BERKELEY — While airplane and rocket experiments have proved that gravity makes clocks tick more slowly — a central prediction of Albert Einstein's general theory of relativity — a new experiment in an atom interferometer measures this slowdown 10,000 times more accurately than before, and finds it to be exactly what Einstein predicted.

Precision timekeeping.

Far from merely theoretical, the results have implications for Earth's global positioning satellite system, for precision timekeeping and for gravitational wave detectors, Müller said.

Freefall

During the approximately 0.3 seconds of freefall, the matter waves on the higher route feel that a little more time elapsed: just 2x10^-20 seconds compared to the lower route. But because of the sheer magnitude of the Compton frequency, Müller said, they oscillated about a million times more often. Since the atom interferometer could measure the difference to within a thousandth of an oscillation, the experiment produced a 9-digit accuracy. This corresponds to measuring the time difference to 10^-28 seconds.