At zero degrees Kelvin, when KE=0, there should be little, if none at all, motion among any particles in the affected, enclosed area.

According to Heisenberg, one cannot measure a particle's motion without altering its position, and vice versa. Thus, small elementary particles cannot be seen and the apparatus used in the experiment is part of the experiment since it can alter the particle's position or momentum. Additionally, it has been "proven" that travelling particles (that are about to collide or pass) "know" what the other one is doing.

Does Bose-Einstein condensation have anything to say about this?

Now, my theory: at zero kelvin, there is no momentum. Therefore, a particle has no momentum during the moment the "event" is captured at zero kelvin - time must also stop for the particles - and therefore position can be accurately measured. A few ultra-milliseconds later, a second picture is taken (the particles roam around a weeny bit after the first measurement is taken and the degrees are raised a hundredth of a degree). Now, we have two events, close together, in which the particles were "frozen" in time and in their respective positions. In the second observation. the particles have a second position or have collided, so particles' momentums between the two observation can be deduced. There you have it (a bit to long).

One problem: To observe this experiment, we need an apparatus to measure. Modern apparati, as far as I know, shoot photons and stuff which rebound back, altering the particle's position (correct me if I'm mistaken).
Because of the one flaw in this theory, the experiment cannot actually be observed using any modern apparatus (unless I'm that far behind the rest of you)...unless someone knows a way around this obstacle.

The first problem with this idea is that it is impossible for any body to attain 0 deg Kelvin. Absolute zero temperature is something like the velocity of light, you can approach it ever more closely but you can never actually reach it.

The second problem is that temperature has nothing to do with time, so time would not stop at 0 Kelvin even if you could reach it (time passes just as quickly at 300 K, 273 K and 5 K though molecular activity will be much less at 5 K than 300 K. Temperature is after all just a measure of molecular motion, this is unrelated to time.)

The third problem is that the "uncertainty" in the principle is not due to some deficiency in experiments, it is a fundamental property of the quantum world and the equations used to calculate how matter behaves at that level. So no experiment can eliminate the uncertainty no matter how it is conducted. To quote John Gribbin's excellent "In Search of Schrodinger's Cat" (which I recommend for a good laypersons introduction to quantum theory):

"It is a cardinal rule of quantum mechanics that _in_principle_ it is impossible to measure precisely certain pairs of properties, including position/momentum, simultaneously."

Matter at the quantum level shows "wave particle duality" and depending on what properties you are measuring will appear as either waves or particles, but never both at once. Position is a particle property and momentum is a wave property, the more closely you measure the particle properties the less precisely you can determine the corresponding wave properties, like momentum, and vice versa.

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David S.

"Why are the pretty ones always insane?"
-- Chief Clancy Wiggum, The Simpsons.

If what you are saying is true, then why bother with QM at all if all that you receive is an estimation? In order for a theory to be valid, it has to not just have precision, but also accuracy. Don't you agree?
Does particle-wave duality apply only to photons, by the way?

"According to Heisenberg, one cannot measure a particle's motion without altering its position, and vice versa"

when i think about this scenario it seems to me it might be a result of not being able to test in a fine enough manner.

to me, it's like they are trying to use a brick to detect the properties of an egg....the brick will always smash the egg if you throw it at it.

dr zuo a few years ago showed the structure of cuprous oxide...he had to use xrays and electrons to do it...and was able to make a nice picture that showed the structures in a fairly undisturbed form.

when we are able to use a very fine detection method i think we will see the properties of these micro structures/bodies without disrupting them.

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dshan said....
"The second problem is that temperature has nothing to do with time, so time would not stop at 0 Kelvin even if you could reach it (time passes just as quickly at 300 K, 273 K and 5 K though molecular activity will be much less at 5 K than 300 K. Temperature is after all just a measure of molecular motion, this is unrelated to time.)"

there's an argument over at the bad astronomy site that included the description of time...supposedly time really is relative to motion or activity.


but i don't agree.

Ah, but it's a very accurate estimation! The much-talked about "uncertainties" are in almost all cases so unimaginably tiny as to have no practical effect on the results. And QM lets you calculate them in advance and predict them as perfectly as it's possible to measure them. QM (actually Quantum Electrodynamics or QED) is the most accurately tested physical theory in history (much more accurately tested and measured than general relativity for example) and has come up trumps every time. The PC you are using now depends on QM to operate, way deep down in it's chips, as do particle accelerators, X-ray machines, and smoke alarms to name just a few.

Wave-particle duality applies to EVERYTHING--matter and energy. All photons, electrons, neutrons and protons are governed by the laws of QM. Now we are finding that even quite large clumps of atoms can be made to act like waves and display other QM behaviour when they are handled and isolated properly (and cooled sufficiently) in Bose-Einstein condensates, etc. One of the most fascinating questions being pursued in experimental physics today is at what point do systems of sub-atomic particles and atoms start behaving as "classical" physical systems (e.g. footballs and satellites) instead of these weird wave-particle combinations that rule the world of the very small.

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David S.

"Why are the pretty ones always insane?"
-- Chief Clancy Wiggum, The Simpsons.

[QUOTE=dshan,Apr 24 2004, 09:23 AM] Absolute zero temperature is something like the velocity of light, you can approach it ever more closely but you can never actually reach it.
That of course refers to the speed of light in a vacuum, not through a medium. See my post in the Q&A forum about how light can travel much faster than c through a medium.

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Quid hoc ad aeternitatum
The conversion of complex and abstract ideas into simple and concrete ones is the essential function of teacher of a body of knowledge.

:huh: Light can travel at faster than c in a medium? It has already been proved that light slows down in a medium, and is therefore refracted ie . water. There is no way that by adding a medium light would be able to travel FTL. Light speed is an internal result and is only altered by changes to the photons internal 'mechanism' ie. negative mass. No external feature can speed light up

K_

I'm guessing the source of confusion is that things can travel faster than light in a medium, producing Cherenkov Radiation. You are right that light goes fastest in a vacuum, and slows down in glass or water.

There was an experiment a year or two ago which seemed to show some information travelling faster than light, but I think it was debunked.

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Forming opinions as we speak

I once read a great description to explain Heisenburg Uncertainty. If you want to measure the motion of a baseball you can take lots of highspeed pictures using a powerful strob-light to capture the balls position at each frame and run it together to map its motion. The photons of light, even from a powerful strob-light flashing many times per second will have no effect on the motion of the baseball. If, however, the object you want to measure is a single atom, the photons you use to measure its motion will have an effect on the motion of that atom. You could use a high intensity strob-light and hit the atom with a large number of high energy photons at once to get a very accurate position, but those photons will then drastically change the velocity and direction the atom is traveling making it impossible to plot its motion. If, on the other hand your goal is to accurately plot its motion you can try to use as few photons as possible at very low energies so that the effect on its motion is tiny, but you lose the ability to accurately measure the photon's position at any given point during its motioin.

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...and we'll be saying a big hello to all intelligent life forms everywhere; and to everyone else out there, the secret is to bang the rocks together, guys...