When in
London recently I was lucky
enough to see the exhibition “Ships, Clocks & Stars: The Quest for
Longitude” at the
National Maritime Museum in Greenwich. The
exhibition was put on to mark the 300th anniversary of the passing of the
Longitude Act in July 1714.
It shows the
historical story of the journey to establish longitude, the east-west position
at sea.
The quest for longitude was a huge challenge at the time and
rewards of up to £20,000 were offered to anyone who could solve this mystery.
Some of the world’s greatest scientists of the 17th and 18th
century worked on a solution. These included Galileo, Isaac Newton, Captain
Cook and John Harrison.
The confirmation of longitude saved ships from terrible fates
such as shipwreck and starvation. Discovery of Longitude revolutionized and
extended the possibility of safe long-distance sea travel. Even
centuries later, the science that was discovered during this quest still has an
affect on modern communication and travel. The development of GPS, mobile
phones and international time zones all rely to some extent on the information
discovered at that time.
Two of the highlights of this exhibition include
All
five of
John Harrison’s legendary timekeepers which were the first to
allow accurate timekeeping at sea.
John Harrison's first sea clock H1
John Harrison's clock H2
Harrison's "Sea Watch" No.1 (H4), with winding crank
Harrison's Chronometer H5
John Harrison
invented the first marine chronometer which helped to solve the problem of
establishing the East-West position or longitude of a ship at sea. These watches
are the forbears of modern chronometers as we know them today
1767 portrait of John Harrison
So why was discovering Longitude so important and why was
accurate time so necessary? Longitude fixes the location of a place on Earth
east or west of a north-south line called the prime meridian. It is recorded as
an angular measurement ranging from 0° at the prime meridian to +180° eastward
and −180° westward. A ship's east-west position was essential when approaching
land. After a long sea voyage, cumulative errors in dead reckoning often
resulted in shipwrecks and loss of life.
Preventing these disasters became essential in Harrison's lifetime because this was a period when both
trade and navigational exploits were becoming more common. Earlier methods to determine longitude during a long sea
voyage were difficult because of the problems in accurately estimating the time
at any given place. These earlier methods relied on astronomical observations,
but this too was fraught with problems because it relied on the predictable
nature of the movement different heavenly bodies.
The self taught Harrison solved the problem
by producing a clock which could be relied upon to keep the time of the given
place. Against all odds, he developed a clock which was not affected by
variations in temperature, pressure or humidity and which stayed accurate over
long time intervals, resisted corrosion in salt air, and was able to function
on board a constantly-moving ship.
Harrison’s work in
developing a clock which could work accurately under these harsh conditions was
an amazing feat. Many leading scientists of the time, including Issac Newton
were doubtful that it could ever be achieved.
However there is some evidence that Harrison did not work alone "Lone, longitude genius may have had help" But whether he had help or not ,we of our generation are pleased he was so resourceful
because his work was the forerunner for the
wristwatches, clocks, chronometers
and GPS systems available to us today.
This exhibition is a must see for all the
Horology Enthusiasts out there who just love to see a well made antique clock and learn a bit of history at the same time.
