Re: The Big Crunch may be a possibility

On Sun, 23 Mar 2025 09:10:01 -0500, RonO <rokimoto557@gmail.com>
wrote:

On 3/23/2025 4:28 AM, jillery wrote:

On Sat, 22 Mar 2025 09:25:09 -0500, RonO <rokimoto557@gmail.com>
wrote:
 

On 3/22/2025 1:44 AM, jillery wrote:

On Fri, 21 Mar 2025 09:30:04 -0500, RonO <rokimoto557@gmail.com>
wrote:
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On 3/20/2025 5:27 PM, Kestrel Clayton wrote:

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On 20-Mar-25 17:33, RonO wrote:

https://www.nbcnews.com/science/science-news/dark-energy-changing-
understanding-rcna197386
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Dark energy may be waning, and the acceleration of our galaxies may
one day end.

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That's interesting. I couldn't tell from the Berkeley Lab public release
whether this new data suggest the rate of expansion is dropping, or if
the acceleration of the rate of expansion is decreasing (instead of
increasing, which is the current consensus). In other words, is it
slowing down, or just not speeding up quite as fast?
>

What would happen after the big crunch?  Would all the matter in the
universe eventually fall into one large black hole?  How much matter
can a black hole contain before something like the Big Bang happens?
There is already "evaporation" from black holes.  Would anything send
the evaporation out of control?  Could anything like a Big Bang occur
within a black hole to create a new universe within the event horizon?

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I'm fairly out of date on this, but before the discovery of dark energy,
the consensus was that the universe is either flat, or so close to
spherical as to be indistinguishable. That would indicate the expansion
of the universe would eventually halt, but the universe would not really
collapse. Instead, given enough time, the stars would all burn out, all
protons would eventually decay, and even the black holes would
evaporate, until all that remains are photons, electrons, and some
other, weirder particles. (However, I know photon decay is currently
considered less certain a prospect than in the 1990s, so YMMV.)
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Everything collapsing into a massive black hole still seems unlikely,
but if it did, that would simply be a different route to the photon age.
Eventually energy states are so low that quantum phenomena become the
biggest movers and shakers in the universe, and after that... we really
don't know. It's simply off the map, as far as modern physics goes.
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Fascinating stuff. Thank you for sharing the article!
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Google thinks that there might be enough dark matter and regular matter
in the universe so that the collapse would happen if the expansion stops.
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One science article that I read recently noted that inflation predicted
that there are parts of the universe that would not be visible to the
Webb telescope.  The fringe of our universe expanded away so fast that
there would be a sort of event horizon past which light has not reached
us inside the visible universe.  Sounds weird, but is all matter further
away than that horizon, part of the calculations about whether the
universe will collapse or not?
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Ron Okimoto

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You confuse inflation, the bang of the Big Bang, with cosmic expansion
apparently due to dark energy.  These are two separate phenomena with
different causes.
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Also, it's a matter of observation that galaxies are moving away from
Earth at speeds proportional to their distance.  This necessarily
means that at some distance called the Hubble Sphere, galaxies recede
from Earth faster than the speed of light.  This does NOT mean the
galaxies are moving FTL relative to their local space.
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An explanation.
https://www.facebook.com/neildegrassetyson/videos/how-the-universe-expands-at-light-speed-with-neil-degrasse-tyson/523350765610844/

 
 
Your link above appears to no longer refer to the original video.  The
video that now exists is 9.5 minutes long, but the text refers to
several time stamps greater than an hour.

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I still get the video.  Expansion acceleration and things looking like
things would exceed the speed of light starts at around six and a half
minutes.

IIUC Facebook is an unreliable link for source material, as its pages
are changed on a regular basis.  The video I see from your link has
NGT and one of his humor sidekicks talking about the effects of
Special Relativity, and how General Relativity puts no constraints on
the rate of cosmic expansion.

 

The claim is that the expansion of space accelerated faster than light
for parts of the universe that are no longer visible to us.  Space
expanded and nothing really accelerated to faster than light, but they
are just too far away to observe.  There was the initial inflation when
space expanded much faster than the speed of light creating a "flat
universe" with just the right amount of mass and energy to keep it from
collapsing.  Dark energy is supposed to account for the continued
expansion of space within the universe.  One article that I recall
claimed that the visible universe extends out to around 45 billion light
years in all directions from where we are.  The visible light has to be
younger than the age of our universe (less than 14 billion years), but
space has expanded.

 
 
An important point is, according to the evidence, there was a time
before about 4bya when the universe was dominated by gravity, and its
rate of expansion was actually slowing.  Now the universe is dominated
by dark energy, and so its rate of expansion has become ever faster
since then.

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The claim in the article is that the expansion of the universe continues
to be currently accelerating, but the rate of acceleration is
decreasing, so dark energy effects seem to have limits.

What you say above is contrary to what I have read:
<https://en.wikipedia.org/wiki/Dark_energy#Evidence_of_existence>
********************************
In 1998, the High-Z Supernova Search Team published observations of
Type Ia ("one-A") supernovae. In 1999, the Supernova Cosmology Project
followed by suggesting that the expansion of the universe is
accelerating. The 2011 Nobel Prize in Physics was awarded to Saul
Perlmutter, Brian P. Schmidt, and Adam G. Riess for their leadership
in the discovery.
********************************

I recall an article claiming that our current visible universe extended
out to around 45 billion light years in any direction (maybe it was 45
billion light years across, the light within visible space has to be
less than 14 billion years old) but there has to be a lot of the
universe that we can no longer see.  Kestrel indicated that this limit
applied to the points within our visible universe so that every location
had a different horizon and could see a different part of the existing
universe.  There would have to be a lot of matter that is not in the
visible universe.

Correct.  This is something I pointed out to Peter Nyikos awhile ago,
and I pointed out to you in my last post.  Every point in the cosmos
is surrounded by its own Hubble Sphere.  The working assumption is
that the cosmos outside our Hubble Sphere is largely similar to the
space inside.  The problem is there is no way to know this for
certain, even in principle.

Ron Okimoto

 
 

It doesn't matter, what I wanted was if the mass of the universe
estimate includes the mass that is not observable.  We have the
background radiation map of the universe, and estimates based on what we
can see (these are based on the observable universe).  The estimates
would have included what we could not see within the visible universe
because we lacked the ability to detect the light from the distant
objects.  Did this estimate also include the mass that was too far away
to be visible?  How do we know how much mass is no longer visible and is
beyond the horizon of what we can see?  We've been trying to estimate
the amount of dark matter within the visible universe, so how would we
measure the amount of matter further away than the visible horizon?
Even though we can't observe it, it is still part of our universe.
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Ron Okimoto

 

--
To know less than we don't know is the nature of most knowledge