② Beyond the Edge of the World▪On worldviews in Columbus’ time

Columbus discovers America. But more importantly, he discovers discovery itself.

Wootton, David

The Invention of Science Book

2016, ISBN: 978-0141040837.

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Britannica, Encyclopædia

Art From The Encyclopædia Britannica (1768–71) Online


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Clavius, Christoph

In sphaeram ioannis de Sacro Bosco commentarius Online


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In 1492, Columbus sailed west to prove that the world was round. His sailors, terrified of falling off the edge of the world, were on the brink of mutiny just as America’s coastline came into view.

Except they weren’t. Ever since antiquity, nobody who had given it a moment’s thought actually believed the world was flat. Especially sailors, who could see the world’s curvature on the horizon with their own eyes.

This myth of medieval people believing the world to be flat was constructed after the fact. It was a story of ignorance that neatly fitted with the newly defined ‘Dark Ages’. It showed just how far men had come, and how truly the Renaissance man was head and shoulders above his ancestors.

Or is there more to the story than that? The discovery of America may not have proven to anyone that the earth was round, but it did completely uproot everyone’s concept of what the world looked like.

Hello and welcome to A History of Science. Episode 2: Beyond the Edge of the World.


In 600 BC, Pythagoras was the first of the ancients to call the world round. In the centuries that followed, revered Greek writers including Plato and Aristotle all paid lip service to the idea, until in the second century AD the Alexandrian writer Ptolemy settled the issue once and for all. In his Almagest, he summarized all arguments made over the centuries for a spherical earth. The book would remain the standard on astronomy for the next 1400 years, and ensured that the spherical earth was known throughout medieval Europe.

Among the proofs that Ptolemy gave were theoretical and practical ones. To his more learned readers, he argued that every part of the earth’s surface tended towards the center, and so logically formed a perfectly round globe. Yet he also described how mountains seem to rise out of the sea to sailors on an approaching ship, indicating that they must have been hidden by the curved surface of the sea. And it were imaginative explanations like these that ensured that no fifteenth century sailor was afraid of falling of the edge of the world.

So Columbus’ voyage did not convince his supposedly backwards contemporaries of the sphericity of the earth. His discovery of the American continent, however, did completely change the perspective medieval people had of the earth. Not from a flat disc to a round globe, but from perfectly shaped spheres of land and water to a seemingly random pattern of continents. In this episode, we will explore how Columbus’ discovery changed that perspective, and how it planted into the minds of fifteenth century people the seed of discovery.

The Ptolemaic System and Planetary Orbits

What did the world look like to Columbus and his contemporaries? It was as round to them as it is to us, but apart from that?

Well, for starters, it was the center of the universe. Ptolemy summarized earlier philosophers’ arguments for the earth being the universe’s center in his Almagest. This idea fitted neatly with the Christian idea of man and his habitat being the core of God’s Creation, and went down like butter in medieval Europe.

The ancients envisioned the universe as a geometrically based system, built up from perfect circles, triangles, and other forms. They reasoned that for any movement to continue indefinitely, such as the planets’ orbits, only perfect mathematical shapes would suffice. Any other shape would be inefficient causing the planets to lose their speed and eventually crawl to a halt.

A map of the Ptolemaic system, then, closely resembles a clockwork. The earth forms an orb in the center, with all other planets moving around it in perfect circles. Now, in reality the planets move in egg-like ellipses, not in perfect circles. And earth rotates in an ellipse of its own, of course. And, just for the record, all planets rotate around the sun, not the earth. So obviously, this geocentric perfect-circle model did not fit at all with observations of the planets’ movements. Seen from the earth, planets seem to randomly change their speed, distance, and brightness in relation to our planet. As instruments became more accurate, mapping these random orbits to the Ptolemaic system became increasingly difficult.

The ancient Greeks did try, though. To account for the apparent anomalies in their model, they conceptualized circles-within-circles. Planets moved around the earth in orbits resembling an old phone cord; constantly looping and looping again. By adding enough loops to planets’ orbits, they could make the model fit the measurements. And while the system remained the standard for more than a millennium, it was cracking in its joints with every new measurement.

The Ptolemaic System and Worldly Spheres

Now before we get back to Columbus, let’s take a closer look at what the world itself looked like in the Ptolemaic System. To begin answering that question, we first have to determine what his contemporaries believed the world was made of. And that, unsurprisingly, brings us back to the same four classical elements we introduced in the previous episode. The ancient Greeks believed not just that human bodies were made of earth, water, air, and fire, but everything else as well. Earth and water makes clay. Air and fire creates smoke. All other things out there – plants, rocks, stone, animals, metal – existed of similar combinations of these four elements – just in more complex variants.

If you look at the world from this pre-modern point of view, these four elements are abundant; we live on earth, breathe air, are surrounded by oceans, and see fire bursting through the skies during thunderstorms. Although medieval scholars were not sure about the exact proportions in which the classical elements related to each other, they were definitely sure that the world was made up out of them.

Ptolemy did not limit his model of perfect circles to planetary orbits. The world existed of perfect circles as well; four of them, to be precise, each one containing one of the four classical elements. Ptolemy called these circular bodies spheres, and described their relations in detail.

As the ‘heaviest’ of the classical elements, the sphere of earth was located at the center of the universe. Immediately surrounding it was the sphere of water, forming the world’s oceans and rivers. Above both of those was the sphere of air, which formed the sky. Above that, and mostly out of sight, was the sphere of fire, which was only briefly visible through bursts of lightning.

Now, I can imagine you having difficulty visualizing these admittedly nonsensical maps. If you do, take a look at the website, where I have collected some of these maps for reference: ahistoryof.science. In the meantime, try and visualize this idea of the world as a Russian Matryoshka doll. The outer doll forms the sphere of fire, the smaller one inside forms the sphere of air, the one after that water, and the smallest and final doll represents the sphere of earth.

Columbus and Circumnavigation

So what does this have to do with Columbus’ voyage? Well, let’s think this model through, shall we? If we are living on the innermost sphere of earth, why are we not surrounded by water? The smaller orb of earth should be completely engulfed by oceans from the adjacent sphere of water, right? But, obviously – as we are not all swimming – this is not the case. So what’s happening here?

There were conflicting theories on this matter. The most prominent of them envisioned the sphere of earth as an apple floating in a bucket of water. Being light, the apple floats to the surface, with roughly half of it being exposed to the air. This made perfect sense to fifteenth century Europeans; we lived on an enormous island surrounded on all sides by one giant ocean.

Now, Columbus did not set out to prove the world was round. What he did want to show, however, was that there was a Western sea route to the Indies. Since before the birth of Christ, Europeans had traded with the Far East through the Silk Road. The Silk Road was an extensive network of trading communities connecting Europe, the Middle East, India, and China to each other. Traveling this road, while lucrative, was dangerous. The way was long, hazardous, and – most important of all – expensive because of the many middlemen skimming off profits. There must be a better way to get to that silk, over water; if Asia was on the other edge of the apple, you could simply sail all the way around the globe until you hit land. And that is what Columbus intended to do.

He had a hard time finding fundraisers for his expedition. And who can blame them? His potential patrons weren’t afraid of him falling off the earth with their precious ships, but they were convinced nobody could circumnavigate the earth and live. There could be no land between Europe and Asia; no place to reprovision, get freshwater, or perform repairs. It was suicide.

Famously, of course, Ferdinand and Isabella of Spain took a gamble and funded Columbus’ expedition. And when, on that fateful day in October 1492, Columbus hit land, he was convinced he had circumnavigated the globe. He must have landed on the Eastern coast of India, and so called the inhabitants Indians. He wasn’t unimaginative to not consider having landed on another continent altogether, he simply couldn’t fathom the idea of other continents existing. Columbus died in 1506, having never realized the land mass he had famously set foot on was not connected to Asia at all.

The New World in the Ptolemaic System

When scholars landed on this unknown land, however, they quickly came to realize that it could not possibly be where it was supposed to be. The observations of the stars on this new land were completely different from what they were used to from Silk Road expeditions. This was not Asia. so, where were they, then?

In 1503 Amerigo Vespucci, an explorer who had sailed West in the wake of Columbus’ discovery, was the first person bold enough to call the shots. In a letter pregnantly titled Mundus Novus, he claimed the newly discovered land mass was nothing less than a new continent. From then on, the land was commonly referred to as the New World, until it would get its official title from Vespucci’s first name, Amerigo.

Vespucci claimed that the New World was located roughly halfway around the globe from the known land. To fit this fact into the already bursting Ptolemaic System, an increasingly creative theory had to be thought up.

Scholars at the time argued that this New World was an antipode to the known sphere of earth, in other words that it lay exactly opposite to it on the globe. This possibility had been discussed once before by the ancients, but had never received much attention. Now that this new continent had to be shoehorned into the Ptolemaic system, a theory with some ancient credibility suddenly looked appealing.

In order to make a continent on the other side of the globe possible, they imagined the sphere of earth as an ellipse instead of a circle. If it was long and thin enough, it was theoretically possible to pop out of the water on both sides of the globe. Variations on this theory required the sphere of water to be egg-shaped as well to allow for more of the earth to be above the water’s surface.

This theory only held if the New World lay exactly opposite the known earth. And as more measurements were done, it turned out that it did not. It lay roughly a quarter West from the Eurasian continent. Fanciful theories were proposed to make this fact fit the model; one of them envisioned two spheres of earth instead of one. But to no avail. It was too late. The New World could not be explained by the Ptolemaic system.

Cartographers were the first to come to terms with this new reality. In 1517 the first sophisticated map of the world existing of three spheres instead of four was published. The spheres of earth and water were collapsed into a single one. Notably, the word terra, which had previously been used to denote the sphere of earth, was increasingly being used to reference the combined sphere of earth and water. This represents a major step towards our modern concept of the world as a single globe, instead of a combination of overlapping orbs.

From there it went quickly. Theories on how this natural phenomenon had to be explained ran wild. The Viennan scholar Vadianus suggested that inhabitable earth was scattered randomly across the globe, floating on one giant ocean. Another hypothesis was put forward that claimed God had opened up the sphere of earth through caves and rivers, and had allowed the water to fill these cavities, essentially becoming one sphere. Whatever the case, though, the four spheres were forgotten as if they had never existed.


Itn 1492 everybody believed the spheres of earth and water to be separate. In 1550 every scholar believed they were one. This sudden change in belief was absolutely unprecedented.

It is difficult for us to imagine how great the implications of this seemingly rational shift in opinion were. Medieval science relied much more upon authority than it did on evidence, experiment, or observation. The wisdom of the ancient Greek philosophers was never called into question. Measurements that conflicted with their teachings were whisked away as having been performed carelessly. If that didn’t satisfy more persistent minds, scholars claimed nature had simply changed since the time of Aristotle.

The discovery of the New World, however, was too big to ignore. The facts were too abundant, and too decisive. Within the span of half a century, and after 1400 years of prominence, the four spheres were discarded. It was the first occurrence ever in which ancient philosophy was accepted to be wrong. The first time that facts dictated science.

Not just the immediate implications were great. In short order, other aspects of the Ptolemaic system were put to the test. The most famous of these is Copernicus’ theory on how the earth revolves around the sun, instead of the other way around. Even though this would not be widely accepted until Galileo provided evidence for it, the spark had been lit. Copernicus could have never made this claim sixty years earlier, in a time when Ptolemy still had unquestioned authority. Now, it was a viable point of view.

The discovery of the American continent was a catalyst for change in virtually all fields of science, not just astronomy. All of a sudden there were lots of different kinds of plants, animals, minerals, even people, that somehow had to fit in the existing systems of thought. How did ‘Indians’ get to the New World if there was no land bridge connecting Asia and America? Were they somehow not descendants of Adam and Eve? Or what about the giant Dinosaur bones that lay scattered all over the new continent. Had these animals gone extinct? Did that imply that Creation wasn’t perfect? Was God still tinkering with a finished product?

This seemingly endless amount of unknown flora and fauna that came from the New World uprooted every notion held since antiquity. How could theories on life not be contested if the ancient Greeks could never have taken into account completely unknown species? In order to make sense of all these facts, observations, and measurements, a more systematic method of inquiry was needed. Over the centuries, these systematic routines of experimental testing and logical deduction would come to form what is perhaps the greatest discovery of all, the scientific method.


In 1492, Columbus discovered America. But more importantly, he discovered discovery itself.

If you enjoyed this episode, I encourage you to read David Wootton’s The Invention of Science, a magnificent book that is a must-read for anyone listening to a podcast on the history of science. Much of the content of this episode comes from chapter four of his book, so be sure to read it if you want to know more about the impact Columbus’ discovery had on the medieval worldview. A link to his book is on the website, ahistoryof.science.

Thanks for listening. Hopefully until another history of science.