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    INSTITUTE OF PHYSICS PUBLISHING JOURNAL OF PHYSICS B: ATOMIC, MOLECULAR AND OPTICAL PHYSICS

    J. Phys. B: At. Mol. Opt. Phys. 38 (2005) S437S448 doi:10.1088/0953-4075/38/9/001

    1905a miraculous year

    Jurgen Renn and Dieter Hoffmann

    Max Planck Institute for the History of Science, Wilhelm Street 44, 10117 Berlin, Germany

    E-mail: [email protected] and [email protected]

    Received 15 February 2005

    Published 25 April 2005

    Online at stacks.iop.org/JPhysB/38/S437

    AbstractThe article discusses Einsteins famous papers of 1905his miraculous year

    and deals with their physical and historical context as well as their fundamental

    impact on modern physics. It shows that the papers are not isolated, but

    connected with each other by Einsteins deep-seated conviction of physical

    atomism and his criticism of an ether. They are concerned with specific

    problems that can be characterized as borderline problems since they go

    beyond the traditional divisions between mechanics, electrodynamics, and

    thermodynamics.

    The year 1905 is generally considered Albert Einsteins annus mirabilis. It was not only a year

    of miracles for him personally, but it was also a miraculous year for the further development

    of physics. In this year, besides several book reviews, Einstein published five papers that

    revolutionized the basic principles of physics.

    The titles of Einsteins papers were comparatively unspectacular: On a heuristic point of

    view concerning the production and transformation of light (completed 17 March, 1905); A

    new determination of molecular dimensions (30 April); On the movement of small particles

    suspended in liquids at rest required by the molecular kinetic theory of heat (11 May); On the

    electrodynamics of moving bodies (30 June); and Does the inertia of a body depend upon its

    energy content? (27 September), see figure 1. Every one of these works [1] had far-reaching

    consequences for a physical understanding of the world.

    Thus, the paper on electrodynamics contained the basics of Einsteins theory of special

    relativity, and laid the foundation for a new concept of space and time. This paper led him to

    the most famous physical formula, E = mc2.

    Einsteins work on the creation and transformation of light was based on Max Planckstheory of blackbody radiation, and asserted the existence of so-called light quanta. This meant

    that, contrary to the then well-established and highly successful electromagnetic wave theory,

    light possessed characteristics of particlesa bold and revolutionary hypothesis at the time.

    Ultimately, Einsteins study of Brownian motion was a major factor in the final acceptance

    in physics of atomic theory, which was still controversial at the time.

    What was it that turned this 26-year-old examiner at the Swiss Patent Office in Bern,

    who, far from the leading physical research centres of the time, led more of a modest

    0953-4075/05/090437+12$30.00 2005 IOP Publishing Ltd Printed in the UK S437

    http://dx.doi.org/10.1088/0953-4075/38/9/001http://stacks.iop.org/jb/38/S437http://stacks.iop.org/jb/38/S437http://dx.doi.org/10.1088/0953-4075/38/9/001
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    Figure 1. Facsimile of the title pages of Einsteins 1905 papers. From [16].

    scientific existence (an outsider, and a loner as well), into the greatest revolutionary in the

    world of physics since Isaac Newton? The oft-used reference to the physical genius of

    Einstein romanticizes him more than it explains who he wasand not only because of todays

    inflationary use of that term, which also places sports stars in the same category. Whoever

    deals with the myth of Einstein simply by referring to his genius is, not least, neglecting the

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    Figure 2. Einstein at the Patent Office around 1906.

    specific conditions for his insights and the circumstances of his life that allowed both Einsteins

    personality and his gift for physics to unfold. We will briefly examine these factors below.

    Albert Einstein was born on March 14, 1879 in Ulm as the son of a Jewish family [2].

    His father was at first based in Munich, where the family moved in the summer of 1880.

    Later in 1894 they moved to northern Italy where they worked in the electrical industry. At

    the age of 16 Einstein followed his parents to Italy for a short time, after conflict with the

    authoritarian German school system. He caught up on his diploma in the Swiss town of Aarau

    in 1896, and went from there to study physics and mathematics at the Federal Polytechnic

    Academy in Zurich (later called the Swiss Federal Institute of Technology). Although much

    of the Einstein literature insists on calling him a wayward pupil and an unsuccessful student,

    he was in actuality neither. But his behaviour did indicate a high level of individuality and

    independence from an early age. As a young man he was called an Einspaenner or loner,

    for whom reading physics textbooks was usually more important than going regularly to

    lectures. In the summer of 1900, Einstein succeeded in graduating with a Diploma as a

    Technical Instructor for Mathematics. Unfortunately, he could not at first find any regularemployment, as applications for assistantships with his Zurich teacher Adolf Hurwitz as well

    as with Wilhelm Ostwald in Leipzig or Heike Kamerlingh-Onnes in Leiden were rejected [3].

    Thus Einstein had to make do with work as a tutor and substitute teacher in various Swiss

    schools and boarding schools.

    In the summer of 1902 he managed at last, through the intercession of a friend, to find a

    permanent position at the Swiss Patent Office in Bern. For the next seven years, he worked as a

    technical expert third class andthen second class (see figure 2). But these years were influenced

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    blinkers of specialization, bringing him closer to the internationalist spirit of science as well

    as its worldview and political consequences.

    Above all, this reading sharpened his awareness of scientific puzzles and unresolved

    questions, characteristics that later were of great benefit to his revolutionary work.

    The evidence that Einstein was occupied with original scientific problems even while inschool comes from a paper written when he was 16 years old which dealt with the effect of a

    magnetic field on the dispersion of light in ether, speculating about the ether and asking how

    a beam of light would look from the point of view of an observer also moving at the speed

    of light. These were the problems, the Gedankenexperimente or thought experiments, that

    would later be seen as precursors to Einsteins theory of relativity.

    The image of the young Einstein must also include his early fascinationwhich he shared

    with other great scientistswith the precision and beauty of mathematical thought. He taught

    himself the basics of geometry as well as important areas of higher mathematics.

    When Einstein graduated in the summer of 1900, there was no clear path for him to

    embark upon professionally. This did not keep him from working on his own scientific profile.

    His interests at the time centred on statistical physics, and in the years following he succeeded

    in independently formulating, at about the same time and without any knowledge of the workof the American physicist Josiah Willard Gibbs, the basic principles of this field.

    This achievement resulted from an attempt to expand on the work of Ludwig Boltzmann

    to develop a kinetic theory of heat, in which among other things the electron theory of metals

    as well as radiation theory could be used.

    This parallel discovery of Einsteins would not have necessitated an annus mirabilis, as

    his work in the area of statistical physics would have been more than enough to launch an

    admirable career as a physicist. In fact, his first revolutionary paper of March 1905 would

    actually have stood in the way of such a career at first, as opposed to furthering it. Einsteins

    hypothesis of light quanta was, after all, a radical break with the traditions of optics and

    electrodynamics of the nineteenth century, standing in diametric opposition to the large amount

    of experimental as well as theoretical evidence that supported the electromagnetic wave theory

    of light.

    The fact that Einstein dared to advance this theory is related to his early work on statisticalphysics. This work attempted, e.g., to apply statistical mechanics to what was then the

    prevailing problem of thermal radiation in thermodynamic equilibrium. In the fall of 1900,

    Max Planck developed a formula that is still valid today for the dispersion of energy during

    thermal radiation based on the precise measurements of heat radiation from a blackbody taken

    at the Physikalisch-Technische Reichsanstalt in Berlin. However, the derivation of Plancks

    radiation law, which introduced his quantum of action h to physics, was highly problematic.

    Several physicists had already lodged protests, cf [6], and in the search for a physically

    satisfying derivation of Plancks radiation formula Einstein could show, the higher the energy

    density and wavelength of radiation, the more reasonable the theoretical foundations [of

    Plancks formula] we have been using prove to be: However, they fail completely in the case

    of low wavelengths and low radiation densities (in the area of validity of the so-called Wiens

    radiation formula- JR/DH) [7, Doc. 14].Einstein especially alluded that the classical concept of electromagnetic radiation as

    vibrations in a continuum is irreconcilable with the assumption of thermal equilibrium. The

    number of wave frequencies in a continual ether would be infinite, but the law of dynamic

    equilibrium states that every frequency must receive the same portion of energy. Thus Einstein

    discarded the idea of a continual ether and asserted that the problems of Maxwells theory

    in properly explaining electromagnetic radiation in a blackbody, i.e., radiation in thermal

    equilibrium, could be overcome through a heuristic viewpoint, if one assumes that the

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    energy of light is discontinuously distributed in space. According to the assumption considered

    here, in the propagation of a light ray emitted from a point source, the energy is not distributed

    continuously over ever-increasing volumes of space, but consists of a finite number of energy

    quanta localized at points of space that move without dividing, and can be absorbed or

    generated only as complete units [7, Doc. 14].Thus, the theory of light quanta was formulated, which not only made clear the principle

    irreconcilability between Plancks radiation formula and classical physics, but was also a

    theory with which Einstein could also explain for the first time various anomalies in the

    electromagnetic theory of light.

    This wasStokes formula for fluorescence, the ionization of gases through ultraviolet light,

    and most importantly Philipp Lenards discovery in 1902 of the (qualitative) connection that

    the energy of emitted electrons in the photoelectric effect is not dependent on the intensity of

    the light, but on its frequency [8]. For this correlation, Einstein first formulated the well-known

    photoelectric equation:

    mv2/2 = hf P

    where m is electron mass, v is maximum velocity of the freed electrons, f is frequency oflight, P is characteristic amount of work needed to free a single electron from a metal.

    Thus Einstein had found uses for Plancks quantum constant h outside of thermal radiation

    theory, thereby demonstrating its general significance for the world of physics. But Planck

    himselflike most other physicistswas at first unwilling to go along with Einsteins

    far-reaching conclusions. This was less because Einstein would have a long wait for a

    quantitative confirmation of his photoelectric formula, but most importantly because most

    physicists hoped to preserve the electromagnetic wave theory of light and, along with it,

    classical physics.

    In the end, Einsteins light quantum theory opened up a new, non-classical understanding

    of radiation and matter. In this sense it was not Planck, but Einstein with his 1905 work on

    light quanta, through whom the problem of thermal radiation became the crucial starting point

    for quantum theory, cf [6].

    It was not only his light quantum theory, however, that made Einstein a central figure

    in this process. More importantly, the light quantum theory became the starting point for

    intensive research into the questions of quantum theory, which would make Einstein by far the

    most important pioneer in the early history of quantum theory and which would considerably

    support the insight that the development of this theory would be connected with a deeply

    significant transformative effect on the foundations of classical physics.

    Thus in 1907 Einstein was able, using the quantum hypothesis, to lay the foundations for

    the first non-classical theory of specific heat in solids. In 1909, while considering blackbody

    radiation, he introduced the idea of lights dual nature as both a wave and a particle, and

    in 1912 formulated the law of photochemical equivalence. Further milestones in Einsteins

    activities with quantum theory were a new derivation of Plancks radiation formula in 1916, in

    which the term transitional probability for spontaneous and induced emission and absorption

    of radiation was introduced, thereby laying the theoretical foundations for the invention of thelaser. Finally, in 19241925 he developed BoseEinstein statistics, an equation describing the

    statistical distribution of certain types (todays so-called bosons) of identical particles in an

    ideal gas.

    His participation in the Solvay Conferences, which had taken place since 1911 (see

    figure 3), did much to promote acceptance of quantum theory; but in the 1920s his appearances

    at these summit meetings of leading contemporary physicists were increasingly characterized

    by determined opposition to the so-called Copenhagen Interpretation of quantum mechanics.

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    Figure 3. The first Solvay Conference, Brussels 1911.

    He consistently rejected a statistical interpretation of quantum mechanics because of its

    putative incomplete description of physical reality. In discussions with Niels Bohr and other

    pioneers of modern quantum mechanics, Einstein always pointed out gaps in the theory and

    expressed his belief that all natural processes follow deterministic paths. His now-classic

    saying, formulated in a letter to his friend Max Born on 4 December, 1926, the old one

    . . . is not playing at dice [9], stands for this belief just as it does for his final significant

    contribution to quantum theory, the paper published in 1935 together with Boris Podolsky

    and Nathan Rosen, in which questions about the completeness of a quantum mechanical

    description of physical reality came to a head through the so-called EinsteinPodolskyRosen

    paradox [10].

    Thus it was not only the young Einstein who rebelled against the physics establishment.

    Just how unconventional and strange Einsteins light quantum hypothesis was is made clear,

    for instance, by the fact that it had to struggle for recognition much longer than quantum

    theory itself. Up to the 1920s, it stood alone in the world of physics. Starting in 1914, the

    American physicistRobert Andrew Millikan conducteda long series of precision-measurement

    experiments in order to disprove Einsteins bold light quantum theory and his explanation of

    the photoelectric effect. Although Millikans measurements resulted rather quickly in a basicagreement between the theory and experimental reality, for a long while he only wanted

    to admit that this confirmation was nothing more than the quantitative confirmation of the

    photoelectric equivalence, especially since yet another precision method for determining

    Plancks active quantum had been found, thanks to his work. The light quantum hypothesis

    itself seemed to him fully unacceptable until the early 1920s.

    Even Max Planck himself, after all the father of quantum theory and one of Einsteins

    strongest supporters, who once called Einstein his most important discovery, said in 1913

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    during a laudatory address for Einsteins election to membership in the Prussian Academy that

    Einsteins contributions to physics had been so great that the scientific world should not be

    too critical if he once in a while has shot past the mark, like for instance with his hypothesis

    about light quanta. . . . Because without the ability to take risks, even the most exact natural

    science cannot introduce any true advances [11].It is an irony of the history of science that Einsteins light quantum theoryhis discovery

    of the law of the photoelectric effectwon him the Nobel Prize for physics in 1921. This

    had less to do with the scientific foresight of the selection committee than with the fact that

    Alfred Nobels testament specifically preferred effects to theories, and Einsteins general

    theory of relativity seemed to be insufficiently confirmed and in addition was considered highly

    controversial [12].

    The final turning point in the general acceptance of Einsteins light quanta and therefore

    the waveparticle dual nature of light was of course not provided by the Nobel Prize

    committee, but by the discovery of the Compton effect in 1922, and his convincing theoretical

    interpretation based on Einsteins light quantum hypothesis shortly afterwards [13]. Arnold

    Sommerfeld, who had witnessed this during a trip to America, wrote about it to Niels Bohr:

    The most interesting thing I experienced in terms of science in America was the workof Arthur Compton in St Louis. After this, the wave theory of x-rays will have to be

    abandoned [14].

    After it became clear to Einstein in the spring of 1905 that the problem of thermal radiation

    in thermodynamic equilibrium not least made the concept of empty space insupportable, other

    ideas in this regard in which he had engaged for quite some time, especially relating to the

    electrodynamics of moving bodies, suddenly gained new significance. Letters from the years

    between 1899 and 1903 show that Einstein was continually absorbed in these problems [4].

    He drafted experiments to analyse the changes in the speed of light in a moving body or

    the relative movement of the earth through the ether. But in trying to bring his ideas into reality,

    he ran into insuperable problems that even with the intensive study of relevant textbooks and

    other scientific literature could not be overcome. Special attention was given to the work of

    the Dutch physicist Hendrik Antoon Lorentz on electrodynamics, which had climaxed in the

    well-known electron theory.This theory, based on the commonly held notion of a stationary ether, still managed to

    bring processes taking place in frames of reference in motion, with the help of auxiliary space

    and time coordinates, into agreement with the experience of systems at rest. This reduction

    held within it the seed of the so-called Lorentz transformations between moving frames of

    reference.

    Like Plancks derivation of his law of radiation, the derivation of Lorentzs theory from

    classical physics proved complicated and connected with problematic additional assumptions.

    Similarly to what he had done with his revolutionary work on light quanta, Einstein here

    cut the Gordian knot in that he came up with a completely new interpretation of Lorentzs

    transformation equations.

    From the perspective that Einstein had gained during his research, the building blocks

    of Lorentzs theory appeared in a new light. While for Einstein the ether, which was animportant basis of Lorentzs work, had become questionable, Lorentzs conclusions about

    the relationship between electromagnetic measurements taken in moving frames of reference

    seemed, in contrast, quite reliable. These conclusions were in agreement with the postulate that

    in measuring electromagnetic and optical phenomena, it was impossible to tell the difference

    between a framework at rest and a framework moving at a uniform speed. Still, Lorentz had

    only been able to reach these conclusions, which had been proven by observation, with the

    help of additional assumptions. He had therefore to introduce an auxiliary variable for time

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    into his description of physical processes in moving frameworks that was different from time

    in a system at rest. In addition, Lorentz assumed that the length of bodies is shortened in

    the direction of their movement through the etherthis was the only way to explain why the

    MichelsonMorley experiments had failed to detect any movement of the earth through the

    ether.The results of these deliberations added up to an expansion of the relativity principle

    already at the core of classical mechanics to electromagnetic and optical phenomena. Einstein

    had expected such an expansion since he first considered a strange asymmetry in classical

    electrodynamics: the interaction between a magnet and a conductor moving towards each

    other was described differently depending on which was considered to be at rest, but the

    physical effectelectricity induced in the conductoris always the same.

    For Einstein, the success of Lorentzs electrodynamics was essentially a confirmation of

    the principle of relativity. But it was simpler not to embark on the difficult path Lorentz

    had adopted in order to see this confirmation, especially since his starting point of an etheric

    medium was, from Einsteins perspective, highly questionable. It seemed much more plausible

    to make the principle of relativity the starting point, thereby setting Lorentzs theory, so to

    speak, on itsfeet instead of itshead. Einstein clearly hoped that hisanalogy of thermodynamics,which apart from its physical details was based on simple principles, would lead him to a theory

    that was independent of the composition of electromagnetic phenomena, i.e., whether they

    were waves or particles.

    Thus he searched for the solution to the problem of the electrodynamics of moving bodies

    on an entirely new and more profound level, whichsupported by his philosophical readings,

    especially in a discussion with his friend Michele Besso in May of 1905he ultimately found

    in kinematics: the doctrine of space and time. While new variables for time and length played

    a supporting role in Lorentzs theory, they took on fundamental significance in Einsteins

    deliberations. It was a kind of Copernican turning point in the formation of basic principles.

    What consequences did Lorentzs electron theory have for the kinematic behaviour of

    bodies in motion? How would it be possible to determine whether systems in motion behaved

    in the way Lorentz had asserted? It was questions such as these that led Einstein to the

    problem of simultaneity in two systems moving with uniform velocity with respect to eachother, thereby causing him to take the crucial step that would eventually solve this problem.

    In order to determine simultaneity he developed a method that was based on calibrating

    two clocks separated by distance through light signals. This method disclosed a certain amount

    of arbitrariness in the determination of simultaneity in systems moving towards each other,

    because the concept was at first only defined in one frame of reference. This arbitrariness

    could be eliminated in two ways. One could assume that the determination of simultaneity

    with Einsteins method would lead to the same results regardless of motion of the framework;

    that would make it possible to conclude the validity of the concept of absolute time, which

    was the basis for conventional physics. Alternatively one could introduce the hypothesis that

    it was not time but the speed of light that would remain the same regardless of the motion

    within the framework.

    Einstein chose the latter hypothesis, despite counterintuitive consequences like therelativity of simultaneity. It allowed him to derive the main results of Lorentzs

    electrodynamics based on two simple principles, that of relativity and the non-classical

    principle of the constancy of the speed of light. This in turn made it possible for him to

    extend the scope of the principle of relativity from classical mechanics over the entirety

    of physics, whereby the classical Galileo transformations between frameworks in motion

    were replaced by Lorentz transformations. With its seemingly paradoxical consequences like

    shortening of length and time dilatation, or the so-called twin paradox, these transformations

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    guaranteed that all inertial systems are physically equal, i.e., the laws of physics are retained

    in these transformations and the speed of light remains constant.

    In a supplementary paper Does the inertia of a body depend on the energy it contains?

    Einstein in the fall of 1905 derived another consequence of his theory of special relativity.

    In relation to this, he wrote to his friend Conrad Habicht: One other consequence ofelectrodynamic work has occurred to me. The principle of relativity in relation to Maxwells

    equations demands that mass is a direct measurement of the energy of a body; that light carries

    mass. A noticeable decrease in mass must then occur in the case of radium. The thought is

    funny and infectious; but whether God is laughing and has led me by the nose, I do not know

    [15].

    As we know today, God was not leading Einstein by the nose at all, rather he was leading

    Einstein to the most famous physical equation of all time as well as to his scientific fame and

    popularity.

    Einsteins special relativity theory from 1905 received the form in which it is usually

    expressed today from Hermann Minkowski, Einsteins Zurich mathematics professor. In

    1908, he gave it the form of four-dimensional spacetime geometry. This four-dimensional

    formulation tied in with the further development of the relativity theory by Max von Laue,Arnold Sommerfeld and other physicists, in whose frameworks more fundamental conceptual

    insights, like, for instance, the role of the four-dimensional energy impulse tensor, provided

    material for the understanding of inertia and eventually gravitation as well.

    Another breakthrough of Einsteins annus mirabilis was his analysis of Brownian motion.

    This work also has a hidden connection to the more famous relativity and quantum theory

    papers. It is rooted just as deeply as the others in Einsteins occupation with questions of

    statistical physics. While the controversy was still raging among physicists at the turn of the

    century about the legitimacy of assuming the existence of atoms in order to explain thermal

    phenomena (as well as other physical processes), Einstein turned the issue on its head and

    instead questioned whether classical thermodynamics could correctly describe the movement

    of particles suspended in fluid.

    From the point of view of thermodynamics, such particles should behave like macroscopic

    bodies, which after a certain amount of time reach equilibrium. From the point of view ofthe kinetic theory of heat, these particles differ from real atoms in size only. When they are

    exposed to the buffeting of their smaller siblings, they should pick up on the thermal movement

    and thereforeas had, in fact, been observedbegin moving in random motion at a constant

    rate.

    The laws of mechanics were used to calculate the average rate of motion of the particles

    as related to their share of the thermal energy, but it became clear that it was impossible to

    reconcile the calculated rate of motion of the suspended particles with the observed rate. In

    his work on Brownian motion, Einstein analysed this phenomenon as a statistical process, a

    stochastic process.

    Thus Einstein used the strange, in-between world of fluctuations, the best example of

    which is Brownian motion, to bridge the macrocosm of our everyday environment and the

    microcosm of atoms and moleculesin order to make the latter more comprehensible. Brownianmotion became the key to proving the existence of atomseven though their characteristics

    no longer fit into the classical image of moving particles.

    Remarkably, it was Einsteins atomic interpretation of Brownian motion that was the first

    to be understood and accepted. Its experimental verification, which was from 1908 advanced

    by the French physicist Jean Perrin, was an impressive and crucial confirmation of the atomic

    structure of matter, and contributed immensely to the final acceptance of atomic theory in

    physics.

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    Figure 4. Schematic forborderline problems.

    (This figure is in colour only in the electronic version)

    Einsteins essential conviction of atomic theory, which he gained at the very latest in his

    early student days, must also be seen as the connecting element in all his key works of 1905,

    because in all these works it played a crucial heuristic role.

    In this context, however, we can see yet another connective element among these works.

    Einsteins works during his annus mirabilis are all concerned with problems of a certain

    kind; they go beyond the divisions among mechanics, electrodynamics and thermodynamics,

    the three main areas of classical physics, and therefore can be characterized as borderline

    problems (see figure 4).

    Mechanics, the oldest discipline in physics, was long considered the basis upon which

    all physical phenomena could be explained. Besides mechanics, electrodynamics and

    thermodynamics had established themselves since the middle of the nineteenth century as

    relatively independent areas with their own theoretical foundations. Their reduction to

    mechanics was attempted, but this proved in the end to be both impossible and unnecessary.Instead, a whole series of problems emerged that affected at least two of the three domains of

    classical physics.

    The problem of thermal radiation in thermal equilibrium was just such a borderline

    problem between thermodynamics and electrodynamics, that of the electrodynamics of moving

    bodies bordered both electrodynamics and mechanics, and Brownian motion lay between

    thermodynamics and mechanics. It is no coincidence that the scientific revolution Einstein

    initiated in 1905 was sparked by just such borderline problems. Because these borderline

    problems were not isolated, they were, so to speak, problems that dealt with the overlap zones

    among the continents of classical physics, where highly integrated knowledge systems meet.

    Since this degree of integration came not least from model concepts like the notions of the

    ether and the atom, it is not surprising that the inner conceptual conflicts of classical physics

    were replaced in these model concepts. Against this background we can understand how the

    seemingly specialized works of Einstein during his miraculous year of 1905 ultimately led to

    the elimination of the ether and the acceptance of the existence of atoms, and also led to the

    surprising conclusion that light is not a wave after all, but has a quantum nature.

    References

    [1] For a documentary edition of the papers (with comments), see Stachel J et al (ed) 1989 Collected Papers of

    Albert Einstein (CPAE) vol 2 (Princeton, NJ: Princeton University Press)

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    [2] For Einsteins biography see Folsing A 1997 Albert EinsteinA Biography (New York: Viking)

    [3] Stachel J (ed) 1987 Collected Papers of Albert Einstein (CPAE) vol 1 (Princeton, NJ: Princeton University

    Press) pp 2889

    [4] Renn J and Schulmann R 1992 Albert EinsteinMileva MaricThe Love Letters (Princeton, NJ: Princeton

    University Press)

    [5] Einstein A 1993 Letters to Solovine, 19061955 (New York: Citadel Press) p 142

    [6] Kuhn T S 1978 Black-Body Theory and the Quantum Discontinuity 18941912 (Oxford: Clarendon)

    [7] Stachel J (ed) 1989 Collected Papers of Albert Einstein (CPAE) vol 2 (Princeton, NJ: Princeton University

    Press)

    [8] Lenard P 1944 Wiss. Abh. Lpz. 3 251 ff

    [9] Einstein A, Born M and Born H 1971 The correspondence between Albert Einstein and Max Born and Hedwig

    Born from 1916 to 1955, with commentaries by Max Born The BornEinstein Letters (New York: Walker)

    p 88

    [10] EinsteinA, PodolskyB andRosen N 1935Can quantum-mechanical description of physicalreality be considered

    complete? Phys. Rev. 47 77780

    [11] Planck M 1975 Wahlvorschlag fur Albert Einstein, Berlin 12.6.1913 Physiker uber Physiker I ed C Kirsten and

    H-G Korber (Berlin: Akademie) p 202

    [12] Friedman R M 2001 The Politics of Excellence: Behind the Nobel Prize in Science (New York: Freeman)

    p 119 ff

    [13] See Stuewer R 1975 The Compton Effect: Turning Point in Physics (New York: Science History Publications)

    [14] Eckert M and Marker K (ed) 2004 A Sommerfeld: Wissenschaftlicher Briefwechsel vol 2 (Berlin: Diepholz)

    p 144 (A Sommerfeld to N Bohr, 21 January 1923)

    [15] Klein M J et al (ed) Collected Papers of Albert Einstein (CPAE) vol 5 (Princeton, NJ: Princeton University

    Press) p 33 (A Einstein to C Habicht, Bern, June 1905)

    [16] Renn J (ed) 2005 Einsteins Annalen Papers (Weinheim: Wiley)