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Physicists Develop World's Most Accurate Clock

  • Shelley Schlender

If you like to be on time, take a minute and listen in: Scientists at the University of Colorado in Boulder, working with the National Institute of Standards and Technology, have created a clock that's accurate to within one second in 200 million years. That's twice as accurate as the current official clock used for the United States, which in turn, contributes to the precision of official world time. Reporter Shelley Schlender visits the laboratory where the new strontium atomic clock is ticking.

In a shop full of grandfather clocks, each one chimes at a slightly different time. That's because, minute by minute, week by week, most timekeeping devices get a little bit off.

But in our fast-paced world, many applications need more accuracy. And in a laboratory at the University of Colorado, physics professor Jun Ye says that his team's new experimental clock may become one of the best. It's even more precise than the official U.S. standard clock — a sophisticated atomic timepiece that is accurate to within one second every 80 million years.

Ye says that the strontium atomic clock is more than twice as accurate because it ticks faster. "It's a general principal that when you're making a clock, you want the underlying oscillation to be as fast as possible because that allows you to check out mistakes much quicker," he explains.

How fast is an oscillation? Well, a grandfather clock goes tick-tock around once a second. The most accurate clocks in use today count the natural ticking inside an atom that comes from energy jumping back and forth … billions of times every second.

Physicist Andrew Ludlow, who's working with Jun Ye, compares it to the pendulum of a grandfather clock. "It's swinging back and forth. The grandfather clock is counting how that swinging is happening, and that's ultimately what's keeping track of time -- that pendulum inside the grandfather clock. In the same way, the atom has a natural oscillation frequency. We're looking to count those oscillations, to see how that atom is evolving, and that ultimately is the clock."

What's different about their clock, Ludlow says, is what it uses to count the oscillations. One of the most accurate clocks in use today is the U.S. standard clock at the National Institute of Standards and Technology in Boulder. It relies on bursts of microwave radiation to do the counting. But while those microwaves ripple incredibly fast, they miss a bunch of ticks. Ludlow says their new, experimental clock uses something that oscillates even faster, and catches more ticks — laser light.

To run this super-high precision clock takes an incredible amount of equipment. In the lab are four tables, each the size of a small truck, covered with wires, vacuum pumps, lasers, mirrors, metal boxes and magnifying glasses. Andrew Ludlow says that's to be expected. "We're not looking to put this on our wrist anytime soon," he says with a grin.

But the world's first computers filled an entire room, and now many computer devices do fit on your wrist. So Ludlow says that someday, this enormous clock will be smaller… but its impact on society will be big. He predicts that more accurate clocks will improve wireless communication and navigation systems here on earth, and in spacecraft that will explore other worlds.