Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Can rotation solve the Hubble Puzzle?

academic.oup.com

Post reply on HN
Print view View original

81–90 of 120 posts

Re: Can rotation solve the Hubble Puzzle?

#81

Post by cryptonector »

philipswood wrote: post #74
jinwoo68 wrote: post #47

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?

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.)

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

They are aptly named.

Re: Can rotation solve the Hubble Puzzle?

#82

Post by gitaarik »

defrost wrote: post #71
eggn00dles wrote: post #68

Earlier quoted context omitted.

the big bang happened everywhere

With the caveat that by some awkward metric 'everywhere' was much smaller when it happened.

Well, that depends whether the universe is infinite. In any case, everything was closer together and hotter.

Re: Can rotation solve the Hubble Puzzle?

#83

Post by bdamm »

cryptonector wrote: post #81
philipswood wrote: post #74

Earlier quoted context omitted.

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.)

Nitpick: atoms really have no subdivisible parts with the same properties as the whole . They are aptly named.

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..

Re: Can rotation solve the Hubble Puzzle?

#85

Post by defrost »

gitaarik wrote: post #82
defrost wrote: post #71

Earlier quoted context omitted.

With the caveat that by some awkward metric 'everywhere' was much smaller when it happened.

Well, that depends whether the universe is infinite. In any case, everything was closer together and hotter.

Infinities come with a spectrum, some are smaller than others . . .

Re: Can rotation solve the Hubble Puzzle?

#86

Post by gitaarik »

nodfyr wrote: post #7
hoseja wrote: post #2

Wait did nobody seriously consider rotation yet? Everything is rotating. Angular momentum is conserved.

That would imply a preferred direction in the universe (the axis of rotation) and thus anisotropy. There are stringent constraints on anisotropy from the cosmic microwave background. In particular, one can use the Doppler effect to check whether the CMB dipole is compatible with our velocity with respect to the CMB frame.

Well, the universe has an axis, found in the CMB:

https://en.m.wikipedia.org/wiki/Axis_of_evil_(cosmology)

Re: Can rotation solve the Hubble Puzzle?

#87

Post by ano-ther »

est31 wrote: post #4

> All objects within our universe rotate, including planets, stars, solar systems, galaxies, and galaxy clusters. Moreover, black holes, spherically symmetric objects with horizons, display near maximal rotation as presented by Daly (2019). The idea that everything revolves [...] naturally extends to the whole universe, as hinted by recent claims of anisotropic Hubble expansion in X-ray observations by Migkas et al.…

If the universe is a black hole, would we be able to see anything falling into it after it crosses the event horizon?

Re: Can rotation solve the Hubble Puzzle?

#88

Post by gitaarik »

jl6 wrote: post #12
AnimalMuppet wrote: post #11

Earlier quoted context omitted.

Are we in an infinite universe? I thought the current thinking was that it was finite but unbounded; that is, that it curved back on itself.

That’s one speculative possibility, but we don’t know. It could be infinite, or finite with a boundary just out of sight (beyond the edge of the observable universe), or some other more exotic geometry. There’s no solid evidence either way. My money’s on non-infinite, just because I’m not sure infinity is a well-defined concept outside of mathematics. We’ve certainly never observed any other infinite phenomena.

I always like to think that finity can only exist in a context of infinity. So even if the "universe" is finite, it exists in a context of infinity.

Because they're opposites, they depend on each other's existence. Like hot cannot exist without cold, or light doesn't have any meaning if there is no darkness.

Re: Can rotation solve the Hubble Puzzle?

#89

Post by gitaarik »

exe34 wrote: post #9
lumost wrote: post #8

Earlier quoted context omitted.

Rotation implies a great many observables and properties of the universe. There would be a cosmic axis, which implies a cosmic center and a cosmic north. Both concepts that are problematic in an infinite universe. If the universe is in fact inside of a black hole of a different universe - some of these problems go away as the Hubble volume would be the finite boundary of the universe.

and we would be at the center?

Yeah, we are.

https://en.m.wikipedia.org/wiki/Axis_of_evil_(cosmology)

Post reply on HN