Short answer: Refraction! When starlight passes through Earth's atmosphere, layers of air at different temperatures refract the starlight, bending its path. The amount of bending is constantly changing with the wind, so the starlight forms a very faint dancing pattern on the ground, like the mottled light on the bottom of a swimming pool. As you look up through those bright and dark spots, the amount of starlight reaching your eyes changes, and you'll see the star twinkle. Long answer: You might [...]