Radiometer - Light Mill for sale. Buy from The Science Company.

The Sphere Powered by the Sun!

Set the radiometer in the sun or bright light and watch the vanes spin! More light, more spin!

The vanes, or wings, in the Radiometer are alternately dark and light in color. When the light strikes these wings, it transfers heat to each one - but not to the same degree. The lighter wing reflects the rays, and the dark wing absorbs the rays. Now, when the freely moving particles of air inside the radiometer strike the light-colored reflective vanes, they take on very little energy and do not bounce off very fast. However, when the atoms strike the dark vanes, they take on a great deal of energy...and "kick" away at terrific speed. Result: The vane begins to spin and continues to spin as the bits of air continue to "kick" away from the dark-sided vane. Naturally, the stronger the light, the more energy there is to "heat up" the dark side of the wing...causing the vanes to spin faster and faster as the light gets brighter.