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Down goes antimatter! Gravity's effect on matter's elusive twin is revealed

An artist's rendering of antihydrogen atoms falling out the bottom of the ALPHA-g magnetic trap.

An artist's rendering of antihydrogen atoms falling out the bottom of the ALPHA-g magnetic trap.

September 27, 2023

Landmark CERN experiment answers longstanding question of whether antimatter and matter are gravitationally attracted or repelled.

If you dropped some antimatter, would it fall down or up? Scientists now know the definitive answer: down. That is, if you can somehow prevent it from exploding into pure energy long enough to see where it goes.

A scientific paper describing the landmark experiment behind that conclusion is published today in the journal Nature and comes from the international Antihydrogen Laser Physics Apparatus (ALPHA) collaboration at the European Organization for Nuclear Research (CERN) in Switzerland. The ALPHA collaboration's unique, painstaking experiment has answered the longstanding fundamental question about whether antimatter is gravitationally attracted or repelled by regular matter by observing the downward path taken by individual atoms of antihydrogen. Their work also provides a key piece in one of the most immense unsolved puzzles in science — why is there so little antimatter in the observable universe?

CERN's ALPHA collaboration is supported by more than a dozen countries and private institutions, including the U.S. through the joint U.S. National Science Foundation/Department of Energy Partnership in Basic Plasma Science and Engineering program.

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