[LMB] Old Moldy OT:

Joel Polowin jpolowin at hotmail.com
Thu May 11 17:16:42 BST 2006


James <cessnadriver at gmail.com> wrote:
>I don't know if this happened, but since it deals with chemistry or
>physics... calculating temperatures and ending up with -300 degrees
>Ceslus? Has that happened?

In (bad) SF?  The Trek NextGen episode "The Royale" had a planetary
surface temperature of "minus 291 degrees Celsius".

In reality?  The temperature of a system at equilibrium is determined
by the distribution of energy states of its components.  In a system
at absolute zero, all the components would be in their lowest
possible energy states; as the temperature rises, statistically,
there's a shift of an increasing portion of the components into
higher energy states.  But the usual calculation of theoretical
temperature from the distribution assumes that the system is at
equilibrium, and if the distribution is weird, the temperature
calculated from it may also be weird.  I'm rusty on this kind of
calculation (and never was very good at it!) but I seem to recall
that if there's a "population inversion" -- basically, that the
proportion of system components in a high energy state is higher
than the proportion in a low state -- the calculated temperature
comes out below absolute zero.  (In such a situation, the system
is set up to dump a lot of energy so as to get back to a normal
distribution -- for example, population inversion is required for
a classic laser to emit.)

Joel




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