A pair of experimental atomic clocks based on ytterbium atoms at the National Institute of Standards and Technology has set a record for stability. NIST physicists reported in the August 22, 2013 issue of Science Express that the ytterbium clocks' 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. The clocks would be accurate within a second for a period comparable to the age of the universe.