Edinburgh is buzzing this week as the festival enters the last few days, so for our latest Curiosity of the Week we bring you one of the city’s intriguing landmarks.
Many people will have seen, and even walked up, the Nelson Monument in Edinburgh; but not everyone will be aware of the Time Ball and its purpose. The Time Ball is a large sphere attached to the top of the monument, which was installed in 1852 to aid passing ships. The heavy zinc-coated ball is attached to a wooden mast, which is fitted with directional arms pointing North, East, South and West.
The ball was originally fitted to the top of the Nelson Monument to help ships in the Firth of Forth calculate the exact time. Previously, ships would have had to send someone ashore with their chronometer (the ship’s clock), to the Observatory on Calton Hill, in order to set it to the right time. Before modern navigation aids, ships relied on a chronometer to calculate their longitude. So it was an important device.
But how does the Time Ball work? At 12.55 GMT the ball is raised halfway up the mast, to signal to navigators positioned offshore to get ready. Then, at 12.58 GMT the ball is raised to the top, so that at exactly 13.00 GMT the ball can be dropped. Since recent restoration, the ball is still dropped every day at 1pm (except Sunday).
As light travels faster than sound, this visual aid to ships offshore was thought to be more accurate than the sound of a clock striking. However, Edinburgh also has a cannon which is fired every day at 1pm.
You can visit the inside of the Nelson Monument, and take the steps to the top for a £5 admission fee. Inside the monument there is a tiny museum which has more information on the Time Ball and local naval history. If you want to see the Time Ball in action, then head near to or up to Calton Hill just before 1pm, and keep your eye on the white mast at the top.
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