EINSTEIN, Albert (1879-1955). Autograph letter signed ('A. Einstein') to Hermann Müntz, n.p. [postmarked Potsdam], 20 November 1929.

EINSTEIN, Albert (1879-1955). Autograph letter signed (\'A. Einstein\') to Hermann Müntz, n.p. [postmarked Potsdam], 20 November 1929.



In German, 1½ pages, 276 x 219mm. Envelope.



Unified Field Theory. Einstein explains the framework of his earliest major attempt at the unified field theory: \'The theory makes me very happy, and my belief in it is constantly increasing. I have recently lectured on it in Paris\'. He sets out in turn the equations and their corresponding identities, one of them marked as \'Vertauschungsrelation\' (transposition relationship), and then a process by which the orders of magnitude can be made to disappear: \'This is the strong indication of the compatibility of the equations\'. As a postscript on the verso, Einstein explains how in the first approximation his equations permit in a remarkable way a choice of coordinates according to specified conditions through which a decay of the equations can be achieved – he sets this out in both the Newtonian and the Maxwellian form.



The search for a unified field theory – one which could account for all of the fundamental forces in nature – was the abiding preoccupation of Einstein\'s last decades. His 1929 equations constituted his first major attempt. His lecture in Paris (on 8 November) was published in the Annales de l\'Institut H. Poincaré (1930), under the title \'Théorie unitaire du champ physique\'. Hermann Müntz was a Polish-German mathematician, author of the Müntz approximation theorem. He collaborated closely with Einstein in the years following 1927, and his help is acknowledged in a number of papers.