The Thrilling Tale of Longitude and Our Neurons of Navigation
"Where am I?" is a crucial question for survival. Answering it, from the sci-fi discoveries of navigational neurons to a master horologist forgotten by history, is a tale worth your time.
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We now navigate the world with ease, our location pinpointed by satellites floating high above us in the heavens, but it was not always so. How have our brains evolved to explore a complex landscape? And how did an 18th century government harness the dreams of crackpots and obsessive craftsmen to solve one of the most important questions of them all: where am I? The answer lies with an extraordinary story, linking neurons with naval history.
I: Getting Lost
The thrilling tale of longitude is a story of clocks and kings, but it begins with Sir Clowdisley Shovell of Cockthorpe killing two thousand sailors because he didn’t know where he was.
Shovell, the son of a Norfolk gentleman—apparently a profession of its time—had risen through the ranks of the 17th century Royal Navy, from cabin boy to admiral. Shovell sank pirate ships, fought with the French against the Dutch, then fought with the Dutch against the French. He was widely regarded as a titan of the seas, one of the best sailors of his era.
But his era was not always kind to sailors. In the early 18th century, navigation was still an imprecise science, often requiring dead reckoning, in which haphazard guesswork was combined with intermittent latitude measurements—and a sprinkle of hope—to determine a ship’s location. Calculating longitude was impossible, so sailors knew how far north or south they were, but not how far east or west. And, as you might imagine, that knowledge was rather important if you were sailing full speed toward a coastline.
In 1707, after an unsuccessful naval campaign against the French, Shovell’s fleet was ordered to return home. With fifteen fearsome ships of the line, four fireships, a yacht, and a sloop under his command, Shovell left Gibraltar and set sail for Portsmouth, on England’s south coast. What happened next is subject to legend—perhaps apocryphal, but good yarns nonetheless.
According to the lore, Shovell summoned his senior crew on October 22, 1707, to discuss twelve days of fog—“dirty weather” as he called it—and where they might be. After comparing notes of their varied, but mostly worthless, guesswork calculations, Shovell was said to conclude that the fleet was on course, exactly where it should be.
Then, so the story goes, a lowly sailor did something that lowly sailors aren’t supposed to do: he challenged his superiors. He claimed to have recognized the rocks on the horizon as being part of the Scilly Isles, a shipwreck alley off the coast of Cornwall, the southwest tip of England. He may not have held a fancy rank, but he knew his homeland. According to Dava Sobel’s popular book, Longitude, Shovell “had the man hanged for mutiny on the spot.”1
Soon thereafter, the ships smashed into rocks off the Isles of Scilly. Four of the ships soon began floating on the waves in much the same way that bricks don’t.2 In minutes, nearly two thousand sailors drowned, quite literally lost at sea. It remains, to this day, one of the worst naval disasters in British history. And it all happened because humans couldn’t yet reliably figure out where they were on the oceans.
According to legend, just two men survived long enough to reach the Scilly beaches, and one of them was Clowdisley Shovell himself. As Sobel describes it, Shovell collapsed on the sand, weakened and barely alive, only to be murdered by a local woman who coveted the large emerald ring on his finger. The opportunistic murderer is said to have confessed her crime on her deathbed, “producing the ring as proof of her guilt and contrition.”3
Legend or not, what is certainly true is that two thousand able-bodied sailors were dead—the victims of scientific ignorance in a world constrained by primitive navigation. At a time when empires could rise and fall on the high seas, it became obvious that cracking the code of longitude wouldn’t just save sailors’ lives; it would literally determine who ruled the oceans.
II: Sea turtles, pigeons, and sci-fi neurons in your brain
In the 1860s, sailors captured a sea turtle near Ascension Island, a tiny volcanic droplet of land halfway between South America and Africa. They branded the turtle, then brought it back with them to Europe. But when they reached the English Channel, the animal looked unhealthy, so they tossed it overboard.
Two years later, the same sea turtle was caught again near Ascension Island, almost certainly after it had made its way back to the turtle feeding ground in Brazil. How on Earth had that turtle navigated its way, apparently effortlessly, from a place it had never been, straight back to where it belonged?
Many species traverse the planet with astonishing ease. In addition to the long distance travel of sea turtles, arctic terns can flit back and forth between the two poles, soaring from the Arctic to the Antarctic, traveling between 25,000 and 50,000 miles per year. Monarch butterflies migrate across generations, a familial relay voyaging across thousands of miles.4 Pigeons can be deprived of any sensory inputs, moved 60 miles, and still find their way to the right location without much fuss. Meanwhile, many of us would be lost without Google Maps.
A generation ago, the notion that animals used “magnetic maps” to navigate—effectively having their own version of longitude and latitude that is tied to Earth’s magnetic field—was contentious, to say the least. Now, it’s widely accepted; birds, salmon, sea turtles, and other species use magnetism to get around the globe. (In experiments, scientists even found evidence that magnetic maps may be inherited across generations).
However, not all animals rely on magnetism. It turns out that sailors aren’t the only ones to use dead reckoning to figure out where they are. We do it all the time, using a process known as path integration, in which we—and other animals—intuit relative location based on a constantly updated sense of velocity, direction, distance, and so on.
Path integration is the reason why we’re able to have a rough sense of which way to turn to head back somewhere, even if we’re taking a new route. We all have an idea of where we just came from, automatically and constantly updating, in our heads.
How do we do that?
Now we enter the realm of apparent science fiction, as we look inside our brains. We have two distinct kinds of navigational neurons: place cells and grid cells.
Place cells fire when we are at a specific location. (It is quite literally true that a set of neurons will fire when you are at your house, or your favorite restaurant, but that exact pattern will fire nowhere else). Grid cells fire at regular intervals as we navigate the world, producing a hexagonal pattern that allows us to understand where we are, with multiple layers of granularity. How this works remains a mystery, one of the many perplexing secrets housed in our skulls. (My colleague, Neil Burgess, at University College London, is one of the leading experts on place cells and grid cells, and his TED talk below is worth your time).
However, even with this neuronal wizardry, we have limits. Place a human on a ship in vast seas, and we can quickly get lost amid the vast expanse of featureless blue surrounding us. Sailors might be able to navigate a new port using grid cells and place cells, but it won’t help them avoid getting shipwrecked off the Isles of Scilly. And Clowdisley Shovell, like the rest of us, didn’t possess the magnetic acuity of a sea turtle.
How, then, did humans first solve the problem of navigating the open oceans?
III: The Longitude Problem
Navigation requires a combination of two coordinates: longitude and latitude. Latitude was easy, whether on land or at sea. It could be quickly calculated using the position of the sun at noon, or by using the North Star at night (in the northern hemisphere).
Longitude, however, was more complex. It can be calculated by time. The 360 degrees of the Earth’s sphere can be broken down into 24 hours, meaning that each hour represents 15 degrees. London and New York are approximately 75 degrees of longitude apart, which is why five time zones separate them (75 degrees / 15 degrees per hour = 5 hours).5 So, in order to figure out how far east or west you have traveled from a given location, you need only know:
What time it is in the place you left (such as London)
What time it is where you are now (in the open ocean, for example)
Once you have those two data points, you can calculate how far away you are from the point of origin, or in the case of a ship, from your home port. As a result, if you can see the sun or the stars (for latitude)—and also accurately measure time (for longitude)—you can know, with tremendous precision, exactly where you are on the planet.6 No GPS required.
However, in the early 18th century, when Clowdisley Shovell got two thousand men killed after getting lost, it wasn’t possible to accurately calculate time at sea. The reason was straightforward: every accurate clock of the time relied on three mechanisms that were rendered completely useless while on a sailing ship.
A pendulum clock requires stability; it obviously cannot work on a ship that is constantly tilting and wobbling on the waves.
Clocks were lubricated with oil, which would become more or less viscous over time, particularly as it moved from tropical climes to chilly ones
The metal that formed a clock’s pendulum would expand in heat and contract in the cold, meaning that the pendulum would be longer in tropical areas and shorter in temperate ones, messing up the timekeeping.
These three problems meant existing clocks were dead weight onboard any oceangoing vessel. Many of the best scientific minds of the day—including Sir Isaac Newton—gave up on tackling the longitude problem, considering it unsolvable, a scientific impossibility.
But accepting defeat in longitude would ensure that naval navigation would remain as guesswork—and more Clowdisley Shovell-style tragedies would inevitably unfold, costing precious cargo and countless men.
Then, in 1714, Parliament passed The Longitude Act of 1714, an early form of an X-Prize, in which roughly two million pounds (in today’s value) would be awarded to anyone who solved the longitude problem.7
Old-timey prose is always lovely, so here is how one case was made for the necessity of the act:
If to carry Ships in Safety, to give Help to People tost in a troubled Sea, without knowing to what Shoar they bear, what Rocks to avoid, or what Coast to pray for in their Extremity, be a worthy Labour, and an Invention that deserves a Statue.
It wasn’t just because of Clowdisley Shovell, either; mapmakers couldn’t create accurate charts because of longitudinal imprecision, and trade riches were slipping beneath the waves, too. With London established as the most important port in the world, solving the longitude problem wouldn’t just save lives; it could unleash a world-changing empire.
Pushing hard for the Longitude Act were a certain Humphry Ditton and William Whiston, who believed they had cracked the case after “an intoxicating afternoon with several friends, who were sworn to secrecy” (translation: they got drunk and, like many drunk people, wrongly believed they had invented a rather clever idea).
Their idea was to permanently anchor a series of ships at regular intervals across the Atlantic, for example, and have them signal the local time—say noon—using either a loud cannon boom, or through the visual cue of an aerial rocket.
How this would work was unclear—and it lingered on as one of the many slightly crackpot ideas that gummed up the work of the committee overseeing longitudinal progress. (One satirical idea, channeling the sadistic 18th century impulses of Kristi Noem, involved sticking dogs on ships, wounding them, then touching a magical powder back in London that would instantaneously cause the dog to cry out, allowing sailors to know the time back home through this fantastical canine clock).
Soon, scientists working for the prize became regarded as the “longitude lunatics,” fools tilting at scientific windmills, because only crazy people would try to solve such an obviously impossible problem. Hogarth mocked them in the artwork below, depicting an insane asylum filled with people hoping to secure their riches through science.
Jonathan Swift even mocked Ditton and Whiston directly, writing the memorable lines:
The longitude miss’d on / By wicked Will Whiston / And not better hit on by good Master Ditton
So Ditton and Whiston / May both be p-st on / And Whiston and Ditton / May both be sh-t on
Suffice to say, there was not much optimism that the longitude problem could be solved—or much respect for those who sought to slay the uncertainty of the seas.
IV: The Forgotten Clockmaker
John Harrison changed everything.
Harrison had little formal education, but was masterful working with wood and was fascinated by clocks.8 At first, he had difficulty convincing the scientific establishment of his ideas, but soon, his clocks dazzled. He refined them over decades—in one case spending seventeen years working on a single clock—producing five timepieces, the first working marine chronometers. Little by little, they improved, making it plain that scientific impossibility was becoming reality, forged through the determination and inventiveness of a self-taught craftsmen with a laudable obsession with problem-solving and timekeeping.
Harrision came up with several innovations that changed not just marine history, but world history. His clocks solved the problem of oil by designing it away; his timepieces—seemingly miraculously—employed several new anti-friction devices, facilitated by, among other innovations, using a naturally oily wood. Then, taking his genius one step further, Harrison invented the caged roller bearing, a nearly frictionless mechanism that later helped unleash the industrial revolution by improving machinery. Caged roller bearings are still used in “virtually every complex machine made today.”
To solve the problem of pendulums that elongate or shrink in varied climates, Harrison invented a bimetallic mechanism of canceling these expansions and contractions out. By combining brass and steel, he could effectively ensure that any bit of the mechanism that elongated would be offset as “the downward expansion of the steel rods is counteracted by the upward expansion of the brass rods.” Harrison’s related invention of the bimetallic strip is still used today and has been instrumental in thermometers, gas safety valves in ovens, electric circuit breakers, and cars, to name a few.
But beyond their role in scientific progress, Harrison’s clocks are works of art. I visited those displayed at the Royal Observatory museum in Greenwich recently, standing in awe before the presence of intricately beautiful objects that helped humanity navigate across centuries. Here, for example, is a video I took of his first attempt: H1—still working today.
Decades later, after two additional refinements, Harrison produced the much smaller H4, an exquisite bit of craftsmanship that was also one of the finest clocks ever made.
His final clock, H5, produced impeccable accuracy, no matter the turbulence on the oceans. To the 18th century mind, Harrison had done the impossible.9
V: Harrison’s Legacy, Government Prizes, and the Incuriosity of Modernity
For centuries, Harrison’s innovations changed history, and revolutionized navigation on the seas. That only changed in the early 20th century, when the wireless telegraph and radio signals made it possible to transmit time signals across vast distances to shipboard receivers. Finally, GPS—using satellites—eclipsed methods that relied on earthbound timekeeping.
But the tale of longitude—and the ongoing scientific sleuthing into the neurons we use to navigate across shorter distances—yield three important lessons.
First, government prizes can act as a crucial catalyst for scientific innovation. The industrial revolution and the rise of British naval superiority were both partially unleashed due to an investment of just two million pounds in today’s value. We should be developing many more state-funded scientific prizes today, particularly for research into neuroscience, as the 21st century will likely be defined by our understanding of complex cognition, both artificial and human.
Second, scientific snobbery—and excluding people from innovation based on credentialism—could have kept Harrison’s ideas from emerging, delaying crucial progress. It’s a cautionary tale for the modern world, in which our degrees are often wrongly imagined as an accurate shorthand for our intellectual worth.
Finally, the tale of longitude highlights the intellectual incuriosity of our modern age, in which we, to an unprecedented degree, drift through the world while rarely pausing to ask “how does that work?” We happily tap our destination into Google Maps, never wondering how the solution to what is now such a banal task as navigation changed the fate of the world forever.
In one wonderful psychology study, participants were asked if they knew how a toilet worked. “Of course!” the participants replied. “Great!” said the scientists. “Please write down, or draw, how it works.”
At that point, the participants realized they had no idea how a toilet works much beyond how to make it flush. As
highlights: “This isn't specific to toilets—you can get it with everything from spray bottles to helicopters.” This is known as the “illusion of explanatory depth,” where we imagine that we understand something, but are completely flummoxed when we’re asked how it actually works. Gravity is another great example. (Try explaining, in detail, exactly why stuff falls down, other than saying that masses exert forces on each other. Sure, but how?).The point, then, is that human problems are often best solved by diverse—but stubborn thinkers—who are insatiably curious and relentlessly ask two simple questions that we mostly take for granted: “Why?” and “How?”
Countless lives were saved and the trajectory of world history shifted across centuries, all because one clockmaker couldn’t get those questions out of his head.
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This probably never happened. Sobel’s work is brilliant and elegant prose, but these historically inaccurate stories are presented as ironclad fact in her account.
Yes, this is a riff on one of my favorite turns of phrase from Douglas Adams describing the Vogon fleet.
This also probably never happened.
For an excellent discussion of both the longitude problem and John Harrison’s clocks, see Jonathan Betts, “John Harrison and the Quest for Longitude, 2nd edition.”
Another method of calculating longitude relied on tracking the movements of the moon. The Royal Observatory in Greenwich, London (where the Prime Meridian is now fixed) was established to better understand this method of navigation, but it often took up to four hours to calculate—and it was impossible to use when it was cloudy or if the moon was in its new phase and was therefore dark. Much of this story relates to Edmund Halley, of Halley’s Comet fame.
The payments would be certified, then paid out, on a sliding scale, by the level of accuracy.
For a fuller picture of this extraordinary person, read Dava Sobel’s book, Longitude.
His battle to collect the prize money was contentious, but he eventually got some of what he was due according to the act of Parliament.
One thing most people don't realize is the the GPS system is all based on time as well! The triangulation is highly intricate, relying on time lapses between radio signals between the satellites and the receiver. The time pieces in the satellite system rely on atomic decay and are reliable down to 3 nanoseconds. Yes, that is 3 billionths of a second. Hence, we have incredible accuracy for about any place on earth receiving the signals from them.
Sobel’s “Longitude” is an entertaining and thrilling read. When I read it, I probably assumed that the political dynamics challenging Harrison’s inventions were a thing of the past. Sadly, the Covid era disputes that.