Magnificent Glass Radiometer, makes a great gift for those who have 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 containing a partial vacuum. Inside, a rotor with four vertical metal vanes is mounted on a low-friction spindle. Each vane is white on one side and black on the other. When exposed to light or infrared radiation, the vanes rotate — the black sides moving away from the light source and the white sides moving toward it. Rotation occurs under sunlight or incandescent light. Brighter light results in faster rotation. Color: As shown in image Material: Glass Type: Transparent base Package Contents: 1 x 4-Blade Rotating Glass Radiometer Note: Light reflection and display settings may cause slight color variation between the image and the actual item. Measurement tolerance is ±1–3 cm.