Longitude

July 26, 2026

AI Summary

5 min read

In October 1707, off the Isles of Scilly, a heavy storm drove a fleet of over 20 English warships homeward from the War of the Spanish Succession. For days, the sky had been sealed with cloud, offering no sight of sun or stars. Without a celestial bearing, the ships had no way to fix their position. The fleet’s commander, Admiral Sir Cloudesley Shovell, one of England’s most experienced naval officers, could only guess where they were. That night, HMS Association—a 90-gun warship—ran aground on the rocks. One after another, HMS Eagle, Romney, and Firebrand followed. Nearly 2,000 men drowned in what became the greatest maritime disaster of the age. The cause was not war or weather, but a problem more fundamental: the inability to measure east-west position at sea. Longitude remained unconquered.

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What you'll learn

1 (00:00) **Advertisements** - Two ad segments for Progressive Insurance and Home Depot.
2 (01:35) **The 1707 Scilly Naval Disaster** - A dramatic reenactment of HMS Association and the fleet of Sir Admiral Cloudsley Shovel running aground near the Isles of Scilly, killing nearly 2,000 sailors due to an inability to determine longitude.
3 (06:03) **Introducing the Longitude Problem** - The episode formally presents longitude as one of the great unsolved problems of the early modern world, sitting at the intersection of science, navigation, empire, and time.
4 (07:17) **The Theory vs. The Practice** - Dr. Emily Akkermans explains the simple theory of longitude (measuring the difference in time between two places) and the impossible practical barrier: no clock could keep accurate time at sea.
5 (10:12) **The Rising Stakes of Global Trade** - As European empires expand, the need for safe, predictable ocean crossings becomes urgent, with merchant and naval fleets losing ships, cargo, and lives due to navigational errors.
6 (12:22) **Two Competing Approaches Emerge** - The search for a solution splits into two paths: the celestial approach (using the heavens as a clock) and the mechanical approach (building a portable clock).
7 (13:39) **The Royal Observatory and the Lunar Distance Method** - The founding of the Royal Observatory Greenwich in 1675 to map the stars, leading to the development of the lunar distance method, which uses the moon as the "hand" of a celestial clock.

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Show Notes

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.

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