Wikipedia:Reference desk/Archives/Science/2011 September 3

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September 3

Oxygen and cancer

Hi. I read somewhere that when normal cells are starved of oxygen, their metabolism changes to glycolysis through the Warburg effect and the normal self-destruct mechanism based on mitochondria stops, thus making these cells cancerous. Does this mean that any oxygen starvation of tissues, for example through ischemia or mountain sickness, automatically increases the risk of cancer? Finally, does sleep deprivation reduce the amount of oxygen to organs and various parts of the human body? Thanks. ~AH1 ^(discuss!) 00:15, 3 September 2011 (UTC)

If oxygen tension is too low to support mitochondrial activity, the cell will not have enough energy to divide, or even survive for long. Furthermore, the buildup of fermentation products would damage the cell. Cell death and tissue necrosis would be the result of prolonged hypoxia, not cancer, which is essentially uncontrolled cell proliferation. As to your second question, I don't see any mechanism by which sleep deprivation can cause hypoxia per se. Dominus Vobisdu (talk) 09:25, 3 September 2011 (UTC)

Consider the partial oxygen starvation scenario.Electron9 (talk) 02:05, 7 September 2011 (UTC)

Ruptured star

Is it possible for a star to sort of "pop" and expel its contents through the rupture via its own gravity (kind of like a balloon bursting when you squeeze it)? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 00:19, 3 September 2011 (UTC)

Nova,Supernova, and Hypernova are the known ways stars can "pop". Dauto (talk) 00:24, 3 September 2011 (UTC)

Also see Polar jet and Coronal mass ejection and Gamma-ray burst for different phenomena which may meet what the OP is talking about... --Jayron32 00:29, 3 September 2011 (UTC)

The question implies that a star has some "membrane" keeping it intact. Usually, the opposing forces of gravity (keeping the star from exploding) and internal pressures (keeping it from swallowing itself) keep the star in equillibrium. Sometimes in core collapse events, the star will start to implode, superheat and reach an outward pressure exceeding the gravitational force, and thus shedding its layers in a way somewhat similar to a balloon popping. It is the internal gravity, not an external membrane, that keeps the star together. Although the transition from a red giant star (similar to the Sun in late stages) to a white dwarf is commonly described as the star "shedding its outer layers", it in other words explodes. The presence of heavy elements such as carbon and oxygen in high amounts causes the star's pressures to exceed its gravity, ejecting its atmosphere. ~AH1 ^(discuss!) 00:31, 3 September 2011 (UTC)

I meant if it can rupture and through its own gravity squeeze out the contents of its super-high-pressure core followed shortly by the rest of the star. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 15:41, 3 September 2011 (UTC)

Gravity can indeed push things up, when something else is heavier and pushes down to displace them. Such convection is a part of stellar structure. As you can see, various sorts of stars have different areas where there is a convection of material. But what's really, really weird that I learned in a previous discussion here is that the core of a sun actually doesn't turn over with everything else, not even in the end as the star is used up. It just sits there, like Tantalus, immersed in a sea of hydrogen from which it cannot drink, until from lack of fuel it collapses in on itself and explodes. Then all that unused hydrogen is blown out to recondense and make new stars. A strange tragic poetry in space. Wnt (talk) 17:01, 3 September 2011 (UTC)

Rotor and propeller vs. cylinder

Why are rotors and propellers used instead of a cylinder, which could compress the water or air? What makes those solutions more efficient than the latter? Quest09 (talk) 00:25, 3 September 2011 (UTC)

Water isn't compressable. --Jayron32 00:29, 3 September 2011 (UTC)

You mean it's difficult to compress, right? Anyway, you can push it with a cylinder, and make a vehicle move forward. Quest09 (talk) 00:36, 3 September 2011 (UTC)

No, it is essentially uncompressable. The atoms are already at essentially maximum density, you can't actually push them any closer together. --Jayron32 01:10, 3 September 2011 (UTC)

Of course what Jayron means is that you can't push them much closer together at any reasonable pressure. Water does have a bulk modulus; it will compress a little bit. And if you use truly extreme pressures, it will compress a lot (it's not anywhere close to electron degenerate matter, much less neutron degenerate matter). --Trovatore (talk) 01:14, 3 September 2011 (UTC)

Yes, true, but for the application of what the OP is looking for, we can treat water as uncompressable. The reason things like jet engines and turbo chargers and superchargers work in air is because air is very compressible; essentially you get a direct relationship between decreased volume and increased pressure (Boyle's law). Water doesn't work that way. Yeah, it is in a very small way, compressible in the sense that with some massive pressures, you can get minute changes in volume, but not in ways that make it anything like an effective means of propulsion akin to a jet engine or something like that. For the purpose of this application, you can assume it as essentially uncompressable (to a first approximation). --Jayron32 01:29, 3 September 2011 (UTC)

Used for what? ~AH1 ^(discuss!) 00:31, 3 September 2011 (UTC)

They are used for moving a vehicle forward. Quest09 (talk) 00:36, 3 September 2011 (UTC)

So your idea is to compress water in a cylinder, then release it out the back to propel a Ski-doo-type vehicle forward ? It wouldn't work very well. As was said, water isn't very compressible. Then there's the problem of this method providing a putt-putt motion instead of smooth movement. StuRat (talk) 01:17, 3 September 2011 (UTC)

Could someone explain how a cylinder would be used for propulsion? Are we talking about something like a turbine? Dismas|^(talk) 01:42, 3 September 2011 (UTC)

I think he's thinking along the lines of a Hydraulic cylinder, but I'm not sure how such a device could make an efficient propulsion system... --Jayron32 01:45, 3 September 2011 (UTC)

Now, if you make it a pneumatic cylinder, and use it to launch a projectile, then that sounds more practical. I believe some children's toys work like that, and it might be practical for other applications, like launching unmanned airplanes. StuRat (talk) 01:53, 3 September 2011 (UTC)

Well yes, but then we're back to air again, but the OP is interested in water propulsion. There are water-based "jet" engines, like the Pump-jet, but these don't rely on compression; they are basically just encased propellers which are optimized for higher RPMs and more directionality, and with a constricted output, akin to putting your thumb over the garden hose. Still not proper "compression", but they do provide thrust by pressurized water. --Jayron32 04:00, 3 September 2011 (UTC)

Thanks so far. Yes, that would answer why we don't do it for using water for propulsion: it is not compressable. However, if we use a pump to compress air to move a vehicle on water, air or even on a road, would that be much less inefficient than a rotor on air or a propeller on water or a tires on the floor? Quest09 (talk) 12:07, 3 September 2011 (UTC)

Due to the low density of air, you need to move a lot of it quickly to move an object. This is best accomplished by a giant fan, as in an airboat. StuRat (talk) 17:58, 3 September 2011 (UTC)

Is the OP asking about the advantages of axial flow pumps over reciprocating positive displacement pumps for purposes of propulsion? Our article on the former states that they are more suited for low heads and higher discharges.-- 110.49.242.30 (talk) 05:49, 3 September 2011 (UTC)

From a practical point of view, in the simple piston/cylinder arrangement, the velocity of the piston is not constant, so the output would be in spurts leading to a jerky ride on a boat (this would also cause more fluctuating stress on the components, metal fatigue, etc.). Whereas proplelars give constant thrust (almost). Of course a hydraulic accumulator would help to smooth this out even in high pressure systems (as used by the London Hydraulic Power Company), as would double acting, multiple cylinders. So, other design conspts have proved superior mainly for these reasons. --Aspro (talk) 12:38, 3 September 2011 (UTC)

Similar to multiphase electricity, wouldn't it be possible to combine 2 or more pumps for continuos output? Gasoline pumps seem to have piston pumps inside, and provide pretty steady flow. Edison (talk) 20:28, 3 September 2011 (UTC)

Thinking about it, I can't quite see why a pressurized tank of water shouldn't work, even though just thinking about it it seems ridiculous. I mean, if you pressurize the tank one microliter at a time, I picture a piston moving a distance against great force, just as if you were filling an air tank with a bicycle pump. I'd think when you get to the same pressure, you've done the same amount of mechanical work. So there should be the same amount of propulsive energy in the tank waiting to be tapped. And yet... Wnt (talk) 19:28, 4 September 2011 (UTC)

... and yet you've not done the same amount of work, because while you wind up with the same force, you push the pump handle through much less distance. It will take many strokes of your pump to pressurize the tank with air as the pressure rises slowly, but only a small fraction of a stroke to pressurize the tank (already filled with water) with that microliter of additional water needed to rapidly reach your target pressure. Work = force * distance = pressure * volume (but in both cases you need to integrate the incremental work to take into account the changing force). Thus compressed gas is used in pressure accumulators where you wish to store a lot of energy, and a gas cylinder (such as a scuba tank) is totally filled with water during hydrostatic testing so that relatively little energy will be released if it ruptures. -- 110.49.250.48 (talk) 12:56, 7 September 2011 (UTC)

Jupiter sized object crashing into Sun

Hi, suppose an object about 1/1000 the mass of the Sun came from interstellar space and hit a bullseye with the Sun at 200miles/sec?Would there be brief fusion at sun's surface? Would the sun be changed drastically in some way? Would life on Earth be destroyed? What if we tweaked the mass and velocity of the object up and down?...It seems to me tha if impact of a comet or asteroid with Earth is probable enough to be at least a minor worry nowadays, an impact on the sun with a larger object could be a minor possibility, if not a worry. 200miles/sec seems reasonable, since Earth revolves around sun at 18miles/sec, and object is supposed to go straight toward sun from a long way--no need for it to have a closely comparable velocity.Thanks24.7.28.186 (talk) 03:47, 3 September 2011 (UTC)

You mean aside from completely throwing the earth out of its orbit before it ever got to the sun? --Jayron32 04:01, 3 September 2011 (UTC)

If it came from the other side, I don't think it would affect the Earth's orbit very much. Of course, I'm not sure how much it would take....

In response to the OP's final sentence, though, that's really not true. The kinetic energy of an object in a circular orbit is half the energy it needs to escape, which means escape velocity is only square-root-of-two times larger. If the Sun pulls an object in from infinity, it hits at the escape velocity, so around 25 mi/sec if the OP's numbers are correct.

Of course if it doesn't get its velocity by falling into the Sun, but simply because it was already going fast, then there's no special limit. But then the odds against it hitting the Sun are large; if it's a little bit off, it just makes a hyperbolic path past the Sun and heads back into interstellar space. --Trovatore (talk) 04:07, 3 September 2011 (UTC)

Unless it hits the corona, its slowed down by friction, and it falls into the sun. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 15:44, 3 September 2011 (UTC)

Whoops, now that I think about it, that's the escape velocity from the Sun at the radius of the Earth's orbit. The escape velocity at the surface of the Sun would be a lot larger. About 15 times as large if my calculations and quick googling are right. So could be on the order of 350 to 400 mi/sec. --Trovatore (talk) 04:11, 3 September 2011 (UTC)

Sure the object could come in while the Eath is on the other side, or more generally from out of the ecliptic entirely. How much time would an oject that fast to meaningfully perturb Earth's orbit?...I think most comets that get in close must be going very fast at that point...Are the odds of a hefty object hitting the sun, in a 10 million year span, say, really so small? Thanks again.24.7.28.186 (talk) 04:20, 3 September 2011 (UTC)

As far as we know, there just aren't any Jupiter-sized objects anywhere near the Solar System, except for Jupiter. And it seems to be staying put. --Trovatore (talk) 04:30, 3 September 2011 (UTC)

If it's interstellar, and going "fast", it wouldn't be "near" until "shortly" before. But come on you guys! :-) I said what if. I am wondering what would happen. Surely it has happened to some star in any case.24.7.28.186 (talk) 04:41, 3 September 2011 (UTC)

Here's what I guess would happen:

1) No fusion at the surface.

2) It would submerge immediately, probably sending a massive fireball back out in the direction from which it came. I don't think the fireball would reach escape velocity, though, so would behave like a massive solar flare and follow magnetic lines of force back down to the surface.

3) Ripples would travel around the surface of the Sun and form a series of peaks and troughs on the opposite side, possibly launching flares.

4) The Sun's fusion might be temporarily interrupted. Not sure about this.

5) The magnetic field would be messed up, so we might see increased sunspot activity for some time after. StuRat (talk) 05:40, 3 September 2011 (UTC)

The Sun's fusion will not be interrupted because the amount of heat needed to bring up the object's temperature to that of the Sun is much less than what the fusion reaction is putting out. This is like throwing a snowball into a blast furnace -- the snowball just vaporizes, while the furnace just keeps on melting steel. Everything else is correct, though. 67.169.177.176 (talk) 06:04, 3 September 2011 (UTC)

I wasn't thinking of the direct cooling effect, but rather the physical disruption caused as the "slug" moves to the core, displacing some of that core into cooler, outer layers, where fusion would stop. StuRat (talk) 17:53, 3 September 2011 (UTC)

This won't happen cause the object would be completely vaporized long before it can reach the core. 67.169.177.176 (talk) 04:20, 4 September 2011 (UTC)

Are you sure about that ? And, even if it was vaporized, the gases should still continue with the same trajectory, right ? Or perhaps 100 times the mass would continue at 1% of the initial velocity, if it pushes along a good portion of the star, too. StuRat (talk) 06:55, 4 September 2011 (UTC)

Not exactly -- as soon as the object vaporizes, mixing and diffusion comes into play, which would slow it down and spread it out. So most of it wouldn't continue on the same trajectory for too long. 67.169.177.176 (talk) 04:47, 6 September 2011 (UTC)

A massive solar eruption will sterilise the Earth completely. Fortunately someone will build a shield to save us. (Although the aliens that caused it, then have a another try at wiping us out. Mitch Ames (talk) 05:48, 3 September 2011 (UTC)

I agree that there won't be a significant effect as far as the Sun is concerned, but the orbits of the planets can be significantly perturbed. The Earth could e.g. be kicked out of the Solar system, or crash into the Sun or another planet. Count Iblis (talk) 18:12, 3 September 2011 (UTC)

While approaching the sun, the Jupiter-sized planet would lose its shape and be splitted in pieces because of the huge tidal forces of the sun, that’s what we call Roche limit. This happened to the Comet Shoemaker–Levy 9--Franssoua (talk) 10:56, 5 September 2011 (UTC)

If it's moving fast enough the pieces will still be traveling in about the same direction and generate the same effect. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 14:52, 5 September 2011 (UTC)

Vicodin vs Vicoprofen

Why do so many doctors prescribe vicodin over vicoprofen? From everything I have read, the tylenol in vicodin doesn't really do anything beneficial, but the ibuprofen in vicoprofen would help reduce inflammation which is common in most people with pain. — Preceding unsigned comment added by 76.173.30.220 (talk) 04:32, 3 September 2011 (UTC)

I don't like the idea of combining meds like that. If you have a separate pain killer and anti-inflammatory, you can take whichever one(s) you need and avoid excess drug interactions. StuRat (talk) 05:30, 3 September 2011 (UTC)

Vicodin is a combination drug. It is hydrocodone combined with acetominophen in the same pill. Vicoprofen is a similar pill which contains both hydrocodone and ibuprofen. --Jayron32 05:34, 3 September 2011 (UTC)

Our vicodin#Pharmacodynamics article notes (without cite) that there is a synergistic effect between the two components. However, even considered separately, the two act in different ways and locations to reduce pain. DMacks (talk) 15:39, 3 September 2011 (UTC)

Acetominophen is an anti-inflamatory, too 208.54.38.193 (talk) 17:17, 7 September 2011 (UTC)

"Surface" of the Sun

I recall it being mentioned, in an undergrad physics course I took long ago, that what we call the "surface" of the Sun is actually somewhat of an optical illusion. The density increases gradually, but because of an artifact of the increasing refractive index, we see a sharp transition.

Is that true, and do we have an article on it? --Trovatore (talk) 06:28, 3 September 2011 (UTC)

Surface of the sun doesn't cover this, but the third paragraph of Sun#Characteristics starts with:

The Sun does not have a definite boundary as rocky planets do, and in its outer parts the density of its gases drops exponentially with increasing distance from its center. Nevertheless, it has a well-defined interior structure, described below.

The subsequent text appears to answer your question. Mitch Ames (talk) 07:05, 3 September 2011 (UTC)

Hmm, well, not quite, or at least it doesn't deal with it directly. It says the photosphere is the boundary where the gases get too cool or too thin to glow visibly. But the claim I recall is that light rays coming from different directions bend more or less because of the gradient of refractive index, producing an apparent discontinuity or near-discontinuity in brightness. I don't see any text in the article that either confirms or denies that. --Trovatore (talk) 07:56, 3 September 2011 (UTC)

Supercritical ocean

Is it technically correct to say, Venus is mostly covered by an ocean of supercritical carbon dioxide? If so, then would you notice the presence of such an ocean if you are suspended 100 m above the critical barosphere, what would it look like, and what is the average depth of such an ocean? Plasmic Physics (talk) 08:45, 3 September 2011 (UTC)

The transition between the subcritical and supercritical layers of the atmosphere is gradual, so there's no visible interface for you to see. Same as on Jupiter, only Venus's atmosphere doesn't turn into a liquid like Jupiter's does. FWIW 67.169.177.176 (talk) 09:04, 3 September 2011 (UTC)

I know that there is no visible interface like that of a normal body of water on Earth, but then neither do clouds. Clouds are white and fluffy, the humid air around it is not. Supercritical carbon dioxide is white and fluffy, gaseous carbon dioxide is not. I guess whether you notice the presence of the ocean or not at a 100 m, depends on the pressure gradient. Plasmic Physics (talk) 09:20, 3 September 2011 (UTC)

I think it is confusing to use the word ocean for anything other than a liquid. Looie496 (talk) 16:06, 3 September 2011 (UTC)

. Slightly supercritical carbon dioxide and slightly subcritical carbon dioxide ought to look very similar. That's part of the point that there isn't a phase transition at supercritical boundary. Water clouds aren't comparable because there is a true phase transition there between water vapor and water liquid. In addition, though the Venera images aren't the clearest things in the world, it is certainly possible to see on the surface of Venus so it is not like being in a fog bank. Dragons flight (talk) 17:59, 3 September 2011 (UTC)

At what point is it appropriate to call a supercritical barosphere an ocean? How many grains of sand make a pile? Plasmic Physics (talk) 05:55, 4 September 2011 (UTC)

I'd say it depends on the increase in density and/or viscosity. In other words, when the barosphere becomes dense enough to support very lightweight solid objects (balsa wood, paper, etc.) or viscous enough to cause significant drag even at low speeds, then it can be considered a liquid. FWIW 67.169.177.176 (talk) 04:11, 5 September 2011 (UTC)

What about a fish tank full of sulfur hexafluoride, there is no liquid involved, yet an aluminium foil boat can float in it. Or what about the oceans of liquid methane on Titan, liquid methane isn't that viscous, is it? Plasmic Physics (talk) 14:36, 5 September 2011 (UTC)

Liquid methane IS viscous enough to cause significant drag to slow-moving objects, as is water. Yes, on second thought, it would be better to judge by viscosity rather than density whether a supercritical fluid is more like a gas or more like a liquid. FWIW 67.169.177.176 (talk) 04:44, 6 September 2011 (UTC)

What would be the reference viscosity, this original question is a technical rather than a semantic question. Plasmic Physics (talk) 13:33, 6 September 2011 (UTC)

Y'know, it's pretty hard to agree on a definite viscosity that marks the borderline between "supercritical gas" and "supercritical liquid" -- there's a big gray area between the two. The best answer that I can give you is, "more viscous than any gas under normal conditions, but less viscous than any liquid under normal conditions". FWiW 67.169.177.176 (talk) 06:04, 7 September 2011 (UTC)

Is Quantum Theory REALLY so spooky and weird?

OK, this is where I get to display my ignorance on this subject, and if I do, hey come in and tell me.

I am puzzled over this. The 'weird' part lies almost entirely in this: that events in the quantum world are so arranged that they are affected by our observation of them.

Now, think of this thought experiment: I am a physicist and go home and dream about some particles I have locked up on glass slides. When I get to work the next day, I (and my colleagues) find that those particles, and ONLY those particles, have disappeared. Now THAT would be weird.

My question is basically this: To observe something is NOT the same as thinking or dreaming about it. In the experimental setup, one has to shine some kind of light on the particle in order to see what it is doing (or indirectly on some particle with which it is associated.) On this level of the very small, shining a light on something is like throwing a boulder at it. So it is no wonder that the particles which are 'observed' (have boulders thrown at them) are behaving differently to the ones that do not have this done.

To take the weirdness literally is to make a special case for consciousness as a phenomenon different in kind to all other types. I would have thought that fundamentalists would have grasped this and been converts to 'quantum weirdness' because it says that thinking and observing are very special events that change things in ways that other kinds of interactions do not. In other words, that there REALLY IS a distinction to be made between materialist and idealist phenomena, something that sceintists would not normally be happy to admit.

So, is there anything at all in my musings? Myles325a (talk) 10:09, 3 September 2011 (UTC)

For the most part, you are right that the "you affect things by observing them" thing is the same for everyday things as for sub-atomic things but is just bigger for sub-atomic things because photons are larger relative to them (please excuse the very imprecise language!). There are weirder things, though. For example, in the double-slit experiment it is possible to observe which slit a photon went through without actually stopping it going through. If you do that, the interference pattern suddenly disappears and you get the two bright lines that you would expect from classical mechanics. A lot of the weird stuff in quantum mechanics doesn't come from the effects of observation, though, it comes from the probabilistic nature of everything. An electron in an atom, for example, doesn't have a well defined position. It needs to be thought of as a probability distribution of possible positions. That's very weird when compared with our experience of things at human scales where everything is in a definite place. --Tango (talk) 10:26, 3 September 2011 (UTC)

If I understand you correctly (and there's a fair chance I don't), you're asking "is a shallow caricature of quantum theory often used by religious fundamentalists as an argument for Cartesian Dualism?" and the answer is no, that's not what fundamentalists do. That's what fruity new-age types do, all the time, although there was more of it around in the 90s.  Card Zero  (talk) 10:31, 3 September 2011 (UTC)

I've always taken QM to be a mathematically elegant method for describing the behavior of very small things. The problem is while most scientific disciplines can be reduced to a set of low information content math-free core concepts that can be explained to a general audience, this doesn't work very well for quantum. In all seriousness, I think the only way to get an adequate grasp of quantum mechanics is to take a graduate level quantum class and go through all the derivations yourself. Then it will start to make sense. Pop-culture quantum is little more than philosophy unfortunately. I(q) = User(q)·Talk(q) 14:10, 3 September 2011 (UTC)

I think Feynman's QED: The Strange Theory of Light and Matter works quite well. Sean.hoyland - talk 14:25, 3 September 2011 (UTC)

If I may butt in, IMO, the quantum mechanics we see on the Discovery channel looks very flashy to see, and to any normal person, it looks highly fascinating. But to a seasoned physicist, it is not that fascinating, and its even mundane sometimes. It all depends on who you are and how you see it. Lynch7 14:34, 3 September 2011 (UTC)

QED is great for what it does, but I don't think it sheds any light on the measurement problem. -- BenRG (talk) 02:45, 4 September 2011 (UTC)

The issue with QM is that at the quantum level a lot of things don't behave like macroscopic objects do. It's not that they don't have a logic to them — they do, and it has been inscribed into some very fancy equations for some time now. It's that when you try to reduce those equations to "macroscopic logic" — the sort of logic that makes sense at the level that humans interact with the world — then you end up with contradictions, paradoxes, things that don't seem to make sense. But that's just because you're applying the logic to the wrong realm. When the people who've spent a lot of time with QM say "oh, it's not that weird," it's just that they've internalized that division of logic and don't worry about it anymore. Einstein didn't want to do this, and thought that logic should be logic on all scales — this is why he thought it was "spooky" and was not a fan of it at all. But basically Einstein was wrong.

Still, there are some weird-ass, totally testable results. My favorite is Wheeler's delayed choice experiment. It's basically the double-slit experiment on a cosmic scale, which makes it even weirder, since your choices of measurement today apparently affect the path of a photon that was emitted billions of year ago. To a photon, though, this totally makes sense. --Mr.98 (talk) 14:40, 3 September 2011 (UTC)

It makes sense in the transactional interpretation, which expands the suggestions of Empedocles by saying that an advanced wave of light is emitted by the telescope and propagates backward in time toward its object. Once a person understands, like Cassandra, that there is only one past, one present, and one future, physics becomes considerably more intuitive. Wnt (talk) 16:44, 3 September 2011 (UTC)

Honestly, I don't think that makes it more intuitive, to have waves of light going backwards in time from the observer (rather than the emitter). You can say, "I choose not to question the logic of this," and much of the math requires one to do that, but that isn't to say it's actually intuitive — you've just stopped demanding for it to make intuitive sense. That is what I meant above when I mentioned the internalization of quantum logic. It might not be wrong to think about it that way, but it isn't intuitive, if you actually care about things making sense. --Mr.98 (talk) 17:08, 3 September 2011 (UTC)

I don't believe that the transactional interpretation exists as a logically coherent formulation of quantum mechanics. It only has one proponent of note—John Cramer—and he doesn't seem to know how to derive basic experimental results in quantum mechanics free of any interpretation. A few years ago he proposed a retrocausality experiment ("The UW Nonlocal Communication Experiment") that's just a quantum eraser without the coincidence counter. Everyone else knows how this apparatus will behave, but he seems not to. I don't think it's possible for someone with such a basic (for a professional physicist) misunderstanding of quantum mechanics to "interpret" it. -- BenRG (talk) 02:45, 4 September 2011 (UTC)

The biggest problem with the philosophical interpretation of quantum mechanics is that the uncertainty principle seems to be at odds with special-relativistic causality. This is the EPR paradox. It's not such a big deal if a formerly accepted principle like SR causality turns out to be wrong; the trouble is that it's not wrong. If you want to make a "realistic model" of quantum mechanics you have to break special relativity in some specific way, and then the question is why the physicists in your model universe can't detect the specific nature of the breakage. In almost every set of physical laws that are compatible with your assumptions, the breakage (that is, the true nature of things) is detectable. So why would the universe choose the one set of laws that's deceptive? Physicists have to assume the universe is not malicious, since otherwise physics is impossible.

Another philosophical problem that's less nasty but still interesting is interaction-free measurement. If you put a particle detector somewhere and it doesn't detect a particle, that tells you that no particle was there. That's a measurement and it has a detectable effect like any other measurement, even though the experimental apparatus and the system didn't interact and weren't even in the same place. The Elitzur–Vaidman bomb tester is one surprising example of this. Another is "radiation-free radiography": you can, in principle, take a chest X-ray without depositing any radiation in the patient's chest, by measuring the probability that the X-ray photons would have been absorbed had they passed through the patient, even though they didn't. The chance of actual absorption can be made arbitrarily small, though not exactly zero. It's odd that you can experimentally measure the effect of possibilities that weren't realized, but I think you can just accept that the world works that way; there's not as much of a practical problem with interpretation as there is with the EPR paradox.

Historically, another problem was the "collapse of the wave function" that apparently occurs when a measurement is made and is responsible for the measurement effect. The collapse looks like a Bayesian update, but whereas a Bayesian update is just a change of your subjective opinion of something's likelihood, the wavefunction collapse has measurable physical consequences. This is what convinced some prominent physicists that there was some sort of special connection between one's subjective thoughts and the outside world, early in the history of quantum mechanics. I think it's fair to say that this problem is now completely solved. The traditional wavefunction collapse combines two different things: quantum decoherence, which is a physical process having nothing to do with subjective opinions, and a true Bayesian update, which is subjective and has no effect on the outside world. But the knowledge that this problem is solved has not trickled down to the general public. There's still a lot of quantum woo-woo based on those early statements by prominent physicists. -- BenRG (talk) 02:45, 4 September 2011 (UTC)

I don't think the thing that's hardest to accept about EPR and related paradoxes is actually causality. Most people intuitively accept free will, and therefore limitations to causality.

As I've said before, I think the biggest sticking point is realism. In the two-slit experiment, which slit did the electron actually go through? --Trovatore (talk) 03:33, 4 September 2011 (UTC)

Neither. 'electrons' are concepts we've invented to explain the results of our experiments. As are 'slits'. Or 'experiments'. There is no reason to expect that the universe should be 'realistic', 'reasonable', or 'explicable'. Sometimes we think we understand it - but that is usually just the result of not looking closely enough at it. AndyTheGrump (talk) 03:56, 4 September 2011 (UTC)

AndyTheGrump is being a bit trite here, and while I don't agree with much of the nihilism of it, there is a nugget of truthiness to it which needs to be explored, and it is this: QM and all the rest becomes much more understandable when you meet it on its own terms. The only way that QM doesn't make sense is when you try to treat things like electrons (and other such particles) as though they were little balls. Once you can divorce that idea from your mind, you will find QM much less perplexing. The slit experiment doesn't make sense if the electron is a little ball. Or even if it is sometimes a little ball. Or is ever a little ball. An electron is never a little ball. It is always, only, an electron. Nothing more, and nothing else. We can devise experiments and models and whatnot whereby thinking of the electron as a little ball may work, a bit, but the electron doesn't become that merely because our models need it to be. Its just an electron. Period. Once you stop having to pigeonhole it into manmade categories like "particle" or "wave" or whatever, and just take it on its own terms, the paradoxes and weirdness melts away... --Jayron32 04:13, 4 September 2011 (UTC)

Well, no, it really doesn't. The paradoxes and weirdness are really there at a very fundamental level that you can't get around by thinking of the electron as "an electron, period". You can try to think of the electron as de-localized, but it doesn't help, because other things respond to it as though it were localized.

This can be put into formal terms as saying that quantum mechanics violates "local realism". It doesn't necessarily violate realism per se; there can be an underlying reality. But put it together with locality and you've got a problem. We have articles about just how bad a problem at Bell's theorem.

Niels Bohr said, "anyone who is not shocked by the quantum theory has not understood it". It was true then and it's true now. --Trovatore (talk) 05:36, 4 September 2011 (UTC)

Thing is, there are deep philosophical paradoxes with "classical realism", so it may well be that quantum mechanics looks to be weird only because we ignore the problems with classical realism. So, I think that Niels Bohr was wrong. Count Iblis (talk) 16:05, 4 September 2011 (UTC)

I'm not sure what you mean by classical realism (and that link won't help ;) ), but I mentioned Empedocles and Cassandra to point out that there was a time long ago when people had a different intuitive sense of how the world worked, which in some ways seems more consistent with quantum mechanics. So I don't think quantum mechanics offends against intuition in general, but only against the intuition of people in this place and time with this culture's preconceptions. Wnt (talk) 17:21, 4 September 2011 (UTC)

Well, I think Cassandra was wrong. I don't buy the "block universe"; what's the point? I am entitled to assume that there is a point, because if there isn't and I think so, then I'm wrong, but it doesn't matter. For it to matter whether I'm right or not, there has to be a point. --Trovatore (talk) 18:50, 4 September 2011 (UTC)

Perhaps the point is not held within the four visible dimensions in which we mundanely perceive the development of human life, but in some additional dimension(s) in which entirely different laws apply. Wnt (talk) 19:05, 4 September 2011 (UTC)

For it to matter whether I'm right or wrong, there has to be a point to what I, personally, do, and therefore I am entitled to (and indeed, should) assume that there is. --Trovatore (talk) 19:09, 4 September 2011 (UTC)

OP myles325a back live. Holy Moly, what a complete waste of my time! And yours. This is like 95% of all answers to questions to this desk - the giver of light is far more interested in expounding on their pet hobby horse, and usually does not even KNOW what the question was. Sit down and listen CAREFULLY and don't bother to spew up a load here. I'm NOT thankful, I'm angry and I'm not going to take it anymore. Think like Alan Turing and try to give a fundamental definition of what is necessary and sufficient to be an act "of observing". How is it different to every other kind of pbenomena, like, say, photosynthesis? Would it be fair to say that if I tried to grow moss on an a quantum experiment, it would detect that and say "No moss on this roller, I'm a goin to pack into my little shell." What about simply THINKING about a particle, or talking about it? Now you will say that simply talking about a quantum particle will not affect its behaviour coz we are not "engaging with it". AHHHA!! Then what precisely is the engagement of "observing"? And if observing something objectively "engages" with the subject, then does not that relationship quite obviously going to affect it, and would not we expect it too? Think DEEPLY comrades, I don't want geekboys who know the name of EVERY particle to tug on my sleeve here. This is philosophy on a fundamental scale, not the time to with your collection of the brilliant names and shallow thoughts. You all remind me of what Ned Flanders once said to Lisa in a unique moment of rage: "Oh Lisa, someone with an answer to every question: THAT NOBODY ASKED!!!

If you have written ANY of the arrant shit in the above so called "answers" then don't bother contributing here again. I don't need you, I don't want your petty thinkettes. I want some people with a FRONTAL LOBE that works, not someone who has the family neuron while they are on holidays. Kapish? Then get started. And read my question carefully. And answer likewise. Myles325a (talk) 06:54, 5 September 2011 (UTC)

Attitudes like that are not welcome at the refdesk. Adjust yours or go away. --Trovatore (talk) 06:59, 5 September 2011 (UTC)

"Observing" is a bad choice of word by physicists. What happens when we look at something? Light bounces off it and enters our eyes. It's not the light entering our eyes that matters, but what bounces off the the object. When something "bounces" off a quantum particles, that is what we called observation of that particle. Which usually collapses its wavelength and blah blah blah. Humans don't need to be involved at all. As far as I'm aware, humans can't change a single physical thing at all by just thinking. That's called "the Force". Pascal (talk) 07:25, 5 September 2011 (UTC)

Well, no. Interaction with something else does not in itself collapse the wavefunction (not wavelength). Apparently the modern thinking is that the wavefunction doesn't really collapse at all but just "appears to"; some of that is beyond my expertise. What is very clear, though, is that however you slice it, it's really really weird. That's different from saying it's weird in the specific way of thoughts influencing the physics, but nevertheless weird. --Trovatore (talk) 07:29, 5 September 2011 (UTC)

[1] may strain a frontal lobe, but it indicates that the photon in the two-slit experiment always passes through both slits, not one or the other; the issue is that the confirmation wave is sent from one location or another. The "act of measurement" is the act of emission of this retrotemporal signal from the detector. Wnt (talk) 23:22, 6 September 2011 (UTC)

An interpretation that requires backwards causality is every bit as weird as any of the others proposed. --Trovatore (talk) 00:29, 7 September 2011 (UTC)

Behavioural toxicity

Will someone explain what behavioural toxicity is.Specially I want to know views on behavioural toxicity of psychiatric and neurological medication.Will someone please provide pointers to the literature on this topic.Pachyobs (talk) 12:10, 3 September 2011 (UTC)Pachyobs (talk) 13:10, 3 September 2011 (UTC)

Behaviour induced by a substance which is not helpful. A side-effect which has a negative affect on behaviour. This abstract gives a good explanation. [2] This is a relatively small field of study (although it effects a great number of patients). Books about this subject tend for this reason to be expensive. You may be better going to Google Scholar and starting your own research there.--Aspro (talk) 13:24, 3 September 2011 (UTC)

Lunar eclipse?

Is File:Harvest moon.jpg a total lunar eclipse? The moon seems red. 123.24.67.209 (talk) 14:31, 3 September 2011 (UTC)

No, the image of the moon was taken when it was close to the horizon. It appears read because of Rayleigh scattering. Interestingly enough a lunar eclipse appears red for the same reason, but there is also a shadowing effect that appears during a lunar eclipse which is not present in this image. --Daniel 14:45, 3 September 2011 (UTC)

Malai-ula Banana

Does anybody know anything about a species of banana named the Malai-ula, written also Malaiula and Manaiula of the Maoli group, seen here? Like what is its scientific name?--KAVEBEAR (talk) 17:16, 3 September 2011 (UTC)

As far as I can tell there is no distinct scientific name -- all modern cultivated bananas are hybrids of the two species Musa acuminata and Musa balbisiana. Looie496 (talk) 23:50, 3 September 2011 (UTC)

Please be aware that cultivars are not species, and the old Linnaean names Musa sapientum and Musa paradisiaca applied for bananas and plantains respectively, as well as the dozens of other scientific names assigned to different cultivars and varieties of bananas over the years, are incorrect and should never be used.

Like Looie496 mentioned, almost all modern banana cultivars are hybrids and polyploids of two species. All cultivars of the Maoli-Popoulo group (better known as 'Pacific plantains') belong to the AAB Group. The 'A' in AAB represents genotypic characteristics of Musa acuminata, while 'B' represents Musa balbisiana.

The correct scientific name of malaiula bananas (as a member of the Maoli-Popoulo group) is thus:

Musa acuminata × balbisiana

× represents hybridization. If you wish to be more specific to that particular cultivar (if it is a recognized cultivar), the scientific name + cultivar name should be written as thus:

Musa acuminata × balbisiana cv. 'Malaiula'

If written complete with authors and subgroups, it would be:

Musa acuminata × balbisiana Colla (AAB Group) cv. 'Malaiula'

-- Obsidi♠n Soul 09:19, 4 September 2011 (UTC)

manned robot-like machines?

coming soon to a war near you

After waching "Avatar", a freind stated with apparent 'common knowledge' that the manned robot-like machines which walk a round on two legs in the movie, actually exist in the U.S. military. It seems to me that such a design would be inherantly problematic and would have little strategic value. Does anybody know if such things really exist?Phalcor (talk) 17:58, 3 September 2011 (UTC)

In Avatar, those were unmanned avatars, the people were elsewhere, operating them remotely. I believe the military did experiment with manned robo-suits, without much success. However, operating vehicles remotely seems like a much safer option, now that we have that technology. Note that the "robo-suit" technology, though, does have applications for disabled people, so research continues there. StuRat (talk) 18:43, 3 September 2011 (UTC)

The movie had manned robot walkers too, e.g. [3] Dragons flight (talk) 19:01, 3 September 2011 (UTC)

Indeed, and the short is answer is yes, the military does have powered exoskeleton, or "battlesuit" technology, but it is not yet developed enough to be practical on the battlefield, and is much smaller than the huge mechs seen in movies and anime. Beeblebrox (talk) 19:07, 3 September 2011 (UTC)

Another device in development is BigDog, which while not an exoskeleton is a walking military robot. Walkers like the ones in Avatar are not currently used by the military. --Daniel 23:12, 3 September 2011 (UTC)

Mecha is the term for a piloted walking machine. From a military point of view, they definitely are useful depending on their design and capabilities. The advantages are of course, superior mobility and agility compared to wheeled or tracked vehicles. The horse, after all these years, can still negotiate terrain that a wheeled or tracked vehicle simply can not. However the disadvantage is of course stability. Basically if the mech is too big like the ones from battletech, then their sheer size will work against them. They will be walking artillery targets, and can be knocked over far too easily. The ones from avatar are about the max size you would want them to be. As for, do they exist in the military? No they do not exist yet. More advances in robotics need to be made. Namely the development of artificial muscles and better actuators. It may be possible to use stemcells of other animals and grow muscles that are used in conjunction with a machine creating sort of a cyborg. The Gekko from Metal Gear Solid 4 have legs that were grown from the stemcells of ungulates. http://metalgear.wikia.com/wiki/Gekko ScienceApe (talk) 01:33, 8 September 2011 (UTC)

Escape velocity

The escape velocity of Earth is 11.2 km/s, but what if, for example, you built a giant staircase that went from Earth's surface to outer space? It would clearly be possible to take the first step, and each subsequent step would only be easier because of the weakened gravity. --76.211.90.74 (talk) 20:08, 3 September 2011 (UTC)

Yes, the escape velocity doesn't apply in that case, since it's not just your momentum moving you away from Earth, but an additional force on the staircase with each step. StuRat (talk) 20:13, 3 September 2011 (UTC)

You can leave earth at any speed. At the surface, you need those 11.2 km/s, but at the moment when you start going higher and higher, you need less and less speed. Your hypothetical staircase accomplishes just that: it takes you to the point where you just need a little speed to leave earth. 88.9.108.128 (talk) 21:39, 3 September 2011 (UTC)

If you put the staircase on the equator, then after the first 36,000 km, you would have to rotate 180° and start to climb upside down to go higher. It woud feel like climbing down with the Earth above your head. Count Iblis (talk) 21:47, 3 September 2011 (UTC)

What ??? StuRat (talk) 21:52, 3 September 2011 (UTC)

What ??? II 88.9.108.128 (talk) 22:01, 3 September 2011 (UTC)

Space elevator. TenOfAllTrades(talk) 22:11, 3 September 2011 (UTC)

In order to climb the stairs, you need to keep rotating with the Earth, ie. once every 24 hours. Once you reach the altitude of geostationary orbit, that rotation is the same as orbital velocity, so you would feel weightless (as anything in orbit does). Once you get higher than that, you will be moving faster than orbital velocity. That means centrifugal force (and yes, it does exist in this context) will be greater than gravity, so you will be pulled away from the Earth. That means you need to stand on the underside of the stairs. --Tango (talk) 22:25, 3 September 2011 (UTC)

Aaaahhh !!! 88.9.108.128 (talk) 22:28, 3 September 2011 (UTC)

Geostationary orbits are always in the plane of the Equator. Cuddlyable3 (talk) 23:07, 3 September 2011 (UTC)

Hmmm. Escape velocity is equal to sqrt (2 G M / r). G = 6.67 × 10^-11 m³ kg^-1 s^-2. M = 5.9736 × 10²⁴ kg.

• So Earth escape velocity for a given r is sqrt (7.969 x 10¹⁴ m³ s^-2 / r).

• Anything spinning geosynchronously will have a velocity 2 * pi * r / 86164 s (note the sidereal rotation period, your space elevator not caring when the sun rises).

• So assuming these r's are the same (only an approximation unless the elevator is at the equator) we can set them equal. That means 7.969 x 10¹⁴ m³ s^-2 / r = (2 * pi * r / 86164 s)². Pulling out the constants and seconds, 4.708 x 10²³ m³= r³, and r = about 77800 km. At this point, anything released from the top of a space elevator should fall entirely out of orbit ... unless I fouled up the math!

Searching for "space elevator" and "78000 km" finds me a few hits, mostly about it being twice the geostationary height, which seems oddly appropriate... I should keep digging, but I'll leave it at this for now. Wnt (talk) 00:02, 4 September 2011 (UTC)

7.969 x 10¹⁴ m³ s^-2 / r = (2 * pi * r / 86164 s)² gives r = 53000 km (this is 2^(1/3) times the r of the geostationary orbit), that is where you can let go of the ladder and fly to infinity.--Patrick (talk) 10:45, 4 September 2011 (UTC)

Phooey - apparently I can't be trusted with a calculator. Explains why I couldn't find my source! But armed with this figure I found [4] which gives an escape radius of 53,100 km. It also says transfer orbits to L1, lunar, and L2 are reachable from 50,630, 50,960, and 51,240 km respectively. Wnt (talk) 18:44, 4 September 2011 (UTC)

Dark matter and dark energy

Other than that they're both invisible, is there any connection between dark matter and dark energy? --76.211.90.74 (talk) 20:11, 3 September 2011 (UTC)

Yes of course. Since Herr Einstein proved that matter is another form of energy, then that is their connection, assuming that dark matter and dark energy actually exist.190.56.108.113 (talk) 20:44, 3 September 2011 (UTC)

So is dark energy just dark matter converted into energy (and vice versa)? --76.211.90.74 (talk) 20:57, 3 September 2011 (UTC)

O.K. I'll go with it. Since the existance of both those items is theoretical, then that question is a bit like asking if all the seven dwarves are related.190.56.108.113 (talk) 21:07, 3 September 2011 (UTC)

That would be an appropriate question. The answer would be to determine if the author ever specified their relationship, just as the answer here is to determine if those who developed the theories of dark matter and dark energy theorized any relationship between the two. StuRat (talk) 21:47, 3 September 2011 (UTC)

Quite right StuRat. I did get a little flippant. Guilty as charged. I should have read your links earlier.190.56.108.113 (talk) 22:12, 3 September 2011 (UTC)

(Edit Conflict) To give a serious (though rough and ready) answer: no, they are not directly connected.

Dark matter is matter in individual galaxies and in galaxy clusters that we can't see (at astronomical distances), but which we are pretty certain must be present.

The reason we think it's there is that the speeds stars orbit around a galaxy and the speeds galaxies in a cluster move depend on the total mass of the galaxy or the cluster respectively - the more mass there is, the faster they move. We commonly see stars in galaxies - particularly in their outer portions or 'halos' - and galaxies in clusters moving faster than can be accounted for by just the mass we can see (in the form of glowing stars and hot gas, or non-glowing gas and dust lit up by the light from the former). We deduce that there must be some non-glowing or unlit-up mass we can't see - the dark matter. Whether this matter is in the form of a sea of exotic subatomic particles that have mass but otherwise don't interact much with ordinary matter - Weakly Interacting Massive Particles or WIMPS - of large cold objects like, say, planets that exist in space far from any stars to light them up - Massive Compact Halo Objects or MACHOs - or something else, or a combination, we don't yet know.

Dark energy is something completely different. We know that the whole universe is expanding (after the Big bang) and we know that the gravitational attraction between all the mass in it should be gradually slowing down the rate of expansion. However, observations over the last couple of decades suggest that the rate of expansion is either not slowing down as much as we expect, or might even be in the process of speeding up (all this is taking place over billions of years, so it's not easy to pin down). Some previously unknown force with the opposite effect to gravity may, we think, be causing this speed up, and cosmologists have labelled the source of this force "dark energy". Again, we don't yet know what it actually is. Other explanations have been proposed, one being that over very long distances gravity doesn't follow exactly the laws that we've worked out from observing it at shorter scales. {The poster formerly known as 87.81.230.195} 90.197.66.30 (talk) 22:26, 3 September 2011 (UTC)

Yes, the adjective dark tends to be used when we don't really know what we are dealing with (also in dark flow). There is no implied or known connection between the phenomena, other than the general connection between all matter and energy in the universe. Dbfirs 08:08, 4 September 2011 (UTC)

Dark matter is probably intermediate mass black holes, because exotic particles like WIMPs would have fallen in to black holes if they ever existed. 208.54.38.238 (talk) 18:20, 7 September 2011 (UTC)

Hormone therapy and sexual desire

Does taking hormones - corresponding to our gender or to the opposite - affect our sexual preferences? Quest09 (talk) 21:33, 3 September 2011 (UTC)

If taken during brain development in early childhood (or prenatally), then yes. After that the brain is hard-wired and much more difficult to alter. StuRat (talk) 21:45, 3 September 2011 (UTC)

Probably prenatally, anyway; see prenatal hormones and sexual orientation. Any possible connection between postnatal hormones and sexual orientation in humans is iffier. Red Act (talk) 02:38, 4 September 2011 (UTC)

You may find the article Chemical castration of interest. --Tango (talk) 22:27, 3 September 2011 (UTC)

Apparently, chemical castration does not change what you like. It only reduces the amount of what you sexually desire. Quest09 (talk) 22:32, 3 September 2011 (UTC)

So if you currently crave 300 pound women, this will make you crave 150 pound women ? :-) StuRat (talk) 06:48, 4 September 2011 (UTC)

Update to the Nutrition Facts box in USA

How will this help? [5] Sure, it'll make stuff less confusing, but what's the point of de-emphasizing sodium content, which most Americans overindulge in, or taking away the daily recommended values, which takes away the need to remember how much sodium I would need each day? Most Americans, I daresay, won't be able to calculate this information in their head, and fewer will remember how much, say, sodium they need each day. Imagine Reason (talk) 23:01, 3 September 2011 (UTC)

I don't think it's clear how the new labels will treat sodium, but I for one would be in favor of de-emphasizing it to some degree -- the current recommendations are absurdly low and there is no scientific evidence that following them leads to improved health. Looie496 (talk) 23:34, 3 September 2011 (UTC)

(edit conflict) Do you have a factual question or are you just here to rant? You can read what is in the article as well as the rest of us; if you don't like the answers that article gives you, I'm not sure what help we can be. --Jayron32 23:34, 3 September 2011 (UTC)

Lol, just noticed this one above my sodium-related one. This does look rather bad, not to violate WP:AGF, but seems to be a bit of soapboxing. Sir William Matthew Flinders Petrie | Say Shalom! 23:59, 3 September 2011 (UTC)

Would the average consumer have any idea what sodium content in food means to them? Note that I'm not asking other editors if THEY know. I'm asking if the general public knows. HiLo48 (talk) 00:14, 4 September 2011 (UTC)

No, I'm not soapboxing, and I'm surprised that anyone could fail to AGF to such a question. I am asking for the rationale for de-emphasizing a problematic area in nutirition (Looie496, more experts would agree than disagree that the current recommendation for sodium is too HIGH and much of the problem in hypertension is exacerbated by high sodium intake) and making it practically impossible for the average consumer to ascertain how much sodium is in the newly packaged foods. Imagine Reason (talk) 00:25, 4 September 2011 (UTC)

What's AGF? HiLo48 (talk) 00:30, 4 September 2011 (UTC)

See WP:AGF. Dominus Vobisdu (talk) 00:36, 4 September 2011 (UTC)

See this Scientific American piece for an overview of the current state of genuine scientific data concerning salt effects. Looie496 (talk) 03:12, 4 September 2011 (UTC)

This seems to be directly contradicted by DASH_diet#Conclusions. Imagine Reason (talk) 15:28, 6 September 2011 (UTC)

I agree that even a bad RDA% is better than none. Many people have no clue how much of each nutrient they need. They already dropped the RDA% for protein, which I think was previously set so 55 g = 100%. I'd have to carry a cheat sheet around with me, to tell me how much of each nutrient is recommended. Also, how I determine if a food is good or bad is if the percentages of the good things, like fiber, are higher than the percentages for bad things, like saturated fat and cholesterol.

The one proposed change which I very much would like to see is the red-yellow-green colors to show which nutrients are in healthy proportions and which are not. Also, I suspect that the reason they want to emphasize calories over fat, carb, and protein content is that many "diet" brands take out one of those, like fat, and then substitute in another, like carbs in the form of sugar. The resulting "diet" food can have more calories than the original.

One change they didn't list, which I would like to see, is trans fats being listed to the tenth of gram, instead of gram. Currently anything with less than half a gram per serving can be listed as zero, even though half a gram per serving may be harmful. StuRat (talk) 06:43, 4 September 2011 (UTC)

This is more a Humanities refdesk question in general, but one scientific claim in that article seemed really bizarre to me - the claim that people are eating highly processed "adult baby food" compared to 20 years ago. I mean, pizza is still pizza, ice cream is still ice cream, mashed potatoes are still mashed potatoes. I can't think of what food they have in mind that has changed. (It might be a valid point if it were 100 or 500 years though) Wnt (talk) 19:11, 4 September 2011 (UTC)

I think the point is that people are buying more and more of the processed foods and less raw produce, meat, etc. For example, fewer people are buying plain oats and more are buying the little packets of "instant oatmeal" with sugar and flavors and chemicals added. StuRat (talk) 05:17, 5 September 2011 (UTC)

Actually, by law trans fat content < 0.5g per serving must be listed as 0g. This is absurd and no doubt drafted by the food industry. Imagine Reason (talk) 15:19, 6 September 2011 (UTC)

How much sodium is too much in one day?

So I'm 21, 5' 7.4" (168.5 cm), about 160 lbs (72.72 kg), mostly muscle, though with some body fat. I purchased some yummylicious Holy Cow Kasher beef jerky, which I really like but has almost 1g of sodium per bag and there are three more left at the moment. I think I have eaten/inhaled about three bags today or so (almost 3 g of sodium. How much sodium would be sickening (poison me) and how much would be lethal for a fella like myself (not that I would get to that point)? Sir William Matthew Flinders Petrie | Say Shalom! 23:56, 3 September 2011 (UTC)

This is the kind of medical advice we really can't give. The health consequences vary depending on the person. I'll point you at Salt#Health effects and say the site disclaimer DOES apply. Wnt (talk) 00:07, 4 September 2011 (UTC)

Didn't realise nutrition was covered. Chillax bro, and thanks for the link. :p To answer my own question, it looks as 72g would do the trick, or would 144g of sodium, given that salt is half chlorine? Sir William Matthew Flinders Petrie | Say Shalom! 00:11, 4 September 2011 (UTC)

Salt is actually 39.33% sodium by weight.Anonymous.translator (talk) 00:26, 4 September 2011 (UTC)

Ah right, silly me, as you can see, I suck at chemistry (forgot all about them having different atomic weights). :p So how much sodium would that be? Surely more than I could willingly consume. Sir William Matthew Flinders Petrie | Say Shalom! 00:30, 4 September 2011 (UTC)

Well, that link said 1 g of salt per kg of body weight would kill you. That would be 0.3933 g of sodium per kg of body weight. Of course, it's silly to carry it to that many decimal places, since the amount that kills will vary somewhat from person to person. So, let's say 0.4 × your body weight in kg. Another way of putting that is that it's your body weight divided by 2500. StuRat (talk) 06:24, 4 September 2011 (UTC)

Most often I'm the lone voice arguing a question isn't asking for medical advice, but this really does cross the line. What you've given us is a weight, not a medical history, and we're interested in medicine, but not doctors. We don't know if you have arrhythmia, enlarged heart, high blood pressure, how much your blood pressure varies during the day, whether you have an aneurism. We don't know how much water, calcium, magnesium, and other things you take in that might help the kidneys eliminate salt. We don't know if you're in a hot climate or cold, dry or wet, nor the color of your urine. A rough average figure of a gram of salt, 0.4 grams of sodium per kg simply is absolutely no guarantee for individual human beings, and there is likely also some lower value where permanent damage is done that doesn't lead immediately to death, and I don't know where that is. Also let's not forget that beef jerky may contain other chemicals that might have some effect. Now I'm all for describing general information about salt and beef jerky and what people normally eat safely, if we can find that data, but when we start talking about how much you should or could consume, there we've gone too far. Wnt (talk) 17:16, 4 September 2011 (UTC)

I see what you're getting at, but I could have also asked for the same information in a very general manner without saying it was me or someone else and just talking very generally, now couldn't I? ;) This question was mostly asked for fun mind you (I find the idea of excessive jerky consumption to be amusing). If I had a serious health-related question about food consumption such as one cholesterol-related (an actual concern of mine in the past), I would ask my doctor. Needless to say though, it is highly unlikely I could actually consume enough jerky (or anything else with enough sodium) to cause me any damage as a result of excessive salt intake. Sir William Matthew Flinders Petrie | ^{Say Shalom!} 19:00, 4 September 2011 (UTC)

As long as you know we're not giving you advice about your particular situation, I'm OK with that - I just wanted to clarify that, since you never really know what might happen over the internet. (There's probably a campus jerky-eating contest somewhere...) Wnt (talk) 19:17, 4 September 2011 (UTC)

Come on wiki, I thought you were better than this... I'm surprised that no one's mentioned this yet, but the 'sodium' on a label is not a measure of how many grams of Na are in the food - it's just an abbreviation of sodium chloride. Now, table salt is not good for you in the long run, but the body is remarkably capable of normalizing short-term spikes. To illustrate this, let me propose a thought experiment (don't do this): imagine you go into your kitchen and find a salt shaker or container of salt (don't do this) and opened it up so that you were face with the salt, and not just the dispenser tip. Then imagine pouring it in your mouth and just eating it (don't do this) until you vomitted so violently that you physically could not consume any more (DON'T do this). If you are an otherwise healthy person, even this SHOULD not kill you, though you'll be sick for several hours at least. While it's wise to limit salt consumption, you cannot die by eating too many salty foods at once (unless you have any one of a number of salt-sensitivity disorders, in which case all bets are off). 24.92.85.35 (talk) 21:33, 4 September 2011 (UTC)

Wrong, Na means sodium, which often comes from other sources beyond NaCl. StuRat (talk) 03:48, 5 September 2011 (UTC)

Do you have a ref for the claim that grams of Na on the label is normalized to grams of NaCl? That's a very significant difference, if true. Note that not all sodium in food is in fact from sodium chloride. --Trovatore (talk) 22:21, 4 September 2011 (UTC)

I feel compelled to mention that while salt is almost harmless for adults, small babies occasionally die of salt poisoning and there is at least one documented death of a 4-year-old. [6] Hans Adler 22:39, 4 September 2011 (UTC)

"Almost harmless" in terms of acute toxicity, maybe. The chronic toxicity of salt is an enormous problem in the West. --Trovatore (talk) 22:59, 4 September 2011 (UTC)

I've got a container of my favorite flavor of salt right at hand (in the U.S.), which says a 1.4 gram serving contains 290 mg of sodium and 350 mg of potassium. As for your vomiting experiment, I wouldn't be that confident. Saline emesis is regarded as an outdated, dangerous technique even in cases of poisoning, especially where children are concerned.^[7][8] I can easily think of one circumstance under which I think such a salt shaker experiment would be deadly even to a normal healthy adult: if combined with marijuana use, which prevents vomiting. Wnt (talk) 22:11, 4 September 2011 (UTC)

Bender: There was nothing wrong with that food. The salt level was ten percent less than a lethal dose.

Zoidberg: Uh oh. I shouldn't have had seconds.