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The Flat Earth

The “Wisdom” of Celebrities

In 2016 and 2017, the media were abuzz with reports of yet another celebrity suggesting that the earth is flat. Most of the coverage was incredulous and slightly sarcastic, but by giving these ridiculous ideas so much coverage, the media ended up spreading the ideas more widely and even, to some extent, legitimizing them. As tabloid journalism has practiced for years, “if it bleeds, it ledes,” and this is even more true now. In today’s media world, the whole point of reporting something sensational or crazy, no matter how ridiculous it is, is to get attention and more hits on the website or to sell more magazines. After all, the bottom line is what matters, not the objective truth. But media reports seldom give a critique or a detailed explanation of why 99.99 percent of the world doesn’t think the earth is flat.

The media had already created a fuss in 2008 when Sherri Shepherd of the morning talk show The View and reality TV personality Tila Tequila said that the earth is flat, or at least questioned the idea that the earth is round.¹ (These same people espoused other discredited notions as well: Shepherd is a creationist, and Tila Tequila has preached a wide variety of controversial ideas, including neo-Nazi antisemitism). A number of prominent professional athletes, including Denver Nugget forward Wilson Chandler,² Cleveland Cavalier (now Boston Celtic) guard Kyrie Irving,³ retired NBA center Shaquille O’Neal,⁴ and Minnesota Vikings wide receiver Stefon Diggs,⁵ also came out for the flat-earth notion in 2017 and 2018. Irving explained his thinking in the following words:

Is the world flat or round?—I think you need to do research on it. It’s right in front of our faces. I’m telling you it’s right in front of our faces. They lie to us…. Everything that was put in front of me, I had to be like, “Oh, this is all a facade.” Like, this is all something that they ultimately want me to believe in…. Question things, but even if an answer doesn’t come back, you’re perfectly fine with that, because you were never living in that particular truth. There’s a falseness in stories and things that people want you to believe and ultimately what they throw in front of us.⁶

O’Neal is a famous prankster who loves to punk reporters with outrageous statements. He later admitted he was joking just to get a reaction out of people.⁷ Irving eventually retracted his statements and gave a public apology to America’s science teachers.⁸

The biggest public outrage was the reaction to statements made by rapper B.o.B., whose legal name is Bobby Ray Simmons Jr. B.o.B has advocated the full range of conspiracy theories, including the idea that the moon landing was a hoax, 9/11 was an inside job, the Illuminati are trying to establish a New World Order, Jews are secretly in control of everything, and the US government is actively cloning people. Not only did he start a Twitter war about his beliefs, but he upped the ante, getting into a rap battle with astronomer Neil deGrasse Tyson,⁹ repeating all the usual debunked claims of flat-earthers, and even setting up a GoFundMe campaign to raise $200,000 for his own rocket to send up a satellite so that he could see for himself. Like most flat-earthers, he believes that everything from NASA is a hoax, so he wants to do it himself. The idea of sending his own rocket up would be laughable if it were not so sad, and it doesn’t consider the problem that even a cheap satellite launch costs about $62 million. Then he recorded and released a rap video called “Flatline,” expanding on his ideas, challenging Tyson directly, and even mentioning the noted Holocaust denier David Irving. Some of the lyrics include

Aye, Neil Tyson need to loosen up his vest.

They’ll probably write that man one hell of a check.

I see only good things on the horizon.

That’s probably why the horizon is always rising

Indoctrinated in a cult called science

And graduated to a club full of liars.¹⁰

Not to be outdone, Tyson wrote his own rap song, “Flat to Fact,” and his nephew, Stephen Tyson, rapped and recorded it. Some of the lyrics include

Very important that I clear this up.

You say that Neil’s vest is what he needs to loosen up?

The ignorance you’re spinning helps to keep people enslaved, I mean mentally.

All those strange clouds must be messing with your brain.

I think it’s very clear that Bobby didn’t read enough

And he’s believing all this conspiracy theory stuff.¹¹

In March 2018, in a flat-earther stunt, motorcycle racer, daredevil, and limo driver “Mad” Mike Hughes launched his own homemade rocket almost 1,875 feet into the sky from a homemade launchpad near Amboy, California, on the floor of the Mojave Desert.¹² His intention was to get high enough to see if the earth really looked curved from space, but at the elevation he reached, it would have been impossible to tell—and he was only in the sky for less than a minute in a violently vibrating rocket with a tiny window, after which he made a hard landing and sustained severe injuries.

Hughes told the Associated Press, “I don’t believe in science. I know about aerodynamics and fluid dynamics and how things move through the air, about the certain size of rocket nozzles, and thrust, but that’s not science, that’s just a formula. There’s no difference between science and science fiction.”¹³ Of course, if he really wanted to see the curvature of the earth from a high altitude, there are lots of safer ways, which are discussed at the end of the chapter, that would not risk his life and health. On February 22, 2020, Hughes paid the ultimate price for denying reality when his rocket crashed and killed him.

Hearing all this, most people shake their heads and wonder what has happened to our society and education system that the weirdest of all ideas is actively being debated in mainstream media and that someone as famous as Neil deGrasse Tyson feels it is worth his time to debunk it. Hasn’t the reality of the round earth been established since the time of Columbus? As Tyson tweeted, “Duude—to be clear: Being five centuries regressed in your reasoning doesn’t mean we all can’t still like your music.”¹⁴

As astronomer and author Phil Plait wrote in 2008,

The world is filled with dumbosity, and it’s all we can do to fight it. But sometimes an idea is so ridiculous that you have to wonder if it’s a joke. Yeah, I mean the Flat Earthers. Can people in the 21st century really think the Earth is a flat disk, and not a sphere? When I see their claims I have to wonder if it’s an elaborate hoax, their attempt to poke a hornet’s nest just to see how reality-based people react. The media will sometimes talk to these goofballs, and I’m glad to report it’s almost always tongue-in-cheek, which is probably more than they deserve.¹⁵

Myths of Columbus

Actually, it’s a myth that most people in 1492 thought the earth was flat and that they scorned Columbus because he was convinced it was round. In fact, most educated people have known that the earth is round for at least 2,500 years. Ancient Greeks noticed that the earth cast a curved shadow on the moon during an eclipse. In his dialogue Timaeus, Plato wrote that the creator “made the world in the form of a globe, round as from a lathe, having its extremes in every direction equidistant from the centre, the most perfect and the most like itself of all figures.”¹⁶ Plato’s student Aristotle noticed that if he traveled north or south, it changed which stars he could see above him, and later astronomers discovered that if you traveled to the Southern Hemisphere, the constellations are entirely different.

About 200 BCE, the Hellenistic Greek scholar Eratosthenes famously estimated the circumference and diameter of the earth. He had heard stories that the sunlight shone vertically down into the bottom of a deep well only at high noon on the summer solstice in Syene, about two hundred kilometers south of Alexandria down the Nile River near the modern Aswan High Dam. By using a long rod to measure the length of its shadow and calculating the angle of the vertical rod with the sun overhead in Alexandria, he was able to measure the difference in the angles between Syene and Alexandria (fig. 2.1). Using simple geometry, he estimated the circumference of the earth to be about forty thousand kilometers. This is amazingly accurate, less than 0.16 percent off the value that we now accept.

Nor did the discoveries of the Greeks die with the “Dark Ages” and the loss of most of the writings of the ancient Greeks and Romans. Although some medieval scholars thought the earth was flat, most of them had read Plato and Aristotle and accepted their evidence that the earth was round. About 1250 CE, the medieval scholar John Sacrobosco wrote Treatise on a Sphere, with multiple proofs of the curvature of the earth. In it, he said,

That the earth, too, is round is shown thus. The signs and 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. Moreover, celestial phenomena evidence that they rise sooner for Orientals than for westerners. For one and the same eclipse of the moon which appears to us in the first hour of the night appears to Orientals about the third hour of the night, which proves that they had night and sunset before we did, of which setting the bulge of the earth is the cause.¹⁷

Figure 2.1. Diagram showing Eratosthenes’s famous experiment to calculate the size and curvature of the earth. He noticed that at summer solstice, the sun was directly overhead in Syene (which is on the Tropic of Cancer, where the sun’s rays come straight down on the first day of summer). Meanwhile, to the north where he lived in Alexandria, the sun made a 7° angle from a post sticking vertically above the ground. Eratosthenes used this angle and the known distance between Syene and Alexandria to calculate the size of the earth to within 1 percent of the values we know now. (Courtesy Wikimedia Commons.)

The myth that most educated people in the medieval times and up to 1492 believed in a flat earth is a relatively recent notion. As Jeffrey Burton Russell documented in his 1991 book, Inventing the Flat Earth: Columbus and Modern Historians, American author Washington Irving, famous for his stories of Rip van Winkle and the Headless Horseman of “The Legend of Sleepy Hollow,” created this fiction; he needed to spice up the conflict between the Church and Columbus in order to improve the drama for his 1828 book, A History of the Life and Voyages of Christopher Columbus. Irving was very widely read and cited, so his myth entered all the American history textbooks for the next century. Even as late as 1983, it was still widely believed, and the myth appeared in historian Daniel Boorstin’s best-selling book, The Discoverers.

Modern Flat-Earthism

In fact, flat-earth beliefs were a rare fringe idea with few followers until relatively recently. In the 1800s, the most famous flat-earther was Samuel Rowbotham (1816–1884). In the 1860s, he pioneered the modern flat-earther notion that the earth was a disk centered over the North Pole (fig. 2.2), bounded on its outer edge by a wall of ice (instead of Antarctica over the South Pole, which cannot exist in their version of geography). The skies above were a dome of fixed stars only five thousand kilometers above the earth’s surface, consistent with the old medieval notion of the heavens before the birth of modern astronomy. His ideas were first published in a pamphlet called Zetetic Astronomy, followed by a book called Earth Is Not a Globe, and another pamphlet, The Inconsistency of Modern Astronomy and Its Opposition to the Scriptures, which revealed the biblical literalist roots of most flat-earth thinking.

According to Rowbotham, the “Bible, alongside our senses, supported the idea that the earth was flat and immovable and this essential truth should not be set aside for a system based solely on human conjecture.”¹⁸ He is correct in saying this, because there are at least sixteen places where the Bible says the earth is flat; talks about the “four corners of the earth,” the “ends of the earth,” and the “circle of the earth”; or suggests that you can see the entire earth from a high place.¹⁹ Rowbotham and later followers like William Carpenter and Lady Elizabeth Blount kept promoting the idea and founded the Universal Zetetic Society after Rowbotham’s death in 1884. This incarnation of flat-earth thinking died out some time after 1904.

After about fifty years of virtually no organized activity, the rebirth of flat-earth thinking occurred in 1956 with the founding of Samuel Shenton’s International Flat Earth Research Society, based in his home in Dover, England. Always a tiny group, with a very limited membership, they corresponded through a homemade mailed newsletter, yet every once in a while, they managed to get a short burst of publicity in the newspapers. In the 1960s and 1970s, when Mercury, Gemini, and Apollo astronauts first began to produce images of the earth from space, Shenton dismissed the images as hoaxes (the common belief among flat-earthers ever since), saying, “It’s easy to see how a photograph like that could fool the untrained eye.”²⁰ Later, he attributed the curvature of the earth seen in NASA photographs to a trick of the curvature of wide-angle lenses: “It’s a deception of the public and it isn’t right.”²¹

Figure 2.2. Map of the earth from a north polar projection. (Courtesy NASA.)

After Shenton’s death in 1971, Charles K. Johnson picked up the mantle and inherited Shenton’s library from his wife. He reorganized the group as the International Flat Earth Research Society of America and Covenant People’s Church, where they maintained their lonely quest at his home in the town of Lancaster in the Mojave Desert.²² They claimed to have reached a membership as large as 3,500, scattered around the world, paying annual dues of six to ten dollars. The society communicated via the quarterly Flat Earth News, a four-page tabloid written and edited almost entirely by Johnson and sent in the mail. As hard-core biblical literalists, they emphasized all the passages that state that the earth is flat. Every few years, they would get smirking coverage in the newspapers, but their membership declined during the 1990s, especially after a fire at Johnson’s house in 1997 destroyed all records and membership contact information. Johnson’s wife died shortly afterward, and then the society itself vanished when Johnson died on March 19, 2001.

Flat-earth thinking might still be a tiny fringe belief with no organized leadership were it not for the internet and the ability of believers all around the earth to find each other and organize a virtual community. In 2004, the Flat Earth Society was resurrected by Daniel Shenton (no relation to Samuel) as a web-based discussion forum and then eventually relaunched as an official society, with a large web presence and their own wiki.²³ As of July 2017, they claimed a membership of five hundred people. However, the publicity from celebrity entertainers and musicians, such as those discussed at the beginning of this chapter, seems to suggest that flat-earth ideas are much more common (see chap. 18), even if the believers are not official members of the Flat Earth Society. There are a number of other flat-earth societies on the internet not affiliated to Shenton’s group. The first Flat Earth International Conference met in Raleigh, North Carolina, on November 9 and 10, 2017, with about five hundred attendees.²⁴ In May 2018, there was a three-day flat-earth convention in Birmingham, England, with several hundred attendees who traveled all the way to England to hear a spectrum of speakers with a common belief in the flat earth.²⁵ Even more alarming, about a third of millennials are not convinced that the earth is round (as discussed in chap. 18).²⁶ And there are calls on the internet for a reality show to let the flat-earthers test their ideas and actually try to travel off the edge of the earth!²⁷

In 2018, Netflix produced a documentary about the flat-earthers called Behind the Curve.²⁸ Like most such documentaries, it consists mostly of interviews of the major advocates of a particular idea (in this case, the flat earth) and contrasting views of other interviewees who regard the believers as crazy. It starts with one of the stars of the flat-earth movement, Mark Sargent, a middle-aged, balding man who still lives with his mother and depends on her to feed him. Sargent spouts one incredible claim after another, sitting in his mother’s basement obsessing over little details and posting hundreds of YouTube videos expounding his ideas. He claims as proof of the flat earth that he can see skyscrapers from his mother’s Whidbey Island backyard. However, Whidbey Island is less than forty-eight kilometers (about thirty miles) from downtown Seattle, too close to detect the curvature.

Sargent describes how he obsessed for three solid days trying to track aircraft online that flew near or across the South Pole and then decided there weren’t any such flights. According to Sargent, this proves that Antarctica is not a continent on the South Pole but a giant ice wall on the perimeter of the flat earth. (Later in the same part of the movie, a Caltech grad student pulls up a different flight tracking site and finds plenty of planes flying over parts of Antarctica.) He shows his handmade model of the flat earth with the dome of the sky and stars above it, and the moon and sun rotating in the sky above us, but he does not explain how this would create the phases of the moon or would explain eclipses, which are entirely impossible with his model.

When you argue with a flat-earther, a highly revealing moment is when they fall back on their cop-out “Oh, that’s just math and physics—I don’t believe in those.” In the documentary, Sargent says, “The reason why we’re winning against science is that science just throws math at us,” as if that were some mark of how smart he is and how he is beating science. This is behind much of their thinking: they are only capable of simple intuitive models and are typically math-phobic, so they refuse to do even the simplest calculations that would show why their ideas are impossible. By contrast, since the days of Isaac Newton, the reasons we know the earth is round are best understood by doing mathematical calculations that only make sense in a spherical globe and cannot be accommodated in a flat earth.

But the most revealing moment in the documentary is when the flat-earthers attempt to do experiments to prove their point. In both cases, the experiments actually show that the earth is round, and the flat-earthers refuse to accept the results:

One of the more jaw-dropping segments of the documentary comes when Bob Knodel, one of the hosts on a popular Flat Earth YouTube channel, walks viewers through an experiment involving a laser gyroscope. As the Earth rotates, the gyroscope appears to lean off-axis, staying in its original position as the Earth’s curvature changes in relation. “What we found is, is when we turned on that gyroscope we found that we were picking up a drift. A 15 degree per hour drift,” Knodel says, acknowledging that the gyroscope’s behavior confirmed to exactly what you’d expect from a gyroscope on a rotating globe. “Now, obviously we were taken aback by that. ‘Wow, that’s kind of a problem,’” Knodel says. “We obviously were not willing to accept that, and so we started looking for ways to disprove it was actually registering the motion of the Earth.” Despite further experimental refinements, Knodel’s gyroscope consistently behaves as if the Earth is round. Yet Knodel’s beliefs seem unchanged when discussing the experiment at a Flat Earth meetup in Denver. “We don’t want to blow this, you know? When you’ve got $20,000 in this freaking gyro. If we dumped what we found right now, it would be bad. It would be bad. What I just told you was confidential,” Knodel says to another Flat Earther in attendance.²⁹

The second experiment was run by Knodel’s cohost on his flat-earth YouTube channel, Jeran Campanella. This experiment provides the ending for the film. As described in Newsweek,

Campanella devises an experiment involving three posts of the same height and a high-powered laser. The idea is to set up three measuring posts over a nearly 4 mile length of equal elevation. Once the laser is activated at the first post, its height can be measured at the other two. If the laser is at eight feet on the first post, then five feet at the second, then it indicates the measuring posts are set upon the Earth’s curvature.

In his first attempt, Campanella’s laser light spread out too much over the distance, making an accurate measurement impossible. But at the very end of Behind the Curve, Campanella comes up with a similar experiment, this time involving a light instead of a laser. With two holes cut into styrofoam sheets at the same height, Campanella hopes to demonstrate that a light shone through the first hole will appear on a camera behind the second hole, indicating that a light, set at the same height as the holes, travelled straight across the surface of the Flat Earth. But if the light needs to be raised to a different height than the holes, it would indicate a curvature, invalidating the Flat Earth.

Campanella watches when the light is activated at the same height as the holes, but the light can’t be seen on the camera screen. “Lift up your light, way above your head,” Campanella says. With the compensation made for the curvature of the Earth, the light immediately appears on the camera. “Interesting,” Campanella says. “That’s interesting.” The documentary ends.³⁰

Even more revealing than the failure of their experiments and their reactions when they inadvertently demonstrate the curvature of the earth is the insight into the psychology of flat-earthers. Like many other conspiracy believers and cult followers, flat-eartherism is a fundamental belief system to them and a community, so flat-earthers cannot allow anything to change their minds. Otherwise, they will lose their sense of identity and group belonging as well as their feeling of understanding and controlling the world around them. As reported in Newsweek,

“Say you lose faith in this thing. What then happens to my personal relationships? And what’s the benefit for me doing that? Will the mainstream people welcome me back? No, they couldn’t care less. But, have I now lost all of my friends in this community? Yes. So, suddenly, you’re doubly isolated,” psychologist Dr. Per Espen Stoknes says in the documentary. “It becomes a question of identity. Who am I in this world? And I can define myself through this struggle.” “If I tried to go…” [flat-earther Mark] Sargent says in the documentary, contemplating the scenario described by Dr. Stoknes. “They would come and say, ‘Don’t, don’t do it.’ So I couldn’t, even if I wanted to.”³¹

How Do We Know?

One thing we have learned from this widespread skepticism of science and established reality is that we scientists and educators need to do a better job of conveying both the facts of science and the evidence of those facts to people. We need to describe and demonstrate the evidence why we know certain things to be true. As Neil deGrasse Tyson wrote, “The fact that there’s a rise of Flat-Earthers is evidence of two things. One, we live in a country that protects free speech. And two, we live in a country with a failed educational system…. Our system needs to train you not only what to know, but how to think about information and knowledge and evidence. If we don’t have that kind of training, you’d run around believing anything.”³²

So how do we know that the earth is roughly spherical in shape?³³ How could you tell for yourself without engaging in dangerous stunts like launching yourself in a homemade rocket? To answer these questions, we will not use observations from satellites, spacecraft, or aircraft, because flat-earthers believe that these are all hoaxes and part of a giant conspiracy.

1. Watch ships at sea: Even before the Greeks wrote about the spherical earth, ancient seafarers knew that if you watch a ship sail away to the horizon, the bottom hull of the ship vanishes first, followed by the mast and then the top of the ship (fig. 2.3). If it is sailing toward you, you see the masts first, followed by the hull as it gets closer. This only makes sense if the ship is sailing around the curve of the earth. Flat-earthers also have heard of this evidence, of course, and claim it is an illusion caused by the perspective on different objects. But this is not how perspective works. If an object is far away on a flat surface, it will get smaller, but the lower part will not vanish as it recedes; instead, all of it will get smaller but remain fully in view. This is true even if you go to a harbor and follow the ship using a telescope or binoculars to improve your distance vision. The ship will vanish from bottom to top, not just become smaller.

Figure 2.3. Medieval drawing of a ship at sea disappearing bottom first on the horizon of a curved earth. (Public domain.)

2. Look to the stars: As the ancients noticed, the constellations look different as you travel north and south in latitude on the earth. About 350 BCE, Aristotle was one of the first to record this observation. Traveling from Greece to Egypt, he could see the difference in the skies. As he noted, “There are stars seen in Egypt which are not seen in northern regions.” He realized that the earth was small enough that its curvature was apparent over that relatively short distance, “for otherwise the effect of so slight a change of place would not be quickly apparent.”³⁴ The difference became even more obvious when the first European explorers traveled south of the equator and found a whole new sky full of unfamiliar stars and constellations. The Southern Cross, for example, cannot be seen until you travel south of the Florida Keys, yet it becomes the major constellation of the sky when you are south of the equator. Meanwhile, the Big Dipper, which dominates the night sky above forty-one degrees north latitude, vanishes below the horizon as you head south, so at about twenty-five degrees south latitude in northern Australia, it is gone from the sky.

3. Watch a lunar eclipse: Every few years, we experience a lunar eclipse, where the disk of the full moon is covered by the shadow of the earth. It’s weird to watch the circle of the moon gradually get darker and darker as the edge of the earth’s shadow gradually covers it (fig. 2.4). As first discovered by the ancients and reported by Aristotle, the edge of earth’s shadow is unmistakably curved and becomes even more so as the eclipse approaches totality. Finally, the earth’s shadow covers the moon completely, so the only moonlight you see is from light that has passed around the curve of the earth and through our atmosphere (turning it red), refracting to the middle of the shadow.

Many times, the lunar eclipse is not total, but as the distance of the earth from the moon increases, it casts a slightly smaller shadow and the shining edges of the moon are visible on the edge of the shadow. This is called an annular eclipse, and it shows the entire shadow of the earth as a circle or ring of light around the dark shadow. This would never make sense if the earth were flat. Flat-earthers claim that the sunlight is blocked by the flat circular disk of the earth, but why then does the sun never happen to catch the flat disk of the earth on its edge or at an angle, so the shadow has a shape other than a circle? The only way this is possible is if eclipses happened only at midnight, when the “flat disk” is perpendicular to the sun-earth axis, so the “dark side” of the earth would only see the total eclipse of the moon when it was directly overhead at the stroke of midnight. In fact, lunar eclipses happen at all different times of day and night (although they are not very visible in the daytime).

Figure 2.4. A total lunar eclipse on June 15, 2011, as seen from Budapest, Hungary. The upper left frame shows totality, with the moon entirely covered by the earth’s shadow. Over the next hour, the earth’s shadow moves off to the lower right, and its distinctly curved edge can be seen, showing that the earth casts a curved shadow and therefore must be a spherical shape. By 23:10 Universal Time, the shadow has almost completely vanished and the full moon is visible. (Photo courtesy Wikimedia Commons.)

4. Go climb a mountain: If the earth were flat, you could see huge distances if you had a good enough telescope, so looking across the distance between Miami and New York City, only 1,000 miles or 1,760 kilometers, should be no problem. But if you are standing on level ground, even under the best of conditions with a superpowerful telescope, you can see no farther than about 3 miles (5 kilometers). Any object farther than that disappears below the horizon. Of course, if you climb a tree or even a mountain, you can see a bit farther on a day with excellent clear air and visibility. Standing on a hill 60 meters high, you can see about 50 kilometers. But even from the tallest mountains, no one can see much farther than about 60 miles or 100 kilometers, certainly not the distance from New York to Miami.

Take another example: Mauna Kea volcano on the Big Island of Hawaii is the highest peak in the Hawaiian Islands at 4,205 meters (13,796 feet). On a flat earth with nothing but ocean for many miles, you should be able to see enormous distances on a clear day. On the island of Kauai, only 487 kilometers (303 miles) away, is that island’s highest peak, Kawaikini, at 1,592 meters (5,226 feet). Over such a short distance on a flat earth, someone on Mauna Kea should easily be able to see the top of Kauai, but you can’t, because the earth is curved. Thanks to that curvature, the farthest you can see from Mauna Kea is 374 kilometers (233 miles).

5. Go fly in a plane: If you fly around the world, you are traveling around a sphere. You cannot do this on a disk-shaped earth. If you calculated the distances to travel in a circle around the North Pole on a disk-shaped earth (fig. 2.2), it would not add up to the distance you must actually travel around a spherical globe, no matter which latitude you traveled along. Even more convincing is the view from high above the earth. Unlike the people like “Mad” Mike Hughes who killed himself in his homemade rocket that rose only 1,875 feet, there are ways to get high enough to see the earth’s curvature. In a passenger jet flying above 35,000 feet, the curvature begins to be visible, although you need a wide window with a sixty-degree field of view to detect the curvature.

This isn’t possible to see with the tiny passenger windows, but the crew on the flight deck can see it fine, so anyone in the cockpit in flight can see it. (Sadly, after the 9/11 hijackings, the flight deck is always locked against intruders during flight.) Above fifty thousand feet, the curvature becomes more obvious, although few commercial aircraft fly that high. The now-retired supersonic Concorde jet routinely cruised at sixty thousand feet, so passengers on those flights could see the curvature of the earth easily. And of course, military aircraft and spacecraft and our thousands of satellites fly much higher and see it all the time, but as flat-earthers believe that everything from NASA and the military is part of great conspiracy to hoax us all, that won’t help convince them.

6. Fly near the South Pole: Flat-earthers claim that there is no South Pole or Antarctic continent over it, but just a 1,500-foot-tall ice wall around the edge of the earth’s disk guarded by NASA (fig. 2.2). According to the Flat Earth Society, no one has been past this ice wall and lived to tell the tale. Of course, this makes everyone who has ever traveled to Antarctica a hoaxer and liar, including pioneering polar explorers like Roald Amundsen (who reached the South Pole first), Ernest Shackleton, Sir Robert Scott, and others who made these expeditions before the flat-earth idea of the ice wall had been suggested. It also makes liars out of anyone else who may have traveled across the Antarctic Circle and returned successfully, or all the polar researchers down in Antarctica right now. (I have several friends down there finding fossils as I write this.)

Despite what flat-earthers claim, commercial flights do travel over part of the Antarctic,³⁵ and if you get the right window seat and good weather during these flights, you can see parts of Antarctica from your seat. Most commercial flights across the Southern Hemisphere don’t fly over the center of Antarctica because it is not on the shortest possible route (the great circle route, or the straightest line on a globe) between South America and Australia, or South Africa and Australia. But they do fly over the edge of the continent, so you could look down and see the Antarctic ice sheet from your window seat.³⁶ A flight between New Zealand and South Africa would cross Antarctica, but currently there are no flights scheduled to do this.³⁷ Anyway, a commercial flight over the ice cap is not a good idea, especially given the bad weather over Antarctica most of the year—and also because if they have plane trouble, it’s much better to make an emergency landing in the Southern Ocean where there is a chance of rescue rather than in the middle of the Antarctic ice cap. Flights that run south of seventy-two degrees south latitude must carry special survival gear in case they go down in the polar region. As this regulation reduces the number of paying passengers they carry,³⁸ not many flights are scheduled in the Antarctic Circle.

7. Send up a balloon: Another way to get your own images from high enough to see the earth’s curvature is to send up a weather balloon. Both balloons and the kinds of cameras and equipment needed to record and transmit the signals are easily available through commercial sources now, for anyone who has the technical skills and funds to try this. In January 2017, a group of students from the University of Leicester Department of Physics of Astronomy and members of the Leicester Astronomy and Rocketry Society did just such an experiment. Their weather balloon, launched from Tewksbury in Gloucestershire, rose 77,429 feet (23.6 kilometers) into the sky, and their cameras sent back stunning footage of the curved earth from the high atmosphere (fig. 2.5).³⁹ You are welcome to watch the footage online for yourself (just search for videos under “Project Aether”) and see it vividly demonstrating the view from higher and higher elevations. After reaching its maximum altitude (where the temperature was about–56° Celsius and the air pressure was nearly a vacuum), the payload then descended to earth at speeds of more than 100 miles per hour and was successfully recovered in Warwickshire. You can try it yourself if you have the money and the expertise! Just contact the Federal Aviation Administration before you launch to make sure that your balloon doesn’t fly into restricted airspace.

Figure 2.5. Image of earth from balloon. (Courtesy Wikimedia Commons.)

8. Compare shadows: If you are motivated, you can replicate Eratosthenes’s famous experiment (fig. 2.1) yourself. The simplest way to do it would be to take a long flight in a north-south direction. Before you take off, measure the length your shadow casts at a particular time of day at your starting point. Take the flight, and then at the same time on the following day, measure the shadow at your new location. It should be measurably longer or shorter if you have traveled far enough. If the earth were a flat disk and not a sphere, this would not happen, because the sunlight coming in at an angle on a flat disk would always cast the same length of shadow.

9. Compare time zones: As anyone with jet lag can tell you, traveling east to west, or west to east, around the earth for any significant distance is discombobulating, because changing time zones upsets your biological clock. This is a direct demonstration of how different parts of the spinning earth are facing the sun at different angles, so they are all experiencing a different time of the day relative to the sun. The easiest way to confirm this in this world of instantaneous satellite communication (which in itself is a confirmation of the spherical earth) is to compare the time you are experiencing in your area with the time of someone in a different part of the world. For example, if it’s noon in New York and you email or text or call a friend in Beijing, it’s midnight there, and it’s 1:30 a.m. in Adelaide, Australia. Or if you look up the times for sunrise and sunset at different longitudes around the earth, you see that they occur at different times. This is simply impossible with a flat earth. Flat- earthers have tried to get around this problem by claiming that the sun’s light casts a big circular flat “spotlight” that is pointing in a circle around the different parts of the earth, but that explanation falls apart if you think about it. If you were in a large darkened theater, you could still see the spotlight casting its light on the stage even though you might be in total darkness where you sit.

10. Compare seasons: If the earth were flat, the sun’s rays would hit all parts of the earth from straight above and would not come in at an angle, like they actually do. In addition, there would be no seasons, because on a flat earth, both the Northern and Southern Hemispheres would get the same amount of solar radiation all year round. We would all experience whatever seasons there were the same way. But thanks to the spherical shape of the earth and its tilted axis, we experience seasons at different times, so winter in the Northern Hemisphere is summer in the Southern Hemisphere, and vice versa.

11. Feel the pull of gravity: If you accept the laws of gravity worked out by Isaac Newton, then the force of attraction of gravity should get stronger the closer you are to the center of mass. In a flat-earth disk (fig. 2.2), gravity should be strongest in the center of the disk at the North Pole and much weaker as you approach the Antarctic, on the edge of the disk. If you dropped an apple in Australia or southern Patagonia, it should fall somewhat sideways, pulled toward the North Pole, not straight down—but it doesn’t. Anyone with a decent gravimeter (a device that measures gravitational attraction) can measure the gravity anywhere on earth, and the attraction at sea level is nearly always the same (except for local effects like crustal rock beneath you, which is denser or less dense than average). The scientific data for these gravity measurements have been gathered for more than a century and are widely published, although flat-earthers reject all scientists as part of the global conspiracy that includes NASA. (Of course, many flat-earthers don’t believe in gravity, either, but fall back on Aristotle’s antiquated notions that objects fall because they are heavier or lighter.)

12. Consider the solar system: Anyone with a decent telescope, good night visibility, and a chance to look at the moon or the other planets night after night can confirm what early astronomers (especially Galileo) could see: all the other bodies in the solar system are spherical. You can see the shape of the moon clearly, especially as the shape of the illuminated part of the moon changes with the cycle of the full and new moons every month. After several nights of closely observing Jupiter in a good telescope, you can confirm that it is round and spinning on its axis; even better, each night you can see its four largest moons moving around as they orbit around it. It’s a lot more difficult to do this with Mars or Saturn, but Galileo was able to see it when he first trained a telescope to the skies. So if all the other bodies in space are spherical, why would only the earth be flat?

If that’s not convincing enough to fair-minded flat-earthers or to people sitting on the fence on the issue or having doubts about the shape of the earth, then they are hopelessly lost in the mind-set of a cultist, and no amount of evidence will convince them. Sometimes they accidentally reveal the disconnect between their worldview and reality, as when a tweet from the Flat Earth Society read, “The Flat Earth Society has members around the globe.” Then there is the humorous internet meme “The only thing flat-earthers have to fear is sphere itself.” So we will consider this case closed and will move on to the next weird idea about earth: geocentrism.