A pair of experimental atomic clocks based on ytterbium
atoms at the National Institute of Standards and Technology (NIST) has set a
new record for stability. The clocks act like 21st-century pendulums or
metronomes that could swing back and forth with perfect timing for a period
comparable to the age of the universe.
NIST physicists report in the Aug. 22 issue of Science
Express that the ytterbium clocks' tick is more stable than any other atomic
clock.* Stability can be thought of as how precisely the duration of each tick
matches every other tick. The ytterbium clock ticks are stable to within less
than two parts in 1 quintillion (1 followed by 18 zeros), roughly 10 times
better than the previous best published results for other atomic clocks.