Hamburg 2016 – scientific programme

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AGPhil: Arbeitsgruppe Philosophie der Physik

AGPhil 3: Philosophy of Physics 3

AGPhil 3.2: Talk

Tuesday, March 1, 2016, 14:00–14:30, VMP6 HS G

The Einstein-Reichenbach Correspondence on the Geometrization of the Electromagnetic Field — •Marco Giovanelli — FORUM SCIENTIARUM Doblerstraße 33 72074 Tübingen

This paper analyzes a correspondence between Reichenbach and Einstein from the spring of 1926, concerning what it means to 'geometrize' a physical field. The content of an unpublished typewritten note that Reichenbach sent to Einstein on that occasion is reconstructed, showing that it was an early version of sec.49 of the Appendix to Philosophie der Raum-Zeit-Lehre, on which Reichenbach was working at the time. In the note Reichenbach proposed a toy-geometrization of the electromagnetic field: general relativistic equations of motion are rewritten in a way that also charged particles, under the influence of an electromagnetic field, follow their 'natural path' defined by a non-symmetric affine connection. Einstein criticized Reichenbach's note from a technical point view (in particular charged particles cannot all move on geodesics of a single connection), but agreed with its philosophical point: the geometrization does not mean something essential. The paper draws two lessons from this episode: From a historical standpoint, the correspondence inaugurated a philosophical reflection about the role played by geometric considerations in physical theories. From a systematical standpoint, pace Reichenbach, his theory shows the limits of any attempt to impose geodesic equations of motion to a non-universal force.