Fri., January 24, 2014 10:30pm (EST)

Tickety-Tock! An Even More Accurate Atomic Clock
By Nell Greenfieldboyce
Updated: 3 months ago

Computer networks and GPS systems are only possible because of the precision timekeeping of atomic clocks like the one above, says clockmaker and physicist Jun Ye.
Computer networks and GPS systems are only possible because of the precision timekeeping of atomic clocks like the one above, says clockmaker and physicist Jun Ye.
Scientists announced this week that they have created the most advanced clock in the world.

The clock, described this week in the journal Nature, is so precise that it would neither lose nor gain one second in about 5 billion years of continuous operation. That's pretty good, considering that the Earth itself is only around 4.5 billion years old.

Since the 1960s, official timekeeping has been based on the natural oscillations of atoms. And scientists just continue to come up with better designs for so-called atomic clocks. A few years ago, a team unveiled a clock that would neither gain nor lose one second in about 3.7 billion years.

Now that feat has been bested by a team led by physicist Jun Ye of the National Institute of Standards and Technology in Boulder, Colo.

"Many people would say, 'Well, one second in 5 billion years how is that going to impact our lives? It's going to be irrelevant to what we are doing in daily life or in the society.' But that's actually not true," says Ye.

He says advances in clocks have ripple effects for all kinds of technology. Today we depend on things like computer networks and GPS systems that are only possible because of the precision timekeeping of atomic clocks even though the first atomic-clock makers could not have predicted where their inventions would lead. "Nobody would have imagined everybody can have a cellphone and know exactly where you are," Ye says.

At the most basic level, to make a clock you just need something that repeats itself over and over in a way that lets you count off equal increments of time.

The new record-breaking clock uses laser light to trap a few thousand atoms of a metallic element called strontium. Scientists can detect the oscillations, or ticks, of the atoms 430 trillion per second.

The team already has upgrades in mind to improve this clock's performance. Ye says maybe they'll be able to build a clock that is accurate to one second in 50 billion years or even much better than that.

"Where does it end? Does nature place a fundamental limit on how good you can keep the time?" he wonders. "As far as I can tell at the moment, I don't see the limit."

Future superclocks could help scientists explore the bizarre quantum world, or probe the space-time fabric of the universe.

Ye imagines a network of immensely powerful clocks distributed around the Earth. If a black hole explodes in a distant galaxy, he says, "there will be space-time ripples so-called gravitational waves will propagate, and we can actually just listen to the clock and ... know the heartbeat of the universe."

Throughout history, technologies for keeping track of time have had a powerful impact on humanity, says Adam Frank, an astrophysicist at the University of Rochester who wrote a book called About Time.

For ages, telling the time by the sun or the moon was good enough, says Frank. "Those were literally the first clocks for people."

But when societies got more complicated, mechanical clocks took off. First they were in bell towers, then in people's homes. Clock technology advanced from merely ticking off the hours to keeping track of every minute and every second. It was a huge change that today we take utterly for granted, says Frank.

"When you're waiting for the bus, and the bus is late, you feel those five minutes," Frank notes. "You feel those minutes as boredom, as anger, but that's only because you have a device that allows you to count off those minutes."

He says while it may not be apparent now how new atomic clocks might change our experience of time, someday people may interface directly with computers and become aware of fractions of seconds.

People who live far off in the future, Frank says, "may be living in an entirely different time-logic than us, because of their technology for timekeeping."


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