David Mermin sayscorrectly that the spacetime of special relativity does not by itself describe our experience of Now. He also notes that we are “complex, extended entities.” A natural conclusion is that a notion of Now is not built into the fundamental laws of physics. Rather, it arises from the particular way our brains are organized to process temporal information—a way that is consistent with the fundamental laws but not an inevitable consequence of them. Reference 1 provides simple models of how that works within familiar classical physics, including special relativity.
That conclusion is supported by models of observing systems that do not have a past, present, and future way of organizing temporal information and that are also consistent with the fundamental laws.
