[pdonis]

Penrose's The Emperor's New Mind contains a good layman's discussion of it. (It also contains a good example of a layman's work that makes the same mistake the article under discussion here does: even after going to all the trouble to explain in detail how the three regions I described work, and how "now" slicings, unlike the three regions I described, are frame-dependent and don't have physical meaning, he then makes an invalid argument for the "block universe" viewpoint that depends on ignoring the three regions and treating "now" slicings as though they do have physical meaning. It's an excellent example of how even experts of the stature of Penrose can get things wrong.)