Rahul Rao in Scientific American:
Gravity might be an early subject in introductory physics classes, but that doesn’t mean scientists aren’t still trying to measure it with ever-increasing precision. Now, a group of physicists has done it using the effects of time dilation—the slowing of time caused by increased velocity or gravitational force—on atoms. In a paper published online today (Jan. 13) in the journal Science, the researchers announce that they’ve been able to measure the curvature of space-time.
The experiment is part of an area of science called atom interferometry. It takes advantage of a principle of quantum mechanics: just as a light wave can be represented as a particle, a particle (such as an atom) can be represented as a “wave packet.” And just as light waves can overlap and create interference, so too can matter wave packets.