Santa Radiometer: a St. Nick themed classic physics toy- a light powered ornament for a tree near a sunny window. This device goes way back, invented in 1873 by the famous chemist Sir William Crookes when he was investigating partial vacuum environments. Light heats up the “vanes” which then heat up the very thin gas left in the partial vacuum within the bulb- the black side of the vane is hotter than its reverse and any gas molecule that comes into contact with it flies off at a faster speed im