The birth of statistical mechanics

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Discussion Overview

This discussion explores the historical development of statistical mechanics, particularly the transition from classical to quantum approaches. Participants examine the role of early physicists like Maxwell and Boltzmann, and the implications of treating energy as a continuous parameter in classical statistical mechanics.

Discussion Character

  • Historical
  • Exploratory
  • Conceptual clarification

Main Points Raised

  • One participant notes that statistical mechanics appears to incorporate quantum mechanics from its inception, contrasting it with other physics areas that develop classical theories first.
  • Another participant confirms the existence of a "classical statistical mechanics" where energy is treated as a continuous parameter, but emphasizes the need for binning position and momentum to derive sensible densities of states.
  • A different viewpoint suggests that classically, a particle can have an infinite number of energy states, proposing a uniform probability distribution for energy between 0 and E.
  • Participants reference historical contributions from figures like Maxwell and Boltzmann, with one mentioning the Gibbs paradox and its resolution through quantum mechanics.

Areas of Agreement / Disagreement

Participants express varying interpretations of classical statistical mechanics and its relationship to quantum mechanics, with no consensus reached on the specifics of energy quantization or the implications of classical distributions.

Contextual Notes

Participants discuss the limitations of classical approaches in addressing phase space and energy quantization, highlighting unresolved issues in the transition to quantum statistical mechanics.

ShayanJ
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This topic is about history of physics so I decided to post it in general physics section but it would be nice to have a history of physics(or maybe science)section.
Anyway,during my statistical mechanics course,I realized QM is being used from the beginning,in contrast to other parts of physics where a classical theory is developed first and then there are quantum corrections.So I wondered whether there was a time that there was classical statistical mechanics.I know,you now tell "of course there was" but by classical statistical mechanics I mean not considering energy levels and degeneracies and considering energy as a continuous parameter.
I found Boltzmann's 1877 paper at http://www.trivialanomaly.com/ and took a look at it.In it,boltzmann assumes that particles can take velocities of the form \frac{p}{q} and also he assumes that the energy(he uses the term "alive force" which I think he means energy)of any particle is an integer multiple of a constant factor.
Also in http://arxiv.org/pdf/physics/9710007.pdf , it is said that Max Planck was inspired by Boltzmann's ideas in his theory about black body radiation.
We know that maxwell independently had discovered maxwell-boltzmann distribution.I want to know had maxwell also have the idea of energy quantization or he just derived the distribution experimentally?
Also I will appreciate any ideas about classical statistical mechanics and whether there is a distribution which considers energy as a continuous parameter.
Thanks
 
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Yes, there is a "classical statistical mechanics" in which energy is considered as a continuous parameter - or, more precisely, energy is a function of the continuous state variables of position and momentum. However, it turns out that in order to write down sensible densities of states, etc., you need to bin the positions and momentum. The bin widths ##\Delta x## and ##\Delta p## end up entering into the density of states as the product ##\Delta x \Delta p##, so modern treatments tend to use our knowledge of quantum mechanics to identify this bin area with ##\hbar## (raised to the appropriate power if in 2 or 3 dimensions).

See, for example, sections 3.6 and 4.3.2 of Tobochnik and Gould, available online here: http://stp.clarku.edu/notes/
 
Yeah,my thoughts also led me to the result that classically,a particle has infinite number of choices for its energy content.So I concluded that for finding a classical energy distribution,a different approach should be taken.
Maybe we can tell that every energy between 0 and E is equally probable and probability distribution is 1/E.
 
Statistical mechanics - Wikipedia, the free encyclopedia has a short history, mentioning several contributors who lived well before the discovery of quantum mechanics. Contributors like James Clerk Maxwell and Ludwig Boltzmann, who worked half a century before.

ETA:
Gibbs paradox - Wikipedia, the free encyclopedia mentions the problem of what to do about phase space in the classical limit. It also mentions a problem with counting that quantum mechanics successfully resolves. Its discoverer, Josiah Willard Gibbs, Jr., had died in 1903.
 

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