Coming your way, 19 June… Finding Longitude

Yes, this is one big advert – but hey, this is my blog and you all know that I’ve been going on about longitude for long enough…

19 June 2014 sees the publication of Finding Longitude: How Clocks and Stars Helped Solve the Longitude Problem, written by me and my former National Maritime Museum colleague, Richard Dunn. It accompanies the exhibition Ships, Clocks & Stars: The Quest for Longitude, on at the NMM from 11 July 2014 – 4 January 2015.


Finding Longitude

I will admit that the front cover’s stormy seas, echoed in the exhibition publicity, is a little off the mark for longitude (stormy seas will get you whether or not you know where you are), but evidently drama and peril sell. We authors did, however, have (mostly) full control over the contents and many images that are inside. You can get a flavour of this from the “See Inside” feature on a well-known book-selling website that you will otherwise undoubtedly eschew.

Finding Longitude 2

The book largely follows the flow of the exhibition, but gives us a chance to go into more depth, provide additional stories and name more names : longitude was a very collective endeavour. It’s a story that starts well before the Longitude Act of 1714 and goes on until the middle of the 19th century: the voyages of HMS Beagle, which girded the Earth with a series of accurately determined locations, are our symbolic stopping point. We have space to be a little more international, although this is still certainly the story from the British perspective, and we have the luxury of being able to illustrate objects that could not fit in the exhibition or travel overseas.
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It’s available as a hardback (RRP £25), as a paperback special edition available at the Museum for the exhibition (titled Ships, Clocks & Stars: The Quest for Longitude) and as an eBook (RRP £9.99).
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The Longitude Prize Committee: a new Board of Longitude?

Cross-posted from The H Word blog.

The Board of Longitude brought to life at Greenwich Theatre in 2005.
The Board of Longitude brought to life at Greenwich Theatre in 2005. Photograph: Tristram Kenton

The new Longitude Prize has nothing to do with longitude: that particular problem is long since solved. Yet it has a Longitude Committee that, like the original Board of Longitude, includes the Astronomer Royal. Lord Rees has borrowed the tercentenary of the first Longitude Act and the idea of an incentive prize in the hope of turning money and talent toward a new challenge.

But, apart from the Astronomer Royal, what are the connections between the new committee and the old? And what do the differences tell us about the two schemes?

The Commissioners

The 1714 Act appointed a number of Commissioners of Longitude, either by name or by position, from political, maritime and scientific worlds. By making several positions ex officio, the authors of the Act ensured – by accident or design – that the Commission could continue in perpetuity. It also marked a first by bringing key scientific positions directly into government decision-making.

The political positions were: the Speaker of the House of Commons, the First Commissioner of Trade and, in 1714, ten named Members of Parliament. The maritime and Admiralty representation was: the First Lord of the Admiralty; the First Commissioner of the Navy; the Admirals of the Red, White and Blue Squadrons; and the Master of Trinity House.

The scientific men were: the President of the Royal Society; the Astronomer Royal; and the SavilianLucasian and Plumian Professors at Oxford and Cambridge Universities. Later the Lowndean Professorship, founded in 1749, was also added.

The Commissioners do not seem to have met before 1737, when they deliberated John Harrison’s first reward, by which time many of the named MPs had died. The left the ex officios, the best-known of which attending in 1737 were Edmond Halley and James Bradley. Halley was Astronomer Royal, although he had previously been a Commissioner as Savilian Professor. Bradley was there as Savilian Professor, but was to remain a Commissioner when he succeeded Halley as Astronomer Royal. It was a small world.

The Board

The Commissioners of Longitude were not known as the Board of Longitude until around the 1760s. By then business was considerably more bureaucratic and regular and the core team had settled down as the Astronomer Royal, President of the Royal Society, the professors, the first Lord of the Admiralty and the secretaries to the Board and the Admiralty.

Things changed again when, under the influence of Joseph Banks, the Board was reorganized. It had already become concerned with all navigational issues, not just longitude, and now the ambition was to become a scientific advisory board to the Admiralty. The 1818 Longitude Act appointed three Fellows of the Royal Society and three salaried Resident Commissioners on top of the professors. This was, apart from packing the Board with Banksian sympathisers, a way to include other scientific fields.

The Committee

I can’t comment on the internal politics but, despite obvious differences, there are some interesting similarities between the Board and the Longitude Committee. Firstly, of course, there is Lord Rees, who as Astronomer Royal links the two groups. (A few years ago, Rees had positions that would have earned him a seat on the Board of Longitude three times over: Astronomer Royal, President of the Royal Society and Plumian Professor).

Oxbridgian scientific gravitas remains, with Athene Donald, Professor of Experimental Physics at Cambridge, and Kay Davies, Dr Lee’s Professor of Anatomy at Oxford. Also present is is Wendy Hall, Professor of Computer Science at Southampton. The range of disciplines shows that, while longitude was seen as a mathematical and astronomical matter, the breadth of potential challenges this time around requires a broader mix. The presence of women also reveals social change, although at 4/18 of the Committee, perhaps less than we’d like.

Engineering had no academic or institutional presence in the early 18th century, but in the 21st it is clearly a field relevant to solving technical problems. Thus, rather than the President of the Royal Society, we haveMartyn Thomas, Vice-President of the Royal Academy of Engineering.

A novelty of the last century is the appointment of scientists directly to government. On the Committee are Chief Scientific Advisor Mark Walport, Chief Medical Officer Sally Davies and David Mackay, Regius Professor in Engineering at Cambridge and Chief Scientific Advisor to the DECC. Otherwise, the connection to government is down to John O’Reilly, Director General of Knowledge and Innovation (there’s a title!) at BIS.

From here the differences are significant, starting with those linking business, charity and government. In 1714, men who made their living through trade would not, unlike the propertied gentlemen MPs, have been seen as disinterested enough to guarantee their trustworthiness. In 2014, however, we have David Gibson, Head of Innovation at GlaxoSmithKline; Andrew Dunnett, Director of the Vodafone Foundation;Iain Gray of the Technology Strategy Board; and Geoff Mulgan, Chief Executive of the prize organisers Nesta.

Also included are individuals known for championing and communicating science. There is Imran Khan, Chief Executive of the British Science Association; Roger Highfield, journalist and Director of External Affairs at the Science Museum; and Andrew Cohen, Head of the BBC Science Unit. Spanning different ends of science and technology publishing arePhil Campbell, Editor in Chief of Nature, and David Rowan, editor of Wired Magazine.

The public

While 18th-century Britain had many significant popularisers of science, they would not have been Board members. Plenty was said about providing something of public utility, not to mention saving lives at sea, but there was no interest in consulting more widely. Indeed, it seems that the call for longitude rewards came from the scientific community – potential winners of money – rather than from mariners.

The role of the public has, therefore, changed. While in 1714 an interested public was the source of potential solutions, with the large reward of £20,000 designed to spread the word and catch the eye, in 2014 there is little sense that answers will come from outside a trained and professional group of scientists or engineers. Thus the public is brought on board to help (a little) with a choice from the six potential challenges.

What the result of the public choice is, and the response to the challenge, time will tell. Given that, unlike the original Commissioners of Longitude, the Longitude Committee has not been appointed ex officio, we might assume they hope it will all take less than half a century.

 

There was no such thing as the Longitude Prize #2

I am reposting part of this post from the Longitude Project blog, as a timely reminder, because there *is* now such a thing as the Longitude Prize. It is also on Twitter and much in the media as it heads toward official launch next week. The six potential challenges for the new £10 million prize will be explored on Horizon on 22 May, in a programme that will also look back at the original longitude story. I will appear briefly as a talking head in a film on challenge prizes on The One Show tonight, failing to make the points outlined below. [Update: just heard that my contribution has been cut from the brief film – boo!]

Despite having, back stage, had some impact on how Nesta have been thinking about their prize, the media focus remains on the story of a “prize” that was won by John Harrison. Having just done a talk last night pointing out that Newton was right to say longitude was “not to be found by Clock-work alone” – and that, in fact, the timekeeping method could never have taken off without the complementary lunar-distance method working in tandem with it – I turn back to this post. There was no prize. Harrison did not win it. He did not solve the longitude problem single handed. It made sense for the Board of Longitude to back both methods.

….

There was no such thing as the Longitude Prize. From the beginning, as well as using the term “reward” not “prize”, the Longitude Act offered a range of sums depending on the accuracy achieved. Later on, with subsequent acts, the possible rewards proliferated, initially with the realisation that Harrison needed to be supported with ‘grants’ of money while developing his clocks and, by the 1770s, with knowledge that a handful of sea watches was not a complete solution and that benefit would be gained by offering further rewards for improvements to techniques and hardware.

Derek Howse’s article on the Finances of the Board of Longitude reveals what was spent by the Commissioners. Between 1714 and 1828, rewards accounted for only 33% of spending, while overheads (23%), expeditions (15%) and publications (29%) made up the rest. The total spent on rewards was £52,534, of which £22,000 went to Harrison. This sum was made up of a number of payments between 1737 and 1764 to improve and test his timekeepers, £7500 paid in 1765 (a further sum being on offer to take this up to a £20,000 reward if two more sea watches could be made, one by Harrison and one by another maker) and £8750 was awarded by an act of parliament in 1773.

It’s a matter of interpretation as to whether this process constitutes receiving the maximum reward. A number of the payments to Harrison had required additional acts (in 1762, 1754 and 1765) and, ultimately, all the money came from government as a result of the original Act of Parliament. However, the final payment did not appear in the Board’s accounts, which confirms the fact that this final move took place outside the Commissioners’ decision-making process.

More interesting to me is who received the other £30,534. Happily, Howse’s article lists all the reward recipients in an appendix. The bulk of the rewards post-date 1765, when the Board played its hand and divided out rewards between the two successful methods, timekeeping and lunar distances. While Harrison received his £7500 in October 1765, in May:

  • Leonhard Euler was paid £300 “for Theorums furnished by him to assist Professor Mayer in the Construction of Lunar tables”
  • Maria Mayer was paid £3000 as a posthumous reward to her husband Tobias “for his having constructed a Set of Lunar Tables” and to her for making them property of the Commissioners
  • Catherine Price, Edmond Halley‘s daughter, was paid £100 for handing over several of Halley’s manuscripts, which the Commissioners believed “may lead to discoveries useful to navigation”.

While Harrison’s work was the cause of the Commissioners beginning to meet, keep minutes and spend money, there were other pre-1765 pay-outs. Christopher Irwin received £600 in 1762-3 for his marine chair (designed to allow observations of Jupiter’s satellites on board ship) and way back in 1741, William Whiston was paid £500 “For procuring a new Sett of Astronomical Instruments for finding out the Longitude on the Coasts of this Kingdom with the Variations of the Needle and for enabling him to make Observations with them”.

Harrison was certainly the biggest single beneficiary of the Longitude Acts, but balanced against that are the many involved in lunar distances. There are the rewards to Euler and Mayer, but 1765 also saw the beginning of investment in the computing work (£35,559 to 1828) and publication of the Nautical Almanac. There had already been expenditure on lunar-distance-related hardware, salaries for trials and expeditions and later sums were paid out for work on astronomical tables, for example £1537 between 1770-93 for Charles Mason‘s efforts and £1,200 to Josef de Mendoza y Rios for his longitude tables in 1814.

Post-1765 there were numerous rewards, mostly of tens or hundreds of pounds. The largest, after Harrison’s, was divvied up among the officers and crew of HMS Hecla and Griper in 1820, who received £5000 for reaching 110°W within the Article Circle, after discovery of the North West Passage became one of the Board’s interests in the 1818 Act. The Arctic voyages also led to Edward Sabine being given £1000 in 1826 for his pendulum experiments. Those who helped develop the chronometer as a commercial product, John ArnoldThomas Earnshaw and Thomas Mudge, were each rewarded with £3000.

Although there was in the 18th-century a sense of competitiveness and occasional reference to a longitude prize (of which more in a later post [since published here]), suggesting that there was a single pay-out that Harrison did or did not win misses both the richness of the history of the Board of Longitude and obscures the way that longitude solutions were developed and used.

 

Happy birthday Robinson Crusoe: the fictional author of a “History of Fact”

Cross-posted from The H Word blog.

Daniel Defoe’s book was published 295 years ago today [25 April], marking the birth of the author Robinson Crusoe and a seriously playful entanglement of fact and fiction.

Daniel Defoe's Robinson Crusoe (1719)
Frontispiece and title page from original 1719 edition

I hope plans are afoot to celebrate the tercentenary of the publication of Daniel Defoe’s Robinson Crusoe in 2019. With five years to go, however, 2014 also seems an apt time to take a look at this famous book, not least because this year is a celebration of all things Georgian: marking the accession of George I, we have the BBC’s Georgian Season, and exhibitions at the British Library and Queen’s Gallery. Signed just before George’s arrival, was the 1714 Longitude Act, the tercentenary of which is being marked with a Longitude Season at Royal Museums Greenwich.

Robinson Crusoe sits perfectly in the midst of this, highlighting new literary forms available to a growing reading public, and the interest in travel and the exotic at a time of expansion of maritime trade and empire.

While the book is seen today as an important precursor to the novel, as part of a new genre of realistic fiction, it was designed, at least in part, to confuse and to question. Robinson Crusoe was its purported author, not its title. The actual title of the first edition placed the book squarely in the realm of genuine (if sometimes embellished) travel narratives:

The Life and Strange Surprizing Adventures of Robinson Crusoe, Of York, Mariner: Who lived Eight and Twenty Years, all alone in an un-inhabited Island on the Coast of America, near the Mouth of the Great River of Oroonoque; Having been cast on Shore by Shipwreck, wherein all the Men perished but himself. With An Account how he was at last as strangely deliver’d by Pyrates. Written by Himself.

Full of geographical detail, with the “author” clearly identified, there was nothing to distinguish this as fiction. The picturesque image on the frontispiece pointed to the remarkable experiences to be related, but would have reminded readers of images of peoples from other parts of the world, shown as “other” but rendered strangely familiar by European artists, used to depicting European faces, landscapes and dress.

Defoe’s title is worth comparing to those of other travel and adventure narratives. For example, that published in 1681, by a real sea captain: Robert Knox of the East India Company. Alongside the experiences ofAlexander Selkirk, who spent four years on an uninhabited island until being rescued in 1709, Knox’s adventures and narrative have been seen as one of Defoe’s inspirations:

An Historical Relation Of the Island Ceylon, in the East-Indies: Together, With an Account of the Detaining in Captivity the Author and divers other Englishmen now Living there, and of the Author’s Miraculous Escape. Illustrated with Figures, and a Map of the Island. By Robert Knox, Captive there near Twenty Years.

Knox’s book had been published by Richard Chiswell, identified on the title page as “Printer to the Royal Society”. As was typical of that Society’s tactics for underscoring the trustworthiness of new knowledge, emphasis was placed on the status of the author, the importance of eye-witness accounts and personal observation, told in plain writing and, as a bonus, supported by a map and illustrations.

Knox’s “Truth”, “Integrity” and “Credit” were attested to in statements from the very credit-worthy Christopher Wren and the Governor, Deputy-Governor and 24 named members of the Court of Committees of theEast India Company, who included a fair sprinkling of baronets and knights. A preface by Robert Hooke lauded Knox’s efforts, not least for doing what the Royal Society repeatedly asked of travellers by sharing potentially useful observations and experience of foreign lands with the public.

Defoe naturally also made use of such devices, playing with his readers’ understanding of truth and credibility in a way that alarmed some but was so popular with the public that the book went through several editions in its first year. In a preface the book’s “editor” commended it to the public as “a just History of Fact”, noting that “The Story is told with Modesty, with Seriousness, and with a religious Application of Events to which Wise Men always apply them”.

Rather than as simply a novel, then, Robinson Crusoe should also be read as a hoax or, perhaps more accurately, as a satire on travel narratives and other texts attempting to present reliable knowledge. Whether readers took his fiction as truth, or they doubted it effects, it raised questions about the acceptance of the words put down, however plain the language, by other travellers, experimenters and observers. This uncertainty was, as much as the adventure and exoticism, part of the book’s appeal.

Crusoe is our perfect guide to this year of Georgian exploration.

Science fictions and the history of science

Cross-posted from Science Comma blog.

For those who are fans of sci-fi, or interested in how sci-fi plays into the history of science, there are some things you might want to take a look at.

Firstly, this Friday there is a free lunchtime lecture at the Royal Society on “The Royal Society and science fiction”, being given by Professor Farah Mendlesohn, who is head of department for English, Communication, Film and Media at Anglia Ruskin University. The blurb reads:

The lone (mad) scientist is a common trope in science fiction, but hidden away is a fascination with secret and semi-secret societies who work for the future of all mankind. This talk will look at the representation of the Royal Society in science fiction and fantasy as fact, fantasy and metaphor.

For those who can’t make it to London, the talk should be available, like the Society’s other events, as a video afterwards.

Secondly, yesterday saw the republication of the 1870-71 short story, The Brick Moon, by Edward Everett Hale. It is being published by Jurassic London, along with a new story, Another Brick in the Moon, by Adam Roberts. Details of the publication are available here, and also from this post by Richard Dunn, Senior Curator at Royal Museums Greenwich, who co-wrote the introduction with Marek Kukula, Public Astronomer at the Royal Observatory Greenwich.

Cover of the newly published edition of The Brick Moon
Cover of the newly published edition of The Brick Moon

The original story is about an artificial satellite, the Royal Observatory, the Greenwich Meridian and possible solutions to the problem of finding longitude at sea. It is a perfect accompaniment to the Longitude Season, just getting underway in Greenwich.Secondly, yesterday saw the republication of the 1870-71 short story, The Brick Moon, by Edward Everett Hale. It is being published by Jurassic London, along with a new story, Another Brick in the Moon, by Adam Roberts. Details of the publication are available here, and also from this post by Richard Dunn, Senior Curator at Royal Museums Greenwich, who co-wrote the introduction with Marek Kukula, Public Astronomer at the Royal Observatory Greenwich.

Finally, as well as a major exhibition on the longitude story (opening in July), this season also includes an art and fiction response. Already open at the Royal Observatory is Longitude Punk’d, an intervention in, or takeover of, the pre-existing longitude galleries. Author Robert Rankin and other artists and makers have come up with a whole range of more or less ludicrous or plausible ideas about solving longitude or alternative realities in which clock maker John Arnold made himself clockwork legs and Astronomer Royal Nevil Maskelyne built an airship and hoped to contact parallel universes – just in case they knew his longitude. Read more from the curator here.

Longitude Season has started…

There has already been plenty of longitude on this blog, The H Word and the Longitude Project blog, so apologies that there is more to come. This has all been leading up to 2014, the tercentenary of the first Longitude Act, and the start of Longitude Season at Royal Museums Greenwich. It seems like a good idea to put in one place where we’ve been and some of what’s happening this year.

The Board of Longitude Project logo.
The Board of Longitude Project logo.

First came the Board of Longitude Project. A five year, AHRC-funded research collaboration between the National Maritime Museum and the Department of History and Philosophy of Science at the University of Cambridge. The team is/was: Principal Investigator Simon Schaffer, Co-Investigators Richard Dunn (Senior Curator and Head of Science and Technology at NMM) and me; two postdocs (Alexi Baker and Nicky Reeves) and three PhD students (Katy Barrett, Eoin Phillps and Sophie Waring). Very shortly joining us as engagement officer is Katherine McAlpine.

Then came the brilliant digitisation project, a JISC-funded digitisation of the Board of Longitude archive, together with related papers from Cambridge University Library and the NMM. Because of its association with the research project and the Museum, this came with lots of add-ons beyond the scanning and listing, and you can read more on the site and at my Guardian post here.

This year is about delivery and public engagement: four exhibitions, two books and a conference (although there’ll be more scholarly books, collections and articles to come out of the project in following years).

Exhibitions

Already open at the Royal Observatory is Longitude Punk’d, which is a steampunk intervention (invasion?) into the courtyard and Flamsteed House that plays with existing spaces and displays, the themes of travel and longitude and with art/science, fact/fiction, real/fabricated. You can read more about it in this post by curator Heloise Finch-Boyer. It is inventive, playful and very funny, but can also confuse and is not necessarily to everyone’s taste. As a response to the problem of denuding the existing galleries in order to put on the main longitude exhibition (see below), it is really brilliant. Once the two exhibitions exist together I hope everyone will be happy! Hashtag is #LongitudePunk’d

Also at the Observatory is a small image and text display, Start to Satellites, about the development of satellite navigation, which takes the story of navigation well beyond the 18th and 19th one about longitude.

Next up will be the main event: Ships, Clocks & Stars: the Quest for Longitude, opening to the public on 11 July. It is an object-rich, historical telling of the story, supported by AV and interactives, with Richard Dunn as the lead curator, me (though my involvement has somewhat diminished since I left the museum) and an NMM team involving Kris Martin, Claire Warrior and Matt Lawrence. I hope it will be fab, and you will hear more anon! Hashtag is #ShipsClocksStars

Last to open will be Art and Science of Exploration, a rehang in The Queen’s House that focuses on the art surrounding the voyages of James Cook. It will be the first opportunity to have Stubbs’s kangaroo and dingo properly on show, alongside paintings by Hodges and Webber. In many ways it will be a natural extension of the main exhibition, which features a section on Cook’s voyages, a key testing ground for new longitude techniques. Hashtag is #ArtSciEx

There will be lots of events on during the run of the exhibitions, so keen an eye on the website. The hashtag for the season as a whole is #WhereOnEarth.

Books

The official book accompanying the exhibition has been written by Richard Dunn and me, and is published by Collins. Called Finding Longitude, it is already available on Amazon for pre-order. It’s available on Kindle and a paperback edition will be sold in the exhibition shop (with luck the hardback trade edition will also make it to paperback?). This follows the same narrative as the exhibition, taking the story well beyond Sobel’s John Harrison focus, and is beautifully illustrated with historical painting and objects. It is out on 19 June.

Out in the autumn is a collection of essays on Nevil Maskelyne, published by Hale Books, called Maskelyne: Astronomer Royal. I have edited it and there are chapters and sections by me, plus chapters by Jim Bennett, Mary Croarken, Nicky Reeves, Rory McEvoy, Alexi Baker, Caitlin Homes and Amy Miller, largely coming out of the symposium we held back in 2011. This should also be well-illustrated with images from the NMM’s collections and, although not in any way replacing Derek’s Howse’s biography of Maskelyne, adds some interesting different angles.

Conference 

The big conference for the project, and the exhibition, is Longitudes Examined: Tercentenary Conference on the History of the Board of Longitude and the Determination of Longitude at Sea. The programme is now available online and looks brilliant (I’m not speaking, although will be part of the final discussion panel, so I’m allowed to say that)! 

Farewell Greenwich Mean Time (see you in October)

Cross-posted from The H Word blog, where this was first published on 30 March 2014.

The 24-hour Shepherd Gate Clock outside the Royal Observatory, Greenwich, displaying Greenwich Mean Time to the public.
The 24-hour Shepherd Gate Clock outside the Royal Observatory, Greenwich, displaying Greenwich Mean Time to the public.

It has become something of a tradition on this blog to mark the biannual change of the clocks and, although I no longer work at the Royal Observatory Greenwich, it’s a habit that sticks. This time, as we say farewell to it until the autumn, it seems a good opportunity to reminisce about Greenwich Mean Time.*

Why Greenwich time? And what’s mean about it?

Mean time is clock time. It is a regularised, idealised version of solar time that is tracked not by the apparent motions of the Sun, observed by shadows on sundials, but by a mechanical device that splits the solar day into equal parts. Mean time ticks away at the same pace no matter the season. The difference between the two is described by the equation of time.

Establishing the relationship between mean solar time and apparent solar time only really became possible, or useful, with the arrival of the pendulum clock in the 1650s. This made the mechanical clock, for the first time, a scientific instrument. Christiaan Huygens, who developed the first prototype pendulum clock in 1656, was able to produce reasonably accurate tables of the equation of time in 1665.

However, it fell to John Flamsteed to publish tables in 1672-3 that tackled the problem in what became the standard way. He provided the formula by which apparent solar time could be converted into Mean Time.

Just a couple of years later, Flamsteed was appointed the first Astronomer Royal and moved into the newly built observatory in Greenwich. There, he and his patrons had installed state-of-the-art pendulum clocks by the best clockmaker available, Thomas Tompion. With observations of the Sun and the help of his tables, Flamsteed set these clocks to the local time: Greenwich Mean Time.

Greenwich time became important because there were people measuring it and because other people made use of astronomical observations based on it. Flamsteed’s catalogue of stars, which was to become a standard reference work for the following decades, listed their positions based on Greenwich time.

It was one of Flamsteed’s successors, Nevil Maskelyne, Astronomer Royal from 1765 to 1811, who did most to ensure that GMT mattered to more than just astronomers. Under his initiative, observations made at Greenwich were processed into tables that could be used by navigators and cartographers to establish positions at sea or on land. This was the Nautical Almanac, first published for the year 1767.

Surveyors of the Royal Navy and the Ordnance Survey relied on data that was based on observations made at Greenwich, meaning that their charts and maps used Greenwich as a reference point. More precisely, this was the meridian (north-south line) on which the chief telescope at Greenwich was mounted. The Greenwich meridian thus became a prime meridian for British mapping, and east-west position was measured from there. To establish longitudes it was necessary to know the difference between local time and GMT. This could be worked out with astronomical observations and the tables of the Nautical Almanac and, increasingly, with chronometers set to GMT.

The move of GMT from the specialist worlds of astronomy, navigation and surveying into civilian life was down to the increasing role of technologies and cultures that demanded standardization. The arrival of railways made timetabling a necessity. Telegraph systems made it both desirable and possible to know what time it was elsewhere. Factory work made production and payment dependent on timekeeping.

GMT became “Railway Time” in the 1840s, and Britain’s legal standard time in 1880. Despite what you’ll often read, it did not become an international standard in 1884. In that year an international conferencedid recommend the adoption of the Greenwich meridian as the world’s reference point for time and longitude, but it was just a recommendation.

What actually happened as a result of the International Meridian Conference, and what did not, is a story for another post. See you back here on 26 October.

* Our standard time is now in fact Coordinated Universal Time (UTC), derived from International Atomic Time but as close as darn it to GMT.