CEFISES Seminar: Olivier Darrigol, « Relativity: a line that can be traced through centuries? »

Livestream https://www.youtube.com/@CEFISES

Series: MEPHISTO (MEtaphysics and PHIlosophy of Science: Transcendental Orientations)

Speaker: Olivier Darrigol (CNRS/Université Denis Diderot)

Title: « Relativity: a line that can be traced through centuries? »

Abstract

It is generally thought that the principle of relativity had long served mechanics when, around 1900, Poincaré and Einstein seized upon it to reformulate the electrodynamics of bodies in motion and to develop what we now call the theory of relativity. In reality, most physicists before Relativity did not regard Galilean relativity as a principle but rather as an empirical law (Galileo) or as a theorem (Newton and most of his successors). Yet it is true that in the seventeenth century Christian Huygens inaugurated a lasting tradition of deriving mechanical laws from constructive principles of relativity. The plural is necessary here, because since Newton two types of relativity were considered: on the one hand Galilean invariance, asserted by Galileo, and on the other a more general invariance with respect to a global acceleration of the system of bodies (somewhat like in Einstein’s equivalence principle). We will see how the principles of relativity flourished in the hands of Euler, d’Alembert, and Laplace, then became the basis for a popular derivation of Newton’s law of acceleration in nineteenth‑century French physics textbooks. It turns out that both Poincaré and Einstein were aware of this tradition, and that Poincaré drew from it the name principle of relative motion, later altered to principle of relativity. By giving this principle a major architectonic role, both authors were distant heirs of the great Huygens.