According to major media reports, the strontium optical lattice clock is capable of measuring seconds to 19 decimal places. If it ran for 30 billion years – more than twice the current age of the universe – it would only be off by around a second. This precision represents a major breakthrough in optical clock technology and signifies a step towards changing the official definition of a second within the next decade or so.
' Currently, the second is defined in the International System of Units (SI) as 9,192,631,770 oscillations of the cesium-133 atom, but cesium atoms have a margin of error as they swing back and forth nine billion times per second. In contrast, strontium oscillates at a significantly quicker rate of 700 quadrillion 'ticks' per second, making it a much more accurate measurement. Two other strontium optical clocks have already passed this milestone, and having a third means scientists are one step closer to officially redefining the second.
This performance meets the 2 x 10^–18 single-clock accuracy requirement for redefining the SI second.
For the official definition to be changed, at least three optical clocks based on the same type of 'tick' and with a certain level of precision and stability need to be in use at different institutions. The timeline for the proposed redefinition is set by meetings of the General Conference on Weights and Measures (CGPM), held every four years, with a request to work towards a proposal for the new definition to be presented at the 29th meeting in 2030. Beyond redefining the second, the clock could play a crucial role in various fields, such as aiding the search for dark matter and specific measurements of Earth's gravitational field.
' This could support future applications including tests of fundamental physical laws, next-generation satellite navigation systems, and the establishment of a unified ultra-precise time network.
The new achievement provides a viable technological path for developing portable and space-based optical clocks.