Why do stars twinkle?
The twinkling of the star is caused by the light passing through the different layers of the earth’s atmosphere.
A star is a huge sphere of plasma. It is characteristically known for its shining light. There are millions and millions of stars in the universe. The closest star to Earth is the Sun. The other stars in the universe are visible to us in the night sky, when the light from our own Sun is not hiding them from view. The stars appear as fixed dots in the sky, mainly because they are so far away from Earth.
While astronauts are in space, they do not actually see stars twinkle. Hence, we can assume that contrary to popular belief, stars do not actually twinkle. They give off a steady source of light, similar to our Sun. The change in their light pattern occurs only when the stars grow through different stages of their life. However, each stage can be billions of earth years long.
However, stars do appear to twinkle from the surface of the Earth. They reason for this is actually the changes in Earth’s atmosphere. Light travels as the speed of over 1 billion km/h. When the light from the stars passes through different layers of the earth’s atmosphere, it gets refracted. Light tends to change directions when it hits a change in density, like a pocket of cold air or hot air. Hence, some of the light reaches our eyes, while some of it gets refracted elsewhere. As we only see part of the light, the times when we do not see the light, the stars appear darker. This causes the phenomenon of the stars twinkling. Think of how a coin at the bottom of a swimming pool seems to wobble from side to side. Or when on a hot day, the shimmering waves that come off a heated road seem to make a distant car appear wavy. It is the same philosophy, essentially.