Longitude (2007), the international best seller is the true story of the long scientific quest for the perfect time-keeping instrument, the chronometer. English clockmaker, John Harrison, was the mechanical genius who pioneered, over a forty year period, the portable precision instrument. He accomplished what Isaac Newton said was impossible.
In navigation terms, the chronometer carries the true time from home port to any remote corner of the world. And that’s how the quest began. Christopher Columbus, and any sailor worth his or her salt, can follow a straight path across the Atlantic, sailing the “parallel” (that is parallel to the lines of latitude that travel around the globe). The zero-degree parallel of latitude is fixed by the laws of nature. The problem in navigating is not the latitudes but the longitudes (the lines on the globe that run north to south). The zero-degree meridian of longitude shifts like the sands of time. The measurement of longitude meridians is governed by time.
To learn one’s longitude at sea, one needs to know what time it is aboard ship, and also know the time at the home port or another place of known longitude – at that very same moment. Knowledge of the two times would enable a navigator to convert the hour difference into a geographical separation. Pendulum clocks of the time were useless at sea. As more ships were exploring new territories, waging war, or trading goods between countries, untold numbers of sailors died when their destinations suddenly loomed in front of them and took them by rocky surprise.
The British Parliament set up a Longitude Act in 1714, offering a king’s ransom for a “practical and useful” means of determining longitude. John Harrison collected his reward in 1773 after forty years of single-minded effort. Hence this is more than a story of an invention. It is even more than astronomy, navigation and clock-making. It is a fascinating account of political intrigue, international warfare, academic back-biting and rivalry, scientific revolution, and economic upheaval.
Renowned astronomers such as Galileo Galilei, Jean Dominique Cassini, Christiaan Huygens, Sir Isaac Newton, and Edmund Halley (of comet fame) all attempted the great puzzle amid palatial observatories in Paris, London and Berlin, believing that the clockwork universe would reveal the answer. It took a person with no formal education or apprenticeship to tackle the problem from a mechanical perspective – making a virtually friction-free clock that required no lubrication and no cleaning, and was impervious to rust. But more essentially, the chronometer kept its parts moving perfectly balanced in relation to one another, regardless of how the world pitched or tossed about on the high seas. He disregarded the pendulum and combined different metals in such a way that when one component expanded or contracted with changes in the temperature, the other counteracted the change and kept the clock’s rate constant.
Dava Sobel relates history and science in a brilliant, short read that is sure to interest both the scientific and non-scientific readers.
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