The Penguin History of the World

Meanwhile, after his work on quanta, Einstein had published in 1905 the work for which he was to be most widely, if uncomprehendingly, celebrated, his statement of the theory of relativity. This was essentially a demonstration that the traditional distinctions of space and time, and mass and energy, could not be consistently maintained. It therefore constituted a revolution in science, although it took a long time for the implications to be thoroughly absorbed. Instead of Newton’s three-dimensional physics, Einstein directed men’s attention to a ‘space–time continuum’ in which the interplay of space, time and motion could be understood. This was soon to be corroborated by astronomical observation of facts for which Newtonian cosmology could not properly account, but which could find a place in Einstein’s theory. One strange and unanticipated consequence of the work on which relativity theory was based was his demonstration of the relations of mass and energy, which he formulated as E = mc², where E is energy, m is mass and c is the constant speed of light. The importance and accuracy of this theoretical formulation was not to become clear until much more nuclear physics had been done. It would then be apparent that the relationships observed when mass energy was converted into heat energy in the breaking up of nuclei also corresponded to his formula.

While these advances were absorbed, attempts continued to rewrite physics, but they did not get far until a major theoretical breakthrough in 1926 finally provided a mathematical framework for Planck’s observations and, indeed, for nuclear physics. So sweeping was the achievement of Schrödinger and Heisenberg, the two mathematicians mainly responsible, that it seemed for a time as if quantum mechanics might be of virtually limitless explanatory power in the sciences. The behaviour of particles in the atom observed by Rutherford and Bohr could now be accounted for. Further development of their work led to predictions of the existence of new nuclear particles, notably the positron, which was duly identified in the 1930s. The discovery of new particles continued. Quantum mechanics seemed to have inaugurated a new age of physics.

By mid-century much more had disappeared in science than just a once-accepted set of general laws (and in any case it remained true that, for most everyday purposes, Newtonian physics was still all that was needed). In physics, from which it had spread to other sciences, the whole notion of a general law was being replaced by the concept of statistical probability as the best that could be hoped for. The idea, as well as the content, of science was changing. Furthermore, the boundaries between sciences collapsed under the onrush of new knowledge made accessible by new theories and instrumentation. Any one of the great traditional divisions of science was soon beyond the grasp of a single mind. The conflations involved in importing physical theory into neurology or mathematics into biology put further barriers in the way of attaining that synthesis of knowledge that had been the dream of the nineteenth century, just as the rate of acquisition of new knowledge (some in such quantities that it could only be handled by the newly available computers) became faster than ever. Such considerations did nothing to diminish either the prestige of the scientists or the faith that they were mankind’s best hope for the better management of its future. Doubts, when they came, arose from other sources than their inability to generate an overarching theory as intelligible to lay understanding as Newton’s had been. Meanwhile, the flow of specific advances in the sciences continued.