wrote:
Ok here's another thought, if you had two reflective surfaces facing
each other in parallel... and somehow you were able to shine a light
between them...

A. assuming the light source was perfectly aligned, so that the light
strikes the surfaces at right angles with no variation - bouncing back
and forth, over lapping itself.

In practice even with perfect alignment the wave nature of light would
limit the number of bounces, depending on how large your source was
(the larger the better) and how far apart the mirrors were (the closer
the better). Even a laser beam spreads out a lot when you shine it
down a long hall. Using a higher frequency of light would also help.

B. the initial source of light is removed quickly so that the first
reflection/bounce doesn't go back into the source thus
terminating/absorbing the light. When I say quickly... I assume it
would have to be faster than the speed of light to be removed before
the light returned back up to reach it?

No, not unless the light source was at least four times as wide as the
distance to the mirror. The light has further to go. In practice it
might be easier to make the source become transparent, or something
along those lines.

C. the reflective materials contain no imperfections, as the light
reflects back towards the other it is not absorbed or diminished.

Total internal reflection might be useful here, although you'd need to
change the geometry of the experiment a bit.

So you have two materials with a beam of light moving between
them...over and over and over...

Would it stay the same temperature?

Unless light was absorbed, yes.

Would it increase in brightness as the light overlaps itself?

Not unless you brought the mirrors closer together. Energy is
conserved, so it's only going to get dimmer (due to imperfections in
the experimental setup).

Would it eventually destroy the two reflective materials?

After several gazillion overlaps of the light - how dangerous would it
be if one of the two reflective surfaces was removed and the
intense/over lapped light was allow to escape?

WHY do I think of these scenarios?
(Don't bother answering that last one GRIN).
Cheers.