system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Where does light go?

If one were in a perfectly sealed room and turned a light on, there would be light in the room and none visible from the outside. However, if the light were turned off, the room would get dark. Why? Where do the light waves go?
gpt
It would get absorbed by everything in the room, including the walls, ceiling, and floor.  That happens even when the light is on--some is absorbed, and some is reflected off, and what you "see" is the light reflected off of, say, a wall.  The light keeps bouncing around the room, until it's eventually all absorbed.  But as long as the light is on, more light keeps bouncing around, and some is absorbed.  As soon as you turn the light off, the light continues to bounce around for a fraction of a second, before it is all absorbed.