A cool way to measure big G

Abstract

On page 518 of this issue, Rosi et al.1 describe an amazing measurement: the gravitational force between a rubidium atom and a 516-kilogram mass, with a relative uncertainty of just 0.015%. Their experiment was aimed at a precise determination of the gravitational constant, which describes the strength of the gravitational pull that bodies exert on each other, and was based on the technique of atom interferometry - a method that takes advantage of the wave nature of cold atoms to precisely measure gravitational acceleration.