Dark Matter: Mapping the Universe

At CERN, 3,000 physicists explore the essence of antimatter and investigate how gravity behaves in new “extra dimensions”

Like ancient cartographers mapping the world – filling unexplored regions with sea-serpents and here be dragons – scientists try to map the workings of the universe. But the map keeps changing, billowing outwards. The questions shift, breed, multiply. Why isn’t the universe made of antimatter, rather than matter? What is the dark matter that grips galaxies? 

Dark matter is, in fact, a key focus for thousands of today’s scientists. Solving its mystery would significantly expand our understanding of matter in the universe. Currently, research is taking place both in space and on Earth, and some scientists say they may be close to an answer.

 

A view of the CMS detector that sees the ­particles that collide in the LHC | Photo: CERN

A view of the CMS detector that sees the ­particles that collide in the LHC | Photo: CERN

Elegant theories and extra dimensions

Normal matter – the material that comprises people, but also plants and animals, planets and stars – accounts for only four per cent of the universe. Dark matter, however, makes up around 26 per cent, and exerts a gravitational pull that binds galaxies together. Without dark matter, our galaxies would fly apart.

In April at the European Organization for Nuclear Research (CERN), scientists reported a possible sign of dark matter. The research comes from the Alpha Magnetic Spectrometer (AMS), which is mounted on the International Space Station, and is the most sensitive and powerful particle physics spectrometer ever used in space.  When looking at the cosmic ray flux, AMS scientists found an excess of antimatter. When dark matter particles collide and are annihilated, it is thought they might produce antimatter.

“Over the coming months,” said spokesperson, Samuel Ting, “AMS will be able to tell us conclusively whether these positrons are a signal for dark matter, or whether they have some other origin.”

If they are related to dark matter, this would align with the theory of “super-symmetry”, described by many scientists as an especially “elegant” theory, which suggests that the universe has twice as many particles than the current model suggests, and that the lightest of these particles could be dark matter.

Austrian scientists – like physicist Claudia-Elisabeth Wulz – play a central role in dark matter research at CERN, the leading international laboratory for particle physics. As deputy chair of the CMS Collaboration Board and representative of the Austrian Academy of Science, Wulz works with 3,000 other physicists searching for new physics in the Large Hadron Collider – a huge tunnel a hundred metres underground, which stretches across the border of France and Switzerland. Inside the Large Hadron Collider (LHC), particles are smashed together so that physicists can examine the effects.

Part of Wulz’s role is selecting the most interesting collisions for further analysis, to help us understand the gravitational effects of dark matter.

“Although it sounds like science fiction,” she says, “gravity in new, extra dimensions might be much stronger than we normally experience it in our well-known three-dimensional space.”  String theory predicts at least six extra dimensions, which “may become accessible at the LHC.” For the moment, the LHC is undergoing a major upgrade, allowing it to operate at nearly twice its previous power, and the search for dark matter will continue.

Austria is one of the oldest members of CERN, having joined in 1959, just five years after the laboratory was founded. However, five years ago, Austria’s then-Minister of Science and Research Johannes Hahn announced that Austria would withdraw due to the high costs, equalling a full 70 per cent of Austria’s entire funding for international science research. Heated protest from the scientific community and a petition with 32,000 signatures prompted Chancellor Werner Faymann to overrule the decision, and Austria has continued to be one of the 20 countries involved.

It may have paid off, as the last few years at CERN have been particularly exciting. Last year, to the sound of popping champagne corks, CERN announced the discovery of the Higgs boson, an elementary particle predicted by physicist Peter Higgs in 1964 which explains the way elementary particles get their mass. To find the boson, protons were smashed together in the Large Hadron Collider, mimicking conditions that have not existed since the Big Bang.

Absurd as nature

Austrian physicist Claudia-Elisabeth Wulz explores dark matter at CERN | Photo: Astrid Bartl

Austrian physicist Claudia-Elisabeth Wulz explores dark matter at CERN | Photo: Astrid Bartl

Still, many mysteries wait to be solved. Some physicists argue that we may yet be able to unravel all the main mysteries of the universe in our lifetimes. “Someday,” said American physicist Murray Gell-Mann, who won his Nobel Prize for identifying quarks, “we may actually figure out the fundamental unified theory of the particles and the forces, what I call the ‘fundamental law.’ We may not even be terribly far from it.”

Still, says Gell-Mann, that doesn’t mean there is a “theory of everything” (which scientists sweetly abbreviate to TOE). The fundamental law will be quantum mechanical, he says, and will depend on probabilities, not certainties. A fundamental law could not determine the history of the universe without what Gell-Mann calls “this incredibly long series of accidents.” Chance always plays a part. The future of science is as elusive, surprising – indeed as “absurd”, as physicist Richard Feynman once said – “as Nature herself.”

 

Filling in the map

The map of the universe is constantly changing. Scientists are continually making new, contradictory findings, and rethinking and redrawing the way the universe works. An understanding of dark matter would represent a huge advance in our knowledge. Imagine all the matter in the universe as a map of the world; we would go from knowing only four per cent of the map, to understanding more than a quarter.

Whatever we may or may not discover about dark matter, Wulz urges the importance of pursuing fundamental physics: “No technical progress comes without basic research,” she says, “not to speak of spin-offs from particle physics, such as the World Wide Web or facilities to treat cancer. We need this research as much as we need opera houses or football stadiums. It is part of our humanity.”

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