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Longitude is a sheer delight of a popular history of technology. Up until the 18th century, half of navigation was done by chance. Finding latitude is easy, simply take the angle between the horizon of the sun at noon or Polaris at night, adjust for the date, and you know where you are relative to the equator. But longitude is a different matter. Ships wandered in the great oceans, crews riddled with scurvy, or crashed into rising cliffs. The British government offered a prize of 20,000 Pounds, equivalent to millions of dollars today, for a solution to the longitude problem. Meanwhile, finding longitude was ridiculed as an impossible quest, on par with perpetual motion and squaring the circle.
Serious approaches to longitude centered on time. If you knew what time was at some fixed point, a home port, and could compare it to local time, then 1 hour of difference in time corresponded to 15 degrees of longitude. But keeping track of the time simply was not possible with contemporary clocks which gained or lost whole minutes in an hour on land. Shipboard conditions, with constant motion, dampness, and temperatures ranging from sweltering tropics to arctic gales, made the problem seem impossible.
Sobel follows the story of the man who cracked it, a self-taught clockmaker from Yorkshire named John Harrison. Harrison developed the first chronometer, a clock which kept accuracy to within seconds under harsh maritime conditions. But Harrison's triumph was bedeviled by official opposition. The men who made up the longitude board were mostly astronomers, and they believed that the problem must be solved by reference to a celestial clock, either eclipses of the moons of Jupiter, or the position of the moon relative to major stars. British astronomer royal Nevil Maskelyne refused to accept a 'mere mechanic' had cracked the problem, instead preferring a method based on the moon.
After a decades long struggle, an elderly Harrison was awarded the money by Parliament, though not the prize. Chronometers were very expensive, ten times as expensive as an almanac of lunar ephemera, and navigators used lunar methods for decades. Harrison became the victor in the eyes of history. His chronometers are treasured artifacts. GPS, that omnipresent locator, relies on satellites and ultra-precise clocks. Longitude captures the spirit of the great age of exploration, and the taming of the leviathans in the blue spaces on the maps, in the best possible way.
Serious approaches to longitude centered on time. If you knew what time was at some fixed point, a home port, and could compare it to local time, then 1 hour of difference in time corresponded to 15 degrees of longitude. But keeping track of the time simply was not possible with contemporary clocks which gained or lost whole minutes in an hour on land. Shipboard conditions, with constant motion, dampness, and temperatures ranging from sweltering tropics to arctic gales, made the problem seem impossible.
Sobel follows the story of the man who cracked it, a self-taught clockmaker from Yorkshire named John Harrison. Harrison developed the first chronometer, a clock which kept accuracy to within seconds under harsh maritime conditions. But Harrison's triumph was bedeviled by official opposition. The men who made up the longitude board were mostly astronomers, and they believed that the problem must be solved by reference to a celestial clock, either eclipses of the moons of Jupiter, or the position of the moon relative to major stars. British astronomer royal Nevil Maskelyne refused to accept a 'mere mechanic' had cracked the problem, instead preferring a method based on the moon.
After a decades long struggle, an elderly Harrison was awarded the money by Parliament, though not the prize. Chronometers were very expensive, ten times as expensive as an almanac of lunar ephemera, and navigators used lunar methods for decades. Harrison became the victor in the eyes of history. His chronometers are treasured artifacts. GPS, that omnipresent locator, relies on satellites and ultra-precise clocks. Longitude captures the spirit of the great age of exploration, and the taming of the leviathans in the blue spaces on the maps, in the best possible way.