keithl wrote:Both quantum mechanics (Lamb said "quantum electrodynamics") and turbulence are well understood physical theories, but the individual instances are unpredictable from the starting conditions. "Why?" is an easy question - otherwise, the God+Universe system would be deterministic, and vulnerable to the halting problem.
What do you mean by "deterministic, and vulnerable to the halting problem"? There are non-deterministic Turing Machines and they are not any different with regards to the halting problem. And besides, the halting problem is only relevant to theoretical machines with truly infinite memory, i.e. not anything that actually exists in the physical universe.