3 4 0 D O C . 4 3 N E W S O U R C E S O F E N E R G Y
Published in Berliner Tageblatt, 25 July 1920, Morning Edition, p. 4.
[1]The Berliner Tageblatt requested expert opinions of the most eminent physicists and chemists of
the University of Berlin: Einstein, Fritz Haber, Willy Marckwald (1864–?), Professor of Physical
Chemistry at the University of Berlin, Walther Nernst, Max Planck, and Heinrich Rubens. According
to the introductory part of the long article, the reason for the inquiry was a search for alternative
sources of energy to replace coal, which the French were demanding as reparations at a recent confer-
ence in Spa, Belgium. A final agreement required that Germany deliver two million tons within the
next six months (see Trachtenberg 1980, pp. 144–152).
The article including this document bears the title “1 Gramm Materie = 3000 To. Kohle.”
According to his first biographer, Einstein was evaluating the practical realization of the transfor-
mation of mass into energy months before Rutherford’s discovery (see Moszkowski 1922, the chapter
entitled “Ein Gramm Kohle,” especially p. 47).
[2]Ernest Rutherford (1871–1937), Professor of Physics at the University of Cambridge and Direc-
tor of its Cavendish Laboratory, first reported on his findings on artificial disintegration to the Royal
Institution of Great Britain on 6 June 1919 (Rutherford 1919a, 1919b).
[3]In his Bakerian Lecture, delivered on 6 June 1920 (Rutherford 1920), Rutherford gave an over-
view of his investigation of the artificial disintegration of nitrogen and oxygen bombarded with α-par-
ticles, and announced the discovery of particles with mass 3 and positive charge 2. He supposed this
compound atom to be an isotope of helium. His subsequent research, however, showed that only pro-
tons and α-particles are produced (see Rutherford 1922). For a historical account of Rutherford’s dis-
covery of artificial disintegration, see Stuewer 1985.
[4]At the Cardiff meeting, Arthur S. Eddington, aware of the immense amount of energy in ques-
tion, remarked that the fulfillment of “our dream of controlling this latent power” would serve “the
well-being of the human race—or its suicide.” Eddington 1920b, p. 46.
[5]A few months earlier, Einstein had praised Pflüger’s little book to Alexander Moszkowski
(1851–1934). Alexander W. Pflüger (1869–1945), Professor of Chemistry at the University of Berlin,
argued for the practical importance of the principle of relativity by calculating the calories that could
be produced by a complete transformation of 1 kg of carbon into energy (Pflüger 1921, p. 18). Einstein
showed reserve toward Pflüger’s optimism (Moszkowski 1922, p. 47).
[6]Einstein also discussed the idea of self-sustaining nuclear decay with Moszkowski: “It does
seem possible that, under certain conditions, nature will automatically sustain atomic decay after it
has been purposefully initiated, analogously to a fire that spreads even though only a spark has been
intentionally lit” (“Es scheint nämlich denkbar, daß unter gewissen Bedingungen die Natur den Atom-
zerfall automatisch fortsetzen wird, nachdem ihn die Absicht des Menschen planvoll eingeleitet hat;
nach Analogie eines Brandes, der sich ausbreitet, wenn als absichtliche Vorbereitung, auch nur ein
Funke auftritt.” Moszkowski 1922, pp. 48–49).