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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

#121

Post by nabakin »

negativelambda wrote: post #116
JumpCrisscross wrote: post #84

“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…

Is there a recording of their seminar anywhere?

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

#122

Post by kittikitti »

This 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.

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

#123

Post by gorbot »

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…

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.

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

#124

Post by negativelambda »

nabakin wrote: post #121
negativelambda wrote: post #116

Earlier 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…

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.

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

#125

Post by recursivecaveat »

Razengan wrote: post #30
indoordin0saur wrote: post #7

Earlier quoted context omitted.

The universe was always only expanding between galaxies, not within them.

So wait, individual stars aren't getting further apart? Galaxies aren't getting "bigger"/more diffuse?

Imagine the universe as a giant balloon. Inside are little miniature balloon stars floating around, tied with string into balloon galaxies. If we heat the air: the big balloon expands, the clusters of mini-balloons spread out from the other clusters, but the clusters don't get any more diffuse. The string is way way too strong to be overpowered by the separating force from the expansion of the gas over short distances.

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

#126

Post by negativelambda »

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…

It could be a big discovery and it also aligns with the findings from DESI BAO [1] and by another Korean group using galaxy clustering to infer the expansion history [2].

[1] https://arxiv.org/abs/2404.03002

[2] https://arxiv.org/abs/2305.00206

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

#127

Post by andrewflnr »

> 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?

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

#128

Post by AceyMan »

antihipocrat wrote: post #56
bombdailer wrote: post #50

Earlier quoted context omitted.

Eventually we will find that the heat death of the universe and the big bang are the same thing, since the totality of the universe is always a oneness, then from the universal perspective the infinitely small and infinitely large are the same thing (one), then they by nature bleed into (and define) each other like yin and yang.

You may appreciate this idea: https://en.wikipedia.org/wiki/Conformal_cyclic_cosmology

Penrose? That guy, again. /s

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

#129

Post by mkl »

michaelmrose wrote: post #67
mkl wrote: post #43

Earlier quoted context omitted.

If you can get to a star 100 light years away, you can get to Andromeda. It doesn't require going faster, just waiting longer.

I feel like waiting longer in some sense may itself represent a substantial increase in difficulty in terms of creating something which remains stable for tens of thousands of years. On the other hand who knows with zero samples how stable societies are thousands of years beyond our present level of development.

Yes, that's why I said 100 light years rather than 4.3. Maybe it's still too low, but I think there are targets within the Milky Way that would require solving pretty much all the problems of getting to Andromeda.

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

#130

Post by ngold »

negativelambda wrote: post #116
JumpCrisscross wrote: post #84

“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…

Just curious, is this dark matter holding back the universal expansion?
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