Experience this sphere powered by the sun! 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 at the same degree. The lighter wing reflects the rays and the darker wing absorbs. The stronger the light, the more energy there is to heat up the darker side of the wing causing the wings to spin faster. It spins under the solar light or a regular light bulb. Great for science projects, as a gift or as a desk amusement! For ages 8 and up.