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1905: Einstein’s paper revolution

01 Oct 1998

Einstein's Miraculous Year: Five Papers That Changed the Face of Physics
(ed) John Stachel
1998 Princeton University Press 198pp £14.95/$19.95hb

Outside it is a warm May evening, as two friends sit deep in discussion in a coffee house in Berne. “Besso, you must help me, I think I am going mad. How is it even thinkable that a light ray could overtake two reference systems with exactly the same speed if one is moving, the other at rest? Yet, if the symmetries we observe in electromagnetic phenomena are to make any sense, somehow it must be so. But how is it possible?”

How would you or I have responded? Probably with something like, “Albert, this is silly. Go home. Get some rest.” It is to Michele Besso’s enduring credit that he represses that first reaction and sits loyally by Einstein. He even offers suggestions as Einstein – his friend and co-employee (second-class) at the patent office – goes over and over the same ground, trying one desperate ploy after another.

How the rest of that turbulent night passed cannot be known. However, we have as its fruit a manuscript entitled Electrodynamics of Moving Bodies, which was completed at the end of June 1905 and dispatched to Max Planck in Berlin. We also have Einstein’s own recollection years later of a brief encounter with Besso in the patent office the following morning. Simply, and without greeting or preamble, Einstein informed his friend: “Thank you. I’ve completely solved the problem.”

Perhaps only someone who knew the dice were rolling his way could have found the courage to take on this supreme challenge. In fact, it was the climax of a surge of confidence and productivity without parallel in the history of science. It led Einstein to write five papers in that one year of 1905, each of which alone would have secured his reputation as one of this century’s leading scientists. Those five jewels – originally published in German in the journal Annalen der Physik – are collected here, newly translated into English.

Although we do not have the exact date of the May breakthrough, it was quite probably no more than a few days after Einstein completed his paper on Brownian motion. On 30 April he also completed his PhD dissertation, which was published later that year. It showed how to obtain Avogadro’s number and the sizes of ions in solution from measurements of osmotic pressure and the coefficient of diffusion. Long undervalued compared with his more spectacular contributions from 1905, it nowadays outstrips all of them in terms of the annual number of citations.

In March there were two papers, one on Avogadro’s number, and another that bears the innocent-looking title: On a Heuristic Point of View Concerning the Production and Transformation of Light. In its first three paragraphs, the battle-lines are drawn by a master of stagecraft. The wave theory of light, Einstein writes, “has proved itself superbly in describing purely optical phenomena and will probably never be replaced by another theory”. Having summarized the compelling evidence in favour of the wave theory, he then goes on to propose the completely opposite hypothesis, namely that “the energy of light is discontinuously distributed”.

Einstein advocates this view partly because the wave theory seems to lead to contradictions when applied to certain emission and absorption phenomena (such as the photoelectric effect), but mainly because he is dissatisfied with the “profound difference” that existed between the discrete corpuscular description of matter and Maxwell’s continuous-field description of radiation. This sort of reasoning must surely have struck any reader of the time as metaphysical if not downright frivolous, so deeply entrenched was the wave theory of light as the crowning achievement of 19th-century physics.

This was the only one of Einstein’s 1905 papers that he described as “revolutionary”. It was also the one that his contemporaries – Planck in particular – found hardest to swallow. In fact, Einstein advanced the idea with considerable caution and reserve, and it was not until his radiation papers of 1917 that he felt confident enough to assign a momentum to these energy quanta. Although Compton’s scattering experiments of 1923 finally convinced physicists of the reality of these “speeding bullets” – it was only in 1926 that they were given the name “photons”.

Einstein’s five papers were all written within a period of four months, but their incubation extended over a much longer time. He had brooded over the peculiar symmetries of electromagnetic phenomena for some seven years. And although his “apprentice” papers of 1902-4 were flawed, they played a crucial role in Einstein’s intellectual development. Independently of Gibbs, he had arrived in these papers at some of the key results of statistical mechanics – in particular his favourite toy, the beloved fluctuation formulae. These results led him from one profound insight to another over the next twenty years, culminating with the first intimation of the wave-like character of matter (independently of de Broglie) in 1924.

In these excellent new translations of Einstein’s papers, the economy and freshness of Einstein’s style come through with undiminished force. There is the occasional jolt, as when one finds that his thrice-familiar formula, E = mc2, appeared originally as m = L/V2. Somehow, this does not have quite the same aura. John Stachel, the founding editor of Einstein’s collected papers, provides an admirable and non-technical general introduction, while each paper is preceded by a clear and detailed commentary that places it in the context of the physics of its day and of Einstein’s own development.

To re-read these papers is to relive perhaps the most dramatic year in the history of physics. In the words of his biographer, Albrecht Fölsing: “Never before and never since has a single person enriched science by so much in such a short time as Einstein did in his annus mirabilis.”

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