Solar Radiometer would look awesome sitting on your desk, but it works best when you place it in direct sunlight even though it moves pretty decent with a flashlight. This is a cool radiometer, the bulb where those blades spin is a partial vacuum, the word “partial” is the tricky part. A scientist known by the name of Lbedev noticed that the effect disappeared in a hard vacuum. It means that the light side of the blades is slightly warmer than internal air temperature but cooler than the black side. The air that hangs out by the cool side would flow slowly to the warm side of the blade, making the blade to spin naturally with the help from the sunlight. Science is awesome, isn’t it? [Buy It Here]