Feb 18, 2010
New precision for relativity’s gravitational redshift
General relativity states that clocks in an accelerated-reference frame run slower than stationary ones. This principle is used often in syncing clocks on Earth with those on satellites or planes, but the time difference has never been measured more accurately than five decimal places; more accurate measurements would help us better understand space-time curvature and develop a theory of quantum gravity. A group of scientists that includes Energy Secretary Steven Chu recognized that an atom in a quantum superposition simultaneously travels two paths at slightly different elevations, and therefore experience slightly different gravitational effects. This let them measure the relativistic effects out to nine decimal places using data they had apparently generated over a decade ago.
General relativity states that an object in an accelerated frame experiences time more slowly than a stationary object. This effect is also generated by gravity, which is essentially an accelerated frame—being on Earth and in Earth’s gravitational pull of 9.8 meters/second/second is the same as being in a rocket in space traveling 9.8 meters/second/second. Time passes more slowly, or dilates, in these frames, an effect known as gravitational redshift.