19 June 2013
Venue: Maths 103
This talk will propose that spacetime is an evolving block universe, with a future boundary that extends into the future as time progresses. This is required in order that it make sense to say the Galaxy is 13.7 billion years old today, and will be older tomorrow, in universe where the future is indeterminate because of quantum uncertainty, which intera alia affects structure formation in the early universe. The issue then arises as to how one determines the surfaces of proper time characterising the "present" at each instant. I propose these are determined by integrating proper time along the Ricci eigenlines since the start of the universe. These are unique because the real universe is nowhere empty. One can use an ADM coordinate system that realises this prescription. Instantaneity is irrelevant to this construction: it is a psychological construct that has no physical connotations.