Raymond Burr?
MJ said it best.
There’s no driving force. It’s all sources and sinks. To move energy from the part you want to reach absolute zero, there must be a sink of lower energy to absorb it. There is no sink lower than absolute zero.
Because heat is energy, and as molecules get more energy, they vibrate more. If you take a certain amount of any gas (oxygen, nitrogen, whatever), it’ll take up a certain volume at room temperature. Increase the temperature, and it takes up more spaces, because the atoms are vibrating around more frantically. If you lower the temperature, there’s less energy, so the atoms vibrate less, and it takes up less space. Lower the temperature even more and it’ll take up even less space.
But obviously, you can’t use less and less space forever – at some point, you get to effectively zero sized space where all those oxygen atoms take up no room at all. (Well, less than the planck limit, at least). You can’t take up less space than zero space.
We define absolute zero as the temperature at which a gas would take zero space. That’s why you can never get to absolute zero, you can only get close.
Absolute Zero can be neither created nor destroyed, right? I remember that from Physics class.
Or am I thinking about some other universal property, like Mother Love? Sexual Tension? Clear Ether?
The Heisenberg uncertainty principle.
If something was at absolute zero could it be re-warmed?
Well if you want to invoke The Quantum, it’s possible to have a situation in which a system has an energy deficit which would technically count as a negative value for the total thermal energy, although I don’t believe that you can actually achieve a genuine 0K this way.
It depends a little on what you mean. When most people think of “absolutely zero” they think of an unbounded system, such as a particle or particles in an infinite universe. In this situation, it is certainly possible for a system to exist at T=0, but getting it there from any finite temperature is another story. Roughly speaking, the work you have to do to lower the temperature grows without limit as you come closer and closer to T=0. In that, it’s somewhat like the approaching the speed of light – an asymptote which you can approach as close as you like (assuming you have the work available).
From the QM point of view, you need to create a wavefunction that has equal amplitude everywhere in the universe, i.e. dx -> infinity as dv -> 0 in such a way that the product continues to satisfy the uncertainty principle. You can imagine that if you start with a system that is at least somewhat localized, it will be a real problem ensuring it has equal amplitude everywhere in an infinite universe. You can get as close as you like, with the expenditure of work, of course – which corresponds to having your wavefunction uniform over a larger and larger volume, say, starting out with a beaker in a lab, then across the whole Solar System, then across the Local Group of galaxies, and so on.
If you are willing to regard confining potentials as strictly external – in other words, do not count the particles that generate them as part of your system – then it’s actually not especially hard to achieve T=0 for finite confined systems. For example, the electrons in an atom in its ground state form a tiny thermodynamic system which can readily be put into its T=0 ground state. The reason is that in a confined system it takes a finite amount (quantum!) of energy to raise the system to an excited state. If the fluctuations in energy available from the environment are small enough – smaller than the first excitation gap – then the system is stuck in the ground state, at T=0.
There are even some large collective systems that sometimes exhibit this property – those that superconduct, for example. Here an excitation gap opens up, for various not always well understood reasons, and if the fluctuations from the environment are small enough (i.e. the temperature is low, but not zero) then the system is “stuck” in the ground state, and exhibits the peculiar frictionless dissipationless dS = 0 properties of processes at T=0.
The previous passage from Absolute Zero is perhaps more compelling:
At a temperature of 170-billionth of a degree above absolute zero, Weiman and Cornell created a pure Bose-Einstein condensate in a gas cloud of just 3,000 atoms of rubidium, the first in the universe, as far as we know.
So these guys at MIT created what was probably the coldest temperature that ever existed in the universe. Won the Nobel Prize.
Cause entropy will take it all, though it may seem a shame. That, in a nutshell, is what entropy’s about - you’re now down with the discount.
Don’t get this. The HUP says not that particles don’t have a definite location – statistical location counts or not? – and momentum, but we just can’t measure both of them at once.
So, I’m not talking about sticking a thermometer in there. Can CalMacham’s objection be challenged by some sort of math and a nudge from a zillionth above 0K over the goalpost to 0 w/o needing to check? Ie, extrapolated?
Or are we talking about a frozen Schroedinger cat?
You’re not getting any allowance. You can’t get your way. And you can never leave the house. 
My post immediately above:
Carl Pham, did you just address this and I didn’t get it?
If so, could you dumb down your post for me?
Yes, but be sure to remove the protective foil wrapper before placing in microwave oven.
I believe it has to do with the quantum effect of ground states.
I think that, in the Copenhagen interpretation, the particles actually don’t have a definite location. I think there is still active debate on this though. Since we all agree we can’t know the two quantities, debate may be the only thing we ever get.
No. Popularizations to the contrary notwithstanding, the uncertainty principle doesn’ let things simultaneously have a definite position and momentum, regardless of whether anyone is measuring it or not. If you really did achieve zero temperature and had particles with absolutely no motion, then you would have absolutely no idea of their location. This isn’t highfalutin incomprehensible science, it’s a direct consequence of the wave nature of matter. And everything we know about things is consistent with that model. If you have a prblem, take it up with deBroglie.
so if you know that your matter is in the building, that sets an absolute upper limit on your knowledge of their momentum, which in turn sets a limit on their temperature. As long as the uncertaint principle holds, you’re not going to get to absolute zero.
I’m assuming by Nova you mean the WGBH programme?
Actually it was an Horizon programme and co-production with the BBC, but anyway.
Seriously though, if you look at one of the bases of Quantum Physics how can you ascertain the tempertature without changing it?
Secondly think of what you require, no radiation, No radiation absolute.
Practicly and I suspect theoreticly impossible.
Peter
So that Bose-Einstein condensate people have been talking about, very, very close to 0ºK, we only have a vague idea as to where it was?:dubious: