Question

Why do stars appear to be twinkling?

Answer 1

Twinkling of stars due to atmospheric refraction:

1. Refraction is caused when light travels from one medium to the other.
2. Our earth is covered with the atmosphere having different layers with different optical densities.
3. The warmer layer of the atmosphere behaves like an optically rarer medium whereas the cooler layer behaves like an optically denser medium.
4. Since the temperature in the different layers of the atmosphere is not stable, the density changes, and the observer will receive the light coming from the star at different angles causing the twinkling effect.