Stars twinkle because their light passes through Earth's atmosphere, which has layers of air with varying densities and temperatures. This causes the starlight to bend (refract) multiple times in different directions as the atmosphere moves and changes. As a result, the apparent position and brightness of the star fluctuate, making the star appear to twinkle. In simpler terms, as light from a star enters the Earth's atmosphere, it is continuously bent due to the changing air layers, causing the star's light to flicker in intensity and position when viewed from the Earth's surface. This effect is called atmospheric refraction and is responsible for the twinkling of stars. Planets generally do not twinkle because they are closer and appear as tiny disks, so the bending effects average out and their light remains steady.
