Ernest Rutherford

This Anchor paperback is a biography of the physicist Ernest Rutherford. The author is himself a noted physicist and metallurgist. He worked with Rutherford as a student and associate in perhaps the most exciting days of Rutherford’s many: in the years just before 1914, in Manchester, after Rutherford had discovered the atomic nucleus. Moseley was there, showing that the characteristic X-rays of the elements provided a direct measurement of nuclear charge and atomic number, and thus “calling the roll” of the elements Niels Bohr was also in Manchester, facing the implications of the nuclear atom for atomic structure, a structure unintelligible in terms of Newtonian dynamics, and calling for such new descriptions as stationary states, transitions between them, and quantum conditions determining the energy of the states in terms of the electron’s mass and charge, and the quantum of action that “governed” the atom. The author is a polished and experienced lecturer; he is a poet; he is an historian of science. Few biographers can have as engaging and noble a subject.

The biography takes us from Rutherford’s birth, on a small homestead near the village of Nelson on the South Island of New Zealand, to the interment of his ashes, sixty-six years later near Newton’s tomb in Westminster Abbey. This is an intellectual biography, following Rutherford’s arguments, experiments, and conclusions. There is little in it that takes Rutherford away from physics. We learn almost nothing of his wife and his marriage, though there are quotations from his early letters to Mary Newton in New Zealand, telling of his professional progress, and particularly of the prospects of an income adequate to sustain marriage. His daughter appears only once, in a word of her tragic death. There is a good deal of Rutherford’s honors, which are explained with great care, for an audience ignorant of the meaning of the Order of Merit, of the Nobel Prize in Chemistry, of a peerage. We learn of Rutherford’s love of gardening only because it was a small accident in his garden that led, prematurely, obscurely, perhaps unnecessarily, to his own death. There is nothing of the Rutherford home which, to so many of the younger generation, was to be almost a second home. But of Rutherford the physicist there is a sustained, scrupulous, and extraordinarily full account.

In two respects Andrade takes great care to help the lay reader. He describes in detail the physics laboratories of Rutherford’s youth: the meagreness of the equipment, its crankiness and inconvenience, the lack of money, of electricity, and of almost all that we take for granted. There is a plate showing Rutherford with the equipment in which, late during the first world war, he first disintegrated the nucleus of nitrogen. It is hard to make the equipment out in the plate, but I have seen it in the Cavendish Laboratory; it is to our present-day eyes unbelievably small, homemade, and simple; one can tell in the plate that it hardly occupies the space between the two sides of Rutherford’s open coat. Andrade is also very careful to explain the intellectual background of the times, and above all the arguments that Rutherford used in devising and interpreting experiments. It is always hard, in writing for a lay audience, to avoid overexplaining the obvious and taking the truly difficult for granted; but Andrade comes close to avoiding this. With these thoughtful precautions, he tells the heroic story.

Rutherford himself spoke of his own simplicity; and Bohr, in a great tribute to him thirty years ago, used the same word. Bohr used often to say that he was not marked so much by intelligence as by an extraordinary common sense. He was indeed marked, which surely Bohr took for granted, by a superlative instinct for discovering novelty, for knowing what things were worth looking at, that might produce deep discoveries, and what things were trivial, and to be left to others. As Andrade wisely quotes from Kohlrausch on Faraday, “He smells truth.” Rutherford was also extraordinarily forthright and straight of tongue and pen, and extraordinarily warm, lighting and bringing life. As his teacher at Canterbury College in Christchurch wrote, in recommending him for a fellowship at the Cavendish Laboratory in Cambridge, “Personally Mr. Rutherford is of so kindly a disposition and so willing to help other students over their difficulties that he has endeared himself to all…”

Rutherford’s first works he undertook in New Zealand. They were based on Hertz’s discovery of electromagnetic waves. When he came to Cambridge, J. J. Thomson, then Cavendish Professor and Director of the Cavendish Laboratory, who was in a few years to discover the electron, took Rutherford as his collaborator in work with X-rays, recently discovered by Roentgen. Still before the turn of the century, and before Rutherford’s departure for a professorship at McGill, Becquerel discovered radioactivity, and Rutherford knew that the exploration and understanding of this was to be his vocation.

In the years at McGill, Rutherford sorted out the three radiations from natural radioactive substances, such as uranium and radium. Their true nature did not become clear at once, but Rutherford seems to have understood it long before he could prove it. He suspected, and then he knew, that the alpha rays were the nuclei of helium; but the proof did not come until 1908, when he had gone to Manchester. He also, working with Soddy, was able to establish the existence of several families of naturally radioactive materials, identifying parent and product through many generations, showing how the emission of the radiations changed the chemical properties of the atoms, and encountering the “chemically inseparable substances” which were to turn out to be, when the nuclear atom was under stood, substances with the same nuclear charge or atomic number, but different nuclear mass and properties. For all of this, he won the Nobel Prize in Chemistry: a transmutation, he remarked, “more rapid than any I have studied,” from physicist to chemist.

Rutherford’s greatest discovery came in Manchester. In 1909 he and his colleague Geiger thought that a young man called Marsden should have an experimental problem to work on, and Rutherford suggested that Marsden see whether alpha rays passing through matter were ever scattered through a large angle. Rutherford did not think that there would be. The hard atoms of Lucretius and the nineteenth-century atomists had turned out to be quite soft; alpha particles passed through them quite easily, with minute deflections, and so did fast electrons, beta rays, or cathode rays. Since the discovery of the electron, it had been thought that an atom was an extended distribution of positive charge, in which somehow electrons reposed, and occasionally oscillated to emit light, or rearranged themselves to form molecular compounds. When Geiger came to Rutherford a few days later, he said, “We have been able to get some of the alpha particles coming backwards,” and Rutherford wrote. “It was quite the most incredible event that has ever happened to me in my life. It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you.” A year and a half later, Greiger tells us. “One day Rutherford, obviously in the best of spirits, came into my room and told me that he now knew what the atom looked like and how to explain the large deflections of alpha particles. On the very same day I began an experiment to test the relations expected by Rutherford between the number of scattered particles and the angle of scattering.” What Rutherford had seen is that there must be in the atom something massive enough to turn the alpha particle back, and with a strong enough force. This was the atomic nucleus, occupying a million millionth of the atom’s volume, with almost its whole mass, and with a charge equal to the atomic number, and thus to the number of electrons in the neutral atom.

Before leaving Manchester, and despite heavy work on antisubmarine devices, Rutherford, deserted except for his laboratory assistant, made one other discovery: that alpha particles could transmute the nuclei of light atoms, and in particular knock a proton out of nitrogen to form an isotope of oxygen.

After Rutherford’s days at Manchester, the problem of the structure of atoms could not be evaded, and the mutability of the atomic nucleus itself opened wide the study of its structure and properties. Rutherford accepted the Cavendish Professorship and the direction of the Cavendish Laboratory in Cambridge. In his Bakerian Lecture in 1920 he predicted with strong and persuasive arguments the existence of a heavy isotope of hydrogen and, more important, the existence of the neutral counterpart of the proton, the neutron, and the importance of this particle in inducing the transmutation of nuclei. The heavy hydrogen and the neutron were discovered eleven and twelve years later, the neutron by Chadwick in close association with Rutherford. That same year saw the first use of artificially accelerated particles, in this case protons. To bring about nuclear reactions, Cockcroft and Walton had built an unsophisticated but effective particle accelerator in the Cavendish Laboratory. Rutherford’s cup was very full.

In the years that followed, it became clear that Rutherford’s anticipation was just. Neutrons did indeed easily and copiously change atomic nuclei. The most violent of these changes was induced by Fermi and his collaborators in Rome, when they caused the fission of uranium; but neither Fermi nor anyone else knew that that was what they had done until after Rutherford’s death. He thus did not expect any large-scale use of nuclear reactions. That large-scale thermonuclear reactions occur in the stars was indeed then thought very likely; but there was no word of the atomic reactor or the atomic bomb. It has been a not infrequent conjecture among my colleagues that, had Rutherford lived to see these developments, the course of history might have been rather different, perhaps rather better.

This reviewer has read Andrade’s book with admiration and with gratitude, reliving many great things, learning many others. Andrade has clearly addressed his book to an audience with little prior knowledge; it is difficult for me to judge whether the excitement and the warmth that are to be found in it will really be found there by the readers to whom it is addressed. There are many references to Rutherford’s manner and his qualities: his forthrightness, his boisterousness, his generosity, his warmth. I doubt that these adjectival evocations will make the laboratory, the colleagues, the great man live; I hope that the story of what Rutherford wrought will.

There is one trait of this book that would not be expected from what I have so far written: it is very sad. I understand this only in part. It is a book of mourning, not only for Rutherford, but for a man and a world which the author clearly regards as remote almost beyond words, and quite beyond recall.