Abstract
``It is utterly beyond our power to measure the changes of things by time. Quite the contrary, time is an abstraction at which we arrive through the changes of things." Ernst Mach [1]. *What* change? Three answers to this are `any change' (Rovelli), `all change' (Barbour) and my argument here for the middle ground of a `sufficient totality of locally relevant change' (STLRC) giving a generalization of the astronomers' ephemeris time. I then use STLRC as a selection principle on existing and new approaches to the Problem of Time in Quantum Gravity. Emergent Jacobi-Barbour-Bertotti time can be interpreted as arising from a STLRC, resolves the classical Problem of Time and has an emergent semiclassical counterpart as regards facing the QM Problem of Time.
Edward Anderson