Why Do Stars Twinkle?

You must have seen stars twinkling in the sky. Starlight comes to us from very far away. Its journey from the upper reaches of the sky to the earth is full of strange twists and turns.

The twinkling of the stars is nothing but an optical illusion or something that looks real, but isn't.

You must have seen a road dissolve into water on a hot summer day. This is another example of an optical illusion.
This happens due to the light's journey. Most of the time, light travels in a straight line, but when it passes through layers of hot and cold air, it bends and deflects.

So when we see the stars twinkling, it is actually the starlight bending as it passes through the earth's atmosphere.

Credit: Children's Questions and Answer Book