Welcome back to Glass Half Full, and thanks for reading! Today, we’re continuing the discussion of how to talk to a flat-earther as background to my satirical novel, Ship of Fools. If you find this post valuable, please:
Last week I promised a post on different ways to prove the Earth is round, should you ever find yourself in a serious debate with a flat-earther. But as I wrote in that post, evidence of this sort is unlikely to be effective unless you already have a solid relationship with the flat-earther in question and they seem open to listening.
In this post, I’m going to give you some points to avoid and some points you can make, but first, I’m going to make a shocking claim:
The Earth is both flat and round
Wait, Larry, how can that be? The answer: It all depends on scale. Here’s an example: Do the horizontal (well, slightly tilted) elements in this image look straight or curved?
They’re straight lines, right? Now how about when we zoom out a bit?
And all the way out:
(Thanks to YouTuber SciManDan for these screen grabs.)
We’re all walking around on one of those flat segments (which I believe correspond to arcs of one degree). Sure, on the actual Earth there’s curvature within each 100-km segment, but it’s too subtle for us to sense it. We can detect the effects of curvature, as Dan points out in the video linked above, but that’s different from being able to detect the curve directly. For all intents and purposes, in our everyday lives, we live on a flat surface. But that’s in the context of living on a globe.
I hope this will give you a bit of compassion for any flat-earthers you know. Here’s what we all experience in everyday life, which can easily lead to false conclusions if we don’t know anything else:
Wherever we have a view to the horizon, the landscape (or seascape) appears flat
It feels as if Earth is stationary — we don’t feel as if we live on a spinning ball hurtling through space
Everything in the sky — the sun, the moon, the stars — appears to be in motion, traveling around the Earth
Add to this a distrust for authority, especially of the scientific kind, and is it any wonder people fall for flat-earth messaging? So try to have patience with the flat-earthers in your life, and tread carefully if you do try to persuade them to come back to the globe side.
Points to avoid
First off, don’t call the Earth round! It’s an oblate spheroid, slightly wider at the center. Flat-earthers know this, so if you call it round, they’ll say you don’t know your own model. But if you call it an oblate spheroid or slightly pear-shaped, they’ll say, “You globers can’t make up your minds! First it was round, now it’s not.” Just one example of how you can’t win in a debate with a flat-earther.
Second, don’t simply claim that the Magellan-Elanco Expedition proved the Earth is a globe, as this article does1. It’s actually a bit more complex than that. The flat-earthers will tell you this voyage traveled around the disk in a lopsided circle. There are many problems with that statement, but can you think of what they are?2
![A top-down map of the Earth with the Magellan-Elanco route drawn in red. A top-down map of the Earth with the Magellan-Elanco route drawn in red.](https://substackcdn.com/image/fetch/w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F3eae1157-c89a-4dcd-8016-89c362795d4f_482x482.jpeg)
Third, don’t claim you can see the curve of the Earth by looking out at the ocean from a beach or a cliff. You can’t! If you think you’re seeing curvature, it’s because the sweep of the horizon makes a circle with you at the center. Don’t claim you can see the curve from an airplane either, which the flat-earthers have successfully debunked over and over. You need to fly about twice as high as your average passenger jet to see any curve.
Proofs
There are many, many proofs that the Earth is a globe. These are just some of them, ranked from least-convincing (to a flat-earther) to the most convincing. I’ll go into detail on the last two, but if you’d like to talk about any of the others, please leave a comment.
Pictures from space
Ships disappearing hull-first over the horizon
Sunrise and sunset
Eratosthenes’ stick and shadow experiment
The Magellan expedition’s circumnavigation of the Earth
Modified Eratosthenes “three stick” experiment
Different set of stars in the southern hemisphere
Seasons
Single face of the moon seen from Earth
Shape of the Earth’s shadow during lunar eclipse
The Coriolis Effect
The existence of Antarctica (rather than an ice wall at the edge of the disk)
The opposite apparent rotation of stars in northern vs. southern hemisphere
Twenty-four hours of daylight in austral summer
Let’s look at the last two, since flat-earthers have no rebuttals to them, other than “Australia doesn’t exist!” (I wonder what the Australian flat-earthers think of that claim?)
In the northern hemisphere, the stars appear to rotate counterclockwise around the northern celestial pole, which is closely aligned with Polaris, the North Star.
But in the southern hemisphere, the stars rotate in the opposite direction around the southern celestial pole.
This makes sense on a globe, but there’s simply no way to explain it if the Earth were flat.3 This is an easy observation that anyone can make by traveling from one hemisphere to the other. If time and money are an obstacle, flat-earthers in one hemisphere could compare notes with flat-earthers in the other. A flat-earth YouTuber could crowd-fund their audience to finance the trip. (Or maybe just watch these videos and trust that they’re not some gigantic plot!)
But the best globe-earth proof, in the sense that flat-earthers might accept it, is the fact that the sun never sets at the South Pole in the austral summer. Like the apparent rotation of the stars, there is no explanation for this on a flat Earth. Many flat-earthers have stated that experiencing this phenomenon would convince them to give up their false belief. But so far, none of them have travelled to Antarctica to find out, despite several offers of funding and chartered planes.
Now a new effort, Will Duffy’s The Final Experiment, plans to take both globe-earthers and flat-earthers to Antarctica in December of this year.
Seven prominent flat-earth debunkers have taken up the challenge, while two flat-earthers have accepted. (Duffy is only paying for two, or possibly three, participants to take the trip.) It will be fascinating to see if this trip actually happens, whether flat-earthers will attend, and whether they will be persuaded.
This is where one of my fictional flat-earthers in Ship of Fools differs from his real-life counterparts: Sarge Marshall is willing to sail to the South Pole in the belief that he’ll instead find an Ice Wall at the edge of the Earth. Like the one real-life flat-earther who tried to get his followers to fund such a trip, he gets considerable flack for it. To avoid spoilers, I won’t say more.
Debunking flat-earth claims
Positive arguments for the spheroidal shape of the Earth are important. But you’ll need one more set of tools in your box of arguments: rebuttals to flat-earth claims. These ideas include:
Gravity doesn’t exist (or isn’t what we think it is)
The moon produces its own light that cools the Earth rather than heats it
Earth is covered with a dome (the Dome of the Firmament)
The sun is only around 3,500 miles above the Earth
The list goes on and on! Rather than rebut them all, next week’s post will feature a roundup of my favorite flat-earth debunkers, most of them on YouTube. They deserve credit for converting at least one flat-earther and partial credit for stemming the spread of this foolish idea.
Thanks so much for reading! If you enjoyed this post, I hope you’ll give it a like or a share, or even subscribe or buy me a coffee.
What do you think? What points would you make if you found yourself in a debate with a flat-earther? Leave a note in the comments!
Come back on Friday for the next chapter of Ship of Fools: “A Flat-Earth Interlude.” You’ll find out what life might be like if Earth was actually flat. (Hint: in that world, the cranks and skeptics are called “Roundheads.”)
This article is a great example of why you shouldn’t start with the premise that debunking flat-earth beliefs will be easy. Flat-earthers have reasonable-sounding rebuttals to four out of its five proofs. (They all fall apart if you inspect them closely.)
The best rebuttal here is that the Magellan voyage would have been much longer on a flat Earth than on a globe. On the actual Earth, the circumference of each parallel gets shorter as you move south of the Equator; on the flat-earth map, the circumferences increase in length. If the planet matched the flat-earth map, then Magellan might never have made it across the Pacific with the extra distance he would have had to cover. Since Magellan planned for a trip around a globe and the plan worked, this is solid evidence that we do live on a globe.
Unless you think space is a complicated Rube Goldberg machine with rotating double-sided disks and mirrors, as in the video embedded here.