Roman Mars

The reason this fleet was so dangerously off course was because they didn't know their longitude, their east-west coordinates.

It was a problem that had plagued navigators and scientists for centuries.

The greatest minds of Europe, Isaac Newton, Galileo Galilei, and the Halley's Comet guy, they all tried and failed to find a way to calculate longitude at sea.

Most people thought it simply wasn't possible.

What follows is a tale of imperial greed, a lucrative contest, and an obsessive underdog who became his own worst enemy.

Maybe let's give it a try without any citrus fruits.

This grid is what gives us GPS coordinates.

For example, the Pandora building in beautiful uptown Oakland, California, that's around 37.810 north, 122.267 west.

Which was annoying.

Before the age of GPS, the best navigational tool available was the sky.

The sun, the moon, and other celestial bodies were your reference points, no matter where you were in the world.

Getting longitude, on the other hand, is a completely different story.

The reason calculating longitude is so much harder is largely down to the fact that the Earth doesn't stay still.

It spins.

Calculating longitude is like trying to keep track of all the horses on a carousel.

No matter how hard you try, they'll just keep spinning out of sight.

Sailors did manage to get around without knowing their longitude, but not very well.

They were forced to make do with depressingly bad methods.

Which might have been a great idea if it weren't for the fact that pirates also knew these routes, and so they could just sit around doing basically no work and pick off whatever ships they wanted.

This is actually where we get knots as a unit of speed.