Invented in 1873 by chemist Sir William Crookes as a byproduct of some chemical studies, the radiometer is made from a glass bubble from which most of the air has been removed, creating a partial vacuum. Inside the bubble, on a low friction spindle, there is a rotor with several (usually four) vertical, lightweight metal blades evenly distributed around the axis. Shoulders on one side polished or white, on the other black. When exposed to sunlight, non-mechanical light or infrared radiation (even the warmth of a hand nearby may be enough), the blades do not have visible driving force, the dark sides withdraw from the radiation source, and the bright sides move forward. Simply place near a window or under direct incandescent light, as the blades only rotate in light (solar light or incandescent light). The more light shines on the globe, the faster the blades rotate. Specifications: Material: Szkło Color: ClearBase Size: 80 mm / 3,1 "Height: 205 mm / 8,1" Ball diameter: 90 mm / 3,5 "Features: Great glass radiometer, it's a great prezent for those who have everything. All made of glass. The globe ma a diameter of 3,5 inches and a height of 8 inches. This physical and technical miracle clearly shows how sunlight is converted into energy. Place near a window or in incandescent light and watch the blades rotate. Pls make sure you don't mind before you make an offer. 2. Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.