Why do the stars twinkle at night ?

It's the atmospheric refraction due to which the starlight gets bent towards
the normal when it passes through the dense atmosphere. Since the density of the atmosphere is not the same everywhere so the extent of refraction keeps on changing. Stars being far away from the earth look like point sized objects and as the path of light coming from them keeps on changing so their apparent position also keeps on fluctuating due to which the stars sometimes appear brighter and at times fainter. This phenomenon makes the stars look like they are twinkling.


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