Re: How does isotropic connect to zero angular momentum for the universe?

Hello Dick,

I think one of the previous answers you're referring to is this one, written by me long ago.

What I was trying to say in that answer had to do with whether the universe itself (not necessarily the microwave background radiation) was isotropic. The idea is that if the universe had a net angular momentum (or spin) it would not be not isotropic -- the same in every direction -- because the spin axis would be a "special" direction. Since current cosmological theory assumes the universe to be isotropic, this might mean that some of its predictions are wrong.

Ok, what does this have to do with the cosmic microwave background? As you may know, this radiation is extremely isotropic, and there is certainly no hint of a spinning universe in it. Frankly, I don't know for sure whether a spinning universe would imprint a signal on the observed microwave background, but I suspect that it would, since other motions (like that of the Sun through the galaxy) do have such an effect. So either: the universe has no spin (because we don't see it in the microwave background), or any spin has no effect on the microwave background. I think the former is more likely correct.

Pauline