Inside the bulb, on a low friction spindle, is a rotor with several (usually four) vertical metal vanes spaced equally around the . The vanes are polished or white on one side and black on the other. When exposed to sunlight, artificial light, or infrared radiation (even the heat of a hand nearby can be enough), the vanes turn with no apparent motive power, the dark sides retreating from the radiation source and the light sides advancing. Just place near a window or under a direct incandescent light as the vanes only rotates in light (sunlight or incandescent light). The shine on the globe the faster the vanes rotates. Magnificent Glass Radiometer, makes a great gift for who have everything. Subject: Physics All made of glass.This physical and technical miracle shows you in a clear way how sunlight is converted to .Place near a window or under incandescent light and watch as the vanes rotate., Weight: 0.48060773116 Pounds, Manufacturer: Blisfulhoks