Is it possible to achieve absolute zero?

[William Henley]

Is it possible to achieve absolute zero?

 

[ShayanJ]

No!

 

[OCR]

No!

So it is...

The laws of thermodynamics dictate that absolute zero cannot be reached using only thermodynamic means, as the temperature of the substance being cooled approaches the temperature of the cooling agent asymptotically. A system at absolute zero still possesses quantum mechanical zero-point energy, the energy of its ground state at absolute zero. The kinetic energy of the ground state cannot be removed.

http://en.wikipedia.org/wiki/Absolute_zero

 

[Chestermiller]

Is it possible to achieve absolute zero?

Only if you do very poorly on your thermo exam.

Chet

 

[Thermo]

But how is it possible that there is no place below -273 cantigrate degrees in the universe?

 

[davenn]

But how is it possible that there is no place below -273 cantigrate degrees in the universe?

Centigrade

why do you feel the need for there to be something at absolute zero ?

Did you read the link given in post #3 above explaining the conditions at absolute zero ?Dave

 

[Thermo]

There are empty areas between galaxies. I mean no any sun nearby not even 100000000000000000000 light year nearby. Aren't they even below -273,15?

Just because a chart that shows that volume is zero at absolute zero. I can't be convinced there isn't a -273 cEntigrade degrees out there. This volume thing at 0 point is not even experimental but a chart assumption.

 

[davenn]

This volume thing at 0 point is not even experimental but a chart assumption.

no, incorrect

I'll ask again ... did you read that wiki link ?

about the coldest thing you will find out there is the cosmic microwave background which is about 3 Kelvin (ie. 3 deg above absolute zero)
This permeates the universe everywhere between the galaxies So it pretty much predetermines the coldest temperature you will find
Dave

 

[Thermo]

You don't need to humiliate me. That's why students don't ask questions their mentors. Anyway, yea I've read it but then it is not polynomial degradation when you leave the sun to the outer space? Because you will achieve the 0 or even below if you do so.

 

[jbriggs444]

but then it is not polynomial degradation when you leave the sun to the outer space? Because you will achieve the 0 or even below if you do so.

Probably you are thinking of exponential degradation. That pattern arises when you have a hot object that transfers heat to an infinitely large cold reservoir and the rate of heat loss is proportional to the temperature difference. The hot object cools down and its temperature asymptotically approaches the temperature of the cold reservoir.

Given the cosmic microwave background at 3 degrees kelvin, the temperature that is approached is 3 degrees kelvin, not absolute zero.

 

[Vanadium 50]

That's why students don't ask questions their mentors

If you were asking questions, I'd have a little more sympathy. But you're not - you are making statements like "This volume thing at 0 point is not even experimental but a chart assumption." If you don't like being told your statements are wrong, maybe you should stop making wrong statements.

 

[Thermo]

Our lecturer said it is because of the V-T chart. But maybe he didn't want to mention more. I am sorry for my behaviour didn't mean to make statements but tried to understand.

 

[OCR]

about the coldest thing you will find out there is the cosmic microwave background which is about 3 Kelvin (ie. 3 deg above absolute zero)

There could be some exceptions...?

http://en.wikipedia.org/wiki/Boomerang_Nebula
http://en.wikipedia.org/wiki/CMB_cold_spot

 

[Neandethal00]

Only if you do very poorly on your thermo exam.

Chet

ha ha , very funny answer.
But seriously, didn't absolute zero come from a theoretical vanishing 'volume' of gas or object?
How can anyone justify zero volume of anything? This tells us the theory breaks down before temperature reaches absolute zero.
Another way of saying, temperature below absolute zero is possible in an unknown state of matter.

 

[PeterDonis]

didn't absolute zero come from a theoretical vanishing 'volume' of gas or object?

No. Absolute zero has to do with temperature, not volume. It's perfectly possible to describe mathematically a system at absolute zero with finite volume.

 

[PeterDonis]

a chart that shows that volume is zero at absolute zero

What chart are you talking about? Do you have a reference?

 

[PeterDonis]

how is it possible that there is no place below -273 cantigrate degrees in the universe?

Because there has to be a state of minimum possible energy. Absolute zero is that state.

 

[Vanadium 50]

I think they are arguing that all we know about absolute zero came out of Charles' Law, as if no progress was made in the intervening two centuries.

 

[Drakkith]

But how is it possible that there is no place below -273 cantigrate degrees in the universe?

Zero kelvin, or -273.15 centigrade, is the temperature at which the atoms/molecules that compose an object would be solely in their ground states. The ground state is the minimum energy level for that atom/molecule, so at absolute zero an object would have the least internal energy possible. There is literally no other internal energy for it to give up.

 

[ShayanJ]

Zero kelvin, or -273.15 centigrade, is the temperature at which the atoms/molecules that compose an object would be solely in their ground states. The ground state is the minimum energy level for that atom/molecule, so at absolute zero an object would have the least internal energy possible. There is literally no other internal energy for it to give up.

I think that's not the proper way of saying it. Its better to say, at absolute zero, by definition, particles will have zero energy. But because any system has a ground state energy which is greater than zero, no system can reach absolute zero.

 

[Vanadium 50]

I think that's not the proper way of saying it. Its better to say, at absolute zero, by definition, particles will have zero energy. But because any system has a ground state energy which is greater than zero, no system can reach absolute zero.

I'm sorry, but that's not correct. Drakkith's message is right.

 

[ShayanJ]

I'm sorry, but that's not correct. Drakkith's message is right.

No need to be sorry!
What I understand from he's message is that absolute zero is where the system(of course a system for which we can define temperature) is in its ground state. Now if we say absolute zero can't be reach, we're actually saying that we can't have such a system in its ground state even in principle. That seems wrong to me but maybe I'm just getting things wrong.
Also as far as I remember from thermodynamics, its the definition of absolute zero that the motion of all particles stop at this temperature which means zero energy.

 

[Drakkith]

Now if we say absolute zero can't be reach, we're actually saying that we can't have such a system in its ground state even in principle. That seems wrong to me but maybe I'm just getting things wrong.

No, that's pretty much correct. It isn't possible for objects larger than atoms and perhaps small molecules to reach their ground state through thermodynamic means.

 

[ShayanJ]

No, that's pretty much correct. It isn't possible for objects larger than atoms and perhaps small molecules to reach their ground state through thermodynamic means.

If you're talking about the 3rd law of thermodynamics(at least its Nernst's statement), then its about absolute zero, not the ground state. So what you're saying is equivalent to defining absolute zero as the temperature the object has when it is in its ground state. So this post actually is equivalent to your last post.

 

[Thermo]

The chart I was talking about. It is not possible to reach that temperature in labs but we can estimate it is zero volume from the chart if we lenghten the line to the -273.15 centigrade degrees.

http://www.avogadro.co.uk/miscellany/t-and-p/charles.gif
Source: http://www.avogadro.co.uk/miscellany/t-and-p/t-and-p.htm

 

[jbriggs444]

The chart I was talking about. It is not possible to reach that temperature in labs but we can estimate it is zero volume from the chart if we lenghten the line to the -273.15 centigrade degrees.

If all you knew about gasses was their volume as a function of moderate temperatures (room temperature and above) and if those observations led you to infer a direct proportion (i.e. Charles law as mentioned upthread) then you could extrapolate to imagine a zero temperature in the neighborhood of -273 degrees Centigrade.

But Charles law is not correct. It is an approximation that works well for diffuse gasses -- at scales and precisions where the size of the gas molecules is negligible. It does not work at scales and precisions where the size of the gas molecules is significant. Measurements of gas volume versus temperature near absolute zero will vary significantly from an extrapolated prediction of near zero volumes at near zero temperatures.

When measuring (and defining) low temperatures, you need different measuring techniques and more careful definitions.

 

[f95toli]

Also as far as I remember from thermodynamics, its the definition of absolute zero that the motion of all particles stop at this temperature which means zero energy.

That is not correct. There would still be zero-point motion at 0K. A "hand-wavy" type of argument for this is that otherwise you could violate the uncertainty principle.
Anyway, the calculation showing this can be found in many standard QM textbooks.
Hence, you can't "define" 0K by saying that it is the temperature where everything "stops".

 

[ShayanJ]

That is not correct. There would still be zero-point motion at 0K. A "hand-wavy" type of argument for this is that otherwise you could violate the uncertainty principle.
Anyway, the calculation showing this can be found in many standard QM textbooks.
Hence, you can't "define" 0K by saying that it is the temperature where everything "stops".

You didn't read my last post. What I said was that by that definition of absolute zero and because of uncertainty principle, no system can reach absolute zero. But now people have cast doubt on this kind of reasoning. My point is that, the definition of absolute zero goes back to thermodynamics and the time where there was no QM. So it seems natural to me that it doesn't respect QM. But maybe the community changed the definition. But I've never seen absolute zero being defined as the temperature at which the system is in its ground state.

 

[Vanadium 50]

Absolute zero is the state of minimum energy. How much zero-point energy there is is irrelevant - what matters is that it's at its minimum. One cannot cool beyond it because that would require that it is in a state that is less than its minimum, which is untrue by definition of "minimum". One cannot reach it because there is no way to take a system at temperature A and another system at temperature B (A and B might be quite cold) and end up with a system at temperature 0 and one at temperature C without some heat flowing from cold to hot. That's impossible.

It has nothing to do with the uncertainty principle.

 

[f95toli]

It has nothing to do with the uncertainty principle.

Indeed. What I was referring to was the fact that things can still move (or at least fluctuate) at 0K. This is obviously a "pure" QM effect since classically one would have expected the kinetic energy to be zero.
if you want you can think about this motion a "quantum noise", i.e. a type of "intrinsic" fluctuation.
However, the fact that you can't reach 0K has nothing to do with the uncertainty principle, or even with QM effects as such.
Sorry if I wasn't clear.

 

[Neandethal00]

You don't need to humiliate me. That's why students don't ask questions their mentors. Anyway, yea I've read it but then it is not polynomial degradation when you leave the sun to the outer space? Because you will achieve the 0 or even below if you do so.

Don't feel bad. Posters in this forum act like they have solved all the mysteries of the universe. Just get used to them.

Many of you here are missing one point. Temperature, energy and many other physical variables have and measured from a Reference point. One direction from the reference point is positive and opposite direction is negative. Celsius temperature scale is the most simplest example, reference point is 0^OC, freezing of water and blah blah, you already know it.
My question is "Why absolute zero is not a reference temperature"?

 

[Drakkith]

Don't feel bad. Posters in this forum act like they have solved all the mysteries of the universe.

No, we just hold people to a higher standard in discussions than most other people do.

Many of you here are missing one point. Temperature, energy and many other physical variables have and measured from a Reference point. One direction from the reference point is positive and opposite direction is negative. Celsius temperature scale is the most simplest example, reference point is 0OC, freezing of water and blah blah, you already know it.
My question is "Why absolute zero is not a reference temperature"?

It's not a reference point in the way you're thinking because there is only a finite amount of energy that can be given up by an object. This is called its internal enregy. At absolute zero all of this internal energy is gone. There is no more for it to give up, hence the object cannot go below absolute zero, and because of thermodynamics it can't even reach absolute zero. We've taken the zero point on our kelvin temperature scale and set it to absolute zero so that nothing can go below zero kelvin.

 

[PeterDonis]

The OP's question, and some additional questions arising from it, have all been answered. Thread closed.