Our story has so far been a tale of five great scientific revolutions. The first, initiated by Galileo and largely completed by Newton, brought mechanics and the concept of universal gravitation. The second, pioneered by Carnot and carried on by Mayer, Joule, Helmholtz, Thomson, Clausius, Gibbs, and Nernst, gave us thermodynamics. In the third, Faraday and Maxwell introduced the field concept and constructed a theory of electromagnetism. The work of Clausius, Maxwell, Boltzmann, and Gibbs in the fourth revolution, called statistical mechanics, opened the door to molecular physics. And the fifth revolution, Einstein's relativity theory, rebuilt our view of space, time, and gravitation.
This part of the book starts one more account of scientific revolution. The story begins conveniently in 1900 and twenty-five years later arrives at a new science, now called “quantum theory,” “quantum mechanics,” or “quantum physics,” which probes further the microworld of molecules, atoms, and subatomic particles. A usage note: to distinguish pre- and postquantum physics I will now use the adjectives “classical” for the former and “quantum” for the latter, as in “classical mechanics” and “quantum mechanics,” and “classical physics” and “quantum physics.” (“Quantal” would be a better partner for “classical,” but that term is rarely used.)
In its early stages, the quantum revolution had three great leaders: Max Planck, whose disciplined insights gave the first glimpse of what was coming; Albert Einstein, who became as deeply committed to this intellectual adventure as to relativity theory; and Niels Bohr, who brought the revolution to its greatest crisis. Each of the three pioneers first faced the task of reconciling classical physics with the strange conclusions forced by the new physics, and each in his own way failed. Planck and Bohr tried to dispel the mysteries by building the new physics partially into the framework of the old. Einstein quickly accepted the most drastic features of the new