Introduction

Abstract

The discovery of the general theory of relativity (GR) has often been justly praised as one of the greatest intellectual achievements of a single human being. At the ceremonial presentation of Hubacher’s bust of Einstein in Zürich, W. Pauli said:

“The general theory of relativity then completed and — in contrast to the special theory — worked out by Einstein alone without simultaneous contributions by other researchers, will forever remain the classic example of a theory of perfect beauty in its mathematical structure.”