I found this radiometer GIF on the internet.
I've had a radiometer for decades, fascinated by the way it spins in the light. It works with sunlight or an incandescent light bulb.
I finally decided to order a new one after mine stopped working.
Here's a photo from the internet that looks just like mine.
Sir William Crroke invented the radiometer.
Below are explanations about how it works.
It's not so simple!