Concepts of Simultaneity: From Antiquity to Einstein and Beyond

1 Terminological Preliminaries

For the sake of verbal consistency and the prevention of possible misinterpretations it is desirable, if not necessary, to begin our study with some terminological comments. The topic of the present chapter is therefore primarily not the concept of simultaneity but rather the word or the verbal expression that denotes this concept. As far as semantic considerations are involved, without which a meaningful discussion of the differences between the terms under discussion would be impossible, it suffices at this stage to define the term “simultaneity,” as understood by common sense, as the “temporal coincidence of events.” We will ignore the philosophical and physical problems involved with this definition for now. As far as we know, the earliest recorded term that has been interpreted as denoting simultaneity is the Egyptian hieroglyph ,1 which is transliterated by “hȢw” and interpreted as a “term, that denotes the simultaneity C H A P T E R O N E Terminological Preliminaries 1 See, for example, A. H. Gardiner, Egyptian Grammar (London: Oxford University Press, 1957), p. 579. For later or less frequently used hieroglyphic expressions of a similar meaning see E. A. Wallis Budge, First Steps in Egyptian (London: Kegan Paul, Trench, Trubner & Co., 1923), pp. 43, 81, 116, 250, or R. Lambert, Lexique Hiéroglyphique (Paris: Geuthner, 1925), p. 142. Terminological Preliminaries 9 of events.”2 As the well-known egyptologist Eberhard Otto showed, however, the original meaning of this term was not a temporal but rather a spatial relation denoting “local proximity or neighborhood.”3 It is therefore probably also the earliest known example of the metonymical use (the use of one word for another) of spatial terms to denote temporal relations that is frequently encountered both in ancient and in modern languages.4 Today we still speak of a “short” or “long” interval of time; we say “thereafter” instead of “thenafter,” or “always” instead of “at all times.” In fact, we will soon see that the word “simultaneity” itself is such a metonymy. Let us first point out that in his statement that the hieroglyph denotes “simultaneity of events,” Otto did not use “event” in the sense in which it is used in modern physics. The term “event,” derived from the Latin “e-venire” (to come out), was used at the time of William Shakespeare5 to denote an occurrence , process, or phenomenon of indeterminate temporal duration, just like its German equivalent “Ereignis.”6 In the terminology of modern physics, however , the word “event,” just like “Ereignis,” became a technical term to denote “an occurrence of negligible spatial extension and temporal duration.”7 The use of the term in this sense gained general currency, especially with the advent of Einstein’s 1905 relativity paper, in which the definition of simultaneity is followed by the statement “a system of values x, y, z, t . . . completely defines the place and time of an event.”8 In his 1907 review paper9 Einstein called such a system a “Punktereignis” (point-event). Hermann Minkowski, in 2 “ . . . ein Terminus, der die Gleichzeitigkeit von Ereignissen angibt.” E. Otto, “Altägyptische Zeitvorstellungen und Zeitbegriffe,” in H. E. Stier and F. Ernst (eds.), Die Welt als Geschichte (Stuttgart: Kohlhammer, 1954), vol. 14, pp. 135–148. 3 “ . . . ein Wort, das eigentlich die räumliche Nähe, die Nachbarschaft bezeichnet.” Ibid., p. 146. 4 For examples of such space–time metonymies in Sumerian and ancient Hebrew, see M. Jammer, Concepts of Space (Cambridge, Massachusetts: Harvard University Press, 1954; enlarged edition, New York: Dover Publications, 1993), pp. 3–4. 5 Cf. J. Bartlett, A Complete Concordence of Shakespeare (London: Macmillan, 1966), p. 455. 6 The word “Ereignis” derives from “ir-ougen” (to appear to the eye), related to the German word “Auge” (eye). See G. Wahrig (ed.), Brockhaus-Wahrig: Deutsches Wörterbuch (Wiesbaden: Brockhaus, 1981), vol. 2, p. 548. From the etymological point of view the German word “Ereignis ” resembles the word “phenomenon,” which derives from the Greek “
´” (to make visible). 7 Ibid., p. 548. 8 “ . . . Wertsystem x, y, z, t, welches Ort und Zeit eines Ereignisses . . . vollkommen bestimmt.” 9 A Einstein, “Über das Relativitätsprinzip und die aus demselben gezogenen Folgerungen,” Jahrbuch der Radioaktivität und Elektronik 4, 411–462 (1907); quotation on p. 415. 10 Concepts of Simultaneity his famous 1905 lecture on space and time, called it a “Weltpunkt” (worldpoint ).10 Finally, let us quote from the introduction of a recent treatise on relativity...