system
Given the following post, respond as if you're commenting on Reddit:
human
Is it possible to completely contain light? Say, in a room designed to trap light particles could you turn on a lamp then shut the lamp off and the room stay lit?



FYI I have no idea how light particles work.
gpt
If you had an emissivity of 0 i.e. a perfect mirror, which doesn't exist.  Each time a photon is absorbed/emitted, there's going to be loss of energy as heat.


Moreover, if you had a room that worked like that - you would be unable to walk into it, since your body would quickly absorb the light and emit it as IR with an energy loss as heat.