NIST Ion Clock Sets New Record for Most Accurate Clock in the World

There’s a new record holder for the most accurate clock in the world. Researchers at the National Institute of Standards and Technology (NIST) have improved their atomic clock based on a trapped aluminum ion. Part of the latest wave of optical atomic clocks, it can perform timekeeping with 19 decimal places of accuracy.

Optical clocks are typically evaluated on two levels — accuracy (how close a clock comes to measuring the ideal “true” time, also known as systematic uncertainty) and stability (how efficiently a clock can measure time, related to statistical uncertainty). This new record in accuracy comes out of 20 years of continuous improvement of the aluminum ion clock. Beyond its world-best accuracy, 41% greater than the previous record, this new clock is also 2.6 times more stable than any other ion clock. Reaching these levels has meant carefully improving every aspect of the clock, from the laser to the trap and the vacuum chamber.

The team published its results in Physical Review Letters.

“It’s exciting to work on the most accurate clock ever,” said Mason Marshall, NIST researcher and first author on the paper. “At NIST we get to carry out these long-term plans in precision measurement that can push the field of physics and our understanding of the world around us.”

Indulge me in a rant. If we're going to redefine the second because of advancements in measuring sensitivity, doesn't this become a good time to reconsider the SI structure?

Bad approximations of distances in the 18th century brought us the metric system. With the sort of precision we now have, not to mention the need for nongeocentric units as space increasing becomes a field of research, why are we using a flawed system based on guesses from a few guys in France during The Enlightenment?

I've no issue with shorthand like AUs or light-years for large distances, but it feels we should have the basic tenets of the universe as the basis. Like, the light-nanosecond for distance on the human scale (it's about 11.8 inches or 29.98cm) and then reconfigure the system from first principles.

I'm not saying we should throw out measuring systems each time they get more precise, but a lot of cruft is grandfathered in to what we currently use. We can't just go for further precision and then shrug and say "well, nothing we can do about it."