Beschreibung:

ALBERT EINSTEIN (1879-1955) Autograph manuscript signed ('A. Einstein') of an article, a response to Ernst Reichenbächer's 'To what extent can modern gravitational theory be established without relativity?', stamped '22 November 1920', including a number of emphases, cancellations, emendations and insertions, 3 pages, folio , one on verso of the opening page of a typed letter from Einstein to Professor V. Bjerknes, Berlin, 12 November 1920, responding to a paper on electro-magnetism ('the electromagnetic field seems to me more fundamental than the ponderable mass'). Provenance : Dr Mühsam, Berlin (gift from Einstein; letter signed by Ilse Einstein, 1 December 1920, 'I am commissioned by Professor Einstein to send you for the benefit of a Jewish charitable cause the accompanying brief autograph manuscript by Professor Einstein'). A DEFENCE OF THE THEORY OF RELATIVITY. Einstein immediately accepts that the answer to the question in Reichenbächer's title is affirmative, but goes on to justify the principle of relativity by analogy with the second law of thermodynamics: 'When there are two theories that in one field do justice to the totality of ascertained experience, one prefers the one that needs fewer mutually independent assumptions. From this point of view, the principle of relativity is, for electrodynamics and for the theory of gravitation, as valuable as the second theorem is for the theory of heat, because it would take many mutually independent hypotheses to reach the conclusions of the theory of relativity without using the principle of relativity'. Einstein goes on to offer a brief epistemological justification of relativity, before turning to a series of specific objections to the relativistic theory of gravitation raised by Reichenbächer: first, the argument against the principle of equivalence, that 'gravitational fields for finite space-time domains in general cannot be transformed away', to which Einstein responds that his opponent 'fails to see that this is of no importance whatsoever'; second, that 'fields existing with respect to a coordinate system rotating against an inertial system' are, allegedly, only 'fictitious' but not 'real' fields, pointing out that this is only correct in Newtonian theory; although there is some uncertainty about this area, Einstein himself is of the opinion that 'all, even the most distant, masses of the universe take part in establishing the gravitational field in every location'. Reichenbächer's third objection involved a misunderstanding of Einstein's consideration of the two celestial bodies that rotate relative to each other. In a strongly-worded conclusion, Einstein confesses that 'It is completely incomprehensible to me how Herr Reichenbächer , towards the end of his analysis, arrives at the conclusion: all laws of nature must be phrased in a generally covariant form. Because if acceleration has absolute meaning, then the nonaccelerated coordinate systems are preferred by nature, i.e., the laws then must -- when referred to them -- be different (and simpler) than the ones referred to accelerated coordinate systems. Then it makes no sense to complicate the formulation of the laws by pressing them into a generally covariant form'. Einstein's vigorous refutation was published together with Reichenbächer's paper in Die Naturwissenschaften 8 (1920), pp. 1010-1011.