No one conception of time emerges from a study of physics. One's understanding of physical time changes as science itself changes, either through the development of new theories or through new interpretations of a theory. Each of these changes and resulting theories of time has been the subject of philosophical scrutiny, so there are many philosophical controversies internal to particular physical theories. For instance, the move to special relativity gave rise to debates about the nature of simultaneity within the theory itself, such as whether simultaneity is conventional. Nevertheless, there are some philosophical puzzles that appear at every stage of the development of physics. Perhaps most generally, there is the perennial question, Is there a "gap" between the conception of time as found in physics and the conception of time as found in philosophy?

One can understand all of these changes and controversies as...