Expert: Philip Stahl - 2/19/2010

Question
Why do most, if not all, spacial objects like planets, moons,  stars, suns, galaxies -- even meteors -- spin around their respective axes?

Answer
Hello,

Well, I don't know that meteorites spin around any axes in any uniform way, but that's a topic for another discussion.

Anyway, given that all the bodies you referenced formed from highly energetic processes - and most often under the collapse of dust and gas clouds of different size, this isn't surprising.  For example, let there be some original giant cloud of rotating gas (proto-star)of mass M and let it spin off wedges and globs of material (of masses: m1, m2, m3....m9) at differing distances. It will then lose angular (rotational) momentum in the process - while the detached "globs" acquire it.

This is in fact what happened to the proto-Sun which used to spin on its axis much faster than it does now. That "lost" angular momentum  (or lost rotational kinetic energy, if you prefer)went into providing the differing rotational energies of the assorted planets. Hence, their spins.

The same process likely applies for Moons, as well as galaxies - though obviously in different scales. (A proto-galactic cloud, leading to a cluster of bound galaxies (e.g. Local Group), probably has 10^12 times more mass than a proto-solar nebular cloud).

The main point is that we always expect transfer of some early modes of energy, like kinetic and heat, to other modes, like rotational kinetic and light (especially as the gravitational force binding the material leads to nuclear fusion, say in stars).

Hope this sheds some light!