ABSTRACT
For physicists, the twentieth-century, and especially its first half, was the heroic age. Modern physics may conveniently be said to have begun in 1900, with Max Planck's quantum theory. Before Planck there was the 'classical physics' of Galileo and Newton, which described the workings of objects no smaller than an atom, and no larger than, say, the solar system. Ernest Rutherford studied the radioactive ore pitchblende and pronounced that the radiation coming from it could not possibly come from chemical reactions. Albert Einstein showed that brownian motion was proof of the existence of atoms; light was composed of particles and produced the special theory of relativity. The existence of photons was proved by whole series of experiments by the American Robert Milliken and also the Englishman Arthur Compton independently proved every detail of Einstein's hypothesis. According to the standard model, there are three forces at work inside an atom: the electromagnetic force; the strong atomic force and weak atomic force.
