Antimatter falls down, just like ordinary matter

Gravity pulls antimatter down just like ordinary matter, a new experiment shows. The finding won’t shock many physicists. But it does put a damper on some offbeat theories that, in order to solve some of cosmology’s biggest mysteries, posit that gravity pushes rather than pulls on antimatter—so that the stuff is subject to “antigravity.” “I’m not surprised,” says Alan Kostelecky, a theoretical physicist at Indiana University Bloomington. “On the other hand, this is the kind of thing people take for granted, and such things need to checked.” Gabriel Chardin, a cosmologist with CNRS, France’s national research agency, says, “It’s a beautiful experiment by outstanding people” and “a blow” to speculative theories that assume antimatter experiences antigravity—but not yet a fatal wound. According to the so-called equivalence principle, in a gravitational field all objects fall at the same rate regardless of what they’re made of. Galileo Galilei demonstrated the principle by rolling balls of different materials down a small ramp (not, as legend has it, by dropping them from the Leaning Tower of Pisa). Starting from the principle, Albert Einstein deduced that gravity arises as massive objects warp space and time, a foundation of his 1915 general theory of relativity. Until now, however, nobody had tested whether the equivalence principle holds for matter and antimatter. To find out, physicists working with the Antihydrogen Laser ...
Source: ScienceNOW - Category: Science Source Type: news