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Longitude (book)
Encyclopedia
Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time is a best-selling book by Dava Sobel
about John Harrison
, an 18th century clockmaker
who created the first clock (chronometer
) sufficiently accurate to be used to determine longitude
at sea—an important development in navigation
. The book was made into a television series entitled Longitude
. In 1998, The Illustrated Longitude was published, supplementing the earlier text with 180 images of characters, events, instruments, maps and publications.
Determining latitude
was relatively easy in that it could be found from the altitude of the sun at noon with the aid of a table giving the sun's declination for the day. For longitude, early ocean navigators had to rely on dead reckoning
. This was inaccurate on long voyages out of sight of land and these voyages sometimes ended in tragedy as a result.
In order to avoid problems with not knowing one's position accurately, navigators have, where possible, relied on taking advantage of their knowledge of latitude. They would sail to the latitude of their destination, turn toward their destination and follow a line of constant latitude. This was known as running down a westing (if westbound, easting otherwise). This prevented a ship from taking the most direct route (a great circle
) or a route with the most favourable winds and currents, extending the voyage by days or even weeks. This increased the likelihood of short rations, scurvy
or starvation leading to poor health or even death for members of the crew and resultant risk to the ship.
Errors in navigation have also resulted in shipwrecks. Motivated by a number of maritime disasters attributable to serious errors in reckoning position at sea, particularly spectacular disasters such as the Scilly naval disaster of 1707
which took Admiral Sir Cloudesley Shovell
and his fleet, the British government established the Board of Longitude
in 1714.
The prizes were to be awarded to the first person to demonstrate a practical method for determining the longitude of a ship at sea. Each prize, in increasing amounts, were for solutions of increasing accuracy. These prizes, worth millions of dollars in today's currency, motivated many to search for a solution.
Britain was not alone in the desire to solve the problem. France's King Louis XIV founded the Académie Royale des Sciences in 1666. It was charged with, among a range of scientific activities, the improvement of maps and sailing charts and advancement of the science of navigation. From 1715, the Académie offered one of the two Prix Rouillés specifically for navigation. Spain's Philip II
offered a prize for the discovery of a solution to the problem of the longitude in 1567; Philip III
increased the prize in 1598. Holland added to the effort with a prize offered in 1636. Navigators and scientists in most European countries were aware of the problem and were involved in finding the solution. Due to the international effort in solving the problem and the scale of the enterprise, it represents one of the largest scientific endeavours in history.
As Dava Sobel explains, "to know one's longitude at sea, one needs to know what time it is aboard ship and also the time at the home port or another place of known longitude-at that very same moment. The two clock times enable the navigator to convert the hour difference into geographical separation. Since the earth takes 24 hours to revolve 360 degrees, one hour marks 1/24 of a revolution or 15 degrees. And so each hour's time difference between the ship and starting point marks a progress of fifteen degrees of longitude to the east or west. Every day at sea, when the navigator resets his ships clock to local noon when the sun reaches its highest point in the sky, and then consults the home port clock, every hour's discrepancy between them translates into another fifteen degrees of longitude. One degree of longitude equals four minutes of time the world over, although in terms of distance, one degree shrinks from 60.15 nautical miles or 111 km [Earth's circumference being: 21,653.521 nautical miles, or 24,901.55 statute miles at the Equator], to virtually nothing at the poles. Precise knowledge of the hour in two different places at once - a longitude prerequisite so easily accessible today from any pair of cheap wristwatches - was utterly unattainable up to and including the era of pendulum clocks. On the deck of a rolling ship such clocks would slow down, or speed up, or stop running altogether. Normal changes of temperature encountered en route from a cold country of origin to a tropical trade zone thinned or thickened a clocks lubricating oil and made its metal parts expand or contract with equally disastrous results. A rise or fall in barometer pressure, or the subtle variations in the Earth's gravity from one latitude to another, could also cause a clock to gain or lose time."http://www.sailtexas.com/long.html
Before the 18th century ocean navigators could not find an accurate way of determining longitude. This failure caused ships to miss their destination, many times crashing into rocks and killing their crews. A practical solution came from a simple carpenter, John Harrison, who solved one of the most difficult problems of his time by creating an accurate chronometer. The best scientists of the time, including Isaac Newton, thought it impossible. Harrison spent four decades perfecting a watch that would ultimately earn him the prize established by the Longitude Act of 1714, thanks to the recognition and influence of King George III of England.http://www.nobeliefs.com/sobel.htm
In recognition of Longitude Sobel was named a fellow of the American Geographical Society
.
Dava Sobel
Dava Sobel is a writer of popular expositions of scientific topics. She graduated from the Bronx High School of Science and Binghamton University...
about John Harrison
John Harrison
John Harrison was a self-educated English clockmaker. He invented the marine chronometer, a long-sought device in solving the problem of establishing the East-West position or longitude of a ship at sea, thus revolutionising and extending the possibility of safe long distance sea travel in the Age...
, an 18th century clockmaker
Clockmaker
A clockmaker is an artisan who makes and repairs clocks. Since almost all clocks are now factory-made, most modern clockmakers only repair clocks. Modern clockmakers may be employed by jewellers, antique shops, and places devoted strictly to repairing clocks and watches...
who created the first clock (chronometer
Chronometer
Chronometer may refer to:* Chronometer watch, a watch tested and certified to meet certain precision standards* Hydrochronometer, a water clock* Marine chronometer, a timekeeper used for celestial navigation...
) sufficiently accurate to be used to determine longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....
at sea—an important development in navigation
Navigation
Navigation is the process of monitoring and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks...
. The book was made into a television series entitled Longitude
Longitude (TV serial)
Longitude is a 2000 TV drama produced by Granada Productions and the A&E Network for Channel 4, first broadcast in 2000 in the UK on Channel 4 and the US on A&E. It is an adaptation of the 1997 book of the same title by Dava Sobel...
. In 1998, The Illustrated Longitude was published, supplementing the earlier text with 180 images of characters, events, instruments, maps and publications.
Problem of longitude
Determining longitude on land was fairly easy compared to the task at sea. A stable surface to work from, a comfortable location to live in while performing the work and the ability to repeat determinations over time made for great accuracy. Whatever could be discovered from solving the problem at sea would only improve the determination of longitude on land.Determining latitude
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...
was relatively easy in that it could be found from the altitude of the sun at noon with the aid of a table giving the sun's declination for the day. For longitude, early ocean navigators had to rely on dead reckoning
Dead reckoning
In navigation, dead reckoning is the process of calculating one's current position by using a previously determined position, or fix, and advancing that position based upon known or estimated speeds over elapsed time, and course...
. This was inaccurate on long voyages out of sight of land and these voyages sometimes ended in tragedy as a result.
In order to avoid problems with not knowing one's position accurately, navigators have, where possible, relied on taking advantage of their knowledge of latitude. They would sail to the latitude of their destination, turn toward their destination and follow a line of constant latitude. This was known as running down a westing (if westbound, easting otherwise). This prevented a ship from taking the most direct route (a great circle
Great circle
A great circle, also known as a Riemannian circle, of a sphere is the intersection of the sphere and a plane which passes through the center point of the sphere, as opposed to a general circle of a sphere where the plane is not required to pass through the center...
) or a route with the most favourable winds and currents, extending the voyage by days or even weeks. This increased the likelihood of short rations, scurvy
Scurvy
Scurvy is a disease resulting from a deficiency of vitamin C, which is required for the synthesis of collagen in humans. The chemical name for vitamin C, ascorbic acid, is derived from the Latin name of scurvy, scorbutus, which also provides the adjective scorbutic...
or starvation leading to poor health or even death for members of the crew and resultant risk to the ship.
Errors in navigation have also resulted in shipwrecks. Motivated by a number of maritime disasters attributable to serious errors in reckoning position at sea, particularly spectacular disasters such as the Scilly naval disaster of 1707
Scilly naval disaster of 1707
Scilly naval disaster of 1707 is an umbrella term for the events of 22 October 1707 that led to the sinking of a British naval fleet off the Isles of Scilly. With four large ships and more than 1,400 sailors lost in stormy weather, it was one of the greatest maritime disasters in the history of...
which took Admiral Sir Cloudesley Shovell
Cloudesley Shovell
Admiral of the Fleet Sir Cloudesley Shovell , was an English naval officer. Rising through the ranks and fighting in many of the important battles of the late 17th and early 18th centuries, he became a popular British hero, whose celebrated career was brought to an end in a disastrous shipwreck in...
and his fleet, the British government established the Board of Longitude
Board of Longitude
The Board of Longitude was the popular name for the Commissioners for the Discovery of the Longitude at Sea. It was a British Government body formed in 1714 to administer a scheme of prizes intended to encourage innovators to solve the problem of finding longitude at sea.-Origins:Navigators and...
in 1714.
The prizes were to be awarded to the first person to demonstrate a practical method for determining the longitude of a ship at sea. Each prize, in increasing amounts, were for solutions of increasing accuracy. These prizes, worth millions of dollars in today's currency, motivated many to search for a solution.
Britain was not alone in the desire to solve the problem. France's King Louis XIV founded the Académie Royale des Sciences in 1666. It was charged with, among a range of scientific activities, the improvement of maps and sailing charts and advancement of the science of navigation. From 1715, the Académie offered one of the two Prix Rouillés specifically for navigation. Spain's Philip II
Philip II of Spain
Philip II was King of Spain, Portugal, Naples, Sicily, and, while married to Mary I, King of England and Ireland. He was lord of the Seventeen Provinces from 1556 until 1581, holding various titles for the individual territories such as duke or count....
offered a prize for the discovery of a solution to the problem of the longitude in 1567; Philip III
Philip III of Spain
Philip III , also known as Philip the Pious, was the King of Spain and King of Portugal and the Algarves, where he ruled as Philip II , from 1598 until his death...
increased the prize in 1598. Holland added to the effort with a prize offered in 1636. Navigators and scientists in most European countries were aware of the problem and were involved in finding the solution. Due to the international effort in solving the problem and the scale of the enterprise, it represents one of the largest scientific endeavours in history.
Knowing Longitude
Recognition
- British Book of the Year, 1997
- Modern Library 100 Best Nonfiction, Readers List (26th)
- American Academy of Arts and Letters Harold D. Vursell Memorial Award, 1999
- Le Prix Faubert du Coton
- Il Premio del Mare Circeo
- Royal Society Prizes for Science Books, 1997 (Shortlisted)
- American Library AssociationAmerican Library AssociationThe American Library Association is a non-profit organization based in the United States that promotes libraries and library education internationally. It is the oldest and largest library association in the world, with more than 62,000 members....
Non-fiction Outstanding Books for the College Bound and Lifelong Learners, 1999 - American Library AssociationAmerican Library AssociationThe American Library Association is a non-profit organization based in the United States that promotes libraries and library education internationally. It is the oldest and largest library association in the world, with more than 62,000 members....
Outstanding Books for the College Bound and Lifelong Learners, Science and Technology, 2004
In recognition of Longitude Sobel was named a fellow of the American Geographical Society
American Geographical Society
The American Geographical Society is an organization of professional geographers, founded in 1851 in New York City. Most fellows of the society are Americans, but among them have always been a significant number of fellows from around the world...
.