Classical Theory Quotes (2 quotes)
The kinetic concept of motion in classical theory will have to undergo profound modifications. (That is why I also avoided the term “orbit” in my paper throughout.) … We must not bind the atoms in the chains of our prejudices—to which, in my opinion, also belongs the assumption that electron orbits exist in the sense of ordinary mechanics—but we must, on the contrary, adapt our concepts to experience.
Letter to Niels Bohr (12 Dec 1924), in K. von Meyenn (ed.), Wolfgang Pauli - Wissenschaftliche Korrespondenz (1979), Vol. 1, 188. Quoted and cited in Daniel Greenberger, Klaus Hentschel and Friedel Weinert, Compendium of Quantum Physics: Concepts, Experiments, History and Philosophy (2009), 615.
The vital act is the act of participation. “Participator” is the incontrovertible new concept given by quantum mechanics. It strikes down the term “observer” of classical theory, the man who stands safely behind the thick glass wall and watches what goes on without taking part. It can’t be done, quantum mechanics says.
In Charles W. Misner, Kip S. Thorne, John Archibald Wheeler, 'Beyond the Edge of Time', Gravitation (1973), Part 3, 1217.