General description This magnificent 4 Blades Rotating Glass Windmill, also known as a glass radiometer, is a stunning decorative piece that makes a great gift for anyone who has everything. It beautifully demonstrates how sunlight is converted into energy, providing both aesthetic appeal and educational value. Technical specifications Globe diameter: 3.5 inches Height: 8 inches Material: Glass Color: Photo Color Measurement allowed error: +/- 1-3 cm Usage Place the windmill near a window or under incandescent light to observe the vanes rotate. The vanes rotate in response to sunlight, artificial light, or even infrared radiation. The darker sides of the vanes retreat from the light source while the lighter sides advance, creating movement. Other information Invented in 1873 by chemist Sir William Crookes, the radiometer operates in a partial vacuum. Inside the glass bulb, a rotor with four vertical metal vanes is mounted on a low friction spindle. Note: Light reflection and different