In 1905, a young employee of the patent office in Bern, Switzerland, publishes a series of papers, three of which he describes to his friends as "revolutionary". The story is well known: one of these three papers is entitled Sur l’électrodynamique des corps en mouvement and is universally regarded as marking the birth of special relativity.
The story is more complicated, however, because from 1895 onwards Lorentz and Poincaré, among others, sought to resolve the contradictions raised by repeated failures to detect the Earth's motion through the ether. Special relativity would provide a solution to this problem.
The principle of relativity ----------------------------
The idea of relativity took shape over the centuries through developments that sparked extensive debate about the nature of phenomena. Before the 20th century, space and time were the principal players in the principle of relativity. The first key concept is the motion of objects. Aristotle regarded motion as absolute, implying the existence of a privileged observer. In the Middle Ages, scholars attempted to relate the absolute nature of rest and motion to an experimental context. The concept of relativity itself, however, was truly discovered by Galileo (1564–1642), who supported the Copernican theory. Nicolaus Copernicus (1473–1543) had already begun to reject the idea of an absolute frame of reference. But Galileo went much further: he asserted that "true" motion did not exist, that "motion is as nothing". Thus, no experiment conducted entirely within a mechanical system could detect that system's motion. This was Galilean relativity, supplemented by the principle of inertia, which states that any body left to itself persists in its state of motion and obeys the law of composition of velocities.
These principles need to be formalized through mathematical relations involving time. The concept of time had attracted attention in antiquity, but it was Newton's rational mechanics that formalized it as a measurable quantity. In his 1687 Principia, Isaac Newton expressed the principle of inertia in equations and, by codifying ideas about space and time, established two fundamental principles of his mechanics. The first was absolute space: there exists a privileged coordinate system in Euclidean space relative to which motions can be described as absolute. The second similarly asserted the existence of a universal time, according to which the present instant is the same regardless of the observer's motion.