Christopher Columbus sailed the Atlantic in 1492, thinking he’d found a new route to India. Instead he ran into the Americas, which are nine-thousand miles closer—the name “West Indies” reflecting his enormous error five-hundred-years later.
How could his calculations be so far off? Like all Renaissance scientists and navigators Columbus knew the world was round. What he didn’t know was how big our planet is.
The mathematician Eratosthenes lived in North Africa more than 2000 years ago. Triangulating two Egyptian cities, this amazing thinker extrapolated the Earth’s entire circumference to a high level of accuracy. How accurate? His estimate is within one-percent of today’s GPS satellites’. Since the Earth is 25-thousand miles around there should be no doubt about how far west a journey to India would take.
Unfortunately, Señor Colón did not use the North African’s estimable estimate when crossing the Atlantic. A hundred years after Eratosthenes, an astronomer named Posidonius recalculated the Earth’s circumference using the same methods but inferior data. The result was thousands of miles off, and this circumference became scientific canon for centuries. Colombus compounded the error with additional calculations that made the journey even more optimistic. If he had known the true distance, he never would have sailed. European ships of the day could never carry enough food to reach India because our planet is just too big. The Chinese had huge ships, but Columbus’s were puny in comparison. Lucky for him, the Americas got in the way and his crew survived. For the rest of his life he erroneously thought he had reached the East Indies.
Columbus held a number of other dumb ideas, but this one changed the world.
I’m Jeff Gentry.
Best reference:
SHCHEGLOV, D. A. (2017). Eratosthenes’ Contribution to Ptolemy’s Map of the World. Imago Mundi, 69(2), 159–175.
Dumb Ideas that Changed the World copyright 2023 by Jeff Gentry. All rights reserved.