Caesium 133 clock9/19/2023 ![]() With each order of magnitude in improvement, researchers have imagined new ways to exploit the extreme abilities of these clocks. In 2013, optical atomic clocks were shown to be better than cesium atomic clocks, and new records in accuracy have arrived yearly since then ( 5). This opened the door for creating optical atomic clocks. Researchers could line up one of the teeth of the laser light to the oscillations of an atom radiating in optical frequencies, lock the laser frequency to that line, and use sophisticated electronics to tally the transitions. ![]() Each pulse is of a different color or frequency, and the comb spans the entire visible spectrum. This device uses a laser to generate extremely short pulses of light that appear as spikes at regularly spaced intervals, creating what looks like the teeth of a comb. No one knew how to count these lightning-fast ticks.Ī breakthrough came in 1999 when physicists developed what is known as a femtosecond optical frequency comb ( 3, 4). “Optical transitions are just way too fast,” says physicist Mukund Vengalattore of Cornell University in Ithaca, NY. Although perfect for even more precise clocks, these atoms posed a serious challenge. But other atoms-such as aluminum, strontium, and ytterbium-have natural oscillations at optical frequencies, corresponding to visible light, which are about 100,000 times faster. The cesium-133 radiation is in the microwave portion of the electromagnetic spectrum. The work led to the modern definition of a second as the time it takes to complete 9,192,631,770 such oscillations of the cesium-133 atom. These atoms emit radiation as they oscillate between two closely spaced energy levels. In 1955, physicists Louis Essen and Jack Parry developed the first atomic clock at the National Physical Laboratory in London by using ions of cesium-133 as tiny subatomic pendulums ( 2). “I think you could argue that it’s kind of at the core of everything,” he says.Īlbert Einstein famously defined time as “that thing you measure using a clock.” Clocks need a moving part, like a pendulum, to mark the passage of time. He thinks major new insights are sure to come from the high-precision measurement of time. Ye’s team constructed the record-holding clock announced in March. 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). It may seem startling that precision clocks have such ramifications. This, in turn, can help climate researchers monitor sea level rise and geologists track the movement of tectonic plates. 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. 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. Image courtesy of Ye Labs, JILA.Īnd yet, the device, known as an optical atomic clock, will allow physicists to do a lot more than tell time. The synchronized atoms are used to count infinitesimal ticks for the world's most precise optical atomic clock. Trapped atoms of strontium-87 produce a bluish glow within a shielding box surrounded by thermal sensors.
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