Wizard of Whatever
Registered Senior Member
It may indicate the expansion may eventually stop and maybe even reverse.
The Universe's Expansion May Be Slowing Down, Not Speeding Up ?
- Thread starter Killjoy
- Start date
I think I got that from the thread that pinball shared with us
Strong Progenitor Age Bias in Supernova Cosmology
The thread title is the first part of the title of a paper published just today [1]. Here is the abstract: 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...
Not sure if it is ahead of the subject.Certainly interesting if Steady State was to come back into play as a possibility.
exchemist
Valued Senior Member
Why should that be? It is still expanding, which is in line with the Big Bang hypothesis. Steady State would mean no expansion.I think I got that from the thread that pinball shared with us
Post#12Strong Progenitor Age Bias in Supernova Cosmology
The thread title is the first part of the title of a paper published just today [1]. Here is the abstract: 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...www.physicsforums.com
Not sure if it is ahead of the subject.Certainly interesting if Steady State was to come back into play as a possibility.
Jarek Duda
Registered Senior Member
This thread starts with - indeed there are e.g. recent DESI observations that dark energy is weakening, suggesting Big Crunch, e.g.:
Physicists Predict When The Universe Will End in a Reverse Big Bang
If recent discoveries that dark energy is evolving hold any water, our Universe will collapse under its own gravity on a finite timeline, new calculations suggest.
www.sciencealert.com
Physicist: After 33 billon years, universe ‘will end in a big crunch’ | Cornell Chronicle
After expanding to its peak size about 11 billion years from now, the universe will begin to contract – snapping back like a rubber band to a single point at the end, according to a Cornell physicist.
Study says the universe will 'end in a big crunch' and scientists predict when it will happen
We’ve grown up with the idea that the universe will expand forever, meaning the "cosmological constant" is positive. What if it's negative?
Is dark energy getting weaker? Fresh data bolster shock finding
Physicists had long assumed that the elusive force has constant strength. But the latest results from a project to map the Universe’s expansion challenge this idea.
www.nature.com
Big Crunch would be time reversed Big Bang, so should have tendency to form time reversed black holes: white holes ... we might be able to observe to verify.
Last edited:
Pinball1970
Valued Senior Member
You have a thread for white holes do not derail this thread. We are discussing SN environments and how they have been factored into this study.This thread starts with - indeed there are e.g. recent DESI observations that dark energy is weakening, suggesting Big Crunch, e.g.:
Physicists Predict When The Universe Will End in a Reverse Big Bang
If recent discoveries that dark energy is evolving hold any water, our Universe will collapse under its own gravity on a finite timeline, new calculations suggest.Physicist: After 33 billon years, universe ‘will end in a big crunch’ | Cornell Chronicle
After expanding to its peak size about 11 billion years from now, the universe will begin to contract – snapping back like a rubber band to a single point at the end, according to a Cornell physicist.news.cornell.edu
Study says the universe will 'end in a big crunch' and scientists predict when it will happen
We’ve grown up with the idea that the universe will expand forever, meaning the "cosmological constant" is positive. What if it's negative?www.earth.com
Is dark energy getting weaker? Fresh data bolster shock finding
Physicists had long assumed that the elusive force has constant strength. But the latest results from a project to map the Universe’s expansion challenge this idea.
Big Crunch would be time reversed Big Bang, so should have tendency to form time reversed black holes: white holes ... we might be able to observe to verify.
if the acceleration is lessening,what happens when (if?) it becomes less than zero?
Does expansion gradually stop and if it does, does it turn into contraction or might it find an equilibrium which could look like the Steady State even if not the Steady State that Hoyle assumed?(well I am not really familiar with what the Steady State was actually meant to be)
Last edited:
Pinball1970
Valued Senior Member
Steady state was totally different and pretty much debunked in the 60s.
Pinball1970
Valued Senior Member
If it stops that is still not steady state. SS claimed that new mattress was produced as the Universe expanded which is not a halt.
Pinball1970
Valued Senior Member
No beginning, it can still expand adding matter so the overall density remains the same.
Disproven in the 60s.
Maybe you should lie down.This is clearly an overwhelming turnaround.
I blame the auto incomplete.
exchemist
Valued Senior Member
God knows. None of this speculation is yet appropriate in my view. All we have is a challenge to the standard idea of a constantly accelerating expansion, driven by this nebulous Dark Energy concept that nobody has a handle on. The implication is that the lambda in the Lambda Cold Dark Matter hypothesis may have to be reassessed and possibly replaced with some other, potentially time-dependent function.
TheVat
Valued Senior Member
At least the SS theory had a soft landing when it toppled.
ETA - I see I'm not the first to...spring on that typo.
Last edited:
TheVat
Valued Senior Member
Hoyle had that brain-bending infinity conundrum, if I recall. The universe has no beginning and so has been expanding for an infinite period of time and creating an infinite amount of mattresses, er, matter. An infinity of space can contain an infinite mass. And well, in principle, there could be infinite mattresses. Hilbert's Hotel would have that.
Pinball1970
Valued Senior Member
I think the CMBR put steady state to bed, so to speak.
exchemist
Valued Senior Member
But he did at least give us the name “Big Bang” , for the theory he was trying to ridicule.
Pinball1970
Valued Senior Member
Yes that was he.
Jarek Duda
Registered Senior Member
Pinball1970
Valued Senior Member
What? In words please.
Pinball1970
Valued Senior Member
I try not post YouTube videos, here is a quote on PF from Sabine Hossenfelder (the Hoss)
"Basically, they say that it's wrong to conclude that the expansion of the universe is accelerating. It's just that younger galaxies have on average dimmer supernovae. They don't say why this might be the case. They simply say this is what the data really say. And this isn't one of those maybe results with low statistical significance. This is a whopping 5.5 sigma correlation which they call a serious systematic bias."
One interesting comment was that this factor is not new to the cosmological community, just that it is not as significant as this paper suggests.
We can expect more on this since so much is at stake.
"Basically, they say that it's wrong to conclude that the expansion of the universe is accelerating. It's just that younger galaxies have on average dimmer supernovae. They don't say why this might be the case. They simply say this is what the data really say. And this isn't one of those maybe results with low statistical significance. This is a whopping 5.5 sigma correlation which they call a serious systematic bias."
One interesting comment was that this factor is not new to the cosmological community, just that it is not as significant as this paper suggests.
We can expect more on this since so much is at stake.