Dark matter touches known matter

physics: The mysterious anti-world

Graz. Every science fiction fan knows that huge amounts of energy can be obtained from antimatter. Using a warp drive, the "Enterprise" travels through the galaxy at faster than light speed. Much of it is pure fiction, but it does exist, antimatter - the enigmatic reflection of matter. At the Cern nuclear research center, physicists chase antiparticles through an accelerator to measure their properties. Michael Doser, spokesman for the Aegis experiment at CERN, is one of them. At the Fifteen Seconds Festival in Graz, the Austrian physicist spoke to the Wiener Zeitung about the mysterious anti-world.

"Wiener Zeitung": Only about four percent of the universe consists of known matter. What about the antimatter and what about the rest?

Michael Doser: The four percent come in two forms: matter and antimatter. Like image and mirror image with reversed signs. Electrons that are negatively charged are positive in antimatter. It is the other way around with protons. You can also build atoms from antiprotons and anti-electrons - anti-hydrogen, for example. But the light that an anti-hydrogen emits and the light that emits hydrogen are identical. The rest are dark matter and dark energy. But we don't know what it is. Dark matter could also be particles. If so, there would have to be anti-dark matter particles as well. Dark energy is completely different again. However, there are indirect indications of their existence.

How can antimatter be detected?

Antimatter arises regularly and everywhere - also in our body. But as soon as it hits matter, it is immediately destroyed. Because the moment an anti-electron meets an electron, they destroy each other. It's like a tango de la muerte: the particles find each other and commit a fatal trade in the process. They are getting closer to each other. As soon as they are touched, they destroy each other. This creates two flashes of light that can be measured.

Still can they be made?

We produce them at the Cern nuclear research center through collisions. The trick is to shoot one particle at another. If the energy is high enough, a particle and antiparticle are created - for example a proton and an antiproton. Since they have different charges, I can pull them apart in electric fields. The antiparticles are packed in a vacuum. As long as they are there, they persist.

At Cern they are doing an experiment called Aegis, in particular to measure the gravity of antiparticles. How about gravity?