Where the F*** Are We?

The Isles of Scilly, an archipelago off the far west of the UK, are home to at least 900 shipwrecks. This treacherous area was the site of the deadliest maritime disaster in British history on October 22, 1707. A fleet led by Admiral Cloudsley Shovel, returning from battle with the French, struck jagged rocks, resulting in the loss of four ships and nearly 2,000 lives. This tragedy occurred because the navigators were 200 miles off course; they knew their latitude but were unable to calculate their longitude, their east-west coordinates. In the 18th century, calculating longitude at sea was considered nearly impossible, a feat comparable to finding the philosopher's stone. While latitude is easily determined by measuring the height of the sun or the North Star above the horizon, longitude is tethered to the Earth's rotation. To determine longitude, a navigator needs to know the exact time at a home port and the local time simultaneously. Since the Earth rotates 15 degrees every hour, the time difference reveals the distance traveled. However, 18th-century clocks were notoriously unreliable. Pendulums were useless on rocking ships, lubrication oils became "gunked up" in salty air, and temperature changes caused metal parts to expand or contract, throwing off the time. Before a solution was found, sailors relied on "sailing the parallels"—sticking to one line of latitude—which made them easy targets for pirates. They also used "dead reckoning," measuring speed by throwing a knotted rope overboard, which is where the unit "knots" originates. Determined to solve the problem for the sake of imperial expansion and maritime safety, the British Parliament passed the Longitude Act of 1714. It offered a massive prize of £20,000 for a solution accurate within 30 nautical miles. While the scientific establishment, including figures like Isaac Newton and Galileo, believed the answer lay in astronomy, a self-taught clockmaker named John Harrison proposed a mechanical solution. Harrison, a carpenter’s son with no formal scientific training, spent years developing H1, a 75-pound brass clock. He utilized innovative features like the "grasshopper escapement" and used lignum vitae, a self-lubricating wood, and bi-metallic strips to counteract temperature fluctuations. To handle the ship's motion, he replaced the traditional pendulum with connected bar balances that compensated for each other's movement. In a 1735 trial to Lisbon, H1 successfully corrected the ship's navigator, proving a clock could work at sea. However, Harrison was a perfectionist. Instead of claiming the prize, he spent the next two decades refining his designs. In the 1750s, Harrison pivoted from large clocks to a smaller "sea watch" called H4. This five-inch-diameter watch used rubies and diamonds to minimize friction. In 1761, Harrison’s son, William,