Wikipedia:Reference desk/Archives/Science/2007 December 23

= December 23 =

Red spot on an Egg Yolk
What's the red spot on some egg yolks? I've heard this called a "blood spot," but I'm not sure it's really blood, nor would that seem to make any sense. Someguy1221 (talk) 00:51, 23 December 2007 (UTC)


 * An early-stage chicken embryo? On occasion, I've cracked open eggs and found embryos large enough to discern the developing features. Heh, my grandma boiled an egg last year and discovered a near-fully grown chicken foetus upon shelling it. --Kurt Shaped Box (talk) 01:00, 23 December 2007 (UTC)


 * It appears that the red spot is not an embryo, but rather from a blood-vessel bursting on the surface of the yolk during egg-production, and is a sign of freshness. . DuncanHill (talk) 01:05, 23 December 2007 (UTC)


 * Further info here.  —Preceding unsigned comment added by DuncanHill (talk • contribs) 01:06, 23 December 2007 (UTC)


 * Did your grandmother enjoy the Balut, Kurt Shaped Box? William Avery (talk) 10:33, 23 December 2007 (UTC)


 * Apparently, it smelled really, *really* bad (making half the house smell of death bad). I guess that it's an acquired taste... ;) --Kurt Shaped Box (talk) 00:43, 24 December 2007 (UTC)


 * Apparently, it used to be that if you were Jewish and keeping Kosher you could not eat an egg with a red spot. In fact, you were supposed to break your eggs into a separate glass and examine them before adding them to a recipe because one bad egg could make the whole recipe not-Kosher. But I guess things have changed. Thanks factory farming! I guess if you are Jewish and prefer organic eggs you still have to be on the lookout?  S a u d a d e 7  14:30, 29 December 2007 (UTC)
 * Your source goes into some detail and is interesting. But note that it says Therefore, the requirement to check each egg remains in effect, as does the requirement to dispose of eggs containing actual blood spots. So a careful person is required to check every egg, even if it is known to be commercial and hence unfertilized; and at the same time, if the person eating (not cooking) the eggs knows they were commercial, it is permitted to eat them even if he is unsure they were checked.  Crazy stuff. Rpresser (talk) 19:09, 31 December 2007 (UTC)

Airplane safety
If impact and fire are the two major cause of death in a plane crash, why plane maker doesn't build a plane with large cushion and heat insulator that cover the cabin? Are they doing enough for the safety of passengers? roscoe_x (talk) 00:58, 23 December 2007 (UTC)


 * A lot that doesn't go into planes is due to weight considerations. Planes are fairly light for their volume, in fact. Good heat insulation to cover the entire cabin would be pretty heavy, I'd imagine, and a large cushion would be quite unaerodynamic. Further, a large cushion wouldn't help at all if the plane is plumetting toward the earth at full speed. And if you're willing to wait for it, I'm sure SteveBaker will give a response that will dwarf mine in both substance and length.  Someguy1221 (talk) 01:02, 23 December 2007 (UTC)


 * The answer is of course money. If its to expensive, its not practical. Far more people die on the roads than in planes, but we don't increase car safety because its not practical. It could be done, but no one will pay $100,000 for a plane ticket.--Dacium (talk) 10:56, 23 December 2007 (UTC)


 * Well we do increase car safety - improved headlights, air-bags, impact bars, crumple zones things like that. As for planes...large cushions would do little to stop most impacts - though they could plausibly introduce airbags into seats/curtain airbags - injuries/deaths can occur due to damaged landings/emergency landings. Fire-wise they could skip heat-insulation and have some sort of sprinkler system - obviously it would need to be advanced enough not to just make the situation worse (e.g. water on electrical fires is a bad thing). As the above note, weight is a big issue - as is cost. The number of deaths in commercial aviation annually is very low as I understand it. ny156uk (talk) 11:13, 23 December 2007 (UTC)


 * Gah&mdash;sprinkler system on an airplane...too much weight! Water is heavy stuff.  Carrying a couple of tons of it around on the aircraft everywhere it flies...ugh.  'Dry' systems that use carbon dioxide or other gaseous fire suppressants would pose a risk of asphyxiation to passengers and crew.  Materials used in aircraft construction (particularly in the cabin) are required to be fire-retardant; they burn poorly anyway, if at all.  The insurmountable obstancle is that you're lifting off with a hundred tons of fuel on board, and if you break open some fuel tanks in a crash, then there's going to be fuel everywhere.  Putting out those sorts of fires takes professional firefighters with heavy equipment.  (Attempts have been made to make jet fuel safer in a crash; these attempts have not been successful.)  For what it's worth, many of the mechanical spaces on aircraft – the place where in-flight fires are likely to start – do contain fire bottles filled with fire suppressants.  In the event of fire, these bottles are triggered automatically or manually from the cockpit.  (I have also seen small, automated fire bottles built into airplane washroom waste receptacles, presumably to handle butts from careless, covert smokers.)
 * On the subject of crumple zones, the legs of airline seats are designed to collapse in a controlled manner to cushion the occupant in the event of a crash. Airbags, meanwhile, are unlikely to appear on commercial aircraft for a number of reasons.  First, it would mean putting rather a lot explosive material in the aircraft cabin&mdash;something that regulators are understandably twitchy about.  Second, there's no good, automated way to figure out when the airbags should go off in an airplane crash.  What if you're just on the first bounce?  Third, detonating all those airbags in a relatively airtight cabin could force oxygen out of the passenger compartment. TenOfAllTrades(talk) 15:43, 23 December 2007 (UTC)


 * In the event of a water crash with airbags, the bags could prevent passengers from being able to exit the aircraft Rfwoolf (talk) 17:29, 23 December 2007 (UTC)


 * Also, the accelerations a body is exposed during a crash are incredible. The report into the Swissair Flight 111 crash off Nova Scotia in 1998 suggested that the occupants were subjected to forces at least 350 g, which is well beyond the limits of human survivability. It is likely impossible to create a system that will protect occupants at loads like that while still being flyable or affordable. -- Flyguy649 talk 17:47, 23 December 2007 (UTC)

How much of a sphere can you see from one point?
Particulary to do with planets. I have always assumed it is 50% but I started thinking about it and I thought that it surely must be less, at some point the surface of the sphere will be paralel with your direction of vision. Is there some mathematical relationship that any one could write that would describe this? Cheers, Shniken1 (talk) 05:10, 23 December 2007 (UTC)
 * Let $$R$$ be the distance between the observer and the center of the sphere. Let $$r$$ be the radius of the sphere. Then the apex angle of the visible spherical cap is $$2\arccos\frac{r}{R}$$.$$2\arcsin\frac{r}{R}$$?? Using the formula found in the solid angle article, the solid angle of the cap is $$2\pi(1-\frac{r}{R})$$. Since the full solid angle of the sphere is $$4\pi$$, it means that the visible surface area is $$\frac{2\pi(1-r/R)}{4\pi}=\frac{R-r}{2R}$$. If $$R >> r$$, this ratio approaches $$1/2$$. - Sikon (talk) 07:15, 23 December 2007 (UTC)


 * All of it... provided it's completely lit with nothing obscured, and you use a few mirrors. Of course, that's assuming mirrors are not disallowed in your question.  Though, if we're talking planets, those giant mirrors can get expensive.  (Sorry, couldn't resist.) --  Hi  Ev  10:09, 23 December 2007 (UTC)
 * Giant mirrors? What are talking about? --Taraborn (talk) 13:35, 23 December 2007 (UTC)
 * He was making a joke about the scale of planets necessitating a giant mirror to see the sides out of view. - Woo ty   [ Woot? ]  [Spam! Spam! Wonderful spam! ] 13:51, 23 December 2007 (UTC)
 * Well, you could do it with smaller mirrors and use a telescope. It does raise an interesting side question though: how many mirrors would you need? (I'm guessing 2, but possibly 3?) -- SB_Johnny | talk  14:07, 23 December 2007 (UTC)
 * Oh. I didn't see the "All of it..." part... --Taraborn (talk) 14:43, 23 December 2007 (UTC)
 * If the mirror is large enough and you are far enough away from the sphere, you can do it with ONE mirror. The maximal case is where your viewpoint is at zero inches from surface of the objective sphere, and the reflecting mirror constitutes another sphere that completely encircles both you and the objective sphere.  The minimal case is where you are infinitely far away from the objective sphere, using an infinite magnification telescope, and the reflecting mirror is barely larger than the radius of the objective sphere.
 * If you take general relativity into account, you can do it with NO mirrors. Just have a black hole at the center of the sphere being viewed, and put the observer at the photon sphere.
 * The "conventional" solution would be to have three mirrors, each one convex in shape, placed at the axes of a tetrahedron with the viewer at the fourth axis, the objective at the center, and all four of you positioned at I think 2R from the center of the objective sphere (R = radius of objective sphere).
 * All this is back-of-the-envelope drawing, no math used :=) 19:05, 31 December 2007 (UTC)


 * When I'm out flying in my spaceship, I always measure the angle $$2\alpha$$ that the planet covers from my point of view and the distance $$h$$ to the surface. That way, I get the planet radius as
 * $$r=h\frac{\sin\alpha}{1-\sin\alpha}.$$
 * —Bromskloss (talk) 19:02, 23 December 2007 (UTC)
 * thats the craziest semiangle $$\alpha$$ I've ever seen! Furmanj (talk) 00:54, 24 December 2007 (UTC)


 * Really, how do you mean? —Bromskloss (talk) 12:20, 25 December 2007 (UTC)

Taste of vegetable oils
Why are some vegetable oils bitter in taste, and some not? Linseed or flax and hemp oils are bitter, while olive, canola {oil seed rape), walnut, and sunflower oil are not? Is there something in the oil that gives the bitter taste? Thanks 80.2.198.203 (talk) 15:29, 23 December 2007 (UTC)
 * Oils have very distinct tastes depending on what their made out of. Just because it's an oil, it doesn't mean they're all going to taste the same. An analogy could be made to different types of nut butters (i.e. peanut butter, cashew butter, almond butter, etc.) -- MacAddct &#xF8FF; 1984 (talk &#149; contribs) 16:14, 23 December 2007 (UTC)
 * The bitterness of Olive oil depends on the concentration of polyphenols such as Oleuropein. William Avery (talk) 17:02, 23 December 2007 (UTC)


 * And, of course, any oil that gets old and rancid tends to taste more-bitter than fresh oil.


 * Atlant (talk) 00:15, 24 December 2007 (UTC)

Coloured snow
Hi. What causes snow to turn different colours, say pink, green, or blue? Is it bacteria? Chemical reactions? Minerals? I heard that pink snow was called watermelon snow, I saw green snow on a probably-salted outdoor staircase, and I saw blue snow while building a snowball while the temperature was above freezing. What other colours are there, besides yellow caused by dog pee, and brown caused by road ploughed snow? Thanks. ~ A H  1 (TCU) 15:32, 23 December 2007 (UTC)
 * For watermelon snow, it's a type of algae that produces the color. I'm not sure about the other colors though, maybe it could turn blue if a colored brand of rock salt was laid down? Just don't eat the yellow snow! -- MacAddct &#xF8FF; 1984 (talk &#149; contribs) 16:10, 23 December 2007 (UTC)


 * Some commercially available ice-melting salts have dyes added to let you see where you've spread it. I've seen magenta, blue and green. -- Flyguy649 talk 21:26, 23 December 2007 (UTC)


 * With regard to light-blue snow, you might enjoy our article Color of water.


 * Atlant (talk) 00:14, 24 December 2007 (UTC)

telescope aperture required to view astronomical objects
Hi. Can you use the brightness in apparent magnitude of an object, the surface brightness at the site, the surface brightness of the actual night sky at the location of the observing site, the atmospheric conditions, how high an object is in the sky, the capability of the person's eyes, etc, to calculate the effective aperture of a telescope required to actually see and recognise an object apart from the background sky? If possible, please give a relatively simple understandable formula that directly takes the numbers of the factors and uses the numbers to directly calculate to a specific aperture that can be calculated using a scientific calculator and all algebraic symbols must be explained as to what it stands for and the formula can be used to provide an answer in the calculator withought confusion? If you have a formula, also please provide the units that each number is in. If you don't have a direct formula, can you use the numbers to do a simple estimation that isn't exact but uses the numbers directly? Also, as a side note, is the formula for the area of an oval π(sR * lR), where the symbol on the left is pi, and sR is half the shortest diameter and lR is half the longest diameter? If it's something else, can it be found on the article for oval? Thanks. ~ A H  1 (TCU) 19:01, 23 December 2007 (UTC)


 * If you mean an ellipse, then your formula is correct. Not every oval is an ellipse.
 * Considering the telescope aperture, I don't know a detailed formula for all the factors, but maybe this formula for the maximal magnitude helps you:
 * $$mag_{max} = mag_{max,eye} + 5 \cdot lg(d/d_{eye})$$
 * where magmax,eye is the maximal magnitude you can see with your eyes, d is the aperture, deye is your eye's aperture (maximally 4 mm) and lg is the logarithm on base 10. This assumes the object to be point-like.
 * Icek (talk) 10:42, 24 December 2007 (UTC)

Moon's hidden face
Why is the moon held in lock-step with the earth so only one aspect is visible, in contrast to the earth which is not similarly bound to the sun? - CarbonLifeForm (talk) 20:43, 23 December 2007 (UTC)
 * Check out the article on tidal locking and come back if you want more :) --Ouro (blah blah) 21:15, 23 December 2007 (UTC)


 * Gravity gets weaker the further away from the sun (or earth) you are. Tidal effects come about as a result of the difference in the strength of gravity because one side of the orbiting body is further away than the other.  That difference stretches the moon or planet slightly in the direction of the tidal force - if the body rotates, it is continually pulled and squashed by the tides (here on earth we can see the effects of that in the tides from our oceans - but it applies to solid rock too).  This 'kneading' of the material requires energy and the energy comes from gradually slowing down the rotation of the object.   Eventually, the body loses all of it's rotation and winds up with one face pointing towards the center of the orbit...typically the heaviers side, as you might expect.


 * The reason the earth isn't tidally locked - but the moon is, is because the Earth is about 150 million kilometers from the sun - but it's only around 13,000 km across. So as a percentage of 150 million km, the diameter is tiny - just one part in 10,000 - so there is very little difference in the sun's gravity between the two sides of the planet - and hence, very little tidal forces.  The moon, is about 400,000 km from the earth and 1,700 km across one part in 300.  So the difference in gravitational force between the two sides of the moon is large - but the difference across the earth is tiny.   The moon's gravity has a much bigger tidal effect than the sun's (because we are much closer) - but the moon's gravity is only one sixth of the earth's - and the earth has much more rotational inertia.  Eventually, even that tiny effect will cause the earth to be tidally locked so that one side of the planet will face towards the moon which will always appear in the exact same place in our sky.

That will result in the earth rotating just once a month - so our "day" would be a whole month long. But that's going to take a long time. Pluto and it's moon, Charon have already arrived at this exact situation because they are much closer to each other and they are of much more equal sizes than Earth and the Moon. As a result. they are both tidally-locked to each other.


 * SteveBaker (talk) 05:29, 24 December 2007 (UTC)


 * There are two details to add in the above, both of which strengthen Steve's point. First, 1/6 is the strength of gravity at the Moon's surface in proportion to that at the Earth's surface.  The relevant number here is 1/81, which is the mass of the Moon in proportion to the Earth.  (Gravity at the same distance from the center of the respective bodies will be in this proportion.)  And second, gravity doesn't just diminish with distance, it diminishes as the square of the distance.  When you consider this in combination with the explanation above, it works out that tidal effects diminish as the cube of the distance.  (Or using calculus: the derivative of 1/r² is proportional to 1/r³.) --Anonymous, 05:43 UTC, December 24, 2007, Earth.

battery
The battery of an electronic device originating in China opened (poor quality glue). The sticker claims that it is a Li-ion but it looks like it might not be. The highlighted part on the right is a weight which was glued inside the battery casing, and the highlighted part on the left is weird strip that appears to short-circuit that battery cells - it's silver at the terminals but black along its length. Any idea what that strip is? --Seans Potato Business 22:59, 23 December 2007 (UTC)
 * what makes you think it's not a li-ion cell? Could you post a clearer picture? Is the strip conductive? Does it actually connect to both terminals? Is the other terminal actually at the bottom of the battery? Furmanj (talk) 00:57, 24 December 2007 (UTC)
 * It looks like it's a 2 cell battery. Get a multimeter and measure the voltage.  If the battery measures > 4V, then it's Li-Ion.  Li-ion BTW in cylinderical form looks no different then regular batteries except for it's size.  Lithium ion polymer are the ones that comes in flat retangular shapes.  I can't tell for certain from your picture but it does look like li-ions.  The hint is the little device at the top, it should be a protection/charge circuit.  Regular alkaline battery would not need this.  Are you sure the black strip is not a piece of wire?  You would need to connect both end of the battery to use it.  The black strip looks like it's the negative wire.  NYCDA (talk) 19:29, 24 December 2007 (UTC)

Number of animals consumed during a human lifetime
I recently read a novel about vampires who had to kill someone for food every night. This made me think that in a way, non-vegetarian humans are like vampires - we kill to live. We eat animals, and also use leather. I'm not a vegetarian, and I wonder how many animal deaths I will be indirectly responsible for during my life? I often eat tinned sardines which have three or four lives in them. On the other hand eating a portion of bacon, which I never eat, only requires a small fraction of a whole animal. Does anyone know what my likely total score of animal deaths will be during my lifetime please? If I turn up at the pearly gates and find that God's a vegetarian or gives equal worth to animal souls, then I'm in trouble! This is not a pro-vegetarian rant, I'm just curious. 80.2.209.76 (talk) 23:50, 23 December 2007 (UTC)
 * Some random guy on the internet says 1000 animals over the course of a human lifetime (scroll about 8/9 down, or ctrl-f for "lifetime.") Personally, I think that number seems too small.--YbborTalk 00:20, 24 December 2007 (UTC)
 * EDIT:this more credible looking site, but still just a random guy's blog breaks it down into, "4 head of cattle, 21 sheep, 15 pigs, 1200 chickens and 13,345 eggs." A-ha! This same question was asked on Yahoo! Answers, which came up with about 6,600 animals, almost all of them Chicken & Fish. See the site for a more detailed explination (ot not!) of how those figures were derived. --YbborTalk 00:25, 24 December 2007 (UTC)
 * Okay, so it's one of those 'I heard it somewhere' stats - but apparently your average human will inadvertently consume 1lb of insects (or parts thereof) in a lifetime. --Kurt Shaped Box (talk) 00:42, 24 December 2007 (UTC)
 * I think it's higher than that. I used to room with an agriculture major, and if I recall correctly, the USDA allows ground flour and other processed grains to be as much as a few grams insect parts per kilogram of product.  Dragons flight (talk) 00:56, 24 December 2007 (UTC)
 * Hmmm. It may even have been 1lb *per year* then... Yikes. --Kurt Shaped Box (talk) 13:19, 24 December 2007 (UTC)


 * If one reckons lives like Renfield in Bram Stoker's Dracula, then he must total up not only the creatures he consumes, but the creatures they consumed as well, and the creatures consumed by them, etc. We eat few carnivorous mammals,(perhaps an occasional barbecued raccoon) but birds (including fowl) like to eat insects and worms. Many fish are also little predators. Edison (talk) 05:24, 24 December 2007 (UTC)


 * But what about all of the microscopic animals that we ingest all the time without even realising it? Those must amount to vastly more than the number of large mammals, fish, birds, etc.  SteveBaker (talk) 14:15, 24 December 2007 (UTC)

Unless you're counting 1 cow equaling 5 steaks or something, the number of individual animals killed, it's way higher than 1000 or even 6000. If you have, let's say on average, 2 different kinds of meat a day. That's 700 animals a year alone. That's a pretty low estimate, considering a hamburger, made from ground beef, is a collection of a whole bunch of different cows. Or chicken fingers, which are processed from a whole bunch of different chicken. -- MacAddct &#xF8FF; 1984 (talk &#149; contribs) 17:21, 24 December 2007 (UTC)
 * It all depends on how you count things. The question is, does the tiny bit of meat from each animal count as a whole animal, or are you allowing "fractional animals"?  For example, if you have something like sausage it may be made up of meats from many different animals (though they may all be the same type of animal).  If even microscopic amounts add another animal to your total, then breathing in or inadvertently eating pet dander from your pets counts towards your total.  That makes your count ridiculously high, and impossible to measure.  Also, it's not like you're consuming the whole animal yourself either, so this inflates the "death total" since one animal is recounted for every person who eats even a tiny part of it.
 * If, on the other hand, we use "fractional animals" instead, then any meat you consume counts towards the average amount of edible meat made from that kind of animal. If, for example, the average pig has 50 units (lbs/kg/whatever) of edible meat made from it, then you would only count up by one pig after you've eaten 50 units of ham/pork chops/etc., even though you may have eaten meat from many different pigs.  This way, a pepperoni pizza only adds a tiny fraction of an animal to your animal total, as opposed to many animals.  This gives you a much more realistic and countable measurement.
 * Finally, if the Judeo-Christian God exists, then there are numerous passages in the Bible that say that some meats are OK while others aren't (for example, see Leviticus 11), so that god isn't a vegetarian. Heck, according to the Bible the reason why God favored Able over Cain is that Able (a shepherd) sacrificed animals to Him, while Cain (a farmer) only brought plants (see Genesis 4:2-5).  God also finds the smell of burning animal flesh pleasing (see Leviticus 3:3-5 & 3:14-17).  I don't believe in gods myself, but if you're worried about that one then your problem isn't the number of animals, but the type, portions, and method of preparation. --  Hi  Ev  04:47, 25 December 2007 (UTC)

The number of individual lifeforms in one mouthful of a microbial culture such as cheese staggers the imagination. Do they count? If God cares about the numbers, I wouldn't worry about the cows when you get to Heaven - it's the quadrillions of bacterial deaths you've caused in your lifetime that you'll be responsible for. 74.12.208.131 (talk) 17:00, 25 December 2007 (UTC)
 * Bacteria are not animals. Animals are (by definition) multicellular. SteveBaker (talk) 16:12, 26 December 2007 (UTC)


 * Just last holiday week I probably ate 4 dozen raw oysters, a couple dozen snails, some mussels and some squids and shrimps, some frog's legs, salmon, foie gras...that gives me a kill-rate of almost 100 animals in 7 days. As for the people who eat beef and determining what counts as a "kill" cow-wise - that reminds me of those problems in Analytic philosophy and possible-world theory where they ask you to determine "The mereological sum of all cats in all possible worlds" and then tell you that there are X worlds where there are only cat tails!  S a u d a d e 7  14:17, 29 December 2007 (UTC)