Time = Longitude - Longitude = Time

When I was in London last year - I had the chance to visit the Royal Observatory where this drama played out nearly three centuries ago....

John Harrison - Longitude....

Although John Harrison had advanced a practical method of finding longitude (60 minutes equal 15 degrees of longitude equals 900 nautical miles at the equator - so time equals distance and distance equals time) with his prizewinning chronometer, H-4, in 1759, his successors still faced the formidable challenge of making his complex and delicate design readily reproducible and affordable.

Benefiting from technical improvements like the detent escapement and the temperature-compensated balance wheel, a simplified version of H-4 would remain the basis of chronometer design. However, significant advances would be made in chronometer production.

The demand for chronometers fell off as the age of exploration drew to a close, but was temporarily revived by the need for navigational instruments during both World Wars. However, this period also saw the rise of alternative methods of navigation based on radio and radar which, before long, would eclipse the chronometer. It must be noted that although considered a secondary means of navigation today, the chronometer is the only navigational method that is completely self-reliant. in the event of downed power sources, loss of radio communications, or satellite malfunction, the chronometer remains a reliable means of navigating the seas.