Here's how it works:
* Light bends: When light travels from one medium to another (like from space to the Earth's atmosphere), it changes direction. This bending of light is called refraction.
* Density gradient: The Earth's atmosphere is not uniform in density. It gets denser as you go lower. This creates a density gradient.
* Light bends downwards: As light from a star enters the atmosphere, it passes through layers of increasing density. Each time it passes from a less dense layer to a denser layer, it bends slightly downwards.
* Apparent position higher: This bending of light makes the star appear higher in the sky than it actually is. The effect is more pronounced near the horizon, as the light has to travel through a greater thickness of atmosphere.
In summary: Atmospheric refraction makes stars appear higher in the sky than their true position, especially near the horizon. This phenomenon is responsible for the twinkling of stars, as the bending of light is constantly changing due to fluctuations in air density.
