Eisco Crookes Radiometer - Round Plastic Moulded Base - Glass Bulb 70mm Diameter

This Eisco Crookes radiometer is an educational science tool which is made of a glass bulb containing a partial vacuum. It's approximately 70mm in diameter, containing a fine spindle which supports four light weight vanes. One side of each vane is darkened, and the reverse side is light.When exposed to a strong bright light, the vanes will turn the spindle. The absorption of radiant energy by the darkened side of the vanes creates a temperature difference compared to the light sides, which causes force to be applied by the air molecules on the darkened side which makes the vanes rotate with their light faces leading. For educational use as proof of principle, these are not suitable to be used as ornaments.