 For our purposes, the defining feature of a manifold that is a Newtonian spacetime is that the temporal interval between any two points or events in the spacetime, \(p\) and \(q\), is a well-defined quantity. This quantity is well-defined in that it does not depend upon point of view, reference frame, coordinate system or “observer”. This quantity, then, is absolute in the sense of being frame- or observer-independent. (In the special theory of relativity the temporal interval between two distinct spacetime points fails to be absolute in this sense.)