The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
Why does the cyanpigment in various colored posters get retained rather than the other ones? I've seen posters and other materials exposed to the sun and/or rain having only a faded cyan colored image.--Lenticel(talk)01:30, 1 July 2009 (UTC)[reply]
Different pigments have different lightfastness, and the difference in the lightfastness isn’t due just to the color of the pigment per se. For example, the Monastral Blue cyan pigment has better lightfastness than the Tartrazine Yellow Lake yellow pigment, but the Hansa Yellow G yellow pigment has better lightfastness than the Peacock Blue (erioglaucine) cyan pigment. The reason the cyan pigment in multiple posters appears to have the best lightfastness of the pigments used is because in any part of the world, certain pigments tend to be the most commonly used there, due to economic and other factors. For example, in Europe, the Univit Blue Primaire and Major Blue Primaire cyan pigments are popular, which both have a lightfastness of 8, and the Major Yellow Solid and Major Yellow Primaire yellow pigments are popular, which have a lightfastness of 5 and 3, respectively.[1]Red Act (talk) 04:00, 1 July 2009 (UTC)[reply]
You would have to give a precise definition of "black man", "white woman", and "completely white" for that question to be answerable. None of these are scientifically defined concepts. If the real question is whether Michael Jackson could have fathered Michael Jackson's children, the answer is that I don't know. Looie496 (talk) 03:12, 1 July 2009 (UTC)[reply]
based on Mendelian inheritance probably not. But human skin color is not simply due to the interactions of a dominant black gene and a recessive white gene like the classic black mouse x white mouse experiment. In fact, we still don't know much behind the genetics of skin color. So it is possible but we just don't completely understand the genetics. --Lenticel(talk)03:30, 1 July 2009 (UTC)[reply]
I'd say "yes". If the black man was actually mixed race (one black parent, one white parent) then they could, theoretically, give all the skin colour determining genes from the white parent to their child, resulting in a white child. Plenty of people of mixed heritage look plenty black enough to be called a "black man". I don't know what the odds of it happening are, though - the genes determining skin colour are rather complicated and I don't begin to understand them (I'm not sure anyone does). --Tango (talk) 03:50, 1 July 2009 (UTC)[reply]
Statistically, it depends on whether the white-determining part of the gene is recessive or dominant. In all the attention that has been paid to race, has this ever been investigated? - GlowWorm. —Preceding unsigned comment added by 98.17.43.38 (talk) 04:36, 1 July 2009 (UTC)[reply]
As Looie496 points out, this isn’t really a science question, since “black man”, “white woman”, and “completely white” are all subjective, unscientific terms. However, in my subjective opinion, Vin Diesel looks “completely white” in most photos I’ve seen of him, even though one of his two parents is African-American. Also, Wentworth Miller definitely looks “completely white” to me, even though his father would count as a “black man” at least according to the one-drop rule. Red Act (talk) 04:47, 1 July 2009 (UTC)[reply]
It's debatable as to whether the term “race” is biologically meaningful. For example, according to the race article, in a survey taken in 1999, 69% of the physical anthropologists and 80% of the cultural anthropologists surveyed disagreed with the statement "There are biological races in the species Homo sapiens." Increasingly, in scientific circles, concepts such as “population” and “clinal gradation” are used, instead of trying to divide people into “races”. Red Act (talk) 05:12, 1 July 2009 (UTC)[reply]
Lamarckism (once popular, but more recently said to be discredited) says that acquired characteristics, such as a black man managing to turn his skin white, could be passed on to his children. Edison (talk) 05:33, 1 July 2009 (UTC)[reply]
It's not just said to be discredited, it is discredited. We not only have enormous amounts of evidence for Mendelian inheritance but we have a considerable understanding of the mechanism behind it. --Tango (talk) 05:49, 1 July 2009 (UTC)[reply]
To answer the OP's question: If, by "black" and "white", he/she means "pure black" (i.e. with only black ancestors and no white ancestors) and "pure white" (i.e. with only white ancestors and no black ancestors), then, IMHO, the children would probably look like light-skinned black children (I think "mulatto" is what they used to be called, but I'm not sure); if, however, either parent had even a slightly mixed ancestry, then a wide range of appearances would be possible, from white with a somewhat tan complexion to a fairly dark black. So my own answer to the OP's question would be "probably yes", but that's just my own unscientific opinion. FWiW
76.21.37.87 (talk) 07:09, 1 July 2009 (UTC)[reply]
But then who do you count as a “black” ancestor or a “white” ancestor? Median skin color, for example, varies in a fairly gradual cline as you consider a series of populations along a path from sub-Saharan Africa, through northern Africa and the Mediterranean area, and up to northern Europe. See this map of skin colors. At what point along that path do you consider the gradually changing median skin color to no longer be “black” and start to be “white”?
You’d also need to define how far back you’re looking when you’re considering who an “ancestor” is. According to the Environmental factors section of the human skin color article, it only takes about 500 to 1000 years for the average skin color of even a fairly isolated migrating population to adapt to be what’s ideal for the amount of UV light that the sun shines on a given latitude.
And what all phenotypes do you consider when you’re categorizing an ancestor as “black” or “white”? Presumably more than just skin color? But if you look at all the world’s populations, the other phenotypes that you might use to distinguish “black” and “white” don’t necessarily vary in sync with skin color, since the sun exposure that creates an evolutive pressure on skin color is different from the other environmental factors that create evolutive pressures on other phenotypes. Red Act (talk) 08:08, 1 July 2009 (UTC)[reply]
People seem to think this is a purely theoretical question and we don't really know. Well, look, here. Yes it is possible, yes it happens, and yes very few people (if any) have no ancestors of a different 'race' if you go back 20 or 30 generations. 89.168.19.118 (talk) 10:10, 1 July 2009 (UTC)[reply]
I'm a bit suspicious because: The water's very clean, the lighting is ok, the camera work is kind of ok (not too jerky when walking, focus changes a bit strange), the pulses the thing does look quite destructive - if they do that too much, they look like they'll fall off the wall. I'm no expert in sewer lifeforms or film-making, so I'm very ready to be corrected in everything I said. Aaadddaaammm (talk) 10:18, 1 July 2009 (UTC)[reply]
Apparently they are fairly well known in the industry
That story says "in 20 years of sewer work, they had never seen anything like it before." - that doesn't sound like "fairly well known in the industry" to me! The first video makes it look like these things are pretty big - but that's a robotic camera in a fairly narrow tube - so they could be as small as a centimeter or so. I agree that this appears to be something like a bryozoan - and our article says that there are 8,000 species of them to choose from, so it would take an extensive and difficult search to rule out that possibility. SteveBaker (talk) 12:22, 1 July 2009 (UTC)[reply]
The video claims it's from a sewer, but I don't buy it. It looks like the camera is zoomed in on something else, indicating that everything in this video is tiny. The water seems to be behaving like it's just a small quantity of water as opposed to how water would behave in a normal sewer... So what the heck is it? ScienceApe (talk) 19:00, 1 July 2009 (UTC)[reply]
I don't know what the "creature" is, but it looks like a pretty normal sewer pipe to me (a small one, but they come in all sorts of sizes). --Tango (talk) 19:02, 1 July 2009 (UTC)[reply]
My guess would be internal medical imagery, probably during some surgery, perhaps with some type of artificial irrigation. Bus stop (talk) 19:05, 1 July 2009 (UTC)[reply]
The video is legitimate. According to Raleigh city officials:
... staff biologists have confirmed that the "creature" is actually a colony of tubifex worms. The colonies attach themselves to roots that gradually work themselves into weak points in the pipes. "They seem to respond to the light from the camera," Buchan said. "That light is pretty hot." The worms naturally occur in sewage and pond sediment and are actually sold both live and dried as fish food in pet stores.
Suppose the sun explodes at this moment and separates into two halves traveling in opposite directions at high velocities. The sun's gravitational field will change immediately and affect the Earth's orbit instantly (slightly at first). But it will take about 8 minutes for the electromagnetic radiation from the exploded sun to reach Earth. Why does gravitation have an immediate effect on distant objects, but the effects of electromagnetism are delayed? If gravitons exist, they must travel faster than the speed on light. How is this possible? David 70.55.183.195 (talk) 13:06, 1 July 2009 (UTC)[reply]
If the speed of gravity was in fact infinite, would it be possible/practical to build a gravity-based telecommunications medium with enough bandwidth to, say, have a chat session with someone on Mars? Let's say 10 bytes per second. For the transmitter I'm thinking something like an array of heavy objects on maglev tracks that you scoot back and forth to indicate on and off bits, and a LIGO-type rig for the receiver. --Sean13:29, 1 July 2009 (UTC)[reply]
As was stated above, the speed of gravity equals the speed of light, so it is not infinite. Discussing what would be possible if it was infinite is not scientific and cannot be answered by scientific means, which means it is out of scope of this reference desk. --TheMaster17 (talk) 13:52, 1 July 2009 (UTC)[reply]
Given fallibility, is there really such a thing as an unscientific discussion about imaginary physics? The discussion could be outside of any existing body of knowledge, and futile, but that's not the same as unscientific. 213.122.68.63 (talk) 15:37, 1 July 2009 (UTC)[reply]
Science has to be falsifiable. If I theorise that "If the speed of gravity were infinite real time communication with Mars would be possible" then that isn't falsifiable since there is no experiment that can show it to be true or false since the premise is false. Obviously it is possible that our understanding of gravity is flawed and it does travel at infinite speed, but that makes the question unanswerable since the premise would mean we have no real understanding of gravity on which to base an answer. --Tango (talk) 17:28, 1 July 2009 (UTC)[reply]
Right. We could similarly note that if the speed of light were infinite, LEDs could allow real-time conversations with Mars, or that if the speed of pigeons were infinite, RFC 1149 would finally be worth implementing. — Lomn14:00, 1 July 2009 (UTC)[reply]
I do agree that just asking how the relevant equations would change if one of the constants was different is not "unscientific" at all. There have been many instances where measured or theoretically derived constants were incorrect, and the last time I checked questions about the propagation of gravitational waves were still considered active research. There is nothing wrong in a little careful speculation, and it does not make it "unscientific" (it is not asserting a non-falsifiable theory or anything like that). --98.217.14.211 (talk) 20:23, 1 July 2009 (UTC)[reply]
I don't think making the speed of gravity infinite can be considered as just changing the value of a constant. "Infinity" is not a real number so all the equations that are based on the speed being a real number (ie. any equation in which the constant appears) will cease to work. --Tango (talk) 20:36, 1 July 2009 (UTC)[reply]
Since the responses to my first run at this question focused on the science rather than the engineering, I'll try again: would it be possible to build a reasonably fast machine for moving mass around on Earth that could be detected on Mars (after a suitable delay!). --Sean19:19, 1 July 2009 (UTC)[reply]
I think your question was perfectly reasonable. We have a theory of infinite-speed gravity, namely Newton's, and wireless gravitational communication is possible in Newton's theory. To communicate wirelessly you only need a change in the charge distribution in one place to affect the field in another. It doesn't matter how long it takes for it to happen.
Take a generic 1/r² force law (instantaneous or retarded, doesn't matter). I'll write it as , though M and m might be electric charge and G might be the Coulomb force constant. Let the emitting and receiving stations be separated by a distance D. Suppose the emitting station consists of a charge M moving in a circle of radius d at a frequency ω in the plane perpendicular to the line between emitter and receiver. It's easy to see that the force at the receiving station will "precess" around a central value at the frequency ω. Because the force is aligned with the source, the slope of the force vector relative to the emitter-receiver line is d/D, so the amplitude of the circular component is about d/D times the absolute value of the force, or . Of course, this force has to be added to the influence of every other object in the universe, but the time-varying component will still be there and you will probably still be able to detect it, as long as relatively few nearby objects are rotating at that exact frequency. That's how radio communication works, roughly. However, this doesn't work for gravity, because there's no way to detect the force! The only way to detect force is by the associated acceleration, and the only way to detect acceleration is by comparing to a nearby inertial object, but there are no such objects in this case because gravity acts on everything equally. All you can detect is the local variation in the force, i.e. the first derivative. The first derivative will look like a spring force law, ΔF = k Δx, but with three different constants k along three perpendicular axes of symmetry. In this case the symmetry axes are obvious: the line between emitter and receiver, the (time-varying) direction between the object and the center of rotation, and the direction perpendicular to those. The force constants along those three axes are, respectively, , , and . The first of these doesn't help much because it's constant. But the other two axes rotate into each other over time, so we will see a sinusoidal variation in the force constant in that plane with an amplitude of and a frequency of 2ω. This will lead to a sinusoidal oscillation in the distance between two test particles. The amplitude of that oscillation is proportional to the distance, and the (unitless) proportionality constant is . And that, at long last, is what LIGO measures. According to online sources it's most sensitive at around 200 Hz, where its design detection threshold is about 10−23. So let's plug in some values. Take M = 10 kg, d = 10 m, 2ω = 2π × 200Hz, and D = 56 million km (the closest approach between Earth and Mars). And the result is... about 10−67. So the answer is: not a chance in hell. Note that that's just to unambiguously detect the existence of the carrier signal—never mind modulating it, and never mind doing so fast enough to communicate at 80 bps. -- BenRG (talk) 19:37, 1 July 2009 (UTC)[reply]
Hmm, I think there's something wrong with my brilliant argument because it makes orbiting pulsars very undetectable too. Better ignore it for the time being. -- BenRG (talk) 20:02, 1 July 2009 (UTC)[reply]
Why do you have the tidal forces following a sping-like law? I thought they followed an inverse cube law. --Tango (talk) 20:37, 1 July 2009 (UTC)[reply]
Possible? Eh, maybe, sorta, kinda, in a hideously expensive utterly impractical sort of way, if we worked out all the necessary science and engineering first. Our gravitational wave article covers the underlying principles of such a system. Or we could use perfectly good electromagnetic methods of communication. — Lomn19:42, 1 July 2009 (UTC)[reply]
Note: part of the reason we're unlikely to ever care about this, as a practical matter, is that gravity is 1036 times weaker than EM radiation. It's very difficult to construct a scenario in which perceived advantages of gravitational communication outweigh this massive roadblock. — Lomn19:45, 1 July 2009 (UTC)[reply]
I think that's why he originally asked the question about a universe where gravity moves faster than EM radiation. -- BenRG (talk) 20:02, 1 July 2009 (UTC)[reply]
Question regarding dBm
In a book I've been reading, I found the following statement (among other similar statements):
200 mW –3dBm = 100 mW
Is this correct? Why is the result 100 mW and not 198 mW? If it is, what's the explanation for it?
It is correct, but in perhaps a dfficult form for beginners to understand. See dBm. dBm is logarithmic unit of power, so it is non-linear. Power in dBm is defined as 10 * log (P / 1 mW), where P is a power in mW. Using the properties of logarithms, adding and subtraction in logs is equivalent to multiplying and dividing. So since the inverse log of 3 dBm is 2, -3dBm is the same as saying divide by 2. Usually people wouldn't mix units of mW and dBm in the same equation, but the author probably thought it would be okay since -3dBm is very easily recognized as being one half. —Akrabbimtalk16:32, 1 July 2009 (UTC)[reply]
It's still wrong though. dBm is an absolute unit, so 3 dBm is close to (note, not exactly) 2 mW under all circumstances, just as -3 dBm is about 0.5 mW. In no case can "-3 dBm" mean divide by 2. Only "-3 dB" can mean that. So the OP's expression, if it means anything at all, must mean ~198 mW. If the writer intended it to mean 200 mW / 2, then he should have written 200 mW x (- 3 dB), although that's still an incorrect use of the terminology. --Heron (talk) 17:08, 1 July 2009 (UTC)[reply]
You're right, it really is the question's fault. What I explained in my first answer, is if 200 mW is converted into dBm (23 dBm), and then 3 dBm is subtracted, then the answer is 20 dBm, or 100 mW. Or, if we wanted to convert the second term into mW, we wouldn't know if we were adding .5 mW or subtracting 2 mW from 200 mW. Now that I think about it, adding or subtracting dBm from mW is very ambiguous, and meaningless in equation form. —Akrabbimtalk19:37, 1 July 2009 (UTC)[reply]
You should never add (or subtract) things that are measured in different units, so the equation is clearly nonsense. It could work as an abuse of notation, but, as you say, it is rather ambiguous as to what the abuse is meant to mean. --Tango (talk) 01:48, 2 July 2009 (UTC)[reply]
With respect the first response contains errors. -3dB is the same as saying divide power by 2 (more exactly by 10.3 = 1.99526...). That is a dimensionless ratio. The little "m" in -3dBm means 1mW divided by 2 which is 0.5mW. That is a power. What the OP read in an unspecified book is flat wrong and the author should have written
Florida stone crabs are said to be one of two animals whose meat can be harvested without killing it. What is the other animal?
Some species of lizards drop their tails when they are grabbed. That is a potential for some meat without harming the lizard. Best that I can come up with. 65.121.141.34 (talk) 18:12, 1 July 2009 (UTC)[reply]
Autotomy appears to be the relevant concept here, and there are more than two species that could conceivably have meat harvested in this fashion. Additionally, I would submit that severing an animal's appendages is not inherently "humane" if you're examining the moral issues of eating meat. — Lomn19:04, 1 July 2009 (UTC)[reply]
A traditional food of the Maasai people is a blood porridge of some kind, the blood having been harvested from cattle that they keep around for that purpose. Blood isn't meat, I suppose, but I don't think too many vegetarians drink it. --Sean20:06, 1 July 2009 (UTC)[reply]
Is there any evidence people could not conceive, gestate, and give birth to children in space? I'm curious if there has been any multi-generational studies of animals in space and how that data would correlate with people. Would the fetus develop properly in the absence of gravity? TheFutureAwaits (talk) 17:44, 1 July 2009 (UTC)[reply]
[4] from 1995 describes some experiments with pregnant rats in space for part of the gestation, and says that multigenerational animal experiments were planned for the International Space Station. A 2002 NASA report [5] says on page 32 that they still would like to do multigeneration studies on primates in space, but offers no hint that any multigeneration studies had been done by then. If you email NASA they might be able to search their database and provide a more definitive answer. Edison (talk) 17:50, 1 July 2009 (UTC)[reply]
Animals in space lists the longest animal flight as 90 days - unfortunately the tortoises involved didn't quite have enough time to make multiple generations. Other shorter lived animals have flown though. Rmhermen (talk) 22:18, 1 July 2009 (UTC)[reply]
I assume you mean "in zero gravity". It's possible to closely simulate terrestial conditions in space, in which case I can't imagine any reason why pregnancy would not proceed as usual. Dcoetzee01:37, 2 July 2009 (UTC)[reply]
My Astronomy professor said that there seems to be some problem with pregnancy in space, in that it seems to cause miscarraiges in animals. If it is the same for humans—and it very well may be—then on long voyages, women may have to spend nine months in a rotating chamber that simulates gravity. —Pie4all88TC03:11, 2 July 2009 (UTC)[reply]
As has been pointed out, it is not yet verifiable whether a rotating chamber inducing a gravity-like force is "identical" to terrestrial conditions. There are a lot of confounding factors beyond the first-order net "downward" force that is felt inside a rotating chamber. Nimur (talk) 03:17, 2 July 2009 (UTC)[reply]
I see there's another thread about artificial gravity, so I'll read through it when I get a chance. Thanks for the info! —Pie4all88TC07:19, 2 July 2009 (UTC)[reply]
I'm curious to know the potential difference between one of a single-phase alternator's lines and the ground when this alternator has its neutral not connected to the earth? --Email4mobile (talk) 17:47, 1 July 2009 (UTC)[reply]
Good question. It is undefined, since you have specified no neutral to ground connection. The voltage in practice might be anywhere from zero to the output voltage from either conductor to ground, since there will be leakage current and capacitive coupling to ground. In practice, if there were a voltmeter from each output line to ground, the measurement circuitry would constitute a high impedance ground connection and would determine the voltage measured. If only one voltmeter were connected to one line at a time, it would pull the measured line down and force the unmeasured line higher. Three phase equipment in factories is sometimes designed to be operated ungrounded, because the first unintentional ground does not cause fault current. Ground indicator lights or equivalent relays are used to detect such a ground, and it can be found and fixed without necessarily having an emergency shutdown, There, similarly, the ungrounded phases rise to a high potential to ground while the grounded phase goes to a low or zero potential to ground. Edison (talk) 18:13, 1 July 2009 (UTC)[reply]
Thank you very much indeed. I've tried to find an explanation for that problem once, and assumed the capacitive effects. However when I started simulating that measured voltage via mathematical equations I was stuck by the equivalent circuit to be analyzed due to my insufficient knowledge in this subject and poor imagination of capacitance and impedance patterns. It would be more helpful if you know a reference which details this problem (and have a good day/night. I'm going to bed).--Email4mobile (talk) 18:52, 1 July 2009 (UTC)[reply]
Is the alternator in your car connected to earth ground? Do you feel yourself to be indanger in the car because there is no wire from the neutral terminal to earth ground? How about in an airplane? How about in the International Space Station or the Space Shuttle? There is a neutral but it is not connected to earth ground. How about on a ship? In the early days of marine elecrical systems, some countries used the phase and neutral isolated from the ship hull, and others used the hull as a ground to which the neutral was connected. It is possible that a load element or the alternator winding itself might have graded insulation, with a lower insulation level near the terminal that is supposed to be at earth potential, like the frame of the alternator, particularly if it has a very high voltage output. In such a case, the case of the alternator might be at a dangerously high voltage, or the insulation might fail. A low voltage alternator is likely to have the same insulation level at all points on the winding, and the neutral and phase wires are likely to be of the same insulation rating. In that case the alternator, switch, fuse, wires, and load would probably work with or without the grounding of the neutral. It is basically a safety measure, so that there is less risk of a dangerous voltage on the neutral or frame, or on unswitched and unfused conductors. It also allows fuses or circuit breakers to operate if the phase or intended hot wire becomes accidentally grounded through a break in the insulation. Edison (talk) 00:05, 3 July 2009 (UTC)[reply]
Regarding the car/plane/ship alternators: although they are not connected to earth ground, they are connected to the bodywork/airframe/hull instead, so technically they are still grounded, even though there's no connection to earth ground. Note also that in all these cases, the bodywork/airframe/hull would act as a Faraday cage and thus protect the occupants from getting zapped even if the insulation fails on the alternator. What I meant was that an alternator with its neutral not connected to anything at all would likely be dangerous, especially if it operates at a high voltage.
76.21.37.87 (talk) 03:48, 4 July 2009 (UTC)[reply]
Position basis of a wave function
In literature I'm reading about intro quantum mechanics talking about single particle wave functions, they often discuss them in terms of the position basis (including here: wave function) and other continuous bases like the momentum basis. I was under the impression that wave functions as functions over the points in space lived in L2(C), since they use that inner product and norm. But the position basis (or any other uncountable set) isn't a basis of L2 and similarly Dirac delta functions aren't in L2 since functions that are equal a.e. are put in the same equivalence class. If not L2(C), then what Hilbert space are wave functions supposed to live in? What's going on here? —Preceding unsigned comment added by Rckrone (talk • contribs) 18:40, 1 July 2009 (UTC)[reply]
If it is a good book, this should be declared in some kind of intro section. Ah, and if you really have a good book on quantum mechanics, please tell me, for I don't know any. Sorry if this isn't helpfull. Hoping there will be better responses. I would like to know the answer myself, too. 93.132.130.9 (talk) 20:04, 1 July 2009 (UTC)[reply]
The Dirac delta "function" is not a function at all, not even in . There's no way you could arrange for its integral to be 1. Expressions involving the delta function are really implicit limits of expressions involving normalized Gaussians or suchlike as the width goes to zero. The delta function by itself wouldn't make sense but an expression incorporating it is legitimate as long as the limit of the whole expression exists. Likewise the position "basis" is really a limit of fuzzy Gaussian-like distributions of position, and one requires (or at least hopes) that expressions that define quantities of physical interest converge sensibly in the limit. That's how I think of it, anyway. -- BenRG (talk) 22:00, 1 July 2009 (UTC)[reply]
One does not have to pretend that statements involving deltas are just shorthands for statements about limits. The dirac delta function is a perfectly good mathematical object, it's just not a bona fide function on the reals. It's a measure or a distribution or something (depending on your point of view). Algebraist22:04, 1 July 2009 (UTC)[reply]
But Dirac delta functions aren't in the dual of L2 either. δx would the functional that maps f to f(x), but an element of L2 is an equivalence class of functions that are equal a.e., so they're free to differ at x. On the other hand thinking of it as an idealized limiting case definitely clears some things up, but I'm still not satisfied with the idea of the position "basis." It's certainly not the limit of some sequence of bases. It has the wrong cardinality among other problems. Rckrone (talk) 04:00, 2 July 2009 (UTC)[reply]
For some reason drinking plain water makes me feel sick, but I can consume any other drink just fine, even flavoured water, which doesn't seem like it would be different enough to... be different. What's the deal? Vitriol (talk) 22:39, 1 July 2009 (UTC)[reply]
Is it any plain water or just the plain water from a certain area? What about bottled water? There are places which have tap water I find very unpleasant, possibly even to the point of making me feel unwell. It's just the taste, as far as I know. --Tango (talk) 22:37, 1 July 2009 (UTC)[reply]
I dunno if water from the ice dispenser and the tap would be different, but if it is then both make me wanna barf. And it's definitely not the taste. Vitriol (talk) 22:39, 1 July 2009 (UTC)[reply]
Presumably the ice dispenser gets its water from the tap? When you say "flavoured water", do you mean water that is bought with flavouring or tap water with orange squash or similar added? If its the latter, then it must be the taste, that's the only thing that is different. --Tango (talk) 23:27, 1 July 2009 (UTC)[reply]
My understanding is that fluids with low osmolarity (concentration of dissolved substances) are hard for the stomach to absorb, and that almost any dissolved substance will help. Looie496 (talk) 01:07, 2 July 2009 (UTC)[reply]
You'll have to be clearer what you mean by plain water. If you're drinking distilled water, the sort used for scientific experiments, that's going to taste bad and cause the problems described by Looie496. But tap water usually contains a variety of dissolved impurities. If your tap water makes you feel sick, it's probably something in the water, perhaps some kind of allergy (since it's evidently not making everyone sick). Dcoetzee01:41, 2 July 2009 (UTC)[reply]
If the same water which makes you sick when plain does not make you sick when something is added to it, the cause of the illness is probably psychosomatic; there is no allergan or pathogen in the water, but for some reason the thought of drinking plain water sickens you... --Jayron32.talk.contribs03:52, 2 July 2009 (UTC)[reply]
Yeah, I have a similar problem and I strongly suspect it's psychosomatic. If I drink any plain water within an hour or two of waking up, I generally feel rather sick - but I can drink tea, or orange juice or whatever and feel fine. I can also drink plain water later in the day and feel fine. I can't think of a good scientific reason for this, so I assume it's just my brain playing with me - or just the fact that the tap water here tastes a little horrible and I'm more delicate in the morning! ~ mazcatalk08:35, 2 July 2009 (UTC)[reply]
It may not be psychosomatic. It's possible that the water that's been sitting in your household plumbing all night has picked up some dissolved chemicals - and that the oxygen dissolved in it has dispersed - making it taste 'flat'. Later in the day - when everyone in your neighborhood is using lots of water - and the stuff that's been in your pipes all night has been flushed or showered - you should be getting more aerated water that hasn't been soaking up who-knows-what from your pipes all night. Ergo: Either run water to waste for a few minutes before drinking any - or perhaps shake the stuff up vigorously with air to aerate it. SteveBaker (talk) 11:26, 2 July 2009 (UTC)[reply]
Try half-filling a bottle with the water, closing it, and shaking it pretty hard for a little while, to dissolve some air into the water. That may make it more palatable to you. Or, add a few drops of lemon juice. 208.70.31.206 (talk) 07:42, 2 July 2009 (UTC)[reply]
I get this too, i always thought it was to do with stomach chemistry, drinking plain cold water would be a shock to your system and dilute your pre breakfast stomach juices. I think even adding a spoon of sugar in tea or orange drink or whatever you put in the water would give the empty stomach something to do, so to speak, rather then just diluting it. Mind you, the first thing I usually drink is a hot black coffee with no sugar, so maybe the temperature has something to do with it? There are some chinese people at my work that drink plain hot water from the urn, they believe it's better for you then cold water. Vespine (talk) 00:06, 3 July 2009 (UTC)[reply]
What is the proper name for the nose condition sometimes colloquially called 'Karl Malden nose' (where the person's nose is all bulbous and has a strange texture to the skin)? Note, I don't know if KM actually had this - but his death today reminded me of the subject. --90.240.60.140 (talk) 23:01, 1 July 2009 (UTC)[reply]
Rosacea of the nose, as seen in people like Karl Malden and W.C. Fields was commonly called "gin blossom", as alcohol-thinned blood tended to make the thin blood vessels in that part of the nose rupture it used to be assumed (incorrectly) that alcohol caused the problem ed note: changed due to valid point made by Richard Avery below ; the swollen nose is similar to cauliflower ear. See also the description of the origin of the band name of the Gin Blossoms, who took their name from the phenomenon. --Jayron32.talk.contribs03:48, 2 July 2009 (UTC)[reply]
"alcohol thinned blood tended to make the thin blood vessels in that part of the nose rupture". Do you have a citation for that Jayron? The scientific cause of rhinophyma [[6]], [[7]], [[8]]appears to be unknown at present although there are a number of associated signs that can predict its occurrence. Richard Avery (talk) 07:41, 2 July 2009 (UTC)[reply]
First you need to define "acceptable" - this term does not have a specific meaning in mathematics. Do you mean "finite-valued," "bijective," or some other description of a function? Acceptable redirects to Proper, which does have several mathematical meanings - but out of context, I think it's too vague to pick which meaning is intended. You mentioned wave-functions, so do you intend to show that the integral of e^ -|x| is integrable and that the probability function integrates to 1? If that is your intent, you should perform the integral and check whether it is suitable for your problem. Nimur (talk) 03:34, 2 July 2009 (UTC)[reply]
I am assuming the domain is Quantum Mechanics...I don't think it needs to Integrate out to 1, if it doesn't, you can always normalize it..The important thing is, it must be finite. So, I think being continuous and well defined in the whole region from minus infinity to infinity would do... So now you can see it is satisfies both conditions... I'll leave it for the experts to explain more... Rkr1991 (talk) 05:27, 2 July 2009 (UTC)[reply]
Having been bitten (by midges, I suspect) no less than 10 times in the past two days, I've declared a state of emergency and am searching for a way to combat this continued assault. I would like something cost-effective and long-term and low-maintenance.
I've heard that moving-air is a deterent.
I've been told that barbed-wire wont help.
I've read that cheap consumer units for electric-based destruction are ineffective (insects not attracted to blue ("UV") light) - I have first-hand experience of this, from a couple of years ago
I'm considering deet but it may dissolve my mosquito net (which I suspect is made out of some plastic polymer) and needs to be replaced every day.
I'm a student, living in a single room, so I don't have a large area to cover but I don't think my windows are amenable to nets due to their manner of opening, besides which insects can invade via housemates's rooms.
I've had problems with flies in the past. Sticky fly paper is the way to go - just hang up a bunch of them. It works, and you can see it work. Also make sure you don't leave wet trash out - that's where flies breed. Don't trust in ultrasonic deterrents. You can also look at some of the heavy duty systems used in horse stables - you can read more for example here. Actually fly zappers do work, but this can depend on the particular type of fly. Dcoetzee01:48, 2 July 2009 (UTC)[reply]
I've had some success with insect repellent candles, particularly if you are sat out on a balcony in the evening, or something. --Tango (talk) 01:56, 2 July 2009 (UTC)[reply]
You might be able to find Neem oil at a local health food store, herbalist or flea-market nl:Azadirachta indica. Try a bit on a paper towel first, some people find the smell hard to bear, others hardly notice. (OR To me it sort of smells like cold vegetable soup.)71.236.26.74 (talk) 09:14, 2 July 2009 (UTC)[reply]
It's claimed that biting insects are attracted to carbon dioxide (that's how they find living, breathing things) - there are several CO2 generators out there that claim to be able to rid you of mosquitoes "naturally". Sadly though, this may not help our OP - you wouldn't want to use one of those indoors for obvious reasons. SteveBaker (talk) 11:19, 2 July 2009 (UTC)[reply]
Try any of the artemsia plants, especially southern wood. Unfortunately the fly family, Tabanidae (horseflies & deerflies) find you using visual cues. 67.193.179.241 (talk) 14:39, 2 July 2009 (UTC) Rana sylvatica.[reply]
I removed the leading space from your answer 67.193, so that it didn't extend further that the width of the page. Hope you don't mind! --Kateshortforbob15:46, 2 July 2009 (UTC)[reply]
The best insecticide/repellent I have ever used is a pyrethrin-based aerosol. Gets rid of all flies, mosquitoes, midges, cockroaches... Have a google search for pyrethrin-based products available in your part of the world. Gwinva (talk) 04:19, 3 July 2009 (UTC)[reply]
Who has a "blood-brain barrier"?
Obviously, humans do. Animal experiments are mentioned, so perhaps all mammals have the blood-brain barrier; is this true? What about other animals which have brains; do they all have a blood-brain barrier, or ??? Thank you. - Hordaland (talk) 05:06, 2 July 2009 (UTC)[reply]
This is an excellent question indeed. I know mammals have a BBB as adults, but usually do not have a functional BBB when very young. I also know that birds (or at least some birds) have a BBB. As for other vertebrates - I don't know, and I could not find anything useful in Google Scholar. I know frogs have a functional choroid plexus, though, so they may have a BBB as well. I'll do a more thorough search tomorrow. I don't know if arthropods have anything homologous to a BBB, either. Of course arthropods can not have a proper BBB, as they do not possess a closed circulatory system to begin with; however, they may still have some sort of an epithelial barrier preventing at least some parts of their nervous system from the direct contact with the haemolymph. Anyway, great question. I'll fix the article, but I need to do some reading first :) --Dr Dima (talk) 07:15, 2 July 2009 (UTC)[reply]
All vertebrates have a BBB that consists of epithelial cells. Some invertebrates have an analogous system (insects for example), that consists of glial cells that surround blood vessels. Some sources taken out of the german wikipedia article (which is much more scientific and complete than the english one): [9], [10], [11] --TheMaster17 (talk) 09:31, 2 July 2009 (UTC)[reply]
Due to the limit of speed for the propagation of waves being based on the characteristics of the medium through which the wave travels, what would be the characteristics of the medium (Ether) through which light and gravity travel in the absence of transparent materials like glass such as the vacuum of space?
Our electromagnetic wave equation article may be of use to you. The equation, derived from the Maxwell equations describes the propagation of electromagnetic fields through a medium. It turs out the speed of propagation is dependent on the electric permittivity and magnetic permeability properties of the medium. For a vacuum, these are known universal constants (see vacuum permittivity and vacuum permeability). OP, did this answer your question? I couldn't tell if you were actually asking about the obsolete luminiferous aether theory, annd the last bit of your final question was worded oddly to me. —Akrabbimtalk10:32, 2 July 2009 (UTC)[reply]
Our OP seems a little confused - so let me try to spell it out more simply.
When we talk about the speed that electromagnetic and gravitational waves are moving - we have to be extremely careful. Light does "slow down" when it moves through air or glass or something (that's why lenses and prisms work - and why diamonds are so sparkly). But then we're talking then of the "group velocity" of the waves (the speed at which information carried by the wave travels) - not the "phase velocity" (the speed that the actual waves move)...it gets a bit technical/mathematical and it's hard to explain in words without getting into deep waters! This image may help though:
The red dot moves at the "phase velocity" - a speed which represents 'c' - "the speed of light in a vacuum" - the thing that is the cosmic speed limit. This speed never changes - no matter what the medium is.
The green dots are moving at the "group velocity" - the speed at which a change in the size or frequency of the waves can be propagated. This speed is slower than the phase velocity in air, water, etc - but happens to be the same as the phase velocity in a vacuum. When you hear of scientists "slowing down" or even "stopping" light - they are talking about the group velocity.
In a true vacuum, the two speeds are exactly the same. Unfortunately, when we use the term "the speed of light" - we tend to get slightly fuzzy about which speed we're talking about. For all of the exciting relativity kinds of thing - we're talking about the phase velocity - and we should strictly be saying: "the speed of light in a vacuum" or "the phase velocity of light" - and not just "the speed of light" because that is confusing. For measuring the speed of light in (for example) air and glass so that we can calculate the refractive index and make the right kind of lenses for your spectacles - we're talking about the group velocity - and we should say so - but we usually don't.
'Ether' - in this context - is correctly spelled 'aether' (and often expanded to luminiferous aether) because there is a chemical called 'ether' that is an entirely different thing! The idea that there is an 'aether' through which the waves travel is a seriously outmoded concept - the utter failure of the many efforts to detect the presence of the aether is the reason that Einstein discovered relativity in the first place.
As for "reasons"...these are always difficult for physics. We mostly deal in the "what" - not the "why" of nature. We can measure what it does - but not why it does that. So I don't think we know of a reason why there is a cosmic speed limit. If we had to say anything, it would probably be that he nature of relativity is that there is a cosmic speed limit built into the laws of nature - you can see it clearly in the equations. Light and gravity travel at that speed. We call it "the speed of light" mostly for historical reasons. In the case of light, photons (having zero rest-mass) can't help but travel that fast - if they were (hypothetically) ever to travel any slower then even an infinitesimal force would impart an infinite accelleration (because F=ma - so a=F/m - and if 'm' approaches zero and 'F' is finite - then 'a' approaches infinity). That infinite acceleration would instantly push the photon them up to the cosmic speed limit. Now - as to why there is a cosmic speed limit...that's something we don't know the answer to.
Wow Steve, that was incredibly informative. My knowledge of the subject seems to me much less definitive than I had thought. Your response leaves me wondering, though, are photons always traveling at the phase velocity? Or are they tied into the group velocity? —Akrabbimtalk12:11, 2 July 2009 (UTC)[reply]
Steve, if a change in size or frequency of light can only pass through air, water etc. at less than 'c' how can one prove that any higher velocity exists in the medium ? Cuddlyable3 (talk) 12:28, 2 July 2009 (UTC)[reply]
Steve, your response was pretty inaccurate. The phase velocity of light is not generally equal to c (the vacuum speed of light). It can be smaller or larger. It's effectively infinite for a standing wave, even in vacuum. For light in glass it's roughly the same as the group velocity (that animated image shows a gravity wave, not light, and as an illustration of group velocity it's kind of dubious anyway since there's no real wave packet). It's the phase velocity that's defined to be c/n in a refractive medium and that figures into Snell's law and lensing (see the animated image at the top of refractive index). The group velocity can also exceed c and is not the speed at which information is communicated in general. This Java applet shows how group velocity can be larger than c or negative (that is, opposite the direction of information propagation). The relationship between phase velocity, group velocity and "actual information propagation velocity" is subtle, and I think it may even be an open question. See the last part of this page, starting from "How about using tachyons to transmit information faster than the speed of light..." -- BenRG (talk) 00:52, 3 July 2009 (UTC)[reply]
Apologies: I had added the indent when I responded. Because of the date in the middle, I mistakenly thought Taxa was responding to an unsigned OP. Indent removed. Tempshill (talk) 19:27, 2 July 2009 (UTC)[reply]
A minor nitpick to Steve's answer. The phase velocity does not have to exactly equal c (the universal constant). There are plenty of materials (optical prism?) where both phase velocity and group velocity are non-constant or vary with frequency. Nimur (talk) 16:33, 2 July 2009 (UTC)[reply]
I too am wowed by Steve's answer, whether it is right or wrong. Steve's answer is still extremely informative as to how one might go about answering the question. Most important is his introduction of the relationship between force, mass and acceleration and ultimately energy, which should properly be responsible for a speed limit. The problem I have with group versus phase velocity is that if you can clip the intensity and in effect use it to propagate information then group velocity would always equal phase velocity if such a clipping could be done. Another response that comes to mind is that the limit may be simply be the limit that a magnetic field can generate an electrostatic field and vice versa as the means of propagation. This process must be very efficient and use up very little energy which may or may not support the idea of the existence of a luminiferous aether]]. --Taxa (talk) 05:02, 3 July 2009 (UTC)[reply]
As a side note, see this. It's an issue of a webcomic -- in this case atypical in comic content for this comic, but typical for interesting commentary, in this case on Maxwell's equations. -203.129.49.222 (talk) 11:32, 3 July 2009 (UTC)[reply]
Oh yeah. That fully explains it. I suppose that at some point in the transition of magnetic to electric field light would take on characteristics of a particle while in the opposite phase the characteristics of a wave? --Taxa (talk) 13:43, 3 July 2009 (UTC)[reply]
Second Generation Growth
First generation crystal right, second generation left
The owner of this crystal tells me that the first generation crystal (right) formed first. Then the second generation solution came in and formed the crystal on the left. Does wikipedia have an article on second generation crystal growth, or can anyone find a reference? This would be be a perfect illustration if I could find the article. Noodle snacks (talk) 09:38, 2 July 2009 (UTC)[reply]
Your quesstion seems to be a homework question, as do the ones below. This desk is not answering such questions per policy. Some answers might be found at Hydrogen,degeneracy, Ion, potential as well as other related Wikipedia articles. As aditional advice: The utilization of socks is frowned upon. Try to aviod making the same spelling mistake all over your questions. Its a deat giveaway. --91.6.12.225 (talk) 11:50, 2 July 2009 (UTC)[reply]
Running around acting wild and paying no heed to the expectations and norms of society. Like a semiconductor, a human can be doped into total degeneracy. Edison (talk) 23:55, 2 July 2009 (UTC)[reply]
Note that a quantum-mechanical treatment of a simple harmonic oscillator is not the same as a classical physics treatment. This example is commonly the first example worked in a quantum physics text-book. Nimur (talk) 16:35, 2 July 2009 (UTC)[reply]
I think this is described here as well: Conductivity (electrolytic) Before asking for things that could easily be found by searching, please search Wikipedia and other sources a bit, as suggested at the top of this page. If you need to ask, please keep in mind that we are all human beings, here to enjoy interaction, not automatons waiting for your command. --Scray (talk) 12:21, 2 July 2009 (UTC)[reply]
Is there a scientific reason why humans normally have 5 fingers and five toes on each limb? Why not 4 or 6? Why is 5 the magic number? 65.121.141.34 (talk) 16:29, 2 July 2009 (UTC)[reply]
Depends on what you mean by "reason." The simplest answer is that we have five digits because our ancestors had five digits (pentadactyly). Someone else might be aware of research showing why 5 is more adaptive than 4 or 6, but I wouldn't be surprised if there's no such research. Many traits are not adaptive. Adaptive or not, an expert in ontogeny could probably give you another kind of "reason," that is, exactly how our genes encode for various proteins that lead a fetus to develop five digits.
This probably doesn't answer your question, but hopefully it's something to think about pending a more complete answer from someone with more expertise. --Allen (talk) 16:57, 2 July 2009 (UTC)[reply]
Not necessarily. We can presume that it wouldn't make the body function more effectively, but that is all. --Tango (talk) 17:18, 2 July 2009 (UTC)[reply]
They can't be equally likely since one includes the other (unless it is impossible for 5 and 6 fingers to be equally effective and there is no reason to assume that). If 5 fingers was worse than 6 fingers then we would expect natural selection to select people with 6 fingers and by now we would all have 6 fingers, but if 5 and 6 fingers are equally effective then there is no selection pressure and it just gets chosen at random. So we can presume that 5 is either better than 6 or as good as 6, but we can't tell which without more research. --Tango (talk) 17:31, 2 July 2009 (UTC)[reply]
I think we are comparing 5 to any other number. Isn't that what we are really comparing? The questioner mentions both four (a lesser number) and six (a greater number). Bus stop (talk) 17:33, 2 July 2009 (UTC)[reply]
Tango, you say, "If 5 fingers was worse than 6 fingers then we would expect natural selection to select people with 6 fingers and by now we would all have 6 fingers". I don't think that's true. It might be that 6 fingers confer a very slight advantage, and that there has not been sufficient environmental pressure to make that advantage play much role in determining reproductive success. -GTBacchus(talk)17:44, 2 July 2009 (UTC)[reply]
Our ancestors have had 5 fingers for a long time, all primates have 5 fingers/toes so that means it happened at least 10s of millions of years ago. Polydactyly is fairly common (and can be inherited and, as far as I know, isn't associated with any other negative conditions), so there has been plenty of opportunity for us to evolve to have a different number of fingers. It wouldn't need to be a very large advantage to it to have happened. --Tango (talk) 21:55, 2 July 2009 (UTC)[reply]
I don't have time to do a search, so I can just try to piece together fragments from an old memory... In genetic research, the gene group that is responsible for creation of the digits (fingers and toes) are also responsible for creation of the reproductive organs. So, if there is a genetic abnormality that causes more or less digits, it is highly likely that reproduction will be hindered. Therefore, the ability to stray from five digits is limited by the ability to reproduce. What comes to mind is something like HAX or HEX or HOX. I don't actually work in genetic research. I read this while researching genetic information on the four-toed hedgehog. Does this nonsense ring a bell for anyone who actually knows about genetics? -- kainaw™18:29, 2 July 2009 (UTC)[reply]
HOX is short for homeobox and they determine all sorts of things about the arrangement of the body (eg. that your face is on the front, not the back). It wouldn't surprise me if HOX genes were responsible for the number of fingers, however I've never heard of people with Polydactyly being infertile. --Tango (talk) 22:01, 2 July 2009 (UTC)[reply]
Not the scientific answer you're looking for, I know, but I like to attack the questioner's frame of mind, not the question itself:
If we had 4 or 6, you would just as soon ask, "why not 5?". There's 5 because evidently, that's what works best. Trying to break down that 'why' into some bio-mechanical or socio-evolutionary explanation would be so lengthy and obscure that it wouldn't be worth the effort – in my opinion. Vranak (talk) 19:09, 2 July 2009 (UTC)[reply]
Fingers started as stiffeners for fish fins. The practicality of mittens shows that the number of human fingers doesn't matter much. The evolutionary step that did matter was when a primate gained an opposable thumb. Hands would no more be just for walking on, now they could be used to fruitpicking, hitchhiking and typing the spaces in Wikipedia. Cuddlyable3 (talk) 22:34, 2 July 2009 (UTC)[reply]
Could you give a few more examples of what else CRABP-II mediates besides the number of digits? I'm not a geneticist, but I'd like to know if a modified CRABP-II gene is likely to be maladaptive.
76.21.37.87 (talk) 04:12, 4 July 2009 (UTC)[reply]
In Mutants (ISBN 0006531644), Armand Marie Leroi points out that until recently all known tetrapods (i.e. land vertebrates) had no more than five digits, and those with fewer than five always had ancestors with five digits: the normal conclusion was that the common tetrapod ancestor was pentadactyl, and all subsequent tetrapods had inherited this trait, though in some cases subsequently lost digits. But the discovery of Acanthostega, Turlepreton and Ichthyostega has changed this, and it now looks as though there was considerable variation in the dactyly of early tetrapods before pentadactyly became universal.
Of course you could use this fact to argue for an adaptive advantage in no more than five digits, but I think such an argument would be weak ;) --ColinFine (talk) 16:18, 4 July 2009 (UTC)[reply]
Try this article (although it's a little old). CRABP-II is involved in neural crest development. "CRABP-II mRNA have been shown to increase in tissues and cell lines of various origins, including F9 teratocarcinoma cells, P19 embryonal carcinoma cells, adult human skin, skin fibroblasts, and lesional hyperplastic psoriatic skin following treatment with retinoic acid." Axl¤[Talk]19:57, 4 July 2009 (UTC)[reply]
To me I'm still confused. I haven't got the chance to study about special and general relativity in the university. I tried to read some books and visit such web pages as Relativity of simultaneity to understand some more. Now I need to distinguish the following:
1- Light speed is absolute: What can prove this other than Maxwell's equations?
2- Assuming 1 holds true; what makes us assume that the observer in moving frame of reference will find that light in that frame passes both (front and back) directions and reaches equal distances at the same time (So far we shouldn't conclude that time is relative till both 1 and 2 postulations are verified)?--Email4mobile (talk) 17:55, 2 July 2009 (UTC)[reply]
That the Speed of light as an absolute and unchanging quantity, independent of the speed of the observer has actually been proven experimentally, and not just via deduction. Consider the seminal work of people like the 17th century Ole Rømer. Of course, the definitive works is the Michelson–Morley experiment, which essentially disproved the idea of 'aether', and the Ives–Stilwell experiment, which showed that redshift could be accounted for only if the observed speed of light is identical looking forwards and backwards. Also see History of special relativity which explains the development of all of these ideas and more. --Jayron32.talk.contribs18:10, 2 July 2009 (UTC)[reply]
Did you read the other articles, or folow any links in the see-also sections of any of those articles? The information is here for you to find; the History of special relativity has lots of details and lots of links; also the Ives–Stilwell experiment which also explains your direct question regarding perceptions of the speed of light in a moving observer. --Jayron32.talk.contribs20:32, 3 July 2009 (UTC)[reply]
Solar Panels
If I have a solar panel operating at a certain voltage and current, and I cover part of it, what will decrease, the voltage, the current, or both? Not homework, just curious. 149.169.104.64 (talk) 18:02, 2 July 2009 (UTC)[reply]
Assuming it is a photovoltaic panel, I would think that it would directly reduce the voltage output. Depending on the load network that the panel is attached to (I have no idea how they are integrated into power grids), the current would probably be reduced as well. —Akrabbimtalk19:19, 2 July 2009 (UTC)[reply]
It's going to depend on what else is on the circuit. I don't know a whole lot about electronics, but if we assume a simple case where whatever you're powering has constant resistance R no matter what, then the voltage and current are going to stay in the ratio V/I = R. So cutting the power by half, and using P = IV, the voltage and current would both be reduced by sqrt(2). Maybe someone who knows more about this can comment on how likely that assumption is. Rckrone (talk) 23:36, 2 July 2009 (UTC)[reply]
Actually looking at Electromotive_force#Solar_cell it looks like it's a bit more complicated than I thought. The current and voltage will stay proportional for a fixed resistance, but the power isn't determined only by how much light is hitting the solar panels like I was assuming, it depends on the current, so instead of using the equation P = IV you would have to use the one listed there to figure out exactly by what factor the current and voltage would both drop. Rckrone (talk) 00:04, 3 July 2009 (UTC)[reply]
Most stars are colored red, or yellow or white because of their temperature. Are there any known green colored stars? Say one that has a lot of chlorine or copper in it? Is such a star theoretically possible, even if we don't know of a current example? 65.121.141.34 (talk) 18:16, 2 July 2009 (UTC)[reply]
I wish I could back this up better, but the gist of it is this: stars output their light in a curve, so to speak. Bright, blue stars output most of their light in the blue wavelengths, whereas red stars output most of their light in redder wavelengths. Now, a star with a peak in the green won't appear green for reasons I don't quite remember, but it had something to do with the other (bluer, IIRC) wavelengths drowning it out. So yes, there *are* green stars, but the human eye won't ever perceive them as green. Actually, here is a reference, and here's another one. I left my old text since I think it's mostly correct. ;) -- Aeluwas (talk) 19:10, 2 July 2009 (UTC)[reply]
Human color perception is a strange thing in many ways. Consider that there are actual two different "yellow" colors, which are VERY different, but which our minds cannot distinguish between. One is a single wavelength color consiting of pure yellow light, and the other is a mixture of two wavelengths of light, one red and one green. The human mind only sees these as the same color, though one is clearly a primary color, and one is a secondary color. There are LOTS of colors that work this way. See Color vision for more on how we perceive color. --Jayron32.talk.contribs20:52, 2 July 2009 (UTC)[reply]
How do you define the colour of a star apart from what colour it appears to humans? Those are the only real definitions of colours we have (except for monochromatic colours that can be defined by their wavelengths). --Tango (talk) 21:46, 2 July 2009 (UTC)[reply]
Except for absorption lines whose effect is relatively minor, stars emit blackbody radiation, which is spread over a quite broad range of wavelengths. For cooler stars, most of their output is in the infrared region, so we can only see the top of their spectrum which is red; for hottes stars, it's mostly ultraviolet, so we can only see the blue part. Stars with intermediate temperature emit over the whole visible spectrum, so they are white. Black bodies can only have colors on the Planckian locus; so there can be no green or purple star. --A. di M. (formerly Army1987) — Deeds, not words. 21:42, 2 July 2009 (UTC)[reply]
Interesting fact: our Sun is a "green" star because its spectrum peaks in the green, or at least very close to it. Not surprisingly, the human eye's sensitivity peaks around the same wavelength, but why leaves reflect green light most strongly is a bit harder to explain. --Bowlhover (talk) 23:31, 2 July 2009 (UTC)[reply]
Insect identification
This morning I found these on my front gate; I've never seen anything like them before, and was wondering if anyone could identify? I'm assuming they're moths, and they're mating (?), but beyond that I'm lost. I'm in Belfast, Northern Ireland where I found these guys about 8am. Unfortunately I wasn't able to line anything up for size comparison, but the body length was approx 1.5 inches and 2 inches from wingtip to wingtip. Are they mating? They don't exactly look like the same species - are males and females often significantly different in appearance? Thanks --Kateshortforbob22:14, 2 July 2009 (UTC)[reply]
I think the species is Poplar hawk-moth, Laothoe populi. So, yes, they are moths; and yes, they are mating. Regarding the appearance - I need to look it up. I've seen both grey and brown form in the photographs, but I do not remember if it is sexual dimorphism or just different color forms. --Dr Dima (talk) 22:24, 2 July 2009 (UTC)[reply]
You should replace the current 'mating' photo with this one and explain the color difference in the caption. It's a prettier photo than the current one. Tempshill (talk) 23:15, 2 July 2009 (UTC)[reply]
Thanks Dr Dima, for the identification - I will update the description page accordingly. Thanks also, Jayron32, for adding the picture to those articles - I suspect I would have committed some embarrassing captioning error if I did it myself! --Kateshortforbob10:28, 4 July 2009 (UTC)[reply]
Many animals, such as cows, have a long tongue which is easy for them to stick up into the nostrils for cleaning purposes. It would be difficult for a cow to pick her nose with her hoof. Edison (talk) 02:27, 3 July 2009 (UTC)[reply]
I've seen chimps and gorillas doing it - and it has been observed (sorry - I can't locate the link) that in many (if not all) primates, the nostrils are the exact same diameter as the index finger. This is unlikely to be an accident. SteveBaker (talk) 14:26, 3 July 2009 (UTC)[reply]
@Tempshill: I don't think that's correct, if you're using "Darwin" as a representative of adherents to evolutionary theory. Just to reduce the risk of confusion, I'm going to hazard a guess: "accident" is being used here (by both SteveBaker and Tempshill) to mean "coincidence" or random chance. Though evolution depends on random variation to generate diversity, it is selection that drives adaptation to specific function (which I think was the point SteveBaker was making). --Scray (talk) 19:49, 3 July 2009 (UTC)[reply]
I think SteveBaker used "accident" in the latter sense, and I was using it in the former sense. I don't know that I'd subscribe to the theory that human finger diameter and human nostril diameter have been selected to match each other. Tempshill (talk) 20:39, 3 July 2009 (UTC)[reply]
There's nothing very mysterious about it. If we ignore the obfuscating steps that don't involve your number at all, and rearrange the initial grid a bit, then it boils down to being given a 5x5 grid of numbers, choosing one of them, telling someone which row and which column your number is in, and them then working out your number. Algebraist04:01, 3 July 2009 (UTC)[reply]
It looks very simple once you take away all the pointless stuff. First, it asks you the color. That narrows it down to only 4 or 5 numbers. Then, on the step with the houses, the numbers for the colors are split up so that each house contains only one number of each color. Knowing the color from before, that leaves only one possible number. Ta da! --Bennybp (talk) 04:51, 3 July 2009 (UTC)[reply]
light propogaton versus particle stability
Is perhaps the only difference between light (as a particle) and other particles is that light is self propagating perhaps due to an inability to become a stable particle whereas other particles are either stable or their instability does not cause self-propagation but self-inhalation instead? --Taxa (talk) 05:18, 3 July 2009 (UTC)[reply]
I would advise you to read the article photon. Photons are pretty stable, you can see them around everywhere. I don't understand what you mean by "self-inhalation", or how you propose that a particle can "self-propagate" if it is unstable. Maybe you mean "annihilation" but that requires two particles - one matter and one which is antimatter. Rkr1991 (talk) 06:36, 3 July 2009 (UTC)[reply]
Typing "pocket desert" into Google turns up articles about a specific place near Oliver, British Columbia. Our article describes it as having a 'pocket desert' nearby. This has more information, as does this. So the term seems to be a generic one for multiple 'pocket deserts' - yet only this specific one ever shows up as an example of such a thing. Perhaps the term is used only in Canada with some other terminology being used elsewhere? SteveBaker (talk) 14:22, 3 July 2009 (UTC)[reply]
Searching on "desert pocket", found quite a lot of examples describing areas of local desert conditions as suggested by 194, mainly from the US but also from New Zealand and the Himalayas (cold desert in that case). Mikenorton (talk) 15:32, 3 July 2009 (UTC)[reply]
I'm aware of small areas of desert near Lillooet, British Columbia, could it be the same "pocket desert" Steve found on Google?
What are the strongest and weakest points of gravity on earth?
I'm aware that a number of 'gravitational maps' exist, however, I have heard, in the past, of a place where the phenomena of gravity is noticeably at variance with that of other parts of the world. Where are these places and what, if any, explanation exists for the variance? —Preceding unsigned comment added by 24.234.123.169 (talk) 16:53, 3 July 2009 (UTC)[reply]
Our article Gravity anomaly gives the facts, in a sketchy way. It's possible that you're thinking of stories about places like Confusion Hill in northern California, where the layout of the landscape creates an illusion that objects roll uphill. Looie496 (talk) 17:05, 3 July 2009 (UTC)[reply]
Due to the shape of the earth, gravity will tend to be strongest at the north and south poles - and weakest around the equator (the earth isn't a perfect sphere). However, you don't feel that difference because the centrifugal forces are zero at the poles and higher at the equator...which is why the earth is that shape to start with and gravity-centrifugal force is pretty much constant everywhere. Aside from that, differences in mineral composition and therefore density can make a tiny difference from place to place - also the presence of mountains or deep valleys. This map [12] gives you a better way to visualise it. ~~
Actually, the effects of oblateness and rotation act in the same direction, both reducing the effective acceleration due to gravity at the equator as compared to at the poles. The difference is about 0.35%, of which about 2/3 is due to the rotation of the Earth and 1/3 is due to the oblateness of the Earth. Definitely a noticeable effect - a pendulum clock on the equator loses about 2.5 minutes a day compared to an identical clock at the poles. See Equatorial bulge#Differences in gravitational acceleration. Gandalf61 (talk) 19:38, 3 July 2009 (UTC)[reply]
The story that I heard, was that there was a place where gravity or some other phenomena affected the surface of a lake in Africa. The phenomena supposedly caused the surface to have a noticeable curvature. However, I suppose that this is a legend or myth of some sort.
As I recall, there's a memorial pool in Boston or Philly which is kept so full of water that it had to be slightly curved to match the Earth's curvature, or else water would spill around the edges. It's huge, but I can't remember the name... Andyo2000 (talk) 18:54, 9 July 2009 (UTC)[reply]
Gravity would be lower on the peaks of tall mountains as there is a higher radius from the center of the earth if you are going with a standard physics textbook. 65.121.141.34 (talk) 15:05, 6 July 2009 (UTC)[reply]
At what speed do galaxies travel through the universe/space?
At what speed do galaxies such as the Milky Way and Andromeda travel through space? As a follow-up, what are the speeds of the solar system and earth as well? How are these measured? How does this affect our measurements such as the speed of light, radio waves, etc. Is there a point where the speed of a mass shall decline to 'absolute 0'? Theoretically, is there a way to 'see' a mass traveling faster than the speed of light? —Preceding unsigned comment added by 24.234.123.169 (talk) 17:38, 3 July 2009 (UTC)[reply]
As it turns out, the speed of light relative to you will be equal regardless of how fast you're moving. Check out Special_relativity#Lack_of_an_absolute_reference_frame and also Introduction to special relativity. As a result, measurement of the speed of light is not affected by how the earth or the galaxy are moving, and an object can never be observed to travel faster than light. In addition, objects don't have a meaningful absolute velocity since there's no single "preferred" reference frame in which light behave properly; you can only talk about objects' velocities relative to other objects. Here's some info on the Milky Way: Milky_way#Velocity. Rckrone (talk) 18:34, 3 July 2009 (UTC)[reply]
Hi everyone I recently bought a wetsuit made of neoprene and on the label it says do not use in chlorinated water. I intended to use it in chlorinated water. I am wondering if I do go in chlorinated water in this suit will it affect the insulating properties of the material? If chlorine only acts to discolourise/stain the material I don't much care but I want to make sure that going in chlorinated water won't stop the suit doing its job if you know what I mean. Any help would be much appreiciated. Thanks RichYPE (talk) 17:53, 3 July 2009 (UTC)[reply]
I was taught, vaguely, that chlorine would somehow destroy the wetsuit. Googling "neoprene chlorine", this result from the first page of results claims that "Neoprene ... contain[s] carbon-carbon double bonds as an essential part of their polymer chains. These bonds are susceptible to oxidative damage from species such as ozone and chlorine." As a layman I'm not exactly sure what "oxidative damage" means, but it sounds like it'd be worse than just staining. Tempshill (talk) 20:10, 3 July 2009 (UTC)[reply]
Thanks for your help but chlorinated water is usually in the form of sodium hypochlorite rather than just actual chlorine. I wonder if this makes a difference and whether or not this would react with the neoprene... RichYPE (talk) 22:17, 3 July 2009 (UTC)[reply]
Actually, read the article Bleach. Hypochlorite is really a dynamic equilibrium with chlorine and water, as described here:
Cl2 + H2O H+ + Cl- + HClO
With low pH favoring the backwards reaction and high pH favoring the forwards reaction. Still, even under roughly neutral conditions, there may very well be enough Cl2 present to react with any double bonds via alkene halogenation mechanisms; even if its only a trace amount, Le Chatelier's principle tells us that since the reaction removes chlorine from the system, the hypochlorite-chlorine equilibrium will just generate more chlorine on demand to meet the need. I did some looking, and there does not appear to be any common hypochlorite-alkene reactions directly; however the chlorine is clearly the reactive species here. --Jayron32.talk.contribs00:39, 4 July 2009 (UTC)[reply]
As far as I'm aware, the chlorine addition reaction will not destroy neoprene rubber, but is likely to cause embrittlement over an extended period of time. So, if you frequently use the wetsuit in chlorinated water, it won't come apart the first few times, but you should definitely expect it to wear out sooner than normal.
76.21.37.87 (talk) 04:29, 4 July 2009 (UTC)[reply]
Hi thanks for the posts guys. What I will do is get a refund on my suit (still have receipt) and buy one which is chlorine resistant. Cheers RichYPE (talk) 19:05, 4 July 2009 (UTC)[reply]
I have been a SCUBA instructor for quite some years,+- 14 Years. We used the local comunity pool as an inland training facilety. The pool water was well clorinated and sometimes to the extend that it could be smelled from outside the water. The cloranation time was more or less the same time as the training schedule. I can realy not say that my wetsuites was damaged in any way other than some fading of the colours and even this was minor. Take note however that we washed and rinsed oue suites well after use in clean fresh water and did not dry them in direct sunlight. My old "outsized suites" was passed on to other guy's and are still in use. 196.25.43.75 (talk) 13:34, 9 July 2009 (UTC)[reply]
Minimum Sample Size for a Correlation Study
I know of a formular for determining the minimum sample size for a prevalence study, which most research studies use. Is there any formular to determine minimum sample size for a correlation study, like a correlation between birth weight and fetal cord leptin concentration-a research?Tunmisadej (talk) 19:54, 3 July 2009 (UTC)[reply]
I'm not sure there is a general answer to this. For a specified minimum confidence level and correlation value, one can determine the number of samples needed, but since it depends on the strength of the correlation one may not have a good estimate in advance. For example, a perfect correlation can be statistically significant with only a small number of samples. By contrast, a weak correlation (which is much more common in practice), may require a quite large sample to confidently document. Dragons flight (talk) 20:11, 3 July 2009 (UTC)[reply]
I am sorry, I still find the reference above not clear to answer the question. The one that was mostly discussed was sample size for determining proportion study. If I have correlation coefficients from prevoius research studies, I would like to know if this can help in determining minimum sample size using any formula or otherwiseTunmisadej (talk) 11:30, 4 July 2009 (UTC).[reply]
Which obeys the student's t-distribution characterized by ν = N-2. Using this one can determine the two-tailed probability of r occurring by chance amongst N samples. Most people use a table because the math is messy. To answer your question simply vary N for fixed r and use the table to figure out when the resulting t is associated with the level of confidence you want. Again, since all the factors are interdependent the sample size will dependent strongly on the strength of the relationship, which is general is difficult to know confidently in advance of doing the experiment. Dragons flight (talk) 08:08, 5 July 2009 (UTC)[reply]
I am very grateful to Dragons flight, the idea is quite useful. I was trying to have a scientific proof for my sample size in a correlation study.41.219.230.122 (talk) 18:55, 5 July 2009 (UTC)[reply]
Blood pressure in cats
Our vet always quotes our cat's blood pressure as a single number whereas human blood pressure is always quoted as two numbers, the systolic and diastolic pressures. Why is only one quoted for cats and which one is it (or is it some other number entirely)? Thanks. --Tango (talk) 22:27, 3 July 2009 (UTC)[reply]
The information on this site (http://www.pets.ca/encyclopedia/hypertension_cats.htm) has some details under the 'diagnosis' section and seems to suggest both types of numbers being run against cats. Are these measured separately or together? If they are separate then maybe it is to minimize stress on the animal and perhaps the single piece of information is usually enough. All speculation though, sorry. ny156uk (talk) 23:12, 3 July 2009 (UTC)[reply]
I think you have to ask your vet on this one: it's certainly possible to obtain the usual systolic/diastolic readings in cats (normal is ~124/82) using a machine (I think the cat's rapid heartbeat might make it difficult to do by ear). But whether your particular vet is quoting systolic, diastolic, or mean arterial pressure is something only he or she can say. - Nunh-huh23:16, 3 July 2009 (UTC)[reply]
July 4
what sort of atomic radius is this?
If I take a mole of some element, measure its volume, then divide by 6.024 * 10^23, and then find the radius of the sphere with that volume, what am I measuring? Van der waals radius? —Preceding unsigned comment added by Em3ryguy (talk • contribs) 01:16, 4 July 2009 (UTC)[reply]
I'm not sure you are measuring anything useful. Any substance is going to have a space between its atoms in any phase of matter; your calculation includes this extra-atomic space as part of the radius of the atom itself. Even assuming you had a perfect crystal at absolute zero (which is an impossible to reach state), you still have to consider packing efficiency. In any real solid, the atoms are going to still obey kinetic molecular theory in that they will vibrate in place; and this motion will also add volume to the theoretical perfect packing required for your calculation to work. See Van der Waals radius#Methods of determination for real experiments used to calculate the Van der Waals radius. I am pretty certain that most modern chemists would use X-ray crystallography to find such values today. Also, the Van der Waals radius is something of a meaningless curiosity. It supposes that atoms are hard spheres; they are not, and do not behave as such under any conditions where their radius is likely to be important. --Jayron32.talk.contribs01:28, 4 July 2009 (UTC)[reply]
Useful or not, though, there is a technical term for this radius: mean interatomic spacing, or crystal lattice atomic spacing (depending on the type of matter, you might or might not have a crystal lattice). Take a look at this material science textbook, for example. Nimur (talk) 04:00, 4 July 2009 (UTC)[reply]
The real reason the most shell fish should be kept live until cooking
I'd like to read a accurate and somewhat scientific description of the reason that most shellfish are kept alive until cooking. I haven't been able to find much on or off Wikipedia. ike9898 (talk) 01:26, 4 July 2009 (UTC)[reply]
No, it's a good question from the OP because other dead animals we eat aren't kept alive until throwing them into the cooking pot. Tempshill (talk) 04:27, 4 July 2009 (UTC)[reply]
Shellfish are kept alive until cooking because there is often no way to distinguish between a recently dead shellfish and a long-dead shellfish. This is especially true of true shellfish like clams and oysters; you generally only can tell if its good to eat if it hasn't rotted, and the only way to tell if it hasn't rotted is to ensure its still alive when you cook it. Most live shellfish ship pretty well on ice, which is why you can get live clams pretty much anywhere (for the right price). Heck, I've seen them in seafood markets in Chicago, which is 1000 miles from an ocean. Crustaceans, which often get classed as shellfish, (though they really aren't), like shrimp, prawn, lobster, and crab are probably safe to eat if frozen alive; in fact lots of shrimp is handled that way. Lobster, on the other hand, is not generally cheaper to ship frozen than alive; unlike shrimp, lobster can survive for a long time out of water, and can survive in a "dormant" state if kept on ice, like dry ice, which is why live lobsters can be shipped to many parts of the country. Crabs are usually cooked and packaged on the boat, in the case of snow crabs or king crabs, which are the kinds of crab you get when you get those crab legs on the chinese buffet. Other types of crab, such as dungeness crab or blue crab are usually only availible dockside. Live crabs are cooked to consume at the restaurant, or cooked and picked and shipped in the form of "lump crabmeat". Unless you are at the shore, you are not going to be able to get raw or fresh crab to cook. --Jayron32.talk.contribs18:13, 4 July 2009 (UTC)[reply]
Original poster here I'm afraid everyone who's answered so far doesn't know much more than I do, and I really think that there is more to it than what has been mentioned so far. I have seen some (unreliable) sources explain that it has something to do with autolytic enzymes that are released when the animal dies which break down the tissue rapidly. I also think I've heard about some serious food safety concerns. Anybody else have input? ike9898 (talk) 01:13, 5 July 2009 (UTC)[reply]
I think Shantavira, Edison and Jayron32 have a bit of a point. In particular, most seafood including fish generally has to be fresh and is usually cooked within a day or two of cathing or frozen or otherwise prepared. You do get live fish in restaurants, but for home use, carrying and storing live fish is impractical but live shellfish is usually not. Shellfish may be somewhat worse then fish (I see suggestions they should be cooked within a few hours) so this may not entirely answer the question but I think it's getting there. The fresh is best mantra is of course a common view, and it's not uncommon for there to be live chickens in wet markets but I'm not entirely sure if many people would actually want to eat a beef from a cow slaughtered a few hours ago. Nil Einne (talk) 12:42, 5 July 2009 (UTC)[reply]
I don't think your statement about live crabs is entirely accurate. It depends where you live. It's not that hard to buy live crabs in Kuala Lumpur or other areas of the Klang Valley for example which is not that close to the shore [14]. This is probably true in most largish Malaysian cities even ones that are further from the shore (although given its geography, most Malaysian cities aren't that far from the shore). I tried to find evidence for live crabs from Ipoh which is probably further from the shore but couldn't find definite evidence other then from restaurants. It's probably not as easy nowadays as it was in the past given the changing demands, the growth of supermarkets and hypermarkets and the lower popularity of wet markets but I still think it's likely not that hard. And as mentioned in the thread, they may be available in supermarkets and hypermarkets in Malaysia, like Carrefour sometimes. I suspect this is the same in many parts of South East Asia and even more so in East Asia. E.g. this [15] is supposedly in Walmart in China although which Walmart isn't specified... In other words, it depends a lot on the local preference, market and demand. N.B. live fish are quite common in most Malaysian restaurants including cheap coffee shop ones. Nil Einne (talk) 12:28, 5 July 2009 (UTC)[reply]
@Jayron ... frozen alive; in fact lots of shrimp is handled that way ... Don't know about your shriping boats, but most of the ones I've seen tossed them into boiling water before they got frozen/ stored on ice.71.236.26.74 (talk) 14:31, 5 July 2009 (UTC)[reply]
Many are, but many are not. Because of their fiddly size, ease of spoil, and relative expense, shrimps are processed right on the boat and the processing may be in a number of ways. Besides size sorting, the shrimp may be cooked or not, de-"vein"ed or not, have the tail removed or not, and have the head removed or not. The stuff you find at the local mega-mart is most likely to be cooked because most people aren't interested in doing that part themselves, but the product shipped to restaurants would more likely be in the raw state. Matt Deres (talk) 23:33, 5 July 2009 (UTC)[reply]
It happened to me at one era in my life right after breakfast, otherwise not for many years. It was as automatic as putting a coin in a gumball machine. Edison (talk) 03:38, 4 July 2009 (UTC)[reply]
Is enquiring about trends in normal bodily functions seeking a medical dignosis? Do most people dump shortly after a meal? Thats all I want to know. Its not medical its statistical. —Preceding unsigned comment added by 79.75.91.172 (talk) 09:57, 4 July 2009 (UTC)[reply]
Seeking a medical diagnosis for a perfectly normal and widespread phenomenon? Have you looked at Gastrocolic reflex it should answer your question and confirm the normality of the action. It happens to a lot of people, particularly after the first meal of the day. Richard Avery (talk) 10:01, 4 July 2009 (UTC)[reply]
From Wikipedia, the free encyclopedia, quote: "The X-ray background is occulted by the dark side of the Moon." Is this true? How could it be? Please explain. And, please do make sure, when you replying, you actually do understand that "dark side of the Moon" do not actually refer to the "far side of the Moon". Another quotation: "The far side [of the Moon] should not be confused with the "dark side" (the hemisphere that is not illuminated by the Sun at a given point in time), as the two are the same only during a full moon. ". Vitall (talk) 03:14, 4 July 2009 (UTC)[reply]
Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. — Preceding unsigned comment added by SteveBaker (talk • contribs)
What lead you to believe that question asking if Wikipedia article statement is true/correct could be homework question??? And, that is unrelated, but where in the world topic of X-ray background radiation are taught in schools? Vitall (talk) 03:58, 4 July 2009 (UTC)[reply]
An edit earlier today changed the link in the article so that it pointed to Far side of the moon, which created an incorrect statement. I've reverted that edit. For an explanation of how the dark (unlit) side of the moon appears to occult the background radiation, see the description for File:Moon in x-rays.gif. Actually, the entire Moon occults the x-ray background, but in that image x-rays generated by the sun are reflected from the lit portion of the Moon's surface. 152.16.59.190 (talk) 03:37, 4 July 2009 (UTC)[reply]
the entire Moon occults the x-ray background <--- I fully agree with THAT statement. Sort of obvious. So do Sun, Mercury, Venus etc. occults the x-ray background radiation. And, so there is absolutely no need to keep designated Moon statement in X-ray astronomy and X-ray background articles??? And no need to emphasize dark side of the Moon? Vitall (talk) 04:08, 4 July 2009 (UTC)[reply]
That was also part of the question. When I was reading X-ray astronomy, I came across statement that "observed X-ray background is occulted by the dark side of the Moon." It sort of throw me away - in what sense? "Occulted" just like "covered", "hid"? Or Wikipedia meant something different? And why only dark side? And if that radiation is observed, how could it be "occulted", etc. Vitall (talk) 04:46, 4 July 2009 (UTC)[reply]
"Occult" means hidden. Astronomers use the term "occlusion" to denote the covering, or hiding, of one phenomenon by another. So to say that the moon occults the X-ray background is technically correct, although it differs from popular usage of the term. Maybe a better term to use in this case would be "occluded" rather than "occulted".--TammyMoet (talk) 08:44, 4 July 2009 (UTC)[reply]
OCCULT verb: become concealed or hidden from view or have its light extinguished, cause an eclipse of (a celestial body) by intervention[16]. Etymology: From 1533, "secret, not divulged," from Latin occultus "hidden, concealed, secret," past participle of occulere "cover over, conceal," from ob "over" + a verb related to celare "to hide," from Proto-Indo-European base *kel- (see cell). Meaning "not apprehended by the mind, beyond the range of understanding" is from 1545. The association with the supernatural sciences (magic, alchemy, astrology, etc.) dates from 1633[17]a century later. Cuddlyable3 (talk) 15:03, 4 July 2009 (UTC)[reply]
Spoiled food is not only unhealthy because of the presence of bacteria or other microorganisms. These organisms have chemically changed the food (e.g. by breaking down proteins; consuming starches and sugars; potentially producing waste toxins, etc.). Nimur (talk) 04:08, 4 July 2009 (UTC)[reply]
Some bacteria and fungi produce toxins as a byproduct of metabolism Even if you kill the pathogen later by cooking, the toxin is still there. See botulism as an example. Our article on Foodborne illness describes this quite well. For your second question, remember the fungi are as different from each other as plants are. Some are beneficial, some are innocous, and some are deadly. -Arch dude (talk) 12:24, 4 July 2009 (UTC)[reply]
Mushrooms are fungi and classified as vegetables, but that doesn't make all mushrooms edible, either. Many species are extremely toxic or psychoactive. There are some fungi that are not mushrooms but still edible, for example the Judas' ear or snow fungus, but I'm not sure what food group they would belong in. ~AH1(TCU)23:53, 4 July 2009 (UTC)[reply]
To expand on Axl and the U.S. government; fruits and vegetables are not culinarily exclusive categories; there is some overlap. Botanically speaking, a fruit is any seed-bearing body in a plant. Culinarily speaking, a vegetable is any part of a plant which is used in cooking for savory applications. Thus, there are lots of fruits which are used as vegetables. Consider not only tomatos, but also the entire family of squash and eggplants and cucumber and lots of other fruits which are used in savory cooking applications. There are even a few plants which, while techinically not "fruit", take on fruit-like applications in cooking, such as rhubarb. --Jayron32.talk.contribs12:40, 4 July 2009 (UTC)[reply]
Well, except that chefs and taxonomists don't necessarily consult each other when working these things out. From a culinary point of view, something you eat is either a "Plant" or an "Animal". That's it. That Linnean taxonomy has changed over the past 100 years to remove fungi from the "plant" kingdom where they were formerly classified, and moved them to their own kingdom on co-equal footing with plants doesn't matter much to cooks. They still use mushrooms in the same manner in cooking as they always have. And they are used as vegetables. --Jayron32.talk.contribs19:22, 4 July 2009 (UTC)[reply]
All these words are informal. Biologically, mushrooms are not even plants -- they are thought to be more closely related to animals, in fact. Looie496 (talk) 18:37, 4 July 2009 (UTC)[reply]
To answer Lowellian: Since humans can survive on a diet that contains very little if any plants (as e.g. in the original life style of Inuit or Mongols), I don't think adding mushrooms will hurt. Fruit and vegetables are a very good and convenient source for many nutrients, but not the only one. --Stephan Schulz (talk) 19:02, 4 July 2009 (UTC)[reply]
Hmmm. This depends on the role fruit and vegetables play in the diet. If you follow modern recommended dietary standards (as in the food pyramid) and replace all fruit and vegetables with mushrooms, then I suspect you will miss some essential nutrients. But I also suspect the same is true if you replace everything with spinach... --Stephan Schulz (talk) 07:24, 5 July 2009 (UTC)[reply]
Not quite true, it would just involve quite a bit of food chemistry. In the days before the internet there was a study (NASA?) that said humans could live on vats of fungi and algae if an adequate number of varieties were selected and chemical reformulation was employed to produce those chemicals that could not be harvested directly. 71.236.26.74 (talk) 08:23, 5 July 2009 (UTC)[reply]
I think it's questionable if you really need milk or meat if you have a well chosen diet. Also bread and other grain/s /products, while not usually considered vegetables or fruits, do come from plant sources. And some fungi are more suitable meat substitutes (being high in mycoprotein) then fruit/vegetable. E.g. Quorn is made primarily from fungi and some single cell protein proposals are primarily fungi Nil Einne (talk) 21:18, 5 July 2009 (UTC)[reply]
Viewing solar eclipse
With a solar eclipse coming on the 22nd of this month I wanted to ask what precautions I must take while viewing the eclipse (i.e. wear sunglasses etc.). And will it be visible here in Pakistan? Thanks. —Preceding unsigned comment added by 116.71.61.65 (talk) 06:06, 4 July 2009 (UTC)[reply]
See same question (Archives June 26 "Solar eclipse") > no. 14 welder's glass/goggles are safe and should be available in Pakistan. Don't use any lower grade though. 71.236.26.74 (talk) 15:26, 4 July 2009 (UTC)[reply]
This map shows the local circumstances of the eclipse; you can click on your location to view these. The total part of the eclipse will not be visible in Pakistan, but the partial phases can be seen close to sunrise in the early morning. The "magnitude" tells you how much of the sun is being covered (multiply the number by 100 for the percentage). ~AH1(TCU)23:38, 4 July 2009 (UTC)[reply]
Physics questions
My science textbook sucks, and I have some questions about motion (Note: please don't oversimplify anything):
When I lift an object, I'm converting some form of energy inside me into kinetic energy (to lift the object) and then to gravitational potential energy. When I drop the object, the energy is converted back into kinetic energy. Once the object hits the ground, where has the energy gone? There's no kinetic energy.
My textbook states "... when he [a weightlifter] holds the barbell above his head, no work is being done on the barbell. The weightlifter is applying an upward force equal to the weight of the barbell, but there is no movement in the direction of the upward force." This doesn't sound right - surely work is being done to counteract gravity and prevent the barbell from falling?
If I hit a very small brick with a very large force (sideways, so the brick may move), my hand will hurt because of Newton's 3rd law. If I hit a brick wall (made of the same material) with the same force, will my hand hurt the same amount?
states that objects at rest have energy. The Energy article states that energy is "the amount of work that can be performed by a force", but the energy of an object at rest can't be used by any force, can it?
A1. The answer is that when you drop the object down, either it bounces back up again if its something like a ball, or it makes a big sound. It scatters all the air and dust particles in the area and slightly heats up the ground. The energy is dissipated in doing all these small small tings.
A2. Somebody owes Steve a dollar. Well, you're confusing force with energy. The weightlifter needs to keep supplying force in order to counter gravity, but he does no work, and ideally, spends no energy, keeping it up. Work is force times displacement. Since he just has to hold the weight in place, he doesn't do any work.
Give the poor sweating weightlifter a rest and replace him with a six-foot-tall rack to hold the barbell. Does the rack doo work? No. -Arch dude (talk) 12:12, 4 July 2009 (UTC)[reply]
A3. Yes, your hand will hurt the same amount. The thing is, it is easy for us to give more force to a stationary brick wall than a movable brick, because it just, well, moves away. However, for equal impulsive forces, you will hurt the same.
The physics of injury is complicated, so we cannot give a real-world answer. But a simplified answer is that hitting the wall will hurt more, because the "hurt" depends on how much ofhe energy of teh blow is absorbed by the hand. when the brick can move, much of he energey is converted into kinetic energy in the brick, while the rest is absorbed as pressure waves in the hand and the brik, withthe pressure waves eventually dissipating as heat. With the wall, none of he energy is converted to kinetic energy, so more of it is availble to hurt your hand. -Arch dude (talk) 12:12, 4 July 2009 (UTC)[reply]
A4. Read Nuclear Energy. That is the very same energy which can be used to blow up a city.
E=MC2 operates when mass is converted to energy, typically in a nuclear reaction. This is separate from any kinetic energy or gravitational potential energy. However, there is no feasible way to convert ordinary mass conpletely into energy. We know how to convert a tiny percentage of some kinds of mass into energy, as in a nuclear reactor or a thermonuclear detonation. -Arch dude (talk) 12:12, 4 July 2009 (UTC)[reply]
"there is no feasible way to convert ordinary mass completely into energy"... what about matter-antimatter collisions? It's feasible (though fortunately not easy, given the relative lack of abundance of antimatter). --98.217.14.211 (talk) 13:03, 4 July 2009 (UTC)[reply]
Thanks for the answers. I'm still confused about No. 2. Doesn't the weightlifter use energy to exert a force? After all, if I push against a wall I'm using energy to exert a force against the wall even though it's not moving... Where does that energy go? --wj32t/c08:48, 4 July 2009 (UTC)[reply]
Exerting a stationary force does not use energy, and a stationary force does no work. The barbell could be supported at the same height on a pillar or by hanging it from the roof - no energy is used by the pillar or the cable. You could lean a heavy object against the wall - again, stationary force, no work done on the wall, no energy being used. Your body uses energy all the time, to keep your heart beating, your lungs breathing and to keep you warm. Sometimes some of this energy might do external work - when you are lifting a weight, or pushing a moving object, for example. But all the energy used by the stationary weightlifter or the stationary wall pusher is wasted as heat - none of it does external work.
For extra credits, analyse the energy and work in a frame of reference in which the weightlifter or wallpusher are not stationary - put the weightlifter in a lift moving vertically at constant speed, and put the wall and wallpusher on a train travelling on a straight track at a constant speed. Gandalf61 (talk) 09:07, 4 July 2009 (UTC)[reply]
Just to add to what Gandalf said, when a weightlifter holds a dumbbell in the air, he is not doing work in the scientific sense of the term. It may look as if he is, with all the sweating and gurning, but muscular effort is not the same as work. Muscles are designed to be most efficient for running and throwing, and other dynamic activities. Under those conditions, the force they exert is cyclic, so they get a chance to recover between contractions. They are not designed for exerting large forces over long periods of time. From what I can gather from a quick look at muscular contraction, a muscle fibre contracts when it receives a command, and then starts to relax whether you want it to or not. The biochemistry of muscle fibres means that they cannot stay contracted indefinitely. If you tell a muscle to exert a constant force, what actually happens is your nervous system triggers one bunch of muscle fibres; and then, when they get tired, it triggers another bunch. Eventually it runs out of fresh fibres and has to start re-using the first bunch again. This is why muscles twitch under these conditions. The muscle is thus consuming chemical energy all the time just to stay in one place. --Heron (talk) 10:13, 4 July 2009 (UTC)[reply]
I disagree with Rkr1991's answer to question three. Try punching a punching bag as hard as you can. Your hand might sting a little. Now try punching a brick wall as hard as you can. [Medical advice: don't actually try that.] In both cases, the change in momentum (impulse) is the same. The movement of the punching bag allows the impulse to be applied over a longer period of time, which means that the maximum force applied is lower. It's the maximum force that determines the pain (and severity of injury). In your scenario where the small brick moves, the impulse is applied over a longer time period. Axl ¤ [Talk]11:32, 4 July 2009 (UTC)[reply]
By impulsive force, I mean a large force applied over a very short period of time. Punching the punching bag increases the time of application of force, because it deforms, or as I said, moves away. So, it doesn't hurt as much. I stand by my statement. Rkr1991 (talk) 12:42, 4 July 2009 (UTC)[reply]
We may never be able to exert the ideal impulsive force, but the closer we get to it, the more it hurts is my point. A shorter sharper strike is more painful on the hand than a longer drawn out strike. Rkr1991 (talk) 04:51, 5 July 2009 (UTC)[reply]
If you are given only the color of parasols, which is more likely to keep you cooler, black or white one? I think black color absorb more light (at least in the range of visible frequency), so it tends to keep you less cool than white one.
Like sushi (talk) 07:53, 4 July 2009 (UTC)[reply]
No, this is wrong. Visible light will indeed warm you unless you are a perfect mirror. Where else would the energy go? Or why would a monochromatic laser in the visible be able to burn holes through some material (including "you" ;-)? --Stephan Schulz (talk) 11:38, 4 July 2009 (UTC)[reply]
The human body preferentially absorbs infra red. It penetrates to a couple of inches into the body. Other wavelengths do not penetrate and therefore are not absorbed. —Preceding unsigned comment added by 79.75.115.133 (talk) 22:37, 4 July 2009 (UTC)[reply]
It's correct that infrared is absorbed quite well. But it is not correct that other wavelength "do not penetrate" and therefore "are not absorbed". Hold a strongish flashlight up against your hand in the dark to see visible light partially penetrating through a part of your body. And even if a given wavelength is only absorbed on the surface, it will still heat the body. Light does not penetrate most metals (due to the electrons ability to interact with nearly all photons), but an iron skillet in the sun will still heat up. --Stephan Schulz (talk) 23:09, 4 July 2009 (UTC)[reply]
As far as I understand it, light colours reflect more light and tend to keep you cooler if you are wearing them? The opacity of the material may also be a factor. Exxolon (talk) 12:23, 4 July 2009 (UTC)[reply]
Would a two-tone parasol that is white (or even better: aluminised shiny) on the top and black on the inside surface keep one coolest? It could be made reversible for use as a warming umbrella in Winter. Cuddlyable3 (talk) 14:30, 4 July 2009 (UTC)[reply]
This general question came up some time ago, in the guise of whether light or dark clothing keeps you cooler. As I recall, there were arguments in both directions, and it was never really solidly resolved. Looie496 (talk) 16:44, 4 July 2009 (UTC)[reply]
I think black on the bottom has pros and cons. On the one hand radiation reflecting up against the bottom won't reflect back down and hit you, but it's not as if that energy just disappears. The parasol will convert it to heat, some of which will reach you anyway by conduction through the air and radiation. Rckrone (talk) 18:05, 4 July 2009 (UTC)[reply]
I asked here some time ago (in fact, on may 20) about the definition of "work", and have come to know that the same amount of force applied for the same time could mean different work done.
I was browsing today's questions and noticed something.
As the work is defined as Force*Displacement, (although I don't know much about what displacement is), it seems that objects exerting some force, but stationary in a reference frame are doing some work for an observer in a diferent reference frame. As any two parts comprising an object are attracted to each other through gravity, and if the object does not change shape, there is a force to cancel out the effect of gravity, and as the object is displaced (right?), objects in an inertial motion seem to do work.
Is it right for objects not changing velocity to be doing work?
It's not possible for objects to exert a force on each other while remaining stationary. If you push against a wall you will accelerate away from it unless you brace yourself against something that's ultimately attached to the wall, like the floor, in which case the sum of the forces against the wall and floor will be zero. There's no net work being done with respect to any reference frame. Objects do self-gravitate and there is a force opposing that, but the sum of the gravitational and opposing forces is zero. -- BenRG (talk) 13:44, 4 July 2009 (UTC)[reply]
(ec) Let us first see what Displacement is. It is a vector, having direction pointing to the direction of the overall motion, and magnitude the length of the shortest line joining the initial and final points. Please read the relevant the relevant article for further clarifications. We need to get one more point clear. Say I push you (literally). The force is applied by me and you move. The product of my force and your displacement is work. So Work done by an object A on another object B is the force applied by A to push B multiplied by the displacement moved by B. I have to say, it should be a dot product, but never mind. it seems that objects exerting some force, but stationary in a reference frame are doing some work for an observer in a different reference frame. Yes, that's right. Work is dependent on reference frame, that is, it depends on how you look at it. As any two parts comprising an object are attracted to each other through gravity, and if the object does not change shape, there is a force to cancel out the effect of gravity, and as the object is displaced (right?), objects in an inertial motion seem to do work. I think you are a little confused. Objects push other objects to do (mechanical) work, not themselves. However, you can say gravity (earth) does work on these objects. Is it right for objects not changing velocity to be doing work? The fact that whether the object that is doing the work is moving or not is irrelevant. What matters is the force applied by the object and the displacement on the object on which work is done. Rkr1991 (talk) 13:50, 4 July 2009 (UTC)[reply]
I should have said "objects doing nothing else than inertial motion" for the last one? And (though I may have been confused) as two parts are both attracted to the other by gravity and counter force is by both for both, both parts are applied force and (as the object as a whole is moving) both parts are displaced. That was my point.
Basically if a moving object isn't accelerating, it must be that the net force on it is zero. So while it's possible for something else to be exerting a force on it in the direction of motion and therefore doing work to it, some other force either from the same source or from somewhere else must be canceling it out and therefore doing the same negative work to it, which is why the kinetic energy of the object stays constant. Rckrone (talk) 19:00, 4 July 2009 (UTC)[reply]
So, it is the net force that matters. Then no work done for objects stationlly in a reference frame should be ascribed to zero net force than to zero displacement in the reference frame, because displacement differs in reference frames.
Like sushi (talk) 01:42, 6 July 2009 (UTC)[reply]
One more thing. Different time lag between two works results in different displacement (not one while the force is applied, but overall displacement) with the same total work, even in the same reference frame. Or can works with a time lag not be added or subtracted directly? If there is no problem with this, I think I need to understand "work" as something that does not reflect total displacement in a reference frame nor force (independently of reference frames) straightly.
Like sushi (talk) 05:23, 6 July 2009 (UTC)[reply]
You're free to talk about the work done by specific forces, but if you want to consider the total work done by object A on object B, then that's going to be the value corresponding to the net force of object A acting on object B. For example in the case of two halves of a moving object exerting gravity on each other, if you wanted to you could say that half A is doing work on half B through gravity, but at the same time A is doing the same negative work on B through the normal force, and so the total work that A is doing to B is zero.
As for the time thing, work is given by W = F.d only in the case of a constant force. If some displacement takes place in the absence of any force, then the work being contributed at that time is zero. For work based on a time dependent force you would need something more like where v is the velocity of the object. Rckrone (talk) 08:22, 6 July 2009 (UTC)[reply]
Thank you for replying. I think I understand that total force and work is zero in the case. But about the time lag, I don't mean not-constant force. I am thinking about two series of works by constant force which are done with a time interval.
I'm not sure, but is mass needed to deteremine the velocity when the work and force are given? I think it is not needed to deteremine the force when the work and velocity are given.
Definitely insect pupae, the question that now remains: pupae of what? Could be some sort of potter wasp or mud dauber. The only way to be sure (or at least have a better id chance) is to take some pupae and put them in a container to allow them to hatch and attempt to id the imagos. We'll await a further post. Richard Avery (talk) 17:40, 4 July 2009 (UTC)[reply]
In a medical article Im working on, I need a term to describe the coining of new syndromes... This has to do with Rumination syndrome, where a recent paper proposes the characteristics, diagnosis criteria, causes, and potential outcomes of the disorder in adults (Where the syndrome until now was considered a disorder of infancy).
Is there a term to describe this process of formally and medically assigning the symptoms and causes of a disorder/disease? -- ʄɭoʏɗiaɲτ¢17:47, 4 July 2009 (UTC)[reply]
I am reading a science fiction book and the "antagonist" is a "rogue pulsar." In the story, there is a rogue pulsar travelling through a solar system and it threatens to destroy a planet and it's civilization on its way by. Is this possible? Can pulsars travel through space? —Preceding unsigned comment added by 216.154.19.192 (talk) 19:07, 4 July 2009 (UTC)[reply]
Well, pulsars are just rotating neutron stars, and should have a similar distribution of position and velocity as their progenitor stars. That means that yes, they travel through space and might come close to other stars and solar systems. But they are not traveling in some kind of controlled manner, and the chances of an encounter with any given star systems are miniscule. Also see this article. What is the title of the book in question? --Stephan Schulz (talk) 19:18, 4 July 2009 (UTC)[reply]
You might consider checking out the book Death from the Skies, which has a chapter dealing with how a black hole might destroy the Earth. A rogue neutron star (of which a pulsar is a subtype) would behave quite similarly to a stellar-mass black hole, so it should be a good approximation. Additionally, pulsars generating X-rays or gamma rays could damage a planet from farther away -- in this case, disruption of the Earth's ozone layer is the primary mechanism. To directly answer the question, though, yes, stars move relative to one another. Most roughly orbit a galaxy in the same direction, but some could orbit in retrograde (likely as a result of a previous close encounter with another star) and a galactic collision would greatly raise the odds of a stellar encounter -- though the odds remain extremely low. Proper motion is the measure of a star's motion relative to the Sun. Barnard's star, for example, will move two light years closer to the Sun over the next ten thousand years. — Lomn03:37, 5 July 2009 (UTC)[reply]
Yes, the book I referenced is, indeed, Star Trek: Mere Anarchy. Thanks everyone. With science fiction, one can never tell just how accurate things are. I'm still trying to get my transporter to work properly . . . —Preceding unsigned comment added by 216.154.19.192 (talk) 04:32, 5 July 2009 (UTC)[reply]
Is there a term for this psychological phenomenon?:
Let's say you're feeling angry or depressed about something which you know, rationally, is petty, selfish, insignificant, and just not worth that kind of emotional reaction(like a comment on the Internet denouncing your favorite books, or being denied a small treat you weren't really entitled to). But rather than admit to yourself that you're getting worked up over that, you tell yourself that your negative feelings are actually caused by something else-- perhaps something(like, say, governmental corruption) of greater significance to the world but with less personal import than the aforementioned petty thing. Has this form of self-deception been documented and named? If so, is it common? 69.224.113.202 (talk) 19:08, 4 July 2009 (UTC)[reply]
It seems to me that displacement is concerned with changing the target of your anger (or other negative emotion), while rationalization is changing the supposed reason for the anger. So the OP's query could go either way, depending upon whether he says, "I am not angry at the parking meter that ate my quarter; but at the town mayor for his incompetence" (displacement) or "I am not angry because of the loss of 25 cents, but because it represent governmental incompetence" (rationalization). Of course, ill-feelings are more diffuse than such linguistic analysis, so the distinction in this instance may be somewhat pedantic. May be relevant, though, if one is writing a novel and needs to use the exact term to prevent those &%@$*# reviewers (who never could write anything worthwhile themselves) from nitpicking it apart. :-) Abecedare (talk) 21:03, 4 July 2009 (UTC)[reply]
Also, just a small clarification: what I had in mind is that the real and presumed reasons for negative emotions may be completely unrelated-- as I tried to convey with the examples of (possibly imagined) personal slights and government corruption. 69.224.113.202 (talk) 23:23, 4 July 2009 (UTC)[reply]
A question of comfort
When I leave the shower cubicle for the cooler bathroom, immediately I feel cold across the arms and whole upper body. Though it takes only a few minutes to towel the upper half completely dry, whereupon the discomfort disappears, the way of doing this makes a subjective difference. I find it better to remove all of the water from one part before dealing with another, as opposed to quickly towelling most of the surface water from the whole area then dealing with the residual dampness a part at a time. I know that the water is conducting my body heat to the surrounding air - is this exactly the same as heating the water to evaporate it? In terms of overall heat loss, will it make any difference what towelling procedure is adopted, assuming water is being removed at a constant rate? I'm assuming that any model of the physics involved should ignore body heat generated by towelling effort, including local frictional heating.≥86.146.175.89 (talk) 19:40, 4 July 2009 (UTC)[reply]
Your trunk may tend to be more sensitive than your extremities with regards to heat changes; for good reason. Since all of your vital organs are there, your body would probably react more negatively to even slight temperature changes than would your arms and legs, which while important, from a survival point of view, are more expendable than say your heart or lungs. --Jayron32.talk.contribs19:45, 4 July 2009 (UTC)[reply]
Not sure about the answer but if you wipe yourself down before leaving the shower-cubicle you'll drive off quicker with less wetness for the towel to pick up. A few 'swipes' of your hands down your arms, legs and front (back is a bit tough!) gets rid of a lot of the water and makes it quicker to get dried in my experience. ny156uk (talk)
I'm not sure it matters how much volume of water is on your body so much as how much surface area of your body is wet. In other words a thin film of water after a quick pass may have nearly the same cooling effect as the large drops before any toweling. So being thorough might be the most efficient in terms of losing the least heat. Rckrone (talk) 20:30, 4 July 2009 (UTC)[reply]
Our article on evaporative cooling deals with a device rather than the human body, but the principle described is the same. There are parts of your body that have a lot of sweat glands and there is always some evaporation there so your body's sensors are expecting that. Any excess is perceived as cooling and will thereby trigger a counter reaction e.g. shivering, constriction of small blood vessels and raising of hairs (goose bumps) Water is actually an insulator, so large drops may take longer to cool you than a thin film because some of the evaporative cooling is used to cool the water drops rather than your skin. That's one of the reasons why misting feels cooler the finer the mist is. The other is more surface area. 71.236.26.74 (talk) 01:13, 5 July 2009 (UTC)[reply]
You can't. According to the vacuum energy article, at least, “consensus among particle physicists is that ... vacuum energy cannot be harnessed to do usable work”. Getting “free energy” would violate the law of conservation of energy, which has never been violated in any experiment. Red Act (talk) 01:12, 5 July 2009 (UTC)[reply]
USPTO has granted a bunch of perpetual-motion-machine patents...just one of many pieces of evidence why existence of a patent for something doesn't prove that the something actually works as claimed and that the patent approval process does not include scientific review. DMacks (talk) 05:38, 5 July 2009 (UTC)[reply]
Right. In particular, the "inventors" who were granted the patent linked to do not actually have their device functioning as a net source of energy.[20] It’s all just a pipe dream. Red Act (talk) 06:08, 5 July 2009 (UTC)[reply]
So you can buy a patent on something that could work, saving the cost and effort of actually engineering the device to actually work. When later someone else, unaware of the patent, finds out how to do things and really builds that machine the first one can claim all the benefits and enforce license payments by law? 95.112.189.234 (talk) 12:03, 5 July 2009 (UTC)[reply]
There's some requirement about a patent being "reduced to practice" in order to have a strong claim of originality (and be a valid patent)...you can't patent an idea, but only specific items or processes of it (though they are often be described in vague or general terms). Here's a decent article I found:[21]. On the other hand, Patent trolls do things at least close to what you propose. DMacks (talk) 14:34, 5 July 2009 (UTC)[reply]
The whole Claims section describes the specifics of what is being patented. That appears to be the intended implementation (facts of the process or device) of this ZPE system, not the idea of ZPE extraction in general. DMacks (talk) 16:42, 5 July 2009 (UTC)[reply]
Doesn't mean it actually does what it says it does, just that it's built the way it says it's built. But going back to the heart of the matter in this, "there is some flaw in the patenting process" is a position supported by numerous legal experts (and also why patents are considered self-published rather than reliable proof of anything other than the facts of the device for WP:RS). DMacks (talk) 17:40, 5 July 2009 (UTC)[reply]
So it just building up a legal insecurity for those doing similar work, if they can be sued for doing that work? Patents regarded as being self-published is one thing, but evoking government authority to protect "self-published" things against other people is another thing. Thus owing a government-granted patent at least means that no one doing work on that subject can be sure not to get suede and sentenced. 95.112.189.234 (talk) 18:31, 5 July 2009 (UTC)[reply]
I don't agree with patents "just" doing that, but otherwise yes, companies have huge legal research departments that make sure any work they might want to patent does not fall victim to prior art of existing patents. They might urge adjusting the company's product or process to "novel enough" to avoid being covered by them, they would certainly use careful wording in new patents to make things look clearly novel vs existing work (whether they actually are or not is often a court issue) and/or by trying to invalidate prior patents as too vague or over-reaching. See also Submarine patent, another trap for the unwary. DMacks (talk) 19:33, 5 July 2009 (UTC)[reply]
So you agree that current patent laws incite companies to spend lots of money to "huge legal research departments" to find the proper "careful wording in new patents to make things look clearly novel" instead of using that money on proper original research and development. 95.112.189.234 (talk) 20:02, 5 July 2009 (UTC)[reply]
I have to correct me: I should have said "current patent practice" instead of "current patent laws", but for a researcher that boild down to all the same. 95.112.189.234 (talk) 20:06, 5 July 2009 (UTC)[reply]
Don't put words in my mouth or make it seem like you're winning a debate that isn't happening by forcing me into a corner that doesn't exist. I'm not (and I refuse to) take a position here on what's happening, I'm merely stating the current situation. I didn't say "instead of". But if companies don't carefully protect their interests and aren't careful to make their products distinguishable from competitors and/or protectable from them, you can bet some other company will take advantage of it (read "find a way to get their customers") because there's clear benefit to doing that. DMacks (talk) 02:25, 6 July 2009 (UTC)[reply]
Well, that ratio is a "rule of thumb" and not an exact requirement. That ratio tends to yield best results for dissolving noble metals (like gold). Take a look at Aqua_Regia#Chemistry for the chemical equilibrium equations. To some extent, any answer will boil down to "because that is the ratio which best dissolves gold, as verified by experiment" - but you can get more specific about the detailed physics and ionic chemistry to explain this statement further. Nimur (talk) 01:34, 5 July 2009 (UTC)[reply]
Aqua Regia was discovered by Abu Musa Jabir ibn Hayyan (known in Europe as Geber) some time before 815 AD, or about 900 years before the rise of the modern atomic theory of chemistry. After first inventing both hydrocloric acid and nitric acid, he then determined the best ratio experimentally. -Arch dude (talk) 11:35, 5 July 2009 (UTC)[reply]
The actual molar ratio between Cl- and NO3- is ~2:1 , this fits ok with the ratio required for dissolving gold which is between 4:3 and 4:1 depending on the extent to which NO2 produced produces more HNO3, I've also heard it said that the ratio is a good one for producing NOCl see Aqua_Regia#Decomposition_of_aqua_regia - which is a particularily active reagent - it's suggested that the ratio is the one which dissolves gold most rapidly.
Sauroposeidon
I was reading the artical on the Sauroposeidon and it says that this sauropod is known from four vertebrea. How it is possible to extrapolate an entire animal (length, weight, etc.) from so little data? —Preceding unsigned comment added by 216.154.19.192 (talk) 04:35, 5 July 2009 (UTC)[reply]
Part of it follows the rule of "quacks like a duck, looks like a duck ..." There is a lot more to it, though. Bones grow in response to the stress that they are subjected to in addition to the basic plan laid out in the animals DNA. So the size of a bone will tell you something of the size of the animal. From the shape of the bone you can deduce where in a body it would have been, based on similar bones in other animals. The article states that the ribs were still attached. Our article doesn't say, but in dinosaurs (and some reptiles today) all vertebrae had ribs attached. From the size of those you could also deduce the size of the neck. Blood vessles, nerve channels and tendons leave holes and grooves in bone. From those you can sometimes guess how muscles were attached and thus what an animal looked like and how it moved, based on what is known of similar features in modern animals. There are also bones of related animals where more complete skeletons have been preserved. 71.236.26.74 (talk) 06:14, 5 July 2009 (UTC)[reply]
TRYING TO FIND AN ARTICLE ON HOW COME DOES IT SNOW
There is a lot of information about snow in the article titled "Snow". I see several paragraphs about how snowflakes form and fall. DMacks (talk) 07:17, 5 July 2009 (UTC)[reply]
Intergovernmental Panel on Climate Change trends
It seems that every time the IPCC comes out with a report they say their previous forecast had underestimated some effect or their model has improved and the effects will be worse. And now I read on the front of New Scientist "It's worse than we thought" about the latest forecasts on sea level rises compared to the 2007 report. Is there any aspect in any of their reports where a later report has said an effect will probably not be as bad as they said previously? Dmcq (talk) 10:01, 5 July 2009 (UTC)[reply]
I don't think that's a correct observation. As far as I can tell, the IPCC position has been fairly stable. The level of detail and the confidence have increased over time (and with that negative consequences can be predicted more exactly), but the basic predictions have not shifted a lot. The 1990 report estimated 3 degrees of temperature increase during the 21st century, the 2007 report has a number of scenarios that still cluster around the same value. Sea level rise from 2001 to 2007 is similar, too (in fact, the nominal 2007 range is lower, but explicitly excludes non-linear changes in polar ice caps). --Stephan Schulz (talk) 10:24, 5 July 2009 (UTC)[reply]
I agree with Stephan Schulz - the predictions have been, very roughly speaking, stable, and I believe there are examples where the prdition has been less significant that in the prior report. It is temping to put together a chart of of the key predictions, but I fear this may run into problems. A small problem is that in some cases the central estimate has gone down, but the range has gone up. A larger problem is that they have modified the way they present some of the values, so there's not precisely an apples to apples comparison. While adjustments for these issues are possible, they constitute research, so they must be done outside WP. Additionally, the reference to the New Scientist statement implicitly accepts its validity - I don't believe everyone or even a consensus is on board with that conclusion.--SPhilbrickT13:25, 5 July 2009 (UTC)[reply]
Sorry yes, reading it better you're right. It is surprisingly consistent despite the improvements in measurements and models. Perhaps I just read too many scare stories that keep pointing out that it could be far worse and quoting the highest figures. And the range of values has got wider instead of narrower because they've put in a number of different scenarios. Dmcq (talk) 16:08, 5 July 2009 (UTC)[reply]
If the cheese is left open it will dry out - a hard cheese can't oxidise in the middle, there might be some oxidisation at the surface - but I don't know what process this is.83.100.250.79 (talk) 13:25, 5 July 2009 (UTC)[reply]
Cheese may oxidize some, but bacterial and yeast action will also work on exposed cheese; if the right mix of cultures are present, you will get a very tasty cheese indeed. These cultures will tend to soften, rather than harden, the cheese. The hard rind is mostly due to drying out. --Jayron32.talk.contribs17:44, 5 July 2009 (UTC)[reply]
If you leave your cheese in the fridge unwrapped, it will dry out. End of story. If you put it in the fridge, you have to wrap it in plastic. If you live in a climate where you can leave it in a cool dark cellar, you can wrap it in cheesecloth and it will be a happy cheese for a considerable time. Looie496 (talk) 01:58, 6 July 2009 (UTC)[reply]
If it is placed in a sealed plastic bag in the refrigerator at 40 degrees Fahrenheit, it should not dry out as you describe, but it may eventually get green mold. If vacuum sealed it may last longer. Edison (talk) 02:20, 7 July 2009 (UTC)[reply]
biology red blood cells
When red blood cells are placed in pure water it bursts,this is due to the absence of which structure.
Since Axl didn't say it, one of our policies is not to answer your homework questions for you. What Axl did - pointing you to how to find the answer - is all we do. Vimescarrot (talk) 14:44, 5 July 2009 (UTC)[reply]
This question has been removed as it may be a request for medical advice. Wikipedia does not give medical advice because there is no guarantee that our advice would be accurate or relate to you and your symptoms. We simply cannot be an alternative to visiting the appropriate health professional, so we implore you to try them instead. If this is not a request for medical advice, please explain what you meant to ask, either here or at the talk page discussion (if a link was provided).
Just a question, as I am ignorant of this subject matter -- is the still pool connected the moving current of the river? Bus stop (talk) 21:06, 5 July 2009 (UTC)[reply]
An "oxbow" would also fit that definition. It is said to be: "An abandoned meander in a river or stream, caused by cutoff. Used to describe the "U" shaped bend in the river or the land within such a bend of a river." Bus stop (talk) 21:37, 5 July 2009 (UTC)[reply]
This glossary is a good find. Seems like "backwater" is the term closest to what I'm looking for—but "backwater", it appears, can be used to refer to something quite vast. I'm looking for a word that can be used figuratively to refer to something off to the side (of the movement and activity of a like substance). I vaguely remember reading or watching something that mentioned still pools connected to a moving body of water—and that they were ecologically important to some species. For example, if you wanted to spear yourself a fish, you might want to find one of these. But it's possible that there isn't a short term for this. —Preceding unsigned comment added by Alfonse Stompanato (talk • contribs) 23:10, 5 July 2009 (UTC)[reply]
Well, Lard suggests that most lard should not melt below temperatures of 30oC (85 or so degrees Fahrenheit). However, lard, like all animal products, will probably spoil if stored for extended periods at room temperature, so storing in a refrigerator is recommended. Intelligentsium22:05, 5 July 2009 (UTC)[reply]
Google books search [22] gives old references suggesting temperatures for long term storage of lard anywhere from 31 to 60 degrees Fahrenheit. Certainly people have stored lard for a time at room temperature, but long term storage seems to require lower temperatures. [23] suggests that antiooxidants can delay lard becoming rancid. [24] Says lard's shelf life is "not particularly long."[25] say that supermarket lard will be usable for one yuear if refrigerated. Lard makes superior pie crusts and biscuits, but the saturated fats are not that healthful. Edison (talk) 22:19, 5 July 2009 (UTC)[reply]
Perhaps - if you could kill every last bacterium and mold spore in the stuff (eg by pasteurization or irradiation) - then you could either can, bottle or vacuum seal it and keep it for a very long time. Whether it would spoil for other reasons (internal chemical reactions, etc) is tough to estimate. But other meat products can be canned (think Spam) and kept pretty much indefinitely at room temperature - those military ration packs are vacuum-sealed and last almost indefinitely - even at quite high temperaturess. I think lard should survive similar treatment. SteveBaker (talk) 23:30, 5 July 2009 (UTC)[reply]
Lard is essentially all saturated fat; as such it is probably atleast as shelf-stable as say vegetable shortening, that is if you aren't going to leave it already opened in your pantry for months at a time, you probably don't need to refrigerate it. It may be animal derived; but its no more a "meat" product than "vegetable oil" is a vegetable. --Jayron32.talk.contribs23:57, 5 July 2009 (UTC)[reply]
OR: We used to store lard in a pot. every couple of days it was boiled in a pot of water and then put in the "larder" (sic.) after the pot no longer felt hot. When the lard had solidified on top of the water it was removed, the water was thrown out and the lard was kept till the next round or until it was used in cooking. This procedure was done as part of the usual cooking routine. So if the stove was run on firewood or coal there was no need for starting it for a separate run. I think there is an old saying out there about having "a pot of lard on the fire". 71.236.26.74 (talk) 03:39, 6 July 2009 (UTC)[reply]
WP:OR Living elderly cooks who used lard to make delectable baked goods say they stored it in the refrigerator. I have seen it turn brown and rancid at room temp in a cabinet. If you make biscuits, piecrust, cookies and such with it every day you could use it up before it turned rancid. Edison (talk) 02:18, 7 July 2009 (UTC)[reply]
Bony lumps
My mind is teasing me; I cannot remember the term for this. There is an inherited condition where there are additional deposits of bone in the mouth cavity. They may be present as bumps in front of the teeth (i.e. within the gum), ridges on the palate, or even processes within the mandible. The condition is not usually a source of trouble; they're just extra bone. I'm drawing a complete blank and my look through our various dental and anatomical articles isn't helping me. I am not, by the way, think of something like tonsilloliths, but of actual additions to the normal bones. Matt Deres (talk) 23:48, 5 July 2009 (UTC)[reply]
Stated that the coal inside a firebox reaches a temperature of 3,500 degrees. This could not possibly be correct. Iron melts way below 3,500 degrees. —Preceding unsigned comment added by 24.189.180.238 (talk) 01:42, 6 July 2009 (UTC)[reply]
I don't know where the source is for that 3,500F figure. But a couple of web pages ([26], [27]) mention firebox temps of 2,500F. Our page on iron gives a melting point of 2,800F. But even if the 3,500 temp is right, that second web page (which give a melting point of iron of 2000F), as well as our page on fireboxes, suggest that melting can be prevented by keeping the firebox covered with cooler water. Makes sense to me, because it reminds me of that camp trick of boiling water in a leaf over a fire. --Allen (talk) 02:07, 6 July 2009 (UTC)[reply]
Wikipedia defines "red hot" (in relation to heat) as follows: "The glowing color of a heated object between about 950 °F and 1500 °F (510 °C to 816 °C}". - GlowWorm. —Preceding unsigned comment added by 98.17.44.60 (talk) 03:16, 6 July 2009 (UTC)[reply]
Coal is a pretty poor conductor of heat, I believe, so it is entirely possible that the coal at the centre is that hot but the coal at the edge, where it is contact with the iron, is below the melting point of iron. Cooling the firebox with water would help maintain that. --Tango (talk) 03:36, 6 July 2009 (UTC)[reply]
Actually, I remember seeing a bit on Modern Marvels or some similar show regarding locomotives that the coal inside a firebox was so hot that the entire thing had to be jacketed in water; this water of course turns to steam and drives the locomotive. However, the show claimed that if the water were allowed to run low, the burning coal could actually melt the iron of the firebox. So the numbers seem realistic. If the iron is constantly being cooled by water, it itself may never reach its melting point even if the coal inside it DOES. --Jayron32.talk.contribs04:36, 6 July 2009 (UTC)[reply]
A locomotive firebox is usually surrounded by water. If the water level in the boiler falls below the top of the firebox, there is a serious danger that the top of the firebox will become too hot, weaken and fail under boiler pressure. A safety device called a fusible plug gives a loud audible warning if there is an insufficient height of water above the top of the firebox. Gandalf61 (talk) 09:24, 6 July 2009 (UTC)[reply]
<following moved from separate post 71.236.26.74 (talk) 15:45, 6 July 2009 (UTC)>
Maximum firebox temperature is 2500 Fahrenheit degrees, according to this reference:
[28] 24.189.180.238 (talk) 15:12, 6 July 2009 (UTC)[reply]
Meanwhile, locomotives can always explode if something goes wrong: read the paragraph of 2-6-6-6 that begins with "One H-8". I don't know the interior workings of steam locomotives, so it might be that this wasn't a firebox issue, but it sounds vaguely familiar. I'd provide pictures if I could, but the only photos of this incident that I've seen were in a printed volume. Nyttend (talk) 04:39, 7 July 2009 (UTC)[reply]
Doll's rule in evolutionary biology
I want to know what is Doll's rule in Evolutionary Biology.
I am preparing for an Anthropology exam conducted by public service commission of India. The Doll's rule is part of the syllabus for that exam. I did not get proper result when I searched in Google. Please refer the syllabus for the exam in the following link
http://www.threeauthors.com/upsc-exams/show.asp?xx=cse_m&x=9&yy=cse_m
I request you to give me information about Doll's rule
Are you sure you don't mean Dollo's law? Our article is short, but well referenced, and pretty self explanatory. I'll let you read it and decide if that is what you are looking for. It is certainly related to Evolutionary biology... --Jayron32.talk.contribs05:39, 6 July 2009 (UTC)[reply]
How does a bicycle puncture repair kit work?
I would like to know how the components of a bicycle puncture repair kit work. Is sand-papering the area really necessary? I notice the repair plaster things are mostly black (like the inner tube itself) but with an orange layer which is supposed to interface with the rubber solution. Does the rubber solution dissolve this orange layer? Does it dissolve anything else? What's in the orange layer? ----SeansPotato Business07:41, 6 July 2009 (UTC)[reply]
This question fall in the area of psychology: I'm trying to find a name for a theory I have heard. Acoording to the theory (or what I remember of it) we do not - in a way - remember a past event but the last time memorized that event. That is, when memorize something we don't only retrieve a memory, we also "rewrite" it. I'm not sure I found anything on the subject on Wikipedia although confabulation touches the idea. I'd be happy to have any pointers as to what terms I could use to search scientific databases. Samulili (talk) 18:31, 6 July 2009 (UTC) 08:12, 6 July 2009 (UTC)[reply]
I don't know the exact hypothesis (which is the correct name of a scientific "theory", have a look at theory) you describe here, but it certainly touches long-term memory, long-term potentiation and therefore memory consolidation. And my impression is that this hypothesis is oversimplifying a lot, so it probably is no scientific explanation, rather a "layman's terms" explanation. Our memory is more complex than this explanation suggests (for example, there is more than one type of memory). --TheMaster17 (talk) 09:04, 6 July 2009 (UTC)[reply]
I know what you're talking about - the idea is that every time we remember something, the act of remembering it "rewrites" it - possibly with small changes. This is supposed to account for phenomena like False memory syndrome where the act of being repeatedly quizzed about a non-existant event can cause that event to become a memory. Lost in the mall technique is a way to demonstrate that this happens. I think Interference theory comes close to what you're looking for. SteveBaker (talk) 13:59, 6 July 2009 (UTC)[reply]
It's not a Wikipedia article but there was a very interesting story about a study on memory (and similar to the original question,) which I heard on NPR: [here]. The summary is that tests on the effectiveness of Beta Blockers led to research into how well people remember things while taking the drugs and then after they stop taking the drugs. Apparently it was possible to coerce a pre-existing memory OUT of someone's mind while they were on the drug, by causing them to recall a memory and then fail to re-remember it. They would then have no recollection of that memory even after they stopped the drug treatment. --Jmeden2000 (talk) 20:24, 6 July 2009 (UTC)[reply]
Cow identification
What breed are these brown cattle in Cambridgeshire? You pass a lot on the path from the university to Grantchester.
I believe the "bankers" who took over General Motors from Durant were actually the E.I. deDuPont de Nemours Co. When the government ordered DuPont to divest itself of all General Motors stock they had to pass a special law to keep DuPont/General Motors stock owners from having to pay so much tax that they would flood the market of GM stock. —Preceding unsigned comment added by 76.69.149.145 (talk) 10:47, 6 July 2009 (UTC)[reply]
Hello. Is there any simple way to determine the valence of an atom just by looking at its position on the periodic table? If not, which is the simplest way to know the valence of an atom (I'm fed up with having to look up each atom on the Internet :()? Thank you!! —Preceding unsigned comment added by 83.34.232.9 (talk) 11:10, 6 July 2009 (UTC)[reply]
If you mean the number of electrons in the last shell, then the group the element is in is the number of electrons in its valence shell, e.g. Oxygen is in the 6th group and has 6 valence electrons. —Preceding unsigned comment added by 116.71.51.138 (talk) 14:43, 6 July 2009 (UTC)[reply]
That rule of thumb works for many small atoms, but larger more complex atoms have pathological valence behavior. The transition metals are the perfect example of this - almost all of them have two valence electrons, even though they span many columns of the table. Use caution when applying rules of thumb to valence electrons, as the physical behavior can be more subtle. Nimur (talk) 15:00, 6 July 2009 (UTC)[reply]
For main-group elements (The tallest groups, AKA the s- and p- groups, AKA the "A" groups), the ones that start with H, Be, B, C, N, O, F, He; just number those groups (ignore the transition metals for now) from left to right; that is the number of valence electrons in those atoms. Thus, the first tall column from the left has 1 valence electron, the second tall column has 2, the third tall column has 3, and so forth. This only works for the main groups.
For the transition elements, it is a much more complicated situation. Basically, the "d" orbitals are so close in energy to the "s" and "p" orbitals that the atom can freely "borrow" from these d-electrons as needed to expand the number of availible valence electrons. All transition elements at first glance should have exactly 2 valence electrons (since they all have a full s orbital on the outermost energy level, and the "d" electrons are always added to an interior energy level). Take an element like Manganese for example. It has the basic electron configuration or [Ar]4s23d5. So one would say it has a valence of 2 electrons, since there are 2 electrons on energy level 4. However, since the 4s and 3d orbitals are very close in energy, one can find a wide range of valences, and thus oxidation states, for Manganese this is pretty much anything from +1 to +7 inclusive; though the main ones are +2, +4, and +7.
So basically, the system is ONLY reliable for the main group (tall columns) elements, the middle bit is pretty much memorize it or look it up. --Jayron32.talk.contribs19:28, 6 July 2009 (UTC)[reply]
Waste disposal
I was wondering what would happen to an everyday object if it were propelled towards earth from outerspace. It would definitely burn up. Venus has a more dense atmosphere than Earth and a higher surface temperature too so would it not make an ideal place to dump? What would be the problems and disadvantages of doing so? Thanks. —Preceding unsigned comment added by 116.71.51.138 (talk) 14:15, 6 July 2009 (UTC)[reply]
How were you going to get waste to Venus (or anywhere in outer space)? Using a three-thousand-ton rocket, you can loft about fifty tons away from the Earth — and building the rocket and refining its fuel generates more than fifty tons of waste, even if you could recycle all of the components. (For comparision, New York City generates more than ten thousand tons of waste every day.) TenOfAllTrades(talk) 14:33, 6 July 2009 (UTC)[reply]
(EC) Your waste disposal suggestion has a flaw in the "going up" part, rather than "coming down" portion. For rocketsgoing into orbit you'd have to budget $100 million per launch. Attempts to cut those costs by an order of magnitude ended in failure. Since you don't want to have your trash spread over a significant area of real estate or ocean, you'd have to go for a reliable system. NASA budgets about $250,000 per pound going to the Moon and I guess you'd have to multiply that by a significant factor if heading to Venus. You'd also have to transport your trash to suitable launch sites (not in my back yard). There'd also be significant additional waste from producing and discarding the rocket. Since the carbon footprint of moving the stuff into orbit or hauling it toward Venus is unlikely to be lower than that produced by Incineration the idea isn't going to fly :-)71.236.26.74 (talk) 14:44, 6 July 2009 (UTC)[reply]
One thing to keep in mind is that you're trying to solve a problem that really doesn't exist. The whole "we're running out of places to dump waste" meme is a misperception. As I understand it, it started because *some* landfills around heavily populated areas like New York were no longer accepting garbage, but there is more than enough room in rural areas for more landfills. It's a thousand times cheaper to ship garbage from New York to Nebraska than it is to shoot it into space, even when using state-of-the-art nonpolluting landfills. This also ignores the fact that most of the garbage can be re-used, either through recycling the metal/glass/plastic/paper, or by composting the organics, or even just by burning it for energy. (Again, getting rid of it with state-of-the-art low-polluting incinerators is still orders of magnitude less expensive than shooting it into space.) -- 128.104.112.85 (talk) 16:23, 6 July 2009 (UTC)[reply]
Plus following generations might curse you for dumping precious resources in hard to get places. They might have to resort to sorting through our trash for things like copper, gold and titanium (there might be even better examples) because the mining resources are depleted. Even incinerator ashes would be better than going to Venus for resupply. 71.236.26.74 (talk) 17:03, 6 July 2009 (UTC)[reply]
Before the questioner makes a similar argument for supposed "we will never want it" waste, such as nuclear waste, keep in mind that just because we have no use for the waste at this time does not imply that we will never have a use for it in the future. Considering nuclear waste, it may turn out that nuclear waste will become a highly valued resource in the future. It may turn out that it is never used and future generations curse us for creating it. We do not know the future, but we do know that digging up waste on Earth is easier than travelling to another planet to get it. -- kainaw™17:18, 6 July 2009 (UTC)[reply]
Supposing that one has some waste to dump in outer space, what is the attraction of using a little planet like Venus when one can drop the waste in the Sun ? Cuddlyable3 (talk) 17:52, 6 July 2009 (UTC)[reply]
It is easier to get to Venus than the Sun. To reach the Sun you have to get rid of all of the angular momentum an object on Earth has due to the Earth's orbital velocity. To get to Venus you only need to get rid of some of it. --Tango (talk) 01:58, 7 July 2009 (UTC)[reply]
The volcano will readily return whatever it is to the surface, in far more diffuse and potentially hazardous form. If the waste can be incinerated, then use an incinerator. If it's something like nuclear waste, you'll irradiate much of the island. — Lomn18:56, 6 July 2009 (UTC)[reply]
The molten rock is moving. So, the uranium must sink faster than the upward flow of the rock. Add to that the fact that the uranium will become molten as well and it is obvious that some of the uranium will be pushed back to the surface - causing a huge radiation problem. -- kainaw™19:11, 6 July 2009 (UTC)[reply]
Uranium melts at 1100 degC - Lava (according to our article) sits between 700 degC and 1200 degC. I would assume that it gets hotter the deeper in the volcano you go. Uranium is about 8 times denser than lava - so it would likely sink to the level where it melts - then mingle with the rock - and ultimately be shot back out of the volcano - perhaps as ash - spreading radioactive debris over a large area. Definitely not a good plan. If it were that easy - trust me - we'd already be doing that! SteveBaker (talk) 01:45, 7 July 2009 (UTC)[reply]
Since this post goes with the "featured picture item" a bit higher up I'm going to copy it up there to keep the thread together. If no one is going to object I'll delete it here later. 71.236.26.74 (talk) 15:43, 6 July 2009 (UTC)[reply]
Simulate semiconductor
Ok, I'm assuming that there is some software that allows you to simulate flow of e and holes in a semiconductor piece whose doping is specified.
Is there a generic name for such softwares? I want to write one as my project. Should I post this in Physics, computer or maths ref desk. It involves all three.
Putting 'simulation' 'electron hole' etc into a search engine throws up many examples - as for specific software - don't know.
Also see [30] which gives transport physics in semiconductor devices as a possible name for the area - also try searching for "transport models semiconductor devices" - it looks like "hydrodynamic model" is an alternative method to a "monte carlo" based model.83.100.250.79 (talk) 21:49, 6 July 2009 (UTC)[reply]
Have you looked at SPICE ? SPICE is the standard electrical engineering simulation software for semiconductors. The more advanced commercial SPICEs (like HSPICE) simulate device-physics quite thoroughly. You can program down to very specific minutia of the semiconductor geometry, physical properties, thermal effects, etc. Depending on who you ask, SPICE is either a software simulator, or a programming language, or an internal engine for another CAD tool. In its original incarnation, SPICE was 1-part circuit net simulator and 3-parts differential-equation-solver; it has since evolved into a full-fledged circuit design, layout, and simulation engine that is distributed in several free and commercial versions, and integrated into larger CAD packages. Nimur (talk) 23:35, 6 July 2009 (UTC)[reply]
Dogs and tyres
Assuming that, for a dog, a car is a natural object to urinate, is there a special reason why they always do it on the tyres? For us this choice is more or less OK, but what do they mean? Thanks --pma (talk) 17:34, 6 July 2009 (UTC)[reply]
My guess is because the tire is attached to the ground, much as a growing plant (a tree) might be. But I am not sure why a tree, except that marking territory may be involved. Bus stop (talk) 17:45, 6 July 2009 (UTC)[reply]
(ec) :Dogs signal who they are by marking with urine any prominent outcrop on the ground that other dogs may sniff. The tyres of a car are the only parts that touch the ground. Cuddlyable3 (talk) 17:47, 6 July 2009 (UTC)[reply]
Seeing as no dog pheromones have been scientifically described or characterized, and no human pheromones have been scientifically described or characterized, I would suggest the previous answer be taken with a huge dose of skepticism. Rockpocket02:03, 7 July 2009 (UTC)[reply]
Because it's there. I walked a lot of male dogs and they pee/poo anywhere within reach. Tires just happen to be a convenient place. Since tires give off a lot of scents obtained from travel (roadkills, poo and other street smells) they become a magnet to curious dogs. My dogs also sniff my feet to check where I went when I come home from a journey. --Lenticel(talk)05:58, 7 July 2009 (UTC)[reply]
walking across the USA
What supplies would be best for walking across the USA from Atlantic to Pacific (say Baltimore to Portland Oregon)? Weight should be 50lbs or less, and you would start in April. Assume you do not have shops at which you can resupply. 65.121.141.34 (talk) 18:19, 6 July 2009 (UTC)[reply]
Sorry should have clarified better. This is a survival scenario. So for food, a rifle say is acceptable as there are animals to eat. 65.121.141.34 (talk) 19:06, 6 July 2009 (UTC)[reply]
(before Edit conflict with OP) How do you propose to feed yourself on less than 50 pounds? It is probably going to take 8-9 months to make the trek by foot; it takes people about 3 months to hike the Appalachian trail, and that is probably 1/3rd the distance you are trying to cross. If you are not going to be buying any food along the way, then the best thing I can think to do is to arrange for someone to mail you food and other supplies and pre-designated depots. Packages mailed to a post-office or UPS store in your name can be designated to be held for pick-up. If you carefully plan your route, and have your friends mail you packages to the right places to arrive at the right times, you can keep yourself stocked. Alternately, you can have someone go ahead of you in a car and bury caches containing the supplies which you can dig up; that's often how early explorers did it. But considering that you probably need to eat at least 1-2 pounds or so of food each day, you will probably only be able to carry a month or less of food (considering also that part of your 50 pounds is going to be non-food supplies as well). (after Edit conflict) OH!!! You want to be able to hunt and forage for your own food? That will be significantly harder; probably impossible to do so legally, given the laws in many places about poaching or the like. --Jayron32.talk.contribs19:10, 6 July 2009 (UTC)[reply]
It is also guaranteed to a) reduce any other provisions and your clothing to shreds, since goats will eat/chew anything and everything. b) extend your trip by a couple of years because most goats aren't that cooperative, don't like hiking all day and spend most of their time awake either eating or ruminating during which time only an act of god will move them. Also the US is no longer the Wild West. If you want to go hunting you need a hunting license for each county you are passing through. Fishing licenses are separate in most jurisdictions. Regulations on carrying weapons and ammunition vary widely. The bigger issue than food is going to be water. There are quite a few places where there's absolutely no water to be found for miles around. Then there are places where the water that is there will kill you. Either fast or slowly. Then there's the weather. People who wander away from civilization do get killed due to exposure. In summer you get toasted [31], in winter frozen to an icicle [32]. ...and all that without meeting any of the even less desirable elements (of society). [[33]] 71.236.26.74 (talk) 21:17, 6 July 2009 (UTC)[reply]
It isn't possible. You have close to a thousand miles of desert and mountain to get across, and you won't make it. There's hardly anywhere where you can legally hunt out of a special season. If you carry a gun, you'll be arrested 20 times, and even if not, hunting would slow you down so much that you'd be caught by winter halfway. This just isn't a feasible scenario. Looie496 (talk) 20:49, 6 July 2009 (UTC)[reply]
Actually, in most of the United States, it is technically perfectly legal to carry a firearm unconcealed (legislation varies by state and local jurisdiction - Wikipedia has a great set of articles, Gun law in the United States and Gun laws in the United States (by state) - but these are guides only, and you should check with the local sheriff or consult a lawyer regarding specifics). Rifles and shotguns are less regulated than handguns in most states. However, even if it is legal to walk along the road carrying a hunting rifle, it will almost certainly draw attention from law enforcement, who may question you (and may have the option to arrest you, depending on local laws). (They will probably also inform the law enforcement in the next district you plan to walk towards that an "armed transient" is en-route). Hunting out-of-season, however, can be difficult (this is called poaching and will be probably be noticed); but it's possible that with effective planning, certain legal game could be found in reasonable proximity to much of the walking route. Nimur (talk) 23:42, 6 July 2009 (UTC)[reply]
If it isn't possible, then it is possible. Bring lightweight fishing gear, and a slingshot. I don't know what other advice to offer, but I too have wanted to walk across the United States. Bus stop (talk) 21:33, 6 July 2009 (UTC)[reply]
You'd also be trekking across large rivers (like the Mississippi), tall mountains (perhaps some with glaciers), major highways, and perhaps fences and private or restricted property (like Area 51). Bring a map, and some, erm, gear. Lightning is also a danger, as are flash floods, tornadoes, blizzards, and other elements of extreme weather. You might encounter bears or rattlesnakes in forests and semi-deserts. Also, where are you going to sleep and use toiletries? You can't possibly walk for 9 months straight, so there have to be suitable places you can stop every day and night. Also, if on the off-chance you happen to be walking in Nebraska when global warming hits, or close to Wyoming when the Yellowstone supervolcano erupts...you might be in a little trouble. And that's not to mention the 2009 flu pandemic (assuming you start your hypothetical journey in the near future), and if you're travelling through a large city, you'd have to use roads and maybe you'll get stuck in traffic and then you'd want to book a hotel. ~AH1(TCU)00:26, 7 July 2009 (UTC)[reply]
Walking across the U.S. without restriction, such as the ability to buy food and water in town as needed, and simply choosing to walk rather than drive, and camp rather than get a hotel, would be entirely possible in about a year or so. One could easily choose a path that would stick to major highways and you should be able to hit at least a rest area with a snack machine and clean running water every day or two. However, crossing the continent as though it were wild; living off of the land and avoiding all civilization would be nearly impossible. Lewis and Clark did it, but it was a well-funded government expedition with the cooperation of native peoples. It took them over a year to reach the Pacific from St. Louis. They left in May 1804, arrived at the Pacific in December 1805, and did not get back to St. Louis until September 1806. Add another 1000 miles to cover the trip from Baltimore, and if you assumed you had to travel under the same conditions they did, the trip the OP proposes would likely take 3-4 years, if you survived at all. --Jayron32.talk.contribs00:43, 7 July 2009 (UTC)[reply]
Also, the shortest journey would seem to be a straight line, but that would run you through Lake Michigan! Under that straight line, it's about 2,370 miles. You might as well stop in Chicago along the way, but it can be done—Terry Fox ran from St. John's, Newfoundland, to Thunder Bay, Ontario (3,339 miles in 143 days), but of course taking breaks every day at cities and towns, all the while with cancer and wearing a prosthesis! ~AH1(TCU)01:00, 7 July 2009 (UTC)[reply]
Hard to believe that noone has mentioned the American Discovery Trail which crosses the U.S. and has been thru-hiked. Apparently there aren't many hikers, campers or hunters among the answerers here. It isn't all that dangerous or impossible. Also hunting licenses are state issued (with extra stamps for migratory birds issued by the federal gov't.) - not by county. Rmhermen (talk) 01:20, 7 July 2009 (UTC)[reply]
50 pounds would be a punishing load to carry on the back. A bicycle would allow you to carry the load and to move at 15 miles per hour or faster on highways (if it did not count as part of the 50 pounds.) If you were afoot, the 50 pounds of load might support you for a month, and you would only be a small fraction of the distance from start to finish. You could carry 10 pounds of food, clothing and supplies on a 40 pound bike, and live off the kindness of strangers. If you carried a laptop, you could probably find hosts every 50 miles or so who would house and feed you free, allowing a 2800 mile trip (per Google maps) in 56 days. If you are a member of some religious denominations, and told them it was a pilgrimage or some such they would likely host you. Edison (talk) 02:12, 7 July 2009 (UTC)[reply]
A strong male hiker can easily carry 50 pounds 20 miles per day up and down mountains -- I've done it. But it takes 2 pounds of food per day to maintain weight if you're hiking long distances, and that's if the food is chosen very carefully, so 50 pounds won't get you through a month even if the bulk of it is food. (An ultralight hiker may get along with less than 10 pounds of non food/water weight.) Also, if you think you can find hosts every 50 miles, you haven't driven across Nevada. In any case, walking across the US is definitely doable if you can resupply with food -- however you'll be carrying well over 50 pounds for some stretches, most of it water.) Looie496 (talk) 03:41, 7 July 2009 (UTC)[reply]
"Easily??!!!" I say bullshit as to carrying a 50 pound pack up and down mountains 20 miles, except for Marines, Commandos or other Rambos. Wheeled transport would be more feasible. Why carry such a load if you can ride or pull it on wheels? There is a good highway system. I agree that a month would be an outside estimate for how long the initial 50 pound pack would support your food needs. As for water, there are lightweight devices for water purification which would suffice except in desert. Edison (talk) 04:59, 7 July 2009 (UTC)[reply]
Responding to Jayron32 above, "living off the land" isn't quite right for Lewis and Clark, as they acquired a great deal of food from Native Americans. And, differing from the OP's idea of walking (solo I assume), Lewis and Clark did not walk except when they had to but rather used boats with rowing crews and tow ropes to pull. And they had a party of (mostly) experienced wilderness travelers, some of whom were regularly assigned "hunting duty" in hopes of bagging some food for everyone else. In those days one was able to wander into the woods or prairie with a gun, hoping to shoot some animal (that was not the property of ranchers, etc, as mostly the case today) to feed your party. In any case, I'm hard pressed to imagine how one would "live off the land", without trespassing and stealing, while walking across Illinois, Iowa, and Nebraska, which have been almost completed converted to farms, not to mention Wyoming, southern Idaho or northern Utah, and eastern Oregon or Washington, as these regions semi-desert at best. Finally, if resupplying at stores is not allowed, and you are planning to hunt for food carrying a pack of less than 50 pounds, wouldn't you rapidly run out of ammo? Perhaps a shorter version would be feasible--say one state rather than the whole country. Pfly (talk) 08:15, 7 July 2009 (UTC)[reply]
Given the abundant thorns, and a lack of anything else identifiable, this could be a variety of thistle, or perhaps a member of the rose family, perhaps some variety of wild blackberry. The leaf shape does remind me of blackberry; but that leaf shape is fairly common and not a good identifier. Do you have any other pictures which show flowers or fruit or other distinguishing characteristics? --Jayron32.talk.contribs19:14, 6 July 2009 (UTC)[reply]
I'm in the UK, so your foliage may differ, but that looks identical to the wild blackberry ("a widespread, and well known group of several hundred species, many of which are closely related apomictic microspecies native throughout the temperate Northern hemisphere") or bramble that has latterly taken over my back garden (gardening is not my favourite occupation). Since blackberry picking was historically a popular pastime, it does not seem unlikely that this plant - if not already present - would have been deliberately introduced to a New York park. I trust the park staff will be able to keep on top of its vigorously spreading habits. 87.81.230.195 (talk) 19:39, 6 July 2009 (UTC)[reply]
The fuzziness was making me think more dogrose than bramble, but it would be easier to tell with more pictures of more developed bits. Any fruit or flowers would help. 89.168.106.72 (talk) 02:29, 7 July 2009 (UTC)[reply]
Here are some more pictures, but it didn't have any flowers or fruit. [34][35] I don't think I've ever seen fruit on it. I may have seen this plant with small white flowers a while ago but I'm not sure. Doodle77 (talk) 02:38, 7 July 2009 (UTC)[reply]
Looking at your other pictures, I am not sure we can get any closer than something in the Rosoideae (rose) family. Dog rose or blackberry or raspberry or any of a number of similar plants will produce similar thorny bramble. If we could see the fruit, we could tell if it had berrys or hips and that would help narrow it down. Likewise, the flowers could be helpful. But given that the plant is not currently flowering or fruiting, it is hard to narrow it down more than that. --Jayron32.talk.contribs03:43, 7 July 2009 (UTC)[reply]
Looking at those pictures hardens my gut feeling that it isn't bramble (blackberry-type) but a wild rose. The stems look too thin and smooth, and the thorns too 'fuzzy', for bramble. Small white flowers support bramble, though. Hmmm. 89.168.106.72 (talk) 04:01, 7 July 2009 (UTC)[reply]
Smooth stem doesn't rule out bramble. If the plant developed from an offshoot or fruit of a bramble bush in s.o.'s garden that e.g. got dropped in the park by a bird, then it is possible that it is in the process of reverting from a "thornless" cultivar back to the original thorniness. Lots of cultivated varieties of the Rosoideae do that if left to their own devices. 71.236.26.74 (talk) 09:24, 7 July 2009 (UTC)[reply]
Penis
I know that all the penis enlargment pills currently avaialble are just scams but is there any promising and genuine scientific research going on to develop a pill that really does work to enlarge the penis?
No. If anything were remotely promising, it would already have been headline news in every media outlet just as Viagra was the top of the news everywhere when it just began the first round of trials. -- kainaw™19:30, 6 July 2009 (UTC)[reply]
i have seen penile enlargements; but was always shy to ask its owner the cause.
still don't believe in those wierdos who advertise on enlargements; as they are only out to plunder your bank!!Seacucumber06 (talk) 06:16, 7 July 2009 (UTC)[reply]
Every day in my email, I get people trying to sell me Acari Berries. What the hell are these things? They claim that they're some sort of new fruit that was found in the Amazon that if eaten regularly can cause weight loss, increase lifespan, prevent cancer, cure various diseases and even enlarge the penis and increase sperm count. I know that it's all quack rubbish but seriously, what is the Acari Berry?
See Açaí Palm. You can blame Oprah for this. Her show claimed that it is a wonder-drug and now the scammers are using it to lure idiots people into handing over their credit/bank info. -- kainaw™19:27, 6 July 2009 (UTC)[reply]
Bird Rescue
Oh no! A pre-flight baby bird has been grounded in my back yard. Luckily, the mother—who appears to be a robin—is still taking care of (i.e. feeding) the thing. Now, I know nature is cruel and everything—but, I mean, c'mon, the little guy is right out there with the whole open mouth routine and everything, and evolution has been sloppy about making sympathy a human-exclusive. I fear that if I leave the robin on the ground it might fall prey to—well—a predator. Is there any simply way to elevate it or something to keep it relatively safe for the night? (I live in a NE US suburb—maybe predation is not much of a threat?)
Do you have something against the cute furry little predators? They have to make a living too. Those fox puppies are just SO cute...and soooo hungry - and you're denying them lunch - what a heartless brute! :-) SteveBaker (talk) 01:27, 7 July 2009 (UTC)[reply]
You could contact a Licensed Official Wildlife Rehabilitator, who might take the wee bird away and care for it, or who might take it away and kill it (I have read of such results), or you could try putting it back in the nest (having observed which nest Mom and Dad bird are rearing the siblings in). Do not attempt any hazardous tree climbing. Edison (talk) 01:57, 7 July 2009 (UTC)[reply]
Usual advice is not to add it back to the nest, as handling the chick can result in scaring the parents away and disturbing the nest can lead to it being abandoned (at least, when I've been in this situation, this is what we were told). You might get away with putting the chick on top of something tall and difficult to climb (like a wheelie bin or bird table), but generally if the parents don't manage to take care of the fellow and get it flying, its only hope of survival is probably you hand-rearing it (so, taking it inside, in a lined box, and feeding it and providing it with water). 89.168.106.72 (talk) 02:23, 7 July 2009 (UTC)[reply]
The advice you cite, about not handling the chick, is contradicted by the RSPB link above; but the RSPB link talks about "UK birds" having a poor sense of smell...which begs the question, is it OK to handle birds in other countries to get them back in the nest? Tempshill (talk) 03:28, 7 July 2009 (UTC)[reply]
Can one create a decent solar panel out of the solar cells found in solar powered calculator? If yes, how many do I need and how should I stick them together. The resulting solar cell aggregate should at least power a small electric fan or light bulb. Just curious.--Lenticel(talk)01:03, 7 July 2009 (UTC)[reply]
Since each photovoltaic cell from a calculator only creates a small voltage at a small current, you must connect them in parallel to increase the current, and connect these units in series to get the required voltage. If you take a photovoltaic unit out of a calculator, you can use a multimeter to determine its output characteristics in sunlight. You can use a battery and a rheostat to determine the minimum current and voltage needed by your chosen load. An LED light would be a better choice than an incandescent bulb (like a regular flashlight bulb) to be powered by an array of such photocells. Edison (talk) 01:52, 7 July 2009 (UTC)[reply]
Thanks. I just thought just now how "ungreen" this would be since you'll be discarding a lot of useful electronic gadgets for something that can only power a small appliance/light.--Lenticel(talk)02:36, 7 July 2009 (UTC)[reply]
assessing potential fish stock / resources in a region
how does on assess the existing marine resources, especially fish stocks in a particular region, given the scenario that the stocks are declining due to myriad of reason; especially fishing pressure? —Preceding unsigned comment added by Seacucumber06 (talk • contribs) 06:06, 7 July 2009 (UTC)[reply]
I read the first few lines of the article but I cannot understand how it would effect sniping or long range shooting of unguided weapons. So how does the Coriolis effect effect sniping etc.?--116.71.62.75 (talk) 07:34, 7 July 2009 (UTC)[reply]
Iris scans can be used to uniquely identify people. The UK government is building up a database of them, one way or another. I can also imagine that they could be used to identify wanted people in other countries. My question is, from how far away could you do an iris scan?
I assume an iris scan could be done from a detailed photo of an iris. Such a photo could in theory be taken with a very powerful telephoto lens on a fixed mount. Perhaps illumination by an infra-red or ultra-violet laser could be used to overcome some problems with nightime or haze. The most difficult problem may be aiming the telephoto at the eye on a moving target, but since even cheap digital cameras can find people's faces for auromatic focusing, and the image could be directed into the telephoto by an automatically movable mirror, then its easy to imagine that a computerised aiming system could be set up to do this.
I'm asking my question because I'm wondering if the UK government is going to start recording peoples identities from remote iris scans as they move around the country in the same way that they do now with automatic recording of car registration plates. 78.149.207.75 (talk) 09:50, 7 July 2009 (UTC)[reply]
Please do your own homework.
Resolved
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