What causes the stars to twinkle?

Concept: The atmosphere is a heterogeneous mixture of various particles, it does not have a constant refractive index. Refraction occurs when a substance's refractive index changes. As a result, atmospheric refraction occurs in a medium with a changing refractive index.

Because of the effects of the Earth's atmosphere, the stars appear to twinkle in the night sky. When starlight enters the atmosphere, it is influenced by winds and areas with varying temperatures and densities. When viewed from the ground, this causes the star's light to twinkle. As light from a star travels through our atmosphere, it bounces and bumps through the various layers, bending the light before it reaches you. Because the hot and cold layers of air continue to move, the bending of the light changes, causing the star's appearance to wobble or twinkle.