It’s due to how light from a vacuum refracts when it enters earths atmosphere
The light photons from the star bounce around in the earth atmosphere because you have different temperature pockets all over the atmosphere at different altitudes .
The light bounces around these different density pockets and gives the illusion of the twinkle
The light photons from the star bounce around in the earth atmosphere because you have different temperature pockets all over the atmosphere at different altitudes .
The light bounces around these different density pockets and gives the illusion of the twinkle