Tuesday, December 1, 2009

Longitude by Dava Sobel


by Dava Sobel

Hardback: 208 pages
Publisher: Walker & Company
First Released: 1995

Source: Bought from library book sale

Back Cover Description:
Anyone alive in the eighteenth century would have known that "the longitude problem" was the thorniest scientific dilemma of the day--and had been for centuries. Lacking the ability to measure their longitude, sailors throughout the great ages of exploration had been literally lost at sea as soon as they lost sight of land. Thousands of lives, and the increasing fortunes of nations, hung on a resolution.

The quest for a solution had occupied scientists and their patrons for the better part of two centuries when, in 1714, England's Parliament upped the ante by offering a king's ransom (£20,000, or approximately $12 million in today's currency) to anyone whose method or device proved successful. Countless quacks weighed in with preposterous suggestions. The scientific establishment of Europe--from Galileo to Sir Issac Newton--had mapped the heavens in both hemispheres in its certain pursuit of a celestial answer. In stark contrast, one man, John Harrison, dared to imagine a mechanical solution--a clock that would keep precise time at sea, something no clock had ever been able to do on land.

Longitude is a dramatic human story of an epic scientific quest and Harrison's forty-year obsession with building his perfect timekeeper, known today as the chronometer. Full of heroism and chicanery, brilliance and the absurd, it is also a fascinating brief history of astronomy, navigation, and clockmaking. Through Dava Sobel's consummate skill, Longitude will open a new window on our world for all who read it.

Longitude is an enjoyable, easy-to-read and understand overview of the events surrounding "the longitude problem," including the various solutions proposed, the political and scientific rivalry involved in the quest for the prize, and the scientific advances that occurred in pursuit of the solution.

The book doesn't really go into depth on how the clock was created. Apparently no one really knows how John Harrison solved each challenge in keeping perfect time while at sea. But we're told the solution found in his finished products even if we don't learn the process of how he got there.

I found very interesting the overview of sea navigation at that time and the scientific advances that came about while in pursuit of the longitude prize money. I also enjoyed learning why Greenwich became the 0 degree longitude line and time-setter for the world.

While I thought the author did a wonderful job describing what the various clocks looked like, I'm glad that pictures of John Harrison and several of his clocks were shown on the front cover of the book. The book doesn't contain pictures or diagrams beyond this. (I didn't mind, though, since the clock innards were apparently confusingly complex so pictures of that wouldn't have been enlightening.)

Overall, I enjoyed this book. I'd recommend this quick read to anyone interested in an overview of the longitude problem, the solutions proposed, and how Harrison's clock eventually came to 'rule the seas.'

If you've read this book, what do you think about it? I'd be honored if you wrote your own opinion of the book in the comments.

Excerpt from Chapter One
As a child, I learned the trick for remembering the difference between latitude and longitude. The latitude lines, the parallels, really do stay parallel to each other as they girdle the globe from the Equator to the poles in a series of shrinking concentric rings. The meridians of longitude go the other way: They loop from the North Pole to the South and back again in great circles of the same size, so they all converge at the ends of the Earth.

Lines of latitude and longitude began crisscrossing our worldview in ancient times, at least three centuries before the birth of Christ. By A.D. 150, the cartographer and astronomer Ptolemy had plotted them on the twenty-seven maps of his first world atlas. Also for this landmark volume, Ptolemy listed all the place names in an index, in alphabetical order, with the latitude and longitude of each--as well as he could gauge them from travelers' reports. Ptolemy himself had only an armchair appreciation of the wider world. A common misconception of his day held that anyone living below the Equator would melt into deformity from the horrible heat.

The Equator marked the zero-degree parallel of latitude for Ptolemy. He did not choose it arbitrarily but took it on higher authority from his predecessors, who had derived it from nature while observing the motions of the heavenly bodies. The sun, moon, and planets pass almost directly overhead at the Equator. Likewise the Tropic of Cancer and the Tropic of Capricorn, two other famous parallels, assume their positions at the sun's command. They mark the northern and southern boundaries of the sun's apparent motion over the course of the year.

Ptolemy was free, however, to lay his prime meridian, the zero-degree longitude line, wherever he liked. He chose to run it through the Fortunate Islands (now called the Canary & Madeira Islands) off the northwest coast of Africa. Later mapmakers moved the prime meridian to the Azores and to the Cape Verde Islands, as well as to Rome, Copenhagen, Jerusalem, St. Petersburg, Pisa, Paris, and Philadelphia, among other places, before it settled down at last in London.

1 comment:

Joy Weese Moll (@joyweesemoll) said...

You might like The Illustrated Longitude. I linked to your review from mine, today