![]() “Exquisitely precise timing is built into every aspect of modern infrastructure,” Thomas O’Brian, chief of the Time and Frequency Division at N.I.S.T., told me. A recent test by the National Institute of Standards and Technology demonstrated an optical clock, running on the rare-earth metal ytterbium, that breaks every second into more than five hundred trillion intervals. The competition between these labs has evolved into something “like an Olympics of time standards,” Madej said. It converts this to four hundred and thirty trillion “ticks,” parsing time more finely than any of today’s microwave clocks. ![]() Madej’s single-ion clock measures the four hundred and thirty trillion light waves per second required to energize a strontium atom. Because these clocks rely not on microwaves but on lasers, which operate at far higher frequencies, they can split each second into more intervals. In a cesium-based atomic clock, each cycle can be thought of as a pendulum swing.Ī number of metrology labs around the world, like Madej’s, have been developing a new generation of atomic timepieces, known as optical, or optical-lattice, clocks. Cesium, the element most commonly used in high-precision atomic clocks, is nudged into an excited state at a microwave frequency of just under 9.2 billion cycles per second. To set that frequency, metrologists, as scientists of measurement are known, exploit a law of quantum physics: atoms become excited, and their structure changes, when they are exposed to specific amounts of energy-and the amount of energy required to cause a transition from one particular state to another is immutable, specific to each element. Most of today’s atomic clocks keep time by counting high-frequency microwaves.
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