Abstract
Volume 6 of The Collected Papers of Albert Einstein includes Einstein's writings during 1914 - 1917, his first three years in Berlin. Einstein moved to Berlin in April 1914 from Zurich where he had been a Professor at his old undergraduate school, The Federal Institute of Technology, since February 1912. In the spring of 1913, Max Planck and Walther Nernst journeyed from Berlin to visit Einstein in Zurich in order to make him an offer that, in the end, he could not refuse: a professorship with no teaching obligations and the directorship of the fledgling Kaiser Wilhelm Institute for Physics. Soon after their arrival in Berlin, the Einsteins separated. Mileva departed for Zurich with their sons Hans Albert and Eduard. At this point Einstein's relationship with his cousin Elsa Löwenthal deepened further. Thus, as the editors put so well, in the period covered in this volume, `Einstein's life and career entered a new phase'.
Amongst the key documents in Volume 6 are publications from 1914 in which Einstein concluded that gravitational field equations `cannot possibly be generally covariant'. After having realized his errors, Einstein returned to the theme of general covariance and, in 1915, published three papers in succession in which he developed the generalized theory of relativity. The third paper, published on 25 November 1915 and entitled `The Field Equations of Gravitation', is the capstone of the trio, correcting as it does errors in the previous two. A week prior to its publication Einstein published a result of his new theory: the calculation from the new generally covariant field equations of Mercury's perihelion motion of 43 seconds of arc per century, in agreement with observation. Some time later, Einstein told his former collaborator Adriaan Fokker that upon seeing the result emerge he had heart palpitations. On 8 February 1917 Einstein essentially started the field of modern cosmology with the publication of `Cosmological Considerations in the General Theory of Relativity'. One of the many points of interest in this pioneering paper is Einstein's modification of his field equations with the so-called `cosmological constant' in order to incorporate, as best he could, Machian ideas on effects of distant rotating masses.
Besides tidying up general relativity theory with his review paper of 1916, Einstein made new and far reaching contributions to the quantum theory of radiation. In two papers of 1916 he published his A and B coefficients and went on to conclude that atoms need not emit radiation in spherical waves, but in light quanta with a specific direction and definite momentum. The presence of probability in this theory was to Einstein a `weakness'.
The eclectic set of publications in Volume 6 include ones on molecular currents in magnets, book reviews, contributions to Bohr's atomic theory and statements on the war, as well as documents relating to Einstein's participation as an expert witness in a patent dispute between the German firm Anschütz & Co. and the American Sperry Gyroscope Company. In the end the court chose to follow the former patent clerk's report and decided to prohibit Sperry Gyroscope from manufacturing gyrocompasses that incorporated methods patented by Anschütz.
In summary there is something for everyone in this fascinating collection of papers published by Einstein during 1914 - 1917 and assembled in what we have come to expect as a meticulous scholarly presentation replete with an up to date listing of secondary studies and informative footnotes. We eagerly await further volumes of this truly historic project.