Scientists Get Closer To Redefining the Length of a Second

Scientists are inching one step closer toward redefining the length of a second. NPR reports: Atomic clocks, which look like a jumble of lasers and wires, work by tapping into the natural oscillation of atoms, with each atom "ticking" at a different speed. The worldwide standard atomic clocks have for decades been based on cesium atoms -- which tick about 9 billion times per second. But newer atomic clocks based on other elements tick much faster -- meaning it's possible to divide a second into tinier and tinier slices. These newer atomic clocks are 100 times more accurate than the cesium clock. But it was important to compare them to each other -- to "make sure that a clock built here in Boulder is the same as a clock built in Paris, as in London, as in Tokyo," [Colin Kennedy, a physicist at the Boulder Atomic Clock Optical Network (BACON) Collaboration] says.

"Ultimately, the goal is to redefine the second in terms of a more accurate and precise standard, something that we can make more accurate and more precise measurements with," Kennedy says. As the scientists with BACON [...] wrote in the science journal Nature last week, they compared three next-generation atomic clocks that use different elements: aluminum, strontium and ytterbium. The scientists shot a laser beam through the air in efforts to connect their clocks, which are housed in two separate laboratories in Boulder, Colo. They also used an optical fiber cable. What resulted is a more accurate comparison of these types of atomic clocks than ever before. [N]etworks of clocks like this could also be used as super-sensitive sensors -- to possibly detect a passing wave of dark matter, and to test Einstein's theory of relativity.

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