Question
Explain why the planets do not twinkle.

Answer

  • Planets are much closer to the earth relative to stars.
  • Therefore, planets appear bigger than stars.
  • Stars are far away from the earth.
  • Therefore they appear smaller.
  • So, stars can be considered as point-sized sources and planets can be considered as a collection of a large number of point-sized sources of light, i.e., extended sources of light.
  • As planet is a collection of a large number of point-sized sources of light, the total variation in amount of light entering our eye from all the individual point-sized sources averages out to zero, thereby nullifying the twinkling effect.
  • That is why planets do not twinkle.

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