Quantum_ Einstein, Bohr and the Great Debate About the Nature of Reality - Manjit Kumar [73]
Having renounced his German citizenship in 1896 and taken Swiss citizenship five years later, Einstein was surprised to learn that he was a German after all. Whether he liked it or not, the needs of the Weimar Republic meant that Einstein officially had dual nationality. 'By an application of the theory of relativity to the taste of readers,' Einstein had written in November 1919 in an article for the London Times, 'today in Germany I am called a German man of science and in England I am represented as a Swiss Jew. If I come to be regarded as a bête noire, the descriptions will be reversed and I shall become a Swiss Jew for the Germans and a German man of science for the English!'87 Einstein might have recalled these words had he been at the Nobel banquet and heard the German ambassador propose a toast that expressed the 'joy of my people that once again one of them has been able to achieve something for all of mankind'.88
Bohr rose after the German ambassador and gave a short speech as tradition demanded. After paying tribute to J.J. Thomson, Rutherford, Planck and Einstein, Bohr proposed a toast to the international cooperation for the advancement of science, 'which is, I may say, in these so manifoldly depressing times, one of the bright spots visible in human existence'.89 Given the occasion, it is understandable that he chose to forget the continuing exclusion of German scientists from international conferences. The next day Bohr was on firmer ground as he gave his Nobel lecture on 'The structure of the atom'. 'The present state of atomic theory is characterized by the fact that we not only believe the existence of atoms to be proved beyond a doubt,' he began, 'but we even believe that we have an intimate knowledge of the constituents of the individual atoms.'90 Having given a survey of the developments in atomic physics of which he had been such a central figure in the past decade, Bohr conclude his lecture with a dramatic announcement.
In his Göttingen lectures, Bohr had predicted the properties that the missing element with an atomic number of 72 should possess, based upon his theory of the arrangement of electrons in atoms. At exactly that time a paper was published outlining an experiment performed in Paris that confirmed a long-standing rival French claim that element 72 was a member of the 'rare earth' family of elements that occupied slots 57 to 71 in the periodic table. After the initial shock, Bohr began having serious doubts about the validity of the French results. Fortunately his old friend Georg von Hevesy, who was now in Copenhagen, and Dirk Coster devised an experiment to settle the dispute about element 72.
Bohr had already left for Stockholm by the time Hevesy and Coster completed their investigation. Coster telephoned Bohr shortly before his lecture and he was able to announce that 'appreciable quantities' of element 72 had been isolated, 'the chemical properties of which show a great similarity to those of zirconium and a decided difference from those of the rare earths'.91 Later called hafnium after the ancient name for Copenhagen, it was a fitting conclusion to Bohr's work on the configuration of electrons within atoms that he had begun in Manchester a decade earlier.92
In July 1923, Einstein gave his Nobel lecture on the theory of relativity as part of the 300th anniversary celebrations of the founding of the Swedish city of Göteborg. He broke with tradition by choosing relativity, when he had been awarded the prize 'for his attainments in mathematical physics and especially for his discovery of the law of the photoelectric effect'.93 By limiting the award of the prize for the 'law', the mathematical formula that accounted for the photoelectric effect, the committee deftly sidestepped endorsing Einstein's controversial underlying physical explanation – the light-quantum. 'In spite of its heuristic value, however, the hypothesis of light-quanta, which is quite irreconcilable with so-called interference phenomena, is not able to