The Copernican Revolution and the Birth of Modern Science

Ptolemy and the Geocentric World

For one and a half thousand years, European science lived within the Ptolemaic universe: the Earth stands motionless at the center, around it revolve the Moon, the Sun, five planets, and the sphere of stars. The system described the observed motions of celestial bodies with astonishing accuracy—using a complex mathematical construction of deferents, epicycles, and the equant.

The Ptolemaic system was not simply “incorrect science.” It worked: it allowed for the prediction of eclipses, the motions of planets, and the creation of calendars. Its acceptance was rational—it explained observations. Its problem was not contradicting facts, but in its growing complexity and, ultimately, in the fact that it was incorrect.

Copernicus: The Solar Hypothesis

Nicolaus Copernicus (1473–1543), in "On the Revolutions of the Celestial Spheres" (1543), proposed the heliocentric model: at the center is the Sun, around it revolve the Earth and planets. The Earth is one of the planets, rotates on its axis (explaining the alternation of day and night) and revolves around the Sun (explaining the annual cycle).

It is important to understand: Copernicus’s model was no more accurate than the Ptolemaic one (he also used epicycles), and was not based on new observations. Its advantage was aesthetic and conceptual: it was simpler, more elegant, and explained the retrograde motion of planets without ad hoc epicycles.

Why is this a “revolution”? Thomas Kuhn in "The Structure of Scientific Revolutions" (1962) used precisely the Copernican transition as a paradigmatic example of a paradigm shift—a change in the basic assumptions and conceptual apparatus of science. This is not the accumulation of knowledge, but a qualitative shift: “revolution” in the literal sense.

Galileo: The Telescope and New Physics

Galileo Galilei (1564–1642) did what Copernicus did not: he looked through a telescope and found observational evidence. The moons of Jupiter (1610) are bodies that revolve not around the Earth. The phases of Venus are proof that it revolves around the Sun. Sunspots are a refutation of the “perfection” of celestial spheres.

Galileo also created the foundations of new mechanics. The principle of inertia: a body retains its state of rest or uniform straight-line motion unless acted upon by a force. This destroyed Aristotelian physics, in which motion requires constant influence.

Galileo’s conflict with the Inquisition (1633) was not simply a clash between science and religion. It was a conflict of two epistemologies: authority (Scripture, Aristotle) and experience (observation, experiment). Galileo defended the right of empirical observation to be an independent source of knowledge about nature.

Newton: Synthesis and the Mechanistic World

Isaac Newton (1643–1727) in "Mathematical Principles of Natural Philosophy" (1687) created a synthesis that united celestial and terrestrial mechanics. The three laws of motion and the law of universal gravitation made it possible to describe the movement of everything: from apples to comets.

The Newtonian universe is a clockwork mechanism. God created the world and set its initial conditions, but afterward it operates according to laws knowable through mathematics. This gave rise to mechanicism—the vision of the world as a machine. It gave an enormous impetus to science and technology—and raised an acute philosophical problem: if everything is determined by initial conditions and laws, is there room for free will, chance, God?

Laplace formulated this to the utmost: a creature, knowing the coordinates and momenta of all the particles in the universe at a given moment, could compute its past and future. “Laplace’s Demon” is the image of a deterministic universe. Quantum mechanics in the twentieth century will refute this demon.