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Analysis indicates that the universe’s expansion is not accelerating

ras.ac.uk

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

#161

Post by ChrisMarshallNY »

negativelambda wrote: post #124
nabakin wrote: post #121

Earlier quoted context omitted.

Is there a recording of their seminar anywhere?

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.

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

#162

Post by alfiedotwtf »

jiggawatts wrote: post #153
alfiedotwtf wrote: post #146

Earlier quoted context omitted.

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)

The rule is violated in all sorts of fun and interesting ways. There's white dwarfs, for one, then stars with varying levels of metallicity. Stars can merge, which does strange things to their position on the Hertzsprung–Russell diagram. There's oddball combinations like a red giant with a neutron star that has sunk into its core, called a Thorne–Żytkow Object! Not to mention variable stars, novae, occultation by dus…

Great Scott look at your username!

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

#163

Post by p00dles »

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.”…

That guy should start a PR firm

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

#164

Post by ghtbircshotbe »

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.

How does an infinitely oscillating universe comply with the 2nd law of thermodynamics?

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

#165

Post by jdthedisciple »

mrb wrote: post #90
sfink wrote: post #23

If 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.

A 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.

Interesting observation.

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

#167

Post by basch »

nabakin wrote: post #32

> 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…

This is mostly my physics ignorance talking, but if we measure distance in space-time and not just space, and speed or velocity is space-time/time (which somehow are both relative to each other) and the derivative of velocity is acceleration, cant acceleration mean either expanding "faster" in the sense of distance OR time speeding up or slowing down? All of it seems so self referential its hard to wrap around.

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

#168

Post by mr_toad »

omnicognate wrote: post #91
hn_acc1 wrote: post #24

Earlier quoted context omitted.

I found someone saying colonize the Milky Way Galaxy in ~90m years? Is that what you meant? The observable universe is ~93B LY - unless you're assuming FTL (and MUCH faster than light), I don't see how that's possible?

Time dilation means that you can get anywhere while experiencing an arbitrarily small amount of time. You can cross the galaxy in a second as far as special relativity is concerned. (With the expenditure of insanely vast amounts of energy, ofc.) To an observer back home you'd look like you're travelling at merely extremely close to the speed of light, but to you the journey would take a second.

> You can cross the galaxy in a second as far as special relativity is concerned.

Sure, but the rest of the universe will keep on changing. In 90 billion years it’s going to be a very old universe. Galaxies will become consolidated and isolated, fewer young stars will be born. Only the dim light of red dwarf stars will shine among a graveyard of dead stars.

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

#169

Post by negativelambda »

mr_mitm wrote: post #154
JumpCrisscross wrote: post #140

Earlier quoted context omitted.

> after decades of a standard LCDM model Could you help me understand this sentence: "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”?

The CDM model has no dark energy, unlike the LCDM model. The L stands for Lambda, which is the dark energy term in the Einstein equations. So they are saying when accounting for this effect, our universe looks more like a universe without dark energy, at least when only considering the supernovae probe.

That's only if you consider the supernovae data alone. In combination with other probes like BAO, etc, the combined data are pointing to a Universe with a dynamical (or time varying) dark energy model.

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

#170

Post by mr_toad »

delta_p_delta_x wrote: post #25
Sharlin wrote: post #16

Earlier quoted context omitted.

Edit: A big brain fart, ignore the retracted part below. Colonizing the universe is of course impossible in 100My, barring FTL. What the paper I referred to [1] says is that colonizing the Milky Way may take less than that, and if you can do that, spreading to the rest of the observable universe is fairly easy, very relatively speaking. According to some calculations, it should in principle be possible to colonize th…

> The relative jump in difficulty from interstellar to intergalactic is much smaller than from interplanetary to interstellar. Interesting way to put it... This doesn't seem that accurate. With sufficiently advanced technology, many of which we already possess, we could expect to propel a minute spacecraft to a considerable fraction of the speed of light, and reach nearby stars possibly within the end of the century.…

The distance to andromeda is only about 20 times the width of our galaxy. And there are dwarf galaxies than are much closer.
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