 One way to try to eliminate the arrow of time at the fundamental level is to make use of certain interpretations of statistical mechanics inspired by Ludwig Boltzmann’s work. Imagine the history of the universe as a long timeline, but with no indication of which end of the time line represents the first moment of time and which end represents the last moment. It follows from certain interpretations of statistical mechanics that there is a physical quantity, the entropy of the universe, that will be relatively low at one end of the timeline and relatively high at the other end and will always increase as you move from the former end of the timeline to the latter. (More carefully, the entropy will almost always increase or at least stay constant.) The thought, then, is that we might be able to reduce the arrow of time to this entropy gradient. Earlier moments of time are just moments of time when the entropy of the universe is lower.