Most compact objects in space rotate. This is because they formed from
the accretion of other objects moving in various directions. It would
be very unlikely for these objects to have a net angular momentum of
zero and, since angular momentum cannot be destroyed, the compact
object must have the same angular momentum as the sum of the original
objects. The smaller the size of the compact object, the faster it has
to spin for a given angular momentum. the extreme example of this is a
neutron star, which is so small that can rotate at very high angular
velocity. Imagine an object as heavy as the sun, spinning as fast as
60 times per second!
Of course West and East are just the names we use to describe the
direction in which a point on the surface of the earth is rotating, so
I suppose your question is why the axis points in the direction it
does (which we call North). The axis of rotation of the earth and most
of the planets is in roughly the same direction as the axis of the
orbit of the earth and other planets around the sun. This is because
the solar system formed by coalescence of particles orbiting around
the sun in a disk. The reason for the formation of a disk is
complicated, but can be reproduced in computer simulations. The
rotational and orbital momentum of most of the planets including the
earth point generally in the same direction as the angular momentum of
this primordial disk. |
