Lily's Home Solar Radiometer Crookes Light Mill for Detecting Sunlight and Electromagnetic Radiation, Fascinating and Functional Gift Ideal for Student or Science Guru, Clear Sphere, 4" Dia. Clear

Lily's Home Solar Radiometer Crookes Light Mill for Detecting Sunlight and Electromagnetic Radiation, Fascinating and Functional Gift Ideal for Student or Science Guru, Clear Sphere, 4" Dia. Clear

Invented in 1873 by the chemist Sir William Crookes as the by-product of some chemical research, the radiometer is made from a glass bulb from which much of the air has been removed to form a partial vacuum. Inside the bulb, on a low friction spindle, is a rotor with several (usually four) vertical lightweight metal vanes spaced equally around the axis. 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 more light shine on the globe the faster the vanes rotates.