runs backward. In other words, time can be treated as a variable, t, and the laws remain valid when $-t$ is substituted for $t$. This is referred to by some (e.g. [@smolin2013]) as spatialized time, because we can travel in both directions in it, as we can in space. Spatialized time is a conceptualization and representation of natural time, whereas natural time is the time in which we and the world exist, independently of any representation of it. Spatializing time is thus a way of eliminating natural time by substituting a model for the real thing. The physics of spatialized time is essentially a timeless physics, since we have access to the entire corpus of physical laws in the same sense that we have access to the entire body of timeless mathematics.

The fact that time can be treated as a variable permits the spectacularly accurate predictions that flow from physical theory: the equations can be solved to show the state of the system as a function of time, and thus the state at any particular time, whether past, present or future. This physics is in a deep sense deterministic. This is true even of quantum physics, where, as Prigogine 