thanks for the answer antoniseb

one more thing, can photons go through matter?

Basically imagine this scenario... we have a room (10 meters cubed), the walls are made of the most dense material in the world(Osmium perhaps? or maybe some supercooled/liquid gas), and the walls are lets say 100 meters thick. When we finish that...we put a very powerful light source inside, would the photons from the light source ever "get out"? or would they be trapped forever? or would they dissapear (get absorbed somehow)

oh and do photons "live" forever, as in when a photon is created, does it ever vanish for whatever reason, or does it just keep "bouncing around" forever

now a similar scenario...same thing as above, but the walls are supercooled to near absolute zero temperatures..what would happen then?

i know motion is supposed to stop at absolute zero..does this include photons and gravitons (assuming gravitons exist)?