Sunday, July 6, 2008

Finding Longitude at Sea

A few years ago I ran across a title on the tv which intrigued me, "Longitude." This movie, or as it were, a tv series put in movie format, was to be shown on A&E. I don't recall precisely, but I probably read the description and knew immediately that I had to watch it, geography and scientific discovery being very interesting subjects for me.

Of course I had the usual suspicion that this movie might well turn out to be just another politically motivated propaganda film intended to sell its audience on ... whatever. But this is not what it turned out to be at all, at least as far as I can tell. Plainly stated, it's a fine movie chronicling the struggle of one Mr. John Harrison to solve the problem of finding longitude at sea. A problem that had long perplexed some of the greatest scientific minds of the era, including Isaac Newton and others.

The image above is of Harrison's first Marine Timepiece (H-1) which, while aboard ship on trial, was placed in a cradle and housed in a protective wooden cube of a box four feet by four feet by four feet in dimension. In other words, though it performed well enough on trial to win the prize money promised to anyone who could solve the longitude problem at sea ( a sum equal to about 6 million dollars in today's terms as I understand it), it was a beast of an instrument too large and cumbersome, and too expensive at the time to replicate, to be of any practicable widespread usage. Also, it had a problem inherent to its design; Harrison, while having painstakingly tested the instrument himself on a rocking boat on a river near his home prior to testing it at sea, had failed to account for the centrifugal motion of a ship while it is turning, and this had caused the timepiece to lose more time, over the course of a relatively short journey at sea, than Harrison was himself comfortable with. Mr. Harrison, you see, was a perfectionist, and he immediately, upon returning safely to England with his timepiece -- something that likely would never have happened had it not performed as well as it did on the return trip where Harrison's readings of the machine showed a disparity of some sixty nautical miles between the ship's actual position and the position at which the crew had put it by dead reckoning, Harrison's calculations being found correct and saving the ship from almost certain destruction (read the book or watch the movie, or both) -- began work on a new design in which he would attempt to solve the problem of centrifugal motion at sea, thus creating a much more reliable marine chronometer than his first attempt, H-1, had proved to be.

The story is very interesting indeed. If you're intrigued, as I am, by such stories of such pioneers of scientific discovery, I highly recommend that you seek out and watch the A&E movie Longitude, as well as the book on which the movie is based and of the same title. The book itself is only 175 pages, so it can be read in a matter of hours. Both the book and the movie are very complimentary of one-another. And they contain the added bonus of showing how a few of Harrison's revolutionary ideas came to be used centuries later for the good and comfort of his fellow man.

(Thanks to my eldest son for purchasing the book and allowing me to borrow it over the weekend. You may have it back now.)