D O C U M E N T 2 3 6 M A R C H 1 9 2 6 3 9 9 [2]See Docs. 140 and 188 for the plan to create a chair of natural philosophy in Prague. [3]Philipp Frank. [4]Notgemeinschaft der Deutschen Wissenschaft. [5]The note Reichenbach refers to is most likely a typewritten manuscript titled “On the Unified Field Theory of Gravitation and Electricity” (“Zur einheitlichen Feldtheorie von Gravitation und Elektrizität,” PPiU, Archives of Scientific Philosophy, Reichenbach Collection, HR-025-05-10). On the basis of the correspondence with Einstein that ensued and of Reichenbach’s handwritten correc- tions to the text, it can be conjectured that only pp. 1–7 (parts I and II) of the manuscript were sent to Einstein. In the note, Reichenbach argues that in Weyl’s theory the operation of displacement (the affine connection) does not receive any physical interpretation, contrary to the metric tensor, which can be interpreted as giving an account of measurements with rods and clocks. The argument applies also to Eddington’s affine theory (Eddington 1921) and Einstein’s elaborations thereof (the latest of which is Einstein 1925t [Doc. 17]). In the note, Reichenbach argues that charged mass points should be seen as the physical realization of an asymmetric affine connection whose geodesics are to be iden- tified with the paths of charged particles subject to both gravitational and electromagnetic fields. This geodesic equation can be shown to be equivalent to the equation of motion of a charged particle sub- ject to a Lorentz force. Thus, Reichenbach believed he had presented the Einstein-Maxwell theory in a geometrical form “without any change of its physical content” (“ohne jede Aenderung ihres physi- kalischen Inhalts” p. 1). For further details on Reichenbach’s note and an analysis, see Giovanelli 2016. [6]Probably Reichenbach 1925a. In Doc. 230, Einstein had criticized statistical conceptions of cau- sality, from which Reichenbach likewise distances himself here. [7]In Reichenbach 1925a, the author investigates sentences of the kind “If A occurs with probabil- ity, then, with probability, B occurs.” He argues that if such a sentence is true as it stands, but false with A and B interchanged, then the event A must take place before the event B. 236. To Elsa Einstein [Paris,] Donnerstag [25 March 1926] Liebe Else! Glücklich angekommen Heute und morgen den ganzen Tag Sitzung.[1] Jetzt Abend. Habe mit Langevin[2] in kleinem Restaurant gegessen (göttliche Sauboh- nen) Heut abend noch bei Luchaire.[3] Vielleicht bleibe ich noch den 30. Herzliche Grüsse D. Albert. AKS. [143 195]. The postcard is addressed “Frau Elsa Einstein Haberlandstr. 5 Berlin” and post- marked “Paris R. P Depart 23* 25. III 1926.” On its recto, the card depicts a view of barges on the Seine along the Quai du Marché Neuf, toward Notre Dame Cathedral and the Petit Pont. [1]Einstein attended meetings of the ICIC subcommittee on the establishment of an international bureau of meteorology on 27 and 29 March at the IIIC in Paris. He may have also attended meetings of the subcommittee on bibliography of economic sciences (see Doc. 237 and League 1926b, p. 58 and p. 67). [2]Paul Langevin. [3]Julien Luchaire.
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