This is a companion discussion topic for the original entry at https://biologos.org/blogs/jim-stump-faith-and-science-seeking-understanding/missing-links-february-2-2016
The Flat Earth Society was founded on a scientific proof made in 1838, known as the Bedford Level experiment. A 6-mile stretch of canal ran perfectly straight, and if the earth’s surface is curved, a boat should disappear below the horizon if sighted from one end while traveling along the canal. With the telescope mounted 8 inches above the water, the boat remained completely in view for the entire 6 miles, thereby proving that the earth is flat.
The only problem with this observation was that the temperature difference between the water and the air causes light to bend. One repeat of this experiment found that the boat appeared to rise as it rowed away, suggesting that the earth’s surface is concave. Surveyors already knew about this effect at the time, but people who wanted to believe the earth is flat would not accept explanations.