Tue, 30 Apr 2013 10:00 CDT
© Chukman So
Do atoms of antihydrogen weigh the same as atoms of ordinary hydrogen? Could they even have "negative" weight? To find out, physicists "weighed" antimatter to understand how it interacts with gravity.
When it comes to antimatter, what goes up doesn't necessarily come down. In a new study, physicists weighed antimatter in an effort to determine how this strange cousin of matter interacts with gravity.
Ordinary matter atoms fall down due to the pull of gravity, but the same might not be true of antimatter, which has the same mass as matter, but opposite charge and spin
. Scientists wondered whether antimatter atoms would instead fall up when pulled by gravity, and whether such a thing as antigravity exists.
"In the unlikely event that antimatter falls upward, we'd have to fundamentally revise our view of physics and rethink how the universe works," Joel Fajans, a physicist at the Lawrence Berkeley National Laboratory in California, said in a statement.
Fajans and his colleagues at the Alpha experiment at Switzerland's CERN physics lab made the first experimental measurements of the gravitational mass of antihydrogen
- the antimatter equivalent of hydrogen, made of an antiproton and a positron (the antimatter counterpart to an electron).
Conducting experiments on antimatter atoms is difficult, because when matter and antimatter meet, the two annihilate. Thus, any experimental apparatus that came into contact with the material being studied would be instantly destroyed. Scientists get around this predicament by building traps for antimatter made with magnets, which force antimatter particles to stay in a certain area. As soon as the magnets are turned off, the antimatter falls onto the walls of the trap and eviscerates.
But which direction does it fall toward?