ETH Zurich Creates 2.1-km/s Muonium Beam to Test Einstein's Gravity Theory

1 articles · Updated · The Brighter Side of News · Sep 16

Physicists at ETH Zurich and PSI produced a narrow Muonium beam in vacuum, clearing a key hurdle to directly measure how a second-generation particle responds to gravity.
Superfluid helium cooled to about 0.2 kelvin acted as an "atomic cannon," ejecting newly formed muonium atoms upward at roughly 2.1 kilometers per second with a much tighter spread of speeds and directions.
Muonium is attractive for the test because its mass is dominated by a muon yet it is electrically neutral, but the muon's 2.2-microsecond lifetime has long made controlled gravity measurements impractical.
The team has not measured muonium's fall yet; it plans to send the beam through an interferometer, where gravity should shift the interference pattern enough to infer acceleration.
Projected PSI beam conditions suggest the setup could reach about 1% precision after 100 days, extending equivalence-principle tests beyond ordinary matter and antimatter if successful.