This article is taken from Les Indispensables de Sciences et Avenir #212 January/March 2023.
He noted the history of the Holy See, the Church and science. In the 18th century, Prospero Lambertini, better known by the name of Benedict XIV and nicknamed the “Pope of the Enlightenment”, really opened the Christian religion to new ideas about the world. In 1741, shortly after the British astronomer James Bradley experimentally demonstrated the rotation of the Earth around the Sun, he officially authorized the publication of the complete works of Galileo, which disavowed the condemnation of the scientist by the Holy Office in the previous century. Sixteen years later, he lifted the ban on works defending heliocentrism – the Sun at the center of the universe. In doing so, he legitimizes in the eyes of Christendom a revolution of thought begun three centuries earlier by bold minds.
Among the latter was another clergyman, Nicolas de Cues, who in 1440 was asking himself dangerous cosmological questions. A mathematician and philosopher, it was on this day that he published De la docte ignorance, a revolutionary work on God and the universe. At a time when the scholastic philosophy of Thomas Aquinas (1225-1274) dominated, according to which only God is infinite, and not his creation, the saint was one of the first to believe that the world has an immeasurable magnitude, without a finite limit, contrary to what many Greek philosophers claimed , Aristotle was in the lead. He concludes that the Earth cannot be at its center and that it is not fixed. However, these bold ideas did not escape Aristotelian influence and remained close to Catholic dogma, since the model he proposed was not mathematized. However, Küssein’s work went unnoticed during his lifetime.
In his time, and for almost thirteen centuries, the geocentric model established by Ptolemy (100-168) dominated. This vision of the world, placing the Earth at the center of the Cosmos, based on a geometric approach that allows you to determine the position of “wandering stars” (the Sun, the Moon and planets other than the Earth), draws on his fundamental physics from the reflections of Aristotle. For the latter, the Cosmos is unchanged, the speeds are proportional to the forces, and the movements are nothing but the “means” of a celestial body for moving from one point to another.
The pillars of this system will finally shake this time in 1543 with the publication of Des Révolutions des Orbs Célestes. The work of the Polish canon Nicolaus Copernicus (1473-1543) proposes a Cosmos with the Sun seated at its center. It also suggests that our planet is subject to dual motion: its own rotation and rotation around this star. The echo of this theory will lay the foundation for a deep study of the axioms that govern the perception of the universe.
“However, it should be borne in mind that the concepts of scientific revolution and paradigm shift were formulated only in the 20th century by the American philosopher of science Thomas Kuhn (see – Pierre Luminet, astrophysicist and research director of the CNRS at the Marseille Astrophysical Laboratory. In fact, to commit this revolution will take time. Copernicus was little known during his lifetime. And for good reason, his work was not published until the year of his death.”
What is a revolution?
The history of science is a discontinuous succession of paradigm-driven theories: such is the now classic concept introduced by the American philosopher of science Thomas S. Kuhn (1922–1996) in his 1962 publication The Structure of Scientific Revolutions. . According to him, every major movement in science is based on a demonstrated and consistent model, which itself is based on a set of observations and results that form a consensus, a model on which and in relation to which theories are formulated. This is so long as the accumulation of anomalies that cannot be explained within the current paradigm renders the latter unusable, leading to its reversal – quantum physics and the unsolved problems of classical physics that it allows to explain are a good example of this. Then there is a break that pushes the disciplines to reform on the basis of newly demonstrated and accepted principles.
To illustrate this concept, Thomas S. Kuhn takes the example of the mechanistic or Copernican revolution, which he defines as the archetype of the scientific revolution. In this he followed the Prussian philosopher Immanuel Kant (1724-1804), who two centuries earlier called the development of the heliocentric system the “Copernican revolution”.
This new theory will initially intrigue a limited number of scientists. The French humanist Michel de Montaigne (1533-1592) would be among the first to welcome this. “Not because he considers it right on an astronomical level,” the astrophysicist clarifies, “but because it leads to a relativization of a person’s place in the world, as the atomists and Stoics did, opposing Aristotle.”
In the late 16th century and throughout the 17th century, several scholars followed in the footsteps of Copernicus. An admirer of the latter, the Danish astronomer Tycho Brahe (1546-1601) remained a supporter of a form of geocentrism, but he freed himself from the Aristotelian idea that there were spheres carrying stars and entered into modern science. in order to make observations with great accuracy.
His student and secretary, the German Johannes Kepler (1571-1630), was a convinced Copernican. Studying the movements of Mars for almost ten years, he came to the conclusion that the orbits of the planets around the Sun are not made in a circular, but in an elliptical trajectory. Mathematical relationships follow from this – Kepler’s laws that govern the motion of the planets; The Universe, instead of being only an incomprehensible Cosmos, therefore begins to be mathematized. And calculation becomes the main tool of these scientists who decided to shed light on the darkest corners of the world.
This revolution was not going to pass without consequences. The philosopher and Dominican friar Giordano Bruno (1548-1600) was among those who paid the heavy price. One of the first to rediscover the works of Nicolas de Couet, the Neapolitan became interested in the writings of Copernicus. Seduced by the idea of infinity, he argues that no star is at the center of the universe, since the latter extends equally in all directions, without limits. According to him, all the stars are the sun, and there are countless worlds like the Earth: man and the stars that surround him would not be the main concern of the universe! Even worse, the universe would have no worries!
Bruno also studies the question of motions, replacing the Aristotelian approach with a relativistic approach, according to which the motion of a body can only be studied in relation to a frame of reference. His rebellion against the theological framework will lead him… to the campfire of the Campo dei Fiori in Rome. This condemnation sets the stage for the Church’s suppression of innovative ideas that challenge both its fundamental precepts and Scripture.
A few years later, Galileo (1564-1642) would also pay the price and owe his life only to prudent refutation. An Italian physicist has made a number of observations thanks to a wonderful instrument, an astronomical telescope that he has perfected: the moons of Jupiter, sunspots in eternal evolution, new stars… so many discoveries that support the theory of the distant universe. from the unchanging Cosmos conceived by Aristotle.
The bezel had to have a deafening effect because it was available to everyone. The echo of the Copernican revolution could now be heard outside the narrow circle of authoritative astronomers and philosophers. Unthinkable for a church whose repressive machine has resumed its work: in 1616 the writings of Copernicus were banned; then, in 1633, for continuing to work on heliocentrism, Galileo was sentenced to the immediate cessation of all scientific activity and placed under house arrest until his death in 1642.
The triumph of a new vision of the world, quite understandable
In the same year, a certain Isaac Newton (1642-1727) was born in England, who was to lay the last stone in the Copernican building. Based on the laws established by Johannes Kepler, he developed his theory of universal gravitation, which describes the physical interaction that underlies the attraction between massive bodies. Thus, he contributed to the creation of what we now call classical mechanics. His work popularized the philosophy of René Descartes (1596-1650) that all physical phenomena could be explained by interactions between particles and simple mechanical principles. This is a vision of the Universe-machine: no, the phenomena occurring in the Universe have no end, no purpose that allows them to be explained. Unfortunately, after the trial of Galileo and because of the fear of religious censorship, the French mathematician never declared his adherence to the Copernican thesis during his lifetime. His Traité du monde et de la lumière will only be published posthumously.
Fundamentals of Philosophy by Rene Descartes. This extract from an edition published in 1699 illustrates the philosopher’s concept that physical phenomena can be explained in terms of simple mechanical principles. Credit: SPL/SUCRÉ SALÉ
This new philosophy, for which it became possible not only to describe physical phenomena in the way it was done until then, but also to decipher them thanks to mathematical language, lays, according to the French epistemologist Georges Gusdorf, also the foundations of experimental knowledge: phenomena have no final ” reason of existence”, it is necessary to proceed from experience in order to understand how mechanically, mathematically they occur. The approach, which marks the triumph of a new vision of the world, which has become “a combination of matter and motion, subject to the requirements of calculation”, is completely understandable.
An astronomer watches the sky through a telescope. The illustration is taken from Selenographia, sive Lunae descriptio (1647), in which the Polish astronomer Johannes Hevelius made the first map of the Moon. Credit: BRIDGEMAN PHOTO
After Newton, and following this mechanistic principle, physicists worked to explain other phenomena by discovering the laws that govern them: light, magnetism, heat, or electricity. Thus, more than a century and a half after its publication, Copernican theory profoundly reformed scientific thought in the broadest sense.
For Jean-Pierre Luminet, “the most profound originality of the Copernican revolution lies not in the heliocentric theory, because, after all, Greek scientists and philosophers such as Aristarchus of Samos proposed it two thousand years ago. is called the Copernican principle, according to which there is no privileged position in the universe – whether it is finite or infinite. The meaning of man in the world, both in space and in time.
Since then, physics, as well as science in a broad sense, has been trying to build itself following this principle. Darwin’s theory of evolution, for example, is partly built on this new paradigm, as is modern relativistic cosmology. The Aristotelian universe gave way to a larger and more connected world.