On Thu, Apr 04, 2019 at 08:21:38PM +0000, Phil Pugliese (via tml list) wrote:
> So the stars/suns contained in it have pumped out an unbelievably
> enormous amount of energy into a basically 'closed system'. (no
> 'expanding universe' here, AFAIK) So what happened to all that
> energy?  Both 'conventional' & TU 'handwavium' speculation welcomed!

If it's even a half-decent size (say, at least 0.1 parsecs across)
then it wouldn't make much difference in such a short time frame.  All
the energy pumped out could still be building up in the space and it
wouldn't get hot enough to matter for millions more years.

Using as example a wrap-around cube 0.1 parsecs across and containing
one Sol-like star, the average flux after a million years would be
3000 lux.  This would certainly be bright: similar to a cloudy day on
Earth everywhere in space.  However, it would not be hot: an object
fairly distant from the star would reach an equilibrium temperature of
about -120 C.  Things would not be heating up to human-scale
temperatures until another ten million years passed.

For larger spaces, the timescale before things get hot goes up with
the cube of the diameter.  A space that is a full parsec across with
one Sol-like star in it gives about ten billion years before getting
warm.

- Tim