Question
Thu April 15, 2010 By: Anirudh Sudhir

when anything moves air replaces it so how can planets move in vacume

Expert Reply
Thu April 15, 2010

The "air" is just around the planet earth, upto few km thick. As we go up the pressure decreases, and after that there is no air. There is vast amount of space where there is no air.

Air molecules are held in this layer because their RMS velocity is less than escape velocity from earth.

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