Question

why do we start twinkle?​

Answer 1

Stars twinkle because of turbulence in the atmosphere of the Earth. As the atmosphere churns, the light from the star is refracted in different directions. This causes the star's image to change slightly in brightness and position, hence "twinkle."

Answer 2

I think the real question is, Why do stars twinkle?

Ans→ Stars are appeared to be twinkling because of the atmospheric refraction. As the light enters our atmosphere it has to go through varying optical densities. So, due to this many refraction  it appears to be twinkling.

Hope it helps.

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