A question about Absolute Zero

[Rage Crank]

This is highly theoertical and I came up with it taking a standerized test. So without further adoo,

What would happen if you to a cyrogenic chamber froze something to ablsolute zero and put it on a spacecraft moving at exactly the same velocity as the universe is. Thus canceling out kinetic energy as well.
I am curious.

 

[HallsofIvy]

First, for quantum reasons, you can't freeze something "to absolute zero". The uncertainty relation means that with something inside, say, the laboratory room, there is some uncertaintly in the velocity of the atoms- and that velocity has to be 0, with respect to the laboratory, to be at absolute zero. You can, of course, freeze an object to very close to absolute zero.

Second, and more important, there is NO "same velocity as the universe is". Velocity is always relative to some other object.

Third, the temperature of an object is independent of the kinetic energy of an object (relative to some external frame of reference)- it depends on the kinetic energy of its constituent atoms relative to its own center of mass. If you change the velocity of the entire object, you change the velocity of the center of mass as well and so do not change the kinetic energy of the velocities of the constitutent atoms relative to the center of mass. Changing the speed of an object does NOT change it temperature.

 

[Bill_K]

First, for quantum reasons, you can't freeze something "to absolute zero". The uncertainty relation means that with something inside, say, the laboratory room, there is some uncertaintly in the velocity of the atoms- and that velocity has to be 0, with respect to the laboratory, to be at absolute zero. You can, of course, freeze an object to very close to absolute zero.

HallsOfIvy, I'm afraid I have to disagree with your reasoning on this point. The unattainability of absolute zero is a result of classical physics, not the uncertainty principle. Furthermore, the temperature of a system relates to its disorder, not the motion of its atoms. If you had a system made up of 10²³ atoms all in their ground state, its temperature would be zero, despite the zero-point motion of the atoms.

 

[Drakkith]

HallsOfIvy, I'm afraid I have to disagree with your reasoning on this point. The unattainability of absolute zero is a result of classical physics, not the uncertainty principle. Furthermore, the temperature of a system relates to its disorder, not the motion of its atoms. If you had a system made up of 10²³ atoms all in their ground state, its temperature would be zero, despite the zero-point motion of the atoms.

Everything I've ever read about temperature and heat agrees with Ivy and contradicts what your post says. Plus, if there were any motion at all would the atoms be in their ground state?

 

[Bill_K]

Everything I've ever read about temperature and heat agrees with Ivy and contradicts what your post says. Plus, if there were any motion at all would the atoms be in their ground state?

That's surprising, because what I've said is standard coverage in books on statistical mechanics, usually in the very first chapter. The unattainability of absolute zero is a consequence of the Third Law of Thermodynamics, whose original formulation (1905) by Nernst states, "The entropy of a system at absolute zero is a universal constant, which may be taken to be zero." An immediate consequence is that the specific heat must vanish at absolute zero, and this implies unattainability. Nothing to do with quantum mechanics anywhere in this, expressed or implied, the only relevant concepts being Carnot engines and heat reservoirs. And does not say the energy itself must vanish.

As far as temperature goes, its definition is in terms of entropy, not cessation of motion: 1/T = ∂S(E,V)/∂E. It is the parameter governing the equilibrium of systems, whose equality maximizes the total entropy. 'Ground state' is meant to include both single particles in their ground state, and the absence of collective excitations such as phonons. Yet zero-point energy will remain.

 

[Drakkith]

I got this from wikipedia on temperature:

The process of cooling involves removing thermal energy from a system. When no more energy can be removed, the system is at absolute zero, which cannot be achieved experimentally. Absolute zero is the null point of the thermodynamic temperature scale, also called absolute temperature. If it were possible to cool a system to absolute zero, all motion of the particles comprising matter would cease and they would be at complete rest in this classical sense. Microscopically in the description of quantum mechanics, however, matter still has zero-point energy even at absolute zero, because of the uncertainty principle.

ALSO I found this:

This function is the variation of the internal energy with respect to changes in the entropy of a system. Its natural, intrinsic origin or null point is absolute zero at which the entropy of any system is at a minimum. Although this is the lowest absolute temperature described by the model, the third law of thermodynamics postulates that absolute zero cannot be attained by any physical system.

Also on Zero Point Energy, AKA the ground state:

Because of the uncertainty principle, every physical system (even at absolute zero temperature) has a zero-point energy that is greater than the minimum of its potential well. Liquid helium-4 (4He) remains liquid—it does not freeze—under atmospheric pressure no matter how low its temperature is, because of its zero-point energy.

So it looks to me like you cannot get to absolute zero because of the uncertainty principle AND because of the laws of thermodynamics.

 

[Rage Crank]

Back to the original question. Its merely hypothetical. I know that Absolute zero cannot be achieved, Think of it as cutting something in half. You can always cut something in half no matter how minute the amount is is.
Its simply a theory I have came up with but doesn't the universe have to be revolving around something? think about it. The mon revolves arround the earth, which revolves around the sun which revvles arround what? and that revolves around what? The universe has to have a velocity, It only makes sense. atleast to me. I would love hear peoples opinions. What would happen to my original question?
This is why you need to cut out kinetic energy as well.

"A system at absolute zero still possesses quantum mechanical zero-point energy, the energy of its ground state. The kinetic energy of the ground state cannot be removed. However, in the classical interpretation it is zero and the thermal energy of matter vanishes. wikipedia

It states that the Kinetic energy cannot be removed. Well if we look at this from a relative stand point we can remove the kinetic energy. take this for example. If a person shoots a gun he sees the bullet as having kinetic energy. however if you are moving at the same velocity as the bullet you see it as sanding still. no kinetic energy.

So my question is what happens to an object if there is absolutely no energy in it.
Lets say we took the spacecrft out pf the equation would something different happen to it? would the actual outcome depend fully on your realtive posistion to the object at absolute zero? I don't know if anybody followed me but if you did think about it and reply, I am very interested.

 

[Drakkith]

Its simply a theory I have came up with but doesn't the universe have to be revolving around something? think about it. The mon revolves arround the earth, which revolves around the sun which revvles arround what? and that revolves around what? The universe has to have a velocity, It only makes sense. atleast to me. I would love hear peoples opinions. What would happen to my original question?

Sorry, nowhere in science is the universe required to have a velocity. If it did, then you would get into the question of a velocity in relation to what? Another universe?

It states that the Kinetic energy cannot be removed. Well if we look at this from a relative stand point we can remove the kinetic energy. take this for example. If a person shoots a gun he sees the bullet as having kinetic energy. however if you are moving at the same velocity as the bullet you see it as sanding still. no kinetic energy.

Temperature is the measure of the kinetic energy of all the particles in an object. Every particle is vibrating, rotating, and moving (in some cases) in different directions. It is NOT a measure of the kinetic energy of the whole object in one direction.

So my question is what happens to an object if there is absolutely no energy in it.
Lets say we took the spacecrft out pf the equation would something different happen to it? would the actual outcome depend fully on your realtive posistion to the object at absolute zero? I don't know if anybody followed me but if you did think about it and reply, I am very interested.

You cannot remove ALL energy from an object. That is why we cannot reach absolute zero. Asking what would happen if we could is pointless, as we cannot and because of that we don't know.

 

[Rage Crank]

Okay, finally I understand. Thank you all. I was having a bit of a mental block. But that you for all the help.