Analysis indicates that the universe’s expansion is not accelerating • Hacker News Board

Re: Analysis indicates that the universe’s expansion is not accelerating

#191

Post by andrewflnr » Fri, Nov 07, 2025, 5:31 PM UTC

mr_mitm wrote: post #156

andrewflnr wrote: post #127

> 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 de…

The 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 h…

Ah, I didn't realize dark energy also had evidence that far back. I can only recall seeing the supernova data cited for it.

Re: Analysis indicates that the universe’s expansion is not accelerating

#192

Post by mr_mitm » Fri, Nov 07, 2025, 5:55 PM UTC

andrewflnr wrote: post #191

mr_mitm wrote: post #156

Earlier quoted context omitted.

The 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 h…

Ah, I didn't realize dark energy also had evidence that far back. I can only recall seeing the supernova data cited for it.

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.

Re: Analysis indicates that the universe’s expansion is not accelerating

#193

Post by griffzhowl » Fri, Nov 07, 2025, 6:21 PM UTC

mr_mitm wrote: post #182

the__alchemist wrote: post #179

Earlier quoted context omitted.

I did a deep dive into cosmology simulations ~a year ago. It was striking how much is extrapolated from the brightness of small numbers of galaxy-surface pixels. I was looking at this for galaxies and stars, and observed something similar. The cosmology models are doing their best with sparse info, but to me it seemed that the predictions about things like Dark Matter and Dark Energy are presented in a way that's too…

That fuzziness can be quantified. It's called error bars. Whenever physicists perform a measurement, they always derive a confidence interval from the instruments they use. They take great care of accounting for the limits of each individual instrument, perform error propagation and report the uncertainty of the final result. Consider figure 5 of the following article for example: https://arxiv.org/abs/1105.3470 The…

It's not just a question of instrumental error though. There are also assumptions being used in interpreting the data from the instruments, and it's not generally possible to assign them reliable probabilities.

e.g. the first line of the article's abstract quoted above:

"Supernova (SN) cosmology is based on the key assumption that the luminosity standardization process of Type Ia SNe remains invariant with progenitor age."

If the results reported in the article are right, the confidence we should have in this assumption, and therefore any results relying on it, have just radically changed.

Re: Analysis indicates that the universe’s expansion is not accelerating

#194

Post by mr_mitm » Fri, Nov 07, 2025, 6:24 PM UTC

griffzhowl wrote: post #193

mr_mitm wrote: post #182

Earlier quoted context omitted.

That fuzziness can be quantified. It's called error bars. Whenever physicists perform a measurement, they always derive a confidence interval from the instruments they use. They take great care of accounting for the limits of each individual instrument, perform error propagation and report the uncertainty of the final result. Consider figure 5 of the following article for example: https://arxiv.org/abs/1105.3470 The…

It's not just a question of instrumental error though. There are also assumptions being used in interpreting the data from the instruments, and it's not generally possible to assign them reliable probabilities. e.g. the first line of the article's abstract quoted above: "Supernova (SN) cosmology is based on the key assumption that the luminosity standardization process of Type Ia SNe remains invariant with progenitor…

That's moving the goal post. I was specifically responding to concerns about fuzzy data.

It's true that assumptions have to be made, and those can and should be questioned, but that wasn't the concern of the comment I replied to.

Re: Analysis indicates that the universe’s expansion is not accelerating

#195

Post by the__alchemist » Fri, Nov 07, 2025, 6:29 PM UTC

mr_mitm wrote: post #194

griffzhowl wrote: post #193

Earlier quoted context omitted.

It's not just a question of instrumental error though. There are also assumptions being used in interpreting the data from the instruments, and it's not generally possible to assign them reliable probabilities. e.g. the first line of the article's abstract quoted above: "Supernova (SN) cosmology is based on the key assumption that the luminosity standardization process of Type Ia SNe remains invariant with progenitor…

That's moving the goal post. I was specifically responding to concerns about fuzzy data. It's true that assumptions have to be made, and those can and should be questioned, but that wasn't the concern of the comment I replied to.

My concern is model accuracy holistically; analyzing likelyness-to-be-correct including all assumptions; I think the post you are responding to is in context.

Re: Analysis indicates that the universe’s expansion is not accelerating

#196

Post by pinkmuffinere » Fri, Nov 07, 2025, 6:37 PM UTC

aatd86 wrote: post #176

aatd86 wrote: post #160

Earlier quoted context omitted.

Nope :) It 's not about that. It's not because I imagine that there is a banana in front of me that there will be. It's not tied to material existence in that way. It's perhaps another notion of existence which should be more mathematical. You could think it as "God" provably existing as an idea but that might or might not be realized probabilistically, in our material world. The idea exists obviously. Same as "Zeus"…

Funny thing is to ask: 'Is blue, blue?' Now with existence: 'Does existence, exist?' And then a bit differently: 'Is nothing something?' We see that these are different types of impredicativity. Existence just needs itself to define itself. Nothing cannot exist if nothing actually somehow is. It needs existence. Blue is a word. It does not exhibit the characteristic is describes. The set of all things blue does not c…

There are two main claims that I think you may be touching on:

1. The question of whether concepts exist in the absence of a human mind to imagine them. This is still debated in philosophy. I'm not an expert, so I won't make a claim about this, but I will point out that if it was easy to resolve, it probably wouldn't be a field of active debate after 2000+ years.

2. The question of whether it is necessary that _something_ physically must exist. This I do make a strong claim on: it is not necessary that something physically exist. There is no law that forces objects to exist. We find ourselves in a universe where objects do exist. This is not required. It just happens to be the case.

Side-note: I find the response "Nope :)" to be kindof condescending. I realize English may be a second language to you, so maybe you don't feel the subtle jab in that -- no worries if so, I'm sure I make the same mistakes in other languages all the time. Smiley faces are definitely allowed online, but in general I'd say to use them when making a joke or when acknowledging your own mistake.

Edit: In case somebody is curious, "the question of whether concepts exist in the absence of a human mind to imagine them" is debated at least since plato's time. I believe these concepts-that-exist-without-humans are sometimes called Platonic Forms. They are good for a wikipedia binge!

Re: Analysis indicates that the universe’s expansion is not accelerating

#197

Post by jameslk » Fri, Nov 07, 2025, 6:45 PM UTC

jampekka wrote: post #17

jimbo808 wrote: post #15

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.

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.”…

This sounds like something George Costanza would say

Re: Analysis indicates that the universe’s expansion is not accelerating

#198

Post by tekla » Fri, Nov 07, 2025, 7:13 PM UTC

ChrisMarshallNY wrote: post #161

negativelambda wrote: post #124

Earlier quoted context omitted.

Its 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.

Did he yell "They LAUGHED at me at Heidelberg! They said I was mad. MAD!" ? It is a very fundamental shift, though. The whole "Dark Energy/Matter" hypothesis has always seemed to me, to be a bit of a "Here, there be dragonnes" kind of thing, but I am nowhere near the level of these folks, so I have always assumed they know a lot that I don't.

I've never really gotten this criticism. Science has worked on "here be dragons" ever since it became a "thing".

Neutrinos took like 40 years to discover after experiments earlier showed that either all of modern particle physics was wrong, or there was something that we couldn't see.

Re: Analysis indicates that the universe’s expansion is not accelerating

#199

Post by aatd86 » Fri, Nov 07, 2025, 7:32 PM UTC

pinkmuffinere wrote: post #196

aatd86 wrote: post #176

Earlier quoted context omitted.

Funny thing is to ask: 'Is blue, blue?' Now with existence: 'Does existence, exist?' And then a bit differently: 'Is nothing something?' We see that these are different types of impredicativity. Existence just needs itself to define itself. Nothing cannot exist if nothing actually somehow is. It needs existence. Blue is a word. It does not exhibit the characteristic is describes. The set of all things blue does not c…

There are two main claims that I think you may be touching on: 1. The question of whether concepts exist in the absence of a human mind to imagine them. This is still debated in philosophy. I'm not an expert, so I won't make a claim about this, but I will point out that if it was easy to resolve, it probably wouldn't be a field of active debate after 2000+ years. 2. The question of whether it is necessary that _somet…

I thought the smiley would make the 'Nope' less argumentative. Sorry if you felt it was offensive.

This was in response to: > Side-note: the deontological argument is an argument for the existence of God, which uses the same principle as the grandparent

which was not actually true. This is not the same principle. Maybe the way I expressed the idea wasn't too clear. A close principle, would be Descartes' cogito perhaps...

The question of whether a concept exists even in the absence of the human mind is easy to answer. Without arguments to authority, it suffices to realize that every past event that predates a human being is a concept for that same human. Every future event, even what one is likely to do the next day, is also a concept.

Besides, why human? this is too anthropocentric. It should be extended to animals at the very least.

Or let's have another example: you don't really perceive UV light, and let's say you've never been told that it exists and you live in a cave. You will never interact with it. That does not mean that it does not exist. Whether as a physical concept or merely a pure concept which is then a probability. Even if that probability is 0 or negative even (negative??? we are veering quantum :).

It's probabilistic, not all of these concepts are realized materialistically (for future events that is).

An apple exists even in the absence of humans. So does its concept. Awareness of the existence of this concept is a different thing. One must not forget that, as wise and introspective as some of the ancients were, they were also prone to a lot of cognitive biases such as anthropocentrism.

In essence, my original point is closer to the one of greek philosopher Parmenides.

But this is again not about physical existence. Matter is just data with a set of properties and interaction rules. One of them being existence. A physicist would call matter a special kind of spatial perturbation perhaps.

On a whole other note, I am curious: what made it appear as if English was a second language? :)

Re: Analysis indicates that the universe’s expansion is not accelerating

#200

Post by aatd86 » Fri, Nov 07, 2025, 7:43 PM UTC

antonvs wrote: post #190

aatd86 wrote: post #158

Earlier quoted context omitted.

You have a material view of existence perhaps. How would the notion of nothingness even exist if there was no existence in the first place? And if we even accepted that nothing was possible, which in itself doesn't make any sense, how would something even start to exist? Well the contradiction is already in the fact that there is a preexisting concept of nothing in the first place. Existence is impredicative too. It…

> How would the notion of nothingness even exist if there was no existence in the first place? It wouldn't, that's the point. The is no need for a "notion of nothingness" if nothing exists. Why do you think nothingness doesnt't make any sense? It's a simple concept: no space, no time, and therefore nothing else such as matter, etc. > how would something even start to exist? Perhaps it wouldn't. We weren't talking abo…

Not really, in mathematic or type theory it is a proof. But that's besides the point. If there was nothing, then we wouldn't be able to describe it. We are only describing it because we think it might exist. So in itself it is illogical for it to exist since it can only exist if it does not exist.

Even if we had no data, the state before birth let's say, we still exist as a probability that is about to come to fruition. That is still besides the point.

If there was nothing, as you are trying to call it, there would not be existence. But then we would not be here. reductio ad absurdum. Even if life is a dream, it is still something, an experience. It is still an existence at some level. You are not discussing with nothing, while being nothing :)