Physics at Absolute Zero

Here’s a question that’s been floating around in my little office for a bit: At absolute zero -
(1) All atoms cease both brownian motions and their “shaking”.
(2) All energy has been removed from the system (i.e. kinetic energy, etc.)
(3) Is the lowest (energy-wise) attainable state for matter in theory - cannot be achieved realistically.
(4) No properties can be measured accuratly at this state, since all measurement methods impart some energy to the system, and as a consequence, rise the temperature slightly.
(5) Speed of electron orbit slows, or stops.

My question: are any of these premises true? Ideas?

Heisenberg’s Uncertainty Principle not only ensures that we can never in the real world reach absolute zero (just very, very close to it) but also that there is always some residual motion even in a theoretical system. So what you’ve posted is what would happen in a classical universe but not in a quantum mechanical one.

Oh, now this inspires me with another Crackpot Physics Question.

The Principle of Entropy states that disorder in a closed system always increases… if I understand it correctly, this essentially means that while energy is never destroyed, when it used used some portion of it is lost to waste-heat, and isn’t recoverable.

What happens when the universe is done? All stars burned out, all life gone, etc.

Will the entire expanse of the universe be a matterless void, heated by the entropic waste to a balmy 3 degrees Kelvin? How does entropy increase, then?

Sorry for the tangent, One Brick.

The most fun kind

That is a misstatement of the second law of thermodynamics. Unfortunately there is no succinct way to state unambiguously what it does say. People make a whole freaking career out of it.

A better way might be to say that in a closed system there is no process where the only result it to make the system more orderly. This goes in line with not being able to easily recover waste heat. Your fridge makes the inside colder only by adding the energy from the inside plus ovehead from the power it’s drawing from the wall socket to the room.

As for the universe it’s not certain it will be done, if it’s open and doesn’t collapse on itself maybe so.

Lets see here, I think I might have a line of reasoning that can answer that. Just prior to the big bang, a singularity existed which contained all the energy for our system (read: all the energy our universe will have over the course of it’s existence). The big bang radiated all this outward in all directions at the speed of light (since nothing can travel faster than it, 2x the speed of light * age of universe should give us the exact maximum diameter of our universe). Some was converted into matter, and the rest remains energy (hence the temperature above abs. zero) in some form of radiation or another. Anyway, as the universe expands, the matter:energy ratio changes (E=mc2 and all, and as thermodynamics tell us), but is never less than or more than it was at any other time. The only thing that changes is the amount of this matter:energy per volume universe (since it is always expanding). This value should continue to drop, but never reach zero. I’m not saying all this is true, but it’s what I think is true. Dunno, we’ll see right?

Now to try and answer that question: Remember that entropy will always be equal to, or greater than zero. Things can remain just as chaotic, become more chaotic but never become (spontaneously) more ordered. But as another side note, this was proven not always true at the micro-system scale. Look up “Law of Entropy Broken” for some studies on it. Kinda interesting if you’re into that stuff.

Sorry for the disgustingly long reply!

Nothing made of matter with mass can travel faster than the speed of light within spacetime.

There are no restrictions on spacetime itself. It expanded much faster than the speed of light during the period of inflation.

There are now uncertainties whether the universe is open, closed, or exactly balanced between. You can’t answer the question of its fate without making a choice among these as a premise.

That’s true, but can the universe have dimensions but no mass? If force can’t move faster than the speed of light, can anything? Or is it that limits occur within a system, and the boundries of space/time aren’t within the system, and hence not restricted by it’s own rules. Interesting to think about.

To answer the OP, when you reduce the temperature to near absolute zero you get a Bose-Einstein condensate, basically a lump of matter where the atoms are packed so closely together you can’t tell them apart.

Mostly no.

  1. At absolute zero at standard pressure, helium remains wiggly enough to be a liquid.
  2. There’s energy in the very existence of the matter, and quite a lot of it.
  3. Depends on what you mean by low energy state, but yes, it cannot be achieved realistically.
  4. Sort of, yeah. See answer to 3/
  5. Misunderstanding of electrons. They don’t orbit like planets. They’re in the orbitals because if they weren’t in the orbitals but rather at the nuclei, you’d know where they were and that they weren’t moving, which you can’t do.

However, what you do get is an Einstein-Bose condensate, in which all the atoms become entangled in a quantum sense and behave in some ways like a single atom. Another way of looking at it is that an Einstein-Bose condensate is to matter what a laser is to light.

Yeah, I had figured that as a group, they would adopt the properties of a single atom, but what are the physical effects of a single atom cooled to this degree?

In thermodynamics, entropy is nondecreasing, not increasing. It can stay constant for as long as it wants. The “real” explanation goes to statistical mechanics, which reduces to thermodynamics like Einsteinian gravity goes to Newtonian in classical settings.

If the particles are bosons. A laser beam is effectively a BEC for photons, and it’s neither very cold nor packed closely together. That’s just how we’ve been able to manage it for anything other than photons, such as helium nuclei.

I think fermionic atoms, if they get cold enough, form “Cooper-pair” like couplets which act like bosons, analagous to electrons in a superconductor. These then can become a BEC, thus explaining the superfluidity of helium-3, the discovery of which won somebody the Nobel Prize.

Yes, bound pairs of fermions (say, two nucleons in a p-n state as in my example of helium) are bosonic states. But the particles “condensing” are the bound states.

Incidentally, when you can understand how two pairs of electrons can be in the same state without violating Pauli exclusion on the individual electrons, you’re close to grokking quantum logic.

  1. At absolute zero molecules still oscillate with ZPE.

  2. There’s still energy in some form or other.

  3. Absolute zero can never be attained due to thermodynamics (not Heisenburg’s uncertainity prinicple).

  4. Properties can be measured with arbitary accuracy, but Hesienburg’s uncertainty principle still applies.

  5. Electrons are in the lowest energy state.

True. I suppose someone should mention that temperature and energy are different things. In fact, friends of mine have made systems in which temperature decreases as energy increases.

I think this is a bit disingenuous. Thermodynamics is (as I see it) the older theory supplanted by statistical mechanics. I can see the sketch of a proof hinging on Uncertainty of the Third Law just as much as I can see a sketch of entropy’s nondecrease from SM.

I’m not sure what this has to do with anything.

I see statisical mechanics as a more precise expression of thermodynamics. Of course due to the statiscal nature of thermodynamics strictly speaking ‘never’ is a too strong a phrase to use, but practically speaking absolute zero is unobtainable.

Electron’s still have energy that can be thought of as kinetic energy in their lowest bound energy state.

Ah, I see. You were responding to the OP, not to my post.

I’ve always seen thermodynamics as what happened when chemists study something before the physicists get there… :smiley: Ok, I’ll stop now.

Well, that’s sort of the case in general (not the chemists bit, tho’). Newtonian gravitation was the theory until Einstein came along and gave a better idea. Thermodynamics was good until someone thought up SM, which generalized it.