Use the power of the sun to drive the vanes in this traditional radiometer. Place on a windowsill or in an area that has sunlight and solar energy will create energy to work the radiometer. Made in the USA.
The vanes, or wings, in the Radiometer are alternately dark and light in colour. 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-coloured reflective vanes, they take on very little energy and do not bounce off very fast.
However, when the atoms strike the dark vanes, they "kick" away at terrific speed. Results: 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.