 For mathematical reasons not relevant here, it turns out to be possible to take a given model spacetime and perform a mathematical operation called a “hole diffeomorphism” h* on it; the diffeomorphism’s effect is to shift around the matter content T and the metric g relative to the continuous manifold  M.[5]  If the diffeomorphism is chosen appropriately, it can move around T and g after a certain time t = 0, but leave everything alone before that time. Thus, the new model represents the matter content (now h* T) and the metric (h*g) as differently located relative to the points of M making up space-time. Yet, the new model is also a perfectly valid model of the theory. This looks on the face of it like a form of indeterminism: GTR’s equations do not specify how things will be distributed in space-time in the future, even when the past before a given time t is held fixed. See  Figure 5: