The arrow of time and the nature of spacetime

•The direction of time is an arrow from the start of the universe to the present day.•The arrow of time is the local direction of time for physical events.•It agrees with the direction of time because of special initial conditions.•It cascades down from large scales to microphysics through contextual effects.•It then flows up to macrostructures as complexity emerges.

This paper extends the work of a previous paper (Ellis, 2013) on the flow of time, to consider the origin of the arrow of time. It proposes that a ‘past condition’ cascades down from cosmological to micro scales, being realized in many microstructures and setting the arrow of time at the quantum level by top-down causation. This physics arrow of time then propagates up, through underlying emergence of higher level structures, to geology, astronomy, engineering, and biology. The appropriate spacetime picture to view all this is an Evolving Block Universe ‘EBU’, that recognizes the way the present is different from both the past and the future. This essential difference is the ultimate reason the arrow of time has to be the way it is.