The Rise of the Modern Flat Earth Movement
How could people in the nineteenth and twentieth centuries possibly come to think that the Earth is flat?
“It is a most curious thing that in the nineteenth century any man should be found to wager £500 that the Earth was not round.”
— From the judgement in Wallace v Hampden (1871)
In the fens north of Cambridge, near the village of Welney, the Old Bedford River flows through an impressively straight six-mile drainage canal called the Bedford Level. Built in the seventeenth century as part of a series of major engineering works to drain the fens, it directs the wayward waters of the Great River Ouse northward.
On a warm summer’s afternoon in 1838, a man in his early twenties waded into the canal near Welche’s Dam, carrying a telescope. Samuel Birley Rowbotham was familiar with the swampy Cambridgeshire countryside, having spent some months as secretary to the short-lived utopian socialist commune at Manea Fen. Now, he was setting out to test an idea that had stuck with him since childhood. Since he was seven years old, he had been convinced that the Earth was flat.
Rowbotham sent a friend — or assistant — to row a small boat flying a flag five feet above the waterline up the canal to Welney Bridge, at the other end of the straight six-mile section. He then crouched in the water and watched the flag with his telescope held eight inches above the waterline. Standing still in a canal for the time it takes a small boat to travel six miles could not have been comfortable, but Rowbotham was an unusually determined young man. And when the boat reached Welney Bridge and the oarsman lifted his oars, he felt a surge of vindication. “The flag and the boat down to the water’s edge were clearly visible throughout the whole distance!” he wrote.
According to his calculations, the surface of the water at Welney Bridge should have been sixteen feet below the horizon, and hence the flag should have been invisible. Rowbotham had the geometry right but he was ignorant of physics. Warm air over cool water can cause light to refract, creating mirages of ships and islands floating in the sky or making objects beyond the horizon visible. As Rowbotham needed to stand in the canal…