A Clockwork Strontium: The Future of Timekeeping

In early 2014, a new atomic clock was unveiled at JILA, a joint institute of the University of Colorado Boulder and the National Institute of Standards and Technology (NIST). This strontium atomic device, which set new world records for both stability and precision, has been heralded as a breakthrough in the science of timekeeping.

Atomic clocks keep time based on the frequencies of atoms. Their performance is measured by two primary metrics. The first is stability, or the variation of its speed. The second is precision, which is how closely the clock reaches the frequency at which its atoms oscillate between two energy levels.

First Atomic ClockThe first atomic clock was invented in 1949 at NIST (then known as the National Bureau of Standards) and, because of its accuracy compared to other timekeeping technologies, a new field of research evolved. Photo Credit: NIST.

According to NIST representatives, this clock is so precise that it can keep perfect time for 5 billion years. A small interior chamber contains strontium atoms suspended in a crisscross of laser beams.

When researchers ping them, they vibrate at lightning-quick frequency, turning the clock into a type of atomic metronome ticking out the seconds in tiny fractions.

Record Holder

It is the first clock to hold world records for both stability and precision since cesium fountain atomic clocks became available in the 1990s, and is around 50 percent more accurate than the previous record holder, which is NIST’s quantum clock. Because of its high performance level, it presently serves as the time and frequency standard for the United States.

Thomas O’Brian, who heads NIST’s Time and Frequency Division, said that the clock’s unprecedented ability will “not only lead to better use of things like GPS, but probably open up entirely new applications that I’m not even smart enough to think of yet.”

Technology That Underscores the Atomic Clock

Perfect timekeeping is essential for maintaining a lot of modern tools and conveniences, such as GPS, global telecommunications, and electrical grids. The technology that underscores the strontium atomic clock is so sensitive to gravity, magnetic fields, force, motion, electrical fields, temperature, and other phenomena that it could potentially be used to map the earth’s interior, or help locate underground water springs and other subterranean resources. If a network of these clocks were positioned in space, they could conceivably detect the gravitational waves generated by exploding stars and black holes.

JILA/NIST Fellow Jun Ye and the strontium lattice clock. credit: J. Burrus/NIST

The Next Time Standard?

National Institute of Standards and Technology scientists continue to develop next-generation atomic clocks using different atoms as a base: mercury, ytterbium, aluminum, and calcium. Although still in the experimental stage, these clocks have been showing rapid progress in their timekeeping ability, and each atom type has its own distinct advantages. At the very least, they may enable new technologies, and one might become the next time standard.

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