Longitude

It was once one of the great unsolved problems of the early modern world: the calculation of exactly how far east or west a given point was on the surface of the Earth. Longitude was a challenge that sat at the intersection of science, navigation, empire and time itself. For centuries, sailors had been able to determine latitude, or their position north or south, with reasonable confidence. But its counterpart remained dangerously elusive, leaving those traversing the oceans vulnerable to error, shipwreck and disaster. In the search for a solution, astronomers, inventors, statesmen, and seafarers all played their part. But why was Longitude so hard to figure out reliably? Who really solved the problem? And what changed when sailors could finally measure their position at sea with precision? This is a Short History Of Longitude. A Noiser podcast production. Hosted by John Hopkins. With thanks to Dr Emily Akkermans, Curator of Time at Royal Museums Greenwich. Written by Sean Coleman | Produced by Kate Simants | Production Assistant: Chris McDonald | Exec produced by Katrina Hughes | Sound supervisor: Tom Pink | Sound design by George Colwey | Assembly edit by Dorry Macaulay | Compositions by Oliver Baines, Dorry Macaulay, Tom Pink | Mix & mastering: Cody Reynolds-Shaw Unlock the next two episodes of Short History Of… right now by subscribing to Noiser+. You’ll also get ad-free listening and early access to shows across the Noiser podcast network, including Real Survival Stories and Sherlock Holmes Short Stories. Just click the subscription banner at the top of the feed, or head to www.noiser.com/subscriptions to get started. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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• 0:59Speaker 02

  It's October 22, 1707, near the Isles of Scilly.

• 1:06Speaker 02

  A heavy storm is pressing down over the Atlantic, wind stirring the sea into an angry frenzy under a seamless black sky.

• 1:16Speaker 02

  HMS Association, a 90-gun warship, is guiding a fleet of over 20 English ships towards the western end of the English Channel.

• 1:27Speaker 02

  By now scattered and spread out, thanks to bad weather, the fleet is under the command of Sir Admiral Cloudsley Shovel, one of England's most experienced naval commanders. They're returning from the War of the Spanish Succession, homeward bound after months in the Mediterranean.

• 1:45Speaker 02

  At least, they are meant to be.

• 1:50Speaker 02

  England lies somewhere ahead. But for days, the sky hasn't cleared once to give them a view of either sun or stars, so they've had nothing to take a bearing from, no way to fix their position upon the sea.

• 2:05Speaker 02

  The ship rises, pauses, and drops again, hard enough to jar the teeth.

• 2:14Speaker 02

  Below deck, a young sailor grips the edge of a gun carriage as the floor tilts beneath him. His hair is salt-stiff, his hands raw, and his body moves by instinct, bracing before each roll.

• 2:29Speaker 02

  Like the others on the gun deck, he has been weeks without a proper night's sleep. They are all exhausted, hungry, and desperate to be home.

• 2:39Speaker 02

  Though the sailor can't hear the words of the orders bellowed to the men above, he can hear the tone, and the tension it carries travels through the timbers. Every man aboard shares the same feeling of dread. The sea is always threatening and uncertain, but with no means of knowing where they are, right now, it's even more so. Though they've already avoided countless, untold, unseen dangers by little more than good fortune or divine intervention, what lies ahead is an unfathomable labyrinth of peril. And their luck surely can only hold out for so long.

• 3:16Speaker 02

  The sailor shifts his grip as the ship lurches again. Across the deck, a cannon slams against its restraints,

• 3:25Speaker 02

  and another man scrambles to secure it. They climb another swell, and for a moment, they hang, suspended in time and place.

• 3:36Speaker 02

  Then, an awful, grinding crunch tears through the ship, rumbling up through the hull like a kraken awoke.

• 3:46Speaker 02

  The deck heaves violently as the vessel comes to an immediate halt. The sailor is launched sideways, crashing into timber and iron. Around him, men are thrown against cannons, bulkheads, and each other.

• 4:02Speaker 02

  Though the fleet isn't yet supposed to be anywhere near land, the ship has run aground, stopped dead in her tracks.

• 4:10Speaker 02

  The freezing sea surges in below, and the sailor drags himself upright, hands slipping on wet wood.

• 4:18Speaker 02

  Scrabbling onto the sloping top deck, he narrowly avoids being crushed as the mast cracks and plummets.

• 4:27Speaker 02

  Blinking through the driving rain and spray, he sees others in the fleet meeting the same fate as, one after another, they are driven blindly onto the rocks. HMS Eagle, Romney, and Firebrand are all sinking.

• 4:49Speaker 02

  By morning, the sea will be strewn with wreckage and bodies, the greatest maritime disaster of the age, claiming nearly 2,000 lives.

• 5:02Speaker 02

  But they have been taken by a problem less tangible than war or even weather.

• 5:07Speaker 02

  Out here, in the dark, with no sun and no stars, the world has no fixed edges, no reliable measure of east or west. And without that, even the greatest fleet in the world is easily lost. Battles may have been won at sea,

• 5:28Speaker 02

  but longitude remains unconquered.

• 5:34Speaker 02

  It was once one of the great unsolved problems of the early modern world, the calculation of exactly how far east or west a given point was on the surface of the Earth. Longitude was a challenge that sat at the intersection of science, navigation, empire, and time itself.

• 5:56Speaker 02

  For centuries, sailors had been able to determine latitude or their position north or south with reasonable confidence. But its counterpart remained dangerously elusive, leaving those traversing the oceans vulnerable to error, shipwreck, and disaster.

• 6:13Speaker 02

  In the search for a solution, astronomers, inventors, statesmen, and seafarers all played their part. But why was longitude so hard to figure out reliably? Who really solved the problem? And what changed when sailors could finally measure their position at sea with precision?

• 6:33Speaker 02

  I'm John Hopkins. From the Noiser Podcast Network, this is A Short History of Longitude.

• 6:48Speaker 02

  For as long as sailors have ventured beyond sight of land, they have faced a simple but vital problem: How can you be sure where you are, out on the open ocean, where there are no landmarks or fixed points to guide you? The north-south question, or latitude, is relatively easily solved. By measuring the height of the sun at noon or the position of known stars, a navigator can estimate how far they are from the fixed points of the equator or the poles. It's still a kind of estimation, but at least it's reasonably reliable.

• 7:23Speaker 02

  Dr. Emily Ackerman is curator of time at Royal Museum's Greenwich.

• 7:28Speaker 03

  What sailors used to do was rely on dead reckoning, so this is a method that they measure their speed of travel, their direction of travel, they take into account currents and wind directions, and they're constantly estimating and plotting where they are.

• 7:43Speaker 02

  Though this method gives some certainty of a latitude, the east-west question of longitude is another matter entirely. On land, being wrong about your position might mean a delayed journey or a missed turning. At sea, it can be fatal.

• 8:00Speaker 03

  The problem with longitude is you need a measurement of time because you're measuring the rotation of the Earth.

• 8:09Speaker 03

  So longitude was all about knowing a difference in time. So in theory, it's really simple. If you know a difference in time between two places, so for example Greenwich and wherever you are on the ocean, if you know the difference in time between these two places, you know your longitude. Because Earth spins 360 degrees in 24 hours, you can break this down. So that means 180 degrees in 12 hours, 90 degrees in 6 hours, 45 degrees in 3 hours, etc. So if you know you are 3 hours exactly from Greenwich, you know you are 45 degrees east or west of Greenwich.

• 8:46Speaker 02

  The theory sounds straightforward. In practice, it is anything but. To calculate longitude, you need to know two times at once: the local time on your ship and the time at your reference point far away.

• 9:02Speaker 02

  Local time can be estimated from the position of the sun, though that is dependent on clear skies and careful calculations. But the second value, the time somewhere else, requires a clock that remains precise for weeks, even months, at sea.

• 9:20Speaker 02

  Before the 18th century, no such timekeeper exists. The best clocks of the age rely on pendulums and delicate mechanisms that simply cannot keep steady time aboard a rolling ship with their damp, salty environments and extremes of heat and cold. Without that second measurement of time, accurately calculating longitude is impossible.

• 9:43Speaker 02

  As trade expands and empires stretch across the globe, this problem of crossing vast distances safely and arriving where and when you intend takes on new urgency.

• 10:00Speaker 02

  By the late 15th and early 16th centuries, European voyages are pushing farther than ever before across the Atlantic, around the southern tip of Africa and deep into the Indian and Pacific Oceans.

• 10:13Speaker 02

  Ships sail out heavy with cloth, metalware, weapons and other trade goods, and return heavier still with silver, spices, textiles, and increasingly, human cargo.

• 10:27Speaker 02

  Mergent ventures like the British or Dutch East India Companies establish global networks with navies to protect them. But though entire economies depend on the safe movement of ships across open ocean, the crucial element of longitude remains uncertain. And that is a daily, practical danger.

• 10:49Speaker 03

  It was particular routes, in particular the East India Companies, so the Dutch ones, the English ones. They are sailing down south and they are having to turn east and then they're going to have to head north at the right time. They don't want to go too soon, they don't want to go too late. This could get them into trouble. So for them, it's really important to know exactly when to set that new course for ships.

• 11:13Speaker 02

  A small error in east-west position can have enormous consequences.

• 11:19Speaker 02

  Turn too soon and a ship may miss its destination entirely, lost in open water. Turn too late and it risks running aground on an unfamiliar coast or inadvertently straying into a rival nation's territory, sparking war.

• 11:36Speaker 02

  Longitude becomes one of those rare problems where science, war, commerce and state power all converge. And with the stakes rising, the question is, who will solve it first?

• 11:53Speaker 02

  In the desperate search for a solution, thinkers across Europe propose all manner of ways to determine longitude. But broadly, two approaches emerge. One looks to the heavens, the other to machinery. The celestial approach comes first.

• 12:12Speaker 02

  In the early 17th century, Italian astronomer Galileo Galilei proposes using the moons of Jupiter as a kind of universal clock, since their orbits are regular and predictable. By observing them and comparing their position to tables calculated at your starting point, it's possible to determine how many hours from home you are and from that, your longitude. It's an elegant idea, and on land, it works. But at sea, it quickly falls apart. A telescope is hard enough to use on a stable surface. On a rolling deck, in wind and spray, it becomes almost impossible. Even the most brilliant astronomical solution is useless

• 12:56Speaker 02

  if it cannot be applied in the real conditions of a voyage.

• 13:01Speaker 02

  Still, the idea of using the heavens as a clock gains traction and soon becomes the focus of a major new effort.

• 13:10Speaker 02

  In the late 17th century, the search for longitude is already an international race. Spanish, Portuguese, French and Dutch navigators have all grappled with the problem. And governments across Europe have begun offering rewards for a solution. In the 1670s, a French astronomer called Jean Picard arrives in London claiming he has found an answer by using the moon and stars to determine longitude at sea.

• 13:38Speaker 02

  But when a panel of experts examines his proposal, one problem becomes immediately clear. The method depends on an enormous amount of precise astronomical data. And that data does not yet exist.

• 13:54Speaker 02

  Among those consulted is British astronomer John Flamsteed, who argues that though the system is solid in theory, without far more accurate observations of the heavens, it just can't work. And so, in 1675, under the orders of King Charles II, the Royal Observatory Greenwich is established with a clear purpose of improving navigation by measuring the heavens.

• 14:20Speaker 02

  Under Flamsteed, the first astronomer royal, they begin the painstaking work of mapping the stars. Night after night, observations are recorded and tables compiled of the angles between the moon and a fixed star at any given time in Greenwich.

• 14:39Speaker 02

  In these tables, the astronomers create a reference system that sailors might one day use at sea. And from this effort springs one of the most promising solutions yet.

• 14:52Speaker 03

  So a very important method, which comes into use in the second half of the 18th century is what's known as the lunar distance method, which is basically, at its simplest, you're using the heavens as a giant clock. So the stars form like the dial of the clock and the moon moves relatively quickly against this background. So you're basically using the moon as like the hands of your clock. And it's actually a really complex method, but what you're doing is you're observing the angle, the distance between the moon and the sun or the moon and a fixed star, a star you know the position of. This is where it gets complicated. What the astronomers have done at Greenwich is they have predicted

• 15:34Speaker 03

  at which time that angle will be visible at Greenwich. So you look up that same angle in a table and that gives you your time at Greenwich. So a very complex, but very important method.

• 15:47Speaker 02

  The hope is that by measuring the angle between the moon and a known star and comparing it to the Greenwich tables, a navigator could determine the time back home. From that, longitude might be calculated.

• 16:06Speaker 02

  It is a remarkable solution, but it is mathematically complex. It requires careful observation of clear skies, meticulous measurements and time-consuming calculations. And interpretation of the resulting data requires skill and training. It works, but it's not easy. Worse still, the work required to make it practical takes decades. John Flamsteed spends more than 40 years compiling the necessary observations with sufficient accuracy. Others will continue the work after him, refining and expanding the data.

• 16:44Speaker 03

  It takes 100 years before the nautical almanac is actually published, so before sailors can actually use this method at sea. Because there's so much they needed to know. They needed all this accurate star data. They needed to understand the moon's motion is really complicated. So they needed to understand like how the motion works because everything they need to do is predicting future positions.

• 17:08Speaker 02

  But while the astronomers continue their painstaking work, another idea comes into focus. If longitude depends on knowing the time somewhere else, why not carry that time with you? A portable clock, set to a fixed reference point, could provide the answer directly. But even now, clocks are delicate and unsuited to conditions at sea. No timepiece can survive a long sea journey with its accuracy intact. The search continues, but the stakes are only getting higher as more voyages are undertaken, meaning more ships, cargo and lives lost at sea.

• 17:55Speaker 02

  In 1714, the British Parliament passes the Longitude Act, turning the hunt for a solution into a formal, state-backed challenge. Substantial rewards are offered, scaled to accuracy, with up to £20,000 on offer, around £3.5 million today, for a method that can reliably and repeatedly determine longitude at sea.

• 18:19Speaker 02

  To oversee the process, a group of leading politicians, naval officers and scientists is appointed alongside the astronomer royal to evaluate proposals and to fund and test potential solutions. This body will become known as the Board of Longitude.

• 18:37Speaker 03

  They are the people who oversee the ideas, the schemes, whether they're plausible, whether their ideas deserve merit, whether they deserve a reward and how trials will take place. So if someone comes up with an idea, they might be able to get some money to work on their idea. And if that works out well, then they can ask for a trial. And if they find the perfect way of finding longitude at sea, they will get the reward.

• 19:00Speaker 02

  Now, alongside the learned astronomers and scientists, the field of endeavor widens to include those beyond the established academic world. And in the coming decades, one such maker will emerge from a small market town in Lincolnshire with an idea for a clock that can keep time at sea.

• 19:22Speaker 02

  John Harrison is a man who can turn a skillful hand to many things.

• 19:27Speaker 03

  We don't really know loads about him as a young lad, but he does grow up. He becomes an intelligent young man. He learns lansfering. He learns carpentry. He has an interest in music. He tunes the bells for the local churches. He plays the bass viol. He's the choir master. And he starts making clocks.

• 19:49Speaker 02

  He is not a university-educated astronomer, but he is a practical and talented maker. Working first alone and then alongside his brother James, he sets out to build timepieces of extraordinary precision. But he quickly runs into the limits of existing clockmaking.

• 20:09Speaker 02

  Even on land, keeping accurate time is a delicate business. The performance of a clock depends on the behavior of the materials inside it. Changes in temperature cause metal components to expand and contract, subtly altering their movement. In a pendulum clock, even the slightest variation in length is enough to change the rate at which it keeps time. Since a pendulum is made of metal, which swells and becomes longer as it warms, this is a significant problem.

• 20:43Speaker 02

  There are other issues too. Inside the mechanism, multiple moving parts are in constant contact, creating friction. Clockmakers try to reduce this with oils, but the lubricants available at the time are mostly animal fats, which thicken, dry out, or degrade, and which can introduce further inaccuracy or stop the clock altogether. These fundamental obstacles to accurate timekeeping, for most clockmakers, are simply accepted as part of the craft. But Harrison approaches them differently.

• 21:18Speaker 03

  So basically Harrison, with his brother James, they start making precision clocks. And Harrison has this ingenious way of working and combining materials such as lignum vitae, a tropical hardwood, with self-oiling properties, combining this with brass, and just making his clocks in such a way that there actually is no friction in them. And this is incredibly unusual. And he doesn't require any oiling at all. So he's kind of eliminated one big problem that's causing inaccuracy in clocks. And the other thing he does is this temperature problem. He creates what's called the gridiron system. So to stop the pendulum's length from changing, he comes up with this system of brass and steel rods.

• 22:03Speaker 03

  And because of steel reacts different to brass, to temperature changes, it's cancelling out each other's movement. So it's not affecting the length of the pendulum, which is determining the timekeeping. So these are two huge achievements. And he's doing this in the 1720s. So he could have gone into like the local history books from here, but he hears about this act of longitudes, the rewards on offer, and he thinks he can make a sea clock.

• 22:31Speaker 02

  Convinced that the longitude problem can be solved by harnessing time in a suitable machine, Harrison journeys to London to the Royal Observatory in Greenwich. He meets with the Astronomer Royal, who by this point is Edmund Halley, after whom the comet will later be named.

• 22:50Speaker 02

  Halley is no clockmaker, but likes Harrison's idea. He suggests he meet with one of London's most prestigious clockmakers, George Graham, who already supplies astronomical instruments and clocks to the Royal Observatory.

• 23:04Speaker 03

  John goes to see George and stays all day at George's workshop, chatting about clocks and clockwork. And he stays for dinner and he leaves with an interest-free loan from George, which is very kind of him. And so he goes back up north, back to Barrow upon Humber where he's living. And he and his brother James start working on what's known as H1, Harrison's first sea clock.

• 23:27Speaker 02

  John and James Harrison begin to build H1 in 1731. And four years later, they are ready to demonstrate it.

• 23:37Speaker 02

  The brothers transport the timepiece down to London and show it in George Graham's workshop to much attention and praise. The real question though is whether it can remain accurate at sea. And so H1 is sent on a trial voyage to Lisbon in 1736. It performs well, keeping time accurately enough to correct the ship's longitude during the journey.

• 24:02Speaker 03

  So it did really well. The captain was impressed. But there were sort of like limits of accuracy to which these reward schemes were. So it had to be an accuracy of half a degree, I believe, of longitude to get the biggest reward on offer. And although it was really good and really promising, it was not good enough to go for one of these larger rewards. But it was so promising that the board comes together for the first time. I think they're not a board at this point. I think they just come together as commissioners. You know, are impressed as well by Harrison's clock. And he gets £500 to go away and work on an improved version.

• 24:37Speaker 02

  With that £500, around £100,000 today, the brothers move to London to start work on H2.

• 24:45Speaker 02

  James doesn't take well to the city though, and soon returns to Lincolnshire, leaving his brother alone to his work.

• 24:53Speaker 02

  In London, John Harrison has access to some of the country's finest scientific instrument makers to help his designs. And while H2 looks very different, internally, it's a fairly similar machine to its predecessor. But as work progresses, Harrison begins to see a problem.

• 25:12Speaker 02

  At the heart of the clock are two large, weighted bars, which act as balancing mechanisms that swing back and forth to regulate the timekeeping. They work well in controlled conditions.

• 25:27Speaker 02

  But a ship at sea rolls and pitches, and Harrison realizes that these complex shifting motions will interfere with the movement of the balances in ways he cannot fully predict or control. It is a fundamental flaw, and it cannot be fixed with small adjustments. So Harrison makes the remarkable decision to abandon the H2 design and start again with H3.

• 25:54Speaker 03

  H3 is a fascinating machine. In it, he changes his bar weights. He changes them into two massive round balances. He also incorporates a bimetallic strip. So the temperature compensation is basically two metals fused together, steel and brass. And he puts this in such a way that that will compensate for any temperature changes within the object.

• 26:14Speaker 02

  A version of that device operates inside the thermostat of most modern kettles today. And it's not the only innovation we have to thank Harrison for.

• 26:24Speaker 03

  Another thing he does is the cage roller bearing, again, another anti-friction device, which we now see everywhere in engineering as the ball bearing. So there's some pretty cool parts to H3. But it never works to his expectations. He finishes it in a couple of years, but he spends 19 years working on it. And he never gets it right.

• 26:47Speaker 02

  While working on H3, he commissions a watchmaker to build a much smaller timepiece based on his ideas. In doing so, he introduces a series of crucial refinements, simplifying the design and improving the balance.

• 27:02Speaker 02

  The result surprises even him.

• 27:07Speaker 02

  Though portable watches already exist, they're largely inaccurate. But for the first time, what he produces begins to show real promise as a precision timekeeper at sea. And so in the late 1750s, Harrison turns his attention to a new design, H4, which will be smaller, yet more accurate than any of its predecessors.

• 27:29Speaker 03

  H1, H2, and H3, you probably wouldn't get away with it as cabin baggage anymore. It's slightly too big. H4, easy, so small compared to the others. Compared to pocket watches, it's quite large. You need big pockets, maybe a hoodie. But yeah, so it's a large pocket watch. It's beautiful. It's beautifully engraved. It's a very different looking thing. So it must have been quite a surprise for the board when he suddenly turns up with this big pocket watch.

• 27:54Speaker 02

  Five inches in diameter and weighing only three pounds, Harrison's H4 is minuscule for a sea clock. Its genteel white face is held in a pair of silver cases and three blue steel hands mark out the hours, minutes, and seconds with unerring accuracy. It's unlike anything he's presented before. And according to its maker, it is the most beautiful mechanical thing in the world.

• 28:24Speaker 02

  Within the silver case, the delicate internal workings comprise miniature wheels and cogs, as well as diamonds and rubies to replace the anti-friction systems of Harrison's previous clocks. Finally, almost 30 years since he started work on H1, Harrison duly presents H4 to the board. But their enthusiasm is more muted than he'd hoped.

• 28:53Speaker 02

  By this stage, the role of Astronomer Royal has passed to the methodical, Cambridge-educated James Bradley, a staunch supporter of the lunar distance method, who is himself on the verge of codifying the technique. He views Harrison's timepiece with skepticism, but agrees to a trial. Part of the longitude act is a sea test to prove the accuracy of your solution, all the way to the West Indies and back again.

• 29:22Speaker 02

  The plan is to test both H3 and H4 simultaneously, with H3's progress having been long delayed by the worldwide seven years war. Harrison continues tinkering with H4 for now, while his son William, who has joined his father's business, sails from London to Portsmouth with the cumbersome H3 to await a ship to conduct the trial. After five months of delays, which Harrison attributes to Bradley's interference, the board finally takes action. In November 1761, William finally steps aboard HMS Deptford, bound for the West Indies. But he's only taking H4.

• 30:04Speaker 02

  Convinced that the fundamental design problems of the older version can't be fully overcome at sea, his father has pulled it from the race altogether.

• 30:14Speaker 02

  They're betting the farm on what they call the watch.

• 30:25Speaker 02

  It is the 19th of January 1762 in Kingston Harbor, Jamaica.

• 30:32Speaker 02

  A dry heat hangs over the clear blue water. Gulls, wheel and squawk above as the British naval ship HMS Deptford eases into harbor.

• 30:43Speaker 02

  After three months at sea, travelling all the way from England, they have made it safely to their destination ahead of schedule. Soon, the potentially monumental results of the first sea trial of John Harrison's H4 marine chronometer can be assessed and announced. On the deck, Harrison's son William stands apart from the crew. He has lovingly, carefully wound his father's creation each day, through heat and damp swell and storm, willing it to keep time with the accuracy they need to win the life-changing prize.

• 31:21Speaker 02

  He looks up at the sun, high in the sky, and smiles. By "eye", it's close to noon, but once the exact local time has been confirmed, they will have the answer they've been waiting for.

• 31:35Speaker 02

  He glances over at the captain of the ship, Dudley Diggs, and the two men share a grin. Diggs has already seen the value of this incredible, tiny timepiece.

• 31:47Speaker 02

  Early in the voyage, the crew discovered that several barrels of beer had spoiled, leaving the men unhappily reduced to drinking only water. But William Harrison, trusting H4, predicted that they would reach Madeira within a day, where they could refresh their supplies. Though Diggs doubted both the watch and the forecast, by the next morning, Madeira appeared exactly where William said it would, and the sailors were placated when fresh supplies of wine were brought aboard.

• 32:19Speaker 02

  Diggs was impressed enough to say that when Harrison and his father have their longitude timekeeper available for sale, he wanted to be the first to buy one.

• 32:29Speaker 02

  But it's not just this captain's approval they need. As the ship docks, the board's representative, John Robison, now sets up his astronomical instruments.

• 32:42Speaker 02

  He measures and re-measures the angle of the sun, checks his tables, and, after much calculation, finally establishes the local time. Then he and William fix the longitude of Port Royal by the time difference between here and their starting point in England. Frowning all the while, Robison carefully checks and re-checks their figures. But it is William Harrison who finally beams the full smile of a man vindicated.

• 33:15Speaker 02

  After 81 days at sea, the H4 has lost just five seconds.

• 33:23Speaker 02

  William can't even bring himself to speak. The result is substantially more accurate than the strictest test set by the Board of Longitude. They have done it. H4, his father's labour of love, is proof that time can be carried across the ocean and that longitude can be measured with absolute accuracy.

• 33:53Speaker 02

  By the standards set out in the Longitude Act, the results should be decisive. But instead of celebrating the fact that the longitude problem has been solved, the board demurs.

• 34:05Speaker 02

  The trial has been successful, but it has only been one trial, and their job is to find a method that can be trusted across fleets and oceans. Also, H4 is difficult to replicate, and it costs vastly more than the navigational instruments already in use.

• 34:23Speaker 02

  And so, in August 1762, the board concludes that there is just not solid enough evidence to settle the issue.

• 34:33Speaker 02

  It's not quite back to the drawing board for Harrison, but instead of the £20,000 reward he was hoping for, he receives a mere £1,500 in recognition of the watch's merits, with a promise of a further £1,000 upon completion of further tests. And though he's a big step closer to claiming the prize, he's far from alone in that pursuit. Nipping at his heels is a die-hard lunar distance method supporter called Neville Mascolin.

• 35:04Speaker 02

  Decades younger than Harrison, Mascolin is a Cambridge-trained astronomer, closely connected to the scientific establishment. Working alongside the astronomer royal James Bradley, he has spent years refining the astronomical tables needed to make the lunar distance method usable at sea.

• 35:22Speaker 02

  By the early 1760s, the pieces are finally falling into place. Lunar tables are more accurate than ever, and the instruments for measuring angles have improved. At last, the sky offers a genuinely viable method of calculating longitude.

• 35:38Speaker 03

  It's come to the point where the lunar distance methods, the sextant has been invented, which is an improved angle-observing instrument, the astronomical data is ready, so this method is also now ready to be tested at sea, and it's a lot cheaper. So you can get your nautical tables and your sextant for a lot less money than Harrison's H4. And this is why Harrison starts to see Neville Mascolin as a bit of his nemesis, trying to get the rewards before he can.

• 36:05Speaker 02

  The feeling is mutual, with Mascolin's supporter, James Bradley, reportedly claiming that they would have won the prize already if it weren't for Harrison's plaguey watch.

• 36:16Speaker 02

  Though Harrison's chronometer is impressive, it needs more testing and is expensive. And while Mascolin's celestial solution is cheaper, it also requires further trials and is vulnerable to the whims of Mother Nature. Both have issues, and neither side sees how important they are to one another.

• 36:36Speaker 03

  You can't have astronomy without time, and you can't have time without astronomy, so they're not competing methods. And if you're using a marine chronometer, you need the astronomical data and instruments and angle to check your chronometer. And also, within your lunar observations, you need short-term accuracy for your celestial observations. So, yeah, they are very linked, these methods, and shouldn't really be separated in such a way.

• 37:02Speaker 02

  Yet, with pride and a prize on the line, separated they remain.

• 37:09Speaker 02

  Facing the demand for a further sea trial, in 1764, William Harrison sets out aboard HMS Tartar, bound for Barbados.

• 37:19Speaker 02

  Once again, H4 performs with remarkable accuracy. Over the course of the journey, the watch loses just over half a minute, well within the limit set out by the Longitude Act. In early 1765, the Board of Longitude finally acknowledges that the timekeeper has met the required standard. But still, the full reward is not paid. Instead, Harrison gets half the prize on the condition that he hands over his designs and instruments for inspection and replication. The remaining cash will only be awarded once further copies have been made and successfully tested.

• 37:58Speaker 03

  Eventually, the board commission a watchmaker, Lachlan Kendall, to make copies of H4, and he does, he makes three. They also have fascinating stories, these instruments. The first one sells with Captain Cook, the second one is with William Bligh on the bounty, so he's an unwilling participant in the mutiny that occurs in the late 18th century.

• 38:19Speaker 02

  Between 1772 and 1775, Captain James Cook takes the first replica, K1, on his voyages to the Pacific.

• 38:29Speaker 02

  There, Cook is able to fix his position with unprecedented accuracy, mapping coastlines and navigating safely through unfamiliar waters using the chronometer, which he refers to as "our trusty friend".

• 38:43Speaker 02

  Even as Captain Cook's tests are proving his claim, Harrison remains frustrated with the board's terms for delivering the prize. He takes the extraordinary step of appealing directly to King George III, who agrees to look into the case.

• 38:59Speaker 02

  At Kew, the king personally oversees tests of Harrison's latest timekeeper and finds the results beyond doubt. He declares that if the board won't act, then Parliament must.

• 39:14Speaker 02

  In 1773, after years of dispute, John Harrison is finally awarded a substantial payment by Parliament as recognition at last of what he has achieved. But by now, he is 80 years old and will have only three years left of life to enjoy the fruits of his labour.

• 39:37Speaker 02

  And yet, that's still not the end of the matter. Harrison has answered the question of whether longitude can be calculated accurately at sea. But can it be done repeatedly by numerous captains on any number of vessels anywhere in the world?

• 39:56Speaker 03

  He plays a very important role, but he doesn't solve the longitude problem. It's not that H4 goes to sea and that's it, it's solved. And there is actually not really anything to solve, in a sense, because what you're doing is you're constructing longitude. And you're constructing instruments and measurements from which you're getting data, which you're then putting onto charts, which you're then refining. So the chronometer and all these astronomical observing instruments really come into their own in the 19th century, where they are increasingly used for surveying.

• 40:27Speaker 02

  As the 19th century progresses and more ships set out to discover and chart new lands, the focus of calculating longitude shifts from knowing exactly where you are in the world to knowing what dangers or discoveries lie around you.

• 40:43Speaker 02

  Surveying expeditions spread across the globe, using chronometers and astronomical observations to chart coastlines, fix positions, and identify dangerous reefs and shoals. After all, there is little use in knowing exactly where you are if the waters ahead remain uncharted.

• 41:02Speaker 02

  Among the most famous of these voyages is that of the HMS Beagle, commanded by Robert Fitzroy between 1831 and 1836, with naturalist Charles Darwin aboard.

• 41:16Speaker 03

  The voyage of the Beagle is of course a very famous voyage because of Charles Darwin, but actually it was also creating what was called a chain of meridian distances around the globe. So it sailed with 22 chronometers, and it had the best ones that the observatory had to offer. And they're sailing between two ports as fast as they can, with as many instruments as they can, to determine the time difference and therefore that difference of longitude. And they're doing this as a chain, and this is kind of like creating these anchor points from which you can then connect all your surveys.

• 41:45Speaker 02

  These 22 high-precision timepieces are carefully maintained by Captain Fitzroy and his crew, and are crucial for surveying the South American coast and building up a chain of longitudinal reference points.

• 41:59Speaker 02

  Each voyage helps to define the map of the world. But even with better equipment and better data, a larger problem remains.

• 42:10Speaker 02

  Very few people actually agree with each other's readings.

• 42:15Speaker 02

  The data is pouring in, but not much of it tallies, causing some in the Royal Navy to call for change.

• 42:23Speaker 03

  Henry Raper is a naval officer, and in 1840, he calls on people. So basically, he's saying, there's a lot of data we have, we have a lot of navigational data, lots of places of latitude and longitude, but everyone's measurement of longitude is slightly different. So you can't really collate all this data. So he basically calls for people like, let's just use this as the longitude position for that port. This is the longitude position for that port, and then we can all use the same data. If we then discover that that longitude is an error, then we can correct all the data that is linked to it.

• 42:52Speaker 02

  That need for agreement leads to the even bigger question of where exactly longitude should begin.

• 43:00Speaker 02

  Unlike latitude, which is anchored to the equator, longitude has no natural starting point. Any line could serve as zero. Until now, different nations have used their own starting points. The French use Paris, Britain uses Greenwich, and so on. But this creates confusion and inconsistency. In 1884, the matter is settled at an international conference of 26 nations.

• 43:29Speaker 03

  Greenwich is voted in favor as representing zero degrees longitude, the prime meridian, because of that history of astronomical data collecting and the fact that it's just the basis of so many charts that are in use. There was a two-day discussion on can we have a neutral prime meridian? The idea running through the Pacific Ocean, not going across any territory. But because of the technology, because you are determining position by telescopes on land, you needed a fixed land base. So they were suggesting, well, let's do it 180 degrees from Greenwich. But then other people pointed out, yeah, but you're still using Greenwich, so it's not neutral. It's just appearing neutral. So that takes two days, I believe, that discussion, and they step away from that, and Greenwich gets voted as it will represent zero degrees longitude.

• 44:16Speaker 02

  From this line, the world can now be measured consistently.

• 44:21Speaker 02

  At the same time, a related system begins to take shape.

• 44:27Speaker 02

  If longitude is tied to time, then the world itself can be divided accordingly. The globe is split into zones, each roughly 15 degrees of longitude wide, each representing one hour of time. At the center sits Greenwich, giving the mean time. From there, time is measured forward and backward, plus one hour, minus one hour, until every place on Earth can be located not only in space, but in time. And with the problem of determining exact coordinates now solved, people and goods can be safely transported in vast numbers every day of the year.

• 45:20Speaker 02

  It is a winter night in 2026 in the Thames estuary, just east of London.

• 45:27Speaker 02

  Deep inside the hull of a modern container ship, footsteps ring along narrow metal walkways as a navigator climbs the stairs from the accommodation block towards the bridge to start his shift.

• 45:39Speaker 02

  He pushes open a heavy door to cross a deck.

• 45:43Speaker 02

  Out here, the sea is black, but the shipping lane ahead is busy with movement. Navigation lights drift across the darkness, while the radar turns steadily overhead.

• 45:54Speaker 02

  Heading back inside, the navigator steps onto the bridge. Light spills from banks of instruments and polished screens, where lines, numbers, and moving symbols glow against the glass, each one fixing the vessel's position, its course, and the waters opening ahead.

• 46:13Speaker 02

  He shares a brief exchange with the outgoing officer, confirming speed, heading, traffic, and timings. Then the watch changes hands.

• 46:22Speaker 02

  The ship moves steadily through the darkness, guided by a constant stream of digital information. Latitude and longitude update continuously on the display. The vessel's position recalculated every second with extraordinary precision.

• 46:40Speaker 02

  Beyond the bridge windows, the shoreline of England is still hidden in the dark, just beyond the curve of the estuary. But the navigator doesn't need to search for it. There is no need to strain for a landmark or fear that land may be nearer than it appears. He knows exactly where they are.

• 46:59Speaker 02

  Far above, satellites orbit beyond sight, sending the signals that allow this ship to place itself exactly on the surface of the Earth.

• 47:09Speaker 02

  250 years after John Harrison's death, longitude, the problem that consumed his life, now arrives instantly and silently, embedded in the systems that guide the vessel forward.

• 47:23Speaker 02

  Ahead, the estuary narrows, and through the darkness, the lights of London begin to appear, one by one, marking the channel, the buoys, the distant shoreline, each point of light confirming what the instruments already show. Once, an approach like this would have been made with trepidation and doubt. Now, the ship follows its course as if along an invisible track, joining the queue of other vessels preparing to dock on the Thames tonight. On the bridge, the navigator reaches for the chart display and zooms in. For a moment, he glances from the screen to the darkness beyond the glass. The lights ahead match perfectly. Position confirmed.

• 48:19Speaker 02

  In the end, solving longitude is a long, uneven process of ideas, tested and refined, until eventually, they were made reliable enough to trust at scale.

• 48:31Speaker 03

  It's a very gradual messy process involving so many people, methods, instruments, and different things.

• 48:38Speaker 02

  Harrison proved that time could be carried across the ocean. What followed was the work of turning that proof into practice, and ultimately, mapping the world with a level of precision that had not been possible before.

• 48:52Speaker 02

  Longitude made global navigation safer, faster, and more predictable. It allowed coastlines to be charted accurately, oceans to be crossed with confidence, and distant places to be connected with a new degree of certainty. And over time, it helped fix the world in place, giving every point on Earth a measurable position, allowing us to link space and time in a single shared system that we rely on today.

• 49:21Speaker 03

  We're quite disconnected from the fact that we are on this big rock, spinning round and rounds, you know, circling the sun, and that so much of our lives are governed by it, but that all these systems are still reliant on it, and it still plays such a big role. But I think it's easy to forget that. We don't think about our position here on Earth, we think about out there, but we are out there.

• 49:49Speaker 02

  Next time on Short History of, we'll bring you a short history of Ned Kelly.

• 49:57Speaker 04

  Well, bush range is generally a part of the kind of Australian bush myth, where we've romanticized the bush and all those things with it, the bushman, the bush hero, bullockies and shearers. And by the 1880s, which is right about the time that Ned Kelly was executed, all that was starting to become a mythology, because the country, although it had been very rural previously, was very rapidly urbanizing, and would have very quickly become one of the most urbanized countries in the world. And so this mythology became even more powerful. He's a very, very powerful figure, it's such a great story. It's an Australian story, but it's also an international story. He's the Australian Robin Hood, and that's a very, very powerful mythology.

• 50:37Speaker 02

  That's next time.

• 50:40Speaker 02

  You can listen to the next two episodes of Short History of right now, without waiting and without adverts, by subscribing to Noiser Plus. Just hit the link in the episode description or head to www-noiser.com/subscriptions to unlock more episodes today.