Atomic clocks take a step towards redefining the second

A brand new measurement strikes scientists nearer to revamping how we preserve time.

After scientists redefined the unit of mass, the kilogram, in 2019, they set their sights on overhauling the basic unit of time, the second (SN: 5/20/19). Now, comparisons between three atomic clocks mark an necessary step towards that aim.

Because the 1960s, the second has been outlined by atomic clocks made from cesium atoms, which take in and emit gentle at a specific frequency that determines the size of a second. However “there have been a variety of enhancements in atomic clocks since then,” says physicist David Hume of the Nationwide Institute of Requirements and Know-how in Boulder, Colo. Improved timepieces referred to as optical atomic clocks (SN: 2/21/14) might be used to extra exactly outline the second.

However first, scientists should guarantee they absolutely perceive the brand new clocks, for instance by evaluating the frequencies of sunshine from completely different timepieces. Now, scientists with the Boulder Atomic Clock Optical Community, or BACON, have made such comparisons, measuring the ratios of frequencies of three atomic clocks, one made from ytterbium atoms, considered one of strontium atoms and one made with a single electrically charged aluminum atom (SN: 10/5/17). The outcomes are probably the most exact clock comparisons but, with uncertainties lower than a quadrillionth of a %, the researchers report within the March 25 Nature.

As a result of the three clocks had been in several areas — two at NIST and the opposite 1.5 kilometers away on the analysis institute JILA — the crew in contrast the clocks by sending info throughout an optical fiber and thru an open-air link. This capacity to match distant optical atomic clocks is a step towards clock networks that might be used to make exact measurements corresponding to characterizing Earth’s gravity and testing elementary physics.

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