From 1922 to 1927 Wiener traveled to Europe practically every summer. He found these trips intellectually refreshing and enjoyed the company of interesting people he met. During the 1920s his work was much better appreciated in Europe than in America, and he got considerably more encouragement from mathematicians abroad than he did from those at home, most of whom hardly knew him. During these visits, Wiener worked. The words: “The kind of work I do can be done anywhere. Why should I be less capable of reflecting about my problems on the Potsdam bridge than at home?” are Einstein’s (cf. P. Frank {F4, p. 147}), but could have been Wiener’s. His ideas on quantum mechanics were formed in the course of such travels and participation in seminar discussions in Europe.
From 1922 to 1927 Wiener traveled to Europe practically every summer. He found these trips intellectually refreshing and enjoyed the company of interesting people he met. During the 1920s his work was much better appreciated in Europe than in America, and he got considerably more encouragement from mathematicians abroad than he did from those at home, most of whom hardly knew him. During these visits, Wiener worked. The words: “The kind of work I do can be done anywhere. Why should I be less capable of reflecting about my problems on the Potsdam bridge than at home?” are Einstein’s (cf. P. Frank {F4, p. 147}), but could have been Wiener’s. His ideas on quantum mechanics were formed in the course of such travels and participation in seminar discussions in Europe.
Abstract There is a certain similarity in the early lives of Planck and of Heisenberg [1,2]. Both had fathers who were professors at the University of Munich, both visited the Maximilians-Gymnasium in Munich, and both went to see a professor in Munich to seek advice for their studies. We have mentioned at the beginning of the Prologue how Jolly in vain tried to dissuade Planck from studying physics. Heisenberg, in his autobiographic book [3], which is devised as a series of conversations, tells us of a similar experience. In the autumn of 1920, when he was about to enter the university, his first choice was mathematics. He wanted not only to do course work but also learn about problems of current interest. This, he thought, he could do best by participating in a professor’s seminar usually reserved to advanced students and Ph.D. candidates. He asked for an interview with Lindemann , the most distinguished mathematician in Munich, who was famous for having proved that the number π is transcendental. But the old professor and the young student found no understanding, partly because Lindemann’s dog noisily interfered. The result was that Heisenberg opted for theoretical physics and went to ask Sommerfeld to be admitted to his seminar. Sommerfeld agreed. At that time Pauli, only a year older than Heisenberg, was already actively doing research under Sommerfeld. The two young men became life-long friends.
‘Quantum mechanics is very impressive. But an inner voice tells me that it is not yet the real thing. The theory produces a good deal but hardly brings us closer to the secret of the Old One’. These views were contained in a letter written by Albert Einstein to Max Born in December 1926. Though the following year would see the completion of work on the theoretical foundation of the modern physics of atoms and particles, Einstein was never to change his judgement and remained firmly convinced that ‘this business […] contains some unreasonableness’. He was unwilling to sacrifice his own ideas as to the cognitive scope of science even in the face of the important results being achieved by the new theory. To the undeterministic findings of quantum mechanics he opposed his belief in the ‘possibility of giving a model of reality, a theory, that is to say, which shall represent events themselves and not merely the probability of their occurrence’. For this reason he chose to live with the isolation of his scepticism and dissent, ironically accepting the reputation as a obstinate heretic that he had won over the years among his colleagues, and worked to the end on his own research programme to develop a unified field theory of rigorously causal nature. As is generally known, Einstein carried on a strong scientific and philosophical dispute with the defenders of the so-called official interpretation of quantum mechanics.
Born's reaction In his reminiscences, Born recounted his memories of these exciting days (Born, 1978): ‘Meanwhile Heisenberg pursued some work of his own, keeping its idea and purpose somewhat dark and mysterious. Towards the end of the summer semester, in the first days of July 1925, he came to me with a manuscript and asked me to read it and decide whether it was worth publishing … He added that though he had tried hard, he could not make any progress beyond the simple considerations contained in his paper, and he asked me to try myself, which I promised … His most audacious step consists in the suggestion of introducing the transition amplitudes of the coordinates q and momenta p in the formulae of mechanics … I was most impressed by Heisenberg's considerations, which were a great step forward in the programme which we had pursued … After having sent Heisenberg's paper to Zeitschrift für Physik for publication, I began to ponder about his symbolic multiplication, and was soon so involved in it that I thought the whole day and could hardly sleep at night. For there was something fundamental behind it … And one morning … I suddenly saw the light: Heisenberg's symbolic multiplication was nothing but matrix calculus, well known to me since my student days from the lectures of Rosanes at Breslau.’
In 1925-26, the late Max Born gave two sets of lectures at M.I.T., one on the structure of the atom, the other on the lattice theory of rigid bodies. Problems of Atomic Dynamics contains the text of both sets.What gives this volume its remarkable interest is just those dates: 1925-26. This must have been, by all accounts, the headiest period in twentieth-century physics, and Max Born was one of the leaders of the ferment. As Norbert Wiener remembers, When Professor Born came to the United States [for these lectures in 1925] he was enormously excited about the basis Heisenberg had just given for the quantum theory of the atom.These lectures represent perhaps the most vivid written record of the transition between the old quantum theory of Bohr, and the new theory. At the time I began this course of lectures, Born writes, first paper on the quantum theory had just appeared. Here his masterly treatment gave the quantum theory an entirely turn. The paper of Jordan and myself, in which we recognized the matrix calculus as the proper formulation of Heisenberg's ideas, was in press, and the manuscript of a third paper by the three of us was almost completed.Even as the lecture series progressed, Born became familiar with results, which he introduced into his presentation: Pauli's fourth quantum number, Dirac's formalism, his own work on a general operational calculus. And yet, in spite of the conditions of revolutionary changes in physics that year -- in which established ancien regime principles were collapsing almost monthly -- the theory is developed with a cool elegance and with a formal completeness which may be regarded as a limiting case of its current state. These lectures represent the foundations of quantum theory, and they have withstood the tests of time -- the tests of more than forty years of experimental evidence.