Radiometer on brass stand (small)

Transparent radiometer on a brass stand, small model (exist in large: RA001) - Sir William Crookes’ radiometer (1873) consists of a partial air vacuum inside a glass ball, which contains a set of vanes in mica mounted on a spindle, creating the less friction as possible. The four vertical vanes equally spaced around the axis, presents one side black and the other bright: the dark face absorb photons of infrared light and become warmer than the white one (where photons are repulsed). With rising temperatures the air expands, molecules close to the black side moves away from each other, and pushes the vane, creating rotating motion as if by magic! A complex object but so interesting...