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Analysis indicates that the universe’s expansion is not accelerating
- denismenace 10mo agoDid it change during our life time?
- oofbey 10mo agoJust our understanding of it. That’s flipped multiple times in my lifetime.
- samdoesnothing 10mo agoThanks, AI.
- karakot 10mo agoWhat does 'now' mean here?
- plasticchris 10mo agoProbably it means that now we have evidence that… it is a colloquialism Edit: yep, The universe's expansion may actually have started to slow rather than accelerating at an ever-increasing rate as previously thought, a new study suggests.
- sermah 10mo agoRecent years, probably because of large data centers /s
- deleted 10mo ago[deleted]
- thelibrarian 10mo agoGoing by the second graph, since about 2.5 billion years ago.
- 2OEH8eoCRo0 10mo agoWhat happened to then?
- candiddevmike 10mo agoAside from unanswerable questions (has the universe started to fill it's container? Is a simulation property nearing "1"?), does this make long distance space travel feasible again? I thought there was something around the universe is expanding too fast to visit places like Alpha Centuri (and preventing visitors to us).
- indoordin0saur 10mo agoThe universe was always only expanding between galaxies, not within them.
- Razengan 10mo agoSo wait, individual stars aren't getting further apart? Galaxies aren't getting "bigger"/more diffuse?
- kmeisthax 10mo agoGalaxies have enough gravity to counteract the expansion of the universe.
- Razengan 10mo agoSo do we see the expansion cancelled out by the gravity, or do we only see the gravity? I mean, is it change = gravity or change = expansion - gravity Because this just made me wonder.. is "dark energy" simply the absence of gravity? i.e. just in regions where there is next to no matter/activity?
- JumpCrisscross 10mo ago> do we see the expansion cancelled out by the gravity, or do we only see the gravity? We see gravity overpowering expansion. Same way you can’t launch yourself into orbit by throwing lots of pennies at one a second.
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- redwood 10mo agoWas there a date at the top of this? I didn't see one. I saw a similar headlines earlier this year and I'm trying to understand that this is something new
- felixfurtak 10mo agothe linked journal article is dated Nov 6 2025
- observationist 10mo ago>>>Submitted by Sam Tonkin on Thu, 06/11/2025 At the very bottom. Weird how style guides keep putting important information like this in harder to reach places.
- palmotea 10mo agoIs it SEO? IIRC there's a trend of removing dates from blog posts and articles, and my understanding it's to make the content seem more "evergreen" to Google (vs and article with a date, they may get down-ranked eventually due to age).
- observationist 10mo agoI'm thinking it's SEO cargo culting, and that there are a lot more "monkey see, monkey do" patterns of behavior that don't impact actual ranking but nonetheless crop up in weird things like this. That said, I cannot wait for adtech to go the way of the rotary phone. Localized, private search indexes on phones with local AI interacting with them, only reaching out to the internet when necessary to update information, with hashes and checksums to minimize the number of updates needed for frequently interacted sites, and so on. Google right now is hot garbage - most tiny competitors are far better, let alone yandex or kagi or the like.
- somat 10mo agoI thought the SEO was to keep churning out garbage articles in order to make the page more desirable to search engines because it was more recent. At least that is how it feels, like the search engines are promoting recent content over good content and pages take advantage of this by auto generated trash. to the point I won't even look at a page if it has a date in the last year.
- jimbo808 10mo agoAnyone 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.
- jampekka 10mo agoAt 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-expansion-slowing-not-accelerating-nobel-prize https://www.theguardian.com/science/2025/nov/06/universe-exp...
- HeinzStuckeIt 10mo agoAs 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.
- ImPostingOnHN 10mo agoIt's also something you could say if you forgot to read the assignment and the professor called on you.
- piker 10mo ago"It makes some profound points, yes. What if? BUT what if not?"
- mr_mitm 10mo agoI read it as "I recognize some of the names and the abstract doesn't sound like complete nonsense".
- sfink 10mo agoIf you cover up the part of the Figure 3 graph past "now", it kind of fits a sine wave. https://ras.ac.uk/sites/default/files/2025-10/Figure%203.jpg https://ras.ac.uk/sites/default/files/2025-10/Figure%203.jpg Universe gong.
- ASalazarMX 10mo agoThat's a very thought provoking observation, as if the whole universe behaved like a wave.
- mrb 10mo agoA funny coincidence is that the solar system was formed 4.6 billion years ago which is exactly when the universe's rate of expansion peaked according to figure 3. If you want to believe in an intelligent creator—not that I do—it's as if they were accelerating the expansion until the solar system was formed, then turned the control knob down.
- Terr_ 10mo agoTurns out the universe is one giant PID controller.
- jdthedisciple 10mo agoInteresting observation.
- JumpCrisscross 10mo ago> it kind of fits a sine wave But wavering around a line above y = 0.
- nQQKTz7dm27oZ 10mo ago[dead]
- ertgbnm 10mo agoSeems like the problem should be pretty easy to figure out. Just need to wait ~5 gigayears and see which model is right. I'm personally hoping for deceleration so that we have more total visitable volume. I'll set a reminder to check back at that time to see who was right.
- mabster 10mo agoI just pictured someone getting a message to check which model was right from an ancestor 20 giga generations ago!
- channeleaton 10mo ago!remindme 20,000,000,000 years
- shadowgovt 10mo agoOh, I'm not going to care about visitable volume. With 5 gigayears to work with I'm going to move a few star systems over, break down all the matter orbiting the star into a Dyson sphere made of computronium, and simulate visiting any world I could possibly ever want to.
- qingcharles 10mo agoThis is one reason to assume we'll never meet any aliens. They're just simulating whatever all day long in their Dyson Goonspheres.
- aatd86 10mo agoI would not be surprised if the universe was somewhat elastic, expands and then contracts and then expands ad infinitam. After all, existence in itself is irrefutable and cannot not exist by definition. If we subscribe to a theory of the multiverse, set theory, likelihood, and interaction driven evolution based on gradient type of fundamental laws. Locally changing. Obviously everything sharing a fundamental quality that is part of existence itself. But obviously there are sets, there is differentiation. But it is not created, the infinity of unconstrained possibilities exists in the first place and reorganizes itself a bit like people are attracted to people who share some commonalities or have something they need from each other and form tribes. Same processus kind of works for synapse connections, works for molecule formations, works for atoms... etc... Everything is mostly interacting data. We could say that the concept of distance is a concept of likelihood. The closer is also the most likely. Just a little weird idea. I need to think a bit more about it. Somewhat metaphysic?
- antonvs 10mo ago> After all, existence in itself is irrefutable and cannot not exist by definition. I can say the same about forgnoz, which is something I've just invented that must exist by definition. You'd need to try a bit harder to make existence actually inevitable.
- pinkmuffinere 10mo agoYou’re being downvoted, but your point is true — something can exist “by definition”, and yet not exist in our real world. The thing that exists “by definition” is just a version that we have imagined to exist by definition. But imagining something with property X doesn’t imply anything can actually be found with property X. Side-note: the deontological argument is an argument for the existence of God, which uses the same principle as the grandparent. “Imagine God. Imagine God is good. A good God should exist, because otherwise that god is not good. Therefore, the good God we imagined has the property of existence. Therefore God exists”. The issue is exactly the same — we can imagine something with property X, but that doesn’t mean we can find something with property X
- nabakin 10mo ago> type Ia supernovae, long regarded as the universe’s "standard candles", are in fact strongly affected by the age of their progenitor stars. A key point in the article. From what I understand, this is the main way we measure things of vast distance and, from that, determine the universe's rate of expansion. If our understanding of these supernovae is wrong, as this paper claims, that would be a massive scientific breakthrough. I'm really interested in the counterargument to this.
- stronglikedan 10mo ago> If our understanding of these supernovae is wrong, as this paper claims, that would be a massive scientific breakthrough. Indeed. It's so hard to definitively prove things that are, that the most significant breakthroughs prove things that aren't (so to speak), imho.
- JumpCrisscross 10mo ago> It's so hard to definitively prove things that are, that the most significant breakthroughs prove things that aren't (so to speak), imho Significant breakthroughs do both. Prove things aren’t as we thought. And are as the new model suggests.
- gorbot 10mo agoI'm dumb and barely understand things at a high level, but standard candles never sat right with me so it's interesting to hear that they might not be, but then again who knows.
- jiggawatts 10mo agoThe idea is that standard candles are based on chemistry and microscopic physics only, not cosmology.
- alfiedotwtf 10mo agoIf I remember correctly (sorry it’s been a while), the size of the star determines its colour, and the data suggests that the colour of stars fits nicely into the mass of a star (ie you’ll never see a star of X color thats Y kg)
- ardit33 10mo agoCircular universe...? big bang -> expands -> expansion slows -> starts retracting -> singularity again -> big bang again Roger Penrose seems to be leaning/more convinced of the circular universe theory....
- johnwheeler 10mo agoJust because infinity is a hard thing to understand doesn't mean the universe is and has always been infinite.
- mrbluecoat 10mo agoI have a great deal of respect for the sciences but sometimes astronomy just feels like one giant guessing game: age of the universe, big bang starting as a joke and all the "first minute" timelines thereafter, dark energy and dark matter (code for we have no idea what it is) vastly outnumbering everything else, and now questioning the Nobel Prize-awarded universe expansion. Meanwhile, asteroids the size of buses+ keep whizzing by closer than the moon with little or no warning. Sigh.
- CamperBob2 10mo agoThat's a feature! If you want to be certain, you need religion, not science. And of course, the people concerned with tracking near-earth asteroids are not connected in any way with cosmology.
- dylan604 10mo agowhat? no. religion is not certain which is evidenced by the numerous sects of christianity with their own interpretations of the same book. while science might not have a definitive answer for everything, they distinguish from fact and theory.
- ASalazarMX 10mo ago> religion is not certain Ask any religious person if their religion teaches truth or lie, then ask them if that truth is the absolute truth. We'll wait.
- shomp 10mo agoMainstream physics has been delighted to ignore/abandon essential conservation laws when talking about the expanding universe. It's kinda weird, I tried publishing a paper on it recently and it was not received well. In general, if conservation laws are to hold, expansion must be balanced with [eventual] contraction, is that not obvious? Apparently it was quite contentious to say until... this article?
- antognini 10mo agoNoether's theorem tells us when we would expect conservation laws to hold and when we would expect them to fail. In the case of global energy conservation, there would have to be a global time invariance associated with the spacetime. But this is manifestly not the case in an expanding universe. It is generally not even possible to have a well defined notion of global energy in a dynamic spacetime.
- shomp 10mo agoNoether's theorem tells us when symmetry guarantees conservation, but it says nothing about conservation in the absence of that symmetry - it's not a biconditional statement. Talking about endless expansion is like observing 1 second of a pendulum's swing and concluding there's no time symmetry because it's only moving in one direction. The symmetry exists at the full cycle scale, not the snapshot scale.
- antognini 10mo agoIt's true that it leaves open the possibility of a conserved quantity that is not associated with a symmetry. But the kinds of conservation laws we are thinking about, like conservation of energy, do originate from a symmetry. So if the symmetry is broken it is very reasonable to assume that the conservation law would be broken as well.
- zygentoma 10mo agoNo, the assumption was that dark energy is a property of space itself so it does not conserve energy at all in an expanding space. Also this discovery does still is being explained with dark energy (albeit time varying …) so it still does not assume global energy conservation.
- socrateswasone 10mo ago[dead]
- gmuslera 10mo agoSomeone dumped a flat panel near a noisy planet.
- wtcactus 10mo agoStandard candles (all these measurements of redshift according to distance, need us to actually get the distance of what we are measuring right) are the gift that keeps on giving. This study (and many others, depending on the cosmic scales they use) mainly use Supernovas of Type Ia. I.e. the energy emitted by the supernova of a binary acreccion star, which is a star that is capturing the mass from another start that is very nearby and increasing its mass until it collapses into itself, increases temperature up to the point it starts fusing helium, and goes supernova with all the added energy. That was (and still is now, with some corrections we found since middle last century) supposed to be the same everywhere. Problem is, we keep finding new corrections to it - like this study claims. That is in fact the big claim of this study (ignore the universe expansion part), that they found a new correction to the Supernova of type Ia luminosity. It's a very big claim and extremely interesting if confirmed. But, like all big claims, it needs a big confirmation. I'm a bit skeptic TBH.
- jldl805 10mo ago>I'm a bit skeptic Out of curiosity, what data are you drawing or what qualifications do you have that support your skepticism over three different modes of analysis (as well as pretty much every recent development in the field) supporting this claim: "Remarkably, this agrees with what is independently predicted from BAO-only or BAO+CMB analyses, though this fact has received little attention so far.""
- wtcactus 10mo agoWell, this part you mention, for instance "though this fact has received little attention so far". A change on the standard candles calibration would be a huge deal for cosmology and galactic astronomy (and other fields) and would not be taken lightly at all. There are all sorts of ramifications from this and if astronomers aren't all in an oof about it, it is because big proof is needed for big claims. And a change in the standard candles calibration is indeed a very big claim.
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- JumpCrisscross 10mo ago“Supernova (SN) cosmology is based on the key assumption that the luminosity standardization process of Type Ia SNe remains invariant with progenitor age. However, direct and extensive age measurements of SN host galaxies reveal a significant (5.5σ) correlation between standardized SN magnitude and progenitor age, which is expected to introduce a serious systematic bias with redshift in SN cosmology. This systematic bias is largely uncorrected by the commonly used mass-step correction, as progenitor age and host galaxy mass evolve very differently with redshift. After correcting for this age bias as a function of redshift, the SN data set aligns more closely with the cold dark matter (CDM) model” [1]. [1] https://academic.oup.com/mnras/article/544/1/975/8281988?login=false https://academic.oup.com/mnras/article/544/1/975/8281988?log...
- negativelambda 10mo agoI know the team that did this. In fact i was listening to their seminar just a few days ago. They are very careful and have been working on this a long time. One caveat that they readily admit is that the sample used to create the luminosity age relation has some biases such as galaxy type and relatively lower redshift. They will be updating their results with the Rubin LSST data in the next few years. Exciting times in cosmology after decades of a standard LCDM model.
- nabakin 10mo agoIs there a recording of their seminar anywhere?
- negativelambda 10mo agoIts not publicly available. Maybe for the best haha. The speaker at some point went on a bit of a tirade against many people in the supernovae cosmology community. I think he endured many years of being ignored or belittled.
- ChrisMarshallNY 10mo ago
- animanoir 10mo ago[dead]
- CommenterPerson 10mo agoMaybe someone is tailgating it. And it's trying to annoy them by speeding up, then slowing down. There seem to be so many fudge factors in the whole chain of analysis we won't have an idea until we can make vastly improved measurements.
- WalterBright 10mo agoI picked the wrong week to put my faith in cosmology!
- kittikitti 10mo agoThis is a fascinating discovery! It's brings into focus the Deep Field imagery from the JWST and how gravitational lensing was found to be greater than expected along with galaxies that were much older than expected based on redshift calculations. Perhaps this could indicate that the universe is even older than we originally thought if redshift calculations accounted for an incorrect perpetual acceleration.
- andrewflnr 10mo ago> The corrected supernova data and the BAO+CMB-only results both indicate that dark energy weakens and evolves significantly with time. > More importantly, when the corrected supernova data were combined with BAO and CMB results, the standard ΛCDM model was ruled out with overwhelming significance, the researchers said. I notice they're not saying that dark energy is entirely unnecessary. Do we know if that's just default caution, or are there still strong reasons to believe dark energy exists?
- mr_mitm 10mo agoThe CMB and BAO measurements give us a picture of how the early universe looked. Supernovae are sensitive to the conditions in the late universe. All probes, which are mostly independent, always pointed at the same amount of dark energy. Now these people are saying SN actually point at zero dark energy, if accounting for the physics properly. That doesn't invalidate the CMB and BAO results. So dark energy must have had a big influence in the early universe, and no influence in the late universe, so it must by dynamic. (Ironically, supernovae were the first evidence for dark energy, which I guess was just a coincidence, if this new research is correct.)
- andrewflnr 10mo agoAh, I didn't realize dark energy also had evidence that far back. I can only recall seeing the supernova data cited for it.
- mr_mitm 10mo agohttps://phys.org/news/2020-06-dark-energy-expansion-cosmic.amp https://phys.org/news/2020-06-dark-energy-expansion-cosmic.a... Check the first plot. Four different probes all agree on the same value. Well, used to, if this pans out. The blue one would be somewhere on the x axis now.
- cosmicjoe 10mo agoAs a non-scientist I've always found the Cosmic Distance Ladder as likely to be inaccurate due its assumption about the constant brightness of Standard Candle stars over their lifetime, and the compounding of error at each rung of the ladder. Direct measurement of the CMB seems to be simpler with less chance of error. https://en.wikipedia.org/wiki/Cosmic_distance_ladder https://en.wikipedia.org/wiki/Cosmic_distance_ladder
- XorNot 10mo agoDirect measurement of the CMB can also have problems if our assumptions about it are wrong. A major goal of having two methods is that they should coalesce to the same result within margin of error - that they didn't told us we were missing something.
- wtcactus 10mo agoThe supernovas type Ia luminosity depends on their composition and that takes into account both the age of the supernova and of the donator star. And that can be inferred by the luminosity curve of the supernova. https://en.wikipedia.org/wiki/Type_Ia_supernova https://en.wikipedia.org/wiki/Type_Ia_supernova
- naasking 10mo ago> I've always found the Cosmic Distance Ladder as likely to be inaccurate due its assumption about the constant brightness of Standard Candle stars over their lifetime Stars are just basic nuclear physics and gravity, that's why they're expected to be stable and predictable. > Direct measurement of the CMB seems to be simpler with less chance of error. Direct measurement of the CMB doesn't tell you anything on its own, you have to interpret the data in terms of a model. If you have a completely different model, say one without dark energy or without dark matter, CMB measurements would tell you something different than LCDM.
- eterevsky 10mo agoIf they are replacing a fixed cosmological constant by a model with variable dark energy, doesn't it introduce extra parameters that describe the evolution of dark energy over time? If so, wouldn't it lead to overfitting? Can overfitting alone explain better match of the new model to the data?
- seydor 10mo agoWe need an index tracking the expansion rate . And an ETF on it
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- mr_mitm 10mo agoLooks like their colleagues have some serious doubts about this study: https://xcancel.com/dscol/status/1987118124496249230 https://xcancel.com/dscol/status/1987118124496249230
- amai 10mo agoI saw it coming: https://news.ycombinator.com/item?id=44143502 https://news.ycombinator.com/item?id=44143502