NPR's Noah Adams guides us through a century of timekeeping, beginning with the sound of Big Ben in London striking midnight on New Year's Eve, 1899. We hear how, even today, the BBC uses the live strike of Big Ben as the time signal on some newscasts, and, from the clock's guide, how pennies are used to adjust the time. Also, Steven Dick, historian at the US Naval Observatory, recalls how, in 1877, the time signal was sent by telegraph to the time ball in New York. Physicist Joe Taylor explains how pulsars could be the most stable time signal we have. The owners of the Balzer Family Clockworks in Freeport, Maine talk about their restoration of town tower clocks, and Danny Hillis explains his vision of the Millennium Clock, to be built underneath a Nevada mountains.