It can't rotate on another solar axis, it only can use it's own.

I'm not sure what you are asking. Do you mean instead of some other axis, or why does it rotate at all?

To put it simply, it's a result of angular momentum. If you really want to read in detail about it, check this out: http://curious.astro.cornell.edu/question.php?number=416

1) The fundamental laws of solid mechanics say that if you can ignore the external forces acting on a solid, its movement can be decomposed as follows: - a translation along a straight line, with a constant velocity - a rotation around a straight line going through its center of gravity, with a constant angular velocity This line is called the rotation axis and its direction does not change. In the case of earth inside the solar system, there is also the effect of the gravitation force from the sun. But this mainly causes earth not travelling on a straight line, but on an orbit around the sun. It does not influence the rotation very much (or just very slowly) 2) Newton's Second Law: "The net force on a particle is, thus, equal to rate change of momentum of the particle with time." "Classical mechanics also includes descriptions of the complex motions of extended non-pointlike objects. The concepts of angular momentum rely on the same calculus used to describe one-dimensional motion." Source: http://en.wikipedia.org/wiki/Newtonian_mechanics#Forces.3B_Newton.27s_Second_Law Further information: http://en.wikipedia.org/wiki/Angular_momentum (The conservation of the angular momentum explains the rotation) 3) as the earth has been having the same movements, one of them being rotating on this particular axis for quite a long time, particular effects have been developping: - orientation of the magnetic field close to the rotation's axis - rotation of not solid parts of the earth such as those in the core - temperature gradient between the poles and the equator zone and seasons - distortion of the earth into an oblate spheroid (Equatorial bulge) "Equatorial bulge: bulge which a planet may have around its equator, distorting it into an oblate spheroid": http://en.wikipedia.org/wiki/Equatorial_bulge 4) some external influences and some internal influences (due to the fact that the earth is not really a solid body) could cause these ideal movements to be modified with time. For instance, earth rotation could reduce its speed very slowly. 5) some further references: http://en.wikipedia.org/wiki/Rotation http://en.wikipedia.org/wiki/Earth_rotation http://www.windows.ucar.edu/tour/link=/the_universe/uts/earth2.html http://encyclopedia.farlex.com/rotation+(physics) "What force makes the earth rotate on its own axis? Could its rotation ever slow down?": http://www.guardian.co.uk/notesandqueries/query/0,,-186829,00.html http://en.wikipedia.org/wiki/Mechanics

Earth has magnetic field with North and South Poles. The axis of rotation of earth is different from the magnetic poles and is tilted. This causes force for earth to rotate on its Axis. Moon doesn't have magnetic field and therefore doesnt't rotate on its axis. I feel the same principle applies to all planets in our Solar System.

Earth rotates because of leftover momentum from the solar nebula that all of the planets and the Sun formed within.

Earth, my friend, is way too drunk to stay still. Unfortunately Mr. Sun can't help because he's on fire. The other planets are too lazy...

I'm not jewish.. but it seems God liked the idea of a colorful blue dradle. :)