Okay, if you do not know what the radiometer is you will be amazed at watching the vane spin and the light brighten. Well, this is one of those things that have been around forever. The glass stands at five inches high and is three inches in diameter at the top. The vane has four blades, which is on a needle inside the sphere. The opposite surfaces of the vane are black and white radiant, which makes the radiant energy be either absorbed or reflected to a different degree. The end result is the spinning vane you see. The brighter the light gets the faster it spins. An instruction sheet is included.

To learn more or to purchase the radiometer, click here.