What's On: Ships, Clocks & Stars: The Quest For Longitude at National Maritime Museum
In many ways, a major new exploration of the quest for longitude at the National Maritime Museum is the story of Greenwich itself.
The Royal Observatory was founded in 1675 to help mariners "find out the so much desired longitude of places for perfecting the art of navigation".
The combination of time, space and meridian that gives Greenwich its heritage is also the blend of sciences that provided the answer to a problem that cost so many lives.
Ships, Clocks & Stars: The Quest For Longitude takes as its cue the passing of the Longitude Act, 300 years ago. (The scroll of the Act itself is on public display for the first time.)
This Act constituted the Board of Longitude - a mix of scientists, Admiralty top brass and politicians - which gave grants and rewards for ideas that could help ships fix their East-West position.
The Act triggered an tumult of thought from some of the greatest names in the land - Isaac Newton, John Flamsteed, Edmond Halley, Charles Babbage - while the Georgian coffee houses were homes of fertile discussion - and derision.
Five major areas emerged as viable - signalling, magnetic field variation, clocks, lunar distances, and the rotation of Jupiter's moons. Of those, two showed promise and ran in tandem - improving the accuracy of clocks and tabulating the moon's movement. The former helped keep accurate record of longitude while the latter was the best way to find it, if lost.
One name is synonymous with the quest. John Harrison, the clockmaker whose breathtaking chronometers H1 to H5 are on display in an exhibition packed with thrilling artefacts. (The paradigm-shifting H4 is pictured.)
Co-curator Rebekah Higgitt said: "The well-known story is John Harrison, the lone genius, solving the world's most greatest scientific problem.
"I can see why people want the John Harrison story to be true. In fact Harrison gets a huge amount of support; and it is much more about the government investing, about collective endeavour.
"The discovery or an invention is not the end of the story, it takes a lot of time and a lot of people."
The impressively-mounted exhibition follows the two leading and complementary contenders through their evolution and mass production. They turn up as footnotes in some of the finest tales of our maritime heritage.
Larcum Kendall reproduced Harrison's clocks and his K1 went with James Cook on his voyages to the South Seas while K2 stayed with mutinous crew of the Bounty while exiled William Bligh used traditional tools of navigation to the ship's boat for a 47-day odyssey.
Rebekah said: "The Board of Longitude continued to exist to 1828 and it continued to support the process."
Its demise was political at a time of great upheaval and reform although the work never stopped and was initially taken over by the Admiralty with the Royal Observatory an important resource.
The story, in a sense, continues to this day. No great revolution over took the stars and clocks as a reliable method until satellite-based GPS.
Rebekah said: "The [celestial] nautical almanac is still your back-up if GPS is blocked or fiddled with - its a military technology owned by America so it is vulnerable.
"They stopped teaching astronomical methods in the Navy some time ago but they are re-introducing it to a degree just so some people know the techniques because it remains the only way you can find your longitude if you've lost it.
"Timekeepers are still effective but are not issued. Once you can get a time signal by wireless this takes over. But it is not until the late 20th century that these systems finish."
Until Jan 4, National Maritime Museum, £8.50, rmg.co.uk
© Images: National Maritime Museum