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This question already has an answer here:

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

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marked as duplicate by Waffle's Crazy Peanut, Dan, dmckee Jul 6 '13 at 15:39

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Possible duplicates:, and the links therein... – Waffle's Crazy Peanut Jul 6 '13 at 5:49
@Crazy Buddy: Those questions look like duplicates of each other. – Dan Jul 6 '13 at 7:34
up vote 2 down vote accepted

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.

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