Monthly Archives: November 2001

The Longitude Problem

 

      Until a few days back I had no idea of who John Harrison was and what his contribution to Science was. THis VERITAS is thus inspired by a wonderful program telecast on National Geographic that made me aware of this remarkable genius and the importance of his work.

      An urgent petition reached Parliament on March 25 , 1714 . 

Certain “Captains of Her Majesty’s Ships, Merchants of London , and Commanders of Merchant-men” wanted something done about the day’s most pressing problem in navigation, the problem of longitude.

      In those days Sailors never could accurately know the longitude of their position. They could never know(precisely) how close or how far they were from a particular landmark. This resulted in numerous accidents. For example on October 22, 1707, at the Scilly Isles near the southwestern tip of England, four homebound British warships ran aground and nearly two thousand men lost their lives.

      There were several ways to solve this problem. The two major ones were : the astronomy solution and the clock solution. The astronomy solution relied on the sailors observing the skies(planets, moons stars) to find out their exact longitude. But this solution was not practical for sailors:

A huge telescope is okay on land but imagine a sailor trying to look at jupiter on the deck of a ship tossing voilently at sea. It was not practical at sea and it did not work for sailors.

      The other way to know the longitude was to know the time at your current position, know the time at a standard position( London for example) and to relate the longitude to the time difference. It was known that for every 2 minutes time difference you are half a degree away from the reference point. One could always know the local time at a place:

The sun’s elevation will tell you that accurately. However how would a sailor know the current time at the reference point. Let me tell the readers that this is not such an easy thing. As the Great Newton himself pointed out: “…by reason of the Motion of a Ship, the Variation of Heat and Cold, Wet and Dry, and the Difference of Gravity in Different Latitudes, such a Watch hath never been made.” Remember that in those times clocks were pendulum clocks. Imagine what effect a tossing ship would have on a poor pendulum. :-(.

      Several scientists tried their brains at this problem and failed.

THis list includes Newton , Galileo , Halley , Cassini . This problem was ultimately solved by John Harrison a watchmaker with a love for Science.

      In 1714 the English parliament announced a prize of 20,000 pounds to anyone who could solve the longitude problem within half a degree of latitude or 2 minutes of time. The instrument would be taken on a ship to West Indies and tested there with respect to longitude(time) of London.

        Harrison was twenty-one years old when Parliament announced the prize.  He was born in 1693 at Foulby in Yorkshire, the eldest son of a poor carpenter. Harrison in his spare time studied Physics and Mechanics.

      Harrison worked alone. None of the Great scientists of the time paid any attention to his work. In 1735 Harrison made his first clock called H1. It had not one but two pendulums which were joined to one another. The effect of Gravity on one was compensated by the other. However there was still the problem of pendulums increasing in size due to temperature difference at various places. In 1740 Harrison built H2. But its design was wrong and it failed too. From 1740 to 1759(19 years) Harrison worked on his next clock, the H3. It had two new inventions of Harrison: a strip made of several strips of 2 metals to compensate for expansion due to changing temperatures and a caged roller bearing which reduced friction drastically. Despite that The H3 failed to meet the standards and was discarded.

      Harrison realized that his clocks were too big. In 1755 he started work on a tiny pocket sized watch with all his inventions inside it. H4 was tried in 1761. A ship carried it to Jamica on a 60 day journey . And the watch was accurate to a remarkable 5 seconds. It was a feat! But no one was convinced! Imagine what the top scientists would have felt when they got to know that a simple watchmaker had done what they had considered impossible. So Harrison was not awarded the prize.

He was asked to disclose the secret of his watch. Some scientists thought that the watch was a freak and no other like it could be made. The watch was kept by the Longitude Board and asked a watch maker to replicate it. Harrison was disappointed. He started work on H5. In 1770 Harrison went to the King of England himself. The king himself put H5 to trial and was impressed. The Longitude Board was however reluctant to give Harrison the prize. They only gave him 8000 Pounds. But more importantly he was recognised as having solved the Longitude problem.

      Harrison had worked on the problem for 45 years. He was 80 years old and had crossed swords with the leading lights of his day before solving the problem. In a sense he was a TRUE scientist. He tried untiringly and patiently on what he believed was right. And he did not care what others thought would or would not work . 

 

In the year of Harrison’s death, James Cook sailed again to the Pacific , where he demonstrated beyond any doubt the utility of the chronometer in marine mapping.  Nearly two centuries later , the honored guest at a dinner at 10 Downing Street was an American, who rose to propose a toast to John Harrison.  His invention , the American said, enabled men to explore the Earth with precision and , when most of the Earth had been explored, to dare to build navigation systems for voyages to the Moon .  “You, ladies and gentlemen, started us on our trip .”  The speaker was Neil. A. Armstrong.