Dyson spheres

[Keith F. Lynch]

From: Paul Dietz <dietz%slb-dol...@CSNET-RELAY.ARPA>

But you can't dump heat back into the inside of the sphere, since all you
can see there is other radiating surfaces or the sun.

Sure you can. Don't think of it as a sphere, think of it as
individual small objects. Each object receives light from the sun,
and radiates heat equally in all directions. The fact that the heat
generated in some directions will be intercepted by the sun or by
other of the small objects is not relevant.

The heat must be radiated from the *exterior* of the sphere, which is
visible to interstellar space.

Ultimately, it all is.

I think I see your point, though. Even if there is no net radiation
from the interior sufaces the waste heat will still exert pressure
there (when it is emitted and reabsorbed). A gas of photons in thermal
equilibrium with the radiators, if you will.

This is a more difficult way of thinking of it, but yes.
...Keith