World's most accurate clock

physorg.com reports: [edited]

An atomic clock that uses an aluminum atom to apply the logic of computers to the peculiarities of the quantum world now rivals the world's most accurate clock, based on a single mercury atom. Both clocks are at least 10 times more accurate than the current U.S. time standard.

The measurements were made in a yearlong comparison of the two next-generation clocks, both designed and built at the Commerce Department's National Institute of Standards and Technology (NIST). The clocks were compared with record precision, allowing scientists to measure the relative frequencies of the two clocks to 17 digits — the most accurate measurement of this type ever made.

The comparison produced the most precise results yet in the worldwide quest to determine whether some of the fundamental constants that describe the universe are changing slightly over time, a hot research question that may alter basic models of the cosmos.

The aluminum and mercury clocks are both based on natural vibrations in ions and would neither gain nor lose one second in over 1 billion years — compared to about 80 million years for NIST-F1, the U.S. time standard based on neutral cesium atoms.
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