Seeing Things Move

Abstract

On the classical model, the history of the physical universe is constituted by its states at each instant. The evolving magnitude of any quantity will be given, in terms of selected units of time and of that quantity, by a function from real numbers on to real numbers. Given this classical model of physical reality, there can be no way of avoiding the conception of what is impinging on the senses of any one individual, human or animal, at any one instant. We are therefore left with the problem how we are to explain in these terms our actual experience of observing things that are moving or changing. I suggest that we stand in need of some different model of physical reality, in which time would not be modelled on the classical continuum of real numbers. It would not be composed of durationless instants, but, rather, by overlapping temporally extended intervals, representable by open intervals in the line of rational numbers.

Itamar Pitowsky† (1925–2011)