Absolute Zero: Understanding Heat and Molecular Vibrations

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Discussion Overview

The discussion revolves around the concept of absolute zero (-273.15°C), exploring the nature of heat as molecular vibrations and the implications of reaching absolute zero. Participants examine theoretical approaches to achieving absolute zero, including the possibility of stopping molecular motion or removing all molecules, while also considering the quantum mechanical effects that arise at such low temperatures.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants propose that heat is fundamentally linked to molecular vibrations.
  • One participant suggests two methods to reach absolute zero: stopping all molecular motion or removing all molecules, questioning the feasibility of the latter.
  • Another participant argues that a perfectly empty space is impossible due to background radiation and asserts that molecules cannot be completely stopped.
  • Concerns are raised about the classical understanding of absolute zero, with a participant noting that quantum effects complicate the behavior of materials at such low temperatures.
  • It is mentioned that for quantum harmonic oscillators, the lowest energy state does not equate to complete cessation of motion, indicating that molecules do not stop moving at absolute zero.
  • Participants discuss specific phenomena, such as the deBoer effect and superfluidity in helium, as examples of how materials behave near absolute zero.
  • One participant questions whether a space devoid of molecules could theoretically reach 0 Kelvin, prompting further exploration of quantum mechanics and uncertainty principles.

Areas of Agreement / Disagreement

Participants express differing views on the possibility of achieving absolute zero and the implications of quantum mechanics, indicating that multiple competing perspectives remain. There is no consensus on the feasibility of the proposed methods to reach absolute zero or the behavior of materials at that temperature.

Contextual Notes

Limitations include the dependence on classical versus quantum mechanical interpretations of temperature and molecular motion, as well as unresolved questions about the implications of background radiation and quantum effects at low temperatures.

Maxwells Demon
I've been told that heat is vibrations of the molecules.

I see two ways to reach absolute zero -273,15 C

1. you could stop all the molecules so that they wouldn't move at all.

or maybe?? 2. remove all the molecules. No molecules no vibrations no heat??

is no 2. possible?
 
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No. You can't have a perfectly empty space because of the background radiation (or something like it) when you go deep, deep down into the nano-nanometer levels of spacetime.

Also, you cannot stop a molecule from moving. (I may be proven wrong on this a few millenia from now).
 
MadScientist 1000 said:
Also, you cannot stop a molecule from moving. (I may be proven wrong on this a few millenia from now).

I'm a lowly physics I student, but isn't that the whole theory behind 0K? At that temperature molecules cease to move?
 
Feldoh said:
I'm a lowly physics I student, but isn't that the whole theory behind 0K? At that temperature molecules cease to move?

It is if you consider only classical thermodynamics. However, once you get to temperature range that low, quantum effects will kick in and you simply can't extrapolate all that you've known at higher temperatures down to such low temperatures. We have already seen how such things break down when certain material instead becomes a superfluid.

Zz.
 
ZapperZ said:
It is if you consider only classical thermodynamics. However, once you get to temperature range that low, quantum effects will kick in and you simply can't extrapolate all that you've known at higher temperatures down to such low temperatures. We have already seen how such things break down when certain material instead becomes a superfluid.

Zz.

So, in other words we really don't know what will happen at absolute zero 100% of the time?
 
Last edited:
All right assume that the background radiation isn't there...

Hadn't though quantum mechanically on that one, but my question is also just in theory..

Would you have 0 kelvin if you had a space with 0 molecules inside?
 
Feldoh said:
So, in other words we really don't know what will happen at absolute zero 100% of the time?

It depends on the substance.

Note that for a quantum harmonic oscillator, the lowest energy state that it can occupy is \hbar\omega/2. So if you have molecules or solids that can be described by such harmonic oscillators, we already know that they do not stop moving, since there are no lower state than that.

Furthermore, in noble gasses, we have also seen a deviation in the specific heat measurement as you approach very low temperatures. The deBoer effect observed in such measurements can clearly be attributed to such zero-point energy, where by such quantum effects will start kicking in.

Zz.
 
Helium at -271,15 Celsius is a superfluid.. Zapper do you know anything about that? definition?
 
  • #10
In order for a substance to be at absolute zero, it's atoms but be absolutely still. However, if this were the case, we could know the position and momentum (0) of a particle exactly, which goes against quantum mechanical principles.
 

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