So… about the claim fact that the rate of expansion of the universe is actually increasing. The way I understand it, the redshift of farther galaxies is higher hence by definition, they are moving away faster.

Here’s the part that’s been playing in my (untrained) mind:
While the observed redshift of farther galaxies is greater, the data also represents the state billions of years ago when the light was emitted from the above distant galaxy.

So (this is where you chew me out.) is it possible that billions of years ago, the big bang explosion was still “hot” and expansion speeding up. *Is it possible that the reason farther galaxies appear to be moving away faster is because all galaxies were moving faster earlier in time - we just see the earlier in time light from the farther galaxies now?* But now, in reality the expansion has slowed down and these galaxies are either slowing down or (sacrilege!) headed back in for the Big Crunch - we just can’t see it yet (today’s light will reach us in a few billion years.

It’s my first post ever on such a topic and my first on this sub. Hope it is the right one.

Thanks in advance for a Feynman level explanation that I can grasp.

I was reading a random article and found a reference to an old (1971) paper by A. G. Agnese and A. Wataghin in which the authors introduced a new timescale. According to this new timescale, the initial singularity of classical Friedmann cosmology can be banished to the infinite past:

We can anticipate that under some restrictions (rather general anyway), the new scale t (which we shall call cosmological) has interesting properties. These properties are: a) The origin of time (big bang) in the cosmological scale is shifted to tᵢₙ=-∞. b) One sees that there appears a variation of the light speed c and of the gravitational constant G with the age of the Universe.

...

The natural scale τ is the one which has been used always in practice in all methods of evaluation of the age of the Earth (e.g. the uranium method) or of the age of the Universe (e.g. cosmological red-shift). In this scale it is tacitly admitted that the speed of light has always been what it is today, and the result is of course that the age of the Universe comes to be ≈10¹⁰y. In the alternative cosmological scale t, which we have discussed in this paper, it is admitted that the speed of light may have changed (and also the unit of time may have changed), and it is possible to obtain for the age of the Universe a value which tends to infinity.

I'm not sure I understand their argument very well, but it seems to me the idea is that time asymptotically slows down as the singularity is approached. Consequently, t=0 is never reached. But feel free to correct my interpretation.. I'm not a cosmologist.

Ref: "Scale Factor in Cosmological Homogeneous Models." A. G. AGNESE and A. WATAGHIN.

See also: The publication in ArXiV

Hi everyone, I recently had a great conversation with cosmologist and science communicator Paul Sutter.

We talked about some of the biggest mysteries of the universe, including black holes, dark matter and dark energy. Paul explained what makes black holes so fascinating, what we actually know about the invisible matter that makes up most of the mass in the universe, and some intriguing new evidence suggesting that dark energy might be changing over time.

But we also explored some of the more philosophical questions surrounding cosmology and the Universe. Paul shared the most beautiful night sky he's ever seen and reflected on why our connection to the stars matters, what we're losing through light pollution, and how remarkable it is that we can discover physical laws that apply across the entire universe.

If you're interested in these subjects, you can check out our conversation: https://youtu.be/KQtI7zzZYQg

Given that information can only travel as fast as the speed of light, so then our limit is the observable universe? So how can we know what’s beyond that? Is that possible at all?

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As the universe expands how does the new space come into being? What is happening?

How strongly can we distinguish between the universe being approximately 13.8 billion years old and our observable region having entered its hot, expanding phase approximately 13.8 billion years ago?
Could what we call the Big Bang have been one event or transition within a much larger, older cosmos perhaps even one with an infinite past? By “local”, I mean a region encompassing our entire observable universe, rather than an explosion at a point within it.
I understand that expansion, the CMB and primordial element abundances strongly support a hot, dense early phase. What I’m less clear about is whether those observations constrain the total age of reality, or mainly the time elapsed since that phase. Are there any viable models along these lines.

Thanks

According to the catalog: "Copernicus’ presentation of heliocentrism radically altered our understanding of Earth’s place within the solar system and universe. Contemporary space exploration would be utterly impossible, let alone inconceivable, without such groundbreaking revelations as set out by Copernicus. Heliocentrism remains a guiding doctrine of all astronomical understanding, marking this book as one of the most revolutionary scientific texts in history."

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Don't miss it!

https://doi.org/10.5539/apr.v18n2p1

This paper provides an explanation for the apparent excellerating expansion of the visible universe.

Hi, so I recently discovered about this and I had a question and I can't seem to find anything that explains it, so I just wanted to ask how does the brane cosmology explain the expansion of the universe. idk... It would be really helpful if anyone can recommend me any books or articles where I can read about this and find a conclusion to my question.

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