DeepEarthScience

This week I received a package from the USA, containing my own Crookes radiometer (only a few bucks at ThinkGeek.com (Yes, I am a geek, but the good well developed kind ;) )). This device is a small mill with black and white vanes in a vacuum pumped light bulb which turns around when you put it in sunlight (any light works!). It looks like this (pictures speak a thousand words, well in my case a few dozen) My physics teacher used this device to explain that light particles have momentum (he should have known better), and due to the different reaction with the white and black colored vanes, the mill would turn. During my whole life, I was really sure about that this explanation was the effect causing the light-mill in vacuum to turn. Until this week. My old master supervisor (not that he is old, but I am no longer a master student, he is my colleague now) entered my office room with a cup of coffee (this is of course essential for the story) and saw the Crookes radiometer...