The accurate determination of a ship’s position on the open sea challenged the greatest minds of the 15th through the 18th centuries.
Latitude was easily determined by measuring the sun’s local maximum observed height at noon. Referring to navigation tables specifically for the day’s date, and making minor corrections, the navigator could calculate the latitude of the ship quite precisely.
Longitude however, remained a mystery. Prominent scientists (including Galileo) long sought a solution based on observations of the sun, moon, stars, and planets. Warring governments made common cause to find a solution that would benefit all mankind. The English Parliament passed the Longitude Act of 1714, offering a prize of 20,000 pounds for a solution.
Since the earth rotates 360 degrees in 24 hours, a very accurate and stable timepiece would also suffice. The difference in longitude between two points is precisely equivalent to the difference in time, say, between the observed sunrises at the two points. John Harrison, an English carpenter, devoted his life to building a perfect clock. He was ultimately awarded the prize money in 1773.
Harrison created a mechanical marvel that survived the rolling shipboard environment and temperature extremes without loosing or gaining more than 1 second per day. Imagine the engineering involved! His “H3” is pictured above.
James Cook and Robert Fitzroy are credited with mapping the coasts of Australia, New Zealand, and South America with unparalleled accuracy. Cook lauded Harrison’s timekeeper for its performance on his second voyage. Fitzroy took 22 Chronometers with him on board the Beagle,
“Longitude”, by Dava Sobel, describes the efforts to find a solution. It is a fascinating tale of science, politics, and human intrigue.
