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If you head southwest out of London, you might enter Teddington, a suburb with tree-lined avenues that sits on the banks of the river Thames. Here, in this innocuous neighborhood, you’ll find one of the United Kingdom’s more unusual security programs: the National Timing Centre (NTC), a government-led laboratory that is working to create a new, more resilient way for the country to measure time.
For decades, the UK, like almost every other country, has relied on global navigation satellite systems—signals from satellites orbiting in space—to tell the time accurately. These GNSS signals provide the foundation for mobile networks, energy grids, and the internet. They’re the source of the time on your smartphone, your laptop, and pretty much any other smart device that plays a part in your life. But there are growing fears that GNSS could be disrupted or fail—and with huge implications. A five-day disruption would cost the British economy an estimated £5.2 billion ($6.15 billion).
In 2017, an independent report commissioned by the British government declared that ignorance of the importance of precise time measurement, and the role of GNSS in providing it, was “especially acute.” It added that the vulnerability of the system, to both natural and intentional interference, was “poorly understood,” before recommending that the country take steps to increase the resilience of its accurate timing.
“Our dependency on time, an invisible utility, is rapidly increasing across our digital infrastructure,” says Leon Lobo, head of the NTC program. And yet despite this, the UK’s time is provided through a vulnerable system, he explains. This is why, in 2020, the NTC was set up.
Exactly how your phone and, say, a departures board in a train station both show you the same time might not be something you’ve thought about before—but here’s how this is achieved. GNSS signals are delivered through a constellation of satellites, with each satellite broadcasting coded messages stating which satellite it is, its location in space, and a stable time stamp that it generates on board through multiple atomic clocks, the gold standard of time measurement. These measure time by counting the oscillations of certain atoms, whose vibrations are highly consistent and stable, meaning that clocks relying on them barely drift. (NASA’s atomic clock, for example, will stay precise to the second for more than 10 million years.)
When a signal is received by a GNSS receiver, thousands of kilometers below, on earth, it’s able to calculate the distance to the satellite that sent it by measuring the time delay between the signal’s transmission and its receipt, because radio signals travel at a known speed. Provided the receiver is able to receive a signal from at least four satellites, it can calculate not only its position to meter-level accuracy but also the local time to fractions of a microsecond.
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