What the Euclid Space Telescope Sees

The Euclid Space Telescope has revealed the "first page" of the cosmic atlas it is building. The section of the map of the cosmos being built by Euclid was released on Monday (Oct. 15), and it features tens of millions of stars within the Milky Way and around 14 million distant galaxies beyond our own.


The vast cosmic mosaic was constructed from 260 Euclid observations collected between March 25 and April 8, 2024 and contains 208 gigapixels of data. The region charted is around 500 times as wide as the full moon appears in the sky over Earth.

Perhaps most astoundingly, the mosaic accounts for just 1% of the total survey Euclid will conduct over the next six years as it tracks the shapes, distances and movements of galaxies as far as 10 billion light-years away. Not only will this result in the largest 3D map of the cosmos ever created, but the vast scale of this map will help scientists investigate the mysteries of dark matter and dark energy, sometimes collectively known as the "dark universe."     READ MORE...

Dark Matter Does Not Exist

For centuries, scientists have grappled with the fundamental forces that govern our universe, chief among them being gravity, and more recently, dark matter.

Gravity is the invisible force that attracts objects with mass towards each other, playing a crucial role in shaping the cosmos, from the formation of galaxies to the orbits of planets.

However, as our understanding of the universe has expanded, so too have the mysteries surrounding it.

Dark matter dilemma
One of the most perplexing of these mysteries is the concept of dark matter, a hypothetical form of matter that is believed to make up a significant portion of the universe’s total mass.

Unlike ordinary matter, which we can see and interact with directly, dark matter does not emit, absorb, or reflect light, making it invisible to telescopes and other detecting instruments.  READ MORE...

Disputed Dark Matter Claim

Inside the hall that will house the large scintillator counter. Yemilab is built 1,000 metres underground in an old mine. Credit: Kangsoon Park and Eunkyung Lee





It’s a mystery that has had physicists scratching their heads for more than 20 years. The DAMA/LIBRA experiment at the Gran Sasso National Laboratory (LNGS) near L’Aquila, Italy, has been recording an annual fluctuation of light flashes in its detector that appears to be a sign of dark matter. But no one has been able to definitively replicate the findings.

But beneath a mountain in Jeongseon, South Korea, researchers are scaling up an experiment that could finally lay the controversial dark-matter claim to rest. In June, researchers will finish installing a revamped detector in a brand-new facility called Yemilab. If all goes to plan, the upgraded COSINE-100 experiment will be running by August, says Hyun Su Lee, a physicist at the Institute for Basic Science (IBS) in Daejeon, South Korea.

Dark matter is thought to account for 85% of mass in the Universe, but because it barely interacts with ordinary matter and doesn’t interact at all with light, it is notoriously difficult to observe directly. Several research teams have tried to catch a glimpse of the elusive substance, but only the DAMA/LIBRA experiment has claimed to have seen it for real.     READ MORE...

Ultra Light Particles

Astronomers have a problem. Stars and galaxies dance to an unexpected tune, their motion seemingly governed by six times the matter that can be seen. Scientists believe that the Universe is filled with a form of dark matter that far exceeds the amount of ordinary matter. There’s only one problem: There is no direct evidence for the existence of dark matter.

Over the past 50 years, physicists have tried to detect dark matter, to no avail. Many options have been considered, ranging from subatomic particles to unseen black holes. For the past few decades, the theoretical physics community has favored the idea that dark matter is made of stable particles with a mass somewhere between the mass of a proton and a few thousand times greater.

However, a group of physicists at Fermi National Accelerator Laboratory and the University of Chicago have explored a very different mass range. These scientists are looking for dark matter particles that are trillions or even quadrillion times lighter than the more traditional searches.      READ MORE...

Dark Matter to Visible Light

Explorations in dark matter are advancing with new experimental techniques designed to detect axions, leveraging advanced technology and interdisciplinary collaboration to uncover the secrets of this elusive component of the cosmos.

A ghost is haunting our universe. This has been known in astronomy and cosmology for decades. Observations suggest that about 85% of all the matter in the universe is mysterious and invisible. These two qualities are reflected in its name: dark matter.    READ MORE...

The Universe & Dark Matter

Physicists have long theorized that our universe may not be limited to what we can see. By observing gravitational forces on other galaxies, they've hypothesized the existence of "dark matter," which would be invisible to conventional forms of observation.


Pran Nath, the Matthews Distinguished University Professor of physics at Northeastern University, says that "95% of the universe is dark, is invisible to the eye."


"However, we know that the dark universe is there by [its] gravitational pull on stars," he says. Other than its gravity, dark matter has never seemed to have much effect on the visible universe.    READ MORE...

Dark Matter Hiding in Collider's Particle Jets

A new search for dark matter has turned up empty handed — but, in a silver lining, the effort provided important limits that will help future experiments narrow down the hunt for this elusive substance.

Most astronomers believe that dark matter accounts for 85 percent of all mass in the universe, and that its existence would explain the apparent extra gravity detectable around galaxies and within huge galaxy clusters. However, so far, no one has been able to identify what dark matter is made of.    READ MORE...

Matter in the Universe

Most matter in the universe cannot be seen — but its influence on the largest structures in space can.

Astronomers estimate that roughly 85% of all the matter in the universe is dark matter, meaning only 15% of all matter is normal matter. Accounting for dark energy, the name astronomers give to the accelerated expansion of the universe, dark matter makes up roughly 27% of all the mass energy in the cosmos, according to CERN (the European Organization for Nuclear Research).

Astronomers have a variety of tools to measure the total amount of matter in the universe and compare that to the amount of "normal" (also called "baryonic") matter. The simplest technique is to compare two measurements.

The first measurement is the total amount of light emitted by a large structure, like a galaxy, which astronomers can use to infer that object's mass. The second measurement is the estimated amount of gravity needed to hold the large structure together. 

When astronomers compare these measurements on galaxies and clusters throughout the universe, they get the same result: There simply isn't enough normal, light-emitting matter to account for the amount of gravitational force needed to hold those objects together.

Thus, there must be some form of matter that is not emitting light: dark matter.

Different galaxies have different proportions of dark matter to normal matter. Some galaxies contain almost no dark matter, while others are nearly devoid of normal matter. But measurement after measurement gives the same average result: Roughly 85% of the matter in the universe does not emit or interact with light.  READ MORE...

Neutrinos and Dark Matter

PNNL chemist Isaac Arnquist examines ultra-low radiation copper cables specially created for sensitive physics detection experiments. Credit: Andrea Starr, Pacific Northwest National Laboratory



Ultra-low radiation cables reduce background noise for neutrino and dark matter detectors.

Imagine trying to tune a radio to a single station but instead encountering static noise and interfering signals from your own equipment. That is the challenge facing research teams searching for evidence of extremely rare events that could help understand the origin and nature of matter in the universe. 

It turns out that when you are trying to tune into some of the universe’s weakest signals, it helps to make your instruments very quiet.

Around the world, more than a dozen teams are listening for the pops and electronic sizzle that might mean they have finally tuned into the right channel. These scientists and engineers have gone to extraordinary lengths to shield their experiments from false signals created by cosmic radiation. 

Most such experiments are found in very inaccessible places—such as a mile underground in a nickel mine in Sudbury, Ontario, Canada, or in an abandoned gold mine in Lead, South Dakota—to shield them from naturally radioactive elements on Earth. 

However, one such source of fake signals comes from natural radioactivity in the very electronics that are designed to record potential signals.

Ultra-low radiation cables reduce background noise for neutrino and dark matter detectors.

Imagine trying to tune a radio to a single station but instead encountering static noise and interfering signals from your own equipment. That is the challenge facing research teams searching for evidence of extremely rare events that could help understand the origin and nature of matter in the universe. 

It turns out that when you are trying to tune into some of the universe’s weakest signals, it helps to make your instruments very quiet.

Around the world, more than a dozen teams are listening for the pops and electronic sizzle that might mean they have finally tuned into the right channel. These scientists and engineers have gone to extraordinary lengths to shield their experiments from false signals created by cosmic radiation. 

Most such experiments are found in very inaccessible places—such as a mile underground in a nickel mine in Sudbury, Ontario, Canada, or in an abandoned gold mine in Lead, South Dakota—to shield them from naturally radioactive elements on Earth. 

However, one such source of fake signals comes from natural radioactivity in the very electronics that are designed to record potential signals.  READ MORE...

Blobs of Dark Matter

Dark matter fluctuations in the lens system MG J0414+0534. The whitish blue color represents the gravitationally lensed images observed by ALMA. The calculated distribution of dark matter is shown in orange; brighter regions indicate higher concentrations of dark matter and dark orange regions indicate lower concentrations.  Credit: ALMA (ESO/NAOJ/NRAO), K. T. Inoue et al.

Astronomers Observe Blobs of Dark Matter Down to a Scale of 30,000 Light-Years Across

Dark matter remains mysterious and… well… dark. While we don’t yet have a definite idea of what this cosmic “stuff” is made of, astronomers are learning more about its distribution throughout the Universe. 

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Since we can’t see it directly, observers need to use indirect methods to detect it. One way is through gravitational lensing. Another is by looking for emissions from hydrogen gas associated with small-scale dark matter structures in the Universe.

A group of astronomers led by Kaiki Taro Inoue of Kindai University in Japan used the Atacama Large Millimeter Array in Chile to study a distant gravitational lens system called MG J0414+534. A massive foreground galaxy is bending and distorting the light from a distant quasar that lies some 11 billion light-years away. 

The result is four images of the quasar. When they looked at the data, the team found some strange anomalies in the images. They are actually variations in the distribution of dark matter along the line of sight between us and the quasar. 

The gravitational lens magnified the fluctuations and analysis of the data allowed them to map the fluctuations down to a scale of 30,000 light-years.

What The Blobs of Dark Matter Mean
Throughout the universe, dark matter is associated with massive galaxies and galaxy clusters. However, small-scale clumps and distributions aren’t as well understood. So, astronomers want to find ways to map the smaller concentrations of it. Gravitational lensing provides one way to do that. 

In the case of MG J0414+0534, the positions and shapes of the lensed quasar images look a little strange. They don’t fit the model of gravitational lensing predicted when you plug in the numbers for the galaxy and its associated dark matter component.  READ MORE...

An Alternative Picture of Particle Physics

All of nature springs from a handful of components — the fundamental particles — that interact with one another in only a few different ways. In the 1970s, physicists developed a set of equations describing these particles and interactions. Together, the equations formed a succinct theory now known as the Standard Model of particle physics.

The Standard Model is missing a few puzzle pieces (conspicuously absent are the putative particles that make up dark matter, those that convey the force of gravity, and an explanation for the mass of neutrinos), but it provides an extremely accurate picture of almost all other observed phenomena.

Yet for a framework that encapsulates our best understanding of nature’s fundamental order, the Standard Model still lacks a coherent visualization. Most attempts are too simple, or they ignore important interconnections or are jumbled and overwhelming.

A New Approach
Chris Quigg, a particle physicist at the Fermi National Accelerator Laboratory in Illinois, has been thinking about how to visualize the Standard Model for decades, hoping that a more powerful visual representation would help familiarize people with the known particles of nature and prompt them to think about how these particles might fit into a larger, more complete theoretical framework. 

Quigg’s visual representation shows more of the Standard Model’s underlying order and structure. He calls his scheme the “double simplex” representation, because the left-handed and right-handed particles of nature each form a simplex — a generalization of a triangle. We have adopted Quigg’s scheme and made further modifications.   READ MORE...

Space-Time Distortions

Observing time distortions could show whether Einstein's theory of general relativity accounts for the mysteries of dark matter and dark energy.

Scientists could soon test Einstein's theory of general relativity by measuring the distortion of time.


According to new research published June 22 in the journal Nature Astronomy, the newly proposed method turns the edge of space and time into a vast cosmic lab to investigate if general relativity can account for dark matter  -  a mysterious, invisible form of matter that can only be inferred by its gravitational influence on the universe's visible matter and energy -  as well as the accelerating expansion of the universe due to dark energy. The method is ready to be tested on future surveys of the deep universe, according to the study authors.

General relativity states that gravity is the result of mass warping the fabric of space and time, which Einstein lumped into a four-dimensional entity called space-time. According to relativity, time passes more slowly close to a massive object than it does in a mass-less vacuum. This change in the passing of time is called time distortion.

Since its introduction in 1915, general relativity has been tested extensively and has become our best description of gravity on tremendous scales. But scientists aren't yet sure if it can explain invisible dark matter and dark energy, which together account for around 95% of the energy and matter in the universe.  READ MORE...

Rewriting Laws of the Universe

When we look out at the night sky across vast, cosmic distances using our most sensitive and advanced telescopes, we look back in time. Einstein taught us that light has a finite speed; therefore, it takes light longer to travel to us the further one looks.

Thanks to this, cosmologists have been able to see light dating back to about 14 billion years ago. This light reveals something spectacular and mysterious – the Universe is filled with a sea of energy, waves of tangled electrons and photons in the form of a hot fluid, known as a plasma. We call this plasma the Cosmic Microwave Background (CMB).

We cosmologists have precise theoretical and observational evidence that this plasma underwent gravitational collapse with the aid of an invisible form of matter, called dark matter, forming the first stars and eventually forming the organised superstructure that inhabits the current Universe.

However, a mystery still lurked: the properties of this sea of energy seem to originate from what Einstein called “spooky action-at-a-distance” - objects communicating with each other at instantaneous speeds across ridiculously large distances. This is known as the horizon problem.

In 1981, my colleague, Alan Guth of MIT, proposed an elegant solution to this problem. The idea was to introduce a new player called the inflation field that filled the Universe, and whose energy caused space to expand extremely rapidly. The repulsion that arises due to gravitational effects caused by inflation neatly solves the horizon problem – it makes those regions that we thought to be spookily interacting subject to the weird, but well-confirmed, laws of quantum physics.

The theory of cosmic inflation also provided us with a physical mechanism that answers a question that had long troubled cosmologists: how did the seeds of structure originate in a seemingly featureless primordial Universe over 14 billion years ago?  READ MORE...

Invisible Dark Matter

Some of the tendrils of the cosmic web as visualized by the Evolution and Assembly of Galaxies 

and their Environments (EAGLE) Project. (Image credit: EAGLE Project)

Light produced just 380,000 years after the Big Bang was warped by the universe's dark matter exactly the way Einstein predicted it would be.

Astronomers have made the most detailed map ever of mysterious dark matter using the universe’s very first light, and the "groundbreaking" image has possibly proved Einstein right yet again.


The new image, made using 14 billion-year-old light from the turbulent aftermath of the Big Bang, shows the enormous matter tendrils that formed not long after the universe exploded into being. It turns out the shapes of these tendrils are remarkably similar to those predicted using Einstein's theory of general relativity.

The new result contradicts previous dark matter maps that suggested the cosmic web — the gigantic network of crisscrossing celestial superhighways paved with hydrogen gas and dark matter that spans the universe — is less clumpy than Einstein's theory predicted. The astronomers presented their findings April 11 at the Future Science with CMB x LSS conference at Japan's Yukawa Institute for Theoretical Physics.  READ MORE...

A Second Big Bang

Dark matter, represented as blue light in this Hubble Telescope image of galaxy cluster Cl0024+1654, may have exploded into the universe one month after the Big Bang, new research suggests. (Image credit: European Space Agency, NASA and Jean-Paul Kneib (Observatoire Midi-Pyrénées, France/Caltech, USA))





The Big Bang may have been accompanied by a shadow, "Dark" Big Bang that flooded our cosmos with mysterious dark matter, cosmologists have proposed in a new study. And we may be able to see the evidence for that event by studying ripples in the fabric of space-time.


After the Big Bang, most cosmologists think, the universe underwent a period of rapid, remarkable expansion in its earliest moments, known as inflation. Nobody knows what triggered inflation, but it’s necessary to explain a variety of observations, like the extreme geometrical flatness of the universe at large scales.

Inflation was presumably driven by some exotic quantum field, which is a fundamental entity that soaks all of spacetime. At the end of inflation, that field decayed into a shower of particles and radiation, triggering the "Hot Big Bang" that physicists commonly associate with the beginning of the universe. Those particles would go on to coalesce into the first atoms when the cosmos was around 12 minutes old and — hundreds of millions of years later — begin clumping into stars and galaxies.  READ MORE...

Multiverse Theory

Multiverse theory suggests that our universe, with all its hundreds of billions of galaxies and almost countless stars, spanning tens of billions of light-years, may not be the only one. Instead, there may be an entirely different universe, distantly separated from ours — and another, and another. 

Indeed, there may be an infinity of universes, all with their own laws of physics, their own collections of stars and galaxies (if stars and galaxies can exist in those universes), and maybe even their own intelligent civilizations.

It could be that our universe is just one member of a much grander, much larger multitude of universes: a multiverse.  The concept of the multiverse arises in a few areas of physics (and philosophy), but the most prominent example comes from something called inflation theory. 

Inflation theory describes a hypothetical event that occurred when our universe was very young — less than a second old. In an incredibly brief amount of time, the universe underwent a period of rapid expansion, "inflating" to become many orders of magnitude larger than its previous size, according to NASA.

Inflation of our universe is thought to have ended about 14 billion years ago, said Heling Deng, a cosmologist at Arizona State University and an expert in multiverse theory. "However, inflation does not end everywhere at the same time," Deng told Live Science in an email. "It is possible that as inflation ends in some region, it continues in others."

Thus, while inflation ended in our universe, there may have been other, much more distant regions where inflation continued — and continues even today. Individual universes can "pinch off" of larger inflating, expanding universes, creating an infinite sea of eternal inflation, filled with numerous individual universes.

In this eternal inflation scenario, each universe would emerge with its own laws of physics, its own collection of particles, its own arrangement of forces and its own values of fundamental constants. This might explain why our universe has the properties it does — particularly the properties that are hard to explain with fundamental physics, such as dark matter or the cosmological constant, Deng said.

"If there is a multiverse, then we would have random cosmological constants in different universes, and it is simply a coincidence that the one we have in our universe takes the value that we observed," he said.   READ MORE...

Alternative Theory of Gravity

Radio image of the neutral hydrogen gas in the galaxy AGC 114905. (Mancera Pina et al., MNRAS, 2021)

Out in the dark depths of space, our models of the Universe get messy. A new study looking at the ultra-diffuse dwarf galaxy AGC 114905 has revived a controversial theory (or more accurately a hypothesis) of gravity, and given us more questions than answers about what's making our galaxies tick.

It all starts with dark matter – or in this case, no dark matter. Although most cosmologists agree there's something out there called 'dark matter', causing spiral galaxies to rotate faster than they should, even dark matter doesn't answer all the questions we need it to.

So, it's not a bad idea to look at some alternative options. You know, just in case we are never able to find the stuff.

One alternative hypothesis to dark matter is called Modified Newtonian dynamics (MOND) or Milgromian dynamics framework. This hypothesis – first published in 1983 by physicist Mordehai Milgrom – suggests that we don't need dark matter to fill in the Universe's gravity gaps, if we calculate the gravitational forces experienced by stars in outer galactic regions in a different manner to how Newtonian laws suggest.

To test this idea, which involves working with proportionality to the star's radius or centripetal acceleration, we need to be looking at the speeds of galaxies – specifically weird ones like ultra-diffuse galaxies.

These very faint, ugly ducklings of the galaxy world have a habit of not acting like a galaxy should. For example, some ultra diffuse galaxies seem to be made almost entirely of dark matter, whilst others are almost completely dark matter-less.  READ MORE...

Backwards in Time

A wild new theory suggests there may be another "anti-universe," running backward in time prior to the Big Bang.  The idea assumes that the early universe was small, hot and dense — and so uniform that time looks symmetric going backward and forward.

If true, the new theory means that dark matter isn't so mysterious; it's just a new flavor of a ghostly particle called a neutrino that can only exist in this kind of universe. And the theory implies there would be no need for a period of "inflation" that rapidly expanded the size of the young cosmos soon after the Big Bang.

If true, then future experiments to hunt for gravitational waves, or to pin down the mass of neutrinos, could answer once and for all whether this mirror anti-universe exists.

Preserving symmetry
Physicists have identified a set of fundamental symmetries in nature. The three most important symmetries are: charge (if you flip the charges of all the particles involved in an interaction to their opposite charge, you'll get the same interaction); parity (if you look at the mirror image of an interaction, you get the same result); and time (if you run an interaction backward in time, it looks the same).

Physical interactions obey most of these symmetries most of the time, which means that there are sometimes violations. But physicists have never observed a violation of a combination of all three symmetries at the same time. If you take every single interaction observed in nature and flip the charges, take the mirror image, and run it backward in time, those interactions behave exactly the same.

This fundamental symmetry is given a name: CPT symmetry, for charge (C), parity (P) and time (T).

In a new paper recently accepted for publication in the journal Annals of Physics, scientists propose extending this combined symmetry. Usually this symmetry only applies to interactions — the forces and fields that make up the physics of the cosmos. But perhaps, if this is such an incredibly important symmetry, it applies to the whole entire universe itself. In other words, this idea extends this symmetry from applying to just the "actors" of the universe (forces and fields) to the "stage" itself, the entire physical object of the universe.

Creating dark matter
We live in an expanding universe. This universe is filled with lots of particles doing lots of interesting things, and the evolution of the universe moves forward in time. If we extend the concept of CPT symmetry to our entire cosmos, then our view of the universe can't be the entire picture.

Instead, there must be more. To preserve the CPT symmetry throughout the cosmos, there must be a mirror-image cosmos that balances out our own. This cosmos would have all opposite charges than we have, be flipped in the mirror, and run backward in time. Our universe is just one of a twin. Taken together, the two universes obey CPT symmetry.

The study researchers next asked what the consequences of such a universe would be.  They found many wonderful things.  READ MORE...

Backwards in Time

If the universe has a twin and on that twin time runs backward, then scientists could explain dark matter. (Image credit: MARK GARLICK/SCIENCE PHOTO LIBRARY/Getty Images)

A wild new theory suggests there may be another "anti-universe," running backward in time prior to the Big Bang.

The idea assumes that the early universe was small, hot and dense — and so uniform that time looks symmetric going backward and forward.

If true, the new theory means that dark matter isn't so mysterious; it's just a new flavor of a ghostly particle called a neutrino that can only exist in this kind of universe. And the theory implies there would be no need for a period of "inflation" that rapidly expanded the size of the young cosmos soon after the Big Bang.

If true, then future experiments to hunt for gravitational waves, or to pin down the mass of neutrinos, could answer once and for all whether this mirror anti-universe exists.

Preserving symmetry
Physicists have identified a set of fundamental symmetries in nature. The three most important symmetries are: charge (if you flip the charges of all the particles involved in an interaction to their opposite charge, you'll get the same interaction); parity (if you look at the mirror image of an interaction, you get the same result); and time (if you run an interaction backward in time, it looks the same).

Physical interactions obey most of these symmetries most of the time, which means that there are sometimes violations. But physicists have never observed a violation of a combination of all three symmetries at the same time. If you take every single interaction observed in nature and flip the charges, take the mirror image, and run it backward in time, those interactions behave exactly the same.

This fundamental symmetry is given a name: CPT symmetry, for charge (C), parity (P) and time (T).  READ MORE...

Dark Matter Creates Dark Matter From Regular Matter

An international team of physicists is proposing an addition to dark matter theory. In their paper published in the journal Physical Review Letters, the group is suggesting that dark matter came from regular matter and that dark matter is able to create more dark matter from regular matter.

The existence of a material described as dark matter has been proposed by physicists to explain certain behaviors observed by researchers—the way light bends as it makes its way from far away places to telescopes here on Earth, is just one example. 

But some parts of the theory have yet to be worked out, such as how did the amount of dark matter believed to exist today come into being? The team on this new effort has come up with a theory to answer that question.

The theorists begin by citing prior research which suggests that some amount of dark matter was created as part of the 'thermal bath'—where primordial plasma made of regular matter begat dark matter particles—but not the amount that is believed to exist today. 

They suggest that at some point dark matter particles began making more dark matter particles out of regular particles. And the new dark matter particles were also able to create new dark matter particles out of regular particles.  READ MORE...