[lightarrow]

If you have a rotating universe in any meaningful sense of the word rotation, you have an axis hence anisotropy. In an "empty" universe you can postulate that you would not feel any forces when rotating because you are not rotating with respect to anything and angular momentum would not have any magnitude. So how would this apply to a rotating universe? For argument's sake, assuming a closed universe (which may not be the case), would it not be also difficult to say with what the universe is rotating with respect to?

I agree, it's exactly what I claimed: inertial forces exist within a universe, that is when we are in a ref frame which rotates with respect to the other masses of the universe; but the universe as a whole doesn't rotate with respect to anything, so for the same reason no inertial forces, no anysotropy should appear, in my opinion.

[Tiapan]

If you have a rotating universe in any meaningful sense of the word rotation, you have an axis hence anisotropy. In an "empty" universe you can postulate that you would not feel any forces when rotating because you are not rotating with respect to anything and angular momentum would not have any magnitude. So how would this apply to a rotating universe? For argument's sake, assuming a closed universe (which may not be the case), would it not be also difficult to say with what the universe is rotating with respect to?

I agree, it's exactly what I claimed: inertial forces exist within a universe, that is when we are in a ref frame which rotates with respect to the other masses of the universe; but the universe as a whole doesn't rotate with respect to anything, so for the same reason no inertial forces, no anysotropy should appear, in my opinion.

Define Universe.
That which is all, so "nothing" exists beyond the universe?
What is nothing?

It presumes things we can never know. Lets ignore this homo-centric remnant from religious point of view for a moment and consider an alternative definition.

A universe is that which originates from a "Big Bang" Phenomena.

Why is it not possible to have sister universes formed from other concurrent big bangs?

What is the key proof that Quasars are actually part of our universe. Could they be distant sister universes scattered elsewhere throughout the void we call "nothing"?

Consider a volume of space. If it contains matter, then we consider it as real. If we remove matter we consider it as "empty" and therefore a "vacuum". Matter and Energy are linked by the E=mc^2 equivalence, so is a volume of space truly empty if at any particular time a photon is traversing that volume? Then we have the case of a volume beyond the "universe" which has no matter and because light has not yet reached it, so it is truly empty. Does this mean it is nothing and therefore does not exist. Is this a "True" vacuum?

The Machian concept suggests that even though we have no frame of external reference we will still certainly observe the experience of rotational effects. Consider a space ship way out in deep space with two balanced tangential rockets attached, when fired the spacecraft will spin exhibiting centrifugal force and Coriolis effects if spherical, whether or not we have an external reference or not.

Next many rather dogmatically state the universe is not rotating, indeed the current experimental evidence suggest it is zero, or is it in fact just very small. One investigation gave a value of 10^-13 rad/sec.

Given conservation of angular momentum, if we go back in time the "universe" would have had a smaller radius and a proportionally increased angular velocity. V2/V1=R1/R2

1 year after Big Bang the radius of the universe was 1 light year. Using the observed figure above would mean the universe was rotating at around 0.5 m/sec, still tiny in the scheme of things. Now lets look at the angular velocity around 1/20th of a second after the expansion event. The radius will be 1/20th of a light-second, while the radial velocity at the equator (if that is a correct model) would equal the speed of light.

Since matter cannot exceed this limit what does that say about the minimum size of the universe?

If the observed estimate is correct how could the universe ever have been smaller than aprox. 36,000km in diameter?

How did it get this angular momentum. Is it possible this is evidence of the conservation of angular momentum from a previously collapsed universe? Is it physical evidence of a property that existed before the Big Bang, a concept many accept as impossible. But is it?

It is good scientific principle to be skeptical of all things and challenge the underlying assumptions and axioms if the observed evidence is not matched by theory. Food for thought.

Cheers

[yor_on]

To me it seems to be about expending energy relative something else? Both accelerating and spinning are expressions of getting 'work done' transforming that possible 'work' into something unable to transform again, without injecting 'outside' energy into it.

And as far as i understand both will have the same effect time dilation wise as well as momentum/relative mass depending on speed/velocity/angular momentum? If one look at it from the principle of equivalence I find it hard though to find a similar description from what I observe. But then again, that equivalence principle seems to me only to be true under a very limited circumstance, that is an uniform acceleration at a constant velocity, at f.ex one G?

[Murchie85]

comment to

I think if there were a rotation it would define a special point in the universe about which rotation occurred. None has ben found and is not in any models as far as I know. Also the universe would have an "up" and a "down" along any rotational axis so would no longer be isotropic. This would not fit in with observation but it is possible it is sufficiently small that it is unnoticable. The concept of an overall net rotation would mean that there was a very large angular momentum just after the Big Bang and I suppose an infinite one at some point. I don't think any models have this and it maybe not even a practical supposition, I'm not sure. Certainly the models that already exist are complicated enough without one that introduces artifacts to cope with a possible feature that has never been observed.

Yes definitely, but although the models are complicated enough, if an overall net rotation really did/does exist then it would be essential to add into the current models, it may even help simplify them. Also it would't be completely against intuition as orbits are repeated as scale increases generally eg planets orbiting local stars, stars orbiting in binaries, star clusters orbiting super black holes in the centre of their respective galaxy. Its still not certain of a uniform distribution of stars, therefore if there was a huge clump in the middle then I would argue net rotation (tiny tho it may be) could be a possibility.