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.
I’m gonna wait for Scott Manley to discuss it before I form much of an opinion.
Analysis indicates that the universe’s expansion is not accelerating
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Re: Analysis indicates that the universe’s expansion is not accelerating
#112Mainstream 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?
Noether'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.
Noether'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.
Re: Analysis indicates that the universe’s expansion is not accelerating
#113Earlier quoted context omitted.
Wait but decelerating forever does in fact imply recollapse doesn't it?
An object on an escape trajectory from another mass is forever decelerating, but it still escapes.
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: Analysis indicates that the universe’s expansion is not accelerating
#114> 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 br…
> 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.
> 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.
Re: Analysis indicates that the universe’s expansion is not accelerating
#115If 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.
> it kind of fits a sine wave
But wavering around a line above y = 0.
Re: Analysis indicates that the universe’s expansion is not accelerating
#116“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…
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 in cosmology after decades of a standard LCDM model.
Re: Analysis indicates that the universe’s expansion is not accelerating
#117Earlier quoted context omitted.
That'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.
what? 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.
> no. religion is not certain
Religion allows for certainty. Science does not. Faith versus reason.
Re: Analysis indicates that the universe’s expansion is not accelerating
#118Maybe 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.
Re: Analysis indicates that the universe’s expansion is not accelerating
#119I picked the wrong week to put my faith in cosmology!
Re: Analysis indicates that the universe’s expansion is not accelerating
#120I 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+ ke…
Consider the scales involved. It's amazing that a species that is 99% chimp genes can even think and deduce phenomena of that size; don't ask it to get it right the first time. All of that without having traveled farther than one light second from its home.
It should humble all of us that believe we have absolute knowledge of things. So many people consciously or subconsciously philosophize about the universe, life, spirituality, etc. based on grand ideas and science which is routinely overturned. Really all we can prove is mathematical facts, and what our emotions tell us (i.e. "I Love You").