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Optical Clock Could Redefine Time

  • VOA News

FILE - Fireworks explode over Elizabeth Tower housing the Big Ben clock to celebrate the New Year. The successful testing of a hyper-accurate clock could bring developments in physics and other areas of science.

The second, as we know it, may soon be a thing of the past as a measurement of time.

French physicists have successfully tested two optical lattice clocks, which would lose just one second every 300 million years. The clocks are so accurate, they could lead to a new definition of a second.

Optical lattice clocks, which have been around for about a decade, could one day replace the atomic clocks, which have been the standard for decades. Atomic clocks work by measuring the vibration of cesium atoms exposed to microwaves.

Since 1967, the second has been defined as the duration of 9,192,631,770 oscillations of the microwave radiation absorbed or emitted when a cesium atom jumps between two particular energy states. Atomic clocks are accurate to one second every 100 million years.

The two new optical lattice clocks are being tested at the Paris Observatory. The Observatory’s Dr. Jerome Lodewyck says the new clocks use the element strontium instead of cesium and laser beams instead of microwaves.

Both atomic and optical lattice clocks can be compared to a grandfather clock, which uses the swing of a pendulum to measure intervals of time. The “swing” of an atomic clock’s cesium pendulum occurs trillions of times every second. An optical lattice clock strontium oscillations are 40,000 faster.

That allows the division of intervals into smaller, more precise units, giving the optical lattice clock an accuracy of one second every 300 million years.

While losing a second every 300 million years might not seem important in daily life, many technologies such as telecommunications, satellite navigation and stock markets depend on incredibly accurate timekeeping.

Highly precise timekeeping has been integral to the development of the Global Positioning System (GPS) because of the high degree of synchronization required for satellites to triangulate a receiver’s location.

The new super-accurate clock could have implications for theoretical physics in that it could allow physicists to see if nature’s constants do really do remain constant over time. Also, Earth-observation satellites could be improved because they would allow more accurate tracking of sea-level rise.

But despite the new optical lattice clocks’ accuracy, they may not be the final answer. The U.S. National Institutes of Standards and Technology (NIST) in Colorado has developed an ion clock that is believed accurate to within one second every 3.7 billion years, but it is not yet considered stable enough to use and requires more testing.