On 3/13/2012 12:44 PM, Evgenii Rudnyi wrote:
On 13.03.2012 20:32 meekerdb said the following:
On 3/13/2012 12:26 PM, Evgenii Rudnyi wrote:
On 13.03.2012 20:09 meekerdb said the following:
On 3/13/2012 10:28 AM, Evgenii Rudnyi wrote:


Could you please give one example from physics (yet please not a
thought experiment) where information allows us to reduce entropy?


Thanks a lot. I will look at this.

As fas a I remember, you have told previously that information in
physics is the entropy,

I think your memory is wrong. Please cite where I said that.

In my collection I have this quote for example


25.01.2012 21:25 Brent: “The thermodynamic entropy is a measure of the
information required to locate the possible states of the plates in
the phase space of atomic configurations constituting them. Note that
the thermodynamic entropy you quote is really the *change* in entropy
per degree at the given temperature. It’s a measure of how much more
phase space becomes available to the atomic states when the internal
energy is increased. More available phase space means more uncertainty
of the exact actual state and hence more information entropy. This
information is enormous compared to the “01″ stamped on the plate, the
shape of the plate or any other aspects that we would normally use to
convey information. It would only be in case we cooled the plate to
near absolute zero and then tried to encode information in its
microscopic vibrational states that the thermodynamic and the encoded
information entropy would become similar. ”

Yes, that clearly states that entropy is equal to the information that
would be required to eliminate the uncertainty as to the exact state in
phase space. It's *the missing* information when you only specify the
thermodynamic variables. So what is strange about that? Dollars are a
measure of debt, but that doesn't mean you have a lot of dollars when
you have a lot of debt.

What is the difference with what I have said previously? Entropy and information are related, that is, if I know the entropy, I can infer information and vice versa, so in essence the entropy is information.

But the thermodynamic information, what you get from the JANAF tables, is the missing information when you just specify the thermodynamic variables. If you specify more variables there will be less missing and the entropy will be lower. If you specified the exact state of every atom the entropy of the system would be zero. So the two are not the same, they are complementary; like debt and wealth: both are measured in money but more of one means less of the other.


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