The most detailed map yet of all dark matter in the universe reveals cosmic voids where the laws of physics seem not to apply

dark matter map
Earth-based telescopes like the Victor M. Blanco Telescope dome in Chile have helped scientists map our universe.

  • Astronomers have created the most comprehensive map yet of all dark matter in the universe.
  • Though invisible, scientists can measure dark matter’s gravity because it pulls galaxies into clumps.
  • The new map indicates dark matter’s gravity may work differently than Einstein’s theory of relativity suggests.
  • See more stories on Insider’s business page.

Astronomers have created the most comprehensive map yet of all the dark matter in the universe.

That’s no easy feat, considering dark matter is invisible. Scientists know this shadowy cousin of regular matter exists, though, because its strong gravitational forces can pull entire galaxies together. Based on observations of its influence, astronomers estimate that dark matter makes up one-quarter of the universe.

The new map is the product of years of work by a group of 400 scientists from seven countries, known as the Dark Energy Survey (DES). They pointed the Victor M. Blanco Telescope in Chile skyward to peek at millions of galaxies bound together by dark matter. The distribution of those galaxies, and the ways in which light from them reaches Earth, can inform astronomers about how much dark matter sits between those galaxies and our planet.

In a series of studies published this week, the team showed that the universe is peppered with giant clusters of galaxies bunched together – regions where dark matter, too, is densely packed. But their map, which covers about one-eighth of the sky as seen from Earth, also documents patches of the universe that are nearly devoid of both dark matter and galaxies. These cluttered and empty areas appear to be connected by interstellar gas in a cosmic web.

“It shows us new parts of the universe that we’ve never seen before. We can really see this cosmic web structure, including these enormous structures called cosmic voids, which are very low-density regions of the universe where there are very few galaxies and less matter,” Niall Jeffrey, a cosmologist at University College London, told the Guardian.

The photo below shows a section of the new map; the voids are in black, while the galaxy clusters are bright orange.

dark matter map
A zoomed-in view of the Dark Energy Survey’s dark matter map.

According to Jeffrey, the new findings suggest that gravity may not work the same way in these voids as it does on Earth, which would mean the standard laws of physics do not apply.

Light from 226 million galaxies

While dark matter is unobservable, the force it exerts on other things in the universe helps scientists detect it.

Dark matter bends light coming toward Earth from other galaxies, a bit like a kaleidoscope. So by measuring the intensity of that distortion, astronomers can calculate how much dark matter sits between us and another galaxy, and how smushed together that dark matter is. If a galaxy’s light is very distorted, it suggests the invisible dark matter obscuring it from view is densely clumped.

dark matter map
The DES dark matter map (in purple) superimposed on an image of the Milky Way galaxy.

So Jeffrey and his team looked at how light from more than 226 million galaxies, both nearby and billions of miles away, was getting distorted.

They used the telescope to capture images of those galaxies for 345 nights between 2013 and 2016, then relied on an artificial-intelligence program to translate those observations into their detailed map of dark matter.

The team collected data on another 413 nights before the survey ended 2019, so DES scientists plan to create an even larger, more detailed dark-matter map using the rest of their observations.

The map suggests Einstein might have been wrong

According to Albert Einstein’s theory of relativity, gravity should have caused chunks of matter in the universe to clump up in a predictable way after the Big Bang some 13 billion years ago.

But according to Jeffrey, the DES map suggests Einstein’s theory may have missed the mark to some degree.

“If you look out into the universe, the matter isn’t as clumpy as expected – there are hints that it is smoother,” Jeffrey told the Guardian.

“It may seem a relatively small thing,” he added, “but if these hints are true, then it may mean there’s something wrong with Einstein’s theory of general relativity, one of the great pillars of physics.”

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A new experiment has broken the known rules of physics, hinting at a mysterious, unknown force that has shaped our universe

The superconducting magnetic storage ring at the Fermilab is 50 feet in diameter.

  • A new study suggests subatomic particles called muons are breaking the laws of physics.
  • This may mean a mysterious force is affecting muons, which would make our understanding of physics incomplete.
  • It could be the same force that’s responsible for dark matter, which shaped the early universe.
  • See more stories on Insider’s business page.

One of the most ubiquitous subatomic particles in the universe, the muon, seems to be misbehaving.

Or at least, it isn’t behaving the way physicists expect. In fact, muons are deviating so much from what the laws of physics suggest that scientists are beginning to think their playbook is either incomplete, or there’s some force in the universe we don’t yet know about.

Muons are like fat electrons: They have a negative charge but are 207 times heavier than electrons. Thanks to their charge and a property known as spin, they act like tiny magnets. So when muons are immersed in another magnetic field, they experience an infinitesimal wobble.

But in a study released this week, physicists at the Fermilab in Illinois reported a discrepancy between how much muons should be wobbling and how much they actually did wobble during a lab experiment.

The difference is substantial enough that many scientists are convinced particles or forces we haven’t yet discovered must be involved. The finding, in other words, offers new evidence that something mysterious has played a role in shaping our universe – something that’s missing from the existing rules of physics.

“In this respect, the new measurement could indeed mark the start of a revolution of our understanding of nature,” Thomas Teubner, a theoretical physicist from the University of Liverpool who was not involved in the research, told Insider.

It’s possible that this unknown phenomenon is also linked to dark matter, the shadowy cousin of matter that was created just after the Big Bang and makes up a quarter of the universe.

Shooting muons in a circle at the speed of light

When cosmic rays penetrate Earth’s atmosphere, they create muons. Several hundred muons strike your head every second. They can penetrate objects like an X-ray does – a few years ago, scientists used muons to discover a hidden chamber in Egypt’s Great Pyramid – but the particles only last for two-millionths of a second. After that, they decay into clusters of lighter particles.

During its brief existence, each muon remains oriented around a single point, in the same way a compass always points north. But when it encounters a magnetic field, a muon’s orientation shifts slightly away from that point. That crucial wobble, known as the g-factor, is what the Fermilab experiment is examining.

brookhaven fermilab magnet
A giant electromagnet starts its 3,200-mile journey from Brookhaven National Laboratory in Long Island, New York, to the Fermilab in Batavia, Illinois, in 2013.

Fermilab is a US Department of Energy project with ties to the University of Chicago that’s devoted to the study of particle physics.

Scientists there can produce muons for study by running a beam of protons super quickly into metal using a particle accelerator. So the researchers behind the new study took these muons and funneled them inside a circular electromagnet 50 feet in diameter. The muons then traveled at nearly the speed of light around the circle more than 1,000 times.

When muons in the machine decay, ultra-sensitive detectors can measure which direction the resulting smaller particles are moving. Physicists can then use that information to calculate where each muon’s fixed point is.

Thousands of people in Batavia, Illinois, welcomed the Muon g-2 magnet (in red and white) to Fermilab in 2013.

It should be possible to calculate the precise amount muons will wobble using the Standard Model of physics, which encompasses everything we know about particles’ behavior. But the Fermilab team found that their muons’ wobble did not match those expectations.

Instead, it was off by one-third of one-millionth of a percent.

That difference may seem mind-bogglingly small, but Teubner said it’s actually “a milestone for particle physics.”

And it’s unlikely to be the result of error: The team found that there’s only a 1 in 40,000 chance the discrepancy in their measurement was due to random chance.

“This is strong evidence that the muon is sensitive to something that is not in our best theory,” Renee Fatemi, one of the Fermilab muon experiment managers, said in a press release.

A 20-year mystery

tess stars first science image
The Transiting Exoplanet Survey Satellite’s snapshot of the Large Magellanic Cloud (right) and the bright star R Doradus (left), August 7, 2018.

This isn’t the first time muons have not behaved in the way science’s best theories would predict.

In 2001, the Brookhaven National Laboratory in New York ran a similar experiment using the same giant electromagnet. Those results also showed that muons’ wobble in the lab deviated from what it should have been. But those findings had a smaller statistical significance than Fermilab’s: There was a 1 in 1,000 chance it could have been a fluke.

Now, the Fermilab results confirm what Brookhaven physicists discovered 20 years ago – and that “has made the discrepancy which was already seen with the old result more intriguing,” Teubner said.

Fermilab is expected to release data from two more similar experiments within the next two years. A fourth experiment is also already underway, and fifth is in the works.

Whatever is influencing muons could have a link to dark matter

cdms dark matter fermilab reidar hahn
Two scientists at the Fermilab work on a detector hunting for dark matter in 2014.

According to Teubner, it’s possible that some force that’s not in the Standard Model of physics could explain the muons’ whack-a-doo wobbles.

That force, he said, may also explain the existence of dark matter, and possibly even dark energy – which plays a key role in accelerating the expansion of the universe.

“Theorists would find it appealing to solve more than one problem at once,” Teubner said.

One hypothesis that could apply to both muons and dark matter, he added, is that muons and all other particles have almost identical partner particles that weakly interact with them. This concept is known as supersymmetry.

But Fermilab’s existing technologies aren’t sensitive enough to test that idea. Plus, Teubner added, it’s could be the case that the mysterious influence on muons isn’t linked to dark matter at all – which would mean the rules of physics are inadequate in more ways than one.

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