A Short History of Big Ben, the World’s Most Famous Clock Tower

The most iconic clock in the world is getting some overdue love. Big Ben—the 315-foot tower atop the Palace of Westminster—will be shut down in early 2017 to undergo $42 million worth of repairs.

The world famous clock has told time and its bells have rung through the streets of London for more than 150 years. It’s appeared in movies, been printed on t-shirts and has become a lasting symbol of Great Britain. But while everyone can identify Big Ben, few know about its incredible history. Few know that coins are used to keep the clock accurate. And even fewer know that Latin inscriptions are carved into the clock.

The structure has three distinct parts: the Elizabeth Tower, the Great Bell and the Great Clock. Big Ben—which was the original name for the clock’s bell—has been generally accepted as the name of all three parts.

A terrible fire destroyed most of the Palace of Westminster in 1834. The Elizabeth Tower—as it was later named in 2012—was designed in its place by English Architect Sir Charles Barry. With the tower standing about the Houses of Parliament, the four clocks needed to be both beautiful and accurate.

The Movement

Astronomer Royal Sir George Airy developed high standards for the clock. The first stroke of each hour had to be accurate to within one second and the clock’s performance had to be telegraphed twice a day to the Greenwich Observatory.

The pendulum is 13 feet long, weighs 660 pounds and is suspended on a strip of spring steel–1/64 of an inch in thickness. It beats every two seconds. The clockwork mechanism weighs 5 tons.

After more than 150 years in service, the clock needs to be adjusted. How is this done? With old coins. That’s right, coins.

A small stack of pre-decimalization pennies (31mm in diameter, 9.4g) are placed on top of the pendulum to adjust the timing of the clock. Adding a coin has the effect of ever-so-slightly lifting the position of the pendulum’s center of mass. This has a result of reducing the effective length of the pendulum rod, which then increases the rate of the pendulum swings. One penny changes the clock’s speed by about 0.4 seconds a day.

The Dial

The Great Clock’s dial was built by Augustus Welby Pugin—who collaborated with Barry on the Palace of Westminster’s design. Each cast iron dial is about 23 feet in diameter. They each contain 312 separate pieces of pot opal glass, similar to a stained glass window. An interesting detail is contained in the Great Clock’s dial. On many Roman numeral clock dials, the four o’clock is displayed as “IIII” as a way of better balancing the dial. On the Great Clock, it’s displayed as “IV.”

The hour hand is nine feet long and the minute hand is 14 feet long. When the clock was first installed in the tower in April of 1859, it wouldn’t work. The cast-iron minute hands were far too heavy. They were replaced by lighter copper hands, and it successfully began keeping time on May 31, 1859.

Big Ben Goes Dark

As London has been a target for many enemies during wartime, Big Ben has had to keep a low profile. For two years during World War I, the bells were silenced and the clock faces were not illuminated at night to avoid guiding attacking German Zeppelins. The clock faces went dark again in September 1939 as German planes started their blitzkrieg during World War II.

Even Big Ben Gets the Time Wrong

A number of circumstances have affected the clock’s accuracy of the years. In 1949, the clock slowed by four and a half minutes after a flock of starlings perched on the minute hand. On New Year’s Eve in 1962, the clock slowed due to heavy snow and ice on the long hands. As a result, Big Ben chimed the new year in 10 minutes late.

The first and only major breakdown occurred on August in 1975. The air brake speed regulator of the chiming mechanism broke from fatigue after more than 100 years of use. This caused the fully wound four-ton weight to spin the winding drum out of the movement, causing great damage.

The Great Clock was shut down for a total of 26 days over nine months. It was reactivated on May 9, 1977. This was the longest break in operation since its construction.

Time Catches Up to Big Ben

Big Ben has held a legendary record of keeping impeccable time. But even the Great Clock needs a specialist’s touch. Big Ben is scheduled for $42 million worth of repairs in early 2017. The clock will not chime for several months while it’s being refurbished, just the third time in Big Ben’s 157-year history that the clock will be silenced.

Experts have identified problems with the clock hands, mechanism and pendulum. The British government says the problems need to be addressed immediately to ensure that the clock can continue to work properly.

It’s been over 31 years since the last extensive repairs were made to Big Ben. And even though the clock may be out of service for some time, it will continue to stand as a remarkable example of innovative and beautiful clockmaking.