Re: Ludwig Boltzmann, entropy

Tim Tyler <tim@xxxxxxxxxxx> wrote:
>Paul J Gans <gans@xxxxxxxxx> wrote or quoted:
>> Tim Tyler <tim@xxxxxxxxxxx> wrote:
>> >rnorman <rnorman@xxxxxxxxx> wrote or quoted:

>> >> The fact is, information in the Shannon sense is most definitely a
>> >> notion closely related in formulation to the statistical dynamical
>> >> notion of entropy as a measure of a subset of states. Tim Tyler is
>> >> sort of partially on the right track. Paul Gans is correct, though.
>> >> It is NOT true that entropy is an information-theoretic notion. I
>> >> don't believe any information theorist really claims this.
>>
>> >Entropy *is* in information theoretic notion. It is just not
>> >*only* an information theoretic notion.
>>
>> >Where it's important to distinguish between the terms, people use
>> >terms like "information entropy" and "thermodynamic entropy".
>>
>> >The distinction is pretty irrelevant to this thread, though.
>>
>> >The discussion started with the question of whether the number of
>> >microstates in physical systems was known. They are not known for any
>> >physical system - unless you adopt a notion of microstates tht bundles
>> >similar velocities together, and call them indistinguishable - and if
>> >you do that there's no generally agreed-upon framework that dictates
>> >what granularity of "bucket" you can use - and different size buckets
>> >produce different results for the number of microstates involved.
>>
>> I'm sorry but this is wrong. And has been known to be wrong
>> since about 1910. That was the period in which Sakur and
>> Tetrode worked out the size of a microstate. It turned out
>> to be Planck's constant to the third power.
>>
>> With the development of quantum mechanics and the Heisenberg
>> uncertainty principle came an understanding of *why* that
>> was the size of a microstate.

>Microstates don't have a size. They are configurations.
>Classically, each microstate of a system is a statement about
>the position, momentum and nature of particles in the system.

>> This isn't just speculation. That's the number you need
>> to use in the appropriate equations to calculate the entropy.
>> And that entropy agrees with experiment.
>>
>> Got it?

>No. There may be more states than you claim - or fewer states.

>HUP doesn't place a limit on the number of states the universe
>can take, it's a limit on what knowledge embedded observers
>can obtain about that state - a different concept.

>The entropies calculatied using Boltzmann's constant from thermodynamic
>parameters are based on hypotheses about the particulate nature of
>matter, the lack of other properites apart from positon and velocity,
>the assumption that all the relevant particles are known about, and
>speculation about the granularity of the universe. The results from
>this model may be interesting - but they should not be mistaken for
>what's going on in the real world in any volume of spacetime.

Well, we'll have to agree to differ. But you might
read a book or two on thermodynamics, statistical
mechanics, and quantum mechanics.

---- Paul J. Gans

.

Relevant Pages

  • Re: Ludwig Boltzmann, entropy
    ... >>>particles in the system are completely specified. ... it takes three numbers to define a particle's velocity in three ... It also makes no difference at all because quantum mechanics ... Microstates *must* be discrete. ...
    (talk.origins)
  • Re: How to calculate entropy of particles?
    ... particles, so temperature is no problem to calculate. ... This formula tells me something about how the entropy would change ... it's a measure of how many microstates are ... by random fluctuation, more molecules will in general be in ...
    (sci.physics)
  • Re: How to calculate entropy of particles?
    ... particles, so temperature is no problem to calculate. ... This formula tells me something about how the entropy would change ... it's a measure of how many microstates are ... or thermodynamics, so initial meaning of word entropy is often ...
    (sci.physics)
  • Re: How to calculate entropy of particles?
    ... Each particle has a position, a mass, and a velocity. ... how would you calculate the entropy of the particles? ... You are correct, your entropy is going to be infinite if you consider only classical mechanics, because number of states is infinite. ... What makes entropy of a real system of particles non-infinite is the quantization of the phase space of impulses according to quantum mechanics. ...
    (sci.physics)
  • Re: Ludwig Boltzmann, entropy
    ... >>microstates in physical systems was known. ... momentum and nature of particles in the system. ... > to use in the appropriate equations to calculate the entropy. ...
    (talk.origins)
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