Whittaker and the Aether 


In 1910 the mathematician Edmund Whittaker published “A History of the Theories of Aether and Electricity”, an excellent book describing in great detail the development of field theories (including magnetism and gravity) from Descartes up to the year 1900. Fortythree years later, in 1953, Whittaker published a revised edition of this work, and added a second volume, covering the years from 1900 to 1926, including the emergence of the theories of relativity and quantum mechanics. The second volume is notable for Whittaker’s attribution of what we would call the special theory of relativity almost exclusively to Lorentz and Poincare. He describes Einstein’s 1905 paper on the subject as one which “set forth the relativity theory of Poincare and Lorentz with some amplifications, and which attracted much attention”, and he credited Einstein only with being the first to publish the correct relativistic formulas for aberration and the Doppler effect. Whittaker’s unorthodox view of Einstein’s contribution is nominally consistent with the overall theme of his book, being a history of the theories of aether. The novelty of Einstein’s interpretation was in the idea that the evident relativity of all physical phenomena transcended the properties or behavior of any substance (aether), and was instead a consequence of the structure of space and time. Whittaker was always unsympathetic to this interpretation, as is clear from his preface to the second edition: 

As everyone knows, the aether played a great part in the physics of the nineteenth century; but in the first decade of the twentieth, chiefly as a result of the failure of attempts to observe the earth's motion relative to the aether, and the acceptance of the principle that such attempts must always fail, the word 'aether' fell out of favour, and it became customary to refer to the interplanetary spaces as 'vacuous'; the vacuum being conceived as mere emptiness, having no properties except that of propagating electromagnetic waves. But with the development of quantum electrodynamics, the vacuum has come to be regarded as the seat of the 'zeropoint' oscillations of the electromagnetic field, of the 'zeropoint' fluctuations of electric charge and current, and of a 'polarisation' corresponding to a dielectric constant different from unity. It seems absurd to retain the name 'vacuum' for an entity so rich in physical properties, and the historical word 'aether' may fitly be retained. 

In view of this, it’s not surprising that Whittaker placed little value on Einstein’s contribution to special relativity, since that contribution was construed by many people as just an alternative interpretation that dispenses with the aether. Of course, since the definitive meaning of the word “aether” has never been given, the word can be taken to signify just about anything, including vacuum, so claims about the existence of “aether” are always somewhat ambiguous. (Princess Caroline once wrote to her former tutor Leibniz that “what these gentlemen call vacuum is really nothing but something which is not matter”.) Einstein acknowledged, especially from the standpoint of general relativity, that “space is endowed with physical qualities; in this sense, therefore, there exists an aether”. Despite these conciliatory statements, the choice between the words “vacuum” and “aether” seems to have (for some people) a psychological significance beyond any scientific distinction that might be intended by the words. Indeed the bare facts seem to be agreed, as we can gather from comparing Einstein’s comments (in 1920) 

The whole change in the conception of the ether which the special theory of relativity brought about consisted in taking away from the ether its last mechanical quality… This ether may not be thought of as endowed with the quality characteristic of ponderable media, as consisting of parts which may be tracked through time. The idea of motion may not be applied to it. 

with Whittaker’s conclusion of the chapter in Volume I on mechanical models of the aether (culminating in Kelvin’s vortex sponge): 

Towards the close of the nineteenth century, chiefly under the influence of Larmor, it came to be generally recognised that the aether is an immaterial medium, sui generis, not composed of identifiable elements having definite locations in absolute space… 

We see in these quotations a remarkable concordance in the conception of the aether (to the extent that we might wonder if one was influenced by the other), but a predictable disagreement as to the origin of this conception. Einstein says it was a consequence of special relativity (by which he presumably meant his own version of special relativity as described in his 1905 paper), whereas Whittaker attributes it to Larmor at the end of the nineteenth century, when, he says, “it came to be generally recognized”. However, it should be noted that the paragraph in which Whittaker describes these 19th century developments does not appear in the 1910 version of the book. Instead, the chapter on Models of the Aether in the 1910 edition ended with the discussion of Kelvin’s vortex sponge and Whittaker’s comment that “none [of the 19th century mechanical models] possesses [current tense] greater interest”. The entire subsequent paragraph, in which Whittaker declares that all of this was, by the end of the 19th century, generally recognized to have been superceded “chiefly under the influence of Larmor” in favor of an immaterial medium compatible with relativity, was not added until the 1953 edition. 

After reading Whittaker’s treatment of special relativity, we might expect him to disregard Einstein’s other contributions, but in fact we find a considerable recognition of Einstein’s role in the chapters of Volume II on the beginnings of quantum theory and on the theory of gravitation (i.e., general relativity). For example, after describing Planck’s groundbreaking work on the quantum, Whittaker writes 

The next important advance in quantum theory was made by Einstein, in the same volume of the Annalen der Physik as his papers on the Brownian motion and relativity. Einstein supposed monochromatic radiation… In December 1906 Einstein initiated a new development of quantum theory, by carrying its principles outside the domain of radiation, to which they had hitherto been confined, and applying them to the study of the specific heats of solids… A new prospect opened in 1909 when Einstein discussed the fluctuations in the energy of radiation in an enclosure which is at a given temperature T… [and so on]. 

Einstein emerges as perhaps the main innovator and contributor to the early development of quantum theory in Whittaker’s account, even surpassing Planck, so it would be inaccurate to say that Whittaker consistently downplayed Einstein. Rather it seems that Whittaker was concerned to downplay only certain aspects of Einstein’s theoretical approach, aspects which he (Whittaker) found disagreeable. All of Einstein’s ideas that can be expressed in terms of “the aether” are cited generously, but his ideas involving nonclassical models of space and time are ignored, and the developments in those areas are carefully traced back through alternative sources to individuals who worked in terms of “the aether”. In other words, Whittaker was at pains to show that none of the successful results of modern physics owed their existence to ideas concerning the nonGalilean structure of space and time. (In this respect Whittaker followed Poincare, who often mentioned Einstein is connection with statistical mechanics and quantum theory but never in connection with relativity. The Nobel prize committee adopted the same attitude.) 

Even in his extensive treatment of Einstein’s theory of gravitation, Whittaker includes a discussion of the alternative view put forward by his fellow mathematician Alfred North Whitehead in 1920: 

Whitehead … postulated two fields of natural relations, one of them (namely space and time relations) being isotropic, universally uniform and not conditioned by physical circumstances; the other comprising the physical relations expressed by laws of nature, which are contingent… Whitehead's doctrine, though completely different from Einstein’s in its formulation, may be described very loosely as fitting the Einsteinian laws into a flat spacetime; and no practicable observational test has hitherto been suggested for discriminating between the two theories. 

However, this alternative view, while supportive of Whittaker’s thesis, was not enough to completely eclipse Einstein’s relativistic theory of spacetime curvature, because it was, after all, just “fitting the Einsteinian laws” into flat spacetime. If this were the whole story, a reader might be justified in thinking that the original inspiration and source of the theory was Einstein’s conception of relativistic spacetime – a conclusion that Whittaker wanted to avoid. To offset this, the chapter on gravitation includes a couple of interesting assertions about the origins of the ideas in general relativity. He begins by saying 

From 1904 onwards the Newtonian law of gravitation was examined in the light of the relativity theory of Poincare and Lorentz. This was done first by Poincare, who pointed out that if relativity theory were true, gravity must be propagated with the speed of light, and who showed that this supposition was not contradicted by the results of observation, as Laplace had supposed it to be. He suggested modifications of the Newtonian formula, which were afterwards discussed and further developed by H. Minkowski and by W. de Sitter. It was found that relativity theory would require secular motions of the perihelia of the planets, which however would be of appreciable amount only in the case of Mercury, and even in that case not great enough to account for the observed anomalous motion. 

This is fair enough, in keeping with Whittaker’s general outlook, but then, rather surprisingly, Whittaker informs us that the key idea of general relativity (the idea which Einstein called “the happiest thought of my life”) was actually due to Planck 

In 1907 Planck broke new ground. It had been established by the careful experiments of R. v. Eotvos that inertial mass (which determines the acceleration of a body under the action of a given force) and gravitational mass (which determines the gravitational forces between the body and other bodies) are always exactly equal, which indicates that the gravitational properties of a body are essentially of the same nature as its inertial properties. Now, said Planck, all energy has inertial properties, and therefore all energy must gravitate. Six months later Einstein published a memoir in which he introduced what he later called the Principle of Equivalence… 

It’s debatable (to say the least) that the results of Eotvos’s experiments were seen as indicating that the gravitational properties of a body are of the same nature as its inertial properties… in fact, it’s difficult to conceive of what that could mean outside of the context of curved spacetime. But setting this aside, the implication that Planck articulated the equivalence principle early in 1907 is quite startling. The publication cited by Whittaker is “Berl. Sitz., 13 June 1907, p. 542, specially at page 544”. I have not read this reference myself, but Roberto Torretti translates what he believes is the relevant passage from page 544 of Planck’s paper as follows 

The thermic radiation in a perfectly void cavity surrounded by reflecting walls certainly possesses inertial mass. Does it also have ponderable mass? If, as it seems most likely, this question is to be answered in the negative, the generally assumed identity of inertial and ponderable mass, confirmed hitherto by all experiments, is evidently destroyed. 

If this quote is accurate  and assuming it’s representative of what Planck’s paper says on the subject  then Whittaker’s reliability must be seriously questioned. It appears that, as Torretti comments, “In his eagerness to detract from Einstein’s originality, Whittaker quotes the above passage as saying the opposite of what we have just read…”. Were this some obscure or insignificant point, we might be willing to overlook it as an honest mistake, but to misattribute the origin of the equivalence principle in a historical review of the relativistic theory of gravitation seems hard to excuse. 

Continuing his review of the development of theories of gravity in the early twentieth century, Whittaker comments on Einstein’s 1911 paper (including the argument that rays of light should be deflected by a gravitational field), and then mentions the theories of Abraham, Nordstrom, and Mie. At this point we might expect the focus to return to Einstein, but instead we learn that 

The next advance owed much to a paper that had been written in 1909 by Harry Bateman (18821946). At any place in the earth's gravitational field, take moving rectangular axes x^{1}, x^{2}, x^{3} and a measure of time x^{0}, such that these axes constitute an inertial system A… When we move to a distant place in a field of force, e.g. if we move to the antipodes in the earth's gravitational field, although we can here again find axes (say B) which are inertial, a framework B does not move with uniform velocity relative to a framework A (in fact the two frameworks are in accelerated motion relative to each other), so the relation between two inertial frameworks which holds in the relativity theory of Poincare and Lorentz [“in the free aether”] does not hold when a gravitational field is present… Instead of this, we can now find at every place in the field a local framework of inertial axes… Let x^{0}, x^{1}, x^{2}, x^{3} now be any coordinates specifying position and time over the whole field. Then at each place… we have 

_{} 

The vanishing of this form … is now the condition that a luminous disturbance originating at the spacetime point (x^{0}, x^{l}, x^{2}, x^{3}) should arrive at the spacetime point (x^{0} + dx^{0}, x^{l} + dx^{1}, x^{2} + dx^{2}, x^{3} + dx^{3}). The form (1) must be invariant for all transformations of the coordinates (x^{0}, x^{1}, x^{2}, x^{3}); and its coefficients g_{pq}, which are functions of (x^{0}, x^{1}, x^{2}, x^{3}), are characteristic of the field. Bateman realised the connection of his work with the tensorcalculus of Ricci and LeviCivita: in fact, since (dx^{0}, dx^{1}, dx^{2}, dx^{3}) is a contravariant vector, it follows from the invariance of the quadratic differential form that the set of the g_{pq} is a symmetric covariant tensor of rank 2… Bateman’s ideas were carried over into a more profound treatment of the problem of gravitation in the second half of the year 1913 by Einstein… 

So, once again Whittaker finds that Einstein has been anticipated by work done in the context of the aether. In a footnote Whittaker acknowledges that “These ideas were applied by Bateman in order to investigate a scheme of fundamental electromagnetic equations which are not altered by very general transformations”, which suggests that Bateman was not actually writing about gravitation at all. In addition, when Whittaker says Bateman “realized the connection of his work with the tensorcalculus of Ricci and LeviCivita”, and goes on to describe some results from the latter, it’s unclear if these remarks are intended to be representative of Bateman’s 1909 paper (which actually appeared in 1910), or are Whitaker’s own ex post facto extrapolations. There are many such passages in Whittaker’s History, i.e., passages seemingly crafted to suggest an attribution without actually claiming it. For example, most readers of the above quote would infer that Bateman’s 1910 paper discusses tensor calculus and explicitly identifies the metric coefficients as comprising a covariant tensor of the second rank… even though the quote doesn’t actually claim this. The comments on tensor calculus are merely placed in juxtaposition with the reference to Bateman’s paper, verbally linked by the assertion that Bateman “realized the connection”. Overall, Whittaker’s account seems to be not so much a paraphrase of Bateman as an attempt to frame Bateman’s work in a context that makes it most closely resemble an anticipation of Einstein’s subsequent theory of general relativity. Furthermore, it is far from clear what basis Whittaker has for saying “the next advance owed much” to Bateman’s paper. While it is true that, at least by 1917, Einstein was familiar with Bateman’s 1910 paper (as we can see from his correspondence with Felix Klein), there is no evidence (to my knowledge) that either Einstein or Grossmann had read Bateman’s paper prior to 1916, let alone that it influenced their thinking about gravitation. The historical record suggests that Einstein and Grossmann relied on the works of Gauss, Riemann, Ricci, and LeviCivita for their understanding of the absolute differential calculus, and on the works of Minkowski for the spacetime formalism. Also, Einstein himself had already proposed in 1907 the equivalence principle as the basis of a gravitation theory, and even Whittaker credits Einstein with having introduced the idea of the metric coefficients as the gravitational potentials (see below), so it isn’t clear precisely what advance Whittaker means to attribute to Bateman. 

Coincidentally, Harry Bateman had been a student of Whittaker’s at Cambridge, and Bateman’s early work involved extending the applicability of a technique originated by Whittaker for solving partial differential equations. When Bateman died in 1946, Whittaker was consulted as to who should edit his former student’s collected papers. This personal relationship makes it perhaps less surprising that Whittaker should be so mindful of Bateman’s activities, and so protective of his priority. This is most clearly seen in Whittaker’s brief description of the work of Einstein and Grossmann, which he not only prefaced with the phrase “Bateman’s ideas were carried over”, but twice interrupted to insert the gratuitous comments “making a step analogous to that in Bateman’s paper” and “As with Bateman…”. These three comments, all fit into a single paragraph, give the impression of Whittaker was particularly keen on establishing some kind of priority for his former student. Judging from a letter to the editor of Philosophical Magazine dated 10 August 1918 (appearing in 1919, sixth series, no. 37, p. 219), Bateman himself seems to have felt that his contribution to “general relativity” was not sufficiently appreciated: 

The appearance of Dr. Silberstein's recent article on 'General Relativity without the Equivalence Hypothesis' encourages me to restate my own views on the subject. I am perhaps entitled to do this as my work on the subject of General Relativity was published before that of Einstein and Kottler, and appears to have been overlooked by recent writers. 

It’s interesting that in the summer of 1918, at the climax of the first world war, scientists throughout the world already appreciated the importance of the general theory of relativity, a theory developed by a German scientist in Berlin in 1915. 

Setting aside Whittaker’s interest in Bateman, the real object of his agenda can be seen in his treatment of William Kingdon Clifford. If Whittaker’s aim was simply to downplay Einstein’s originality whenever possible, we would expect him to make much of Clifford’s writings in the 1870s on “the space theory of matter”, such as 

Riemann has shown that… there are different kinds of space…and we can only find out by experience to which of these kinds the space in which we live belongs… I hold that… variation of the curvature of space is what really happens in that phenomenon which we call the motion of matter, whether ponderable or etherial… in the physical world nothing else takes place but this variation 

However, Whittaker mentions Clifford only once, in a footnote to the statement that the path of a free material particle in Einstein’s theory can be described in geometrical language as a geodesic in fourdimensional space with a given metric. The footnote says “A theory that matter consists in ‘crinkles’ of space had been published by W. K. Clifford in 1870”. Here Whittaker seems, if anything, to be downplaying a predecessor of Einstein’s, and in the main text he continues with an appreciation of Einstein’s insight: 

This was a tremendous innovation, because it implied the abandonment of the timehonoured belief that a gravitational field can be specified by a single scalar potential function; instead, it proposed to specify the gravitational field by the ten functions g_{pq} which could now be spoken of as the gravitational potentials. 

This (again) supports the view that Whittaker’s aim was not to diminish the value or importance of Einstein’s contributions, but to denigrate the nonEuclidean geometrical interpretation, which explains why Whittaker had no interest at all in Clifford (who actually implied that the appearance of etherial matter was really just an artifact of curved spacetime, precisely the opposite of Whittaker’s thesis), and why he was careful to qualify the term “geodesic” as just a linguistic analogy, and why he regarded the essential innovation of Einstein’s theory to be the shift from a single scalar potential to a field with ten potentials, rather than the interpretation of gravity as a consequence of the geometry of spacetime. 

Incidentally, although the first edition of Whittaker’s book, published in 1910, ostensibly covers the time period only up to the year 1900, the final section includes an interesting survey of “recent developments”, including the work done by Lorentz and others on “the principle of relativity”. In addition to making note of Minkowski’s paper on space and time, Whittaker also twice mentioned in footnotes the (then) little known Albert Einstein in connection with Lorentz’s efforts to formulate all the laws of electrodynamics such as to be covariant under the Lorentz transformation to all orders in v/c. The footnote stated 

* Lorentz' work was completed in respect to the formulae which connect p_{i}, v_{i}, with p, v, by Einstein, Ann. d. Phys., xvii (1905). 

This was far more than Whittaker would concede to Einstein when writing the second edition over 40 years later. Even more interesting is the comment a few pages further on, where Whittaker summarizes the results in this area: 

The equations of motion of the aether are the same with respect to both sets of coordinates, and therefore neither can claim to possess the only property which could confer a primacy namely, an absolute relation to the aether.* 
* This was first clearly expressed by Einstein, Ann. d. Phys. xvii (1905). 

In contrast, Poincare was not mentioned in Whittaker’s 1910 discussion of relativity (although he was credited with having been among the first to attribute mechanical momentum to energy). However, by the time Whitaker wrote the second edition, he seems to have become more acquainted with Poincare’s writings on the principle of relativity, and evidently concluded that it was Poincare rather than Einstein who “first clearly expressed” the relativity of physical laws and, hence, the complete symmetry between relatively moving systems of reference. 

The role of Max Born in this episode is intriguing. Of course Born was an ardent admirer and defender of Einstein’s relativity, and was in a good position to assess the significance of Einstein’s contribution, because he (Born) had already become acquainted with the relativistic ideas of Lorentz, Minkowski, and others, prior to reading Einstein’s paper for the first time in 1907. Born wrote 

A long time before I read Einstein’s famous 1905 paper, I knew the formal mathematical side of the special theory of relativity through my teacher Hermann Minkowski. Even so, Einstein’s paper was a revelation to me which had a stronger influence on my thinking than any other scientific experience… Einstein’s simple consideration, by which he disclosed the epistemological root of the problem… made an enormous impression, and I think it right that the principle of relativity is connected with his name, though Lorentz and Poincare should not be forgotten. 

Born had even written a popular book on “Einstein’s Theory of Relativity”. However, it is also true that Born was deeply hurt by Einstein’s rejection – seemingly on purely philosophical grounds – of the probabilistic formulation of quantum mechanics, which of course was seen as Born’s key contribution to science. When the Nazis came to power in Germany, Born had emigrated to Britain, eventually settling in Scotland, taking a professorship at Edinburgh, where Whittaker was then Professor Emeritus. Born and Whittaker became close friends, and Born regarded Whittaker’s book as “a brilliant and historic philosophical work which I found extremely useful in my early years”. Presumably he was referring to the first volume published in 1910, although even this seems rather late to be called Born’s early years. Elsewhere Born wrote that Whittaker’s book “was already in use… in my student times”, which seems odd, considering that Born received his doctorate in 1907, and the first edition of Whittaker’s book was published in 1910. 

Regarding the second volume of Whittaker’s book, and the downplaying of Einstein’s contribution to special relativity, it’s worth remembering that Born himself had written about the somewhat misleading impression of novelty given by Einstein’s 1905 paper on special relativity. After summarizing the prior writings of Poincare and Lorentz on the subject, Born wrote 

The striking point is that [Einstein’s 1905 paper On the Electrodynamics of Moving Bodies] contains not a single reference to previous literature. It gives you the impression of quite a new venture. But that is, of course, as I have tried to explain, not true. 

This, of course, is precisely the conclusion that Whittaker reached… after long discussions of the subject with Born. As mentioned above, Born was well positioned to appraise the importance of Einstein’s work in the context of the previous writings of Poincare and Lorentz. He later recalled that 

I was at that time [1905] in Gottingen and well acquainted with the difficulties and puzzles encountered in the study of electromagnetic and optical phenomena in moving bodies, which we thoroughly discussed in a seminar held by Hilbert and Minkowski. We studied the recent papers by Lorentz and Poincare, we discussed the contraction hypothesis brought forward by Lorentz and Fitzgerald, and we knew the transformations now known under Lorentz’s name. Minkowski was already working on his fourdimensional representation of space and time, published in 1907, which became later the standard method in fundamental physics. 

Interestingly, this suggests that Minkowski had already begun to formulate his ideas on the subject even before becoming acquainted with Einstein’s paper. In any case, Born clearly knew more than did most scientists (including Whittaker in 1910) about the various sources and contributors to the development of special relativity, and he surely discussed the matter with Whittaker. It may even be the case that Born’s recollections helped to shape Whittaker’s later view of the subject. Soon after the second volume of Whittaker’s book appeared in 1953 Born wrote to Einstein 

Whittaker, the old mathematician, who lives here as Professor Emeritus and is a good friend of mine, has written a new edition of his old book History of the Theory of the Ether, of which the second volume has already been published. Among other things it contains a history of the theory of relativity which is peculiar in that Lorentz and Poincare are credited with its discovery while your papers are treated as less important. Although the book originated in Edinburgh, I am not really afraid you will think that I could be behind it. As a matter of fact I have done everything I could during the last three years to dissuade Whittaker from carrying out his plan, which he had already cherished for a long time and loved to talk about. I reread the originals of some of the old papers, particularly some rather offbeat ones by Poincare, and have given Whittaker translations of German papers (for example, I translated many pages of Pauli's Encyclopaedia article into English … in order to make it easier for Whittaker to form an opinion). But all in vain. He insisted that everything of importance had already been said by Poincare, and that Lorentz quite plainly had the physical interpretation. 

This private account gives a slightly different impression of events than one would gather from Born’s essay in his book ‘Physics in My Generation’, in which he writes 

In regard to [Poincare’s] work I refer to the excellent book by Sir Edmund Whittaker, A History of the Theories of Aether and Electricity, which was already in use as a guide in my student times. It has now been completely rewritten. The second volume of the new edition deals with 'The Modem Theories, 19001926'; there you can find quotations from Poincare’s papers, some of which I have looked up in the original. They show that as early as 1899 he regarded it as very probable that absolute motion is indetectable in principle and that no ether exists. He formulated the same ideas in a more precise form, though without any mathematics, in a lecture given in 1904 … he predicted the rise of a new mechanics which will be characterized above all by the rule, that no velocity can exceed the velocity of light. Whittaker was so impressed by these statements that he gave to the relevant chapter in his book the title 'The Relativity Theory of Poincare and Lorentz.' Einstein’s contributions appear there as being of minor importance… I have tried to form an opinion about this question from my own recollections and with the help of a few publications available to me… 

This account gives the impression that Born’s attention was drawn to Poincare’s papers by Whittaker, rather than the other way around, in contradiction to Born’s recollection of having read Poincare’s papers in his student days before reading Einstein’s paper, and that Born tried to “form an opinion about this question” only after the appearance of Whittaker’s second volume, whereas the letter to Einstein explains that Born had discussed the matter with Whittaker for at least three years prior to publication of the book, and indeed had actively participated in Whittaker’s research by providing translations of some early papers. In his “My Generation” essay Born’s conclusion is rather murky. He recounts several of Poincare’s statements (pre1905) that sound very much like special relativity, and then concludes his discussion of the priority question by saying 

Does this mean that Poincare knew all this before Einstein? It is possible, but the strange thing is that this lecture definitely gives you the impression that he is recording Lorentz’s work… On the other hand, Lorentz himself never claimed to be the author of the principle of relativity… 

This is hardly a ringing endorsement of Einstein’s claim to priority over Poincare. It can just as well be taken to indicate that Poincare was overly deferential to Lorentz. Born was well aware, from firsthand discussions, “how skeptical Lorentz was [of special relativity] and how long it took him to become a relativist”. In fact, Born wrote that 

When I visited Lorentz a few years before his death, his skepticism had not changed…he probably never became a relativist at all, and only paid lipservice to Einstein at times in order to avoid argument. 

So it’s clear that Born did not regard Lorentz as the founder of special relativity, but his view regarding Poincare’s claim to priority is (in my opinion) less clear. Returning to Born’s letter of explanation to Einstein, it’s interesting that he seems almost to be trying to provoke Einstein over the matter. He writes 

I am annoyed about this, for [Whittaker] is considered a great authority in the English speaking countries and many people are going to believe him. 

Was it really necessary to make such a galling prediction? He then goes on to state the case for the suspicion that he (Born) was somehow complicit. 

It is particularly unpleasant in my opinion that [Whittaker] has woven all sorts of personal information into his account of quantum mechanics and that my part in it is extolled. Many people may now think (even if you do not) that I played rather an ugly role in this business. After all, it is common knowledge that you and I do not see eye to eye over the question of determinism. What is more, I have written a small article which is shortly to appear in which I give a theoretical interpretation of an idea of Freundlich's about stellar red shift, which could, if correct, cause difficulties for the relativistic interpretation. 

It seems as if Born used the appearance of Whittaker’s book as an occasion to review with Einstein all their disagreements, and that at this stage Born was entertaining ideas that could “cause difficulties” for relativity. Regarding the stellar red shift, Born says elsewhere that 

My report on Freundlich’s doubts about the astronomical confirmation of the theory of relativity left Einstein quite cold. He considered the logical foundations of his theory of gravitation to be unshakeable. The latest observations have proved him right. 

Notice that he says here he was simply reporting “Freundlich’s doubts”, whereas his letter to Einstein says that he (Born) himself has proposed a theoretical interpretation of Freundlich’s ideas which could cause difficulties for relativity. Born concluded his account of the Whittaker affair in his letter to Einstein by saying “Well, I had to write this and get it off my chest”. Einstein’s reply, written in ill health less than two years before his death, is wonderfully witty and deft, managing to convey a serene disinterest in Whittaker’s provocative thesis, while at the same time parrying Born’s jab at determinism and weaving a subtle correspondence between the miserliness of priority disputes and the reputation of the Scotch people for parsimony, immediately juxtaposing this with a tacit (and rather brutal) comment on Born’s decision to return to Germany. 

Don’t lose any sleep over your friend's book. Everybody does what he considers right or, in deterministic terms, what he has to do. If he manages to convince others, that is their own affair. I myself have certainly found satisfaction in my efforts, but I would not consider it sensible to defend the results of my work as being my own 'property', as some old miser might defend the few coppers he had laboriously scraped together. I do not hold anything against him, nor of course against you. After all, I do not need to read the thing. 

If anyone can be held responsible for the fact that you are migrating back to the land of the massmurderers of our kinsmen, it is certainly your adopted fatherland [i.e., Whittaker’s Scotland] — universally notorious for its parsimony. But then we know only too well that the collective conscience is a miserable little plant which is always most likely to wither just when it is needed most. 

Born seems to have been oblivious to the undertones in this letter. He comments simply that 

Einstein’s reaction to my complaint about Whittaker’s account of the theory of relativity proves his utter indifference to fame and glory. 
