IMG63

Ernst Mach

VIII

There is cvidencc that Mach bccamc morc sympathctic to Einstcin’s approach during late 1913 and carly 1914. The cvidcnce is not con-clusive, but it must bc rccognizcd that it does exi$t.⁶⁷ Therc are thrce di (Tereni groupings of rclcvant information o£ which the first two arc quitc brief and ncbulous. An undated letter from Einstein to Mach, written probably in latc 1913 or carly 1914, started oif with the commcnt: “I am vcry plcased by the fricndly interest which you havc shown in my ncw theory," as if Mach had carlier written a sympathetic letter to Einstein.⁶⁸ Another piece of evidencc comcs in a letter from Leo Gilbert (alias Leo Silbcrstcin), an “cncrgeticist” and notorious opponent of Einstein, who wrotc to Mach on Dcccmber 1, 1913: “Theday before yesterday I permitted mysclf to send you a paper against the principlc of relativity." Two months later, Gilbert wrotc to Mach again and madę the following interesting rcmark: “With respcct to that, it is not important if we arc not agreed on the matter of the principlc of relativity." If Mach and Gilbert were not 3grecd, and Gilbert opposed the theory, then Mach presumably favored it. The problem, of coursc, is that too much rests on conjecture. For cxample, they may havc disagreed over Machs theory of rclativity, rather than over that of Einstein.

The next grouping of cvidencc in favor of the notion that Mach bccamc morc sympathctic to Einstcin's theory of rclativity is con-sidcrably morc substantial, but is, noncthclcss, subject to different in-terpretations, and thus must also bc regardcd as ambiguous and in-conclusivc. Evcn though many of Petzoldt’s letters to Mach explicitly refer to Einstein’s theory of relativity, only two of the twenty-one cx-tant letters from Mach to Pct/.oldt refer to that theory or to Einstein as a person. Thesc two letters, howcver, whilc they do not State Mach’s approval of any of Einstein’s idcas, ccrtainly scem sympathctic, at the vcry least. The first letter was sent in carly 1914: “The accompanying letter from Einstein is proof of the penctration of positiyistic philoso-phy into physics; you can takc satisfaction in that. A ycar ago philos-ophy was still a mere stupidity.—'The details confirm this. A ycar ago the paradox with the clock had not cvcn occurrcd to Einstein.”⁶⁹

The sccond Mach-to-Petzoldt letter was posted a few days later: “I havc mcanwhilc rcccived a copy of the Zeitschrift fur positiuistischc,

Phtlosophie, which includes your articlc on relativity [i.c., “The Theory of Rclativity of Physics” (1914)], which plcascs mc not only because it acknowlcdgcs my modest contributions to this theme, but for other rensons also.” ⁶⁰

The major qucstion is whether Mach wrotc thcsc letters mcrely to please Pctzoldt or also because hc himsclf now felt morc sympathetic to Einstein’s theory of rclativity. If indeed, Mach did become morc ] sympathetic, then the rcason was probably that Mach had comc to j sharc Pctzoldt’s vic\v that the generał theory was consistcnt with the “rclativization’' of the constancy of the yclocity of light. If. on the other hand, Mach was trying to make Petzoldt happy, and in no way \ changcd his opposition to Einstcin’s theories, then Mach had only 1 himsclf to blamc for the cventual conscqucnccs.

Mach’s two letters, in addition to the one from Einstein, causcd Pctzoldt to bclieve that both Mach and Einstein supported his inter-pretation of Mach as an epistemological and scicntific forerunner of Einstein, an interpretation which in fundamcntal terms was falsc, and which Mach at the time, and Einstein somewhat later, knew was falsc.⁶¹ The consequcnccs wcrc that Pctzoldt, along with numerous allics, strcnuously advocatcd this misinterpretation until it bccamc the majoiity opinion, as it may still wdl bc today (1971).

IX

Joseph Pctzoldt, in his elation over the letters, decidcd to visit Ernst Mach in Vatcrstcttcn and havc a long discussion with him concerning the whole cjucstion of Einstcin’s theory of rclativity and its dcvelopmcnt from the special to the generał theory. Unfortunately, however, whilc his psychological timing might havc becn right, his historical timing could hardly havc becn worse. Hc planncd to make the trip in łatę July 1914, that is. during the tense days immcdiately preceding World War I when reservists had to kecp in mind the imminent likelihood of mobilization. Pctzoldt also notieed a rather cool reaction from Vaterstetten. Ludwig Mach, writing for his father, pointed out the following aspeets of the situation: “Under the present conditions you will want to return borne [to Berlin] soon. Pm sorry that you have not becn able to speak with Dr. Dingler. . . . My father is not wcil. . . .”⁰² Pctzoldt rcactcd by coming to Munich anyway, but thcrc was no one to mect him and conduct him to Vatcrstettcn. Ludwig

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