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Greenwich and the story of time

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Finding longitude at sea

Making navigation safer

Many European countries were looking at ways to make navigation safer. England had much to gain by finding an accurate method for calculating longitude.

Foundation of the Royal Observatory

Christopher Wren. © NMM

In 1675 King Charles II issued a warrant to build a new observatory in Greenwich Park. It would be a place where astronomers could study the heavens and perhaps provide mariners with an answer to the longitude problem.

The Royal Observatory was designed by Sir Christopher Wren. It was completed in 1676 at a cost of just over £500. In order to keep expense to a minimum, many materials used in the construction were re-cycled. Selling off spoiled gunpowder raised much of the budget!

John Flamsteed - the first Astronomer Royal

John Flamsteed. © NMM

In 1676, John Flamsteed, a young astronomer from Derbyshire, was appointed first Astronomer Royal. He set about the massive task of plotting the position of all known stars, and making thousands of observations of the Sun and Moon. This information was published in his work known as the Historia Colestis.

Mapping the heavens is an extremely lengthy process. It takes almost 20 years just to observe the Moon through its complete cycle through the heavens.

On every clear night, Flamsteed would watch the Moon as it moved across the stars. He suffered from cold as heating was not allowed for fear the warm air would distort light as it entered the telescope.

Flamsteed was able to produce such accurate charts and tables only with the use of the latest scientific instruments. Telescopes and clocks were his main tools. Part of the reason the longitude problem was not solved earlier is that accurate clocks were developed only in the 1660s.

The difficulties of creating an accurate maritime clock

In 1657 Christian Huygens, the Dutch mathematician, was the first to make clocks that kept time to within a few seconds rather than many minutes a day.

It was recognized that if a similar clock could keep time on board a moving ship, it would provide an alternative to the ‘Lunar Distance’ method of finding longitude.

Huygens developed a portable version of his pendulum clock, but when it was tested at sea, it did not meet his expectations. Most people believed a clock would never be of use in navigation and the future was in using the positions of stars.

The Octagon Room. © NMM

Two of the earliest long pendulum clocks ever made were commissioned for use at Greenwich. They were built by the leading clockmaker of the day, Thomas Tompion, who had a business in Fleet Street. One of these clocks is displayed in the Octagon Room in the Royal Observatory. It is still running today after more than 300 years.

The competition to find longitude at sea

Sir Cloudisly Shovel in the Association with the Eagle, Rumney and the Firebrand, lost on the Rocks of Scilly, October 22, 1707. © NMM

On 22 October 1707 one of the worst ever maritime disasters forced the British government to renew its effort in solving the longitude problem.

Admiral Sir Cloudesley Shovel, commanding a fleet of 21 ships, was sailing from Gibraltar to England when five of the ships struck the Isles of Scilly. Four of the vessels were wrecked and almost 2000 men were killed. This was only one of many such disasters at the time and poor navigation was to blame.

The Longitude Act

The British government took radical measures by passing an Act of Parliament that offered a maximum cash prize of £20,000 to anyone who could solve the longitude problem by any method that was ‘practicable and useful’.

To claim this prize, the winner would have to find longitude within half a degree on a journey from England to the West Indies, an accuracy of about thirty miles (50 km). This would be quite a feat for a voyage of several weeks.

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Glossary

Longitude

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