If 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?
Analysis indicates that the universe’s expansion is not accelerating
141–150 of 218 posts
Re: Analysis indicates that the universe’s expansion is not accelerating
#142Standard 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…
>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.""
Well, 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.
Re: Analysis indicates that the universe’s expansion is not accelerating
#143We need an index tracking the expansion rate . And an ETF on it
Re: Analysis indicates that the universe’s expansion is not accelerating
#144Earlier quoted context omitted.
>>>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.
Is 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).
I 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.
Re: Analysis indicates that the universe’s expansion is not accelerating
#145If 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 Universe gong.
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Re: Analysis indicates that the universe’s expansion is not accelerating
#146Earlier quoted context omitted.
I'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.
The idea is that standard candles are based on chemistry and microscopic physics only, not cosmology.
If 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)
Re: Analysis indicates that the universe’s expansion is not accelerating
#147Anyone 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.
“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.
This is the thing that blows my mind the most with physics and cosmology
Re: Analysis indicates that the universe’s expansion is not accelerating
#148Earlier quoted context omitted.
I 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…
Just curious, is this dark matter holding back the universal expansion?
Our best guess is “maybe?”
Re: Analysis indicates that the universe’s expansion is not accelerating
#149Earlier quoted context omitted.
> 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.
Wait but decelerating forever does in fact imply recollapse doesn't it?
Nope, that would be velocity changing sign, which means acceleration would increase.
Re: Analysis indicates that the universe’s expansion is not accelerating
#150Earlier quoted context omitted.
> 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.
Wait but decelerating forever does in fact imply recollapse doesn't it?
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.