Quote Originally Posted by Ronin
I remember an old experient in physics class back in high-school that would prove that light has mass.....

it consisted of a glass container that was in a vacuum situation, in this container there was this device that kinda looked like a top, it was set in an axil that allowed it to spin, now...one of the sides of this thing was reflective, with the oposite side was black......when sun light shined on this device the little top thing inside spun around.....I can´t remember the name of the bloody thing in portuguese let alone in english...but if i can find a picture i´ll post it.
It's a radiometer, but it doesn't prove that light has a mass. The experiment proves that the gas molecules inside (the thing doesn't contain a complete vacuum) take heat off the black side, expanding the gas on the black side of the squares, resulting in differences of pressure (pushing the black side a bit) and resulting in a flow of gas molecules around the little squares from the colder side to the warmer, giving the spinning thing more speed.