We May Have A New Definition Of The Second By 2030


It's time to alter the way we calculate time. Or at least that's what researchers have suggested in a resolution draught for the next 27th General Conference on Weights and Measures, which will take place later this year. We might have a new definition of the second, the most fundamental unit of time, thanks to ultra-precise atomic clocks.

The second was described as "the length of 9,192,631,770 radiation periods related to the transition between the two hyperfine levels of the ground state of the cesium 133 atom" back in 1967. This was improved in 2018, although it still relied on the cesium-133 atom's hyperfine transition.

This definition has been useful to humanity for many years, but advances in optical atomic clocks have allowed for greater precision than was previously possible. Cesium is evolving into a grandfather clock in this brave new world of ultra-precise timekeeping.

"As a general rule, the definitions of the SI units should be based on the measurement techniques that produce secondary measurements of those quantities with the lowest uncertainty, "IFLScience was informed by Dr. Liz Donley, director of the Time & Frequency Division at the National Institute of Standards and Technology.

"The accuracy of frequency measurements using optical frequency standards has improved to the point that they are 100 times more accurate than those utilising Cesium as the standard.

However, the second's definition has an impact on the definition of five of the SI's other six units, therefore these uncertainties have an effect on mass measurements, distances, etc. Almost all of the measurements we take are affected by a second that is more exact.

The International Bureau of Weights and Measures, which oversees and standardised the SI unit system, met at the 27th CGPM. To make choices about SI, including redefining base units, as was done in 2018, scientists and officials from standards organisations from throughout the world will convene.

The second is suggested to be redefined by 2030, either by a new, very precise atomic transition or by the weighted average of a number of highly accurate atomic transitions, among other things, in the draught resolution for the meeting held in November. First, it will be necessary to come to an agreement on a set of requirements that this new definition must meet.

For optical clocks to become the norm and the cesium to act as a secondary representation of the second, a number of requirements still need to be satisfied. The New York Times writes that efforts are being made to make those standards more clear and that an announcement might come as early as June of this year. Institutions from all around the world will need to go above and above to demonstrate a trustworthy new definition of the second, even with well defined constraints.

"We must choose which atom (or atoms) the new definition will be based on when the metrology institutions trying to meet the criteria reach some of the important milestones. Although progress is being made quickly, Dr. Donley informed IFLScience that there is still no agreement on this crucial matter.

Not only in laboratories are extremely exact measurements required. They have an impact on both current technologies and potential future ones that optical atomic clocks could bring about due to their ability to precisely record gravity changes and other phenomena.

Reference: New York Times

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