Question

Explain why the planets do not twinkle.

Answer 1

Hint: Twinkling of stars is a common phenomenon observed by us in everyday life which is a result of refraction. Stars are very far away as compared to the planets so they appear smaller than the planets. Ray of light from the stars which is considered as a point source due to its distance gets refracted by different layers of the atmosphere which causes the twinkling.

Complete answer:
Refraction is the phenomenon due to which a ray of light bends from its original path when travelling from one medium to the other. When the ray of light travels from a rarer to denser medium it bends toward the normal and when it travels from denser to rarer medium it bends away from the normal.
Stars are very far away from us so they appear as a point source of light. Due to refraction of the light it appears to change its position very rapidly which can be observed as the twinkling of the stars.

In case of planets, their distance from us is smaller when compared to the stars which makes them appear bigger. So, the light rays here appear to come from multiple point sources or a cluster of point sources of light which causes the dimming effect due to some point sources being nullified by the brightening effect of the other points sources. Also, the angle subtended by the planets at the human eye is more as compared to the stars so the shift in their position is smaller when compared to the stars. As the shift is small, they do not twinkle.

Note:
When we see the word twinkling, the first thing that comes to mind is the stars and we don’t read the question. So, it's better to read the full question first. When it comes to the planets is the major reason which prevents it from twinkling or we may say the same thing in terms of angle subtended by them at the human eyes.