ALPHA experiment
A photo of the ALPHA experimental apparatus. For the first time scientists will be able to study whole atoms of antimatter, which could offer insight into why the universe looks the way it does. CERN

One of the big questions physicists have been tackling for decades is why anything exists at all. A group of European scientists might get us a step closer to an answer.

The key is studying antimatter. Antimatter is just like normal matter, except that the charges of the constituent particles are reversed. When antimatter and matter touch, they annihilate each other and turn into energy.

There are two ways to make antimatter; one is in particle accelerators and the other is in some types of radioactive decay. (The latter is used in positron emission tomography, or PET scans, with the positron being the antimatter cousin of the electron).

But to study antimatter closely you need to get whole atoms of it, and to do that you have to get positrons and antiprotons to come together. That's difficult because the antiprotons and positrons coming out of a particle accelerator are moving so fast.

A team led by led by Professor Mike Charlton, Dr Niels Madsen and Dr Dirk Peter van der Werf at Swansea University and the University of Liverpool under Professor Paul Nolan built a set of magnetic traps, using superconducting magnets cooled to temperatures near absolute zero. The experiment, called ALPHA, for Anti-hydrogen Laser PHysics Apparatus, aims to capture antiprotons and positrons and slow them down enough so that they become antimatter versions of hydrogen, or antihydrogen.

Charlton said that by getting a good look at the properties of antihydrogen, his team can test the concept of matter-antimatter symmetry. That principle says that antimatter should, absent anything else, look and behave just like normal matter.

But that leaves a problem, Charlton said, in an email. If roughly equal amounts of matter and antimatter were formed at the beginning of the universe, it should all have been turned into energy. Almost all of the matter that is out there (and down here) making up galaxies, stars and planets was annihilated by antimatter just after the Big Bang. But we have no idea why so much matter was left over and why all the antimatter seems to have disappeared.

If it turns out that antihydrogen is different in some fundamental way, then that would go some way towards explaining why, after the beginning, there was any matter left over - and why there is something rather than nothing.