Places and events

A place is a location within space. An event is a location within time. Past, present, and future are adjectives that modify place or event. We may speak of places in the past or of events in the past. Here indicates the present place. Now indicates the present event. The locus of events in the past are called the past. The locus of events in the future are called the future. Note that every physical body has its own past, present, and future.

We can turn all that around: Space is the locus of places, and time is the locus of events. Usually, space means the locus of places one could have been to or could go to, and time is the locus of events one could have experienced or could experience. In that sense, space and time are potentials. The here and now are actual. Space and time are the context for places and events. In particular, space and time are the context for here and now.

The order of places is a 3D ordering since three independent components are needed to locate each place. The order of events is a 3D ordering since three independent components are needed to locate each event. A spherical wave front is dimensionally symmetric so it is effectively 1D in space and time. If a spherical wave front is used as a standard measure for space or time, then such space or time is reduced to 1D. Time is commonly treated this way but it is also possible to treat space as 1D.

Displacement is the difference between two places and dischronment is the difference between two events; they are expressed as vectors between the two places or events. Distance is the length of a displacement. Duration is the length of a dischronment. The length along a path of motion in space is called arc length or travel distance. The length along a path of motion in time is called arc time or travel time.