Atoms and Nuclei

We now understand light as vibrations of electric and magnetic fields which somehow propagate through space. Obviously, we need to discuss the nature of light further, but before we do so, we should first ask, “What is matter?” The Greek philosopher Empedocles (Chap. 2) had many interesting ideas on the workings of nature. For example, he envisioned that light travels at a finite (very large) speed, which gained acceptance only much later. He also proposed the idea that matter is made of four elements — earth, water, air, and fire. It was the mainstream view through the Middle Ages up to the seventeenth century.

Robert Boyle was critical of the four-element theory. He thought that matter consists of different kinds of particles and that gross matter was composed of clusters of particles and that chemical changes resulted from the rearrangement of the clusters. In the Sceptical Chymist (1661), the Irishman criticized alchemists who tried to make gold from other elements. He defined an element as a substance which could not be further broken down by any means, thereby originating chemistry as a scientific subject.