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. But the new atomic clock at NIST, described in the Science study, uses a different element: Ytterbium, atomic number 70. Optical light -- specifically, yellow light from a laser with a wavelength of 578 nanometers -- is used to excite the electrons of ytterbium atoms. The current gold standard for time is the cesium clock, a type of atomic clock that an international body of experts has used to define what is the unit of one second: About 9.19 billion oscillations. Whereas scientists talk about billions of oscillations per second in the cesium clock, oscillations per second in the ytterbium clock approach one quadrillion per second, Ludlow said. Along the way, NIST scientists have made several improvements to both clocks, including the development of an ultra-low-noise laser used to excite the atoms, and the discovery of a method to cancel disruptive effects caused by collisions between atoms. The ytterbium clocks' stability record is different from the performance levels previously publicized for NIST-F1, which is traceable to the international system of units, and NIST experimental optical clocks based on single ions, such as the aluminum quantum logic clock or the mercury ion clock. NIST scientists plan to measure the accuracy of the ytterbium clocks in the near future, and the accuracy of other high performance optical atomic clocks is under study at NIST and JILA. The research is funded in part by the Defense Advanced Research Projects Agency and the National Aeronautics and Space Administration (NASA).
– A new timepiece the size of a dining-room table is being hailed as perhaps the world's most precise: It's "like measuring time over a hundred years to a precision of several nanoseconds," says Andrew Ludlow, co-author of a study behind what's being called the ytterbium optical lattice clock. Until now, the standard for time precision in the US has been a cesium-based clock. Some 9.19 billion oscillations of its electromagnetic signal defines a second. But the ytterbium clock oscillates about a quadrillion times per second, allowing observers to "divide time into finer and finer intervals," Ludlow notes. Those intervals are extremely regular; indeed, two of the clocks have set a record for stability, Science Daily reports. Their timing would be perfect for about as long as the universe has existed. Experts must measure the cesium clock across five days for the most precise readings, whereas the ytterbium clock requires just a second to offer the same level of precision. Why would we ever need such a thing? It could mean better GPS, for example: Because the navigation systems are in space, their time perception isn't quite the same as ours on Earth. Scientists could better correct for that using a more precise clock, CNN notes.