Dropping Balls to Tell Time

Everyday, at five minutes to one, a bright orange ball on the roof of Flamsteed House at Greenwich’s Old Observatory in London, slides half-way up a pole. At two minutes to one, it rises all the way to the top. At exactly one PM, the ball falls with a dull thud. Anyone who is looking at the ball when it drops can instantly verify whether their watches are telling the correct time. In this current age, when time could be easily synchronized over the internet or by using mobile signals or GPS technology, “time balls” are superfluous, but back in the Victorian era this was one of the few ways by which time was announced to the public.

Back in those days, few people could afford to have their own watches and clocks, instead relying on the hourly chimes of the church clock to tell time. The church clocks were not very accurate but most people had no need for precise time.

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The time ball atop Flamsteed House at Greenwich, London. Photo credit: Carmen Seaby/Flickr

Things were different for a ship’s captain. Ships needed extremely precise clocks to determine their position at sea, which they did by taking celestial readings and coordinating those readings with the time they were known to occur at another point on earth, such as at Greenwich. The breakthrough came in 1761 when John Harrison, a Yorkshire carpenter, developed a chronometer that was accurate and portable enough to do the job. But Harrison’s remarkable invention was still useless if it couldn’t be set correctly before departing on a long voyage.

The idea of the time ball was proposed in 1829 by Robert Wauchope, a Royal Navy captain. Robert suggested that the time ball be set up at the harbor and dropped at a specific moment to indicate the time. Sailors could view it through a telescope and set their chronometers accordingly.

A visual signal rather than an audial one, as in church bells, was also advantageous. Sound travels slow through the air, taking about three seconds to cover a kilometer. So the farther out the observer is from the source of the sound, the longer it takes to receive the signal. Wind, rain, humidity and other atmospheric conditions also affect the speed of sound. Relying on sound signals to tell time was inherently flawed.

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The Greenwich Time Ball. Photo credit: David Brossard/Flickr

The first time ball was erected in the harbor at Portsmouth, England. It worked so well that in 1833 another one was set up at the Greenwich Observatory on a hilltop —the same one that you see today. The first American time ball went into service in 1845 at the United States Naval Observatory in Washington, D.C.

Time balls were typically dropped at 1PM, although in the United States they were dropped at noon. It’s believed that 1PM was chosen rather than noon because astronomers, who operated the time balls, were always busy doing important observations at midday when the sun is at its apex. Another explanation could be that it was easier for sailors to anticipate the arrival of 1PM after noon had passed than to wait for noon itself.

As the years passed, better time keeping mechanisms were developed such as telegraphic communication and electronic time signals, and time balls became obsolete.

There are over sixty time balls standing at harbors around the world today. A few of them are still operating for the novelty or for tourists, like the one at Greenwich Observatory . Some time balls drop on special occasions, such as the Times Square time ball in New York which drops at midnight on new year’s eve.

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The Greenwich Time Ball. Photo credit: Duncan Stephen/Flickr

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The Greenwich Time Ball. Photo credit: www.rmg.co.uk

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The Boston Time Ball on the roof of the Equitable Life Assurance Society building. (1881). Photo credit: Winslow Upton and William Babcock Hazen/Public domain

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