India, Jan. 4 -- "T here's never a dull moment in timekeeping," says Poonam Arora, senior principal scientist and head of the Indian Standard Time Metrology Division of the National Physical Laboratories (NPL) in Delhi. Think of her as India's ultimate clock-watcher. Arora oversees the machines that set and maintain the most accurate time for the nation, down to the nanosecond. So, don't go in expecting Big Ben. The most precise time-keeping devices on the planet no longer have hands, a face or even quartz mechanisms. "A clock is simply a combination of an oscillator and a counter," Arora says. At NPL, caesium atoms do the oscillation inside a sealed cylinder that looks like a craft-brewery tank. A maze of lenses on one side cool the atoms,...