— Gravity may be the force we're most familiar with, but it's also the one we understand with the least accuracy. Now, a quantum mechanical technique could help pin down the strength of gravity more precisely.
Newton's gravitational constant, G, describes the strength of attraction between masses. But traditional methods that rely on measuring how far small masses are pulled by the gravitational force of larger masses nearby only provide relatively rough estimates of its value.
Now, Mark Kasevich of Stanford University in Palo Alto, California, US, and colleagues have used a quantum mechanical technique called interferometry to home in on G.
Using an interferometer, the team split a beam of caesium atoms into two. The beams were sent along different paths and then recombined to produce a pattern of light and dark interference fringes.
The team found that placing a 540 kilogram lead weight near the beams affects their path and shifts the final interference pattern. From this shift, they calculated a value for G, which matched that found by traditional methods.
So far, their results are no more precise than those methods, but they believe that future measurements with the technique will find the most accurate value for the constant yet.
"We're seeing the gravity field in a purely quantum mechanical way, so we're free of the errors that limit the accuracy of traditional methods," Kasevich told New Scientist.
Journal reference: Science (vol 315, p 74)