That Earth is round was well known long before Columbus

Image above by Kevin from The Beginning at Last

Super fact 28: That Earth is round, or spherical (or closely spherical) had been known for at least a couple of thousand years by the time Columbus set sail. Columbus did not set sail to prove that earth was round, and he knew it was round.

How I imagine one of Columbus’ ships. This is a submission for Kevin’s No Theme Thursday

The ancient Greeks, particularly philosophers like Pythagoras and Aristotle knew that earth was round from observing how ships disappeared over the horizon hull first, while their masts were still visible. They noticed the earth’s round shadow cast on the moon during lunar eclipses.

If earth was flat, earth’s shadow would not appear round, especially not all the time. They also noticed that different constellations were visible depending on the location (on earth). So, noticing that earth was round was a simple and obvious observation that easily could be made thousands of years ago.

Earth is a sphere, or closely spherical. Photo by Pixabay on Pexels.com.

According to historian Jeffrey Burton Russell, “no educated person in the history of Western Civilization from the third century B.C. onward believed that the Earth was flat.” In 240 BC (2,260 years ago) the Greek mathematician and philosopher Eratosthenes calculated the radius and circumference of earth within an error of 2%.  So why did Columbus want to sail west?

Columbus thought that the earth’s circumference was smaller than what Eratosthenes calculation had shown because he relied on maps created by Ptolemy instead of the calculations made by Eratosthenes. When he landed in the New World it seemed like Columbus had been vindicated but that did not last long. Essentially, Columbus sailed west and discovered America because he miscalculated the earth’s circumference.

Columbus thought earth was smaller. He did not know about the Pacific Ocean. Earth Pacific Ocean view Stock Illustration ID: 1617553012 by Matis75

It should be noted that even though the earth is very close to being a sphere, it is more correctly an ellipsoid because it is slightly bulging at the equator due to centrifugal forces. You sometimes hear people say that Copernicus or Galileo proposed that earth was round. This is of course false.

Copernicus’s theory of the solar system, the heliocentric model, proposed that the Sun is at the center of the solar system and the Earth, along with other planets, revolve around it. This was not a well-known fact at the time, unlike the fact that the earth is round. Galileo defended Copernicus theory. The famous alleged quote “And yet it moves” / “E pur si muove” is said to have originated from his argument with the church (however, this is not certain).

So, we know that people knew that earth was round thousands of years before Columbus, and thousands of years before the renaissance, and we know that Columbus did not sail west to prove that earth was round, and he certainly did not prove it. Yet I’ve heard this claim quite often, which is why I consider that earth being round being well known long before Columbus a super fact. Too few people believe earth to be flat like a pancake for me to consider earth being round a super fact.

Eratosthenes Calculates the Circumference of Earth

Around 500 BC (2,500 years ago) most Greeks believed that the Earth was round, but they did not know how big it was. The Greek philosopher and mathematician Eratosthenes devised a clever method of estimating its circumference and he got very close. He had heard from travelers about a well in Syene (now Aswan) that at noon on the summer solstice, about June 21 every year, the sun illuminated the entire bottom of a well, without casting any shadows, indicating that the sun was directly overhead. He had also heard that perfectly vertical poles had no shadows at this time.

The reason for this was that Syene/Aswan is located very close to the tropic of Cancer (23.5 degrees versus 24 degrees, or about 60 miles).

In Alexandria, north of Syene, the sun was not directly overhead on the summer solstice. Eratosthenes measured the angle of a shadow cast by a stick at noon on the summer solstice in Alexandria and found it to be 7.2 degrees. Using the distance from Alexandria to Syene and this angle Eratosthenes calculated earth’s circumference to be between 40,250 to 45,900 kilometers. Earth’s circumference is 40,075 kilometers.

Illustration of the measurement of the Earth circumference by Eratosthenes. On June 21st there is no shadow in Syene/Aswan but there is one in Alexandria. Asset id: 2319651251 by Javier Jaime

Resurgence in Flat Earth Beliefs

While very few people believed the Earth was flat 50 years ago, there has been a recent rise in Flat Earth conspiracy theories, largely fueled by online misinformation. Now a day 2% of Americans aged 18-24 years old firmly believe it is flat. That is despite the fact that it is easy to directly observe earth’s round shape. That is a small minority but why would anyone believe such a thing today.

For example, on a flat Earth, a Sun that shines in all directions would illuminate the entire surface at the same time, and all places would experience sunrise and sunset at the horizon at about the same time. With a spherical Earth, half the planet is in daylight at any given time and the other half experiences nighttime. Well just give someone overseas a phone call and you’ll see what the case is. In addition, different places have different amounts of daylight at the same time, which wouldn’t happen with a flat earth.

You can observe the round shape from an airplane. If you stand on a hill by the coast, you can see ships disappearing over the horizon hull first, and you can see earth’s round shadow cast on the moon during lunar eclipses. If you travel far, you can see the constellations and the stars being in different positions in the sky. The southern and northern hemisphere have completely different constellations.

Never mind Eratosthenes, gravity, the Coriolis force, other celestial bodies being round, eyewitness accounts by astronauts, ring-laser gyroscopes, and Foucault pendulums. The moon shows the same face to everyone on earth, which would not be possible if earth was flat. Also never mind NASA photos and the fact that no one has found the earth’s edge.

Below is a youTube video showing an animation composed of actual satellite photos by NASA. Earth is obviously round in this video.

In this video the near side of the moon is dark and what you see is the far side. The far side looks a little bit different from the near side of the moon. It is a new moon and the people on earth don’t see the moon. The sun is behind us and lights up both earth and the far side of the moon (this side people on earth do not see). Also, since there is daylight, the camera does not capture faint objects such as stars.

To see the other Super Facts click here

Author: thomasstigwikman

My name is Thomas Wikman. I am a software/robotics engineer with a background in physics. I am currently retired. I took early retirement. I am a dog lover, and especially a Leonberger lover, a home brewer, craft beer enthusiast, I’m learning French, and I am an avid reader. I live in Dallas, Texas, but I am originally from Sweden. I am married to Claudia, and we have three children. I have two blogs. The first feature the crazy adventures of our Leonberger Le Bronco von der Löwenhöhle as well as information on Leonbergers. The second blog, superfactful, feature information and facts I think are very interesting. With this blog I would like to create a list of facts that are accepted as true among the experts of the field and yet disputed amongst the public or highly surprising. These facts are special and in lieu of a better word I call them super-facts.

36 thoughts on “That Earth is round was well known long before Columbus”

  1. It is amazing to me that all these years later, schools and texts still teach the belief that Columbus proved the Earth was round, when clearly, others far before knew different. 😄

    Another fantastic article, Thomas. I truly enjoy learning all these facts!

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    1. Thank you for your kind words Kevin. Whilst others not only knew it was round, they also knew roughly how big it was, but Columbus got the circumference wrong. He might now have set sail if he had known that it was much bigger than he thought.

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  2. I remember being taught in school that educated people at the time of Columbus knew the earth was round. Granted, that was a while ago. It was only in Bugs Bunny cartoons that he set sail to prove the earth was round. He set sail to find a shorter route to India and trade. He didn’t expect a couple of continents to get in the way. But, of course, this is how people lived before the internet. And there were card catalogues in the libraries, too.

    Sorry. In a silly mood this morning.

    In all seriousness, you posted an interesting view of perspective and mythmaking.

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    1. Thank you so much Denise. Yes I posted this because I still encounter people who think that Columbus proved that earth is round or that it was discovered that earth was round during the renaissance. It is a common misconception but it is great that learned the correct story at your school.

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  3. That was fascinating. I can answer your question–why flat earthers persist. These are people who deny science, don’t believe they’re hearing the truth from scientists. I get that (disagree of course), but if they don’t bother me (like become science teachers in my kid’s school), I will move on to bigger worries!

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  4. This was an awesome piece as usual, Thomas! I never can understand the flat earth theory, that’s just wild to me for pretty much anyone who has ever taken a trip pretty much anywhere lol 😆 but still, so much continues to be misconstrued in a very odd way. You really do research and bring out all the facts! 🌍 great job 👏 👏

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    1. Thank you so much for your kind words Laura. Some of them don’t believe Australia exist and that people from Australia are just actors. If you are going to be unreasonable, why not go all the way. But I find it interesting that so many people mistakenly believe that earth being round was something that was discovered during he renaissance by people like Columbus, when in reality that is several thousands of years old knowledge.

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  5. Wowza, those ancient Greeks and their brilliant deductions: round shadows and disappearing vessels. Highlighting Eratosthenes’ remarkably accurate calculation of Earth’s circumference around 240 BC further underscores the advanced understanding of our planet’s form long before Columbus’s voyages. For me one of the major “ohhh” moments was that Columbus’s journey was actually driven by a miscalculation.

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    1. I agree the ancient Greeks did a lot of amazing things. Yes people did not want to sail to India by going west, not because they thought earth wasn’t round, but because it was too far, which it was. Then Columbus came along with his wrong calculations and then he thought he bumped into India when it was America. That’s the story we don’t hear often.

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    1. I think it is pretty common to hear people say that Columbus wanted to prove earth to be round or that the fact that earth is round was discovered during the renaissance, but that was already well-known thousands of years before. That’s why I chose it as a super fact. That earth is round is not my super fact because it is not a common belief. I hope it stays that way, but unfortunately social media and the internet have caused a resurgence in flat earth belief. It is still small, but it is funny how a device with a ton of information can cause the spread of so much misinformation and some people buy it.

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    1. Thank you so much for your kind words Debby. You are right. The conspiracy theories and anti-science on social media are making us dumber. It’s ironic how all this information at our fingertips is not making us smarter but dumber.

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  10. It’s amazing to me that 2% of Americans firmly believe the earth is flat (though I’m not surprised). I think they should get on a ship and try sail to the edge, Thomas. If we can’t agree on such obvious facts of science, how will we ever tackle the difficult questions that we face. And clearly Columbus should have listened to Eratosthenes, who clearly had this superfact correct. 🙂

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    1. Thank you so much Diane. About the edge, Ha ha that is a good idea. Why don’t they find the edge. They can also try to explain why it is day in Hawaii and night in Florida. It is amazing that the reason Columbus sailed west was because he had the wrong numbers for the circumference.

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  11. I believe the belief that the bible is infallible contributes greatly to this farse of a flat earth. There are people only too willing to try to convince us the earth is less than 6000 years old too. Such a shame that fact fall by the wayside when religion oversteps it’s bounds.

    What an excellent and thought provoking article.

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  12. I saved the article you linked. Thank you. Most of it is beyond my pay grade but the very fact that I can admit that I don’t understand the science but I believe in it’s factuality makes people who are just willing to accept the creationists dogma at face value even more devastating. Keep up the good work.

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    1. Thank you so much Violet. We cannot know about everything. We have to choose what we want to know about. However, I think it is great that you chose to trust scientific consensus over religious (or political) dogma. With that article I wanted to point out how strong/compelling the evidence for old universe/world is. It is something we know, not something we are guessing. Scientists are not jumping to conclusions. Scientists rarely agree unless the evidence is so strong that it’s the only reasonable thing to do.

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