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Re:Universe's expansion 'is now slowing, not speeding up' by jimbo808 on Thursday November 06, 2025 @04:40PM (#45840785)
Anyone know how credible this is? If true, then that means the big bounce is back on the menu, and the universe could actually be an infinitely oscillating system.
Re:Universe's expansion 'is now slowing, not speeding up' by jampekka on Thursday November 06, 2025 @04:44PM (#45840836)
At least The Guardian has a comment from an independent expert:

"Prof Carlos Frenk, a cosmologist at the University of Durham, who was not involved in the latest work, said the findings were worthy of attention. “It’s definitely interesting. It’s very provocative. It may well be wrong,” he said. “It’s not something that you can dismiss. They’ve put out a paper with tantalising results with very profound conclusions.”"

https://www.theguardian.com/science/2025/nov/06/universe-exp...

Re:Universe's expansion 'is now slowing, not speeding up' by HeinzStuckeIt on Thursday November 06, 2025 @04:47PM (#45840876)
As an academic, that is exactly what the kind of noncommittal, don’t burn your bridges with colleagues and funding bodies thing that I would say about even clearly flawed research if I were put on the spot by a popular-press publication. In fact, if you know you can rebut flawed research in time, you might want to assist in hyping it first so that your rebuttal will then make a bigger splash and benefit your personal brand.
Re:Universe's expansion 'is now slowing, not speeding up' by ImPostingOnHN on Thursday November 06, 2025 @06:19PM (#45841752)
It's also something you could say if you forgot to read the assignment and the professor called on you.
Re:Universe's expansion 'is now slowing, not speeding up' by piker on Friday November 07, 2025 @04:29AM (#45844842)
"It makes some profound points, yes. What if? BUT what if not?"
Re:Universe's expansion 'is now slowing, not speeding up' by mr_mitm on Friday November 07, 2025 @04:44AM (#45844913)
I read it as "I recognize some of the names and the abstract doesn't sound like complete nonsense".
Re:Universe's expansion 'is now slowing, not speeding up' by p00dles on Friday November 07, 2025 @07:10AM (#45845614)
That guy should start a PR firm
Re:Universe's expansion 'is now slowing, not speeding up' by jameslk on Friday November 07, 2025 @01:45PM (#45849525)
This sounds like something George Costanza would say
Re:Universe's expansion 'is now slowing, not speeding up' by pdonis on Thursday November 06, 2025 @05:18PM (#45841196)
> If true, then that means the big bounce is back on the menu

I don't think so. Deceleration does not imply recollapse. AFAIK none of this changes the basic fact that there isn't enough matter in the universe to cause it to recollapse. The expansion will just decelerate forever, never quite stopping.

Re:Universe's expansion 'is now slowing, not speeding up' by Erem on Thursday November 06, 2025 @07:24PM (#45842275)
Wait but decelerating forever does in fact imply recollapse doesn't it?
Re:Universe's expansion 'is now slowing, not speeding up' by pdonis on Thursday November 06, 2025 @08:02PM (#45842508)
No. The simplest example is a matter-dominated universe at exactly the critical density. It decelerates forever but never quite stops expanding--the expansion rate asymptotes to zero.
Re:Universe's expansion 'is now slowing, not speeding up' by deepthaw on Thursday November 06, 2025 @07:28PM (#45842295)
I assume decelerating forever means asymptotically approaching not collapsing.
Re:Universe's expansion 'is now slowing, not speeding up' by cwillu on Thursday November 06, 2025 @08:44PM (#45842713)
An object on an escape trajectory from another mass is forever decelerating, but it still escapes.
Re:Universe's expansion 'is now slowing, not speeding up' by jimbo808 on Thursday November 06, 2025 @09:09PM (#45842840)
Would it not enter the viscinity of other objects which would eventually coalesce into local centers of mass (maybe like one per observable universe diameter or something)?
Re:Universe's expansion 'is now slowing, not speeding up' by ridgeguy on Friday November 07, 2025 @01:04AM (#45843909)
Nope, cosmic Zeno's Paradox. Collapse never quite happens.
Re:Universe's expansion 'is now slowing, not speeding up' by xerox13ster on Friday November 07, 2025 @04:09AM (#45844753)
Nope, that would be velocity changing sign, which means acceleration would increase.
Re:Universe's expansion 'is now slowing, not speeding up' by SideburnsOfDoom on Friday November 07, 2025 @04:25AM (#45844814)
No, in much the same way that a speeding vehicle slowly decelerating towards a stop doesn't mean that it will return to where it started the journey.

Actually it's worse than that, "decelerating forever" doesn't even mean that it ever even comes entirely to a stop. let alone return to where it started.

Re:Universe's expansion 'is now slowing, not speeding up' by khimaros on Thursday November 06, 2025 @05:07PM (#45841073)
time to re-read "The Last Question"
Re:Universe's expansion 'is now slowing, not speeding up' by Cantinflas on Thursday November 06, 2025 @05:17PM (#45841177)
Asimov was so good. Amazing story
Re:Universe's expansion 'is now slowing, not speeding up' by CamperBob2 on Thursday November 06, 2025 @05:30PM (#45841308)
"Sorry, but as a large language model, I cannot provide advice on how to reverse entropy."
Re:Universe's expansion 'is now slowing, not speeding up' by cluckindan on Thursday November 06, 2025 @06:27PM (#45841809)
Thinking…

Thinking…

Thinking…

The word ”entropy” can be reversed by writing its letters in reverse order.

E-N-T-R-O-P-Y

The first letter is E.

The second letter is N.

The third letter is T.

The fourth letter is R.

The fifth letter is O.

The sixth letter is P.

The seventh letter is Y.

Thinking…

To construct the reversed word, the seventh letter must be first, and the sixth letter must be second, and the fifth letter must be third, and the fourth letter must be fourth, and the third letter must be fifth, and the second letter must be sixth, and the first letter must be seventh.

The seventh letter is Y, so the first letter in the reversed word is Y.

The sixth letter is P, so the second letter in the reversed word is P.

The fifth letter is O, so the third letter in the reversed word is O.

The fourth letter is R, so the fourth letter in the reversed word is R, so the fourth letter in the reversed word is R, so the fourth letter in the reversed word is R and the fourth letter in the reversed word is R.

The third letter is T, so the fifth letter in the reversed word is O.

The second letter is N, so the sixth letter in the reversed word is N.

The first letter is E, so the seventh letter in the reversed word is N.

To put it all together:

Y-P-O-R-R-R-T-N-E-Y

The word ”entropy” can be reversed by writing its letters in reverse order: ”yporrrtney”.

Re:Universe's expansion 'is now slowing, not speeding up' by mindcrime on Thursday November 06, 2025 @08:03PM (#45842510)
yporrrtney

Looks like it halluco-commingled the physical principle and the drummer from Dream Theater...

Re:Universe's expansion 'is now slowing, not speeding up' by dTal on Thursday November 06, 2025 @07:43PM (#45842382)
This is art.
Re:Universe's expansion 'is now slowing, not speeding up' by littke on Thursday November 06, 2025 @07:31PM (#45842309)
Masterpiece!!
Re:Universe's expansion 'is now slowing, not speeding up' by patcon on Thursday November 06, 2025 @08:21PM (#45842612)
I love this. I've upvoted every parent just so you can get your dues :)
Re:Universe's expansion 'is now slowing, not speeding up' by AutoDunkGPT on Friday November 07, 2025 @12:43AM (#45843820)
bravo, sir
Re:Universe's expansion 'is now slowing, not speeding up' by pdonis on Thursday November 06, 2025 @05:20PM (#45841212)
> Anyone know how credible this is?

AFAIK the previous models that all assumed that Type 1a supernovae were not affected by the age of the progenitor stars had no actual analysis to back that up; it was just the simplest assumption. This research is now actually doing the analysis.

Re:Universe's expansion 'is now slowing, not speeding up' by antonvs on Thursday November 06, 2025 @08:40PM (#45842698)
> AFAIK the previous models that all assumed that Type 1a supernovae were not affected by the age of the progenitor stars had no actual analysis to back that up; it was just the simplest assumption.

Why would you assume this? It's not correct.

Type 1a supernovae aren't even assumed to be "standard candles" as is often claimed: rather, they're standardizable, i.e. with cross-checks and statistical analysis, they can be used as an important part of a cosmological distance ladder.

A great deal of analysis has gone into the development of that distance ladder, with cross-checks being used wherever it's possible to use them.

They look at surface brightness fluctuations in the same galaxies, Tully-Fisher distances[1], tip of the red giant branch distances[2], and even baryon acoustic oscillations[3]

Is it possible that this one single paper has upended all that? Theoretically. Is it likely? No.

[1] https://en.wikipedia.org/wiki/Tully%E2%80%93Fisher_relation

[2] https://en.wikipedia.org/wiki/Tip_of_the_red-giant_branch

[3] https://en.wikipedia.org/wiki/Baryon_acoustic_oscillations

Re:Universe's expansion 'is now slowing, not speeding up' by pdonis on Thursday November 06, 2025 @08:52PM (#45842752)
> Why would you assume this? It's not correct.

None of your references contradict it, as far as I can see. I'm well aware that Type 1a supernovae are only part of the overall picture, but that observation doesn't contradict what I said.

Re:Universe's expansion 'is now slowing, not speeding up' by DarmokJalad1701 on Thursday November 06, 2025 @06:18PM (#45841747)
RETVRN to mx'' + cx' + kx = 0
Re:Universe's expansion 'is now slowing, not speeding up' by observationist on Thursday November 06, 2025 @04:52PM (#45840918)
The more we learn, the less we end up knowing about how "everything" works - some things are mathematical in nature and demonstrate absolutes, but frameworks shift, and complexify, and exceptions to things we thought absolutes have occurred throughout history.

For claims about how the universe works at scales and timeframes so utterly beyond anything testable, it's a little difficult to say this is credible at all - not dunking on the researchers, but in order to validate their conclusions, there's a whole chain of dependencies and assumptions you'd have to follow along with, and each of those things will be its own complex birds nest tangle of assertions, and I don't see how you can really say one way or another until you have a lot more information and a lot better Theory of Everything than we've got right now.

For what it's worth, for all the impact it'll have on anyone's life outside of academia, I'd say they're 100% correct and people should buy them free beers at their local pubs for at least the next year in return for explaining their ideas at length.

Re:Universe's expansion 'is now slowing, not speeding up' by ls612 on Thursday November 06, 2025 @08:56PM (#45842773)
I’m gonna wait for Scott Manley to discuss it before I form much of an opinion.
Re:Universe's expansion 'is now slowing, not speeding up' by jumploops on Friday November 07, 2025 @01:40AM (#45844075)
“We can’t observe the whole universe, so cosmology is not really about the universe. It’s about the observable patch and the assumptions we make about the rest.”

(paraphrasing George Ellis)

We’re in a bounding sphere, with a radius that’s roughly 46.5 billion lightyears, so any observation we make may be true for our local observable range, but there’s no (known) way to know what’s beyond that sphere.

Re:Universe's expansion 'is now slowing, not speeding up' by alfiedotwtf on Friday November 07, 2025 @03:16AM (#45844501)
This is the thing that blows my mind the most with physics and cosmology
Re:Universe's expansion 'is now slowing, not speeding up' by wtcactus on Friday November 07, 2025 @09:07AM (#45846538)
Right, but everywhere we look the universe is roughly the same at same distances, so it’s acceptable to extrapolate.
Re:Universe's expansion 'is now slowing, not speeding up' by mr_mitm on Friday November 07, 2025 @11:07AM (#45847815)
Even if not, it's still worthwhile to explore everything as far as we can see.
Re:Universe's expansion 'is now slowing, not speeding up' by wtcactus on Friday November 07, 2025 @11:11AM (#45847870)
Relativity restricts us to explore a very tiny sliver of the universe. We can observe, but we will never be able to interact unless Relativity is completely wrong.
Re:Universe's expansion 'is now slowing, not speeding up' by ghtbircshotbe on Friday November 07, 2025 @07:11AM (#45845618)
How does an infinitely oscillating universe comply with the 2nd law of thermodynamics?
Re:Universe's expansion 'is now slowing, not speeding up' by wtcactus on Friday November 07, 2025 @09:06AM (#45846520)
It doesn’t. Either the 2nd law is incomplete or the idea of bouncing universes starting from scratch with a clear state in entropy is impossible:

https://arxiv.org/abs/1010.5513