Einstein’s Apple 1 His First Principle of Equivalence August 13, 2012 Engelbert Schucking Physics Department New York University 4 Washington Place New York, NY 10003
[email protected] Eugene J. Surowitz Visiting Scholar New York University New York, NY 10003
[email protected] Abstract After a historical discussion of Einstein’s 1907 principle of equivalence, a homogeneous gravitational field in Minkowski spacetime is constructed. It is pointed out that the reference frames in gravitational theory can be understood as spaces with a flat connection and torsion defined through teleparallelism. This kind of torsion was first introduced by Einstein in 1928. The concept of torsion is discussed through simple examples and some historical observations. arXiv:gr-qc/0703149v2 9 Aug 2012 1The text of this paper has been incorporated as various chapters in a book of the same name, that is, Einstein’s Apple; which is available for download as a PDF on Schucking’s NYU Physics Department webpage http://physics.as.nyu.edu/object/EngelbertSchucking.html 1 1 The Principle of Equivalence In a speech given in Kyoto, Japan, on December 14, 1922 Albert Einstein remembered: “I was sitting on a chair in my patent office in Bern. Suddenly a thought struck me: If a man falls freely, he would not feel his weight. I was taken aback. The simple thought experiment made a deep impression on me. It was what led me to the theory of gravity.” This epiphany, that he once termed “der gl¨ucklichste Gedanke meines Lebens ” (the happiest thought of my life), was an unusual vision in 1907.