ABSTRACT
Isaac Newton gave us a theory about how objects move, forces interact, and gravity operates. Centuries later, Albert Einstein transformed physics, first with his special theory of relativity (SR) and then with his general theory of relativity (GR). SR tells us how objects move when they are unaffected by gravity; GR generalises the account to include gravity. In their standard formulations, perdurantism and endurantism presuppose that persistence is a matter of existing somehow or other at more than one moment in time. Faced with the fact that SR does not isolate a privileged perspective on simultaneity, some presentists have hoped to find a privileged reference frame in GR. Cosmologists using GR believe that the universe is expanding, and that the distribution of matter everywhere is becoming less dense as a result of this expansion. Metaphysicians have long argued about whether space and time are entities in their own right, or whether they are mere abstractions from concrete objects and events.
