If science fiction were to be believed, antimatter would be everywhere: from the USS Enterprise’s power source to the giant bomb in Dan Brown’s Angels & Demons. In real life, however, it’s much more elusive. But that may be about to change. ALPHA, an international collaboration of CERNbased researchers, has observed the light spectrum of antimatter for the first time.
Antimatter is identical to matter particles, such as electrons and protons, but has the opposite charge. It is tricky to handle as it annihilates the moment it encounters ordinary matter, leaving only pure energy behind.
ALPHA has been working on combining positrons with antiprotons to produce atoms of antihydrogen, which are slippery customers. But by using a clever trap to capture the antihydrogen particles, they can be studied. “We have designed a very special magnetic trap that relies on the fact that antihydrogen is a little bit magnetic,” said Jeffrey Hangst, the collaboration’s spokesperson.
Atoms are identified by the wavelengths of light they absorb or give off when electrons make a jump between different energy levels within them. The ALPHA collaboration found that, within the limits of the experiment, the spectrum for the simplest electron jump in antihydrogen was identical to ordinary hydrogen. This is an important discovery, because if there were measurable differences between antihydrogen and hydrogen, then the basic principles of particle physics would be broken.
There is plenty more to discover – for example does antimatter fall or up or down under gravity? – as the CERN team continues to explore this remarkable substance.