Why planets and stars rotate about their own axis?




Why do stars and planet revolve around their own axis?
What gives them the force to do so?
Will they ever stop rotating?

Well... we know after the big bang matter was created.
It was in the form of huge gas clouds. The cloud contained gas molecules. The cloud was very massive. Billions and billions of solar masses.
These clouds contained gas molecules. Due to gravity these clouds certainly had some rotational movement about their centre. This rotational motion was Slow. Very slow as it was due to motion of gas molecules.

It is believed that planets and stars were made from these gas clouds. At a certain stage they become so massive and unstable that they collapse.

Owing to the law of conservation of angular momentum that states that angular momentum is conserved in case of absence of external forces.

The angular momentum of this massive cloud was transferred to stars and planets made from it. Since the stars and planets were less massive they gained more rotational speed (search law of conservation of angular momentum on Wikipedia if you are confused here).

As a result the planets and stars started rotating.

However the current rotation of planets- their rotational speed and tilt of axis of rotation is a result of several events in the history.

Why planets continue rotating whereas a rotating pen will stop rotating. What gives energy to these planets?
Well the explanation is simple.

The space is empty region with no air hence no air drag or friction. Hence they need no energy to continue rotating.

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