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Picture Courtesy:  THE HINDU

Context:  

Optical clocks are set to redefine the second by 2030 after a successful global precision comparison test.

How is "Second" defined currently?

The official length of one "second" comes from special devices called caesium (Cs) atomic clocks. These clocks do not directly measure time like wall clocks. Instead, they work by counting the tiny, super-fast vibrations that caesium atoms make when they jump between specific energy levels.

How accurate are these caesium clocks?

Caesium atomic clocks are accurate. For example, the atomic clock that sets the U.S. national time standard would only lose one second every 300 million years. Many countries have their own caesium clocks to maintain their national time standards, and they use satellites and fiber optic cables to share this precise time. India, for example, uses five caesium atomic clocks at its National Physical Laboratory in New Delhi to keep its time accurate.

What are optical clocks?

Optical clocks are the next generation of timekeeping. They work on a similar principle to caesium clocks but use different atoms (like strontium or ytterbium) and a much higher-frequency light (optical) signal instead of microwaves.

Scientists expect optical clocks will replace caesium atomic clocks as the world's official time standard around the year 2030. However, before that happens, these new clocks must pass very strict tests to prove they can work perfectly in sync from different places around the globe. 

Source: 

THE HINDU