Relativity Priority Dispute

Issue in science history

Ah, the perennial human obsession with assigning singular credit, even for ideas that clearly simmered in the collective consciousness of a generation. This article, then, delves into the rather persistent squabble surrounding the genesis of special relativity , a foundational pillar of modern physics. For those with a penchant for similar academic fisticuffs, the General relativity priority dispute offers another fascinating, if equally tiresome, exhibition of intellectual jostling.

It’s a well-trodden path in the annals of scientific discourse: a brilliant mind, Albert Einstein , presents groundbreaking theories—special relativity and general relativity —in publications that, with a certain audacious elegance, contained either no formal references to prior works or, at best, a rather select handful. For special relativity , his acknowledgments notably gravitated towards the foundational contributions of Henri Poincaré and Hendrik Lorentz . Later, for general relativity , credits were sparingly extended to David Hilbert , Carl F. Gauss , Bernhard Riemann , and Ernst Mach . Following this seemingly minimalist approach to citation, it was almost inevitable that claims would surface, asserting that these revolutionary theories had been, in whole or in part, formulated by others long before Einstein’s pronouncements. The crux of the matter, therefore, boils down to the rather delicate question of how much credit, based on the principle of scientific priority , should be apportioned to Einstein and to the various other luminous figures who were undeniably circling similar conceptual territory.

The finer points of this historical entanglement have drawn considerable scrutiny from various scholars, who have meticulously dissected the work of Einstein, Poincaré, and Lorentz leading up to the seminal publications of 1905. The questions they pose are not merely academic footnotes but cut to the heart of scientific discovery and influence: To what precise extent was Einstein acquainted with Poincaré’s extensive body of work? Was he intimately familiar with Lorentz’s pivotal 1904 paper, or perhaps a comprehensive review of it? And how diligently did Einstein track the intellectual currents and cutting-edge research being conducted by his contemporaries in the physics community? What we do know, unequivocally, is that Einstein had read Poincaré’s 1902 paper [Poi02]. However, the full scope of his familiarity with Poincaré’s other prolific output in that pivotal year of 1905 remains shrouded in historical ambiguity. A year later, in 1906, we have direct evidence that Einstein was aware of [Poi00], as he explicitly quoted it in his own work [Ein06]. Meanwhile, Lorentz’s 1904 paper [Lor04] had already introduced the transformations that would forever bear his name, appearing prominently in the prestigious Annalen der Physik . Some historical narratives, often romanticized, suggest that Einstein toiled in a state of relative isolation in 1905, with notoriously restricted access to the broader physics literature of the day. A convenient narrative, perhaps, but one that warrants closer examination, as we shall see.

Background

In the rather contentious chronicle of special relativity , the names that inevitably surface in any serious discussion about the distribution of credit are, almost without fail, Albert Einstein , Hendrik Lorentz , Henri Poincaré , and, a little later, Hermann Minkowski . One might think this is a sufficiently complex quartet, but of course, the historical record insists on acknowledging a veritable legion of other scientists. These individuals are cited either for having made significant anticipations of certain aspects of the theory – perhaps a glimmer of an idea, a mathematical fragment – or for their subsequent contributions to its development and elaboration. The list is extensive, a testament to the fact that scientific progress is rarely a solitary endeavor: Woldemar Voigt , August Föppl , Joseph Larmor , Emil Cohn , Friedrich Hasenöhrl , Max Planck , Max von Laue , Gilbert Newton Lewis , and Richard Chase Tolman , among others, all made their mark on the evolving landscape of electrodynamics and nascent relativity.

Beyond these acknowledged contributors, the murky waters of historical polemics throw up more dubious claims. Take, for instance, the alleged contributions of Olinto De Pretto , who, according to certain mathematical scholars, did not create relativity but merely had the distinction of being the first to employ a specific equation. [1] Such claims often feel like grasping at straws in the shadow of giants. Similarly, Einstein’s first wife, Mileva Marić , found herself featured in a PBS bibliography that sensationally suggested she made uncredited contributions to his work. The network, with a rather telling backtrack, later conceded that the show was “factually flawed and ultimately misleading,” and serious scholars have since firmly established these claims as having no foundation. [2] One must wonder about the motivations behind such persistent, if unsupported, narratives.

Perhaps the most prominent voice in the revisionist camp was E. T. Whittaker , who, in his influential 1953 work, History of the theories of ether and electricity, controversially declared relativity to be the creation of Poincaré and Lorentz, allocating minimal importance to Einstein’s papers. [3] A bold assertion, certainly, and one that ignited a firestorm in the historical community.

However, the overwhelming consensus among the vast majority of historians of science, including luminaries such as Gerald Holton , Arthur I. Miller , Abraham Pais , John Stachel , and Olivier Darrigol, diverges sharply from Whittaker’s narrative. They readily acknowledge that Lorentz and Poincaré indeed laid much of the mathematical groundwork for special relativity ; in fact, many contemporary scientists initially referred to it as the “Lorentz–Einstein theory.” Yet, these scholars emphatically argue that it was Einstein, and Einstein alone, who took the truly revolutionary conceptual leap. He systematically eliminated the classical ether from physics, rendering it superfluous, and fundamentally demonstrated the relativity of space and time not as a mathematical artifact, but as an inherent property of the universe. They further contend that while Poincaré explored the relativity of space and time in his more philosophical writings, his actual physical papers, much like Lorentz’s, clung to the concept of the ether as a privileged, albeit perfectly undetectable, frame of reference. Both continued to draw a distinction between “real” lengths and times, measured by observers at rest within this hypothetical aether, and “apparent” lengths and times, measured by observers in motion relative to it. [B 1] [B 2] [B 3] [B 4] [B 5]

Olivier Darrigol, with a characteristic precision that cuts through the fog of historical debate, offers a particularly illuminating summary:

Most of the components of Einstein’s paper appeared in others’ anterior works on the electrodynamics of moving bodies. Poincaré and Alfred Bucherer had the relativity principle. Lorentz and Larmor had most of the Lorentz transformations, Poincaré had them all. Cohn and Bucherer rejected the ether. Poincaré, Cohn, and Abraham had a physical interpretation of Lorentz’s local time. Larmor and Cohn alluded to the dilation of time. Lorentz and Poincaré had the relativistic dynamics of the electron. None of these authors, however, dared to reform the concepts of space and time. None of them imagined a new kinematics based on two postulates. None of them derived the Lorentz transformations on this basis. None of them fully understood the physical implications of these transformations. It all was Einstein’s unique feat. [B 6]

This summary, delivered with the blunt force of an inconvenient truth, underscores the critical distinction: while the ingredients were certainly present, it was Einstein who assembled them into a coherent, fundamentally new theoretical framework, daring to challenge the very fabric of reality as understood at the time.

Undisputed facts

Despite the academic squabbles and the persistent attempts to re-apportion credit, a core set of facts surrounding the History of special relativity and Lorentz ether theory remains universally acknowledged and forms the bedrock of any informed discussion:

• Poincaré’s Early Musings on the Ether (1889, 1902): In 1889, in [Poi89], Henri Poincaré articulated a rather prescient argument: if the ether were indeed unobservable, its very existence would devolve into a purely metaphysical question. He went so far as to suggest that, one day, the concept of the ether might simply be discarded as utterly useless. A remarkably forward-thinking statement, yet, in the very same book (Chapter 10), he pragmatically considered the ether a “convenient hypothesis” and continued to employ the concept in his later works, notably in 1908 ([Poi08], Book 3) and 1912 ([Poi13], Chapter 6). This highlights a subtle, yet crucial, tension in his thought: a philosophical inclination towards discarding the ether, juxtaposed with a practical adherence to its utility within existing physical models. The human mind, ever so fond of its comforts.
• Poincaré’s Principle of Relative Motion (1895, 1900, 1904): By 1895, Poincaré was already arguing, with considerable foresight citation needed , that experimental outcomes, such as those from the famous Michelson–Morley experiment , strongly indicated the impossibility of detecting the absolute motion of matter or its relative motion with respect to the ether. In 1900 [Poi00], he formalized this insight into what he termed the “Principle of Relative Motion,” asserting that the laws of movement must be identical across all inertial frames . He also used alternative phrases like “relativity of space” and “principle of relativity.” [4] This principle was further expanded in 1904, where he declared: “The principle of relativity, according to which the laws of physical phenomena must be the same for a stationary observer as for one carried along in a uniform motion of translation, so that we have no means, and can have none, of determining whether or not we are being carried along in such a motion.” However, ever the cautious empiricist, he appended a significant caveat: we cannot yet definitively know if this principle is ultimately true, but it is certainly fruitful to explore its implications.
• Poincaré’s Mass-Energy Equivalence (1900): In 1900 ([Poi00]), Poincaré published a paper where he conceptualized radiation as a “fictitious fluid” possessing an equivalent mass, denoted as $m_r = E/c^2$. This interpretation was directly derived from Lorentz’s ’theory of electrons ’, which itself incorporated Maxwell ’s concept of radiation pressure. While a significant step towards the famous equation, it was rooted in an existing theoretical framework rather than a radical re-evaluation of fundamental principles.
• Poincaré’s Clock Synchronization (1900, 1904, 1902): Poincaré described a method for synchronizing clocks that were at rest relative to one another, first in [Poi00] and then again in [Poi04]. This procedure revealed a profound implication: two events deemed simultaneous in one frame of reference would not necessarily be simultaneous in another. This concept bears a striking resemblance to the synchronization procedure later put forth by Einstein. [5] Yet, a critical distinction persisted: Poincaré maintained a clear division between the “local” or “apparent” time measured by moving clocks and the “true” time of clocks at rest within the ether. Furthermore, in [Poi02], he reiterated his argument that “some day, no doubt, the ether will be thrown aside as useless,” a statement that, again, demonstrates his intellectual struggle with the prevailing paradigm.
• Lorentz’s 1904 Transformations: Lorentz’s paper [Lor04] , which contained the now-famous transformations that bear his name, was published in 1904. These mathematical transformations were a crucial, indeed indispensable, component of what would become special relativity .
• Einstein’s Derivation and the Elimination of the Ether (1905): In his monumental 1905 paper [Ein05c], Albert Einstein elegantly derived the Lorentz equations by positing two fundamental principles: the constancy of the velocity of light and the relativity principle. He was the first to assert that these two principles, coupled with standard assumptions about the homogeneity and isotropy of space, were sufficient to construct the entire theory—a truly audacious conceptual leap, detailed further in the Postulates of special relativity . He stated, with characteristic clarity: “The introduction of a luminiferous ether will prove to be superfluous inasmuch as the view here to be developed will not require an absolutely stationary space provided with special properties, nor assign a velocity vector to a point of the empty space in which electromagnetic processes take place.” Notably, Einstein’s Elektrodynamik paper [Ein05c] contained no formal references to other literature, a point that has fueled much of the subsequent debate. It did, however, acknowledge in §9, part II, that its results aligned with Lorentz’s electrodynamics. Poincaré, despite his substantial contributions, was conspicuously absent from this paper, though he would be formally cited by Einstein in a subsequent paper on special relativity the following year.
• Einstein’s General Mass-Energy Relationship (1905): In 1905, Einstein was also the first to propose that when any material body emitted or lost energy (whether as radiation or heat) of an amount $\Delta E$, its mass would correspondingly decrease by the amount $\Delta E/c^2$. [6] This was not merely about radiation, but a general principle connecting mass and energy, which was a profound extension of prior work.
• Minkowski’s Spacetime Formulation (1907): In 1907, Hermann Minkowski provided a geometrically elegant reinterpretation of special relativity . He demonstrated that the theory could be beautifully described using a four-dimensional spacetime continuum, seamlessly combining the single dimension of time with the three dimensions of space. This mathematical framework transformed the understanding of relativity, providing it with a deeper, more unified structure.
• Einstein’s Later Ether Concept (1920): In 1920, Einstein revisited the concept of an ether. [7] [8] However, this was a fundamentally different construct from the classical, stationary, luminiferous ether. His later conception was an ether without a state of motion, a geometric field that imbued space with properties, rather than a mechanical medium. This nuance is often lost in simplified accounts, but it highlights Einstein’s evolving, rather than regressive, understanding.

Comments by Lorentz, Poincaré, and Einstein

The primary architects of the theory, or at least its most prominent intellectual progenitors, offered their own perspectives on the intricate web of discovery, often with a humility that belied the monumental nature of their work.

Lorentz

Hendrik Lorentz , a figure of immense stature and intellectual integrity, articulated his appreciation for Poincaré’s Palermo paper (1906) [10] on relativity in a paper written in 1914 and published in 1921. [9] His words are particularly telling:

I did not indicate the transformation which suits best. That was done by Poincaré and then by Mr. Einstein and Minkowski. […] Because I had not thought of the direct way which led there, and because I had the idea that there is an essential difference between systems x, y, z, t and x′, y′, z′, t′. In one we use – such was my thought – coordinate axes which have a fixed position in the aether and which we can call “true” time; in the other system, on the contrary, we would deal with simple auxiliary quantities whose introduction is only a mathematical artifice. […] I did not establish the principle of relativity as rigorously and universally true. Poincaré, on the contrary, obtained a perfect invariance of the equations of electrodynamics, and he formulated the “postulate of relativity”, terms which he was the first to employ. […] Let us add that by correcting the imperfections of my work he never reproached me for them.

This excerpt reveals Lorentz’s candid self-assessment: he recognized his own limitation in not fully embracing the conceptual equivalence of the transformed coordinates, clinging instead to the notion of a “true” time in the ether. He explicitly credited Poincaré with the rigorous formulation of the “postulate of relativity.” However, a 1916 reprint of his seminal work, The theory of electrons, included notes (penned in 1909 and 1915) where Lorentz further elaborated on the distinctions between his findings and Einstein’s: [11]

[p. 230]: the chief difference [is] that Einstein simply postulates what we have deduced, with some difficulty and not altogether satisfactorily, from the fundamental equations of the electromagnetic field. [p. 321]: The chief cause of my failure was my clinging to the idea that the variable t only can be considered as the true time and that my local time t′ must be regarded as no more than an auxiliary mathematical quantity. In Einstein’s theory, on the contrary, t′ plays the same part as t; if we want to describe phenomena in terms of x′, y′, z′, t′ we must work with these variables exactly as we could do with x, y, z, t.

Here, Lorentz precisely pinpointed the conceptual chasm: Einstein’s audacious postulation versus his own laborious deduction, and more critically, Einstein’s revolutionary reinterpretation of “local time” as universally valid “time,” effectively dismantling the privileged status of the ether-bound clock. Martin Janssen offers a compelling hypothesis for why Lorentz, in this book, primarily mentioned Einstein and not Poincaré in connection with light-signal synchronization, the reciprocity of the Lorentz transformation , and the relativistic transformation law for charge density: [B 7]

[p.90]: My guess is that it has to do with the fact that Einstein made the physical interpretation of the Lorentz transformation the basis for a remarkably clear and simple discussion of the electrodynamics of moving bodies, whereas Poincaré’s remarks on the physical interpretation of Lorentz transformed quantities may have struck Lorentz as inconsequential philosophical asides in expositions that otherwise closely followed his own. I also have a sense that Lorentz found Einstein’s physically very intuitive approach more appealing than Poincaré’s rather abstract but mathematically more elegant approach.

This suggests that while Poincaré’s mathematical elegance was undeniable, Einstein’s physical interpretation resonated more deeply with Lorentz, who was perhaps less inclined towards philosophical abstractions in his core physics work. This sentiment was echoed even later, at a 1927 conference on the Michelson–Morley experiment , where both Lorentz and Michelson were present. When Michelson rather generously suggested that Lorentz was the true initiator of the theory of relativity, Lorentz, with characteristic intellectual honesty, replied: [12]

I considered my time transformation only as a heuristic working hypothesis. So the theory of relativity is really solely Einstein’s work. And there can be no doubt that he would have conceived it even if the work of all his predecessors in the theory of this field had not been done at all. His work is in this respect independent of the previous theories.

A rather definitive statement from one of the primary contenders, effectively ceding the conceptual crown.

Poincaré

Henri Poincaré , in contrast to Lorentz’s self-effacing acknowledgments, consistently attributed the development of the new mechanics almost entirely to Lorentz. His references to Einstein were notably limited to the photoelectric effect [13], a separate groundbreaking contribution, but never in connection with special relativity itself. For example, in 1912, Poincaré posed the question of whether “the mechanics of Lorentz” would endure after the burgeoning developments in quantum theory . He wrote: [13]

In all instances in which it differs from that of Newton, the mechanics of Lorentz endures. We continue to believe that no body in motion will ever be able to exceed the speed of light; that the mass of a body is not a constant, but depends on its speed and the angle formed by this speed with the force which acts upon the body; that no experiment will ever be able to determine whether a body is at rest or in absolute motion either in relation to absolute space or even in relation to the ether.

This resolute focus on “the mechanics of Lorentz” underscores a fundamental conceptual divergence. Poincaré, despite his own profound insights into the relativity principle and the mathematical transformations, appears to have remained firmly rooted in an aether-based framework, viewing the relativistic effects as dynamic consequences within that framework rather than as fundamental properties of spacetime itself, as Einstein proposed. His silence on Einstein’s contribution to relativity, therefore, speaks volumes about their differing philosophical and physical commitments.

Einstein

The persistent myth of Albert Einstein as a solitary genius, oblivious to the scientific currents of his time, has been effectively dismantled by historical scholarship. Jürgen Renn, the Director of the Max Planck Institute for the History of Science , has meticulously documented Einstein’s deep engagement with contemporary research. Renn noted Einstein’s prolific contributions to the Annalen der Physik : [14]

The Annalen also served as a source of modest additional income for Einstein, who wrote more than twenty reports for its Beiblätter – mainly on the theory of heat – thus demonstrating an impressive mastery of the contemporary literature. This activity started in 1905. [15] and probably resulted from his earlier publications in the Annalen in this field. Going by his publications between 1900 and early 1905, one would conclude that Einstein’s specialty was thermodynamics.

This paints a picture not of an isolated amateur, but of a deeply knowledgeable physicist, thoroughly immersed in the scientific discourse of his era.

Einstein himself, in 1907 [16], offered a crucial insight into his conceptual breakthrough: he observed that the auxiliary quantity introduced by Lorentz, which Lorentz termed “local time,” could simply be defined as “time” itself. This seemingly minor re-labeling was, in fact, a profound re-conceptualization, stripping away the distinction between “true” and “apparent” time and elevating “local time” to the status of a fundamental physical reality. In 1909 [17] and again in 1912 [18], Einstein further clarified his approach: [B 8]

…it is impossible to base a theory of the transformation laws of space and time on the principle of relativity alone. As we know, this is connected with the relativity of the concepts of “simultaneity” and “shape of moving bodies.” To fill this gap, I introduced the principle of the constancy of the velocity of light, which I borrowed from H. A. Lorentz’s theory of the stationary luminiferous ether, and which, like the principle of relativity, contains a physical assumption that seemed to be justified only by the relevant experiments (experiments by Fizeau, Rowland, etc.) [18]

— Albert Einstein (1912), translated by Anna Beck (1996).

This statement highlights Einstein’s explicit acknowledgment of borrowing the light postulate from Lorentz. However, Einstein and his proponents consistently maintained that this “light postulate,” when combined with the principle of relativity, rendered the classical ether entirely superfluous and led directly to Einstein’s uniquely coherent version of relativity. His genius lay in identifying the minimum set of postulates required to derive the theory, and in recognizing their profound implications for the nature of space and time.

Regarding Poincaré, Einstein referred to him in connection with the inertia of energy in 1906 [19] and for non-Euclidean geometry in 1921 [20]. Yet, conspicuously absent were any references to Poincaré in connection with the Lorentz transformation , the relativity principle, or the light-signal synchronization procedure—precisely the areas where Poincaré’s contributions were most significant to the pre-Einstein development of the theory. It wasn’t until the final years before his death that Einstein, perhaps prompted by his biographer Pais in 1950 (who reportedly sent Einstein a copy of Poincaré’s Palermo paper, which Einstein claimed he had not read before), acknowledged some of Poincaré’s contributions. In 1953, Einstein wrote: [B 9]

There is no doubt, that the special theory of relativity, if we regard its development in retrospect, was ripe for discovery in 1905. Lorentz had already recognized that the transformations named after him are essential for the analysis of Maxwell’s equations , and Poincaré deepened this insight still further. Concerning myself, I knew only Lorentz’s important work of 1895 […] but not Lorentz’s later work, nor the consecutive investigations by Poincaré. In this sense my work of 1905 was independent. […] The new feature of it was the realization of the fact that the bearing of the Lorentz transformation transcended its connection with Maxwell’s equations and was concerned with the nature of space and time in general. A further new result was that the “Lorentz invariance” is a general condition for any physical theory.

This late acknowledgment, while perhaps somewhat belated, clearly articulates what Einstein perceived as the “new feature” of his own work: the conceptual leap from the Lorentz transformations being a mathematical device for electrodynamics to being a fundamental statement about the very structure of space and time . This was the radical reinterpretation that truly set his work apart.

Timeline

This section chronicles the notable scholarly publications and their authors who have weighed in on this enduring debate, offering varied perspectives on the intricate question of priority and conceptual originality.

Sir Edmund Whittaker (1954)

In 1954, Sir Edmund Taylor Whittaker , an eminent English mathematician and historian of science, stirred considerable controversy with his publication. He controversially credited Henri Poincaré with the iconic equation $E=mc^2$, a claim that flies in the face of conventional historical attribution. Furthermore, his book, A History of the Theories of Aether and Electricity , contained a chapter provocatively titled “The Relativity Theory of Poincaré and Lorentz.” [B 10] Whittaker’s narrative explicitly favored Poincaré and Lorentz, making particular reference to Lorentz’s 1904 paper (which Whittaker erroneously dated to 1903), Poincaré’s influential St. Louis speech (“The Principles of Mathematical Physics”) delivered in September 1904, and Poincaré’s crucial June 1905 paper. In a move that significantly downplayed Einstein’s contributions, Whittaker assigned only minor importance to Einstein’s relativity paper, asserting that it merely formulated the Doppler and aberration formulas. This revisionist stance was so entrenched that Max Born reportedly spent three years in a futile attempt to dissuade Whittaker, who remained steadfast in his conviction that Poincaré had already articulated everything of significance, and that Lorentz had unequivocally provided the correct physical interpretation.

Gerald Holton (1960)

Whittaker’s provocative claims met with sharp criticism from Gerald Holton (1960, 1973), a distinguished historian of science whose work, particularly Thematic Origins of Scientific Thought , profoundly shaped the understanding of this dispute. [B 1] Holton argued for fundamental, irreducible differences between Einstein’s theory on one hand, and the theories of Poincaré and Lorentz on the other. Einstein, he contended, executed a radical reformulation of the very concepts of space and time , thereby decisively eradicating “absolute space” and, consequently, the notion of a stationary luminiferous aether from the bedrock of physics. Poincaré and Lorentz, conversely, remained tethered to the stationary aether concept, seeking merely to modify Newtonian dynamics rather than to replace it with a fundamentally new kinematics. Holton famously attributed “Poincaré’s silence” – his conspicuous failure to ever mention Einstein’s contributions to relativity – to these deeply divergent conceptual frameworks. Einstein’s radical views on space and time, and his abandonment of the aether, were, in Holton’s analysis, simply unacceptable to Poincaré, leading the latter to refer exclusively to Lorentz as the progenitor of the “new mechanics.” Holton further highlighted what he saw as inaccuracies in Whittaker’s account, such as the misdating of Lorentz’s 1904 paper. Views consistent with Holton’s were later articulated (1967, 1970) by his former student, Stanley Goldberg. [B 11]

G. H. Keswani (1965)

In a series of articles published between 1965 and 1966, G. H. Keswani meticulously traced the history of relativity, ultimately asserting that the primary credit for special relativity rightfully belonged to Poincaré and Lorentz. [B 12] Keswani emphasized that Poincaré consistently credited Lorentz, while Lorentz, in turn, acknowledged both Poincaré and Einstein, famously declining to take sole credit for himself. Demonstrating a rather bold, some might say audacious, perspective, Keswani also significantly downplayed the importance of general relativity , dismissively stating that “Einstein’s general theory of relativity is only a theory of gravitation and of modifications in the laws of physics in gravitational fields.” [B 12] This narrow interpretation, if accepted, would elevate the special theory to the singular, true theory of relativity. Keswani cited Vladimir Fock as sharing this particular opinion.

This series of articles predictably provoked a robust intellectual response, notably from Herbert Dingle and Karl Popper .

Dingle, among other salient points, articulated that “… the ‘principle of relativity’ had various meanings, and the theories associated with it were quite distinct; they were not different forms of the same theory. Each of the three protagonists…. was very well aware of the others …. but each preferred his own views.” [B 13] This highlights the crucial point that semantic similarities can mask profound conceptual differences.

Karl Popper , a philosopher of science known for his incisive critiques, added: “Though Einstein appears to have known Poincaré’s Science and Hypothesis prior to 1905, there is no theory like Einstein’s in this great book.” [B 14] This directly challenged the notion that Einstein’s ideas were merely a rehash of Poincaré’s.

Unfazed by the criticism, Keswani staunchly refused to retract his claims, issuing replies in two letters published in the same journal ([B 15] and [B 16]). In his response to Dingle, he maintained that the three relativity theories were fundamentally “at heart the same: “.. they meant much that was common. And that much mattered the most.” [B 15] A rather convenient simplification, one might observe.

Dingle, ever persistent, further commented the following year (1967) on the historical crediting: “Until the first World War, Lorentz’s and Einstein’s theories were regarded as different forms of the same idea, but Lorentz, having priority and being a more established figure speaking a more familiar language, was credited with it.” This suggests that initial historical reception was influenced by factors beyond pure conceptual originality.

Arthur I. Miller (1973)

Arthur I. Miller (1973, 1981) [B 2] largely concurred with the insightful analyses of Holton and Goldberg, further strengthening their arguments. Miller posited that while the terminology employed by Poincaré and Einstein—such as the “principle of relativity”—bore a striking superficial resemblance, their underlying conceptual content diverged sharply. According to Miller, Poincaré utilized this principle primarily to refine and complete the aether-based “electromagnetic world view” espoused by Lorentz and Abraham. He further argued that Poincaré, in his July 1905 paper, maintained a distinct separation between “ideal” and “real” systems and electrons. Crucially, Miller contended that the reference frames used by Lorentz and Poincaré often lacked an unambiguous physical interpretation, frequently serving as mere mathematical tools. In stark contrast, Einstein’s theory asserted that processes occurring in different inertial frames were not only mathematically equivalent but physically equivalent, a profound shift. Miller summarized this distinction in 1981:

p. 172: " Although Poincaré’s principle of relativity is stated in a manner similar to Einstein’s, the difference in content is sharp. The critical difference is that Poincaré’s principle admits the existence of the ether, and so considers the velocity of light to be exactly c only when it is measured in coordinate systems at rest in the ether. In inertial reference systems, the velocity of light is c and is independent of the emitter’s motion as a result of certain compensatory effects such as the mathematical local time and the hypothesis of an unobservable contraction. Consequently, Poincaré’s extension of the relativity principle of relative motion into the dynamics of the electron resided in electromagnetic theory, and not in mechanics…Poincaré came closest to rendering electrodynamics consistent, but not to a relativity theory. " p. 217: “Poincaré related the imaginary system Σ’ to the ether fixed system S’”.

Miller, in a later work (1996) [B 2], elaborated that Poincaré’s approach was heavily guided by empiricism, leading him to remain open to the possibility that experiments might ultimately disprove relativity. This cautious stance, Miller suggested, made Einstein more deserving of credit, despite the potential for substantial influence from Poincaré’s earlier papers. Miller also challenged the notion of mathematical equivalence, asserting that “Emphasis on conventionalism … led Poincaré and Lorentz to continue to believe in the mathematical and observational equivalence of special relativity and Lorentz’s electron theory. This is incorrect.” [p. 96] Instead, Miller argued that while the theories might be mathematically equivalent, they were decidedly not physically equivalent. [p. 91–92]

Abraham Pais (1982)

In his acclaimed 1982 Einstein biography, Subtle is the Lord , Abraham Pais offered a nuanced, yet ultimately critical, assessment of Poincaré’s role. [B 3] Pais argued that Poincaré “comes near” to discovering special relativity , particularly in his St. Louis lecture of September 1904 and his June 1905 paper. However, Pais contended that Poincaré ultimately “failed” to fully grasp the theory, primarily because, both in 1904 and later in 1909, he treated length contraction as a third independent hypothesis, alongside the relativity principle and the constancy of the speed of light. According to Pais, Poincaré therefore never fully understood, or at least never fully accepted, the profound simplicity of special relativity, where the entire theoretical edifice, including length contraction, could be elegantly derived from just two fundamental postulates. Pais further argued that Lorentz, both before and after 1905, never truly abandoned the conceptual anchor of the stationary aether:

p. 118: " Throughout the paper of 1895, the Fresnel aether is postulated explicitly “; p. 125: " Like Voigt before him, Lorentz regarded the transformation … only as a convenient mathematical tool for proving a physical theorem … he proposed to call t the general time and t’ the local time. Although he didn’t say it explicitly, it is evident that to him there was, so to speak, only one true time t. “; p. 166: " 8.3. Lorentz and the Aether… For example, Lorentz still opines that the contraction of the rods has a dynamic origin. There is no doubt that he had read and understood Einstein’s papers by then. However, neither then nor later was he prepared to accept their conclusions as the definitive answer to the problems of the aether. "

While Pais acknowledged the masterpiece status of Whittaker’s History, he did not shy away from criticizing Whittaker’s chapter on the “Relativity theory of Poincaré and Lorentz,” remarking with a certain academic venom: “how well the author’s lack of physical insight matches his ignorance of the literature.” This rather “scurrilous” and “lamentable” phrasing [22], as one notable reviewer observed, underscored the intensity of the intellectual passions involved. It’s a reminder that even the most scholarly debates can devolve into personal jabs. Interestingly, other prominent scientists, such as Max Born , praised parts of Whittaker’s second volume, particularly the history of quantum mechanics, as “the most amazing feats of learning, insight, and discriminations” [23], and Freeman Dyson described the two volumes as “the most scholarly and generally authoritative history of its period that we shall ever get.” [24] The complexities of historical assessment, it seems, are rarely simple.

Elie Zahar (1983)

In a series of influential papers (1983, 2000), Elie Zahar [B 17] put forth the argument that both Einstein (in his June 1905 paper) and Poincaré (in his July 1905 paper) independently arrived at the discovery of special relativity . While acknowledging that Whittaker had been unjust in his assessment of Einstein, Zahar contended that Whittaker’s positive account of Poincaré’s actual achievements contained “much more than a simple grain of truth.” In Zahar’s view, it was Poincaré’s somewhat unsystematic and occasionally erroneous statements, particularly within his more philosophical papers (often linked to conventionalism ), that inadvertently obscured his true contributions and prevented him from receiving due credit. Zahar interpreted Poincaré as a “structural realist,” concluding from this that Poincaré genuinely adhered to the relativity of time and space, and that his references to the aether were of secondary, perhaps even pragmatic, importance. He further argued that Poincaré’s 1905/6 paper, with its treatment of gravitation and the introduction of four-dimensional space, was in some respects superior to Einstein’s 1905 paper. Nevertheless, Zahar also gave significant credit to Einstein for introducing the concept of Mass–Energy equivalence in its full generality and for charting the intellectual path that ultimately led to the development of general relativity .

John Stachel (1995)

John Stachel (1995) [B 18], a leading scholar in Einstein studies, observed that the ongoing debate regarding the respective contributions of Lorentz, Poincaré, and Einstein to relativity inherently hinges on one’s precise definition of “relativity.” Stachel argued, with considerable force, that the core of special relativity lies in its kinematics and its revolutionary new understanding of space and time . Dynamical theories, he contended, must then be formulated in strict accordance with this redefined kinematic scheme. Based on this foundational definition, Stachel concluded that Einstein stands as the principal originator of the modern, coherent understanding of special relativity. In his analysis, Lorentz, despite his mathematical brilliance, interpreted the Lorentz transformation primarily as a mathematical artifice, a useful device rather than a statement of fundamental reality. Poincaré’s thinking, Stachel acknowledged, was far closer to the modern understanding of relativity. Yet, Poincaré, too, remained intellectually bound by the belief in the dynamical effects of the aether, and continued to draw a distinction between observers who were at rest relative to it and those in motion. Stachel succinctly summarized Poincaré’s ultimate limitation: “He never organized his many brilliant insights into a coherent theory that resolutely discarded the aether and the absolute time or transcended its electrodynamic origins to derive a new kinematics of space and time on a formulation of the relativity principle that makes no reference to the ether.”

Peter Galison (2002)

In his meticulously researched book, Einstein’s clocks, Poincaré’s maps (2002), [B 5] [B 19] Peter Galison undertook a comprehensive comparison of Poincaré’s and Einstein’s respective approaches to fundamentally reformulating the concepts of space and time . Galison, with a refreshing pragmatism, concluded that the perennial questions—“Did Einstein really discover relativity? Did Poincaré already have it?"—have become “as tedious as they are fruitless.” This is because the answer inevitably depends on which specific aspects of relativity one deems most essential: the definitive rejection of the aether, the derivation and interpretation of the Lorentz transformation , its profound connection to the nature of space and time, the accuracy of its experimental predictions, or other contributing elements. For Galison, what proved more illuminating was to recognize that both thinkers were deeply preoccupied with the practical challenges of clock synchronization, and both, through their distinct pathways, developed a new, operational definition of simultaneity. However, a key divergence remained: Poincaré pursued what Galison termed a “constructive approach,” and critically, he continued to adhere to the concepts of Lorentz’s stationary aether and the distinction between “apparent” and “true” times. Einstein, on the other hand, boldly abandoned the aether entirely, thereby establishing that all times in different inertial frames were equally valid and physically real. Galison was careful to point out that this adherence did not render Poincaré “conservative”; indeed, Poincaré frequently alluded to the revolutionary character of Lorentz’s “new mechanics.”

Anatoly Alexeevich Logunov on special relativity (2004)

Anatoly Logunov , in his 2004 book dedicated to Poincaré’s relativity theory [B 20], presented a compelling argument for Poincaré’s priority. The book notably includes an English translation (on page 113, rendered in modern notation) of the section from Poincaré’s 1900 article containing the equation $E=mc^2$. Logunov unequivocally states that Poincaré’s two 1905 papers are conceptually superior to Einstein’s 1905 paper. According to Logunov, Poincaré was the first scientist to fully grasp the profound importance of invariance under the Poincaré group as a guiding principle for the development of new physical theories. Furthermore, in Chapter 9 of his book, Logunov highlights that Poincaré’s second 1905 paper was the inaugural work to articulate a complete theory of relativistic dynamics, encompassing the correct relativistic analogue of Newton’s fundamental equation, $F=ma$.

Logunov also addressed the persistent narrative of Einstein’s isolation. On page 142, he points out that Einstein was a prolific reviewer for the Beiblätter Annalen der Physik, having written 21 reviews in 1905 alone. In Logunov’s estimation, this extensive reviewing activity directly contradicts claims that Einstein worked in relative isolation and had limited access to contemporary scientific literature. Among the papers reviewed in the fourth (out of 24) issue of 1905 of the Beiblätter, there is a review of Lorentz’s 1904 paper by Richard Gans , which explicitly contains the Lorentz transformations . Logunov interprets this as strong evidence that Einstein was indeed familiar with Lorentz’s paper, containing the correct relativistic transformations, as early as the beginning of 1905. This, he suggests, casts a particular light on the fact that Einstein’s June 1905 paper does not explicitly mention Lorentz in connection with this specific result.

Harvey R. Brown (2005)

Harvey R. Brown (2005), a philosopher of physics who champions a dynamical interpretation of relativistic effects (akin to Lorentz’s, but notably “without a hidden aether frame”), meticulously detailed the intellectual journey to special relativity from Michelson to Einstein in Section 4 of his work. [B 21] He began by articulating the historical crucible:

p. 40: “The cradle of special theory of relativity was the combination of Maxwellian electromagnetism and the electron theory of Lorentz (and to a lesser extent of Larmor) based on Fresnel’s notion of the stationary aether…. It is well known that Einstein’s special relativity was partially motivated by this failure [to find the aether wind], but in order to understand the originality of Einstein’s 1905 work it is incumbent on us to review the work of the trailblazers, and in particular Michelson, FitzGerald, Lorentz, Larmor, and Poincaré. After all they were jointly responsible for the discovery of relativistic kinematics, in form if not in content, as well as a significant portion of relativistic dynamics as well.”

Brown then critically examined Lorentz’s work prior to 1905, focusing on the development of Lorentz’s “theorem of corresponding states ,” and offered this assessment:

p. 54: “Lorentz’s interpretation of these transformations is not the one Einstein would give them and which is standardly embraced today. Indeed, until Lorentz came to terms with Einstein’s 1905 work, and somehow despite Poincaré’s warning, he continued to believe that the true coordinate transformations were the Galilean ones, and that the ‘Lorentz’ transformations … were merely a useful formal device…” p. 56. “Lorentz consistently failed to understand the operational significance of his notions of ’local’ time…. He did however have an intimation of time dilation in 1899, but inevitably there are caveats…. The hypotheses of Lorentz’s system were starting to pile up, and the spectre of ad hocness was increasingly hard to ignore.”

This highlights Lorentz’s conceptual limitations despite his mathematical achievements. Brown then turned to Poincaré’s significant contributions:

p. 62: “Indeed, the claim that this giant of pure and applied mathematics co-discovered special relativity is not uncommon, and it is not hard to see why. Poincaré was the first to extend the relativity principle to optics and electrodynamics exactly. Whereas Lorentz, in his theorem of corresponding states, had from 1899 effectively assumed this extension of the relativity principle up to second-order effects, Poincaré took it to hold for all orders. Poincaré was the first to show that Maxwell’s equations with source terms are strictly Lorentz covariant. … Poincaré was the first to use the generalized relativity principle as a constraint on the form of the coordinate transformations. He recognized that the relativity principle implies that the transformations form a group, and in further appealing to spatial isotropy. … Poincaré was the first to see the connection between Lorentz’s ‘local time’, and the issue of clock synchrony. … It is fair to say that Poincaré was the first to understand the relativity of simultaneity, and the conventionality of distant simultaneity. Poincaré anticipated Minkowski’s interpretation of the Lorentz transformations as a passive, rigid rotation within a four-dimensional pseudo-Euclidean spacetime. He was also aware that the electromagnetic potentials transform in the manner of what is now called a Minkowski 4-vector. He anticipated the major results of relativistic dynamics (and in particular the relativistic relations between force, momentum and velocity), but not E=mc² in its full generality.”

This comprehensive list of “firsts” for Poincaré certainly makes a strong case for his profound insights. However, Brown, with intellectual rigor, proceeded to outline the reasons against crediting Poincaré with co-discovery:

p. 63–64: “What are the grounds for denying Poincaré the title of co-discoverer of special relativity? … Although Poincaré understood independently of Einstein how the Lorentz transformations give rise to non-Galilean transformation rules for velocities (indeed Poincaré derived the correct relativistic rules), it is not clear that he had a full appreciation of the modern operational significance attached to coordinate transformations…. he did not seem to understand the role played by the second-order terms in the transformation. Compared with the cases of Lorentz and Larmor, it is even less clear that Poincaré understood either length contraction or time dilation to be a consequence of the coordinate transformation…. What Poincaré was holding out for was no less than a new theory of ether and matter – something far more ambitious than what appeared in Einstein’s 1905 relativity paper…p. 65. Like Einstein half a decade later, Poincaré wanted new physics, not a reinterpretations or reorganization of existing notions.”

Brown then directly addressed and dismissed the popular idea, held by some authors and historians, that the primary distinction between Einstein and his predecessors lay solely in Einstein’s rejection of the aether. He pointed out that it is always theoretically possible to introduce the notion of a privileged, unobservable frame into special relativity for various reasons, and even Poincaré himself had argued that “some day, no doubt, the aether will be thrown aside as useless.” However, Brown then provided compelling examples of what, in his well-reasoned opinion, constituted the truly novel features in Einstein’s work:

p. 66: “The full meaning of relativistic kinematics was simply not properly understood before Einstein. Nor was the ’theory of relativity’ as Einstein articulated it in 1905 anticipated even in its programmatic form.” p. 69. “How did Albert Einstein…arrive at his special theory of relativity?…I want only to stress that it is impossible to understand Einstein’s discovery (if that is the right word) of special relativity without taking on board the impacts of the quantum in physics.” p. 81. “In this respect [Brown refers to the conventional nature of distant simultaneity] Einstein was doing little more than expanding on a theme that Poincaré had already introduced. Where Einstein goes well beyond the great mathematician is in his treatment of the coordinate transformations… In particular, the extraction of the phenomena of length contraction and time dilation directly from the Lorentz transformations in section 4 of the 1905 paper is completely original.”

Following this detailed historical analysis, Brown further developed his own dynamical interpretation of special relativity , contrasting it with Einstein’s purely kinematical approach in the 1905 paper (though he acknowledges that this dynamical view is implicitly contained within Einstein’s work, “masqueraded in the language of kinematics,” p. 82), and the modern, geometric understanding of spacetime .

Roger Cerf (2006)

Roger Cerf (2006) [B 22] firmly asserted Einstein’s priority in the development of special relativity , directly challenging the claims made by Leveugle and others regarding Poincaré’s precedence. While Cerf readily conceded that Poincaré made undeniably important contributions to the nascent theory of relativity, he argued, echoing the position of Pais, that Poincaré “stopped short before the crucial step.” This crucial misstep, in Cerf’s view, was Poincaré’s treatment of length contraction as a “third hypothesis,” which indicated a lack of complete conceptual understanding of the theory’s fundamental principles. Cerf emphasized: “Einstein’s crucial step was that he abandoned the mechanistic ether in favor of a new kinematics.” He also refuted the notion that Poincaré invented $E=mc^2$ in its modern, universally relativistic sense, arguing that Poincaré did not fully grasp the profound implications of this relationship beyond specific electromagnetic contexts. Furthermore, Cerf dismissed Leveugle’s proposed Hilbert–Planck–Einstein connection as an implausible conspiracy theory , underscoring the occasional descent of academic debate into less savory territory.

Shaul Katzir (2005)

Shaul Katzir (2005) [B 23] offered a distinctive perspective, contending that “Poincaré’s work should not be seen as an attempt to formulate special relativity, but as an independent attempt to resolve questions in electrodynamics.” Contrary to the interpretations of Miller and other scholars, Katzir posited that Poincaré’s rigorous development of electrodynamics eventually led him to reject a purely electromagnetic world view, largely due to the introduction of non-electromagnetic Poincaré stresses in 1905. Katzir argued that Poincaré’s theory, rather than being a direct precursor to Einstein’s, represented a distinct “relativistic physics” guided by the relativity principle. However, within this framework, “Lorentz’s theory and Newton’s theory remained as the fundamental bases of electrodynamics and gravitation,” suggesting that Poincaré’s conceptual revolution, while significant, did not entirely break free from the gravitational pull of classical paradigms.

Scott Walter (2005, 2007)

Scott Walter (2005) [B 24] initially argued that both Poincaré and Einstein independently presented versions of the theory of relativity in 1905. However, in his later work in 2007 [B 24], Walter elaborated on a critical conceptual divergence. He noted that while Poincaré formally introduced four-dimensional spacetime in 1905/6, he nevertheless continued to adhere to the idea of “Galilei spacetime.” That is, Poincaré pragmatically preferred Lorentz covariance over Galilei covariance when dealing with phenomena that were empirically testable; yet, in terms of the fundamental nature of space and time , Poincaré’s intellectual allegiance remained with Galilei spacetime rather than Minkowski spacetime . Consequently, length contraction and time dilation were, in Poincaré’s view, “merely apparent phenomena due to motion with respect to the ether.” This distinction, Walter argued, encapsulates the fundamental difference between the two principal approaches to relativity theory: that of “Lorentz and Poincaré” on one side, rooted in a dynamic, aether-bound explanation, and “Einstein and Minkowski” on the other, advocating a kinematic, spacetime-based redefinition of reality.

See also

• History of Lorentz transformations
• History of special relativity
• Criticism of relativity theory#Accusations of plagiarism and priority discussions
• List of scientific priority disputes
• General relativity priority dispute
• Multiple discovery

Notes

• [1] On Olinto De Pretto alleged contributions by a mathematical historian, see [1], The Guardian, 10 November 1999.
• [2] On Mileva Marić’s alleged contributions, see The Einstein Controversy, Physics Central, 17 December 2008.
• [3] Whittaker (1953), pp. 27–77
• [4] [Poi02]
• [5] [Sta89], p. 893, footnote 10
• [6] [Ein05d], last section
• [7] Einstein, Albert: “Ether and the Theory of Relativity” (1920), republished in Sidelights on Relativity (Methuen, London, 1922)
• [8] Isaacson, Walter (2007). Einstein: His Life and Universe. Simon and Schuster. p. 318. ISBN  978-0-7432-6473-0. Extract of page 318
• [9] [Lor14]
• [10] [Poi06]
• [11]
  • Lorentz, H.A. (1916), The theory of electrons, Leipzig & Berlin: B.G. Teubner
• [12]
  • Lorentz, H.A.; Lorentz, H. A.; Miller, D. C.; Kennedy, R. J.; Hedrick, E. R.; Epstein, P. S. (1928), “Conference on the Michelson–Morley Experiment”, The Astrophysical Journal, 68: 345–351, Bibcode :1928ApJ….68..341M, doi :10.1086/143148
• [13] a b [Poi13]
• [14] Renn, J.,: Albert Einstein in den Annalen der Physik, 2005
• [15] The titles of 21 reviews written in 1905 can be found in “The Collected Papers of Albert Einstein, Volume 2”. See online Archived 2008-09-06 at the Wayback Machine .
• [16]
  • Einstein, A. (1907), “Über das Relativitätsprinzip und die aus demselben gezogenen Folgerungen” (PDF), Jahrbuch der Radioaktivität und Elektronik, 4: 411–462
• [17]
  • Einstein, A. (1909), “Über die Entwicklungen unserer Anschauungen über das Wesen und die Konstitution der Strahlung” (PDF), Physikalische Zeitschrift, 10 (22): 817–825. See also English translation
• [18] a b
  • Einstein, A. (1912), “Relativität und Gravitation. Erwiderung auf eine Bemerkung von M. Abraham” (PDF), Annalen der Physik, 38 (10): 1059–1064, Bibcode :1912AnP…343.1059E, doi :10.1002/andp.19123431014, S2CID  120162895. English translation:
  • Einstein, Albert (1996). The Collected Papers of Albert Einstein, Volume 4: The Swiss Years: Writings, 1912–1914 (English translation supplement; translated by Anna Beck, with Don Howard, consultant ed.). Princeton, New Jersey: Princeton University Press. ISBN  978-0-691-02610-7.
• [19]
  • Einstein, A. (1906), “Das Prinzip von der Erhaltung der Schwerpunktsbewegung und die Trägheit der Energie” (PDF), Annalen der Physik, 20 (8): 627–633, Bibcode :1906AnP…325..627E, doi :10.1002/andp.19063250814, S2CID  120361282
• [20]
  • Einstein, A. (1922), Geometry and Experience , London: Methuen & Co.
• [21] Born’s letter to Einstein in October of 1953
• [22]
  • McCrea, W.H. (August 1983). “‘SUBTLE IS THE LORD.…’ The science and life of Albert Einstein”. Physics of the Earth and Planetary Interiors. 33 (1): 64–65. doi :10.1016/0031-9201(83)90008-0.
• [23]
  • Born, Max (1954). “REVIEWS”. The British Journal for the Philosophy of Science. V (19): 261–263. doi :10.1093/bjps/V.19.261. ISSN  0007-0882.
• [24]
  • Dyson, Freeman J. (March 1954). “Books”. Scientific American. 190 (3): 92–99. Bibcode :1954SciAm.190c..92D. doi :10.1038/scientificamerican0354-92. ISSN  0036-8733.

Citations

• [B 1] a b
  • Holton, G. (1960), “On the Origins of the Special Theory of Relativity”, American Journal of Physics, 28 (7): 627–636, Bibcode :1960AmJPh..28..627H, doi :10.1119/1.1935922
  • Holton, Gerald (1973–1988), Thematic Origins of Scientific Thought: Kepler to Einstein , Harvard University Press, ISBN  978-0-674-87748-1
• [B 2] a b c
  • Miller, A.I. (1973), “A study of Henri Poincaré’s “Sur la Dynamique de l’Electron”, Arch. Hist. Exact Sci., 10 (3–5): 207–328, doi :10.1007/BF00412332, S2CID  189790975
  • Miller, Arthur I. (1981), Albert Einstein’s special theory of relativity. Emergence (1905) and early interpretation (1905–1911), Reading: Addison–Wesley, ISBN  978-0-201-04679-3
  • Miller, A.I. (1996), “Why did Poincaré not formulate special relativity in 1905?”, in Jean-Louis Greffe; Gerhard Heinzmann; Kuno Lorenz (eds.), Henri Poincaré : science et philosophie, Berlin: Akademie Verlag, pp. 69–100
• [B 3] a b
  • Pais, Abraham (1982), Subtle is the Lord: The Science and the Life of Albert Einstein, New York: Oxford University Press, ISBN  978-0-19-280672-7
• [B 4]
  • Torretti, Roberto (1983), Relativity and Geometry, Elsevier, Bibcode :1983rege.book…..T, ISBN  978-0-08-026773-9
• [B 5] a b
  • Galison, Peter (2003), Einstein’s Clocks, Poincaré’s Maps: Empires of Time, New York: W.W. Norton, ISBN  978-0-393-32604-8
• [B 6]
  • Darrigol, O. (2000), Electrodynamics from Ampére to Einstein, Oxford: Clarendon Press, ISBN  978-0-19-850594-5
  • Darrigol, O. (2004), “The Mystery of the Einstein–Poincaré Connection”, Isis, 95 (4): 614–626, Bibcode :2004Isis…95..614D, doi :10.1086/430652, PMID  16011297, S2CID  26997100
  • Darrigol, O. (2005), “The Genesis of the theory of relativity” (PDF), Séminaire Poincaré, 1: 1–22, Bibcode :2006eins.book….1D, doi :10.1007/3-7643-7436-5_1, ISBN  978-3-7643-7435-8
• [B 7]
  • Janssen, M. (1995), A Comparison between Lorentz’s Ether Theory and Special Relativity in the Light of the Experiments of Trouton and Noble, Bibcode :1995PhDT……..26J, archived from the original on 2008-08-21, retrieved 2008-03-15 (thesis)
• [B 8]
  • Alberto A. Mart́ínez (2009), Kinematics: the lost origins of Einstein’s relativity, Johns Hopkins University Press, ISBN  978-0-8018-9135-9
• [B 9]
  • Born, M. (1956), Physics in my generation, London & New York: Pergamon Press
• [B 10] Whittaker, E. T (1953) A History of the Theories of Aether and Electricity : Vol 2 The Modern Theories 1900–1926. Chapter II: The Relativity Theory of Poincaré and Lorentz, Nelson, London.
• [B 11]
  • Goldberg, S. (1967), “Henri Poincaré and Einstein’s Theory of Relativity”, American Journal of Physics, 35 (10): 934–944, Bibcode :1967AmJPh..35..934G, doi :10.1119/1.1973643
  • Goldberg, S. (1970), “Poincaré’s silence and Einstein’s relativity”, British Journal for the History of Science, 5: 73–84, doi :10.1017/S0007087400010633, S2CID  123766991
• [B 12] a b Keswani, G. H. (1965–6) “Origin and Concept of Relativity, Parts I, II, III”, Br. J. Philos. Sci., v15–17. British Journal for the Philosophy of Science,
  • ISSN  0007-0882.
• [B 13] Herbert Dingle, “Note on Mr Keswani’s articles, Origin and Concept of Relativity”, Br. J. Philos. Sci., vol 16, No 63 (Nov 1965), 242-246 (a response to [Kes65])
• [B 14] Karl R. Popper , “A Note on the Difference Between the Lorentz–Fitzgerald Contraction and the Einstein Contraction”, Br. J. Phil. Sci. 16:64 (Feb 1966): 332–333 (a response to [Kes65])
• [B 15] a b Keswani, G. H. (1966), “Reply to Professor Dingle and Mr Levinson”, Br. J. Philos. Sci., Vol. 17, No. 2 (Aug 1966), 149–152 (a response to [Din65])
• [B 16] Keswani, G. H. (1966), “Origin and Concept of Relativity: Reply to Professor Popper”, Br. J. Philos. Sci., Vol 17 no 3 (Nov 1966), 234–236 (a response to [Pop65]
• [B 17]
  • Zahar, Elie (1983), “Poincaré’s Independent Discovery of the relativity principle”, Fundamenta Scientiae, 4: 147–175
  • Zahar, Elie (1989), Einstein’s Revolution: A Study in Heuristic, Chicago: Open Court Publishing Company, ISBN  978-0-8126-9067-5
  • Zahar, E. (2001), Poincare’s Philosophy: From Conventionalism to Phenomenology, Chicago: Open Court Pub Co, ISBN  978-0-8126-9435-2
• [B 18]
  • Stachel, John (1995), “History of relativity”, in Laurie M. Brown; Brian Pippard; Abraham Pais (eds.), Twentieth Century Physics, Philadelphia: Institute of Physics, pp. 249–356, ISBN  978-0-7503-0310-1
• [B 19]
  • “aip.org”. Archived from the original on 2015-03-12. Retrieved 2011-09-19.
• [B 20] Logunov, A. A (2004): “Henri Poincaré and Relativity Theory” – Phys. Usp. 47 (2004) 607–621; Usp. Fiz. Nauk 174 (2004) 663–678 – PraXis 2004
  • arXiv :physics/0405075
• [B 21] Harvey R. Brown, Physical relativity: space-time structure from a dynamical perspective. Oxford University Press, 2005.
• [B 22]
  • Cerf, Roger (2006), “Dismissing renewed attempts to deny Einstein the discovery of special relativity”, American Journal of Physics, 74 (9): 818–824, Bibcode :2006AmJPh..74..818C, doi :10.1119/1.2221341
• [B 23]
  • Katzir, Shaul (2005), “Poincaré’s Relativistic Physics: Its Origins and Nature”, Phys. Perspect., 7 (3): 268–292, Bibcode :2005PhP…..7..268K, doi :10.1007/s00016-004-0234-y, S2CID  14751280
• [B 24]
  • Walter, S. (2005), Renn, J. (ed.), “Henri Poincaré and the theory of relativity”, Albert Einstein, Chief Engineer of the Universe: 100 Authors for Einstein, Berlin: 162–165, archived from the original on 2014-10-06, retrieved 2014-10-03
  • Walter, S. (2007–2009), “Hypothesis and Convention in Poincaré’s Defense of Galilei Spacetime”, in Michael Heidelberger; Gregor Schiemann (eds.), The Significance of the Hypothetical in the Natural Sciences, Berlin: Walter de Gruyter, pp. 193–220, archived from the original on 2014-10-07, retrieved 2014-10-03