A new proof of the impossibility of a universal quantum-classical dynamics is given. It has at least two consequences. The standard paradigm “quantum system is measured by a classical apparatus” is untenable, while a quantum matter can be consistently coupled only with a quantum gravity.

Freeman Dyson has questioned whether any conceivable experiment in the real universe can detect a single graviton. If not, is it meaningful to talk about gravitons as physical entities? We attempt to answer Dyson’s question and find it is possible concoct an idealized thought experiment capable of detecting one graviton; however, when anything remotely resembling realistic physics is taken into account, detection becomes impossible, indicating that Dyson’s conjecture is very likely true. We also point out several mistakes in the literature (...) dealing with graviton detection and production. (shrink)

The assumption that a classical gravitational field interacts with a quantum system is shown to lead to violations of either momentum conservation or the uncertainty principle, or to result in transmission of signals faster thanc. A similar argument holds for the electromagnetic field.

An attempt is made to give a coherent account of the logical essence of the Copenhagen interpretation of quantum theory. The central point is that quantum theory is fundamentally pragmatic, but nonetheless complete. The principal difficulty in understanding quantum theory lies in the fact that its completeness is incompatible with external existence of the space—time continuum of classical physics.