am just 14 years old and so, please explain in a nice way. --Harnithish (talk) 11:31, 21 February 2009 (UTC)

Actually, E=m*c^2 only holds for non-moving objects (that is, objects that aren't moving in the reference frame of the person who calculates E=m*c^2 ).

The more general formula is E=gamma*m*c^2, where gamma is the Lorentz factor gamma=1/sqrt(1-v^2/c^2).

Another formula, directly applicable to photons is

E^2=m^2*c^4+p^2*c^2

where p is the momentum of the particle

p=gamma*m*v

In other words, the energy of the photon is not due to its mass (m=0) but due to its momentum.

(Some physicists consider mass to be velocity-dependent and define the relativistic mass m=gamma*m0 where m0 is the rest mass, the mass an object has according to an observer in whose reference frame the mass is at rest. Photons then, have zero rest mass but not zero relativistic mass.)

Summary : no, you can't apply E=m*c^2 to a photon, because the photon is not at rest in your frame. —Preceding unsigned comment added by 81.11.173.78 (talk • contribs) 09:50, 21 February 2009


 * In answer to the other question (if it is a question), equal masses of substances can have different values despite having the same energy because we can't convert between them. For example, an apple's worth of energy could power vast parts of the world, and therefore be worth a lot. however, we can't convert the apple to energy (yet), so it's not worth that much. - Jarry1250 (t, c) 13:57, 21 February 2009 (UTC)


 * We talk about the photon as though it were a little ball that someone could catch in a butterfly net and look at. In fact it is only a conceptual model that has been constructed to satisfy the need to explain how electromagnetic energy propagates seemingly without any mass transfer. Cuddlyable3 (talk) 14:00, 21 February 2009 (UTC)

what is "Vital fluorescent staining" ?
Google give plenty of search results for "Vital fluorescent staining", but they're all "Application of a Vital Fluorescent Staining...", "Development of a vital fluorescent staining...".

I can more-or-less figure out what it should be from the context in which I read it, and from this wikipedia article: http://en.wikipedia.org/wiki/Staining

Presumably it's some kind of indicator that can be added to bacteria cultures and differentiates between living (vital) and dead bacteria? —Preceding unsigned comment added by 81.11.173.78 (talk • contribs) 09:41, 21 February 2009


 * Your sense is correct, but this is not limited to bacteria. You'll find a lot of useful information using Google (or other search engine, even Pubmed) with the example of Acridine orange and "vital".  I must agree, though, that our content on WP is either hard to locate or lacking.  --Scray (talk) 16:12, 21 February 2009 (UTC)


 * Vital staining (vital in this case referring to vita, Latin for life/living) of any type is that which is done on live (as opposed to fixed tissue. It can involve chemicals, like acridine orange mentioned above, or the addition of markers (like fluorescently labelled antibodies or tagged proteins, e.g. for FAC sorting) to the outside of the cell. -- Flyguy649 talk 20:59, 23 February 2009 (UTC)

Hypothetical lifeforms on earth
What might life be like on earth if earth was orbiting a blue giant star instead of the sun? (that is if the earth was far enough away from the blue giant to prevent it from being too hot for life)? Also what might the landscape (aside from the earth having no moon) and life be like on earth (and possibly thea) be like if they never collided 4.4 billion years ago? —Preceding unsigned comment added by 99.146.124.35 (talk • contribs) 10:14, 21 February 2009


 * Blue giant is just one short stage during the death of a star. Only very massive stars become blue giants and such large stars don't live as long as our Sun. There probably wouldn't be time for life to evolve, at least not complex life. There has been a lot of discussion about what the Earth would be like without the Moon - basically it would less stable (the axis of rotation would move around more) and there would be much weaker tides (there would still be some due to the Sun). It's impossible to say what Theia would be like, it would have to have been thrown out of Earth's orbit somehow and what would happen to it depends on where it ended up. I don't think the Earth would be much different otherwise, it would be slightly smaller, but probably not sufficiently smaller to make a great deal of difference (gravity wouldn't be very different, since its smaller mass would be partially offset by the surface being closer to the centre). The length of a day would be very different (it's difficult to guess what), and the axis might be in a very different place (although it would be moving quite a bit anyway, without the Moon). --Tango (talk) 14:37, 21 February 2009 (UTC)


 * Some external sources for the no-moon effect:  &mdash; Lomn 14:38, 21 February 2009 (UTC)


 * For any reader unfamiliar with Theia, see the giant impact hypothesis. StuRat (talk) 19:25, 21 February 2009 (UTC)


 * The last episode of The Future is Wild, The Tentacled Forest left off at 200 million years later. What might the next lifeforms and landscapes on earth be (assuming that the shows predictions about the first 200 years were correct) after the time when the show left off?--99.146.124.35 (talk) 14:58, 22 February 2009 (UTC) Perhaps 250 million 300 million 400 million years 1 billion years in the future?--99.146.124.35 (talk) 15:02, 22 February 2009 (UTC)

As to the first question, life would have to adapt to the higher percentage of UV radiation, so you'll see less life in the open and more animals digging themselves in, probably thicker skins and more eye protection. --Ayacop (talk) 16:03, 22 February 2009 (UTC)
 * Or maybe just darker skins. Lots of melanin would do the job, you don't necessarily need a thick skin. --Tango (talk) 16:25, 22 February 2009 (UTC)

Why does the iris have a colour?
I'm wondering why the human iris has a colour. Not so much from a physical standpoint (the wikipedia article on iris colour is quite thorough on that part) but rather from an evolutionary standpoint. Why isn't the iris just white like the sclera? What function do all those colours have? PvT (talk) 16:10, 21 February 2009 (UTC)


 * My guess is that it's the same reason as hair color: complex, somewhat linked to other pigments (e.g. skin) and ethnic history/climate, and especially subject to conjecture and junk science. --Scray (talk) 16:40, 21 February 2009 (UTC)


 * I realized that answer to part of your question is that the iris is part of the uvea, the pigmented layer between the sclera and the retina. This helps to understand that the iris is part of a pigmented layer of the eye, but precisely why the iris appears the way it does is more complex than that.  --Scray (talk) 16:47, 21 February 2009 (UTC)


 * I believe the pigment is important for making the iris opaque, this means like only reaches the retina from the pupil resulting in better quality vision. Albinism might be useful (if you want to know why something is the way it is, it often helps to look at what happens when it isn't). --Tango (talk) 17:38, 21 February 2009 (UTC)


 * I understand that the iris is there to regulate the amount of incoming light. However why specifically does the iris have a colour as opposed to being white like the neighbouring tissue. I think Scray helped me out quite a bit. If the iris is an extension of the uvea then it makes sense that it would appear different from the sclera (it's a different type of tissue afteral). What puzzles me is that if the iris is only there to regulate the size of the pupil than why does it need any specific colour. To me it seems that to fulfill this job the iris doesn't need to have any specific colour, as long as it's not translucent. PvT (talk) 17:54, 21 February 2009 (UTC)


 * Precisely. It's also fascinating to note how variegated iris color is (just look at the image on that page, or take a close look at a loved one's).  Is that beneficial or an accident of embryology?  I have a feeling that this could lead into the field of psychology, etc - very complex and currently unanswerable in any concrete way.  But certainly worth asking!  --Scray (talk) 18:12, 21 February 2009 (UTC)


 * The trouble with using albinism as an illustration is that it's not isolated to the iris. The entire pigment layer is important to normal eye development, probably because light bouncing around inside the globe is as (or more) problematic as light passing through the iris.  Without separating the effects of light transmission through the iris and light reflection within the eye, the benefits of iris pigmentation cannot be assessed at all.  --Scray (talk) 17:49, 21 February 2009 (UTC)


 * I'd say that eye color, among many other features, is used to identify individuals. This is important to any social animal, as identifying different individuals is key to survival ("stay away from the one with the dark brown eyes, he's overly aggressive").  And, since humans use visual cues far more than smells or other senses, it would make sense that we would have more visual cues to distinguish one another than other animals that doesn't rely so heavily upon the visual. StuRat (talk) 19:14, 21 February 2009 (UTC)


 * Our article on Eye color, not yet linked in this discussion, has some really good discussion of the genetics and physiological aspects of eye color. --Jayron32. talk . contribs  19:37, 21 February 2009 (UTC)


 * Genes that influence eye colour are involved in other processes. Consider, for example, HERC2 and OCA2. They are also involved in regulating - among other things - skin colour. So its entirely possible that different eye colours are a selective side effect of pressures on the genes in other functional contexts. Sexual selection may also have driven variation. Note also the the variation in eye colour is largely due to physical, schemochromatic effects. So light bouncing around off structural, protein fibres and a few melanosomes gives eyes a blue colour. These fibres and melanosomes have other biological roles, so it could simply be that their colour is a subsequence of that. Rockpock  e  t  00:59, 22 February 2009 (UTC)


 * Having the whites showing seems to be something humans have evolved specially so one can see where another person is looking. Most animals don't have any white showing so it probably is a bad idea normally though I'm not sure why. Presumably for the same reason as the skin is coloured - to protect from UV light. Dmcq (talk) 16:26, 27 February 2009 (UTC)

Dysfunction in the instinct of nature
So I assume that all species have instincts to protect and nurture their young etc. but was there ever any natural deviant in which any living being seemingly didn't work instinctually and did the opposite? Like instead of nurturing, hindering. If there was how could they naturally bear offspring in the first place if apparently their instincts malfunction? 94.196.9.90 (talk) 17:25, 21 February 2009 (UTC)


 * You mean, like parents that eat their young? Another article here. Like ROUS's, I don't believe they exist. ;-)  --Scray (talk) 17:46, 21 February 2009 (UTC)


 * Every animal is capable of it in conditions of high stress and overcrowding, from what I've heard. Any relationship between this and Jerry Springer modern human society is purely coincidental. ;-) arimareiji (talk) 18:23, 21 February 2009 (UTC)


 * One could also claim that the instincts of self-preservation and species-preservation can come into conflict. After all, in times of scarcity, self-preservation may take over.  After all, I can always have sex again.  But if I don't live through this winter, maybe not... Just a WAG... --Jayron32. talk . contribs  19:32, 21 February 2009 (UTC)


 * The goal is always to have as many of your offspring as possible reproduce, but it doesn't matter which ones. If your current young aren't likely to survive that long whatever you do, caring for them is a waste of resources that would be better spent making sure you survive long enough to try again. I think that's the principle behind infanticide in animals. --Tango (talk) 20:53, 21 February 2009 (UTC)


 * I recall reading that a relatively large percentage of giant panda mothers either don't know how to care for their young or aren't interested in doing so. I'm not sure if this only applies to those born in captivity, but it's a challenge to increasing their numbers. StuRat (talk) 12:31, 22 February 2009 (UTC)


 * Are you asking about species that tend to eat their young, or specific animals that somehow don't have the nurturing instincts shared by the rest of their species? — DanielLC 17:22, 23 February 2009 (UTC)

Burns
Why is it exactly that the medical community (and, subsequently, the media) expresses burn injuries in terms of percentages? I have read the Wikipedia articles on Burn and on Total body surface area. But, they did not really address my question. When we read a newspaper report of a burn injury, it will invariably state something along the lines of "The victim suffered burns on 78% of his body" (or something like that). Why exactly is this important? Any insights? Thanks. (Joseph A. Spadaro (talk) 22:03, 21 February 2009 (UTC))


 * The medical community is probably, for the most part, more concerned with the degree of the burn. But a burn is essentially a wound, an opening in the skin through which infection can travel. So a larger percentage burn means a larger surface area that's open to infection, and a concomitantly greater burden on the immune system to defend. As the burn article notes, "Infection is a major complication of burns". The burn article, and the Servitt article linked from it, indicates that the burn affects the body's fluid regulation systems - bigger burn->greater disruption. 87.112.17.229 (talk) 22:57, 21 February 2009 (UTC)


 * The immune system can't the only one that's burdened either. I don't know specifics, but there must be other body systems that are hugely impacted by having to heal such a large amount of skin and other tissues. --Anonymous, edited 00:24 UTC, February 22, 2009.


 * The reason the percentage is reported is quite simple: prognosis. The larger the area, the less likely that the patient will survive. One formula, for example, where TBSA = total burn surface area is: percentage chance of survival = (100 - (age in years + TBSA)). So a 60 year old with a 30% TBSA has a 10% chance of survival, and a 20 year old with a 30% TBSA has a 50% chance of survival. A 25 years old with a 78% TBSA would by this calculation have a -3% chance of survival - that is, his death would be expected. Obviously these are estimates. To a certain extent, the prognosis will influence treatment by indicating who will be most likely to benefit from intensive specialized burn treatment at a dedicated burn center facility. - Nunh-huh 00:35, 22 February 2009 (UTC)
 * That formula says that a 60 year old person with no burns whatever has only a 40% chance of survival, so it seems pretty absurd. Survival for how long? 30 years? Who sits around making up such formulas? Are they based on empirical data or intuition? Edison (talk) 01:22, 22 February 2009 (UTC)
 * Obviously formulas for predicting the likelihood of surviving a burn are going to produce absurd results when applied to people without burns. The "survival" in question is survival of the acute burn episode - that is, recovery sufficient to eventually die of something else. Clearly the formulas are based on empiric data - no one would publish a formula based on intuition. For some people involved in using TBSA to predict survival, have a look at, or have a go with the editorial: . Medline searching will also return various papers. - Nunh-huh 01:41, 22 February 2009 (UTC)
 * The formula is clearly a first-order approximation of the real formula. It's only going to be accurate near whatever point it was approximated about (which will have been a significant burn area and a non-elderly person - exactly where they approximated, I have no way to know). --Tango (talk) 02:17, 22 February 2009 (UTC)
 * And a 110 year old person without burns will have a -10% chance of survival. Sounds pretty depressing to me. --Taraborn (talk) 14:50, 22 February 2009 (UTC)

Hmmmmmmmmmmm. Maybe I mis-spoke when I worded my original question. I agree with all of the above. And it makes sense that the more burn area (percentage), the more danger to the patient/victim. But, isn't this all of interest and concern to the doctors and medical treatment staff only? Why is this of concern to journalists and the news media (and their audiences)? When I watch or read the news, I never hear anything like: "The victim required 28 stitches" ... or ... "The victim required 7 pints of blood" (etc.). Those details are important to the medical treatment staff, but not important to the television or newspaper audience. So, why is the burn percentage treated differently? Yes, it's important to the doctors and treatment staff to know the burn percentage. But, why is it so important to the general news media audience that it is nearly always reported? That was really what my original question was getting at. Thanks. (Joseph A. Spadaro (talk) 02:42, 22 February 2009 (UTC))


 * The number of stitches is of only passing interest medically. Same for units of blood transfused (sometimes, but not consistently of major concern).  In contrast, burn area is always important when burn is the primary injury, it is mentioned every time clinicians present a burn patient to one another, and burn centers report it (along with survival rates) to the entities that fund them.  So, it's almost always known to the person being interviewed by media.  People being creatures of habit, they report it to the media, and the media pass it on.  --Scray (talk) 03:40, 22 February 2009 (UTC)


 * And since the area burned affects the probability of survival, it is of interest to the news media's audience. Well, maybe not you, but to some of the audience. --Anonymous, 06:53 UTC, February 22, 2009.


 * Also, even if the audience isn't aware of the relationship between the burn area and survivability, it's still pretty informative: "78%? Geez, that's a lot, that's bad." -- Captain Disdain (talk) 08:07, 22 February 2009 (UTC)


 * What the media want is to concisely quote a single, supposedly empirical, value which conveys degree of injury. They really want to say someone was burned 30% to death, or the car crash reduced their life to 25%. Of course you can't really reduce complex medical conditions and their prognoses to a single statistic, which is why it's nearly meaningless; it's just like a report of a fire being "3 alarm" or a report of the "bodycount" of a military operation. And I don't agree that news outlets don't use the stitches count as another false statistic:, , . or pints of blood transfused , , . It's the same for the number of bones broken (or in how many places a given bone was broken) during an incident. 87.112.17.229 (talk) 11:44, 22 February 2009 (UTC)


 * I still say the formula is extremely silly and could not be based on data. A 50 year old person with no burns, or burns over .0000000000001% of the body has only a 50 % survival rate? Utter nonsense. As for the percentage of body burned, it is not a literal measurement. There are tables stating what percent the legs, arms, back face, or hands are, and it is just added up. There is no literal measurement of square centimeters burned, by careful measurement of irregular burned areas, versus total square centimeters. Edison (talk) 03:18, 23 February 2009 (UTC)
 * That formula is simplistic. This guideline is more helpful. Axl  ¤  [Talk]  16:42, 23 February 2009 (UTC)
 * Here is the original study in the New England Journal. Alternatively, you could use this formula: logit = -7.37 + 0.05(age) - 0.15(year) + 0.11(% body-surface area) - 6.61 x 10-4(% body-surface area - mean % body-surface area)2 + 1.04 x 10-3(age - mean age)2 Axl  ¤  [Talk]  16:45, 23 February 2009 (UTC)
 * As I explained above, the formula is quite clearly a first-order approximation (you can tell because it's all linear and the true formula obviously can't be since it is bounded). If you try and apply a first-order approximation significantly away from the point it was approximated about, you will get nonsense. --Tango (talk) 16:52, 23 February 2009 (UTC)

Thank you to all for the input and feedback. This discussion was very helpful. Much appreciated. Thanks. (Joseph A. Spadaro (talk) 05:48, 2 March 2009 (UTC))