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Longitude by Dava Sobel
Transcript of Longitude by Dava Sobel
by Dava Sobel
by Eleanor Lieberman
The Longitude Problem
: The Greatest Nautical Problem of the 17th and 18th century.
During the 16th and 17th century Europe was expanding its knowledge of the world
and exploring across the Atlantic.
Ships used a system of longitude and latitude to find their bearings at sea much like a spherical version of the coordinate plane.
is the the distance North or South from the Equator.
is the distance East or West from a prime meridian
Ships could find their latitude because the base line (0 degrees) was fixed as the Equator. Every next 15 degrees would be 1,000 miles. Sailors could use the sun’s position, length of a day, or guiding stars to find latitude.
Longitude however is is measured in time because the prime meridian is not naturally obvious. It was chosen. Time on the boat and time at the home port were needed to find the longitude. But how did ships know the time at home? Clocks were imprecise and would change rhythm in different pressures and temperatures.
Age of Exploration
the wealth of European nations relied upon the oceans. And yet men at sea were literally dying from lack of knowledge of longitude, so Europe began a long race to discover the longitude.
A popular belief was that we could find longitude in the sky, that is by using stars or the moon. This was a good guess because astronomers were already using the skies for other time related calculations. They used phases of the moon to tell months, and they used solstices and equinoxes to time seasons. Constellations like the little dipper allowed for navigation at night and the sun told the time of day on clear days. The tricky part of longitude is that it requires not just the current time of day, but also the time back at original port to calculate the change in time.
In 1514 German astronomer
used the motion of the moon for location and mapped the path to predict relative positions of ships and a landmark. By choosing one 0° landmark (a city) as a reference point navigators could compare time they observed stars with moon locations at a reference. They could then calculate the difference in hours x15°. This was known as the lunar distance method and the problem was that star positions at exact times were not know.
discovered four satellites of Jupiter called the
. He observed that he could find longitude because the ellipses of the Medicean Stars were predictable enough to set a watch. However the plan was rejected because the Medicean Stars were hard to see and only visible on clear nights.
Other Weird Solutions:
One odd method devised to solve longitude was the
Wounded Dog Theory
of 1687.Sir Kerelem Digby discovered a “
powder of sympathy
” that could supposedly heal people from a distance if applied to an article of clothing of the person. Some unknown genius came up with the idea of using the powder of sympathy to find longitude.
A ship would take with them a wounded dog. Someone back in the port would dip the dog’s bandage in a solution of powder daily at an exact time each day. The dog would yelp in reaction to being “healed” and the ship would know what time it was in port. Needless to say this was not the winning method of longitude…
came up with another odd method. They argued that sailors could estimate longitude by measuring the difference in time between seeing a cannon go off and hearing it because light is faster than sound. They proposed stationing fleets every 600 miles that would regularly shoot cannons to inform other ships of the longitude. However in addition to the unlikeliness of accomplishing such a huge task with many fleets that could be exempt from war, ships were not anchored down enough for precise measurements. The plan did create more interest by governments in facilitating longitude research…
The Longitude Prize
1714 the British Parliament enacted the
Longitude Act of 1714
. The act provided cash rewards for anyone able to solve longitude.
20,000 pounds for within ½ degree of a great circle
15,000 pounds for within 2/3 degree
10,000 pounds for within 1 degree
1 degree may seem like very little, but it actually translates to 60 nautical miles.
To judge longitude methods proposed and finance researchers was the
Board of Longitude
, made of scientists, naval officers, and government officials. At the time it was the world’s #1 research and development of longitude agency.
Sir Isaac Newton
, who was very involved in the longitude problem, was confident that the solution would come from astronomy. When the first British
Astronomer Royal John Flamsteed
, who meticulously charted the skies, refused to publish his data, Newton even stole and printed it. Newton also expressed the possibility of a clock accurate enough to calculate longitude. Newton died in 1727
, born 1693 in Yorkshire, grew up the son of a carpenter and educated himself as a child with books such as Newton’s
and Saunderson’s lectures. Harrison was a clockmaker who eventually solved longitude after a decades long journey.
Harrison made many technological innovations including:
Elimination of oil for gears by creating friction free gears made of wood. Oil would change the rate of the clock depending on temperature.
used alternating strips of metals. Metals contract and expand with heat, so alternating metals could counteract each other’s changes.
counted heartbeats of the clock’s pacemaker worked without friction ensuring even heartbeats. They were never off by more than a second a month.
Harrison's first clock was named Harrison-1, or H-1.
1730 Harrison went before the Board of Longitude. He had many important friends in the Board, such as
Dr. Edmond Halley
who took over the royal observatory after Flamsteed. Harrison then spent the next five years improving upon his previous clocks. His new innovations included:
-brass rods and balances
This new clock was called Harrison-1, or
In 1737 the Board of Longitude met for the first time to inspect H-1. Harrison could have accepted the reward right there, but because Harrison was a perfectionist he asked the Board for more time to create another clock.
In 1741 Harrison presented the Board with
, but again he asked the Board for another commission for a new clock. H-2 did have many new innovations including a smaller size that would be more practical for small ships.
As Harrison created H-3 he become somewhat of a recluse in his workshop.
took 19 years to make because Harrison was a perfectionist.
that acounted for temp changes.
-Balances and springs 2 feet by 1 foot
In my opinon, H-3 is
the most beautiful
of the Harrison clocks.
Although H-3 was a very impressive clock, most people in the 1730s-1760s had faith in the lunar distance method (LDM). Harrison was also not the only inventor invested in solving longitude.
used paired mirrors to find direct measurement of elevations of two bodies to be used in conjunction with Flamsteed’s observations.
By 1742 the LDM depended on three parts.
found positions of stars and the motion of the moon.
found ways to measure critical distances between the moon and sun. (Hadley’s quadrant)
were made by astronomer/mapmaker
to translate instrument readings into longitude positions.
was completed in 1759 and was radically different from previous clocks. H-4 was more like a very large watch than a clock. (“
3 lbs compared to H-3 60 lbs
-It was made of diamonds for reasons unknown.
-Can run for 30 hours straight.
-Unfortunately H-4 if not very tolerant to human touch, largely because Harrison sacrificed friction and oil free clogs for more precise oil and metal cogs.
Despite being very fragile H-4 was a masterpiece and deserved every penny of the Longitude Prize.
The intricate blueprints
that are the background
my project are of H-4.
The Road to Mass Production
The Astronomer Royal of 1765 was
Reverend Nevil Maskelyne
, a strong supporter of the LDM, who was Harrison’s arch rival. He was in charge of testing H-4 for the Longitude Prize. On various occasions Maskelyne (allegedly) forced data saying H-4 was more inaccurate than it actually was, kept H-4 in hazardous conditions in sunlight, dropped and damaged H-4 internally damaging it, and tried in every way possible to prevent Harrison from winning his 20,000 pounds. And he did. After long, complicated disputes involving even George III himself, Harrison ended up receiving 15,000 pounds.
After a decades long journey and a lifetime of obsession, Harrison solved the Longitude problem that had become so famous by its time. Harrison died in 1776 at age 83.
The story does not end there. A watch inspired by Harrison’s designs would be quite expensive and needed to be considerably cheaper for use on most ships.
Thomas Mudge, John Arnold, Thomas Earnshaw
, and a handful of other watchmakers improved upon Harrisons designs, made them cheaper, and mass produced them in fierce competition. Arnold himself popularized the term
to define any marine timekeeper.
Here is a "cheaper", mass
made by John Arnold
from around 1777
Connection #1: Hogarth
Sobel tells that when Harrison was obsessively working on H-3 he was visited by famous London printmaker Hogarth, who portrayed him as insane in a lunatic asylum. I thought that sounded familiar so I went downstairs and saw that my family has that exact print in our house. I have seen Harrison’s image a million times without realizing it was him. What really struck me about this odd coincidence is how Harrison’s legacy has lived on. This book is fairly famous and was made into T.V. series a while ago, but other than that Harrison is an obscure figure in history. I believe this is because of astronomers like Nevil Maskelyne who actively tried to hurt Harrison’s image and credibility as a contender in the longitude competition. Harrison may have won the Longitude Prize, but the astronomers won history.
Connection #2: Curing Cancer
I wanted to think of a problem of the day comparable to the longitude problem of the 18th century. Initially I wanted to go into space travel engineering as it mirrors exploring the ocean on ships. However what made the longitude problem so special was not that it was a challenge science was trying to overcome, because many of those exist at any time. Instead what made the longitude problem so special and interesting was how famous it was in the general public. Because Europe’s economy at the time was trending towards centuries of imperialism, longitude was not only a scientific issue but a social and economic issue. Everybody from ship captains to chocolate consumers had a stake in longitude. That is why I thought that the most applicable connection to today is cancer. Our lifestyle of chemicals is incompatible with our bodies. Every person is at risk. Additionally people using the phrase “curing cancer” and a jokingly way of saying something is impossible. That is exactly how people used the longitude problem. Hopefully in a few centuries students can learn about a time when people thought cancer was incurable.
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