[hecuter (OP)]

I was doing a little boning-up on the Theory of Relativity and it discussed how large objects cause distortions in the fabric of space-time, which in turn causes gravity and explains space orbits.  However, what drives the rotation of galaxies, say for example a spiral galaxy?  Is it residual motion left over from the Big Bang?  Or is it being affected by some other force?

[lightarrow]

I was doing a little boning-up on the Theory of Relativity and it discussed how large objects cause distortions in the fabric of space-time, which in turn causes gravity and explains space orbits.  However, what drives the rotation of galaxies, say for example a spiral galaxy?  Is it residual motion left over from the Big Bang?  Or is it being affected by some other force?

One reason is the collision with other galaxies.

[Soul Surfer]

The rotation of galaxies, stars, planets and asteroids comes from the general turbulence of the  gases that form them amplified greatly by the law of conservation of angular momentum as they contract to become more dense.

[daveshorts]

It is thought to be just tiny amounts of turbulence in the early universe which is magnified as the gas collapsed to form galaxies by the conservation of angular momentum.

If this is the case galaxy rotations should be random and there is some recent research as part of the Galaxy Zoo project
http://www.galaxyzoo.org/
Where they have been getting the public to classify galaxies

The results seem to show that there is a correlation in the direction
locally but over large scales it is random
http://uk.arxiv.org/abs/0809.0717

[Vern]

The results seem to show that there is a correlation in the direction
locally but over large scales it is random

This seems reasonable and in tune with the previous posts. As accretion disks form from random nucleons and electrons in space, huge local areas should have some interaction as they form.

[Fluid_thinker]

do they all rotate in the same direction?

[lyner]

In all directions, as a whole.

The best way to explain how they end up rotating is to think of how they are formed. Lots of small particles being attracted to each other are going to converge in the general direction of their mutual centre of mass. If they had been completely frozen / stationary when they were 'let go', then I imagine they would, in fact, all converge into a single point. This would be a very special case, indeed. But they are moving around. That means that they have a net, non zero, angular momentum about the CM. The rotation will increase as the radius decreases (a la skater doing a pirouette) so, by the time they become galaxies and the stars become stars etc, there will be a general swirliness - mostly in the same sense, locally. Hence, the Earth spins and the Moon orbits the Earth and the Earth orbits the Sun and the other planets too, all in the same sense and near the same plane. EXCEPT for a few exceptions, like Uranus, which has a tilt of about 90degrees.

Didja know that, although there is only about 1% of the mass of the Solar System as planets, if that 1% 'fell' into the Sun, the resulting increase in rotation of the Sun would fling it all out again. It's because the angular momentum depends upon the square of the radius of rotation; Jupiter, for instance, has a lot of angular momentum c/w the Sun.