Scientists are hoping to redefine the second – here's why

Everyone needs to know the time. Ever since the 17th century Dutch inventor Christiaan Huygens made the first pendulum clock, people have been thinking of good reasons to measure time more precisely.

Getting the time right is important in so many ways, from running a railway to doing millisecond trades on the stock market. Now, for most of us, our clocks are checking themselves against a signal from atomic clocks, like those on board the global positioning system (GPS) satellites.

But a recent…

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