Scientists Get Nearer To Redefining The Size Of A Second : NPR

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Scientists have made new, more accurate comparisons between types of atomic clocks. Hide Jun Ye caption

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Jun Ye

Scientists have made new, more accurate comparisons between types of atomic clocks.

Jun Ye

Scientists are getting one step closer to redefining the length of a second.

To do this, they use atomic clocks.

Atomic clocks, which look like a jumble of lasers and wires, use the natural oscillation of atoms, with each atom “ticking” at a different speed.

Modern conveniences such as cell phones, internet and GPS are made possible by the ticking of atomic clocks.

“Every time you want to find your location on the planet, ask what time it is from an atomic clock that is in the satellite that is our GPS system,” said Colin Kennedy, physicist at Boulder Atomic Clock Optical Network (BACON) collaboration, tells NPR’s All Things Considered.

The world’s standard atomic clocks have been based on cesium atoms, which tick around 9 billion times per second, for decades.

However, newer atomic clocks based on other elements tick much faster – which means that it is possible to divide a second into smaller and smaller slices.

These newer atomic clocks are 100 times more accurate than the cesium clock. But it was important to compare them – to “make sure that a clock made here in Boulder is the same as a clock made in Paris or in London or in Tokyo,” he says.

“Ultimately, the goal is to redefine the second in terms of a more accurate and precise standard that we can use to make more accurate and precise measurements,” says Kennedy.

That means having a clock that, if set back billions of years to the beginning of the universe, would only be offset by a second, adds physicist Jun Ye, who was also involved in the collaboration.

As BACON scientists, which include researchers from the University of Colorado Boulder and the National Institute of Standards and Technology, 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 to link their watches, which are housed in two separate laboratories in Boulder, Colorado. They also used a fiber optic cable.

“It was definitely a fun experiment,” Ye told NPR. “And it’s very safe in every way and very remote for people’s daily life.”

The result is a closer comparison of these types of atomic clocks than ever before.

Ye says networks of such clocks could also be used as hypersensitive sensors – potentially detecting a passing wave of dark matter and testing Einstein’s theory of relativity.