ABSTRACT
In the last chapter we saw how Newton established the laws and methods of classical physics, and so founded modern science. There was still much debate about the philosophical justification of what he had done, but the agreement of his calculations with observations was so impressive that all opposition was silenced. The Newtonian method was generally seen as the paradigm of scientific endeavour, and scientists in other areas applied it in their own work, often with indifferent success. Attempts were even made to use it in such areas as economics, sociology and psychology. Henceforth physics was set on its road of continual progress, and the physicists knew that now they could go on with their work without bothering any more about what the philosophers said. For the most part this attitude was well justified, but in times of crisis the philosophical issues inevitably come again to the fore. During the eighteenth century important advances were made, particularly
in celestial mechanics by Laplace and in dynamics by Lagrange. Ever more accurate calculations were made, almost all of them agreeing with the observations to high accuracy. Chemistry was further developed by Lavoisier and many of the chemical elements were identified. Here we are principally concerned with the state of physics at the end of the nineteenth century, on the threshold of the new physics of the twentieth century. It was during the nineteenth century that science ceased to be the preserve of
a few university professors and some enthusiastic amateurs and entered the mainstream of public life. The ever-increasing momentum of the Industrial Revolution brought together the traditional skills and empirical knowledge of the craftsmen and the knowledge of the scientists, and the result of that marriage was a plethora of inventions and new industrial processes. Thousands of factories poured out a wide range of products, textiles, ironware, pottery and china that altered the lifestyles of the whole population in an unprecedented way. The Great Exhibition of 1851 publicized a vast range of new products, and showed the world what could now be done. Chemistry, and later on physics, were recognized as legitimate subjects for university education, and produced professional scientists in ever-increasing numbers. It was an era brimming over with confidence and looking hopefully to the
future. With the aid of science and technology, it was confidently believed that all problems could be solved and all obstacles to human development overcome. Inevitably this mood spread beyond science itself and many embraced scientism as the new religion. The events of the twentieth century have somewhat dampened that enthusiasm. In the nineteenth century classical physics came to maturity. Our under-
standing of the physical world developed apace, and much previous knowledge
was unified and given mathematical expression. The different forms of energy were identified and related to each other, and electricity and magnetism were unified by Maxwell’s equations of the electromagnetic field. The chemists established the atomic theory and the physicists showed how spectra can be measured to give information on atomic structure. Classical thermodynamics gave a macroscopic description of thermal phenomena and this was related to a microscopic description by statistical mechanics. Taken as a whole, classical physics provided a detailed description of a vast
range of phenomena, and many thought that it was essentially complete. At the end of the century, there remained a few puzzling phenomena and some philosophical difficulties, but this was not enough to dampen the prevailing optimism. In the space of a few years, however, the discovery of the quantum opened the way to a new world, and classical physics was seen as a limited account of some realms of phenomena. Some old puzzles were solved and replaced by new ones, and most of the philosophical difficulties are still with us, though often in different forms. Some of the main achievements of nineteenthcentury physics are summarized in the following sections (Basalla et al., 1970; Knight, 1986).
