Tuttavia il tempo si rifiuta di essere imbottigliato come il genio della fiaba che viene ficcato dentro una lampada. Alle 13 in punto la palla rossa viene issata sulla cima del pennone. E di un orologiaio, narra questo libro di Dava Sobel, tracciando i contorni di una figura, John Harrison, a cui tutta la storia della navigazione dovrebbe fare un monumento. Ma per fare il punto nautico mancava egualmente un dato essenziale: la longitudine.
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Shelves: history , science , biography 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. A fascinating problem It was Ptolemy in Geographia, written in the 2nd century, who contributed the concept of a co-ordinate system based on the imaginary lines of latitude and longitude, for 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.
With these imaginary lines he bought a new light in to the maritime explorations and map-making methods of his time. The sailors while at the ocean found it pretty straightforward to find their current latitude - which is drawn parallel to each other while girdling the globe — by measuring the height of the sun or any known celestial bodies.
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. 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.
From a modern viewpoint with our easy-to-carry accurate time-telling devices and instant communication this problem, which a sailor faced in finding the exact time at two different locations, may feel far-fetched.
But a sailor in the middle of an ocean pre-dating 18th century only had limited resources in the form of either a pendulum driven clock which was not at all reliable — as the factors like gravity, motion of the vessel, temperature and atmospheric pressure affected the pendulum and there by the time — or by comparing positions of moon or planets like Mars with their anticipatory positions in working out the longitudinal values; both these methods were crude with a high level of inaccuracy.
Since the days of Ptolemy, legendary scientific and exploratory minds like Amarigo Vespucci, Sir Issac Newton and Galileo Galilei did a lot of research into this matter but it took sixteen more centuries for mankind to finally invent a reliable solution for this problem. This disaster and huge protest from the merchants and seamen resulted in the formation of a parliamentary committee for finding a practical solution for the longitude problem.
Dava Sobel covers this formation of the committee and the announcement of the reward in detail. But, by reason of the motion of the Ship, the Variation of Heat and Cold, Wet and Dry, and the Difference of Gravity in different Latitudes, such a watch hath not yet been made. But when the Longitude at sea is once lost, it cannot be found again by any watch.
At the same time another less known figure; a skilled watchmaker from Lincolnshire named John Harrison who was stimulated by the scientific and the monetary factors surrounding this riddle decided to find a solution of his own. His handmade sea-clocks - which are elaborate pieces of engineering marvels and still in display in working condition at the Royal Observatory, Greenwich, England - gave the world the first reliable method for measuring the longitude.
Dava Sobel records the background and each step of this pioneering invention in an easy to read form, by guiding the reader through a tumultuous story of the sheer determination and relentless pursuit for perfection from a self made man and the obstructions, unkempt promises and villainy he had to face from some of his jealous contemporaries.
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.
The illustrated edition is highly recommended.
Longitudine. Come un genio solitario cambiò la storia della navigazione