Duality of Nature

Newton’s and Schrödinger’s equations both describe the motion. Newton’s laws describe the motion of macroscopic objects and are the foundation of classical physics. Schrödinger’s equations describe the motion of quantum particles giving the solutions in a form of wave functions and probabilities. This chapter is all about the quantum particle–wave duality and the explanations on the quantum laws with examples and description, of experimental evidence.

Light and matter are both single entities, and the apparent duality arises in the limitations of our language. It is not surprising that our language should be incapable of describing the processes occurring within the atoms, for, as has been remarked, it was invented to describe the experiences of daily life, and these consist only of processes involving exceedingly large numbers of atoms. Furthermore, it is very difficult to modify our language so that it will be able to describe these atomic processes, for words can only describe things of which we can form mental pictures, and this ability, too, is a result of daily experience. Fortunately, mathematics is not subject to this limitation, and it has been possible to invent a mathematical scheme – the quantum theory – which seems entirely adequate for the treatment of atomic processes; for visualisation, however, we must content ourselves with two incomplete analogies – the wave picture and the corpuscular picture. (Quantum Theory, 1930), Werner Heisenberg (1901–1976)