Antimatter and matter annihilate each other on contact, so how do you go about capturing atoms of antihydrogen for study? The brilliant minds at the CERN particle physics laboratory near Geneva have figured it out.
Antiparticles are the evil opposite of particles, carrying the same mass but the opposite electrical charge. As matter is comprised of particles, so is antimatter comprised of antiparticles. The problem with studying antimatter is the fact that, while folks like to say opposites attract, in the case of antimatter opposites annihilate each other.
Until now the study of antimatter has been limited to charged antiparticles held inside electromagnetic traps. Antimatter atoms, on the other hand, have proven a problem. With no net charge, trapping them wasn't possible. While they do react to magnetic fields, the reaction is generally so weak and the atoms moving so fast that attempts to trap them failed.
Enter the Antihydrogen Laser Physics Apparatus (Alpha) experiment at CERN.
ALPHA team members tried to create sluggish anti-atoms by bouncing antiprotons at -70 °C off much colder positrons at -230 °C. The antiprotons lost energy in the collisions before some finally combined with the positrons to form antihydrogen. The slowest anti-atoms, at a temperature of just -272.5 °C, then became trapped in a powerful cylinder-shaped magnetic field created by superconducting magnets. The field was then turned off so the antihydrogen could annihilate with normal matter, creating particles that silicon detectors picked up.
That's right, CERN is annihilating matter in the name of science. I love that place.
The experiment is far from 100 per cent effective. Mixing 10 million antiprotons and 700 million positrons managed to trap only 39 antihydrogen atoms, but that's 38 more than we had trapped previously, so it's definitely a mark in the win column.
The study of antihydrogen atoms could eventually help solve the mystery of why the universe is comprised of mostly matter, when it should be half matter and half antimatter.
Considering a half antimatter, half matter universe would likely wind up annihilating itself, I'm just thankful things worked out the way they did.
Antihydrogen trapped at long last [NewScientist]