Almost everything is missing. And a team of physicists is trying to find all of it. The universe as we know it includes about a tenth of the total stuff that's out there. The rest? Missing. Invisible. Undetectable, except through the effects of its gravity on the fraction of stuff that we can see. Researchers call that missing stuff the dark sector — the class of energetic and massive particles that seemingly must exist out there somewhere but that don't interact with luminous matter (the stuff we're made of, along with everything we can see) in any way we can detect.
Physicists, hunting the Dark Photon, will blast a diamond with antimatter
There's a new project at the National Institute for Nuclear Physics in Italy that's going to try to unlock all that dark stuff using the theoretical dark photon (the dark-sector version of regular light-carrying photons) as the key. And if they actually find the dark photon, it will provide evidence for the universe's fifth force — which would be huge news in physics. According to a report in The Guardian, Italian researchers plan to bombard a diamond wafer with a beam of antimatter particles called positrons, which are the antimatter versions of electrons. Under normal circumstances, positrons and electrons that smash into each other annihilate each other, producing a pair of regular photons.
If that happens, the researchers expect to be able to confirm the existence of the dark photon, and measure its mass. (Unlike regular photons, dark photons have mass, according to The Guardian.) That would be evidence of not just a new particle but also an entirely new force. In the luminous universe, there are four forces. Electromagnetism carries light energy and binds atoms to other atoms. (As The Guardian noted, it's the reason you don't fall through your chair.) The strong force holds the particles inside atoms together.
The weak force causes atoms to fall apart and decay. And gravity, the fourth force we can detect, pins you to the Earth and governs the movements of the cosmos. If dark photons exist, The Guardian reported, then they would be the manifestation of a fifth force entirely — one not present in our prevailing model of the universe: dark electromagnetism. If one turns up in Padme (and that's a big if; past hunts for dark photons have turned up nada), then it will really be time to rewrite the physics textbooks.