* Air is constantly moving: Our atmosphere is a turbulent mix of gases, with pockets of warm and cold air swirling around.
* Light bends: As starlight travels through these varying densities of air, it gets bent or refracted. Think of how a straw looks bent in a glass of water – the same principle applies.
* Rapid changes: These changes in air density happen very quickly, causing the light from the star to bend and shift in direction constantly. This rapid shifting of light is what we perceive as flickering.
So, why don't planets flicker? Planets are much closer to us than stars, so their light travels through less atmosphere. The amount of refraction is smaller, and the changes are less noticeable, making them appear steady.
Fun fact: The amount of flickering a star does can be an indicator of how stable the atmosphere is at that moment. Astronomers actually use this "seeing" to determine how clear the night sky is for observations!
