## Spielen Gravitationsfelder im Aufbau der materiellen Elementarteilchen eine wesentliche Rolle? [Do Gravitational Fields Play an Essential Role in the Structure of the Elementary Particles of Matter?]

FIRST EDITION IN ORIGINAL WRAPPERS of one of Einstein's major papers on the modification of general relativity and the beginning of his unified field theory.

"As so often the case in relativity, the story of quantum gravity begins with Einstein himself. Soon after the final formulation of general relativity, he pointed out the need for a quantum modification of the theory… [In "Do Gravitational Fields Play an Essential Role in the Structure of the Elementary Particles of Matter?"] he began to speculate whether gravitation plays a role in the atomistic structure of matter:

*There are reasons for thinking that the elementary formations which go to make up the atom are held together by gravitational forces… The above reflections show the possibility of a theoretical construction of matter out of the gravitational field and the electromagnetic field alone…*

"In order to construct such a model of an 'elementary particle,' Einstein shows that it is necessary to modify the original gravitational field equations… The major interest of this paper is that his attention now shifted from possible quantum modifications of general relativity to the search for a unified theory of the electromagnetic and gravitational fields, on the basis of which he hoped to explain the structure of matter. Quantum effects are to be derived from such a theory, rather than postulated ad hoc. Einstein remained committed to this approach for the rest of his life: the search for a 'natural' mathematical extension of the general theory in the hope that such a theory would somehow explain the quantization of matter and energy" (Iyer and Bhawal, *Black Holes, Gravitational Radiation and the Universe*).

IN: Sitzungsberichte der Preussischen Akademie der Wissenschaften, Vol XX, pp. 349-356. Berlin: Akademie der Wissenschaften, 1919. Octavo, original wrappers; custom box. A BEAUTIFUL FINE COPY.

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