[jinwoo68]

Universe is called universe because it is the only one. Everything that exists should be part of the universe. When we say the universe rotates, what does it mean? Rotate relative to what? Does it mean that there's a larger "universe" that contains ours?

[olddustytrail]

Rotation isn't relative. You can tell how quickly you're rotating without reference to any other objects.

[carra]

But even then you can only tell that you are rotating relative to space itself. If I understand correctly here we are speaking about the space itself rotating, so that would not be possible unless something else contains our universe's space, right?

[olddustytrail]

Nope, rotation is not relative because it's an acceleration.

There is no "space itself" because then you're assuming it is relative, like the speed of light. Basically you're trying to rediscover the aether.

That was the question: light moves at speed C, but relative to what?

[philipswood]

Nitpick: "Atoms are called atoms because they have no subdivisible parts".

Oops, it turns out we used the name too soon.

When people say "universe" these days they mean the "visible universe" (or maybe the visible universe plus the stuff we're sure is there, but that falls outside our light cone now) - and not the original definition of the word anymore.

(Not that we have "found" anything else yet.)

[cryptonector]

Nitpick: atoms really have no subdivisible parts with the same properties as the whole.

They are aptly named.

[bdamm]

Atoms having no subdivisible parts implies that there are parts at all. But it turns out all matter is just somewhat stable oscillations within an energy field and no real boundaries between one part and another, and certainly nothing resembling such at the scale of something as large as an atom. So again.. too early..

[cryptonector]

Good point.

[layer8]

“Universe” is often used in the sense of “observable universe”.

[jinwoo68]

I don't think the paper claims that it's the observable universe that rotates. Does it? It'd be awkward if only the observable universe rotates. Observable universe is not special. It's observable just because it is "close" to the Earth.