Living in London

On Friday we we went to Greenwich (pronounced Gren-ich), a delightful little village in Southeast London on the Thames. We took a guided tour that started at the Cutty Sark, and took us by some of the highlights of Greenwich. We saw the Old Royal Naval College, the Painted Hall and the National Maritime Museum. It was one of the most interesting sites we have visited.

The highlight of the day was visiting the Royal Observatory, where Greenwich Mean Time is marked. It turns out that, until the 1750's, navigation at sea was a problem. Navigators could determine their latitude (how for north or south) by measuring the angle of the sun in the sky. But they had no way to determine their longitude (how far east and west). In one incident in 1707, Admiral Cloudsley Shovel and his fleet were afloat in fog and thought they were in the middle of the ocean; they ran aground and over 2000 men died.


The first approach to address the problem was to create a detailed catalog of all the stars in the heavens including their precise locations at exact times. The idea was that ship captains would take measurements of stars in the night sky and determine their longitude from the star catalog. The Royal Observatory was commissioned 1n 1675 to create the catolog. Later, with success elusive, the British Government created the Longitude Prize in 1714 to encourage a solution.


Unfortunately, creating such a detailed account of the heavens turned out to be more difficult than expected. After nearly 100 years the catalog was still not ready, the Longitude prize was unclaimed, and sailers were still struggling to navigate the seas. John Harrison, an English clock maker, had a better idea. His plan was to make a chronometer that would be sufficiently accurate at sea. The clock would be set to a specific time in a specific location (say, Greenwich, for example). Using the sun, the sailor could determine high-noon by noting when the sun reached its highest point in the sky. The time difference between Greenwich and their current location would allow the sailor to determine their longitude.


[It works like this: there are 360 degrees of longitude in the globe. Since there are 24 hours in a day, each hour difference between two locations represents 15 degrees of longitude. By noting high-noon at their current location and calculating the difference in time between the ship and Greenwich, the sailor would have an accurate reading for longitude.]


However, creating a clock that would keep accurate time on a ship was not an easy task. Most clocks of the day were based on pendulums and these did not work will in the tossing seas. It took Harris more than 30 years to perfect the design that was finally adopted for wide use.


Accurate navigation made global seafaring possible. The rapid expansion of the British Empire quickly followed. Soon there would be British Colonies in so many parts of the word that it would be said that "the sun never sets on the British Empire." Learning how Britain conquered the world with their navy by figuring out how to measure longitude was fascinating. We were with our friends from California, Steve and Cynthia, and we will definitely revisit this site again.


-HrH