P. 4093. The light mill (Crookes radiometer) consists of an airtight glass bulb, in which the air pressure is very low, and in which there are four vanes mounted on a vertical spindle, about which they can rotate. The vanes are polished on one side and black on the other. Why and into which direction do the vanes rotate when they are exposed to light?
Deadline expired on 13 October 2008.