The crisis in Cosmology--Solved?

[caltrek]

New Research Suggests that Our Universe Has No Dark Matter
March 15, 2024

Introduction:

(Eurekalert) The current theoretical model for the composition of the universe is that it’s made of ‘normal matter,’ ‘dark energy’ and ‘dark matter.’ A new uOttawa study challenges this.

A University of Ottawa study published today challenges the current model of the universe by showing that, in fact, it has no room for dark matter.

In cosmology, the term “dark matter” describes all that appears not to interact with light or the electromagnetic field, or that can only be explained through gravitational force. We can’t see it, nor do we know what it’s made of, but it helps us understand how galaxies, planets and stars behave.

Rajendra Gupta, a physics professor at the Faculty of Science, used a combination of the covarying coupling constants (CCC) and “tired light” (TL) theories (the CCC+TL model) to reach this conclusion. This model combines two ideas — about how the forces of nature decrease over cosmic time and about light losing energy when it travels a long distance. It’s been tested and has been shown to match up with several observations, such as about how galaxies are spread out and how light from the early universe has evolved.

This discovery challenges the prevailing understanding of the universe, which suggests that roughly 27% of it is composed of dark matter and less than 5% of ordinary matter, remaining being the dark energy.

Read more of the Eurekalert article here: https://www.eurekalert.org/news-releases/1037861

For a technical presentation of the study results as presented in The Astrophysical Journal: https://iopscience.iop.org/article/10.3 ... 57/ad1bc6

[caltrek]

Giant Structure Lurking in Deep Space Challenges Our Understanding of The Universe
by Michele Starr
May 12, 2024

Introduction:

(Science Alert) A colossal structure in the distant Universe is defying our understanding of how the Universe evolved.

In light that has traveled for 6.9 billion years to reach us, astronomers have found a giant, almost perfect ring of galaxies, some 1.3 billion light-years in diameter. It doesn't match any known structure or formation mechanism.

The Big Ring, as the structure has been named, could mean that we need to amend the standard model of cosmology.

The discovery, led by astronomer Alexia Lopez of the University of Central Lancashire, was presented at the 243rd meeting of the American Astronomical Society in January, and is reported in a pre-print paper available at arXiv.

It's the second giant structure discovered by Lopez and her colleagues. The first, called the Giant Arc, is actually in the same part of the sky, at the same distance away. When the arc's discovery was announced in 2021, it puzzled astronomers. The Big Ring only deepens the mystery.

Read more here: https://www.sciencealert.com/giant-str ... universe

[caltrek]

New Research Support Predictions of Modified Gravity Theory as an Alternative to Dark Matter
June 17, 2024

Introduction:

(Eurekalert) Tobias Mistele, a post-doctoral scholar in the Department of Astronomy at Case Western Reserve’s College of Arts and Sciences, pioneered a revolutionary technique using “gravitational lensing” to delve into the enigmatic realm of dark matter. He found that the rotation curves of galaxies remain flat for millions of light years with no end in sight.

Scientists have previously believed that the rotation curves of galaxies must decline the farther out you peer into space.

Traditionally, the behavior of stars within galaxies has puzzled astronomers. According to Newtonian gravity, stars on the outer edges should be slower due to diminished gravitational pull. This was not observed, leading to the inference of dark matter. But even dark matter halos should come to an end, so rotation curves should not remain flat indefinitely.

Mistele’s analysis defies this expectation, providing a startling revelation: the influence of what we call dark matter extends far beyond previous estimates, , stretching at least a million light-years from the galactic center.

Such a long-range effect may indicate that dark matter—as we understand it—might not exist at all.

Read more here: https://www.eurekalert.org/news-releases/1048445

[caltrek]

Tiny Bright Objects Discovered at Dawn of Universe Baffle Scientists
June 28, 2024

Introduction:

(Eurekalert) UNIVERSITY PARK, Pa. — A recent discovery by NASA’s James Webb Space Telescope (JWST) confirmed that luminous, very red objects previously detected in the early universe upend conventional thinking about the origins and evolution of galaxies and their supermassive black holes.

An international team, led by Penn State researchers, using the NIRSpec instrument aboard JWST as part of the RUBIES survey identified three mysterious objects in the early universe, about 600-800 million years after the Big Bang, when the universe was only 5% of its current age. They announced the discovery today (June 27) in Astrophysical Journal Letters.

The team studied spectral measurements, or intensity of different wavelengths of light emitted from the objects. Their analysis found signatures of “old” stars, hundreds of millions of years old, far older than expected in a young universe.

The researchers said they were also surprised to discover signatures of huge supermassive black holes in the same objects, estimating that they are 100 to 1,000 times more massive than the supermassive black hole in our own Milky Way. Neither of these are expected in current models of galaxy growth and supermassive black hole formation, which expect galaxies and their black holes to grow together over billions of years of cosmic history.

“We have confirmed that these appear to be packed with ancient stars — hundreds of millions of years old — in a universe that is only 600-800 million years old. Remarkably, these objects hold the record for the earliest signatures of old starlight,” said Bingjie Wang, a postdoctoral scholar at Penn State and lead author on the paper. “It was totally unexpected to find old stars in a very young universe. The standard models of cosmology and galaxy formation have been incredibly successful, yet, these luminous objects do not quite fit comfortably into those theories.”

Read more here: https://www.eurekalert.org/news-releases/1049884

[caltrek]

Webb Telescope’s Largest Study of Universe Expansion Confirms Challenge to Cosmic Theory
December 9, 2024

Introduction:

(Eurekalert) New observations from the James Webb Space Telescope suggest that a new feature in the universe—not a flaw in telescope measurements—may be behind the decadelong mystery of why the universe is expanding faster today than it did in its infancy billions of years ago.

The new data confirms Hubble Space Telescope measurements of distances between nearby stars and galaxies, offering a crucial cross-check to address the mismatch in measurements of the universe’s mysterious expansion. Known as the Hubble tension, the discrepancy remains unexplained even by the best cosmology models.

“The discrepancy between the observed expansion rate of the universe and the predictions of the standard model suggests that our understanding of the universe may be incomplete. With two NASA flagship telescopes now confirming each other’s findings, we must take this [Hubble tension] problem very seriously—it’s a challenge but also an incredible opportunity to learn more about our universe,’’ said Nobel laureate and lead author Adam Riess, a Bloomberg Distinguished Professor and Thomas J. Barber Professor of Physics and Astronomy at Johns Hopkins University.

Published in The Astrophysical Journal, the research builds on Riess’ Nobel Prize–winning discovery that the universe’s expansion is accelerating owing to a mysterious “dark energy” permeating vast stretches of space between stars and galaxies.

Riess’ team used the largest sample of Webb data collected over its first two years in space to verify the Hubble telescope’s measure of the expansion rate of the universe, a number known as the Hubble constant. They used three different methods to measure distances to galaxies that hosted supernovae, focusing on distances previously gauged by the Hubble telescope and known to produce the most precise “local” measurements of this number. Observations from both telescopes aligned closely, revealing that Hubble’s measurements are accurate and ruling out an inaccuracy large enough to attribute the tension to an error by Hubble.

Read more of the Eurekalert article here: https://www.eurekalert.org/news-releases/1067050

For a technical presentation of the results of the study as published in The Astrophysical Journal: https://iopscience.iop.org/article/10 ... 57/ad8c21

[firestar464]

New Scientist- A new kind of hidden black hole may explain the mystery of dark energy

https://archive.ph/PHqsT

[caltrek]

Does the Universe Behave the Same Way Everywhere? Gravitational Lenses Could Help Us Find Out
February 11, 2025

Introduction:

(Eurekalert) “The cosmological principle is like an ultimate kind of statement of humility,” explains James Adam, astrophysicist at the University of the Western Cape, Cape Town, South Africa, and lead author of the new paper. According to the Cosmological Principle, not only are we not at the center of the Universe, but a true center does not exist. A further assumption, similar to but distinct and independent from homogeneity, is that the Universe is also isotropic, meaning it has no preferred directions. These assumptions underlie the Standard Model of Cosmology, the theoretical framework used to explain the origin, evolution, and current state of the Universe. It is currently the most robust and consistent model, verified by numerous scientific observations, though not yet perfect.

In fact, some recent cosmological observations suggest that, on extremely large scales, there may be anisotropies—variations in the Universe’s structure that challenge the assumption of isotropy. These anomalies have been identified using different methods and include conflicting measurements of the Universe’s expansion rate, studies of the cosmic microwave background radiation, and various inconsistencies in cosmological data. However, these observations are not yet conclusive. To rule out measurement errors, more data must be collected using independent methodologies. If multiple techniques confirm the same anomalies, their existence would become much harder to dismiss.

The new study published in JCAP by Adam and colleagues developed a new methodology to test the Universe’s isotropy using observations from instruments like Euclid. Euclid is an ESA space telescope launched in 2023, which has just begun producing images of the cosmos with unprecedented power, precision, and resolution.

Read more here: https://www.eurekalert.org/news-releases/1072821

caltrek's comment: A universe with anisotropies makes more sense to me than a strictly isotropic universe. Still, the universe is under no obligation to make sense to me.

[caltrek]

'Hidden Galaxies' Could Be Smoking Gun in Universe Riddle
April 9, 2025

Introduction:

(Eurekalert) Astronomers have peered back in time to find what looks like a population of 'hidden' galaxies that could hold the key to unlocking some of the universe's secrets.

If their existence is confirmed it would "effectively break current models of galaxy numbers and evolution".

The possible galaxies may also provide the missing piece of the puzzle for the energy generation in the universe in infrared light.

That's because their combined light would be enough to top-up the energy budget of the universe to the maximum we observe, effectively accounting for all remaining energy emission at these long wavelengths.

Possible evidence of the galaxies' existence was detected on the deepest ever image of the universe at long far-infrared wavelengths, which features almost 2,000 distant galaxies and was created by a team of researchers led by STFC RAL Space and Imperial College London.

Read more here: https://www.eurekalert.org/news-releases/1079968

[caltrek]

I think the following article belongs in this thread in that cosmology should involve not just how the universe initially formed, but also what shaped the universe after its initial moments of formation.

Dwarf Galaxy Clustering Challenges Standard Cold Dark Matter Paradigm
May 21, 2025

Introduction:

(Eurekalert) A new study of diffuse dwarf galaxies is challenging the prevailing galaxy formation model within the standard Cold Dark Matter (CDM) framework, leading to a proposed new model of dark matter.

Under the direction of Prof. WANG Huiyuan from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences, the research team identified for the first time an exceptionally strong clustering pattern in diffuse dwarf galaxies.

The study was published in Nature.

Dwarf galaxies, like all galaxies, sit within a halo of dark matter. These halos formed early in the universe and shaped where galaxies could form.

Nevertheless, not all dark matter halos are the same. Some are more likely to be found in denser regions of the universe than others. This is called "halo bias" and comes in two types—"mass bias," which holds that massive halos cluster more strongly, and "assembly bias," which holds that among halos of the same mass, those with different halo properties exhibit different clustering. For example, the halos formed earlier (old halos) cluster more strongly than those formed later (young halos).

Read more here: https://www.eurekalert.org/news-releases/1084875

[caltrek]

New Measure of the Universe’s Expansion Suggests Resolution of a Conflict
June 3, 2025

Introduction:

(Eurekalert) For the past decade, scientists have been trying to get to the bottom of what seemed like a major inconsistency in the universe.

The universe expands over time, but how fast it’s expanding seemed to differ depending on whether you looked early in the universe’s history or the present day. If true, this would have presented a major problem to the gold-standard model that represents our best understanding of the universe.

But thanks to the new James Webb Space Telescope, scientists from the University of Chicago have been able to take new and better data—suggesting there may be no conflict after all.

“This new evidence is suggesting that our Standard Model of the universe is holding up,” said UChicago Prof. Wendy Freedman, a leading figure in the debate over this rate of expansion, known as the Hubble Constant.

“It doesn’t mean we won’t find things in the future that are inconsistent with the model, but at the moment the Hubble Constant doesn’t seem to be it,” she said.

Read more of the Eurekalert article here: https://www.eurekalert.org/news-releases/1086141

For a presentation of study results as published in The Astrophysical Journal: https://iopscience.iop.org/article/10. ... 57/adce78

[caltrek]

New Theory to Understand the Origins of the Universe
July 15 , 2025

Introduction:

(Eureklaert) A team of scientists led by expert Raúl Jiménez, ICREA researcher at the University of Barcelona’s Institute of Cosmos Sciences (ICCUB), in collaboration with the University of Padua (Italy), has presented a revolutionary theory about the origins of the Universe. The study, published in the journal Physical Review Research, introduces a radical change in the understanding of the first moments after the Big Bang, without relying on the speculative assumptions that physicists have traditionally assumed.

Unravelling the mystery of the origins of the Universe

For decades, cosmologists have worked under the inflationary paradigm, a model that suggests that the Universe expanded extremely rapidly, in a fraction of a second, thus paving the way for everything we observe today. But this model includes too many adjustable parameters—the free parameters—which can be modified. Scientifically, this poses a problem, as it makes it difficult to know whether a model is truly predicting or simply adapting to the data.

In a significant breakthrough, the team has proposed a model in which the early Universe does not require any of these arbitrary parameters. Instead, it begins with a well-established cosmic state called De Sitter space, which is consistent with current observations of dark energy.

Gravitational waves: the key to understanding cosmic structure

The new model does not rely on hypothetical fields or particles such as inflation. It suggests that natural quantum fluctuations in space-time, gravitational waves, were sufficient to seed the small density differences that eventually gave rise to galaxies, stars, and planets. These ripples evolve non-linearly, interacting and generating complexity over time, allowing for verifiable predictions with real data.

“For decades, we have tried to understand the early moments of the Universe using models based on elements we have never observed”, says Raúl Jiménez. “What makes this proposal exciting is its simplicity and verifiability. We are not adding speculative elements, but rather demonstrating that gravity and quantum mechanics may be sufficient to explain how the structure of the cosmos came into being”.

Read more of the Eurekalert article here: https://www.eurekalert.org/news-releases/1091281

For a technical presentation of study results as published in the journal Physical Review Research: https://journals.aps.org/prresearch/abs ... /vfny-pgc2

[caltrek]

Revealing How Matter Affects the Evolution of the Universe
August 17, 2025

Introduction:

(Eureklaert) A University of Queensland researcher has developed a new mathematical model to explain the evolution of the universe which for the first time includes collapsing regions of matter and expanding voids.

Dr Leonardo Giani and a team at UQ’s School of Mathematics and Physics used data from the Dark Energy Spectroscopic Instrument (DESI) which has measurements of the universe to 11 billion light years.

“This new model can change the way physicists and cosmologists look at the universe,” Dr Giani said.

“The standard model mapping the Universe from the Big Bang until today has matter particles of the same size not interacting with each other.

“But in reality, we can see there are stars, black holes, galaxy clusters and empty regions constantly interacting via forces such as gravity not accounted for by the standard model.

Read more here: https://www.eurekalert.org/news-releases/1094989

[caltrek]

The Strongest Evidence for a Universe Before the Big Bang
By Ethan Siegel
September 24 2025

Introduction:

(Big Think) The notion of the Big Bang goes back nearly 100 years, when the first evidence for the expanding Universe appeared. If the Universe is expanding and cooling today, that implies a past that was smaller, denser, and hotter. In our imaginations, we can extrapolate back to arbitrarily small sizes, high densities, and hot temperatures: all the way to a singularity, where all of the Universe’s matter and energy was condensed in a single point. For many decades, these two notions of the Big Bang — of the hot dense state that describes the early Universe and the initial singularity — were inseparable.

But beginning in the 1970s, scientists started identifying some puzzles surrounding the Big Bang, noting several properties of the Universe that weren’t explainable within the context of these two notions simultaneously. When cosmic inflation was first put forth and developed in the early 1980s, it separated the two definitions of the Big Bang, proposing that the early hot, dense state never achieved these singular conditions, but rather that a new, inflationary state preceded it. There really was a Universe before the hot Big Bang, and some very strong evidence from the 21st century truly proves that it’s so.

Although we’re certain that we can describe the very early Universe as being hot, dense, rapidly expanding, and full of matter-and-radiation — i.e., by the hot Big Bang — the question of whether that was truly the beginning of the Universe or not is one that can be answered with evidence. The differences between a Universe that began with a hot Big Bang and a Universe that had an inflationary phase that precedes and sets up the hot Big Bang are subtle, but tremendously important. After all, if we want to know what the very beginning of the Universe was, we need to look for evidence from the Universe itself.

Read more here: https://bigthink.com/starts-with-a-ban ... ig-bang/

[caltrek]

The Standard Cosmological Model Is the Simplest Model of the Universe, But Not The Only One
November 14, 2025

Introduction:

(Universe Today) So if the standard model of cosmology is wrong, what alternative is there?

For the past couple of posts I've been talking about a new study that suggests we've been measuring supernova distances a bit wrong. While these new results could solve the long-standing Hubble tension problem, it does so by overturning the ΛCDM model. Specifically, it would mean that dark energy cannot be due to a cosmological constant that is inherent to the structure of spacetime. What would this mean?

To begin with, much of what we know about the Universe would still hold up. The Big Bang, cosmic expansion, and general relativity are all still valid. The only thing that changes is that the Λ in ΛCDM isn't constant. But while the ΛCDM model has stood the test of time, it's also the simplest cosmological model. Plenty of other models have been proposed, and it's worth looking at a few of them.

One approach is to treat dark energy as a scalar field. Known as quintessence, or the "fifth force," the model proposes that expansion is due to a kind of potential energy. Just as the Big Bang created protons, electrons, and neutrinos, maybe it also created a potential field. The simplest version of quintessence allows for a uniform energy density that is greater or less than the cosmological constant, which is fixed at a value of wq = -1. What this means is that you could tweak the model to fit what we observe.

For example, the amount of matter and dark matter we observe in the cosmos isn't nearly enough to slow down the rate of cosmic expansion. As the Universe expands, the mass density of the Universe decreases, meaning that eventually dark energy dominates cosmic evolution. If you tweak dark energy to be weaker, then there could be enough matter and dark matter to slow down cosmic expansion. The authors of the supernova paper looked at this kind of idea, referring to it as the Flat wCDM model. They found that while it fits the data better than the standard model in some ways, overall it isn't a particularly good match.

Another approach discussed in the article is the variable dark energy model.

Read more here: https://www.universetoday.com/articles ... -only-one

[firestar464]

Our leading theory of dark matter may be wrong, huge new gravity study hints

https://www.livescience.com/physics-mat ... f-research