Dark energy—a mysterious force pushing the universe apart at an ever-increasing rate—was discovered 26 years ago, and ever since, scientists have been searching for a new and exotic particle causing the expansion.
Pushing the boundaries of this search, University of California, Berkeley physicists have now built the most precise experiment yet to look for minor deviations from the accepted theory of gravity that could be evidence for such a particle, which theorists have dubbed a chameleon or symmetron. The results are published in the June 11, 2024, issue of Nature Physics.
The experiment, which combines an atom interferometer for precise gravity measurements with an optical lattice to hold the atoms in place, allowed the researchers to immobilize free-falling atoms for seconds instead of milliseconds to look for gravitational effects, besting the current most precise measurement by a factor of five.
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