Magnificent Glass Radiometer, makes a great gift for someone who has everything. All made of glass. Globe is 3.5 inches in diameter and stands 8 inches tall. This scientific device demonstrates how light energy causes motion. Place near a window or under incandescent light and watch the vanes rotate. Invented in 1873 by chemist Sir William Crookes, the radiometer consists of a glass bulb with a partial vacuum. Inside, a rotor with four vertical lightweight vanes is mounted on a low-friction spindle. Each vane is white on one side and black on the other. When exposed to light—including sunlight, incandescent light, or infrared radiation—the vanes rotate, with the black sides moving away from the light source and the white sides advancing. Rotation occurs only when exposed to sufficient light; increased light intensity results in faster rotation. Color: As shown in image Material: Glass Style: Blue base / Transparent base / Green base Package Contents: 1 x 4-blade rotating glass radiometer Note: Color may vary slightly due to screen settings and lighting conditions. Measurement tolerance: ±1–3 cm.