The concept of 'now' is rather well defined in classical physics, but as we have seen in a previous question , Heisenberg's Uncertainty Principle prevents us from assigning BOTH a specific place and time to any event in spacetime.
All events are in actuality, small fuzzy regions rather than mathematical points with zero size.
This means that 'now' has a size, and this size is determined by the condition that DE x DT Copyright 1997 Dr. Sten Odenwald Return to Ask the Astronomer .