Nichols radiometer

Have you ever seen a windmill and noticed how it spins when the wind blows? Something very similar happens with the Nichols Radiometer, but instead of wind, it uses light to make a small device spin.

A Nichols Radiometer is a very special tool that helps scientists study light. It's made of a small glass bulb with a few metal blades inside. The bulb is not completely sealed, which means that air can still move inside it.

When light shines on the blades, the colors of the light get absorbed and reflected differently from each blade. This causes the air around each blade to heat up differently, which creates a difference in air pressure. When air pressure differs on both sides of the blade, it causes the blade to move.

As the blades spin, they move a tiny pointer on the device, telling scientists how much light is shining on it. Some people use it to see if their light bulbs are providing enough light or if their sunscreen is blocking enough of the sun's harmful rays.

Even though the Nichols Radiometer is a simple device, it has helped scientists understand more about light and how it behaves.