Does time flow? It will be shown in this chapter that if the spacetime structure of the world has a certain branched dynamic form, then time flows. In addition to the flow and direction of time, two issues in quantum mechanics, those of non-locality and the definition of ‘measurement’, are shown to be illuminated by the hypothesis that the world has the spatio-temporal form described. I call the form the branched model, and the interpretation of quantum mechanics to which it gives rise I call the branched interpretation.

Objective time flow

The branched model is a four-dimensional spacetime model in the shape of a tree, each branch of which is a complete Minkowski manifold in which are located objects and events. The trunk represents the past, the first branch point is the present, and the branches constitute the set of all physically possible futures. The scheme is shown in figure 1.

Of the many possible futures which split off at the first branch point, one and only one is selected to become part of the past. The unselected branches vanish, so that the first branch point moves up the tree in a stochastic manner and the tree ‘grows’ by losing branches. This progressive branch attrition is what in the model constitutes the flow of time.

Suppose for example that 1000 lottery tickets have been sold to 1000 different purchasers. Then at the time of the draw, assuming the procedure is completely fair, there will be at least 1000 different kinds of branch at the first branch point: branches on which A wins, branches on which B wins, etc.