new cosmology stuff

[billy rubin]

ill look through this for some primary sources when i get a moment

i have not watched it yet

[Icarus]

here is  different perspective about human origins.......

[Recusant]

According to my understanding of projections for the Universe, at some point all other galaxies will have receded beyond our "horizon." That is, it will appear to star-watchers in the far distant future that our galaxy is the full extent of the Universe, surrounded by seemingly endless empty space. However, if the concept in the following article/paper is correct, then it seems to me that instead of a single galaxy observers will see a large gathering of galaxies surrounded by empty space. I see that as slightly less bleak. 

"The Milky Way might be part of an even larger structure than Laniakea" | Phys.org

If you want to pinpoint your place in the universe, start with your cosmic address. You live on Earth->Solar System->Milky Way Galaxy->Local Cluster->Virgo Cluster->Virgo Supercluster->Laniakea. Thanks to new deep sky surveys, astronomers now think all those places are part of an even bigger cosmic structure in the "neighborhood" called The Shapley Concentration.

Astronomers refer to the Shapley Concentration as a "basin of attraction." That's a region loaded with mass that acts as an "attractor." It's a region containing many clusters and groups of galaxies and comprises the greatest concentration of matter in the local universe. All those galaxies, plus dark matter, lend their gravitational influence to the Concentration.

There are many of these basins in the universe, including Laniakea. Astronomers are working to survey them more precisely, which should help provide a more precise map of the largest structures in the universe.

One group, led by astronomer R. Brent Tully of the University of Hawai'i measured the motions of some 56,000 galaxies to understand these basins and their distribution in space. "Our universe is like a giant web, with galaxies lying along filaments and clustering at nodes where gravitational forces pull them together," said Tully.

"Just as water flows within watersheds, galaxies flow within cosmic basins of attraction. The discovery of these larger basins could fundamentally change our understanding of cosmic structure."

[Continues . . .]

The paper is behind a paywall.

Abstract:

The structure in the Universe is believed to have evolved from quantum fluctuations seeded by inflation in the early Universe. These fluctuations lead to density perturbations that grow via gravitational instability into large cosmological structures.

In the linear regime, the growth of a structure is directly coupled to the velocity field because perturbations are amplified by attracting (and accelerating) matter. Surveys of galaxy redshifts and distances allow one to infer the underlying density and velocity fields.

Here, assuming the lambda cold dark matter standard model of cosmology and applying a Hamiltonian Monte Carlo algorithm to the grouped Cosmicflows-4 (CF4) compilation of 38,000 groups of galaxies, the large-scale structure of the Universe is reconstructed out to a redshift corresponding to ~30,000 km s⁻¹.

Our method provides a probabilistic assessment of the domains of gravitational potential minima: basins of attraction (BoA). Earlier Cosmicflows catalogues suggested that the Milky Way Galaxy was associated with a BoA called Laniakea. With the newer CF4 data, there is a slight probabilistic preference for Laniakea to be part of the much larger Shapley BoA. The largest BoA recovered from the CF4 data is associated with the Sloan Great Wall, with a volume within the sample of 15.5 × 10⁶ (h⁻¹ Mpc)³, which is more than twice the size of the second largest Shapley BoA.

[Tank]

Just finished reading this little booklet (96 pages). It covers a range of subjects and really just shows that while there is some evidence to work with we still have no real idea how reality works.

[Recusant]

As I understand it at least some philosophers have concluded that all we can know is a human version of reality. I think it's a fairly close relation to a hypothetical non-humanly perceived reality but then I would, wouldn't I? It seems like we can understand some important stuff about reality, anyway.


Item below could be important if true. The authors seem pretty sure of their findings.

"Astronomers have found the home address for the universe's 'missing' matter" | Phys.org

A new landmark study has pinpointed the location of the universe's "missing" matter, and detected the most distant fast radio burst (FRB) on record. Using FRBs as a guide, astronomers at the Center for Astrophysics | Harvard & Smithsonian (CfA) and Caltech have shown that more than three-quarters of the universe's ordinary matter has been hiding in the thin gas between galaxies, marking a major step forward in understanding how matter interacts and behaves in the universe.

They've used the new data to make the first detailed measurement of ordinary matter distribution across the cosmic web. The research is published in the journal Nature Astronomy.

For decades, scientists have known that at least half of the universe's ordinary, or baryonic matter—composed primarily of protons—was unaccounted for. Previously, astronomers have used techniques including X-ray emission and ultraviolet observations of distant quasars to find hints of vast amounts of this missing mass in the form of very thin, warm gas in between galaxies. Because that matter exists as hot, low-density gas, it was largely invisible to most telescopes, leaving scientists to estimate but not confirm its amount or location.

Enter FRBs—brief, bright radio signals from distant galaxies that scientists only recently showed could measure baryonic matter in the universe, but until now could not find its location. In the new study, researchers analyzed 60 FRBs, ranging from ~11.74 million light years away—FRB20200120E in galaxy M81—to ~9.1 billion light years away—FRB 20230521B, the most distant FRB on record. This allowed them to pin down the missing matter to the space between galaxies, or the intergalactic medium (IGM).

"The decades-old 'missing baryon problem' was never about whether the matter existed," said Liam Connor, CfA astronomer and lead author of the new study. "It was always: Where is it? Now, thanks to FRBs, we know: three-quarters of it is floating between galaxies in the cosmic web." In other words, scientists now know the home address of the "missing" matter.

By measuring how much each FRB signal was slowed down as it passed through space, Connor and his team tracked the gas along its journey. "FRBs act as cosmic flashlights," Connor, who is also an assistant professor of astronomy at Harvard, said. "They shine through the fog of the intergalactic medium, and by precisely measuring how the light slows down, we can weigh that fog, even when it's too faint to see."

[Continues . . .]

The paper is behind a paywall. There is a preprint version but I think I saw some difference just in the abstract. Abstract quoted below more or less as published.

Abstract:

Approximately half of the Universe's dark matter resides in collapsed halos; significantly less than half of the baryonic matter (protons and neutrons) remains confined to halos. A small fraction of baryons are in stars and the interstellar medium within galaxies. The majority are diffuse (<10⁻³ cm⁻³) and ionized (neutral fraction <10⁻⁴), located in the intergalactic medium (IGM) and in the halos of galaxy clusters, groups and galaxies.

This diffuse ionized gas is notoriously difficult to measure, but has wide implications for galaxy formation, astrophysical feedback and precision cosmology. Recently, the dispersion of extragalactic fast radio bursts (FRBs) has been used to measure the total content of cosmic baryons.

Here we present a large cosmological sample of FRB sources localized to their host galaxies. We have robustly partitioned the missing baryons into the IGM, galaxy clusters and galaxies, providing a late-Universe measurement of the cosmic baryon abundance, Ω_bh₇₀ = 0.051±0.006 where Ω_b is the baryon density parameter and h₇₀ is the scaled Hubble constant.

Our results indicate efficient feedback processes that can deplete galaxy halos and enrich the IGM (total baryon fraction in the IGM is f_IGM = 0.76±0.10), agreeing with the baryon-rich cosmic web scenario seen in cosmological simulations. Our results may reduce the 'S₈ tension' in cosmology, as strong feedback leads to suppression of the matter power spectrum.

[Tank]

That looks really interesting! So in effect dark matter is simply previously undetectable normal matter?

I'd like to see how they square this away with spiral galaxy rotation behaviour which was the first indicator of 'missing' matter.

[Recusant]

I believe the "missing baryon problem" is not the same as dark matter. In the abstract they talk about both dark matter and baryonic matter and refer to the "S₈ tension".

[Tank]

An interesting link. Thank you.

[Recusant]

It's more interesting when contradictory hypotheses are available. The "open Universe" had seemed fairly well established but there is a new paper that attempts to revive the closed Universe. The article says we may get a test of the hypothesis, so something to look forward to maybe.

"If Dark Energy is Decreasing, is the Big Crunch Back on the Menu?" | Universe Today

For generations, humans have gazed at the stars and wondered about the ultimate fate of the Universe. Will it expand forever into the cold emptiness, or meet a more dramatic end? A new study published by physicists from Cornell University, Shanghai Jiao Tong University, and other institutions suggests we may finally have an answer, and it's surprisingly specific.

Using data from a number of astronomical surveys including the Dark Energy Survey and the Dark Energy Spectroscopic Instrument, the researchers have developed a model that predicts our Universe will end in a "Big Crunch" in approximately 33.3 billion years. Since the Universe is currently 13.8 billion years old, this gives us roughly 20 billion years before the curtain falls!

Think of it like a great big rubber band. Initially, the Universe expands as this "rubber band" stretches. But eventually, the elastic force becomes stronger than the expansion, causing everything to snap back together. According to the new model, the Universe continues expanding but at a gradually slowing rate until reaching maximum size, about 69% larger than today, in roughly 7 billion years. Then gradual contraction begins as gravitational forces and the negative cosmological constant take over, leading to rapid collapse in the final moments.

It's important to note that this prediction comes with significant uncertainty. The researchers acknowledge their model has large margins of error due to limited observational data. The negative cosmological constant that drives their prediction remains highly speculative, and alternative scenarios including eternal expansion are still possible.

What makes this research particularly exciting isn't just the prediction, but that we may soon be able to test it. Several major astronomical projects launching in the coming years will provide much more precise measurements of dark energy's behaviour, potentially confirming, refining, or ruling out the Big Crunch scenario entirely, once and for all.

[Continues . . .]

A preprint version of the paper is available.

"The Lifespan of our Universe" | arXiv

Abstract:

The Dark Energy Survey (DES) and the Dark Energy Spectroscopic Instrument (DESI) measurements claim that the dark energy equation of state w≠−1. This observation can be explained by the axion Dark Energy (aDE) model of an ultralight axion plus a cosmological constant Λ. Despite a relatively large degeneracy, there is a high probability that Λ<0. This negative Λ leads the universe to end in a big crunch. Using the best-fit values of the model as a benchmark, we find the lifespan of our universe to be 33 billion years.

[Ecurb Noselrub]

Since we will not be here in 33 billion years (except as scattered photons, perhaps), I suggest that we celebrate the Big Crunch now with a Big Brunch, with lots of crunchy foods, and Bloody Marys with celery sticks to provide a crunch with our drinks. Americans will celebrate anything.

[Recusant]

Since we will not be here in 33 billion years (except as scattered photons, perhaps), I suggest that we celebrate the Big Crunch now with a Big Brunch, with lots of crunchy foods, and Bloody Marys with celery sticks to provide a crunch with our drinks. Americans will celebrate anything.

I think that's a brilliant idea. Inspired even.

There is the minor detail that observations show the expansion of the Universe to be accelerating. We're talking about deep time though. As far as I know there's no evidence that the expansion can only accelerate. Perhaps it's possible that in several billion years the expansion will slow. After a few billion more years the Universe begins to contract and eventually it's Crunch time.   

[Dark Lightning]

Cosmology is an area of physics where there is little enough knowledge that physicists can still run wild.

[zorkan]

Cosmology is an area of physics where there is little enough knowledge that physicists can still run wild.

Quote: The cosmos is a term that generally refers to the universe, often with the connotation of it being an orderly or harmonious system. It can be used in both scientific and philosophical contexts to describe the totality of existence."

Except that it isn't an orderly harmonious system.
Look into the night sky and you could be excused for thinking it's all quiet up there.
Not so.
It works off entropy which means it is destroying itself.
Life is only allowed to exist on this lump of space rock because either it helps to increase the entropy or it doesn't interfere with the process.

[GreenBlaze]

I am not an expert in this area. When I was an undergraduate at university I myself was drawn to study a module called Creation, Science and Faith today in my degree course of religious studies major/communications minor.

During my studies I read  such works from academics such as physicist Gerald L Schroeder's timeless work before this discussion became more topical.

I formed the view that the creation story which applies to the three Abrahamic faiths was not at odds with the Big Bang theories/Cosmic Inflation. As the world was being created each day it was expanding and inflating and today it dilates. I am a spiritual person as well and do not overlook science.

I thought that I would update you about the latest research that the Big Bang Theory and Cosmic Inflation is not at odds with their being a Creator. I have quoted from an astrophysics magazine below and will link to the magazine.

Quoting  a few quotes from a astrophysics magazine-

"For many, there's something very appealing about the Big Bang Theory, quite apart from its scientific veracity. With its image of a single, dramatic moment of creation, it conforms to earlier mythological and religious accounts"

"While an expanding universe is consistent is consistent with the Big Bang Theory it doesn't necessarily require it"

"Yet the Big Bang prevailed in the end, and the steady state picture fell by the way side. Thanks to further observational evidence"

"Scientists found it impossible to reconcile this with the idea that the universe has always been expanding at the relatively slow rate we observe today. Instead they had to assume a very brief period of Cosmic Inflation during the universe grew at a truly enormous rate"


https://www.amazon.co.uk/dp/B0CKKNDBVN?ref=ppx_yo2ov_dt_b_fed_asin_title

[billy rubin]

are you familiar with lastthursdayism, greenblaze?