In Brief
  • Dark matter seems to outweigh visible matter roughly six to one, making up about 27% of the universe.
  • Physicists from CERN now believe there's a fifth universal force that rules the behavior of dark matter, and is transmitted by a particle called the dark photon.

The Fifth Force

The universe is shrouded in mystery—a shroud so dark, in fact, that 27 percent of the matter in it is “dark.” Dark matter does not interact with photons and electromagnetic waves, so it’s invisible to our eyes and to every kind of telescope. Basically, it’s the darkness that surrounds every celestial body, and we only know that it’s there because astronomers observe its gravitational pull on everything else.

A working theory is that – in addition to the four fundamental forces that drive the universe: gravity, electromagnetism, and strong and weak nuclear forces – there’s a fifth force that rules the behavior of dark matter. Physicists from CERN now believe that this force is transmitted by a particle called the dark photon.

“To use a metaphor, an otherwise impossible dialogue between two people not speaking the same language (visible and dark matter) can be enabled by a mediator (the dark photon), who understands one language and speaks the other one,” explained Sergei Gninenko of CERN.

The research facility is now launching the NA64 experiment to search for this particle. The equipment focuses a beam of electrons with a known value of initial energy at a detector. Interactions between the electrons and atoms in the detector produce visible photons. If dark photons exist, they will escape the detector and subtract from the initial electron energy, as by the law of conservation of energy.

The Complex Universe

There’s a lot of work to be done by physicists in order to prove that dark photons exist. Results of the experiment must be replicable and, if the scientists find it, another round of research will be pursued to prove its relation to dark matter.

CERN is an organization of physicists and engineers that probe the universe in pursuit of understanding its fundamental structure. Discoveries from these studies could validate or totally destroy everything we currently know.

While dark matter may seem very far away from us and our daily lives, understanding all these mysteries is another step toward understanding ourselves and this complex universe we live in.