<ul><li>Vanes in the Radiometer are alternately dark and light in color</li><li>Vanes transfer heat to each one but not at the same degree</li><li>Lighter vane reflects the rays and the darker vane absorbs the rays</li><li>For ages 8 and above</li></ul><br><br>Product Description\n\nRadiometer\n\nFrom the Manufacturer\n\nIt\'s the spear powered by the sun! When light strikes the diamond wings it tranfers heat to each one, but not to the same degree. The light wing reflect the rays and the darker wing absorbs the rays. The stronger the light the more energy there is to heat up the darker side causing the wings to spin faster.