The basic story is that of John Harrison, who invented the marine chronometer that first satisfactorily measured time with sufficient accuracy at sea to allow longitude to be determined. He was awarded a huge prize established by the British Parliament three centuries ago for the first practical solution to the measurement of longitude, The story is told in Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time by Dava Sobel, who was one of the writers of the script for the movie.
It also tells the story of Rupert Gould, a troubled man who restored Harrison's four chronometers in the early 20th century, who also became one of the effective popularizers of science in Britain.
The invention of the compass allowed sailors to know the directions at sea, even in the worst of weather. It was possible to navigate by the stars and know the latitude of a ship -- how far north or south it was. However, there was no adequate solution to the measurement of longitude -- how far east or west the ship might be. If one could measure the difference in time between the location of the ship and a known location -- say the Observatory at Greenwich -- then one could determine longitude.
Unfortunately, this was long before the invention of the telephone or telegraph, so it was not possible to simply send a time signal over the lines. It was also important. Thousands of seamen died each year, either running into land while they thought they were far out at sea, or getting lost at sea and dying of hunger or thirst because they could not renew provisions.
It was possible to measure local noon accurately using a sun dial, at least in good weather. Galileo suggested that it would be possible to measure a "universal time" accurately by observing the moons of Jupiter. With astronomical tables, the times of transepts of the moons could be known, and would be observed simultaneously from wherever they were visible on earth. Indeed, the method was used in terrestrial observation even in the 19th century -- Zebulon Pike, after whom Pike's Peak is named, used the technique in his mapping of the west.
However, measuring astronomical events accurately under all conditions at sea was not feasible, and (as the film shows) defeated the intensive efforts of England's astronomers.
The alternative was to create very accurate clocks. Today we have cheap watchers that are more accurate than the most accurate time pieces available in 1700. The technological progress in clock making in the 16th century had not approached the accuracy needed. John Harrison took on the challenge, and devoted a lifetime to the work. He was a carpenter, and had made wooden clocks for local clients as a young man. Realizing he would need to go to metal movements, he created and built a series of four clocks. The first of them was sufficiently accurate in some tests, but failed to account for centrifugal force in some seaborne conditions. Like the first, the second and third clocks were large, His experience increasing with decades of work, he finally build a chronometer that could be held in the palm of the hand that was both very accurate and very capable of maintaining that accuracy under extreme conditions.
I suspect that Harrison's success was due in part to the advances that were made in mechanical technology in Britain. Better metals were available, and machine tools were being invented and perfected. The movie shows support for Harrison by an important clock maker, one who brought him a trained clock maker to serve as an assistant. I would not take anything away from Harrison as a man totally devoted to his task, who developed and used a wonderful mechanical intuition, but I suspect that his work was made possible by the work of others, much as his accomplishments helped others to extend the watchmakers/clockmakers art.
The movie shows a bit of the difficulties of life at sea in the 17th century, especially as it deals with the voyages of William Harrison. John Harrison's son, as he tested the fourth chronometer.
Lessons from this History
The prize offered by the Parliament for a practical means to measure longitude was 20.000 English pounds, equivalent to millions of today's dollars. History suggests that the prize certainly did stimulate research and development. Fortunately, and probably beyond the politicians ability to predict, the task set in the legislation proved possible.
Did science lead to innovation. Apparently not. The Royal Academy scientists were key members of the Longitude Commission, especially astronomers who had great prestige at the time. The script writers clearly believed that the scientists of the time were prejudiced against clock makers and craftsmen, and that in many ways they hindered the effort to produce marine chronometers; they (naturally?) wanted the solution to come from the science of Astronomy.
Harrison's first chronometer worked quite well on land. It failed to work at sea. Harrison had not understood the movement that it would be subjected to on the unstable ships of the time. (I wonder whether some system to protect it from that motion might have helped, but that was not in his bag of tricks.) The scientists on the Longitude Commission apparently wanted the experiment demonstrating the effectiveness of the chronometer to be replicated, and that today looks quite reasonable. So too does the demonstration that the chronometers could be replicated, retaining their accuracy and stability. The dramatic impact of such conditions on someone who had spent decades developing the clock and who had fulfilled the conditions set by the (non-scientists of) the Parliament was obvious and made the movie emotionally interesting. However, replication and scale-up of production were important.
My wife and I both very much enjoyed the film.
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