Wikipedia:Reference desk/Archives/Science/2010 September 5

= September 5 =

Is it possible for grass to ferment?
Topic says it all. ScienceApe (talk) 00:01, 5 September 2010 (UTC)
 * See Silage Rojomoke (talk) 00:10, 5 September 2010 (UTC)
 * I wouldn't recommend drinking it, though. silage martinis don't have a kick worthy of the effort it takes to choke them down.  -- Ludwigs 2  01:50, 5 September 2010 (UTC)


 * Silage is indeed fermented grass - which proves that grass can be fermented. However, it's particularly nasty smelling stuff and for sure a 'silage martini' would be an incredibly nasty thing!  But that doesn't mean that you couldn't make a nice grass-based wine.  After all, if you leave a pile of grapes to rot - what you get isn't 1992 vintage Chablis...it's a rather nasty pile of rotten grapes.  So presumably, if the right amount of care was taken, it might be possible to get something drinkable by humans out of fermented grass.  Maybe. SteveBaker (talk) 15:42, 5 September 2010 (UTC)


 * It might be worth pointing out that grass ferments inside the rumen of grass-eating animals such as cows and horses. Looie496 (talk) 16:51, 5 September 2010 (UTC)


 * Our inaccurately titled article on Fruit wine mentions that a number of items can be used for making wine, including rose hips, dandelions and even marijuana. There's a bit more (and a lot of repetition) at Non-grape based wine. Come to think of it, if you can make wine from rice, I'm reasonably sure you could make it from grass. Matt Deres (talk) 16:20, 7 September 2010 (UTC)

Science (dark matter and black holes)
What is the "dark matter"? And how black hole can absorbed the time? —Preceding unsigned comment added by Seonti (talk • contribs) 05:56, 5 September 2010 (UTC)
 * See dark matter, and black hole plus event horizon for the second question. Does this help a bit? I also expanded the heading. --Ouro (blah blah) 06:02, 5 September 2010 (UTC)


 * A very short explanation of dark matter is: We know there is a lot of mass out there that we can't detect, but shows itself by means of its gravitational effects. We don't really know what it is. Because we can't detect it, we call it "dark". There are different theories as to what it might be. Nobody is really sure at the moment which one is correct. --Mr.98 (talk) 14:14, 5 September 2010 (UTC)
 * Basically we can observe how fast galaxies are rotating, and how they orbit each other. We can infer the mass of the stars from their brightness. There seems to be too little mass for the speed the galaxies are rotating. IIRC we can only account about 10% of the mass. Therefor either -
 * Our understanding of physics of galaxy rotation is wrong.
 * Our understanding of the relation between the brightness and the mass of stars is wrong
 * Our understanding of the distance to the galaxies is wrong (and thus the distance between the stars is wrong).
 * There is more mass in galaxies, which we can't see.
 * The first three have been discounted. 2 and 3 are related to standard candles. Thus only the last one remains. The main candidates for the missing mass are -
 * Massive compact halo objects (MACHOs). These are brown dwarfs, black holes and other large collections of normal matter which is too dark for us to see.
 * Weakly interacting massive particles (WIMPs). These are isolated particles such as neutrinos and large hypothetical particles, that only interact with gravity (and the weak force).
 * Currently WIMPs are in favour over MACHOs, but there is not enough evidence to decide either way.
 * CS Miller (talk) 15:50, 5 September 2010 (UTC)
 * There are constraints on the total amount of baryonic matter from Big Bang nucleosynthesis. If there had been significantly more protons and neutrons (which MACHOs would be made of) around in the early universe, then BBNS would have produced a different abundance of light elements to that which we observe in the universe (roughly 75% H, 25% He, and a smattering of Lithium).  The dark matter can't all be MACHOs without chucking this out of the window.  That's part of the reason WIMPs are favoured.  (Obviously, brown dwarfs and black holes and such do exist, just not in large enough quantities to explain the rotation curves etc.)  --81.158.2.129 (talk) 16:05, 5 September 2010 (UTC)


 * It's Dust in Lyra's world. 67.243.7.245 (talk) 18:53, 5 September 2010 (UTC)


 * if the universe is in black hole we feel the flip of the arraw of time in the age and gravity start to push . thanks . —Preceding unsigned comment added by 77.124.170.151 (talk) 15:07, 6 September 2010 (UTC)

Why can't I just get a local orthodontist to readjust braces installed in India?
Here, I asked about why we can't just fly to India to get braces, since they're far cheaper there than in the US.

Someone thinks I have to fly back every few months for a readjustment. What kind of aggravating joke is that? It's like buying an SUV at the Little Apple Toyota Honda dealership in Manhattan, KS and if it breaks down in Seattle while on a vacation, it has to get towed all the way back to Manhattan to get fixed. It doesn't work that way; the vehicle gets fixed at the closest local service center.

So why didn't somebody think that we can readjust our Indian-installed braces at the orthodontist nearest me? --70.179.165.170 (talk) 07:12, 5 September 2010 (UTC)
 * There are plenty of confused people in this world, and people say plenty of silly things on the internet for a large variety of reasons. In other words, there's no way we can tell you why the person said what they said. Your best bet is to ask them if you really want to know. In any case, it's possible you misunderstood what the person was saying. Perhaps they were suggesting that braces aren't necessarily a one time thing but rather may require ongoing support and adjustment. Therefore you will need to go to someone for this, either the person who installed them or someone else. In any case, this will add to the cost and if you do go to someone else, I would guess it not unusual you will be charged extra. Also if the braces are a different kind and the dentist isn't used to dealing with them, this may also add to the cost. In other words, your cost savings may not be as big as you think from a simplistic analysis Nil Einne (talk) 11:35, 5 September 2010 (UTC)

Carbon steel
is carbon steel magnetic —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 08:59, 5 September 2010 (UTC)
 * I think it is magnetic, but the answer must be somewhere on this page --Stone (talk) 09:15, 5 September 2010 (UTC)


 * Carbon steels display ferromagnetism. Dolphin  ( t ) 11:33, 5 September 2010 (UTC)

Quarks
many sources i have read includes mass of QUARK in Mev which is hopefully unit of charge.Kindly anyone having knowledge of this subject answer. thanks in advance sameer,india 59.93.129.150 (talk) —Preceding undated comment added 09:59, 5 September 2010 (UTC).


 * MeV is mega electron-volt which is a unit of energy, not of charge. Mass is related to energy through Einstein's E=mC2.  Energy is often used as a measure of mass by particle physicists since this is the energy that they must impart to a collision in order to create the particle in question.  Sp in ni  ng  Spark  10:08, 5 September 2010 (UTC)
 * In atomic physics mass and energy are freely mixed. 1 electron-volt is the amount of energy need to move one electron against 1 Volt. 1 Joule (or watt-second) is the amount of energy need to move 1 Coulomb of electrons against 1 Volt. The typical energy of a photon of light is around 2.5 eV. 1 MeV is around 0.001 atomic mass units, where the mass of 1 carbon atom is 12 amu. CS Miller (talk) 15:59, 5 September 2010 (UTC)
 * ... and, in case you were wanting to know about quarks and haven't read our article, the charge of a quark is either one-third or two-thirds of the charge of a proton, and the mass of a quark is only a tiny fraction (0.4%) of the mass of the proton that it is part of. The remainder of the mass of the proton comes from the "kinetic energy" of the gluons that keep the quarks together, and from their binding energy.    D b f i r s   16:48, 5 September 2010 (UTC)


 * In physics, we have very well defined units for measuring all kinds of things. And, we have very effective applicable physical laws that relate different quantities together.  So sometimes experimental physicists muck up the works by using the "wrong units."  But rest assured - their weird units are okay given two things: (1) knowledge of the physical relationships between parameters; and (2) knowledge about any assumptions in the experimental apparatus.
 * In the simple case of, say, weighing a person, we want the person's mass; but we can really only measure their weight (in a reasonable classroom kind of setup). So, we put the person on a spring scale (on Earth and subject to one unit of Earth gravity, g.  In this specific case, we can say that "force=mass⋅acceleration" with very little loss of accuracy or correctness.  So, we often find people describing their weight or their mass interchangeably - because under "normal laboratory conditions" (for the specific scenario we care about), [pound]]s are directly related to kilograms by a simple relationship.  And, we find it convenient to use "pounds" as a unit of "mass" - even though it's not technically right - but that's what the scale reads off to us (and we all know that we can perform the conversion).
 * We can go a step farther. The scale can't actually measure a force - we're really measuring a compression of the spring inside the scale!  By Hooke's law, we know that spring force is linearly related to the distance displaced; and we can simply relate spring force to mass; and we could have a standard spring-scale - so we could actually measure a mass in meters - even though mass is not measured meters!  What we would do is measure how many meters (Δx) the person deflected the scale; and then multiply by the spring constant (kspring) of the scale; and then assume they were on Earth; and say their mass exactly equals Δx*kspring/g.  Or we could say "the mass was Δx meters" - a bit of sloppy shorthand and not really correct; so we can invent a unit called meters-standard-spring-constants-per-Earth-gravity (m ks/g).  Now we can read standardized-scale deflections Δx and mark the scale in m⋅ks/g.  In fact, this is more "correct" than reading off the scale units in kilograms or pounds - because we're directly observing a displacement in meters, and this unit reminds us that our conversion to mass depends on all the implicit assumptions above.  If our spring-scale changes, we can keep using the same units and just change the conversion factor from meters to mass.
 * In subatomic physics, we have similar relationships - for example, mass-energy equivalence. This is a special property that (under certain conditions), mass and energy can be converted.  In the case of experimentation with quarks, we don't have a lab scale: we have sophisticated experiments called deep inelastic scattering probes inside a machine called a Linear Particle Accelerator - and it so happens that the results of these scattering experiments will be read off in units of energy.  In analogy to the way that we can measure a person's force on a scale to infer their mass, given the conditions of "standard Earth gravity" - we can measure an energy release to infer a mass, assuming a perfect "E=mc2" style conversion.  So, we can use the units of Energy and Mass interchangeably.  It so happens that the way we will measure "energy" in a high-energy particle accelerator is by measuring a voltage - say, on an avalanche photodetector or a BaBar - so it makes perfect sense to measure "energy" in units of "electron-volts" (it makes the job a bit easier for the semiconductor physicist who has to do the instrument design).  We use derived units, like the electron volt (and in fact, even the volt - which is a kilogram-per-couloumb times a meter squared per second squared), to make the mess easier to read.  And, while in the simple laboratory experiment, we never have to worry about the 9.81 m/s/s "changing" - in high-energy physics, we might need to consider what happens if a new discovery "recalibrates" the coulomb, or the joule, and so on - so it's nice to be able to handle that complexity with our choice of units.  Nimur (talk) 18:07, 5 September 2010 (UTC)

Silicone Caulk
why is Silicone Caulk not typically paintable? what happens if you paint it? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 11:05, 5 September 2010 (UTC)
 * I'm pretty sure the paint will just fall off as soon as it dries. Looie496 (talk) 18:04, 5 September 2010 (UTC)
 * In order to paint it, the paint has to stick, and silicone caulk is just not sticky. Another option is a textured surface, so the paint fills little holes - but silicone caulk is very smooth. So you can't paint it (with ordinary paint anyway). Ariel. (talk) 18:25, 5 September 2010 (UTC)

What kind of spider is this?
Hi. I just wondered if anybody could help me identify |this spider please? It was found in a house in London, and I think that it might possibly be a False Widow, judging by the markings on its back. However, I am not sure that the body shape and legs are quite right for a False Widow. Any help would be greatly appreciated. Thanks Spider788 (talk) 11:28, 5 September 2010 (UTC)
 * I have posted a second video | here. Thanks Spider788 (talk) 16:09, 5 September 2010 (UTC)
 * Looks like a Tegenaria species to me - see . And it's a male (you can tell by the pedipalps - the two little "clubby" things at the front), out looking for a female - it's the mating time of year. -- Boing! said Zebedee (talk) 21:03, 5 September 2010 (UTC)


 * If not Tegenaria, most likely something in the Araneomorph_funnel-web_spider family. SemanticMantis (talk) 02:40, 6 September 2010 (UTC)

Does http://tineye.com ever help with these sorts of questions? Why Other (talk) 22:26, 6 September 2010 (UTC)

Development of the insulin unit (copy request)
Request Moved to: Wikipedia Resource Exchange/Resource Request. --Seren-dipper (talk) 17:35, 5 September 2010 (UTC)

Estimate of number of generations since origin
Has there ever been made an estimate of the number of generations that has happened since the origin of life?

I would guess that the Last universal ancestor would have an extremely low reproductive age, and from the linked article it seems like the length of a generation for the LUA could not be determined with any accuracy. Still, has anyone tried? Xelnaga diku (talk) 15:58, 5 September 2010 (UTC)


 * I doubt it's even meaningful. For 3 billion years of the 4 billion year history of life there was nothing more than bacteria, archaea, and protista of various sorts, which can reproduce in less than a day but can also generate spores that lie dormant for potentially thousands of years before reproducing.  The best one can say is billions of generations at minimum. Looie496 (talk) 16:12, 5 September 2010 (UTC)
 * We can put some bounds on the estimate with a few assumptions. It is believed that LUCA lived 3.5–3.8 billion years ago. So for our upper bound on the numer of generations, let's take 3.8 billion years ago and a reproductive cycle of one hour: that makes 33 generations. For the lower bound, let's take 3.5 billion years ago and a reproductive cycle of one day (much longer than most modern bacteria): that makes 1.3 generations. So we can say with reasonable confidence that the number of generations since LUCA is in the fairly low trillions, but quite possibly in the low tens of trillions. Physchim62 (talk) 18:56, 5 September 2010 (UTC)
 * A number like that is kind of hard to relate to. Is there any estimate on the number of human generations on average, in some more recent stretch? For example, in my ancestry tree, who has been traced about 400 years back, there are about 13 or 14 generations, or about 30 years per generation. I just wonder if 25-35 is a good rule of thumb for the last 2,000 years, perhaps? ←Baseball Bugs What's up, Doc? carrots→ 19:10, 5 September 2010 (UTC)
 * Yes - although our article surprisingly doesn't mention a rule-of-thumb length. Ghmyrtle (talk) 19:24, 5 September 2010 (UTC)
 * Wikiscient (talk) 21:26, 5 September 2010 (UTC)
 * 25 years is a reasonable rule-of-thumb scale for a human generation, although it is impossible to define a "generation" across a whole population. On that basis, Homo sapiens came into existence about 200,000 years ago, so that makes 8000 generations. Physchim62 (talk) 21:06, 5 September 2010 (UTC)

Confusion regarding electricity
Hello, I am currently somewhat confused as to what "electricity" actually is. I will attempt to explain my current level of understanding which contains a ridiculous amount of contradictions, so that you can perhaps see why I am so confused and explain it a little better.


 * It's a type of low-frequency radio wave, yet it is apparently made of protons.
 * It is a mysterious force which looks like blue-white fire, and yet cannot be seen.
 * It moves forward at the speed of light... yet it vibrates in the AC cord without flowing forwards at all.
 * It's totally weightless, yet it has a small weight.
 * When electricity flows through a light bulb's filament, it gets changed entirely into light. Yet no electricity is ever used up by the light bulb.

Regards, --T.M.M. Dowd (talk) 17:49, 5 September 2010 (UTC)


 * It would be encouraging if you would give some indication that you had tried to read our electricity article. Looie496 (talk) 18:00, 5 September 2010 (UTC)


 * Yes I have read through the article previously. Upon viewing it again, the phenomenon I am having difficulty in understanding is "electrical potential". My apologies for having not been clear about this earlier. --T.M.M. Dowd (talk) 18:08, 5 September 2010 (UTC)


 * It's not a radio wave, and it's not made of protons, but rather electrons (but of course telling you the name doesn't tell you what it is.) It does NOT look like blue white fire. Blue white fire is the color of hot AIR. If you heat air by any means, it will look like that, a lighting bolt in space has no color at all. The flame of a natural gas stove is also blue - for the same reason: it's hot.
 * Here is the main source of your confusion (I think): Electricity is carried by electrons, but it is not the electrons themself! So when electricity goes through a filament, the electrical energy gets converted to light, but the electrons, which carry the energy are unchanged. In an A/C current the electrical energy travels at the speed of light from one electron to the next - but the electrons hardly move. This energy can be considered weightless, and it can change direction quickly (but not infinitely quickly, but let's skip that for now). The electrons, which carry the energy do have weight. (Technically the electrical energy has weight too - E=MC2, but let's skip that too.) Did I answer everything? Feel free to ask again. A lot of wikipedia articles are written by in a way that is hard to understand unless you already understand the topic. It's hard to write an encyclopedic article any other way since you don't know the level of the student. Ariel. (talk) 18:16, 5 September 2010 (UTC)


 * On your user page, you say you have an A* in GCSE Science and a B in AS Physics. Did you seriously not cover any basic concepts like voltage and current? --81.158.2.129 (talk) 18:21, 5 September 2010 (UTC)
 * Of course those topics were covered. We learned how to use equations such as Ohm's law and the resistivity equation, but not really what electricity was in its most fundamental form. --T.M.M. Dowd (talk) 18:36, 5 September 2010 (UTC)
 * If you connect light bulb to light bulb so one uses the other one's waste electrical current, they both will be very dim. All of the energy was used up. --Chemicalinterest (talk) 18:22, 5 September 2010 (UTC)


 * "Electricity" in common parlance loosely refers to both the actual flow of electric current, and to the use of electric current to deliver energy to devices. Because electric current and energy are both invisible (we only see their effects, like incandescence), many people incorrectly think they are the same.
 * In fact, what you need to know is that there are small particles called electrons, that carry electric charge. Other particles, called ions, can also carry charge, but this doesn't happen inside a copper wire.  When charge-carriers move, we call this electric current.  We can use and control this motion to carry energy from place to place - to power devices like lightbulbs.  We can also use this energy to create electromagnetic waves that carry information - and use this to transmit data, sound, pictures, and so on.
 * Another common misconception is about the speeds. Electrons do not move at the speed of light (in fact they move very slowly when inside a copper power-cord).  But the energy that they are conveying does (or can) move as fast as the speed of light.  Again, this is because energy is not the same as electric current.  The way that energy and electric current are related is explained by Maxwell's equations and the Lorentz force equation; it requires some complicated math, but what you need to know is that the energy can move at a different speed than the individual particles that are conveying it.  In fact, it is even possible to convey energy without any current - because electromagnetic waves can travel through vacuums - they do not need electrons to carry them.  We use copper wires (and therefore, electric current) to guide the electromagnetic energy to the place we want it to go - like to your lightbulbs.
 * "Electric potential" is a measure of the relation between energy and current - when a potential exists, it means that individual electrons have the energy to move from one place to another - this is what drives them through a wire or a circuit. Nimur (talk) 18:25, 5 September 2010 (UTC)
 * I'm trying to decide whether electricity can be seen as a guided electromagnetic wave, as you suggest above, and I think the answer is no. In a steady-state DC circuit consisting of a battery driving a lamp, there are no time-varying fields. To the extent that electrons are quantum particles, I suppose there is a tiny time-varying field, but electricity still works in the classical limit where it's carried by a continuous fluid. -- BenRG (talk) 00:55, 6 September 2010 (UTC)
 * Hm. That's a very good point.  In the case of DC current flow, how exactly is power transferred?  The battery produces a voltage; and the voltage entices a current to flow across a resistance; and power is transferred from the battery to the load.  The individual charge-carriers are doing work on the load - e.g., by adding thermal energy to it, in the case of a light-bulb.  But in this case, all of the energy is actually carried by the charge-carriers, and none of the energy is carried in the form of a wave (I think.... Could a DC or "zero-frequency" wave convey energy?) .  I think the case of the AC current has some energy carried by the charge-carriers, and the rest carried by the electromagnetic wave; and the final case, an electromagnetic wave in free space, has all the energy in the wave, and none in the form of moving charge carriers.  I have to think about this some more; but I think the answer is that energy can be conveyed by either the moving electrons, or the electromagnetic wave, or both.  Nimur (talk) 07:17, 6 September 2010 (UTC)
 * I had to think about it too, but I'm pretty sure this is the answer: in the half of the circuit where the charge carriers are heading from the battery to the load, they're under pressure and hence a bit closer together than they would otherwise be, so there's a small net charge on this half of the wire, which produces a radial electric field. There's also a magnetic field, of course, and the cross product of the two (the Poynting vector) is parallel to the wire and points in the direction of the load. In the other half of the circuit the charge carriers are under tension, so there's a slight charge of the opposite sign, and the current is also in the opposite direction, so the Poynting vector again points toward the load. So the energy is carried by the EM field (outside the wire!), even though it's static. Maybe this does deserve to be called an EM wave. -- BenRG (talk) 08:41, 6 September 2010 (UTC)
 * You might find the hydraulic analogy useful. In short, electrons (or other charge carriers) are like water, wire is like a pipe, voltage (or potential) is like pressure, current is like current, a battery is like a pump, and a light bulb is like a paddlewheel driving a mill. It's a close analogy. If you start a pump at one location in a sealed loop of pipe, a paddlewheel at another location will start turning almost immediately, even though it takes much longer for the water that was initially in the pump to reach the paddlewheel. What gets transmitted quickly is the pressure, not the water itself. If you run the pump alternately forwards and backwards, the paddlewheel will turn alternately forwards and backwards and that can also be converted into useful work (by a slightly more complicated mechanism) even though the water in the pump never reaches the paddlewheel in that case. The water remains in the pipe and is not produced by the pump or consumed by the paddlewheel. -- BenRG (talk) 18:35, 5 September 2010 (UTC)

Truck with a 3d picture on it - is it possible in reality ?
Perhaps you`ve seen those images with truck photoshoped so that it appears to be transparent with large three dimensional object inside (if not just google 3d truck ) Last year I had a course in advertising and in oe class we were asked to find good ads vehicles, I offered these as currious example, but most people thought it wouldn`t be usable as acctual ad because the ilusion would work only in this one angle. I`ve seen some videos with 3d street paintings that look crap if not viewed from certain angle. However I wonder if there might be some instances when this would work (like the pepsi boxes or those with ilusion only on side of the car) i.e. it would look 2d from other angles, but wouldn`t be misshaped ? Also from what viewpoints would this illusion be visile ? Xil (talk) 19:55, 5 September 2010 (UTC)


 * If you are talking about pictures that create a 3d appearance by leveraging optical properties (like sidewalk pictures) then those would only work from one narrowly defined angle. you might be able to leverage some of the old-school multi-image effects (the kind used on kids' playing cards, where tilting the card displays a succession of images), but I've never seen it done using 3d images.  You could always, obviously, produce a hologram.  -- Ludwigs 2  20:53, 5 September 2010 (UTC)
 * No, I specificly mean practical application on trucks, certainly nothing like those cards, please see the pictures in question. I mentioned street painting only because it looks distorted from other angles - 2d look would be acceptale, distorted would not  Xil  (talk) 21:35, 5 September 2010 (UTC)


 * You can't do it for an arbitary viewpoint without some tricks. I've seen U-Haul trucks where the tailgate is painted with a fairly convincing picture of the interior of a truck - and it works well when you're driving along behind one.  They've obviously set up the perspective of the thing to make it look right from that most common situation.  If you watch the back as you overtake it - it looks distorted.
 * There are a few (very few) tricks that might get you a little further - but almost all 3D view tricks are either sensitive to your position - or require the viewer to wear some kind of headgear (like the 3D glasses in movie theatres).  The only tricks I know of that work without glasses are:
 * Autostereoscopy - which relies on tiny lenses molded into the surface of the picture to (typically) direct the light from alternate thin vertical strips of the underlying image off in different directions. By drawing the picture as corresponding alternating thin vertical strips from multiple pictures you can arrange for viewers to see different images depending on where they are standing.  Done carefully, this works to a degree - but not perfectly.  There are places you can stand where you'll get some light from one image and some from the next one along - and you get a blurry double-image that's not too convincing.  You see this trick used in a lot of cheap children's toys - and it used to be popular for making "3D" postcards.
 * Holograms - these are expensive to make in large sizes. They also only work well when the lighting is good.  Worst of all, they don't work in color very well.  So I can't imagine them being much use on a truck.
 * There are some odd tricks that rely on the fact that your eyes focus different colors at slightly different depths. I've seen some moderately effective tricks done using this technique - but they are very viewer-position dependent - and the 3D effect is at best rather mild.
 * There is a theoretical possibility that some kind of system could recognise where the human viewers heads were and using (for example) multiple lasers, send a tiny rasterized image directly into that persons eyes. Each image would be calculated using computer graphics to be just the right view of the object for each eye.  It would take a lot of lasers to convince a whole crowd of people though - and the precision of the head tracking software would have to be amazingly good.  This is still more in the realms of science fiction than actually real.


 * So - I think the answer is "No" - you can't do this. What you've been seeing is either a carefully posed single-person view - or a highly faked movie! SteveBaker (talk) 22:14, 5 September 2010 (UTC)


 * The images Xil is talking about are obviously photoshopped (and Xil knows it). They all show the same truck from the same angle against the same background. At most one of them might be real. -- BenRG (talk) 00:42, 6 September 2010 (UTC)


 * I think the OP is talking about images like this, right? Similar to what Steve mentions having seen on U-Hauls.  Looks "real" to me (from that angle)!  And, clearly, yes, someone is using that as an advertising gimmick -- don't know why the OPs classmates would have wanted to shoot down such a thing -- the (non-"gimmick") advertising is still effective from any angle.  Wikiscient  (talk) 05:39, 6 September 2010 (UTC)


 * Here are other photoshopped versions of that same image:                     . Apparently they are all submissions to the Rhino Rolling Advertising Award. -- BenRG (talk) 07:24, 6 September 2010 (UTC)


 * Even if the image only worked from one angle, it would still be an amusing novelty. An early example is The Ambassadors (Holbein). See anamorphosis. 92.15.7.161 (talk) 09:44, 6 September 2010 (UTC)
 * Anamorphosis does seem promising, thanks. My thinking was that some of the photoshoped trucks would look weird - think what only the side or only the back of truck would look like, if only part of the image is painted on (like the one with the beer bottle), however some, such as the truck with pepsi boxes upside down and the one that looks like a bag, don't have split images. So I would imgine that if say pepsi boxes look 2d, but not distorted and you suddenly would note that as you pass by the truck it turns 3d, it would grab your attention, which is just what advertiser needs. Also I've seen some paintings on a single plane, that are not streched, but do give pretty convincing ilusion (I'm not sure though if tehnicaly it is considered 3d, they give ilusion of depth and I suppose shading on object takes care of the rest) Xil  (talk) 01:14, 7 September 2010 (UTC)
 * You are referring to Trompe-l'œil. 92.29.115.74 (talk) 12:52, 7 September 2010 (UTC)
 * Thank you all for answers, now I certainly have some idea which techniques to research further :) Xil  (talk) 08:16, 9 September 2010 (UTC)

protein
In vegetarian stuff where does the protein come from? Calm Minds (talk) 20:45, 5 September 2010 (UTC) Calm Minds (talk) 20:45, 5 September 2010 (UTC)
 * Often from any variety of legumes (beans, peas, etc.) ··· 日本穣 ? · 投稿  · Talk to Nihonjoe ·  Join WikiProject Japan ! 20:51, 5 September 2010 (UTC)
 * Nuts HiLo48 (talk) 21:04, 5 September 2010 (UTC)
 * see Vegetarianism RJFJR (talk) 21:08, 5 September 2010 (UTC)
 * All plant material contains protein. The problem is with the kind of protein.  Proteins are made of amino acids - the human body can consume 22 different amino acids - of which 8 are 'essential' to maintaining your bodies structures and biochemistry - and the other 14 are mostly broken down for energy.  You can't live long without having adequate quantities of all 8 of the essential ones.  You can live without the unessential ones providing you have enough carbohydrate and fat to provide the necessary energy input.


 * And that's the problem. There is protein in all kinds of plants - but only a few kinds contain all 8 of those essential amino acids.  Meat, fish and eggs have all eight - so people who are not vegetarians (or those pseudo-vegetarians who eat fish, eggs or dairy product) have easy ways to get all they need without taking too much care of it.  But for a 'pure' vegetarian, it would be perfectly possible to come up with a diet that was missing one or more of the those essential building blocks - and that would be "A Bad Thing".  So the trick is to come up with enough of those rarer foods that have all 8 - or to devise a diet that has a suitable combination of plants that covers those 8.  SteveBaker (talk) 21:51, 5 September 2010 (UTC)


 * That's basically right but let me make a couple of small corrections. Human proteins are made of 21 amino acids.  Eight of them must be obtained in the diet; the other 13 can be synthesized by the body.  They are just as necessary, and aren't broken down for energy unless they are present in excess quantities -- it's just that they don't need to be eaten.  See our article on essential amino acid for more information. Looie496 (talk) 22:23, 5 September 2010 (UTC)
 * For example, Lysine is typically not very abundant in grains, so people getting most of their calories from cereal crops are typically deficient in it. This can occur in people who choose to be vegetarians and aren't very smart about it, but it's also a problem for people in (generally poorer) parts of the world whose diets are limited by poverty to consist primarily of cereal crops.  Vegetarians who are smart enough to realize this often eat Legumes, which contain plenty of lysine (but generally lack some of the other essential amino acids, like Methionine). Buddy431 (talk) 23:27, 5 September 2010 (UTC)
 * I should note that I've never heard of a multicellular species that could do without at least the "standard" 20 amino acids in its cells. When plants are described as a poor source of essential amino acids, it doesn't meant that any of these are entirely absent, only that they're not available in the most efficient amounts for nutrition. Wnt (talk) 07:19, 6 September 2010 (UTC)
 * Eating too much protein may be bad for you, see Protein_%28nutrient%29. I believe most adults in the West consume more protein than they need, and it is converted to energy. It used to be thought that you needed to consume cereals and legumes in the same meal, but now that is thought not to be true. See http://www.ajcn.org/cgi/reprint/59/5/1203S.pdf 92.15.7.161 (talk) 10:01, 6 September 2010 (UTC)

Hilarious cupcakes
Are there any foods which induce laughter? Fiorsless3 (talk) 21:32, 5 September 2010 (UTC)
 * This would require the food to contain some substance that causes laughter, some might be listed here, mix them in cupcake dough and see what happens Xil  (talk) 21:43, 5 September 2010 (UTC)
 * How about Lime Jello Marshmallow Cottage Cheese Surprise? Looie496 (talk) 22:27, 5 September 2010 (UTC)
 * I don't know about food, but see Inherently funny word. Ariel. (talk) 23:52, 5 September 2010 (UTC)
 * Obviously magic brownies come to mind... ;) Wnt (talk) 07:30, 6 September 2010 (UTC)
 * Whipped cream made with nitrous oxide? Or maybe anything at thisiswhyyourefat.com. Smartse (talk) 16:53, 6 September 2010 (UTC)
 * The pictures at thisiswhyyourefat.com made me want to vomit, not laugh. -Atmoz (talk) 19:28, 6 September 2010 (UTC)

van't Hoff factor problem
A solid consists of a mixture of NaNO3 and Mg(NO3)2. When 6.50 g of the solid is dissolved in 50.0 g of water, the freezing point of the solution is lowered by 5.15 degrees C. What is the composition by mass of the solid?--74.232.4.49 (talk) 22:16, 5 September 2010 (UTC)

How many grams are there of NaNO3 and Mg(NO3)2?--74.232.4.49 (talk) 22:19, 5 September 2010 (UTC)
 * We won't do your homework for you, sorry. Regards, --— Cyclonenim | Chat 00:52, 6 September 2010 (UTC)


 * You might find inspiration at Freezing point depression.  Dolphin  ( t ) 04:13, 6 September 2010 (UTC)


 * You have to find out the decrease in temperature that each solid gives. Then use an equation to figure out by all the data. --Chemicalinterest (talk) 10:58, 6 September 2010 (UTC)