Amazingly precise optical atomic clocks are more than timekeepers

Abstract

In March, physicists unveiled the world’s most accurate timepiece. But this was no pocket watch. At its heart is an atomic pendulum that swings 500 trillion times per second and can measure fractions of a second out to 19 decimal places (1). The clock is so precise that it loses at most a tenth of a second over the entire lifetime of the universe. Trapped atoms of strontium-87 produce a bluish glow within a shielding box surrounded by thermal sensors. The synchronized atoms are used to count infinitesimal ticks for the world's most precise optical atomic clock. Image courtesy of Ye Labs, JILA. And yet, the device, known as an optical atomic clock, will allow physicists to do a lot more than tell time. Such clocks can help investigate fundamental constants of the universe with higher precision than ever before, searching for discrepancies in our current theories of reality. And because time and space are intimately related, these ultra-accurate clocks can also act like measuring tape, mapping the size and shape of Earth with a resolution of a centimeter or less. This, in turn, can help climate researchers monitor sea level rise and geologists track the movement of tectonic plates. It may seem startling that precision clocks have such ramifications. But any time science gets a new tool to study nature, it throws up surprises, says physicist Jun Ye of JILA, a research institute jointly operated by the University of Colorado Boulder and the National Institute of Standards and Technology (NIST). Ye’s team constructed the record-holding clock announced in March. He thinks major new insights are sure to come from the high-precision measurement of time. “I think you could argue that it’s kind of at the core of everything,” he says. Albert Einstein famously defined time as “that thing you …