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    Albert Einstein Autograph Letter Signed "A. Einstein" on a postcard, 3.5" x 5.5", [Berlin]; undated, circa April 1926. Written in German, Einstein writes to Hans Reichenbach in Stuttgart, Germany, concerning Reichenbach's recent work on geometrization of the magnetic field as well as his criticism of Hermann Weyl's similar theory. An English translation is presented in full:

    Dear Mr. Reichenbach

    You are absolutely right. It would be incorrect to assume that "Geometrization" is something fundamental. It is nothing more than a donkey's bridge for discovering numerical laws. Considering this a theory for "geometric" representation would be just an inconsequential matter of personal preference. Fundamentally new is that Weyl, by subjecting the transformation formula in addition to invariance to a new requirement, namely the ("calibration invariant"). However, this advantage is neutralized because switching to equations of the fourth order will be necessary, which in turn means a substantial increase of the arbitrary factor.

    I am sending best regards,

    Yours A. Einstein

    If there is anything I can do for you, do let me know.

    At the time of this letter, Reichenbach and Einstein, still living and teaching in Berlin, were communicating about the former's construction of a theory establishing a connection between electricity and geometry, which he believed was as effective as that of general relativity connecting gravitation and geometry. Reichenbach concluded, however, that his theory was less successful than that of general relativity, and he informed Einstein in a prior letter that based on his experiments, evidence proved that geometrization of a physical field cannot be considered a significant advancement.

    In this letter, which Einstein appears to agree with Reichenbach, while at the same time criticizing Hermann Weyl's own theory on geometrization of the electromagnetic field. Sometime during 1926, Einstein and others helped Reichenbach obtain a faculty position in the physics department at Berlin University.

    Hans Reichenbach (1891-1953), born in Hamburg, Germany, to a half-Jewish father and a non-Jewish mother, studied civil engineering at the Technische Hochschule in Stuttgart, and then studied physics, philosophy, and mathematics in Berlin, Munich and G├Âttingen. He wrote his doctoral dissertation on The Concept of Probability in the Mathematical Representation of Reality, which was completed in 1915.

    After serving in the German army from 1915 to 1917, Reichenbach returned to Berlin, where he attended Albert Einstein's lectures on relativity and statistical mechanics. He was greatly influenced by Einstein and became a life-long friend of the Nobel Laureate. He wrote several popular articles defending Einstein, especially in the context of the observations of the solar eclipse of 1919 confirming the predictions of the general theory of relativity. In the early 1920s Reichenbach served on the faculty at the Technische Hochschule in Stuttgart.

    In 1920, he published The Theory of Relativity and A Priori Knowledge, which demonstrated the influence of Einstein's work. Reichenbach taught natural philosophy at the University of Berlin from 1926 to 1933, when he was forced to flee Germany under the Hitler regime. He subsequently taught in Istanbul, Turkey, and at UCLA in the U.S. Reichenbach obtained his American citizenship in 1943.

    Considered to be the greatest empiricist of the 20th Century, Reichenbach provided the backbone of empiricist philosophy. Inspired by what he perceived as a conflict between (neo-) Kantian a priorism and Einstein's relativity of space and time, Reichenbach developed a philosophy influenced by both science and an uncompromisingly empiricist epistemology.

    Condition: Lightly toned throughout, with two file holes at the top corners. Some ink smudging from a postal marking, does not affect legibility of text. Red ink on verso has also smeared slightly. Overall very fine.

    Auction Info

    Auction Dates
    October, 2018
    25th Thursday
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