Radiometer purple base small

Invented in 1873 by Williams Crookes, to demonstrate the pressure generated by light, the radiometer is composed of a glass sphere emptied of its air, in which is placed, on an axis, a set of 4 mica blades, with a black and a silver face. The difference of temperature of the fins faces creates a move of the air molecules, causing the rotation. A delicate and elegant object

Here in transparent glass, purple base. Height 17 cm. Width 6cm.