A Penny Keeps Big Ben on Time

It takes just a penny to keep Big Ben on atomic time.

Two stacks of pennies stand on top of the pendulum, and by removing one, the timekeepers are slowing the pendulum enough to give it the leap second created by the Earth’s erratic rotation.

For the start of the New Year, London’s favorite old timepiece is in step to the half-second with the atomic clocks that keep the world’s time.

The pennies themselves are special. Heavier than modern pennies, they went out of circulation after Britain decimalized its currency in 1971.

“We still get little old ladies sending in their old pennies for Big Ben,” says Rick Braddock, an official of the government agency that maintains the clock.

The accuracy of this giant clock, which for 129 years has survived pollution, foul weather and war, is London’s best-known landmark and its chimes are heard throughout the world through the British Broadcasting Corp., which uses them to introduce its newscasts.