The idea of a Flat Earth is firmly at the far end of the conspiracy spectrum. It's an extreme conspiracy theory because the belief requires that you accept that the entire space program is a fake, designed to cover up hundreds of years of an even deeper scientific conspiracy to hoodwink people into thinking the earth is round (for no good reason). On the Flat Earth GPS does not work by satellites, but from radio towers, flights between Australia and South America are fake, the sun sets via a bizarre interpretation of "perspective", and Antartica does not exist.
To the person first looking into this theory it can be difficult to believe that the proponents actually take themselves seriously. And indeed many of them do not. Many Flat Earth popularizers are simply doing it for fun, or to make a philosophical point about people's over-reliance on the authority of science. But there are are also people who take it very seriously. Mostly they do so for religious reasons - feeling that a literal reading of the Bible (or sometimes the Koran) indicates the Earth is flat.
So what's a debunker to do? Religious beliefs are largely faith-based, and so not susceptible to reason. But the Flat Earthers attempt to provide scientific proofs of their theory, and some even claim not to be at all religious, and to be approaching it from a purely scientific viewpoint.
To understand a subject it's very useful to understand its history, and to be effective in debunking a subject, you would do well to understand the history of debunking that subject. To that end I highly recommend the book Flat Earth: The History of an Infamous Idea, by Christine Garwood.
The book details the history of ideas about the shape of the Earth, going back to ancient times. But the focus of the book is on the flat Earth movement that sprang up in the late 1800s. An integral part of the story is the role of skeptics and debunkers who attempted to address the issues. There were many points in the book at which I literally laughed out loud with recognition. Not only at situations repeated recently in in flat Earth debunking, but more generally at how the events surrounding the flat earth debate mirrored the debates over more modern conspiracy theories like "chemtrails".
The book opens with a prologue: The Columbus Blunder, describing the origin of the misconception that Columbus proved the Earth was round. In fact the rotundity of the Earth had been known for thousands of years, and very few people of learning doubted it at the time of Columbus' journey. The misconception came about from a colorful account of Columbus' life written by Washington Irving (author of Legend of Sleepy Hollow).
Garwood identifies the Columbus myth as being central to the modern misconception that until recent times everyone though the Earth was flat. This creates the backdrop for the first chapter Surveying the Earth, where she details the evolution of ideas about the shape of the Earth. The shift in thinking from flat to round is identified as being about 2,500 year ago, in the time of Pythogoras, then Plato and Aristotle. While interesting, this chapter is perhaps a little dry, and might put off the casual reader. It can quite safely be skimmed. The important points simply being that the shape of the Earth was discovered (and proven) many hundreds of years ago.
Subsequent chapters are more interesting, as they are arranged more like character portraits. Mini-biographies of the key figures in the flat Earth movements. Often overlapping, they detail the struggles of professed believers - some genuine, some joking, some possibly charlatans. Interwoven are the stories of those opposed to the spread of the false idea.
Chapter two, A Public Sensation, tells the story of Samuel Rowbotham, and opens with:
Here we are introduced to the idea of "zetetic" thinking, a concept that is key to understanding the mindset of the flat Earth believer, both old and new. Pure zeteticism is essentially a form a scientific skepticism where ideas are believed only if you can personally verify them. It is perhaps the ultimate form of "do your own research" where not only do you have to research the evidence for an idea, but you also have to research the very foundation of science itself.
The zetetic mindset has a surprising amount in common with the scientific skeptical mindset. The primary difference being that the scientific skeptic builds upon the solid foundation of established science, while still being open to that science being proven wrong. The scientific skeptic focusses on extraordinary claims that are at odds with established science. The zetetic, on the other hand, treats all claims as extraordinary - often relying more on a sense of personal incredulity to identify things to be suspicious about. The sun does not seem to be 93 million miles away, so for a zetetic it probably is not. Earth does not feel like it is spinning round at 1000 miles per hour, so for a zetetic it seems more likely that it is stationary. It looks flat, so it probably is flat.
The chapter details Rowbotham's attempts to popularize the flat Earth theory via a series of writings and public lectures. Somewhat at odds with zetetic philosophy he also argued from the evidence of the Bible (which he simply accepted as a universal truth). But religion was not the only motivating factor for early flat-earthers, as Garwood describes in her picture of one of Rowbotham's early converts, William Carpenter:
The quote "find out for yourself" was the first thing in the book to make me chuckle, for it so closely resembled the modern refrain "do your own research". More chuckles were to follow.
In 1864 an analog version of the internet existed in pen and ink. Communication was much slower. E-mail was real mail, and discussion forums were either real-life meetings or the letter pages of newspapers. The exploits of "Parallax" were often covered by local newspapers, and the letters that followed bare a striking similarity to the comments sections of more modern times.
The amateur debunkers emerge! And with such similarity to the modern flat earth debunker. Many of the arguments you would read today in a flat earth forum were first made 150 years in letter form. Including laments about the state of the education system:
And the tactics used by Rowbotham also seem to ring a bell:
A series of pat answers, and then when he finally hits an objection he cannot answer he simply leaves. Many of us have experienced similar things with chemtrail believers.
The term "conspiracy theorist" was unknown back then, and not really applicable in the time before the space program required a deep conspiracy as explanation. In the late 1800s the term "paradox" was used for an unusual idea that contradicted known science, and "paradoxer" would somewhat be the equivalent of "conspiracy theorist". Debunking at the time might have been called "de-paradoxing", and we have some 19th century debunkers in those that addressed the paradoxers.
In the same chapter as the slick flat-earth salesman Rowbotham we are introduced to the more strident figure of John Hampden, a christian driven by his faith to promote the flat earth idea, rather less politely than Rowbotham:
Another chuckle there, for what modern debunker has not been accused of being a "government shill", "bribed in secret"?
The characters (Rowbotham, Carpenter, and Hampden) fully established, we come to perhaps the most well known episode in flat earth history with chapter 3, The Infamous Flat Earth Wager. This details a wager proposed by Hampden in 1870:
There are shades here again of modern theorists who offer cash for people who can prove them wrong. Generally though such modern challenges (such as the "Hiewa Challenge") are less tractable than this one, which seems like a pretty sure bet to anyone with surveying experience. And indeed one such man was Alfred Russel Wallace, the co-discoverer (with Charles Darwin) of the theory of evolution and natural selection.
Wallace was an interesting character. While a man of science, he was also convince spiritualism was real and attested to observing supernatural events (including levitation) during seances. This placed him somewhat on the outskirts of science, frowned upon by his contemporaries. His taking up of the wager did not help, with many feeling he was taking advantage of the mentally confused Hampden.
But the wager went ahead. The six mile long canal known as the Bedford Level was the location agreed upon. The first attempt involved fixing six flags at equal heights above the waterline, and then viewing them through a telescope. If the flags were in line that would show the water was flat, and if the middle flags were raised, then it was curved. Unfortunately it was not so simple:
So a second experiment was devised, a simpler version with taller targets that we now refer to as the "Wallace Experiment"
This was carried out, and the middle marker was observed to be several feet above the other markers, thus proving the surface to be curved. Unfortunately the "independent referee" John Carpenter had a bizarre reaction to the observation, literally jumping for joy and declaring that this proved the earth was flat.
Arguments followed, however the holder of the stakes, John Walsh, was quickly swayed to the side of Wallace, especially after discovering that Carpenter was not independent at all, and after a few weeks the fully sum of £1,000 was paid to Wallace. Hampden was apoplectic with rage.
Chapter 4, Trials and Tribulations, details the decades long aftermath of this wager. Hampden insisted that he had been cheated. He wrote many libelous letters to (and about) Wallace, and even threatened him with violence. Eventually Wallace sued him for libel, and Hampden was fined and eventual imprisoned several times. This was financially difficult for Wallace, who had little in the way of income from his work. It nearly led to ruin when six years after the fact a court decided that since Hampden had asked for his stake back before the wager was complete, then Wallace actually had to repay Hampden his £500. Wallace however continued to flirt with the flat earth idea.
Rowbotham (Parallax) continued apace, and new "debunkers" arose to challenge him. One notable being Richard Proctor:
I find Proctor's approach fascinating, because it closely matches my own "ask them to explain their views and to remove the difficulties" - i.e. ask them why they believe as they do (their evidence) and then find the errors in their reasoning or claims of evidence. Debunking.
The chapter wraps up the lives of the key characters. Wallace secures a government pension and lives a quiet life, somewhat regretting he ever got involved, reflecting that ‘fifteen years of continued worry, litigation, and persecution with the final loss of several pounds’ was not worth the wager, which he finally considered to be somewhat unethical, as he knew the outcome in advance.
Rowbotham continued to fight for his beliefs, and died while in the middle of a legal battle involving them. Hampden likewise continued to obsess over Wallace to the end of his days.
The three chapters relating the exploits Rowbotham, Hampden, Carpenter, and Wallace were for me the heart of the book, the foundational tale that was largely repeated with different flavors in later chapters.
Chapter five - Lady Blount and New Zetetics recounts the tale of Lady Elizabeth Anne Mould Blount, an aristocrat who took up the cause, and pursued it with considerable vigor. She published many books and pamphlets. Interestingly she, like Rowbotham, was an advocate of alternative medicine:
There is a similar modern obsession with health to be found in many conspiracy circles. Promoters of conspiracy theories like Alex Jones sell snake-oil remedies like "Survival Shield X-2" or "Super Male Vitality" - not really different in idea to Lady Blount's Muric Acid.
Chapter Six - Flat Earth Utopia - covers Wilbur Glenn Voliva, a deeply religious man who led Zion City - a planned fundamentalist christian community of 60,000 in Illinois. Voliva recited the arguments easily, and was immune to reason. After being asked a series of questions by a young Irving Wallace, he easily rattled off the answers:
And had similar nonsensical explanations for gravity, still used today by people who assert things fall because of "density"
Chapter Seven - Man on the Moon - covers Samuel Shenton, the leader of the International Flat Earth Research Society, in England in the 1950s onwards. This time was uniquely challenging for Flat Earther, as the space program was getting into full swing, and each new event - satellite launches, space walks, the Apollo missions around the moon, and finally the moon landings themselves - seemed like fatal blows to the flat earth idea. Shendon claimed to be initially disheartened, but quickly recovered and simply doubled down by claiming that they were all fake, the entire space program was fake, and the astronauts were either lying or had been brainwashed. He became a popular fellow for the press to interview after every success in space, but he continued on his path.
As before, Shenton received correspondence from critics and debunkers:
Of course their careful diagrams did not work, Shenton continued his work until his death in 1971.
Chapter Eight, The View From the Edge, is rather different in that it details the work of Leo Ferrari with the Flat Earth Society of Canada. FESC was actually a satirical organization - part joke, and part philosophical statement on the over-reliance on science and technology. Ferrari explained in an interview with J. William Johnson:
This message caught the attention of astronomer Bryan Andrew:
I suspect many people who currently argue for a flat Earth do so for similar reasons. But it's very hard to tell.
Chapter Nine - The Californian Connection - tells the tale of Charles Johnson, a flat Earth promoter who was not joking. In fact he essentially inherited the International Flat Earth Research Society from Samuel Shenton, setting it up again in California as the IFERSA ('A' for America). The IFERSA had over 200 members, and is somewhat reminiscent of a type of "alternative" Facebook discussion group which provides a safe place for beleivers, but bans dissenting opinion:
Schadewald became an expert on the Flat Earth belief, wrote often about them, and worked on a book on the subject. A perfectionist, he unfortunately did not finish the book, but it was finished posthumously, and can be read online. It is very similar in structure to Garwood's book.
In the epilogue - Myths and Meaning, Garwood reflects on the Flat Earth movement. Easily dismissed and ridiculed, instead Garwood argues we should learn from it because it makes valid points about how we know what is true, and what the role of science is in that knowledge.