The mechanical clock was certainly not the first means of measuring time, but it is definitely the most remarkable. As the historian Lewis Mumford wrote in Technics and Civilization "The clock has been the foremost machine in modern technics. And at each period it has remained in the lead; it marks a perfection toward which other machines aspire."
Although nobody knows for sure who invented the first mechanical clock, it most likely had its roots in Europe toward the end of the 13th century. Early clocks used gravity to their advantage by utilizing weights falling to the ground to turn the various gear wheels; later clocks would have to overcome this force. The invention of the pendulum by Galileo in approximately 1583 advanced clock-making considerably. This invention reduced the inaccuracy from fifteen minutes a day to ten to fifteen seconds a day. Although this was a considerable improvement, even small inaccuracies posed a problem for navigation.
The accurate measure of time was the only way to calculate a ship's longitude (the position of the ship measured to the east or west of the meridian). An error in the measurement of time could point the ship in the wrong direction. Voyages lasted for many months and even a few degrees off could result in a ship landing hundreds or thousands of miles off the destination port. The pendulum clock was sufficiently accurate, but it had one major drawback for navigation. The pendulum could not maintain a regular swing when subjected to the movements of the ship.
It was imperative that someone develop a method for measuring accurate time while at sea. First Spain, and then France, Italy and England devised competitions to solve this problem. The competitions brought together the greatest minds throughout the 17th and 18th centuries. The result, in 1759 a self-taught carpenter named John Harrison created a masterpiece. The clock was tested at sea on an eleven and a half week long voyage-it only lost five seconds. Another test was performed and it was confirmed, the most famous chronometer ever produced had been created. Harrison's invention advanced the science of measuring time considerably and we still benefit from his work.