On 4/26/2015 1:18 AM, LizR wrote:
On 26 April 2015 at 13:07, meekerdb <[email protected] <mailto:[email protected]>>
wrote:
Nonsense. He was in poor health and he had long suffered drastic swings in mood.
Today he would be diagnosed as bipolar. He also had reason to be depressed because
his ideas were rejected on the Continent. They were considered crazy
because it was
obviously impossible to derive irreversible processes from reversible
physics.
This was correct. Boltzmann smuggled the arrow of time into his calculations via an
assumption concerning whether their velocities were correlated or independent (I forget
the details, but Huw Price explained it very neatly so even I got it, at least at the
time). However, that wasn't a reason to "throw out the baby with the bathwater" -
thermodynamics still works, of course, if you can get a system into a low entropy state
to start with.
Boltzmann's assumption of uncorreleated velocities worked and he got the thermodynamics of
an ideal gas from stat mech precisely because thermodynamics described gases in terms of
pressure and temperature, a description which ignored those correlations. His great
contribution was to see that entropy was the measure of microscopic degrees of freedom
relative to which macroscopic constraints were assumed. If he'd only lived a few more
years he would have seen his ideas vindicated by Planck's application to black body radiation.
Brent
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