Aside from the monarchy, one would be hard-pressed to think of anything more iconically British than the clock in the Elizabeth Tower of Westminster Palace. Its massive bell, Big Ben, has been keeping Londoners on time for over 150 years. In fact, it has maintained almost freakishly accurate time. It is the biggest, most accurate four-faced striking and chiming clock in the world. It maintains accuracy to within one second, and it does so by relying on some surprisingly-unsophisticated mechanisms: gravity and pennies.Huge weights power the clock on long cables that attach to each train of gears. The clock engineers wind the cables three times a week, and as gravity pulls the weights down, the gears rotate. Their rotation is regulated the swinging pendulum. The precision of the pendulum is adjusted by placing pennies on the mechanism. The addition of a single penny causes the clock to gain two-fifths of a second over a 24-hour period.

The clock’s chimes sound every fifteen minutes. The four notes played by these chimes are G#, F#, E and B and are sequenced in twenty-chime increments. Big Ben is the hour bell and also chimes on the note of E. The hour bell starts chiming exactly as the hour turns and emits a chime to represent every hour of the moment. For example, at five o’clock, five chimes will ring from the great bell. As long as the correct number of pennies is in place, these chimes will continue their proud tradition of keeping Britons punctual.