Two lutetium clocks agreed at the 19th decimal place

Each clock had evaluated uncertainty near 1×10⁻¹⁹, four times lower than the previous record.

The systems were compared after 200 hours of averaging, testing whether their systematic error budgets held in practice.

Why lutetium

Its optical transition is unusually insensitive to temperature and magnetic fields. Room-temperature operation and commercial lasers may aid portability.

Accuracy versus stability

Accuracy limits systematic offset; stability describes short-term fluctuation. The advance is verifying calculated accuracy by comparing two clocks.

Uses

Better clocks can support geodesy, navigation and tests for changing constants or dark matter. This is not a consumer timekeeping product.

Next

Other laboratories and long-distance networks must reproduce it. Redefining the SI second remains a separate international process.

Primary source and independent checks

Primary source: Nature paper

Institutional explanation: NUS/CQT release

Independent check: Nature independent news

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