IMG66

Ernst Mach

What you say about circumfcrcncc mcasurcs and clocks is complctcly untcnable. I am talking about thc unjustifiablc transfer of propositions from thc spccial theory of rclativity to rcfcrcntial systems which arc ac-cclcratcd rcląfive to incrtial systems. Freundlich and Schlick arc complctcly right herc. According to ydur way of forming conclusions one could rcason just as wcll, that cvcry ray of light must cxtcnd in a straight linc rclativc to any rotating system etc. Your misunderstanding is quitc fundamcntal.⁸³

In other words, cvcn if Petzoldt was correct that in 1914 Ernst Mach cithcr did £avor Einstcin’s theory of relativity or Petzoldt could havc persuaded him to accept it, had hc been allowed to visit him, still, thcrc is no cvidencc that Mach cvcr abandoncd his opposition to cithcr theo-retical physics or the usc of multidimensional geometries in physics. Furthermorc, evcn if Mach was briefly carricd away, ii was only into sympathizing with or acccpting Petzoldts understanding, which Einstein considered to be a falsc understanding of thc theory of rcla-tivity, primarily bccause of Pctzoldt’s effort to “relativizc" the con-stancy of thc vclocity of lighr. If we mcan by accepting thc theory of rclativity, accepting a vcrsion compatiblc with Einstcin’s understanding of his own theory, then we are now rcady to givc a flat uncquivoc3l answer to thc leading question in this chaptcr: Did Mach finally acccpt Einstein's theory of relativity? No, he did not!

Joseph Petzoldt cvcntually faccd facts, but it was hard. Undaunted by Einsteins earlicr opposition. hc tried again in 1927, this timc to draw thc great scientist into an updated version of his earlicr posi-tivistic socicty, now callcd: The International Society for Empirical Philosophy. Einstein refused to join both bccause of its positivistic background and what he imagincd was its “empirical,” “antiihcorcticar orientation.⁸* Petzoldt finally blurtcd out in his written rcply what hc had tried not to recognize for so many ycars: “You assume that . . . [our socicty] scrvcs a 'spccial philosophical tcndcncy’. . . . But our namc has only historical and tactical significance, vcry much likc thc namc ‘relativity theory', which bccause of your insistencc on the con-stancy of natural laws is rcally an absolute theory.”⁸⁵

XIII

The rernainder of Ludwig Mach's lifc was dcvotcd to carrying out thc spccific instructions of his father with rcspect to conducting cx periments to detcrminc thc cxact, measurablc naturc of light, and com-plcting thc sccond half of The Principia of Physicul Oplics.^M “We hoped by mcans of clarifying thc problem of thc naturc of light to at least dam pen relativistic speeulation, when thc war intcrvcncd and deatli . . . ended my fathcr’s sufler i ng. . . . My father advised mc ahovc all to complctc his łreatises and to puhlish them individually and only then to conccntratc on cnlarging and arranging part II of thc Optics."*¹

Machs eldest son saw to thc 1921 publication of part I of thc Oplics, to thc 1923 publication of thc Popular Scicntific Lectura which in-cludcd scvcral prcviously unpublishcd articlcs, and to thc 1933 reprint-ing of thc Mechanies.⁸⁸ Hc also allowed unchangcd reprintings of sevcral other of his father's books. Through thc ycars, Ludwig Mach worked on rcvising and cnlarging Culturc and Mechanies, conductcd hundreds of cxpcrimcntal obscrvations of solar and celcstial light rays, and planncd a short biography of his father.⁸⁰ Serious difficulties, how-cvcr, stood in thc way of complcting part II of thc Optics. First, hc was no longcr young; in 1920 hc was fifty-two years old. Second, while lic was a skillcd invcntor and cxpcrimcntalist, his knowlcdgc of both physics and philosophy was limited. Third, thcrc wcrc serious finan-cial difFicultics which hampered efforts to buy cquipment and limited thc timc he could spend on cxpcrimcntation. And fourth. and prob-ably most important, several publishing rebuffs, a continuing serics of illncsscs and dcaths in his immediatc family, and thc apparcntly in-conclusive naturc of his cxperimental rcsults so depressed his spirits as to translatc his lingering mcntal determination into cxpcrimcntal impotcncc and sloth, occasionally broken by cvcr rarer bursts of cncrg\ and high hopes.⁰⁰

As a rcsult of thc loss of my hard-carncd fortunc in thc war I regrettabU have had to mortgage my housc. . . .^0ł

Incrcasing age, unfavorahlc living conditions, and the morę than tweKe ycar-long illncss of my wifc who died in Octobcr 1931 has ma.de every-thing morę diflicult and gnaws away at my life’s goal.¹*-

Sincc thc death of my brother in 1933 thcrc has becn no one to help mc in my cxpcrimcntal work. . .

In 1936, Robert H. Lowic, who had becn in corrcspondcnce with Ludwig Mach, led a campaign to help Machs son get back on his fcct