Wikipedia:Reference desk/Archives/Science/2007 April 9

= April 9 =

Can the octet rule be explained in terms of more fundamental behaviors of sub-atomic particles?
Can the octet rule be explained in terms of more fundamental behaviors of sub-atomic particles? --71.162.233.206 00:41, 9 April 2007 (UTC)
 * This sounds like homework to me! Pauli exclusion principle, no? [' Mαc Δαvιs '] ( How's my driving? ) ❖ 02:36, 9 April 2007 (UTC)


 * Actually I did look at the article on Pauli's exclusion principle but did not make any connection between the two. Still haven't figure out how PEP explains the octet rule. (And no, it's not homework — I don't have homework.) --71.162.233.206 03:18, 9 April 2007 (UTC)


 * My memory of quantum mechanics and such is pretty weak, but I believe it has to do in part with electron orbitals—one s and three p orbitals can hold eight electrons, and fully occupied orbitals are in general associated with increased stability. The reasons those orbitals exist arises from wavefunctions and quantum mechanics, I believe, but I cannot remember more. Perhaps someone more well-versed in this area could comment (and improve the article)! — Knowledge Seeker দ 03:29, 9 April 2007 (UTC)


 * Take a look at Atomic orbital. Here's my explanation:


 * Every shell is numbered by the number n. For every n, there are as many subshells as there are numbers between 0 and n-1.  So for example the first shell, n=1, has 1 subshell numbered l=0 (l represents the subshell number).  For n=2, there are two subshells, numbered l=0 and l=1.  The electrons inside each subshell all have a magnetic quantum number; this describes the shape of the electron's orbit.  All numbers from -l to l could be taken as values.  This gives 1 unique orbit to the first shell, 4 to the second, and 9 to the third.  But because electrons also have one additional property, called the spin, that can either be positive or negative, the total number of electrons that can be held is 2 for the first shell, 8 for the second, and 18 for the third.


 * Although the 3rd shell has 3 subshells, the 4th has 4, etc., in the outermost electron shell only the bottom two subshells are used. This is because an electron in an outer subshell will have more energy than one in an inner subshell, and atoms always try to have the lowest possible energy. Subshells beyond the second one will only be used if they're not in the outermost shell (remember that electrons in the outermost shell have a lot of energy, too).


 * So the outermost shell can have 2 used subshells, with the first one containing 1 possible value of the magnetic quantum number and the second one containing 3 possible values. With 4 different orbitals and each electron having either a positive or negative spin, there can be a maximum of 8 electrons with no two electrons having the same properties (if they did, they would be the same particle).  Obviously there can't be any more chemical reactions with a full shell.


 * I hope this helps, but feel free to point out any errors or make my explanation clearer; I'm far from being an expert! --Bowlhover 05:03, 9 April 2007 (UTC)

Artichokes polish aluminum?
I was just cleaning up after dinner, and I noticed that that aluminum lid for our cook pot was bright shiny and silvery. The pot is fairly old and is usually a dull gray color. We had boiled artichoke in it tonight and as usual, the inside of the pot is stained dark. I did add salt to the water that we boiled with which is different than usual. So what would it be about the combination of Salt, steam, and essence of artichoke that would polish the pot lid so bright? -Czmtzc 01:25, 9 April 2007 (UTC)


 * Well, the description definitely suggests there might've been some electrochemistry going on, but I can't really say off the top of my head exactly what. The presence of the steam, possibly including spray carried up from the surface of the boiling water, rather complicates things, too.  I doubt the artichokes had much effect, except maybe to adjust the pH of the water, although I guess it could be remotely possible that some kind of chelation effect might've played a role.  All this is really just wild guessing, though, and could be completely off base.  Some questions that might help solve this would be whether the pot is also aluminum like the lid, and whether the pot and lid are normally in direct electrical contact.  —Ilmari Karonen (talk) 17:16, 9 April 2007 (UTC)


 * Yes, the pot and lid are both aluminum and were in direct contact. The stove uses an electric coil for heating.  According to Globe_artichoke acids are produced and the pot should be uncovered in order to prevent the artichoke from turning brown. - Czmtzc 18:22, 9 April 2007 (UTC)


 * Hmm. The article doesn't cite any references for the claim about the acids, though.   Indeed, I found several sources recommending the addition of acids (usually vinegar or lemon juice) to the cooking water to prevent discoloration of the artichoke.  Anyway, I still have no clue on the specifics, but it does sound like the salty water and steam might have produced some kind of a concentration cell.  In principle, all it would take is something to reduce the electrode potential on the submerged part of the pot, making it anodic and the exposed part and the lid correspondingly cathodic.  I did find a note about chloride ions, as found in salt, accelerating the corrosion of aluminum, but it's not clear to me if this would be at all significant at the conditions normally found in a cooking pot.  (How much salt did you add, anyway?)  Of course, I could still be barking up the completely wrong tree here...  —Ilmari Karonen (talk) 01:41, 10 April 2007 (UTC)


 * I added about a tablespoon to about a gallon and a half of water. Maybe 2 g NaCl to 6 l H2O.-Czmtzc 02:48, 10 April 2007 (UTC)

Easter osmosis ?
I have a chemistry/biology question related to my Easter dinner (do I have you hooked yet ?). One dish was sliced ham (precooked and injected with salt brine) heated with canned yams, canned pineapple rings, and some brown sugar. As always, it's quite good during Easter, but something bad happens to the leftovers. The ham slices left floating in the yam/pineapple juice seem to lose their water content (but retain all their salt) and become shriveled up, almost like bacon. I'm looking for an explanation of what's happening here. I would have expected, that since the ham is much saltier than the yam/pineapple juice, the ham would have absorbed water, not given off water. Perhaps the higher sugar content in the juice is able to suck more water out of the ham than the salt sucks in ? StuRat 03:53, 9 April 2007 (UTC)


 * I don't know exactly why it became like that but fresh pineapples are very good meat tenderisers because they contain some enzyme or something, so maybe you have some half digested meat floating around? --antilivedT 04:42, 9 April 2007 (UTC)


 * It's actually the reverse, it becomes tougher, like leather. StuRat 15:25, 11 April 2007 (UTC)

Earth Re-Entry
Is there anyway to re-enter Earths atmosphere without heating up, for example could you inflate a large ballon in space then slowly re-enter or maybe slow yourself down with engines? This reminds me of SpaceShipOne and how it re-enters could the same process be used for an orbital craft? —The preceding unsigned comment was added by 67.127.97.132 (talk) 04:47, 9 April 2007 (UTC). 67.127.97.132 04:48, 9 April 2007 (UTC)


 * The problem is that in the uppermost layers of the atmosphere, there is very little air resistance - so parachutes, wings and balloons won't have much effect in slowing you down. By the time you reach layers where there is significant resistance, you're falling so fast that you get into all of the heating/burning up problems.  SpaceShip One didn't get very high - nowhere near orbital altitudes.  So it had less far to fall - less time to build up speed - so when it did re-enter the denser parts of the atmosphere, it was going a lot slower than (say) the Shuttle does.  You could certainly slow yourself down using engines - but the amount of fuel you'd need to slow down would be about the same as it took to get you up there in the first place.  When you see the size of the fuel tanks and boosters that the shuttle needs to get up there - and imagine needing about that much to get back down again...then imagine the amount of extra fuel you'd need on launch to get the re-entry fuel up there as well as the spacecraft - you can see that it rapidly gets out of hand.  Heat tiles and the older 'ablative' heat shields are a cheap and (relatively) easy way to do the job. SteveBaker 05:00, 9 April 2007 (UTC)


 * I agree with most of that response, but not that the amount of fuel would be equal. This is because air resistance is hurting when a rocket is trying to gain speed during launch but actually helps when trying to reduce speed for landing.  Perhaps a lower thrust mechanism, like an ion engine, could therefore be used to lower the ship to the surface at a safe speed. StuRat 06:17, 9 April 2007 (UTC)


 * Even if aerodynamic heating were not a factor during atmospheric reentry, the thermosphere is about 2,000°C (3,600°F). − Twas Now ( talk • contribs • e-mail ) 07:06, 9 April 2007 (UTC)


 * Well, yes, but the air is so thin there that very little heat would be transferred to a descending rocket. StuRat 08:14, 9 April 2007 (UTC)


 * Yes, and the International Space Station has orbited in the thermosphere for years without getting significantly heated, as the main heat transfer mechanism is radiation. You might be interested in project ARCHIMEDES by the German Mars society. They are planning to enter Mars' atmosphere by balloon in 2010. Icek 12:43, 9 April 2007 (UTC)

An object which had a large surface area relative to its mass would not heat up as much as did the Space Shuttle or the Apollo capsule from atmospheric friction. This is why when the most recent Space Shuttle disaster occurred and it broke up, nylon bags with computer equipment inside, a videocamera with a tape of the early reentry, and plastic containers with worms from biology experiments landed intact. MOOSE was an early project to allow an astronaut to reenter with only a shield-like disk, a little expandable foam and a space suit as protection: the kilograms per meter of surface area would have been less than for a normal spacecraft reentering. At 30,000 feet he would have opened a chute. Edison 14:11, 9 April 2007 (UTC)

Thank You for all your answers.

Wirenetting allowing blackbirds, not magpies
Every year, a couple of blackbirds builds a nest by my house. And every year, their young/eggs are eaten by magpies. Although that is the course of nature, I would like to find a way to shield their nests from the magpies. I am thinking about some kind of wire-netting. Do you think this would be feasible? How large should the holes be to allow blackbirds, and not magpies?

Thanks in advance

Søren 83.73.238.25 07:06, 9 April 2007 (UTC)


 * I don't think there's much you can do, unless you discourage the birds from nesting there so that they stand a chance of finding somewhere safer. Magpies are not much bigger than blackbirds and there is a real danger of both becoming caught in any netting. Access through a screen with a hole or holes would be safer, but blackbirds prefer an open nest, so the screen could only be erected once they have laid their eggs, and it might put them off rearing their young. Perhaps a birding organisation such as the RSPB would have a better idea.--Shantavira 08:01, 10 April 2007 (UTC)

Protein digestion
Can protein form a white substance when becoming digested in the stomach, looking like the white of a cooked egg yolk? Thank you for your help

CorinneQ 07:21, 9 April 2007 (UTC)Corinne Quinones


 * I would guess yes, as many forms of protein start out looking like that. Besides ovalbumin, there's also chicken and many other sources of protein. StuRat 08:08, 9 April 2007 (UTC)

Thank you very much for your help, I really appreciate you taking the time to answer me StuRat =)

CorinneQ 08:12, 9 April 2007 (UTC)Corinne Quinones


 * You're quite welcome. StuRat 08:15, 9 April 2007 (UTC)

Wake imaging
I am looking for OPEN source material on the subject of " Wake imaging "

That is, the detection of surface or sub-surface craft using Synthetic Aperture Radar.

Rather than open a new subject page, I would be grateful if you could let me know where in Wiki I might find any related data SPECIFICALLY on wake imaging

(I have reviewed the material held on Synthetic Aperture Radar and related discussion on Doppler beam sharpening etc.)

Thanks

Goatman81 09:40, 9 April 2007 (UTC)

I am looking for OPEN source material on the subject of " Wake imaging "

That is, the detection of surface or sub-surface craft using Synthetic Aperture Radar.

The wake of a ship or submarine is the long lasting disturbance in the water caused by its passing.

Rather than open a new subject page, I would be grateful if you could let me know where in Wiki I might find any related data SPECIFICALLY on wake imaging

(I have reviewed the material held on Synthetic Aperture Radar and related discussion on Doppler beam sharpening etc.)

Thanks Goatman81 09:50, 9 April 2007 (UTC)

I saw a picture, probably over ten years ago, in some general publication, which showed an image (probably radar from space) showing the wake of a ship extending many miles and how easily it was spotted these days, noting that there would not be another secret crossing of the ocean like the Japanese fleet which attacked Pearl Harbor, or the U.S. fleet which invaded North Africa in World War 2. Even the search for the Bismarck would be a snap with modern technology replacing the high altitude patrol craft of WW2 which combed the ocean looking for convoys or battle fleets. On further research it was from the Space Shuttle Endeavor synthetic aperture radar experiment in 1994. Google ship wake image space and you will find several references. See. These references are "open source" in the sense that they are not classified, but many require a subscription. Get access to the library of a college and they might be able to give you free access. Edison 13:28, 10 April 2007 (UTC)

Light pens/light guns
Any idea how does a light pen work?Any what about the GUns that used to come with the video games that can detect the images or moving image that we shoot on the TV??210.212.194.209


 * Check out light pen--Shantavira 10:46, 9 April 2007 (UTC)


 * The old NES light gun (NES Zapper) used an interesting method. When you pulled the trigger the screen would be momentarily blanked and white boxes indicating the hit zone for targets would be drawn.  The sensing mechanism was a pretty basic photodiode behind some cheap optics in the back of the gun. -- mattb


 * Dusting off some twenty-year-old memory cells here: I seem to remember that you could cheat by pointing the gun at a light bulb and pulling the trigger. Your description of how the gun worked would explain that. --TotoBaggins 15:19, 9 April 2007 (UTC)


 * You could also change the optics to make the targets a lot bigger... Like by holding a magnifying glass at the end.  -- mattb


 * That all depends on how stupid the software is/was. As our article describes, real light pens were timing-based devices and identified to the computer the coordinates of the region of the screen that they were pointed at (or, for vector graphics systems, the particular vector object they were pointed at). They'd never have been fooled by stupid light bulb/lens tricks. See Lunar Lander for an example of a light pen in action on a vector graphics system.


 * Atlant 16:28, 9 April 2007 (UTC)

Motion Sensors
How does a motion sensor for games, work? if i start with the controller upside down it knows! is is mercury switches or something else. Also how can games consoles tell were you are pointing light guns, wii nunchuks etc. on the tv? —The preceding unsigned comment was added by 84.13.132.232 (talk) 10:31, 9 April 2007 (UTC).


 * Check out motion sensor.--Shantavira 10:47, 9 April 2007 (UTC)


 * It depends! There are many ways to realize motion sensors.  A lot of modern applications use MEMS accelerometers and gyroscopes.  The Wii controllers you refer to both use monolithically integrated MEMS accelerometer chips and a CMOS SoC image sensor:,  .  You could conceivably use some kind of mercury switch scheme, but on top of being bulky, fragile, inaccurate, and unable to really measure acceleration, it might not be a fantastic idea to put a toxic heavy metal into children's toys, especially ones that are going to be thrown around (I'm pretty sure nobody uses mercury switches in thermostats anymore, either). -- mattb


 * If you are asking about the Wii, the controller does two different things. Firstly, it uses a very low resolution infrared camera to look at two infrared LED's in the little gizmo you put on top of the TV screen.  This tells it in absolute terms where it is pointing relative to the TV screen - which is used for 'aiming' games and to move the pointer around when selecting from menus and such.  You can prove this by replacing the light bar with two lighted candles about a foot apart!  The other sensor is a set of accellerometers that measure the accelleration of the remote.  The nunchuck controller only has the accellerometers - no camera.  The accellerometers measure how the remote is moving or rotating - but it doesn't know exactly where the controller is positioned - the actual games within Wii sports work just as well with the 'light bar' disconnected - so we know they only use the accellerometers.  Different games use that data in different ways so it's hard to explain in detail how they figure out where the controller is.  Some of them can't tell whether it's upside down or not.
 * Light guns work differently. The gun has a light sensor at the end of a long, narrow tube that sees the light from the TV screen.  The game console gets a signal whenever the gun sees light.  By measuring the amount of time from when the TV screen starts it's raster scan to when the gun sees a blip of light from the screen, the game can figure out where on the screen the gun is aiming.  It's hard for the gun to see light coming from black areas of the screen - and you'll notice that games that use light guns don't generally draw large areas of dark pixels. SteveBaker 23:09, 9 April 2007 (UTC)

Name that celestial body
So, I've seen a star/planet in the sky a few times over the past month, and I was hoping someone could tell me what it is. I'm in Salt Lake City, Utah, and the object was almost directly due south at about 5 a.m. MDT (23 UTC), and not too far off the horizon, probably about 30 degrees or so. It had a reddish glow/tint, leading me to speculate that perhaps it was Mars, but really that's a pretty baseless guess. I've never been very good at reading various star charts, so I'd appreciate some help. Of course, if you'd also like to "teach a man to fish..." as the saying goes, then feel free to provide me a link and tutelage either on this page or my talk page. Cheers! Eric (EWS23) 12:14, 9 April 2007 (UTC)


 * It was not Mars, but the much brighter Jupiter. See http://www.fourmilab.ch/yoursky/ for an online starchart program, enter your time and location (5 a.m. is 11 UTC), and look south.  The symbol that looks like "4" is Jupiter, and at magnitude -2 it's much brighter than any star.


 * Mars should also be visible from your location, but you'll have to go to an open field and scan the eastern horizon just before sunrise to see it. --Bowlhover 12:46, 9 April 2007 (UTC)


 * Apologies for the UTC error...that's what I get for being up so early in the morning. Eric  (EWS23) 13:27, 9 April 2007 (UTC)
 * Stellarium is the program I use whenever I have a question like this one. It is free and very easy to set up. Once you have it up and running, you can see exactly what the sky looks like from where you are in the world and all the stars, planets and constellations are labelled. Graphically it is the best program of its kind that I have seen, the view is very clear and easy to use. Vespine 00:10, 10 April 2007 (UTC)

Dyssomnia vs Insomnia
What is the difference between dyssomnia and insomnia? Thanks a whole bunch!!!!58.153.97.57 14:38, 9 April 2007 (UTC)
 * Try reading our encylopedia articles on dyssomnia and insomnia; you can use the search box on the left side at the top of the page next time. [' Mαc Δαvιs '] ( How's my driving? ) ❖ 14:52, 9 April 2007 (UTC)
 * I agree - read the articles - but briefly, a dissomnia is any kind of sleep disorder - which could be too much sleeping, too little sleeping, inability to control when you sleep...all sorts of things. Insomnia is specifically a problem with getting to sleep or staying asleep. So insomnia is a kind of dissomnia. A specific case of dissomnia might be insomnia but it might be something else. SteveBaker 22:56, 9 April 2007 (UTC)

Electric Cas vs not driving
Hi, I dont drive but recently find myself lusting after electric cars. I was wondering, given that normally i take the bus to work (i'm supposed to cycle but everytime i get a puncture it takes me about a month to get round to fixing it), what are the pros and cons environmentally speaking? Some of these cars can apparently do the equivalent of 300 mpg which can't be far off what one person "does" in a bus. Also, is there an argument that if you buy an electric car (which in the UK are extrememly rare) you're both rasing awareness (people see you driving) and help lower the cost of future electric cars, which are obviously both environmental good deeds? So what are our thoughts people - bus vs electric car? I'd love to hear your comments....87.194.21.177 14:58, 9 April 2007 (UTC)


 * See our article on fuel efficiency in transportation for some numbers. The sort of comparison that you're looking for is probably on the basis of passenger-miles per gallon.  Depending the location, age, fuel type, and maintenance, a full-sized city bus in city traffic typically gets an ugly-looking 6 to 10 miles per gallon.  However, the same bus holds fifty or sixty passengers.  So the same bus, one-third full, positively sips fuel compared to most other vehicles on the road: about a 150 passenger-miles per gallon.  Fully loaded (or more, in the morning crush), each gallon of fuel equates to more than four hundred passenger-miles.  TenOfAllTrades(talk) 17:07, 9 April 2007 (UTC)


 * The bus runs whether or not you are riding it, so from a fuel standpoint your ride to work is free. anonymous6494 18:06, 9 April 2007 (UTC)


 * True, if just one person switches to an electric car, but if thousands do they may cut back on bus lines. Unfortunately, this makes bus service less convenient, causing some former riders to buy old gas guzzler cars.  Also, you should consider the entire environmental cost of an electric car, which isn't just the fuel but also the energy used and pollution resulting from production and the inevitable pollution when those old batteries, and eventually the entire car, end up at the junk yard.  When you said 300 miles per gallon, are you talking about hybrids ?  A fully electric car doesn't burn any gasoline at all, so gets an infinite number of miles per gallon, although that would be an odd way to put it.  Many people also neglect to consider the pollution created when the electricity is generated which is later used to run the car.  If that electricity is generated in a well-run, modern nuclear power plant, the environmental impact may be slight, while an old, inefficient coal-burning plant may create far more pollution per mile than gasoline does.  Keeping all that in mind, I find it unlikely that getting an electric car is better for the planet than riding the bus. StuRat 18:49, 9 April 2007 (UTC)

HI its me again. THe figure thats quoted by smart's new "ev" is that it does the equivalent of 300mpg, judging from the sentence that preceeds it, that seems to be on a cost basis i.e if you charge it at peak times, its costs £0.85/mile - equivalent to 300mpg. I'm not sure the "bus is going to run anyway" is viable thought is it? i mean, people use that just justification for short haul flying- thus implying that their not responsible for the pollution that their "seat" causes. Also, surely the environmental cost of building a bus is fairly substantial? but yes, it does seem that i'm bus bound... boo. (cheers for the figures though, i think thats what i was really asking)87.194.21.177 19:15, 9 April 2007 (UTC)


 * I'll note that flying may not be as fuel-inefficient as you might think. In the U.S., air travel averaged a fuel consumption of 50.1 revenue passenger-miles per gallon in the third quarter of 2006 ; this puts them ahead of most cars driven by a single occupant, and ahead of many cars driven with two passengers.  Most aircraft also haul a significant amount of freight in addition to their passenger load.  TenOfAllTrades(talk) 19:30, 9 April 2007 (UTC)


 * That's true for long flights, but for short flights you must also consider the substantial fuel used to get to and from the airport (this should be considered for long flights, too, but it's a less significant factor there). StuRat 22:04, 9 April 2007 (UTC)

Have you considered an electric bike? The flat tire problem is easily handled by a no-more-flats foam inner tube or one that is filled with leak sealant gel. Another trick is to drill another hole for a valve stem one quarter turn away from the original valve and then insert a second tube between the first tube and spoke liner leaving it flat until you get a puncture then inflating it when the first goes flat. You can double the range if you can recharge at work and in some places the bus line offers bicycle racks which include electric bikes in case it is raining. Except for improper battery disposal an electric bikes is very environmentally friendly and can also greatly improve your mobility over human power alone. Nebraska bob 05:28, 11 April 2007 (UTC)

A CTC article on punctures showed that an option that was cheap in the long run and basically eliminated punctures is to use tyres like the Schwalbe Marathon Plus. They've got a 6mm-thick layer between the road and the inner tube that can stop drawing pins, but they're apparently ok to ride on too. So much easier around town than a car ^^ Brammers 20:29, 12 April 2007 (UTC)

Chicken or the egg?
I know the chicken or the egg dilemma is usually a philosophical problem, but from a scientific perspective which one actually came first? Heycos 15:09, 9 April 2007 (UTC)


 * Various creatures have been laying eggs — even bird eggs — long before domestic chickens, or even their immediate wild ancestors, emerged, so I'd say it's a pretty clear-cut case. —Ilmari Karonen (talk) 15:18, 9 April 2007 (UTC)


 * Fair enough, but from an evolutionary biology perspective do we know whether it was the "chicken" egg or the "chicken" which first appeared? Heycos 16:19, 9 April 2007 (UTC)


 * Evolution is mostly a gradual process, so it may not make much sense to define a specific the point at which a "chicken" (for whatever definition of the word) emerged with such precision. However, if we did single out a specific gene mutation as marking the emergence of the modern chicken, then presumably the mutation would have to have occurred in the germ line, since mutations occurring elsewhere don't get passed on to subsequent generations. Conversely, a mutation in the germ line doesn't really get expressed properly until a sex cell carrying the mutation undergoes fertilization to produce, in the case of birds, first an egg, and then a mature individual. So my answer would still be the same: the egg came first. —Ilmari Karonen (talk) 16:51, 9 April 2007 (UTC)


 * The problem, I think, is that people tend to think of evolution as something which builds up on one species over time, and then all of a sudden a "more modern" species forms. This is what Richard Dawkins calls "the tyranny of the discontinuous mind" in "The Salamander's Tale" of his wonderful book The Ancestor's Tale.  Submitting to this tyranny, we begin with a "pre-chicken", which undergoes some mutations over time—but still remains a prechicken—until one of these prechickens lays an egg, and suddenly we have the chicken!  I think everyone but the most insane severe fundamentalist would agree that the pre-chicken parents of the first chicken are more closely related to that first chicken than they are to every earlier pre-chicken (except their own parents), and the first chicken is more closely related to its pre-chicken parents than to any subsequent chicken (except its own children).  There is no precise point in time where two parents are of one species, and their offspring are of another species.  Ever.  A species is not a discrete unit, but a continuum of genetic similarity as anagenesis or cladogenesis occur.  See ring species and speciation.  − Twas Now ( talk • contribs • e-mail ) 17:22, 9 April 2007 (UTC)


 * I agree that the chicken egg came first. Whatever arbitrary definition for a chicken is used (like having 99.9% of genes in common with a selected modern chicken, for example) will lead to that conclusion, because the egg is genetically identical to the resulting offspring, while not necessarily genetically identical to the parents. StuRat 18:36, 9 April 2007 (UTC)


 * If that was the case, then the chicken and the prechicken would be two different species, and would not be able to interbreed. I find that absurd. − Twas Now ( talk • contribs • e-mail ) 21:27, 10 April 2007 (UTC)


 * Yes, but you also reach an absurd conclusion if you say that every generation is of the same species as the parents. Then you must conclude that, while A=B, B=C, C=D, ..., and Y=Z; A≠Z.  At some point you must just arbitrarily decide that this is now to be considered a different species.  This is a problem that archeologists must often deal with, when they find various "missing link" fossils. StuRat 03:21, 11 April 2007 (UTC)


 * That is the only alternative conclusion you can think of? I might say that A and B belong to set X, while B and C belong to set Y — there is an intersection, but not an union. − Twas Now ( talk • contribs • e-mail ) 15:13, 11 April 2007 (UTC)


 * Neither or both, and don't let anyone else tell you otherwise. − Twas Now ( talk • contribs • e-mail ) 16:11, 9 April 2007 (UTC)


 * It all depends on how you define "(chicken) egg". What actually makes an egg a chicken egg? If you define "chicken egg" to be a) an object that has been laid by a chicken, then chicken came first. If you define it to be b) an object from where a chicken hatches, then egg came first. You can do the same kind of reasoning with "chicken". --Nitku 17:52, 9 April 2007 (UTC)


 * Doing a search on YouTube, yields two videos with sciencey-conversational analyzations: and . [' Mαc Δαvιs '] ( How's my driving? ) ❖ 19:55, 9 April 2007 (UTC)


 * StuRat has it right. Whatever the egg genetically is so will be the adult that came from the egg. On the other hand the egg may be genetically different from the chicken (or other egg layer) that laid it. So if you go back in time to the first chicken egg that was laid then the organisim that laid it was not a chicken but a pre-chicken. The pre-chicken then laid a genetically different egg from itself that we call a chicken today and it came before the chicken that was in it which later hatched to become the first chicken. ....zzzzz Nebraska bob 19:12, 10 April 2007 (UTC)

Geomagnetic reversal
Would a pole reversal have any effect on magnetic storage devices? --Cody.Pope 15:52, 9 April 2007 (UTC)


 * You could test this by yourself: just turn you computer around 180° and see if the operation of the hard disk is affected. (Seriously, field reversals appear to be associated with a weakening of the magnetic field, which might leave the Earth more exposed to stuff like solar flares that might disrupt long distance communications and power distribution (see geomagnetic storm).  However, I don't think isolated storage devices on the surface are likely to be significantly affected.)  —Ilmari Karonen (talk) 16:24, 9 April 2007 (UTC)


 * OH MY GOD!!! YOU BASTARD! ALL MY FILES ARE GONE! [' Mαc Δαvιs '] ( How's my driving? ) ❖ 17:04, 9 April 2007 (UTC)
 * SteveBaker 22:43, 9 April 2007 (UTC) .enif tsuj gnikrow si yM !drieW
 * Sure, but it's a period of increase geomagnetic instability. Not just one reversal, but many over a period of time.  But in general I see your point. --Cody.Pope 16:27, 9 April 2007 (UTC)

Agreed, the Earth's magnetic field is so much weaker than the field associated with magnetic storage devices that it wouldn't directly affect such a device. StuRat 18:31, 9 April 2007 (UTC)


 * More to the point, when it's in use, your disk is spinning at around 10,000 revolutions per minute. From it's point of view, the earth's magnetic field reverses about 300 times each second! SteveBaker 22:47, 9 April 2007 (UTC)


 * What you'd really have to worry about is anything that relies on a compass. Someguy1221 00:25, 11 April 2007 (UTC)

Identifying an Ethiopian goat antelope
Can anyone identify the animal in this picture Image:Ethiopian Highlands 01.jpg? I am quite certain it is a member of the Caprinae subfamily, and would tentatively narrow it down to the genus Capra. I checked the Flickr page from which this image was taken, the animals listed at Category:Fauna of Ethiopia, and most of the subfamilies of Bovidae (even coming across this awesome animal), but alas! to no avail. − Twas Now ( talk • contribs • e-mail ) 16:02, 9 April 2007 (UTC)


 * Those are both incredible animals. Wow. Nimur 17:53, 11 April 2007 (UTC)


 * Yes. The reason I want to know is simply to see if it would make a good addition to that animal's article. − Twas Now ( talk • contribs • e-mail ) 05:16, 12 April 2007 (UTC)

Arthritic cat
My cat is almost 18 years old now, and he seems to be rather arthritic, though otherwise perfectly healthy and active. Are there medicines for cat arthritis? Corvus cornix 18:32, 9 April 2007 (UTC)


 * You'd be best to consult your veterinarian for advice, but yes&mdash;there are a number of treatments for osteoarthritis in pets: . Many therapies and drugs are similar or identical to treatments used for humans. TenOfAllTrades(talk) 19:35, 9 April 2007 (UTC)
 * Thanks. I wanted to know if there were any treatments before I took him in to the vet.  Corvus cornix 21:36, 9 April 2007 (UTC)


 * I believe vets sometimes give cats a very very small dose of aspirin, but don't give it acetaminaphin (Tylenol), because a small amount of that will kill a cat. Even a small amount of aspirin can kill a cat, so be caseful about that too. --Wirbelwind ヴィルヴェルヴィント (talk) 04:56, 10 April 2007 (UTC)

Nuclear fuel rod disposal
Why can't we load the fuel rods into a rocket and send it to the sun?? It would seem that the incineration would certainly be complete and there would be no excess radioactivity after the burn. —The preceding unsigned comment was added by Baron196 (talk • contribs) 19:29, 9 April 2007 (UTC).


 * Imagine what would happen if a rocket containing that payload were to explode in the atmosphere. -- mattb


 * The two chief objections boil down to cost and risk. It is currently very expensive to launch material into space; the price to loft a kilogram of payload to geosynchronous orbit is about twenty thousand dollars; to the sun would be even more. Lofting tons of waste would be an expensive proposition.


 * Perhaps more difficult to overcome are the concerns about safety. The catastrophic failure of a launch vehicle resulting in an explosion or crash has the potential to spread dangerous radioactive waste over a large area.  Appropriately shielding the waste and packaging it to survive such an accident would add greatly to its weight, increasing the costs of launch.  TenOfAllTrades(talk)

19:43, 9 April 2007 (UTC)


 * It is probably more economical to recycle the fuel rods. After you let them cool down you can reprocess them into plutonium and use them again. However, it is probably more economical than that to just throw them in the ground. [' Mαc Δαvιs '] ( How's my driving? ) ❖ 19:49, 9 April 2007 (UTC)


 * Nuclear generating plants must already solve the problem of radiation containment. So, there's really little additional cost or risk to having spent rods sitting in storage in these places.  If such a place leaks, we've got trouble with or without some extra spent fuel being stored there.  Friday (talk) 19:53, 9 April 2007 (UTC)


 * There are a few reasons why moving nuclear waste to a central repository is better. One is security.  While it would be difficult for terrorists to get fuel rods out of an active nuclear reactor, it might be possible for them to steal them from a used fuel rod storage area and make a "dirty bomb" (or just bomb the area where the spent fuel rods are stored).  Another reason is that nuclear power plants only have a useful life of a few decades, while the spent fuel rods may remain radioactive for centuries.  Rather than keep guards on site for centuries, it makes more sense to move the waste to one site which can be extremely well protected.  However, the transportation of nuclear waste poses it's own risks.   StuRat 20:48, 9 April 2007 (UTC)


 * I am still not sure why people worry about terrorists stealing fuel rods from nuclear plants. What?, are they going to pick one up and walk away with it? Even without the security it would be touch to get to it, then how are you going to move it to where you want it? [' Mαc Δαvιs '] ( How's my driving? ) ❖ 21:14, 9 April 2007 (UTC)


 * They could transport them in a lead container. Then again, if they are on a suicide mission anyway, they may not care if they get a fatal dose of radiation.  The theft of spent fuel rods would be considerably easier if they have an "inside man", possibly one or more of the security guards. StuRat 21:54, 9 April 2007 (UTC)


 * I'd be much more worried about a large aircraft being crashed into the spent fuel pool. Not as much of a concern as it was at one time as we no longer store spent cores in that pool forever, but the spent fuel pool is generally not a very well-protected building!  --BenBurch 21:45, 9 April 2007 (UTC)


 * Solar disposal might be an option in the future, with advances in rocket thrust and reliability. At present it would take many launches of our largest boosters, and we occasionally see one fail and have to be blown up. Yucca Mountain is the intended location for U.S. nuclear waste to be stored until the radioactivity has decayed over a period of many thousands of years. Political factors and environmental objections have kept the transportation of spent fuel on hold, until at least 2017. Meanwhile utilities continue to store nuclear waste in pools or casks. Some of these are located near large cities and/or important sources of fresh water. In the worst case, they are stored at decomissioned nuke plants, with guards whose only duties are to watch the otherwise unmanned plant. The spent fuel could be reprocessed and used in a breeder reactor but that would involve plutonium. In the U.S. there are thousands of functional nuclear weapons, so the presence here of additional plutonium might not be as alarming as in countries which have not so far chosen to build nuclear weapons. Edison 03:01, 10 April 2007 (UTC)


 * So the bottom line is that aside from the cost, getting the spent rods to the sun would have no negative effects on the sun itself and we would not have to be concerned about theft, underground water contamination, or storage for hundreds of thousands of years. The earth is constantly changing and I doubt science can guarantee the stability     of Yucca Flats for the life of the rods. Our only concern is the reliability of the rockets used to get the material on track to the sun.Seems less expensive than storage. Catch up would be expensive,but after that "not so much"Baron196 20:35, 10 April 2007 (UTC)


 * New technology will likely give us a way to reprocess nuclear waste cheaply and safely at some point in the future, so we won't need to store it permanently. StuRat 03:09, 11 April 2007 (UTC)

Measurements
Would someone knowledgeable please explain liquid measurements ending as follows:

mg ml mcg

The question is in regard to liquid vitamin B12. I am totally confused even after searching - Wikipedia and the internet in general.

Thank you, LM —The preceding unsigned comment was added by LiterateMuse (talk • contribs) 19:42, 9 April 2007 (UTC).


 * mg is a milligram (one-thouandth of a gram); ml (properly written mL) is a milliliter (one-thousandth of a litre; thirty mL is about one fluid ounce); mcg (also &mu;g) is a microgram (one-millionth of a gram). Presumably, the packing specifies the concentration of the vitamin in the liquid solution in units of mass (mg or &mu;g) per unit of volume (mL).  Given that information, you can convert a desired mass of vitamin B12 into an equivalent volume of B12 solution.  TenOfAllTrades(talk) 19:48, 9 April 2007 (UTC)


 * Minor nitpick: both ml and mL are correct for milliliters. When the SI was first established, l was the only symbol allowed for liters, but this was impractical for obvious reasons, and L was admitted as an alternative.  For the prefix "micro-" as in micrograms, only &mu; (Greek letter mu) is correct, making &mu;g.  In 1974 a standard was issued allowing "u" an alternative if the Greek letter was not available, but this was later withdrawn, apparently on the assumption that everyone now has computers that support that character; "mc" has never been correct in the SI, but as the original poster saw, some people use it anyway. --Anonymous, April 10, 2007, 04:40 (UTC).


 * A further warning. In the case of milligrams and micrograms you are on safe ground - but if you ever have medication or supplements measured in gram quantities - be aware that it is common practice in the USA to mark such things in 'grains' (1 grain = about 65 milligrams). Annoyingly (and lethally dangerously) the abbreviation for 'grain' is 'g' - same as the SI standard for 'gram'.  Even more ridiculously, the medical profession in the US decided to adopt 'gr' for 'gram' (in violation of the SI naming) in order to continue to use 'g' for 'grain'.  This kind of thing is deeply scarey!  However, since the grain is a pretty small unit as-is, there is no common usage of 'milligrains' or 'micrograins' - so mg and &mu;g are pretty much certain to refer to grams. SteveBaker 05:35, 10 April 2007 (UTC)


 * Good heavens! I was about to observe that the abbreviation for grains is "gr", so there's only confusion with grams if the incorrect symbol "gr" is used for grams. Are there really people who use "g"? Well, Russ Rowlett's web site on units of measure doesn't mention it, but I'm sure you didn't make it up. Talk about your maximal confusion. --Anon, April 11, 01:36 (UTC).

In medical contexts in the United States, even though "&mu;g" is the technically correct abbreviation, "mcg" is preferred for micrograms. Especially in handwritten orders and prescriptions, JCAHO rules require mcg (or "micrograms"); using "&mu;g" is not allowed over concerns that the &mu; could be mistaken for an "M" if written quickly (and therefore, potentially increasing the dose by one thousand). — Knowledge Seeker দ 05:45, 11 April 2007 (UTC)


 * Or by a trillion (If someone is rather picky about their prefixes)?.. I'm not sure how many drugs are administered in Mg though. That would be a fun capsule to swallow. Capuchin 10:45, 11 April 2007 (UTC)

Tarpan fact check
I find this edit somewhat suspicious, and both it and the article before it are contradicted by the IUCN, which makes reference to a Novak 1999 I have not been able to find. Could someone please help sort this out? --Tardis 20:42, 9 April 2007 (UTC)
 * "...it is known from authoritative sources that the last remaining tarpan mare was killed in 1876 on the Agaimany pod, in the region of the present Askaniya-Nova, or Chapli preserve.(Berg, L.S. (1950) Natural Regions of the U.S.S.R, p. 107)"
 * "They were hunted and exterminated, the last tarpan having been killed around 1860 in the steppe north of the Black Sea.(Dobzhansky, Theodosius (1955) Evolution, Genetics and Man, p. 197)"
 * Those are old sources, so i don't know how much faith to place in them. Also note that the redlist link states: "The last known wild individual died in Ukraine in 1879", which would not conflict w/ a later date for the last specimen.&mdash;eric 22:11, 9 April 2007 (UTC)

Terminal velocity of a droplet
Hi

I'm trying to find out what the terminal velocity of a 10uL droplet of water would be at ~1atm. Terminal velocity gives an equation to calculate it, but I don't know what the drag coefficient of this droplet would be. And I'd just be guessing on the cross sectional area. Does anyone have any insights to this, or an emprical measure of the terminal velocity of a 10uL drop of water?

Thanks for your help.

Aaadddaaammm 23:36, 9 April 2007 (UTC)


 * Conveniently, someone's done the measurements. The abstract is here, follow the link on that page to get to the PDF.  10 &mu;L of water weighs 10 mg, or  105  104 &mu;g.  Using their tables on the fourth page of the paper, they give a terminal velocity of 7.65 meters per second.  TenOfAllTrades(talk) 23:59, 9 April 2007 (UTC)
 * That should be 104 &mu;g (but the terminal velocity is correctly looked up). By inverting the formula the drag coefficient can be calculated, it is 0.5. Icek 00:16, 10 April 2007 (UTC)
 * Oop, you're right. Typo fixed. TenOfAllTrades(talk) 01:15, 10 April 2007 (UTC)
 * Thank you, that paper is very useful. But, now I'm not sure if the drop will be at terminal velocity - it's only fallen 3m - and they say that "the largest drops" (they go up to 100uL) take 12m to reach terminal velocity. Do you have any hints for calculating the velocity after falling only 3m? Aaadddaaammm 01:24, 10 April 2007 (UTC)
 * Technically, nothing ever reaches a theoretical terminal velocity. An object approaches terminal velocity, but it never quite gets there. To figure out how fast it's going at any one time, you need to do some physics. Jolb 04:44, 10 April 2007 (UTC)
 * Got any hints on what kind of physics I should be doing? Aaadddaaammm 08:02, 10 April 2007 (UTC)
 * Try differential equations (not really physics, but a mathematical tool useful in its context). Baccyak4H (Yak!) 15:55, 10 April 2007 (UTC)