This article was originally published at the defunct Insight blog at Skeptic.com on March 20, 2018. An archived version is available here. Portions of this article appeared previously in Junior Skeptic #53, bound within Skeptic magazine 19.4 (2014).

Recent news stories,¹ celebrity endorsements, and Google search trends² have highlighted an apparently growing conspiracy theory belief that the Earth is not a globe, but instead a flat disc. According to believers, government forces promote a completely fictitious model of the cosmos in order to conceal the true nature of the Earth. Are these claims true?

No. The Earth is Round

The evidence for a spherical Earth is overwhelming.³ Most obviously, there are many thousands of images and videos of the Earth from space, including a continually changing live stream view of the globe from the International Space Station—not to mention all the astronauts who have personally seen the Earth from orbit. Flat Earthers claim that all images of the globe are fraudulent inventions, and all testimony from astronauts is false. It is unreasonable to dismiss all of the evidence from the entire history of space exploration, especially when there is zero evidence for a decades-long “globularist” conspiracy. However, we do not need to rely on evidence from modern space agencies to confirm the roundness of the Earth for ourselves.

The globe has been clearly understood for thousands of years. Indeed, this was one of the first cosmic facts to be worked out correctly by ancient people because evidence of a spherical Earth is visible to the naked eye.

By the time of the philosopher Socrates and his student Plato, many Greeks understood that the Earth could only be a sphere. Sailors would have noticed that the sails of approaching ships appeared before the hulls of the ships became visible because the surface of the sea is slightly curved, like the surface of an enormous ball.⁴ When you sail toward a ship, island, or lighthouse, their tallest points are the first thing to peek up over the curve of the horizon.

Plato’s student Aristotle offered further “evidence of the senses” to support his own conclusion that the Earth “must necessarily be spherical.” First, there was the evidence of lunar eclipses. When the Moon passes through the shadow of the Earth, that shadow is always the circular shadow of a sphere. Also, Aristotle argued, “our observations of the stars” make it clear “not only that the earth is circular, but also that it is a circle of no great size.” He pointed out that “quite a small change of position to south or north” significantly changes “the stars which are overhead, and the stars seen are different, as one moves northward or southward.” Just as ships can be hidden from view by the curvature of the horizon, so too can the stars.⁵

The debate about the shape of the Earth has been settled for over two thousand years. An ancient scholar named Eratosthenes—the head of the famous library of Alexandria in Egypt—even correctly approximated the circumference of the Earth using experimental measurements of shadows in two cities and some geometry.⁶

Despite modern legends about Medieval backwardness, there never was a time when educated people went back to thinking the Earth was flat. Once discovered, the true shape of the globe was too simple and useful a fact to be forgotten. Sailors were reminded of the planet’s roundness every time they climbed a mast to see further over the horizon or looked to the stars to determine their position. By the time of Columbus, his crew and even his critics understood that our world is a globe.⁷ It had been an established fact for centuries. For example, here’s a passage from the popular astronomy textbook On the Sphere of the World, published over 250 years before Columbus sailed:

That the earth, too, is round is shown thus. The…stars do not rise and set the same for all men everywhere but rise and set sooner for those in the east than for those in the west; and of this there is no other cause than the bulge of the earth.⁸

The Nature of Flat Earth Beliefs

Flat Earth beliefs vary, but usually involve a large disc-shaped world with a relatively tiny Sun and Moon circling above it like lamps above a table. Flat Earth maps rearrange the continents and seas to radiate outward from the North Pole, which is imagined to be at the center of the disc. Everything we think of as the Southern Hemisphere is spread out around the outer circumference. It is usually claimed that Antarctica does not exist at all. Instead, the entire disc is encircled by a vast wall of ice that we mistake for a frozen southern continent.⁹

The people who make these claims are not always sincere. There is a long tradition of humorous trolling by people who merely pretend to think the Earth is flat.¹⁰ However, genuine, passionate Flat Earth believers certainly do exist. They typically base their beliefs on two things: intuition and fundamentalist religious faith. The world seems pretty flat when we go about our daily lives. The Bible also contains passages that suggest that our world could be a flat surface covered by a dome (the “Firmament”).¹¹

Throughout the 19th and 20th centuries, Flat Eartherism was primarily motivated by Biblical literalism.¹² Believers saw the globe and astronomy as threats to faith. “No one can believe a single doctrine or dogma of modern astronomy and accept Scriptures as divine revelation,” argued 19th century Flat Earth author John Hampden.¹³

This remains the position of many Flat Earthers today (although the internet apparently also fosters a new more secular¹⁴ conspiracy theory strain alongside traditional Christian Flat Eartherism). Flat Earth believers have long occupied a fringe within the Christian creationism movement, and have been a source of embarrassment for other creationists. For example, the creationist ministry Answers in Genesis has published several articles correctly debunking Flat Earth beliefs,¹⁵ only to be accused of hypocrisy for accepting astronomy while rejecting geology and biology. “The Flat Earth position is first based upon Scripture,” shot back one Christian Flat Earther.¹⁶

Flat Earth beliefs almost require creationist faith because the Flat Earth could not be a natural object. If such a world existed, it could only be an artificial environment constructed on purpose and maintained by forces we do not understand. Left to itself, a disc-world would collapse under its own gravity, forming a sphere like other planets, large moons, and stars.

Since the dawn of the Space Age, Flat Earth beliefs have necessarily also entailed believing that a vast conspiracy deceives us about the nature of the world.¹⁷ “The space program is a scientific plot to hoodwink the public,” claimed Charles and Marjory Johnson,¹⁸ the most prominent Flat Earth advocates during the 1970s, 80s, and 90s.¹⁹ If they were correct about the shape of the Earth, it would follow that a conspiracy must exist to falsify evidence of Moon landings and images of the Earth from space.

However, this claim of a world-wide conspiracy suffers from the same serious flaws as other similar grand conspiracy narratives (such as the “chemtrails” conspiracy theory that aircraft contrails are actually part of a secret global spraying program designed to poison the Earth). First, there is no evidence that any such conspiracy exists. Second, it is implausible to suppose that a conspiracy could exist at that scale for decades without any of the countless thousands of conspirators ever leaking the truth. Third, if a conspiracy was so powerful as to hide itself successfully forever, it would surely also be able stop Flat Earthers from constantly blabbing about it on the internet, newspapers, and television. Finally, it is unclear what could possibly motivate the sustained world-wide effort and expense necessary to conceal the shape of the Earth.

Christian Flat Earthers consider the conspiracy Satanic, which again places Flat Earth beliefs firmly within the sphere of religious fundamentalism. The assumed goal of the round Earth conspiracy is to lead believers astray from their salvation. This has a certain internal logic given their prior assumptions (on faith) of a Flat Earth, a conspiracy, and ongoing spiritual warfare between God and Satan. A round Earth conspiracy seems difficult to justify in secular terms. Why bother pretending the Earth is one shape rather than another? It stretches credibility to accept the motivation that one Flat Earth organization proposes: space agencies are “most likely motivated by greed…and using only some of their funding to continue to fake space travel saves a lot of money to embezzle for themselves.”²⁰

Flat Earth Ideas Make No Sense and Explain Nothing

Like other creationists, Flat Earthers base their arguments on perceived flaws in mainstream science while ignoring major problems with their own claims. They do not provide scientific evidence for their radical alternative model. Nor do Flat Earth models explain the broad range of natural phenomena that are well-explained by the modern scientific understanding of the globe and its place in our solar system: planetary formation, volcanoes, tides, seasonal changes, the phases of the Moon, plate tectonics, earthquakes, the coldness of the poles, the magnetic field that compasses rely upon, auroras, and so on.

The Flat Earth model fundamentally conflicts with the things we see in nature. For example, why would the southern hemisphere’s stars be visible from the opposite edges of a Flat Earth, while people in the central region of the disc instead see the constellations of the northern hemisphere? Shouldn’t the same stars hang over everyone on a Flat Earth like a ceiling hangs over a kitchen table?

Why do the Sun and Moon and stars appear to rise and set? Most Flat Earthers believe that the Sun and Moon are fairly close objects, each just a few miles across, which always hang above the Flat Earth. Supposedly both objects circle around the North Pole on a plane parallel to the Earth’s flat surface while shining down like lamps to illuminate different parts of the disc. (The Sun and Moon are illuminated and kept moving by unknown forces; neither object orbits anything.) If so, the Sun and Moon should be visible all the time from every part of the Earth’s surface. How could such a world ever experience a sunset? We never see the Sun grow noticeably dimmer or smaller with distance as we would in this Flat Earth model; instead, as the globe turns, the Sun passes out of view over the curvature of the horizon.

Flattening the globe also would severely distort the shapes of oceans and continents and the distances between them. Most notably, all proposed Flat Earth maps greatly expand the distances between southern landmasses. Countries that are relatively close together on a globe would be repositioned many times further away on opposite sides of a flat disc-world. In reality, for example, the distance between the northern countries of China and the USA is similar to the distance between the southern countries of Australia and South Africa—and so are the flight times to travel between them. That would not be true if Flat Earth maps were accurate.

All routes for planes and ships would be different on a Flat Earth, especially in the Southern Hemisphere. According to many Flat Earth maps, the shortest flight route between South America and Australia would cross over the North Pole!²¹ A conspiracy to conceal the flatness of the Earth would therefore have to include hundreds of thousands of airline pilots and ship captains as well as governments, space agencies, mapmakers, and Antarctic explorers.

Gravity, Handwaving, and the Supernatural

Flat Earth advocates rely upon made up excuses and invented forces to explain away the problems of their model. They claim that light, perspective, and gravity work differently than we understand from the evidence of science and our senses. Many claim that gravity does not exist at all. This claim is necessary because everyone on every part of the Earth’s surface feels a roughly equal gravitational pull straight down toward their feet, which only makes sense on a globe: gravity pulls everyone down toward the planet’s center of mass. Gravity would feel very different on a Flat Earth. A disc-world’s center of mass would not be located straight down from most parts of the surface. People standing at the central North Pole would feel a vertical downward pull, but everyone further from the center of the disc would feel gravity pull at an angle. At the edges of the disc, the pull of gravity would be almost horizontal. This would pull the oceans and atmosphere inward toward the center of the disc, drowning the center and leaving the outer edges airless and uninhabitable. Standard gravity would also pull down the Flat Earth model’s tiny nearby Sun and Moon to crash into the North Pole. Since none of these things happen, we know the world is not flat.

Rather than confront the problem of gravity, Flat Earthers respond by dismissing gravity altogether. If the “traditional theory of gravitation” is “incompatible with the Flat Earth Model,” then gravity must be weak or nonexistent.²² But if that were the case, wouldn’t you be floating out of your chair right now? Why would objects fall when you drop them? According to one common Flat Earth claim, objects fall because the Earth “is constantly accelerating up at a rate of 32 feet per second squared (or 9.8 meters per second squared). This constant acceleration causes what you think of as gravity.”²³ This handwaving explanation doesn’t work. If our world is accelerating upward, why doesn’t the Flat Earth crash into the tiny Sun and Moon above us? What force could cause the Flat Earth—an entire world—to constantly accelerate at a perfectly even rate? How would the flat surface remain perfectly oriented with the direction of acceleration without ever tumbling (or even slightly wobbling)?

There are no coherent natural explanations for anything in the Flat Earth model. Even when presented in secular language, Flat Earth claims describe an impossible and necessarily artificial world created and maintained through unexplainable miracles. A Flat Earth could only exist through supernatural or technological forces beyond our comprehension.

The Bottom Line

Believing that the Earth is flat requires not only a world-wide conspiracy to fake decades of space exploration, but also the wholesale denial of many branches of science and the evidence of our senses. It requires the invention of new forces and laws of nature without evidence, and implicitly relies upon the actions of a deity-like being or beings.

Despite the rising prominence of Flat Earth ideas, there has never been evidence to suggest that the world could be flat. Advocates simply assume the “obvious truth” of a Flat Earth on the basis of religious faith, intuition, or humor, and then invent a reality to match.²⁴ Although surprisingly frustrating, the rhetoric of Flat Earthers does nothing to change the simple fact, definitively proven for centuries: we live on the surface of a globe.

References

1. See for example Sebastian Kettley. “SpaceX flat Earth SHOCK: Was Falcon 1 Heavy launch faked to conceal planet’s shape?” Express.co.uk, Feb 7, 2018. https://www.express.co.uk/news/science/915948/spacex-flat-earth-falcon-heavy-launch-fake-elon-musk (Accessed March 13, 2018)
2. Google Trends suggest that Google searches for “flat earth” have been climbing since early 2015, with interest since late 2015 remaining consistently higher than any previous period back to 2004.
3. “Spherical” is here used in an approximate sense. For a discussion of the finer complexities of describing the slightly irregular shape of the globe, see Isaac Asimov. “The Relativity of Wrong.” The Skeptical Inquirer, Fall 1989, Vol. 14, No. 1. pp. 35–44
4. The curvature of bodies of water has also been demonstrated experimentally, most famously by Alfred Russel Wallace to settle a wager with Flat Earther John Hampden in 1870. See Richard Milner and Michael Shermer. “Wallace and the Flat Earthers.” Skeptic, 2015, Vol. 20 No. 3. pp. 34–36; and, Daniel Loxton. Junior Skeptic #53, “Flat Earth?! The Convoluted Story of a Flatly Mistaken Idea.” Skeptic, 2014, Vol. 19, No. 4. pp. 70–71
5. Aristotle, translated by J. L. Stocks. On the Heavens. (Oxford: Clarendon Press, 1922.) As transcribed at http://classics.mit.edu/Aristotle/heavens.2.ii.html
6. Carl Sagan. Cosmos. (New York: Random House, 1983.) pp. 14–15
7. Jeffrey Burton Russell. Inventing the Flat Earth: Columbus and Modern Historians. (New York: Praeger, 1991.)
8. Johannes de Sacrobosco. Lynn Thorndike, trans. Tractatus de Sphaera (On the Sphere of the World). (c. Early 13th century, translation published 1949.) As transcribed at http://www.esotericarchives.com/solomon/sphere.htm
9. This alternative cosmos was fully developed by 19th century Flat Earth proponent Samuel Birley Rowbotham. “Parallax.” Zetetic Astronomy. Earth Not a Globe! An Experimental Inquiry Into the True Figure of the Earth: Proving It a Plane, Without Axial or Orbital Motion; and the only Material World in the Universe! (London: Simpkin, Marshall, and Co., 1865.) pp. 20–22, 79–80, 85–87
10. For a prominent example, see the tongue-in-cheek Flat Earth Society of Canada founded by philosophy professor Leo Ferrari and other mischievous intellectuals in 1970. It would be best, schemed one founding member, if people were “not quite sure whether they should take us literally or not.” Christine Garwood. Flat Earth: The History of an Infamous Idea. (London: Pan Books, 2008) pp. 280–314
11. Robert Schadewald. “The Flat Earth Bible.” Bulletin of the Tychonian Society, No. 44, July, 1987. pp. 27–39
12. As skeptical scholar of Flat Earth ideas Bob Schadewald observed in 1982, “to my knowledge, every English-speaking flat earther who has ever lived has actually been a flat Earther because of the Bible.” Robert Schadewald. Lois Schadewald, Ed. Worlds of Their Own: A Brief History of Misguided Ideas: Creationism, Flat-Earthism, Energy Scams, and the Velikovsky Affair. (Xlibris, 2008.) 130
13. Robert J. Schadewald. “Scientific Creationism, Geocentricity and the Flat Earth.” Skeptical Inquirer, Winter 1981–82, Vol. 6, No. 2. pp. 41–48
14. For example, contemporary Flat Earth Society president Daniel Shenton evidently accepts evolution by natural selection. David Adam. “The Earth is flat? What planet is he on?” The Guardian, Feb 23, 2010. https://www.theguardian.com/global/2010/feb/23/flat-earth-society (Accessed March 12, 2018)
15. See for example “They Think the Earth is Flat?” August 9, 2008. https://answersingenesis.org/astronomy/earth/they-think-earth-is-flat/ (Accessed March 13, 2018.) The article dismisses Flat Earth proponents as a “tiny minority of untrained, pseudoscientific hacks who—partially based on an overly literal interpretation of Scripture—buy into a disproven, centuries-old myth rather than accepting well established modern science.” [May 28, 2018 Wayback archive copy here.]
16. Philip Stallings. “The Biblical Flat Earth: A Response To Answers In Genesis.” http://www.philipstallings.com/2016/03/the-biblical-flat-earth-response-to.html (Accessed March 13, 2018). [Dec 22, 2017 Wayback archive copy here.]
17. This became an especially dominant theme during the 1960s as the International Flat Earth Research Society led by Samuel Shenton struggled to rebut news of manned spaceflight into orbit and to the Moon. See Garwood. (2008.) pp. 219–279
18. “Flat Earth Proponent Decries Shuttle Fake.’” The Vancouver Sun, November 6, 1981
19. Schadewald. (2008.) pp. 111–112; Douglas Martin. “Charles Johnson, 76, Proponent of Flat Earth.” The New York Times, March 25, 2001. http://www.nytimes.com/2001/03/25/us/charles-johnson-76-proponent-of-flat-earth.html (Accessed March 12, 2018)
20. “Frequently Asked Questions.” Flat Earth Society. https://wiki.tfes.org/Frequently_Asked_Questions (Accessed March 7, 2018)
21. This would be the case, for example, if the influential maps published by Samuel Birley Rowbotham were accepted. See “Parallax.” (1865.) pp. 21, 35
22. “Universal Acceleration.” https://wiki.tfes.org/Universal_Acceleration (Accessed March 14, 2018)
23. https://wiki.tfes.org/Frequently_Asked_Questions. (Accessed March 7, 2018)
24. As affirmed by Daniel Shenton in 2009, “The Earth is flat. This is a belief I hold as the beginning of an ongoing search for truth and certainty. It is a starting point—an intellectual foundation on which I feel further knowledge can soundly be built.” Daniel Shenton. “In Defense of the Flat Earth.” (Flat Earth Society, 2009.) http://library.tfes.org/library/daniel_shenton_flat_earth_essay.pdf (Accessed March 12, 2018)