Take the tour ×  This question already has an answer here:  I
understand the governing force causing the earth's cycle around
the sun is gravity. It can be described by Keplar's law. But
what causes the earth's spin? what is its governing law?
share|improve this question Noone knows for sure.
universetoday.com/14491/why-does-the-earth-rotate –  user6972
Aug 28 at 3:17 Possible duplicates:
physics.stackexchange.com/q/12140/2451 and links therein. – 
Qmechanic Aug 28 at 7:06 add comment  marked as duplicate by
Qmechanic Aug 28 at 8:05   1 Answer  The short answer is, the
law of angular momentum.  It's not just the earth that spins.
All planets tend to spin.  In fact, if you think about it, there
is a rotation of galaxies that form out of huge disks of matter.
A solar system forms in a similar fashion, and exhibits a
rotation around the center of mass (the sun, which is also
rotating). Planets form in a similar fashion, and exhibit a
rotation around their own center of mass (their axis) with moons
rotating arou