# Why do cosmic bodies revolve? [duplicate]

Why do cosmic bodies such as planets, stars, satellites revolve?
What made them to revolve after the formation of universe?

## 1 Answer

The short answer is: angular momentum conservation. Angular momentum equates to the product of moment of inertia times angular (rotational) velocity. When a gas or dust cloud contracts under the influence of gravity and forms a more compact cosmic body, any nonzero total angular velocity will increase due to the moment of inertia decreasing.