Question

Why do stars appear twinkling?

Answer 1

Stars appear to twinkle because the Earth’s atmosphere consists of several layers with varying densities, resulting in different refractive indices. The air is also in constant motion due to convection currents caused by factors like wind and temperature changes. As light rays from a star pass through the atmosphere, they continuously change direction due to these shifting refractive indices. This causes the number of light rays reaching an observer’s eye on Earth to vary constantly, making the star seem as if it is twinkling. In contrast, stars viewed from a spacecraft above the atmosphere do not twinkle because their light does not pass through these turbulent atmospheric layers. Additionally, the moon appears to shine steadily as it subtends a larger angle and sends more light rays, so small changes in atmospheric conditions do not significantly impact the total light entering the eye.