I, and many others, learned a lot about the sun when during the last solar eclipse.

I held a spice shaker lid (ie a disc with several round holes) into the sun and observed several crescent-shaped shadows on the ground [0]. It turns out the light that passes through the holes is a projection of the sun, which is kinda a neat realization. It was pretty unintuitive before I saw this, so I’m impressed by the 17th century astronomers.

0: Similar to https://www.researchgate.net/figure/A-cheese-grater-is-used-...