World of Science at AEASC

Throughout Einstein’s writings, one can watch him searching for that world picture, for a comprehensive Weltanschauung, one yielding a total conception that, as he put it, would include every empirical fact (Gesamtheit der Erfahrungstatsachen) – not only of physical science, but also of life.

Einstein was of course not alone in this pursuit. The German literature of the late nineteenth and early twentieth centuries contained a seemingly obsessive flood of books and essays on the oneness of the world picture. They included writings by both Ernst Mach and Max Planck, and, for good measure, a 1912 general manifesto appealing to scholars in all fields of knowledge to combine their efforts in order to “bring forth a comprehensive Weltanschauung.” The thirty-four signatories included Ernst Mach, Sigmund Freud, Ferdinand Tonnies, David Hilbert, Jacques Loeb. and the then still little-known Albert Einstein.

But while for most others this culturally profound longing for unity – already embedded in the philosophical and literary works they all had studied – was mostly the subject of an occasional opportunity for exhortation (nothing came of the manifesto), for Einstein it was different, a constant preoccupation responding to a persistent, deeply felt intellectual and psychological need.

This fact can be most simply illustrated in Einstein’s scientific writings. As a first example, I turn to one of my favorite manuscripts in his archive. It is a lengthy manuscript in his handwriting, of around 1920, titled, in translation, “Fundamental Ideas and Methods of Relativity.” It contains the passage in which Einstein revealed what in his words was “the happiest thought of my life” [der gluecklichste Gedanke meines Lebens] – a thought experiment that came to him in 1907: nothing less than the definition of the equivalence principle, later developed in his general relativity theory. It occurred to Einstein – thinking first of all in visual terms, as was usual for him – that if a man were falling from the roof of his house and tried to let anything drop, it would only move alongside him, thus indicating the equivalence of acceleration and gravity. In Einstein’s words, “the acceleration of free fall with respect to the material is therefore a mighty argument that the postulate of relativity is to be extended to coordinate systems that move nonuniformly relative to one another . . . .”

For the present purpose I want to draw attention to another passage in that manuscript. His essay actually begins in a largely impersonal, pedagogic tone, similar to that of his first popular book on relativity, published in 1917. But in a surprising way, in the section titled “General Relativity Theory,” Einstein suddenly switches to a personal account. He reports that in the construction of the special theory, the “thought concerning the Faraday [experiment] on electromagnetic induction played for me a leading role.” He then describes that old experiment, in words similar to the first paragraph of his 1905 relativity paper, concentrating on the well-known fact, discovered by Faraday in 1831, that the induced current is the same whether it is the coil or the magnet that is in motion relative to the other, whereas the “theoretical interpretation of the phenomenon in these two cases is quite different.” While other physicists, for many decades, had been quite satisfied with that difference, here Einstein reveals a central preoccupation at the depth of his soul: “The thought that one is dealing here with two fundamentally different cases was for me unbearable [war mir unertraeglich]. The difference between these two cases could not be a real difference . . . . The phenomenon of the electromagnetic induction forced me to postulate the (special) relativity principle.”