Nico van Kampen

"The solution of the measurement problem is twofold. First, any observation or measurement requires a macroscopic measuring apparatus. A macroscopic object is also governed by quantum mechanics, but has a large number of constituents, so that each macroscopic state is a combination of an enormous number of quantum mechanical eigenstates. As a consequence the quantum mechanical interference terms between two macroscopic states virtually cancel and only probabilities survive. That is the explanation why our familiar macroscopic physics, concerned with billiard balls, deals with probabilities rather than probability amplitudes."

"Second, in order that a macroscopic apparatus can be influenced by the presence of a microscopic event it has to be prepared in a metastable initial state—think of the Wilson camera and the Geiger counter. The microscopic event triggers a macroscopically visible transition into the stable state. Of course this is irreversible and is accompanied by a thermodynamic increase of entropy."

"The scandal is that there are still many articles, discussions, and textbooks, which advertise various interpretations and philosophical profundities. In the seventeenth century Cartesians refused to accept Newton’s attraction because they could not accept a force that was not transmitted by a medium. Even now many physicists have not yet learned that they should adjust their ideas to the observed reality rather than the other way round."