On 1/18/2012 11:13 AM, Evgenii Rudnyi wrote:
On 18.01.2012 18:47 John Clark said the following:
On Sun, Jan 15, 2012 at 3:54 PM, Evgenii Rudnyi<use...@rudnyi.ru>

" Some physicists say that information is related to the entropy"

That is incorrect, ALL physicists say that information is related to
entropy. There are quite a number of definitions of entropy, one I
like, although not as rigorous as some it does convey the basic idea:
entropy is a measure of the number of ways the microscopic structure
of something can be changed without changing the macroscopic
properties. Thus, the living human body has very low entropy because
there are relatively few changes that could be made in it without a
drastic change in macroscopic properties, like being dead; a bucket
of water has a much higher entropy because there are lots of ways you
could change the microscopic position of all those water molecules
and it would still look like a bucket of water; cool the water and
form ice and you have less entropy because the molecules line up into
a orderly lattice so there are fewer changes you could make. The
ultimate in high entropy objects is a Black Hole because whatever is
inside one on the outside any Black Hole can be completely described
with just 3 numbers, its mass, spin and electrical charge.

John K Clark

If you look around you may still find species of scientists who still are working with classical thermodynamics (search for example for CALPHAD). Well, if you refer to them as physicists or not, it is your choice. Anyway in experimental thermodynamics people determine entropies, for example from CODATA tables


S ° (298.15 K)
J K-1 mol-1

Ag  cr  42.55 ą 0.20
Al  cr  28.30 ą 0.10

Do you mean that 1 mole of Ag has more information than 1 mole of Al at 298.15 

Yes, it has more internal degrees of freedom so that it takes addition of more energy in order to increase those we measure as temperature.


Also remember that at constant volume dS = (Cv/T) dT and dU = CvdT. If the entropy is information then its derivative must be related to information as well. Hence Cv must be related to information. This however means that the energy also somehow related to information.

Finally, the entropy is defined by the Second Law and the best would be to stick to this definition. Only in this case, it is possible to understand what we are talking about.


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