End of Century Reflections on Planck's Quantum Theory and Philosophy

Anil Rajimwale

The quantum revolution in physics of the 20th century has completely transformed the nature not only of physics and science in general, but also of philosophy and our worldview. Quantum revolution began in the early 19th century with the discovery of ‘quantum’ (plural ‘quanta’) principally by Max Planck, and with theories and discoveries in the field of relativity, linked inseparably with the name of Albert Einstein. Max Planck came across the quanta when he was studying what is known as the ‘blackbody radiation’. In classical physics in particular and the classical world in general, there was no serious problems with objects, objectivity and ontology. In classical physics, particles and fields have an existence independent of the observer. In broader view, everything, the world, exists independent of the observer and of the consciousness. The first quantum-mechanical theories on electron in mid-1920s did not take into account the effect of velocity of light, and were therefore non-relativistic.

Martin Strauss

Peter Coles

The development of kinetic theory in the latter part of the 19th century represented the culmination of a mechanistic approach to natural philosophy that had begun with Isaac Newton two centuries earlier. In 1905, however, Albert Einstein single-handedly overthrew the underlying basis of Newtonian mechanics with the introduction of his special theory of relativity. This led to a theory he was never comfortable with: quantum mechanics. The birth of quantum mechanics partly arose from the developments of kinetic theory and statistical mechanics. This chapter looks at the contributions of James Clerk Maxwell and Max Planck to quantum mechanics, quantum probability, waves and particles, and the use of quantum theory by modern physicists to describe matter on all scales.

Mendel Sachs

th century ‐ the theory of relativity and the quantum theory. Based on these developments, it is interesting for the future of physics that when examined in terms of their conceptual and mathematical bases, these theories are incompatible. On the other hand, each of these theories requires an incorporation of the other to proceed toward its completion. This is the dilemma we face in these early decades of the 21 st century: Which of the two theories should be abandoned and which should be maintained?[1] Albert Einstein was the leading proponent of the theory of relativity and its philosophy, Niels Bohr was the leading proponent of the quantum theory and its philosophy ‐ as fundamental theories of matter.[2] Because of the incompatibility of the mathematical and conceptual bases of these theories, in fundamental terms, as will be discussed in detail later on, they cannot peacefully coexist. But because aspects of each of these theories are necessary to complete the other, the form of the accepted theory must be generalized in such a way that it yields, as a mathematical approximation, the form of the theory whose concepts are abandoned. This is an appeal to the wellknown principle of correspondence. Bohr appealed to this principle in showing how the formal expression of quantum mechanics goes smoothly into the structure of classical mechanics as the fundamental unit of action ‐ Planck’s constant h ‐ approaches zero, compared with the values of classical action. Similarly, the principle of correspondence reveals how Einstein’s relativistic mechanics goes smoothly

F. S. MARVIN