In recent years there has been renewed discussion of the problem of temporal becoming (Maxwell 1985,1988; Dieks 1988; Stein 1991). The theme of this paper is that these discussions, timely and interesting as they are, do not go deeply enough into the question. I would like to suggest that a certain way of thinking about simultaneity, which as far as I know was first sketched in a science fiction novel by Robert A. Heinlein (1956), opens up a set of possibilities that deserve serious consideration.
More precisely, I will address the following question: is there anything in the formal structure of Minkowski spacetime which corresponds to our intuitive albeit imprecise notion of a global “present”? It is generally assumed that because of the relativity of optical simultaneity the answer to this question is, resoundingly, no.