New atomic clock sensitive to altitude change of just 2 cm

Los Angeles Times : The connection between time and gravity was made 100 years ago by Albert Einstein. As ever more precise clocks have been developed, researchers have been able to demonstrate the effects of time dilation by comparing the speed of clocks located at different altitudes—in satellites separated by miles, in an airplane and on the ground, on top of a mountain and at sea level, and even just one foot apart. Now, Jun Ye of JILA and his colleagues have developed an atomic clock sensitive enough to show the effect of gravity when the clock is moved just 2 cm up or down. The new clock, which is a version of an optical lattice , uses a laser to measure the movement of an electron in orbit around a strontium nucleus. To improve on previous optical lattice clocks, Ye’s team used highly sensitive thermometers and one of the most stable lasers available. They also were able to reduce the disruptive effects of the laser on the electron. The result is a clock three times more sensitive than the previous best clock and several orders of magnitude more sensitive than the world’s official time-keeping atomic clock.