Stopping the Sun: The Revolution of Copernicus

There's no other daily experience as common as the movement of the sun. That displacement of Helios, the king star, across the sky indicates us the time of the day, and this way we distinguish the morning sun, which shines in a fresh and stimulant environment, from the midday sun, which nails its rays with all its strength, and from the melancholic sun in the sunset. Who hasn't got moved by a sunset's beauty? In our everyday-life language we talk about the "sunrise", "sunset"; we get interested in the cast shadows that the star produces, in order to protect us from its rigors; we admire the sundials because their gnomon keeps track of the time and we look for the beauty of its light which morphs differently in each corner of the planet. For millenniums, and even up to this date, the sun has been ruling the world with its solemn and formidable march.

Map of the World - Martin Waldseemüller, 1507

Because of this, it would be truly outstanding if someone tried to convince us that this primitive experience, so tied to our common sense, was just a pure appearance, that is, despite our perception of the sun moving from east to west, claiming that actually, the sun was completely motionless, and it's the Earth where we live, the one that rotates around it; and that our armed Earth, not only rotates around the sun but also rotates on its own imaginary axis, tracing a yearly movement which explains the astronomical seasons, the solstices and the equinoxes. If we were sensitive, we would think that nobody will even listen to those crazy ideas, that if someone made a similar claim we would make of him an insane man who would be forgotten as quickly as a wink.

However, someone ended up proposing these ideas, indeed. And not only we do not forget the author of such a crazy suggestion, but we referred to him as one of the most influential and well-known astronomers in history. This person claimed that the sun stayed still in the skies and these heliocentric proposals resulted in the expression of the "Copernican revolution" which means an extremely radical change. The name of the father of the idea, who published his work De Revolutionibus Orbium Coelestium (On the movement of celestial spheres) released the same day of his death, 1543, is Nicolaus Copernicus. A character with no mental illness whatsoever, living a sensitive and normal life, a true man of the Renaissance, a uomo universale (universal man) who had knowledge on medicine, law, mathematics, astronomy and who had attended different Italian universities, after finishing his studies at the University of Cracow, Poland. His passion for astronomy led him to review the Almagesto, the great classical work of Ptolemy, which collected all the ancient knowledge from the Hellenistic world. We also know that during his life he was quite interested in the following questions: "What if the center of the world was the sun and not the Earth? What if the Earth wasn't the center of the world but just another planet, a vassal of the king star?".

Crazy ideas, without a doubt, but it wasn't Copernicus the first one to come up with these ideas in the history of humanity. In the 3rd century BC, the astronomer Aristarchus of Samos, who was very likely to be linked to the Alexandrian school, had suggested an unconventional way to understand the cosmos, placing the sun in its center supposing that the planets, including the Earth, rotated around it, and that the Moon did the same but around the Earth. His proposal didn't have much success, despite his prestige as sage; the astronomers considered that if the Earth rotated around the sun, it must have been detected some parallax in the fixed stars, whereas the philosophers directly considered those ideas as ridiculous, a product of ungodliness, because, first, nobody felt that the Earth was moving, and, second, it was absurd that it (the Earth) did this, as from their point of view it was evident that it was situated at the center of the cosmos.

What drove Copernicus to decide to repeat again the attempt of claiming heliocentrism which would go against the most common of all common senses? Up to a certain point, that question can be answered if one reads carefully the letter, that was found in the epilogue of De Revolutionibus and that was sent to the Pope by Copernicus himself. Through this means, Paulus the 3rd received the explanation of why the cosmos should be perceived as a heliocentric system against the geocentric system of Ptolemy. Respecting the ideas of the Alexandrian though, Copernicus claimed in his letter: "His work (from Ptolemy) could be compared to the one of an artist who, taking from different places hands, feet, head and the rest of human limbs --very beautiful on their own, but not formed according to a single body and, therefore, without any correspondence between them whatsoever-- proceeded to arrange them to form something more similar to a monster than a man". What are those beautiful hands, those beautiful feet, that head so well-formed? Basically, the solutions that Ptolemy provided to explain the movement of the sun and of the different planets: he needed to explain the orbit of each planet that we see through a series of imaginary movements, very artificial, which were called epicycles, deferents, equal. These images on the trajectories could be explicatory more or less correct or useful, but to Copernicus' eyes, they were unconnected. The sum of all of them ended up forming a monstrous statue. Against it, Copernicus presented the cosmos as a beautiful and simple system. If the sun was at the center of the universe, planets would form a harmonious system, and explanations concerning their movements would be part of a more simple, unitary and beautiful doctrine. Should we then renounce to the benefits of common sense for something so useless as beauty?

When Copernicus died, his work De Revolutionibus spread throughout the European courts and landed in the libraries of important astronomers. However, it is important to highlight that it was not what we today call a "bestseller". The book was written with an important geometric rigor and it resulted incomprehensible to any reader who wasn't instructed in the geometry of the time. For example, emperor Charles the 5th received a copy of the work immediately after its edition and he was not able to understand it because of the high level of mathematics which was employed by the author, so it was deposited in the palace's library. Fortunately, some wily astronomers managed to read the entire work. Thanks to this, Copernicus' heliocentric ideas didn't have the same fate as the ones from Aristarchus of Samos and didn't fall into oblivion. Copernicus had disciples in life such as Georg Joachim Rethicus, who encouraged him to publish his great work and carried out several reports to spread the heliocentric ideas of his master. Also, he counted with followers who had been born after the publication of his book. Some of them are the English Thomas Dignes and William Gilbert, the German Johannes Kepler and, finally, in Italy, Giordano Bruno and Galileo Galilei.

80 years after the publication of De Revolutionibus, the world of wisdom burned within the controversy. The heliocentric hypothesis could seem insensitive, but it resulted in being profitable in the order of knowledge. Putting the Earth at the center of the universe, immobile, allowed the explanation of the movements of the sun, but if the perspective was changed, and instead of the Earth you put the sun at the center and the Earth rotating around it, the gates to a completely different world opened. The sun became just another star, and the other stars weren't confined in a sphere, as ancient philosophers like Aristotle believed, but instead, they spread throughout deep space. Kepler was the Copernican mathematician who ordered the movement of the planets and he formulated three laws that were admired by all contemporary and posterior sages. According to those laws, planets rotated in elliptical orbits (the sun was situated in one of the focuses of the ellipse) and they moved at constant aerological speed (the radius that joins the sun with a planet sweeps the same areas in the same times). Furthermore, these laws allowed to establish a relationship between the size of the ellipses and the rotation periods of the planets around the sun.

A great theory that, for the greater glory, had a fantastic propagandist: Galileo Galilei himself. In 1610, he wrote a small book titled Sidereus Nuncius (The Sidereal Messenger) which surprised his contemporaries because of the novelties which contained on the nature of celestial bodies. It was not an astronomical geometry treaty, but a field notebook where Galileo described the celestial observations that he had carried out with an instrument called "telescope". A convinced Copernican, Galileo dedicated his time to observe the Moon and the different planets. For weeks, he observed the different phases of the Moon and he managed to reach the conclusion that our satellite had mountains, that is, it was neither made up by sublime matter nor it was a perfect sphere, but it was suspiciously similar to the Earth. Moreover, he saw that Venus, like the Moon, presented different phases, that Jupiter had also moons or satellites, and that there was this planet called Saturn which wasn't a perfect sphere and it had in its surface, like the Moon and the Earth, a series of bumps (unveiled later to be the famous Saturn's rings). This way, the planetary world, and the Earth seemed to be very similar, too similar. The brief book of Galileo which contained all of these observations had an immediate impact; his descriptions and his engravings didn't contain indisputable pieces of evidence of neither the movement of the Earth nor the immobility of the Sun, but they suggested that the entire solar system was suspiciously unitary in aspect, which leads people to think that all its parts are from the same nature.

Galileo became the most famous scientist among the Copernicans when he decided to defend in public the heliocentric ideas. For this, he was condemned by the Inquisition to keep silence and forced to abandon his ideas. Never in the history of science, a silence was so eloquent and never a condemned person has been seen like someone so innocent by history. Modern science was built around an idea that seemed to break with the daily common vision, but finally, it proved that common sense doesn't always lead knowledge successfully.   

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