Bedford Level experiment

The Bedford Level experiment was a series of attempts, beginning in the late 19th century, to show the curvature of the Earth's surface. First conducted by Flat-Earther Samuel Birley Rowbotham, observations along a long straight stretch of drainage canal in the English county of Norfolk seemed to confirm that the Earth is flat.

The basic idea was to use a surveyor's telescope to observe marks at a uniform height above the water, spaced three miles apart. If the earth is curved, the marks will not line up. Mariners had been correcting their lunar sights for the of light near the horizon since the eighteenth century, but the flat-earth proponents failed to account for it, and claimed the observed misalignment was much less than the crazy Round-Earth fanatics had predicted.

Years later, Rowbotham's results were taken up by one of his supporters, one John Hampden, who wagered a bet that he would prove the earth is flat. Alfred Russel Wallace took him up on this, and by accounting for optic refraction, he repeated the experiment and showed the Earth to be curved. Wallace was judged the winner by the editor of The Field (a gamblers' magazine), but Hampden claimed Wallace had cheated. Death threats, libel cases, and Hampden's incarceration ensued.