As per the latest IERS directive, time will stop for one second on December 31, 2008, at UTC 23:59:60, or 5:30 a.m. on New Year morning as per IST. “This is the 34th time such a ‘leap’ of a second—a positive one, which involves adding a second—is going to be carried out. Some years, there are two leaps, and some don’t have any, depending on the rotational correlation,” says Dr Banerjee, whose romance with timekeeping spans three decades.

“Knowing the exact time may not be important to you and me, but those who use the Global Positioning System (GPS), for example, need an accurate measure, down to the nanosecond. (In one nanosecond, a billionth of a second, light travels 30 cm.) The accuracy of GPS coordinates depends on the accuracy of the time measure given by the atomic clock on the GPS satellite,” Dr Banerjee explains. Over 350 atomic clocks around the world compare their time with GPS time and send the data to the BIPM, which calculates UTC as an average of the global atomic clock measures. “The US has about 150 atomic clocks. In India, apart from NPL, ISRO has a few. I want all the clocks to be hooked up to a network so a nationwide average can be calculated,” he says.

Accuracy has never been so much in vogue. Space research stations and power grids require a highly specific time measure. And with a host of radio stations jostling for frequency, there is demand for a more accurate frequency source for broadcasting—unlike pendulum frequencies, atomic frequencies used in cesium clocks are constant and universal. The most accurate clock in the world, the cesium fountain clock developed in France and the US, makes the Rs 35-lakh cesium atomic clock seem antique. It can run for 20 million years without derailing the time measure by even a second. NPL is trying to develop one of these, but has so far met with little success.

... contd.