The radiometer is also known as a light mill, solar power station or the Crookes’ radiometer.  It was invented by the chemist and physicisit Sir William Crookes.  Heat rays from the sun or a bulb warm the dark side of the wings  – and therefore the air around it –  more than on the light side.  The difference in pressure causes the turning motion of  the winged wheel.

Height: 12 cm
Diameter: 8 cm