Completely mind-blowing... Wolfram presents highlights from his big fat NKS book: starts very simple with cellular automata, but eventually rule 110 becomes a universal computation machine which can emulate Ricci tensor from relativity and Feynman diagrams in quantum physics. Imagine an experiment where the universe is a Turing machine. The discussion of his Principle of Computation Equivalence is important for the limits of current science and the foundations of mathematics. Computational irreversibility shows how nature is undecidable in Godel's sense, and thus is unpredictable... we can only observe how complex things will evolve :-) - Adriano