Dreams of a Final Theory: The Scientist's Search for the Ultimate Laws of Nature

by Steven Weinberg

Physicists continued to wrangle over the interpretation of quantum mechanics for years after they had become used to solving the Schrödinger equation. Einstein was unusual in rejecting quantum mechanics in his work; most physicists were simply trying to understand it. Much of this debate went on at the University Institute for Theoretical Physics in Copenhagen, under the guidance of Niels Bohr.* Bohr focused particularly on a peculiar feature of quantum mechanics that he called complementarity: knowledge of one aspect of a system precludes knowledge of certain other aspects of the system. Heisenberg’s uncertainty principle provides one example of complementarity: knowledge of a particle’s position (or momentum) precludes knowledge of the particle’s momentum (or position).†