Heliocentrism, the Revolution That Makes the Earth Spin: Episode 6/10 of the Podcast Scientific Discoveries That Changed the World

What the collective memory retains are the works of Copernicus, and the violent struggle against the Church. This paradigm shift, which does not represent an abrupt break, is described as the first scientific revolution in history: it marks the birth of modern science…

Who were the people involved in this discovery? How did Copernicus' heliocentric theory become a scientific revolution?

To talk about it

Denis Savoy historian of science at Universcience and the Paris Observatory, co-author of the critical edition From the revolutions of the celestial bodies by Copernicus published by Editions des Belles Lettres in 2015.

Vincent Julian Emeritus Professor of Philosophy and History of Science at the University of Nantes, Researcher at the Atlantic Center for Philosophy, and author of What science can: survey published by Matériologique Editions, 2020

geocentric world

The geocentric world view was dominant until the arrival of Copernicus. However, some voices had already mentioned the possibility of heliocentrism, such as the Greek astronomer Aristarchus of Samos, in the third century BC, through a softened sentence in Archimedes' treatise…

But the Aristotelian view of a closed universe, with an immobile Earth, remains the dominant idea. It would be invalidated for centuries by The AlmagestPtolemy's treatise on astronomy, which would be a reference until Copernicus.

The one who invented the epicycles and the variations is Apollonius the Persian in the 3rd century BC, and the one who compiled all this ancient astronomy is Ptolemy in the 2nd century AD. He will publish in Greek a work entitled “Mathematical Synthesis” known by its Arabic name Almagest, which is one of the masterpieces of the history of science and knowledge. Ptolemy will use all the models. There is the cosmology: geocentrism, an instrument: plane and spherical trigonometry, and then the models. But Boutlemy will take some liberties in some of his models by not always maintaining a uniform circular motion, and in particular to explain the anomaly of the retrograde of the planet Mars, he will introduce the so-called equidistant point, a small deviation with respect to the circular motion. It is in fact a step towards the orbit of Kepler. Copernicus later rejected this system of Ptolemy. But you should know that the Almagest allows you to predict in advance, thanks to these models, the position of the sun, the moon and the planets in the sky, to make the ephemeris and to predict when the next solar or lunar eclipse will occur. Denis Savoy

long term revolution

This scientific revolution, which has passed as an expression into everyday language, did not happen overnight, but over the course of four centuries, thanks to successive modifications.

If there was a Copernican work The Revolutions of the Celestial OrbsWe will also have to take into account the contributions of Giordano Bruno, Kepler, Galileo, Descartes, and again Newton in establishing the heliocentric theory once and for all!

In the 17th century, all astronomers were already Copernicans. There were only a few misguided clerics who still believed in Aristotle. Evidence, because we would need physical evidence. The physical evidence of the Earth's motion around the Sun would arrive in 1727-1728 with the English astronomer James Bradley, who would discover stellar aberration, a small motion, a small apparent displacement of the stars in the sky. The most famous physical evidence of the Earth's rotation on itself was provided by Foucault in 1851 with his famous pendulum. It would also be the 19th century, and the century or book of Copernicus would remain deleted from the world. Index of Prohibited Books, three or four centuries late. Denis Savoy

Audio references

Greek thought: astronomyexcerpt from the “Knowledge of Man” program, RDF/RTF, 1954

Excerpt from Galileo's life By Bertolt Brecht, 1943 (broadcast in France 1955)

Read an excerpt from De Revolutionibus Orbium Coelestium (The Revolutions of the Celestial Bodies or Orbs), Nicolaus Copernicus, first printed in Nuremberg in 1543, reissued by Editions des Belles Lettres in 2015

From the sun By Annie Cordy

I heard someone whistle By Jay Jay Johansson