NOW there’s no excuse for being more than a million-billionth of a second
late. Researchers at the US government’s National Institute of Standards and
Technology in Boulder, Colorado, have created a “femtosecond” clock so accurate
that it would be no more than a second out after 30 billion years.
The clock counts the oscillations of a laser beam, which are held at an exact
frequency by linking the laser to electrons jumping between energy levels in a
mercury ion. These transitions tune the laser oscillator to “tick” 100,000 times
as fast as conventional atomic clocks, which are based on…
