Monday, January 15, 2007
Meaurement of Genius
Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time, by Dava Sobel, Read by Kate Reading, Books on Tape, Inc., 2005
Once upon a time, the speed of a ship sailing on the ocean was determined like this. A log affixed to a rope of a known length was dropped out the back of the ship. The time it took for the rope to grow taut was calculated to give approximate speed. This was known as dead reckoning.
This, to put it gently, was a wildly variable method of calculation. But wait, it gets worse. In order to the determine the ship’s longitude, this “speed” was then entered into an even more complicated algorithm involving ocean currents as mapped out by previous sailors, the speed and direction of the wind, and the length of time already en route.
Is it any wonder long ocean voyages were wracked with scurvy as weeks were tacked on to sailing time as miscalculations piled up? Or that foundering on land was a commonplace? In perhaps the most well known incident, Admiral Shovell ran much his fleet aground at the Isles of Scilly and at least 1400 sailors were killed. You see, they were in a fog and believed themselves in the middle of the ocean.
Clearly this was a problem. Latitude, the imaginary bands circling the planet parallel to the equator, were easy to calculate. The altitude of the northern pole star was equal to your latitude. Simple. To get a fix on your location, though, you needed longitude.
The kingdoms of the time recognized this seriousness and many set up various prizes and contests in order to crack the nut of longitude. To demonstrate the seriousness and practicality of determining longitude, one need consider that astronomical observatories were established as star gazers tried to call upon the clockwork universe to assist them.
A prize established by Parliament (£10,000 for calculating a ship’s longitude within one degree; £15,000, for within 40 minutes; and £20,000 for under half a degree) was worth several million dollars in today’s money. Likewise the King of Spain offered a lifetime pension of ducats for the solution.
The problem was so difficult and the prizes and glory so great that everyone got involved even architects such as Christopher Wren and biologist polymath Robert Hooke. Astronomers such as Galileo worked on the problem, using complicated observations of the eclipses of the moons of Jupiter. He even created a gas-mask like helmet with a telescope attachment to one eye-piece that would allow you to see Jupiter’s moons, but keeping the satellites in the eyepiece proved a near impossibility. On land.
Such a prize, as well as the ability to grant money to push promising theories into practical application, brought out not only every scientist but numerous cranks as well. Perhaps the strangest idea involved a “sympathy powder” that was supposed to help heal wounds through sympathetic scientific magic. The suggestion was to wound a dog, put it on board, then at noon at the prime meridian in London dump powder on the dog’s discarded bandage. When it yelped aboard ship that meant it was twelve o’clock back in Jolly Old England.
John Harrison, the eventual winner and solver of the solution, was himself a bit of a crank, a perfectionist and clockwork innovator who made remarkably accurate time pieces. One of the earliest problems he solved as clockmaker were changes in pendulum length (and the resulting inaccuracies) due to the expansion and contraction of the metals from exposure to shifting temperatures. The gridiron pendulum, made up of differing metals whose relative response to temperature fluctuations canceled each other out, was one of the necessary ingredients for any chronometer that would sail across the ocean.
A joiner by trade, he also experimented with a variety of woods, in one instance constructing a clock whose oily wood resin resulted in reduced friction and eliminated the need to lubricate its mechanisms. He also created what’s known as the grasshopper escapement, a frictionless mechanism that regulated the release of a clock’s wind up power, allowing for uniform measurement.
His perfectionism and his aggravation at his inability to make something quite up to his own specifications put off the determination of true longitude, as he would likely have won the prize had he gone with his first or second sea clock — and he would have found a more receptive audience in the board judging the prize.
At the time of Harrison’s first and second clocks, H1 & H2, Edmond Halley, the Astronomer Royal, was his friend on the Board of Longitude, the government body who judged means of measuring longitude as well as disbursed funds toward promising areas of research. Halley’s position on the Board allowed Harrison’s ideas a receptive ear despite widespread belief in the scientific community that no clock would ever attain sufficient accuracy. Even Sir Isaac Newton doubted Harrison’s abilities in this specific realm.
Upon Halley’s death, his successor Astronomer Royals, Dr. James Bradley and then Nathaniel Bliss, had little acceptance that such a solution, created by a non-scientist country bumpkin, could possibly resolve a problem that had endured for centuries. Both were betting on the astronomical solution to longitude known as the Lunar Distance Method, the one favored by most astronomers (and the research field that promised the most additional funding for observatory construction).
The lunar method consisted of measuring the angle of the moon’s center from the sun or a bright star. With lunar distance, a nautical almanac of celestial bodies’ movement and position, a sextant, and reams of calculations and corrections, longitude could be worked out. As long as the moon remained visible.
Harrison’s trials in gaining not only a hearing for his timepiece method, but funding, as well as the travails the Board of Longitude put him through is the stuff of Dava Sobel’s enthralling history of the longitude race, simply titled Longitude. Insiders on the Board frequently altered the terms of the contracts Harrison entered into and delayed declaration of his success repeatedly. Stipulations were added, Parliament itself rewrote its prize legislation, and Harrison’s chronometers were sent hither and yon across the ocean in test after test.
Sobel writes all this with a fast paced flair for storytelling and a knack for pre-digesting the trickier aspects of the science of the solutions and the celestial calculations of the day and presenting readers with a comprehensible thumbnail sketch. It was maddening listening to how astronomically inclined judges pooh-poohed alternate theories while their own encountered setback after difficulty after inaccuracy. Harrison seemed to bear up remarkably well under the frustrations he must surely have felt, including at one point the confiscation of his watches and blueprints by Act of Parliament.
Attesting to his watches’ accuracy was none other that national hero James Cook who filled his captain’s log with praises of the timepiece. The Board were unimpressed and it took Harrison’s petitioning King George III, who threatened Parliament, to get the prize awarded. The King, himself a science buff, tested the watch over ten days and only found it only inaccurate by four and a half seconds.
It is no exaggeration to state that the establishment of the British Empire rests greatly on Harrison’s chronometer. Accuracy in measurement led to a British dominance of the oceans which partly explains why to this day we still use Greenwich Mean Time (now known as Universal Time) as the planet’s official time. Along the way toward resolution of the longitude puzzle many other things were calculated such as the weight of the earth and the speed of light. It was perhaps the impetus for some of the greatest discoveries of the age outside of longitude itself.
Besides among history buffs, maritime museum fans, and archivists of timepieces, John Harrison’s name isn’t as widely known as it should be. While his specific accomplishment was limited to the creation of something so common we take it for granted these days, an accurate means for the measurement of time, it was the element of precision that gave us time as we know it now.
Reader Kate Reading does a fine job of delivering the material in well-modulated tones, keeping her voice lively and clear. Editorially, she charms us by her sympathies for Harrsion, her inflection occasionally rising with indignation on the part of the clock-maker at his rude handling by the Board of Longitude.
Posted by The Critic at 1/15/2007 02:03:00 AM