In two parallel stories, the clockmaker John Harrison builds the marine chronometer for safe navigation at sea in the 18th Century and the horologist Rupert Gould becomes obsessed with restoring it in the 20th Century.

In the eighteenth century, the only way to navigate accurately at sea was to follow a coastline all the way, which would not get you from Europe to the West Indies or the Americas. Observing the sun or stars would give you the latitude, but not the longitude unless done in conjunction with a clock that would keep time accurately at sea, and no such clock existed. After one too many maritime disasters due to navigational errors, the British Parliament set up a substantial prize for a way to find the longitude at sea. This movie's main story is that of craftsman John Harrison (Sir Michael Gambon). He built a clock that would do the job, what we would now call a marine chronometer. But the Board of Longitude was biased against this approach and claiming the prize was no simple matter. Told in parallel is the twentieth century story of Rupert Gould (Jeremy Irons), for whom the restoration of Harrison's clocks to working order became first a hobby, then an obsession that threatened to wreck his life.

In the early years of the eighteenth century, a British fleet foundered on the rocks off of the Scilly Isles due to a navigational error. The problem was an incorrect estimation of longitude, something that had yet to be perfected. As a result, Parliament announced they would award a sum of twenty thousand pounds sterling to anyone who could develop an accurate method of determining longitude. John Harrison (Sir Michael Gambon), a carpenter by trade and amateur clockmaker, decides to try and solve the issue by building an accurate maritime clock. Over many years, Harrison perfected timepieces that would accurately give time at a known location, such as Greenwich, which could then be compared against local time (by measuring the position of the sun in the sky). The time difference could then be converted to degrees of longitude which, combined with the already existing method of calculating latitude, would give the ship's exact location. Harrison's timepieces were a marvel of the age, but it took several experiments and a great many years before his accomplishment was recognized and the cash prize awarded. Interspersed with Harrison's story is that of Rupert Gould (Jeremy Irons), who, just after World War I, located some of Harrison's original timepieces and tried to restore them to working order.—garykmcd

This movie follows John Harrison's (Sir Michael Gambon's) quest to find the key to determining longitude. In the eighteenth century, the problem of measuring longitude confounded scientists, sailors and politicians. In 1707, unable to determine their exact location through a thick fog, two thousand men of the British fleet perished by accidentally running into the rocks off of the Scilly Islands. As a result of this tragedy, in 1714, British Parliament passed the Act of Longitude to offer an enormous cash prize to the person who could solve the problem of longitude. A carpenter by trade, Harrison believed that the solution lied in finding a way to measure time accurately, going against many of the scientists of the day, who felt that the mystery would be solved through celestial navigation. Harrison designs and creates four increasingly refined timekeepers. This work takes him through thirty years of struggle and determination (not only his, but his family's, friends', and allies' as well) to solve what was referred to as the "greatest scientific problem of the time." Along the way, he faces the animosity and interference of many of the celestial navigation proponents.—PetrinaC <[email protected]>

When British Parliament creates an award of twenty thousand pounds sterling to whomever can come up with a solution for determining longitude at sea, a carpenter-turned-clockmaker, John Harrison (Sir Michael Gambon), begins his experiments to build an accurate timepiece unaffected by sea travel. His main obstacles are lack of money, a judgment Board convinced that the answer lies in astronomy and not clocks, and the mechanics of the clock. Rupert Gould (Jeremy Irons), a retired Naval officer who suffered a nervous breakdown in World War I, has been researching Harrison's history and makes efforts to locate and restore Harrison's clocks. Harrison's and Gould's struggles are linked by the clocks which the two men will, across two hundred years, make tick accurately enough to measure longitude.—Kathy Li