How World’s Most Precise Clock Could Transform Fundamental Physics

This handout photo provided by NIST shows a strontium atomic clock, one of the world's most accurate time-keeping pieces in the lab of Professor Jun Ye at the University of Colorado, in Boulder. (AFP)

US scientists have measured Albert Einstein's theory of general relativity -- which holds that gravity slows time down -- at the smallest scale ever, demonstrating that clocks tick at different rates when separated by fractions of a millimeter.

Jun Ye, of the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder, told AFP it was "by far" the most precise clock ever built -- and could pave the way for new discoveries in quantum mechanics, the rulebook for the subatomic world.