Physicists create groundbreaking atomic clock that's off by less than 1 second every 100 million years

An abstract illustration of a clock with swirls of light.

Scientists have developed one of the most precise atomic clocks ever built, and they plan to use it as a reference clock to define time itself.

Based on the rising and falling of cesium atoms under a microwave beam, the NIST-F4 atomic clock is so reliable that if it had started to run when dinosaurs existed 100 million years ago it would be off by less than a second today, according to its creators.