From Charles Goodwin
The article on causal set theory was fascinating, and may even be the beginnings of a “theory of everything” (4 October, p 36). However, the one thing it did not address was the question on the cover – “What makes time flow?”
Whether one has a theory in which Planck volumes evolve, or one in which world lines criss-cross space-time (as in relativity), one is still dealing with a “block universe” in which, if one could view it from outside time, nothing would change. I could see nothing in the article that justified the view that causal set theory has reintroduced the philosophically and physically dubious notion of time as “flowing”.
Dunedin, New Zealand
