Classical physics

Quantum theory was produced roughly between 1900 and 1925; it changed our view of the Universe in a revolutionary way. Such is the central preoccupation of this book. Relativity was another revolutionary theory produced between 1905 and 1916; it is less central here. The clear implication of these statements is that, prior to 1900, there was an established body of theory that was widely successful and was thought to provide final answers to fundamental physical questions. This body of theory is known as classical physics.

The above is a simplified account of the development of physics over the last few hundred years. There is a good deal of truth in it. By 1900, Newton's Laws of mechanics had been established for over 200 years; they had been overwhelmingly successful in describing a huge range of phenomena, both terrestrial and in the solar system. They were held to be among the greatest human achievements, indeed the very greatest strictly scientific achievement, and practically a direct revelation of divine intent, and by 1900 it seemed unthinkable that they could be challenged.

The same could not quite be said of electromagnetism, an area of physics that encompasses electricity, magnetism and, as will be seen later in this chapter, optics. By 1900, what we now take to be the complete and final theory of classical electromagnetism, that of James Clerk Maxwell, was over 30 years old, and the discovery of radio waves by Heinrich Hertz which was acknowledged to confirm the theory, more than ten years old.