Re: Penrose and Entropy


MitchAlsup@xxxxxxx wrote:
rev.goetz wrote:
MitchAlsup@xxxxxxx wrote:
rev.goetz wrote:
Roger Penrose calculates entropy by the number of photons per baryon.
And whenever I asked a physics graduate student about this, they where
not sure why. I wonder if it makes more sense to calculate entropy by
the number of photons per gluon. Does anybody know why Penrose
calculates entropy by the number of photons per baryon?

To a very first order, we have means to measure the number of photons
and the number of baryons, but we do not have the means to measure the
number of gluons. So, we base the model on what we can measure.

Okay. Do you know why the number of photons per baryon tend to increase
in the universe? IIRC, we now have roughly 10^8 photons per baryon, and
if we collapse into a black hole, then the black hole would have at
least 10^20 photons per baryon.

The physics inside a black hole allow those photons to be converted (by
e=m*c**2) back into mass (m = e/c**2) via some particle or other
degenerate physical state. All we can tell from the outside is {mass,
charge, spin}.

Do you hae a reference that substantiates you assertion that the number
of photons per baryon increases with time?

My figures come from the following article.

R. Penrose, "Time-Asymmetry and Quantum Gravity," in Quantum Gravity 2:
A Second Oxford Symposium eds. C.J. Isham, R. Penrose, and D.W. Sciama
(Oxford: Clarendon Press, 1981), 245-72.

James

.

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