Longitude

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In the ’90s, most seafaring vessels switched over to satellite-based computerized navigation systems. But the episodic nature of the chapters, and the abbreviated way she communicates the stories of the testing of H–3, H–4, etc. Si tenemos en cuenta que circunvalar la Tierra supone 360º, que se dividen en 24 meridianos de longitud, obtenemos una separación entre ellos de 15º, calculándose cada grado en minutos. I did start to feel like the book needed some diagrams or pictures, because it got really difficult forming mental images of such obscure and complex devices.

After a decades long struggle, an elderly Harrison was awarded the money by Parliament, though not the prize. But accurately measuring their current longitude was an entirely different case, as the longitudinal lines loop from the North Pole to the South Pole and back again in great circles, which converge at the ends of the earth. This is a page turner that makes what could be a mire of mechanical and mathematical detail simple, easy to follow and enjoy by anyone, whether they are confirmed landlubbers or have a previous interest in the sea.Full of heroism and chicanery, brilliance and the absurd, LONGITUDE is also a fascinating brief history of astronomy, navigation and clockmaking.

But for centuries, where to set 0° longitude was a political selection, so it had bounced around from the Canary Islands (Ptolemy's choice) to Rome to Jerusalem and to many more locations. For a very short book—175 pages of text, and they’re small pages—this little work of history packs in a decent amount of information. A well-timed bomb, exploding 6,440 feet in the air (the limit of available technology), could be seen from a distance of 100 miles. Background: Latitude lines are the parallel lines that circle the globe above and below the equator, and any sailor could figure out his latitude by measuring the length of the day or looking at the angle of the sun or the north star. In the Longitude Act of 1714, the British Parliament offered a prize of 20,000 pounds (equivalent to several million dollars today) to anyone who found a "practicable and useful" means of determining longitude.She holds honorary doctor of letters degrees from the University of Bath, in England, and Middlebury College, Vermont, both awarded in 2002. It's surprising to realize that it was not until the middle of the 18th century, when Jon Harrison invented the chronometer—"a clock that would carry the true time from the home port, like an eternal flame, to any remote corner of the world"—that sailors could count on finding their way by reliable devices.

Since it is an angular measurement, which is based on time, the sailors had to have access to two different times - the current time on-board the vessel and the time at a known and pre-selected longitudinal location – at the same instance for calculating the hour differences to work out the geographical separation and the longitude. At the heart of Dava Sobel's fascinating brief history of astronomy, navigation and horology stands the figure of John Harrison, self-taught Yorkshire clockmaker, and his forty-year obsession with building the perfect timekeeper. Other less elegant or accurate solutions to the longitude problem became mere footnotes in Harrison’s journey, as did Neville Maskelyne. One can easily enough navigate from north to south, or along latitude, with astronomical knowledge and a sextant. On the other hand, the book is quite brief, and the author seems overly enamored of Harrison, though she doesn’t actually refer to him as a “lone genius” as stated in the subtitle (he seems to have collaborated as much as anyone else at the time, when there was less apparent need for lab assistants than today).

Harrison spent four decades perfecting a watch that would earn him compensation from Parliament and longitude rewards thanks to the recognition and influence of King George III of Great Britain. If the proposed signal guns were loaded with cannon shells that shot more than a mile high into the air, and exploded there, sailors could time the delay between seeing the fireball and hearing its big bang. Shipboard conditions, with constant motion, dampness, and temperatures ranging from sweltering tropics to arctic gales, made the problem seem impossible. Era tan importante para los países encontrar una solución al problema de la longitud, que les hacía perder barcos, mercancías, hombres y dinero, que decidieron poner una recompensa a aquél que diese una solución lo más exacta posible. Longitude from Dava Sobel is a fascinating account of how a virtually unknown watchmaker named John Harrison conquered one of the oldest and thorniest problems surrounding the ocean voyages - the problem of accurately measuring longitude -, which stumped even the best of scientific minds for centuries.

This concise and engaging chronicle of an innovative engineering deed covers a lot of details on the history, science and politics, which led to this invention and is a recommended read for anyone who is interested in maritime history and science.

Navigational accuracy was paramount, yet the elusive concept of determining longitude plagued sailors and explorers, leading to countless shipwrecks and lost lives. Anyone alive in the 18th century would have known that ‘the longitude problem’ was the thorniest scientific dilemma of the day – and had been for centuries.