Hello! In this Zenius blog article, I will discuss the shape of the earth. Including the theory, namely the round earth theory and its counterpart, the flat earth theory. Lately, there has been a lot of discussion on various social media about the flat earth. Not only in Indonesia, even in America the view of a flat earth has been popular and quite a lot of people believe it. Teachers at schools who are expected to be able to counter this often go along with the flow, in fact many join in and believe that the earth is flat. Okay, instead of getting confused, now we just prove which one is true. Round earth theory or flat earth theory? To get the answer, don’t forget to read this article to the end!
Illustration of round earth and flat earth (doc: Zenius Archives)
Illustration of round earth and flat earth (doc: Zenius Archives)
List of contents
A Brief History of Earth Science and the Universe
From Mythology to Rationality
Geocentric vs Heliocentric
The Spherical Earth Theory and Its Supporting Evidence
Where Did the Flat Earth Theory (Modern Flat Earth Society) Come From?
The Flat Earth Theory Has Long Been Broken
The Debate on the Flat Earth Issue Has Not Ended
A Brief History of Earth Science and the Universe
But before I discuss about the round or flat earth theory, we need to know about the history of the journey of human knowledge about the universe.
One of the things that distinguishes humans, Homo Sapiens, from other species is the ability to imagine. For example like this, if other species meet a lion, say a deer or a horse, they will more or less think like this “be careful, lion!”. But humans, thanks to their imagination, can think like this, “be careful, the lion is the guardian god of this forest!” This imagination has helped humans to survive and become the most powerful species on earth. How come? Thanks to the imagination, humans can also form a group, organization or laws and regulations that other species may not be able to do. On the other hand, this imagination also creates myths and beliefs about objects or phenomena that exist in this world.
If you want to tell more about this ability of the human imagination, you can watch Glenn’s story about the Origins of the Concept of Money. So don’t imagine that what you think now about the sun, moon, stars or various things that happen in this world is the same as what ancient people thought. In the ancient Egyptian civilization, for example, the sky was depicted as a giant woman, in the form of the goddess Nut. Nut stretched out his legs and arms to the four corners of the world so that they covered the earth. Every morning Nut gave birth to the sun and in the evening he ate the sun again. The cycle repeats every day.
Meanwhile, Geb, god of the earth, lay under the sky (Nut). Geb is depicted as a man lying under the arches of the sky Nut. The Egyptians believed that the earthquake was caused by Geb laughing. Meanwhile, the seawater in this world is Nut’s tears when Geb separates it.
Sounds like a wild imagination? Again, don’t equate modern human knowledge with ancient humans.
Three layers of the universe believed by the people of Ancient Babylon (doc: Wikipedia)
Three layers of the universe believed by the people of Ancient Babylon (doc: Wikipedia)
Unlike the ancient Egyptians, who depicted the universe as personified gods and goddesses, in the Babylonian civilization, the universe was divided into a three-layered structure with a flat earth floating above the water and under the sky. Well, it was in this Babylonian civilization that the science of astrology began to advance, but even so they still considered heavenly bodies to have magical powers.
People imagined certain shapes resulting from the arrangement of the stars, and associated them with certain aspects of nature or their mythology. The Babylonians believed that the arrangement of the stars determined human destiny. This is what we now call the zodiac or horoscope.
Meanwhile, the Sun, Moon and planets (at that time Mercury, Venus, Mars, Jupiter, Saturn) were each given 1 day as an offering. So one week is 7 days. We still recognize the names of several days today, namely Sunday (sun), Monday (month), Saturday (Saturn). Well, here you can see how people in the past drew conclusions, not only from the facts they saw, but many were accompanied by imaginations. It is this imagination that eventually gives birth to the mythologies that exist in various civilizations. Even so, this imagination is actually not always wrong. Sometimes, it can also be true. But, the imagination must be validated (truth tested).
From Mythology to Rationality
At the beginning of the Ancient Greek civilization, there were actually many thinkers who had started to be rational, but still concluded that the earth was flat. For example, Thales argued that the earth is flat and floats on water. The earth is like a piece of wood floating in the middle of the ocean.
Anaximander believed that the earth was in the form of a short cylinder with a flat surface and floating in the air. Anaximenes believed that the heavenly bodies were flat, and he likely also thought the earth was flat. However, what distinguishes the arguments of thinkers in Ancient Greece from before is, they have started to argue based on the observations they have made, even though they are not perfect. With such a culture, figures like Aristotle were born. In 340 BC, he is believed to be the first to write this opinion in his book On the Heavens.
He realized that lunar eclipses were caused by the Earth being between the Moon and the Sun. The Earth’s shadow on the Moon’s surface is always round. This is only possible if the Earth is round. If the Earth is flat, the shadow is oval and only round when the Moon is above the crown.moon_earth_shadow
latitude-arms From past travels, the Greeks learned that the North Star appears lower in the sky when the observer is farther south (since it is above the North Pole). The North Star is directly above the crown of an observer at the North Pole, and above the horizon when he is at the equator.) This is only possible if the Earth is round.
Ships appear and sink on the horizon (the farthest observable limit). If there is a ship sailing away from us, then the hull will sink first on the horizon. Vice versa, the top of the ship will be seen first on the horizon when it approaches us.From this evidence, the first theory which states that the earth is round was presented by Aristotle. Aristotle’s ideas were agreed upon by later philosophers such as Eratosthenes, Euclid, Aristarchus, and Archimedes. Eratosthenes even managed to measure the circumference of the earth using a stick located in two different places. He used the difference in the shadows between the two sticks due to the curvature of the earth to measure the total circumference.
Illustration of Eratosthenes using a stick to calculate the circumference of the earth (doc: Wikipedia)
Illustration of Eratosthenes using a stick to calculate the circumference of the earth (doc: Wikipedia)
In this way, Eratosthenes was able to obtain a value of 46,250 km around the earth. Only missed by about 15% with the circumference of the earth measured in modern times (40,075 km).
You can read the full story and calculations in the following Zenius Blog article. Aristotle also suspected that the Earth was fixed in place and the heavenly bodies revolved around the Earth, but he had no basis for this argument. Since then, the shape of the earth has rarely been debated anymore among ancient Greek philosophers.
Geocentric vs Heliocentric:
The discussion about the shape of the earth among philosophers can be said to have been ‘finished’ after Aristotle put forward his opinion above. After that, questions began to shift, namely about the center of the universe. Is the earth the center (geocentric)? In a sense, the earth is the center of all objects in outer space, and the sun, moon, stars move around the earth. When the Earth is used as a reference for observation, you will see retrograde movements of the planet. As an illustration, the following shows the movement of the Sun, Mars and Jupiter when observed from Earth. The scientist who insists on the geocentric philosophy is Claudius Ptolemy from Alexandria trying to explain this phenomenon while complementing Aristotle’s model. In his Almagest, Ptolemy proposed a model of the Earth as the center of the solar system. Like Aristotle’s model, but with a more complex version that takes into account the positions of the sun, moon and planets from Earth. To explain the retrograde motion of the planets, Ptolemy added circular sub-orbits within an epicicle. With this model,
Ptolemy was able to predict the positions of these objects in the sky, but still, the model was too complicated and not completely accurate. The following depicts the motion of Mars using the Ptolemaic model. (point P stands for planet and yellow point stands for sun). Which is Right: Round Earth or Flat Earth? 25 ezgif-2762044476 Why is it that when the Earth is used as a reference for observers, the movement of the planet is retrograde? The twisting (retrograde) orbit can be explained simply if the earth and planets revolve around the same center (the sun). Because the distance between the Earth and the planet to the sun is different, when the Earth has evolved once, the observed planet has not completely evolved, if it is farther away from Earth. To make it clearer, you can see the GIF on the side.
Now the model of the sun as the center of the solar system (heliocentric) is what Nicolaus Copernicus from Poland tried to propose in the sixteenth century AD.