iSoul In the beginning is reality.

# Timelines and placelines

Events may be ordered in various ways (see here). Events ordered by time form a time line, or timeline, which is:

1. a linear representation of important events in the order in which they occurred.
2. a schedule; timetable.

This may be generalized to the following definition:

A time line is an ordering of events by time or duration.

For example, below is a time line of ancient Greece:

Events in 3D space are ordered by a common time line. Such a time line is like taking the successive radii of concentric spheres emanating from a common point, the origin event, with radii measured by duration, and defining an equivalence class of events occurring at the same duration from the origin.

In the physical sciences, a common timeline based on clocks is employed in which all events are ordered by time. This raises questions of simultaneity, which are addressed in relativity.

Itineraries are commonly ordered by time, but sometimes it is better to order an itinerary by place, such as the series of cities for a journey. The ordering of events by place or length may be called a placeline.

For example, below is a placeline of the (closed) Avontuur Railway in South Africa (click to enlarge):

It shows events (stops) and their distances along a line. The American Automobile Association provides members with triptiks, maps that show a placeline for their trip:

Minard’s famous map of Napoleon’s Russian Campaign of 1812 shows the advance and retreat as a placeline of a series of battles:

Below is a placeline of a Project Mercury flight:

Events in 3D time are ordered by a common placeline. Such a placeline is like taking the successive radii of concentric spheres emanating from a common point, the origin event, with radii measured by distance, and defining an equivalence class of events occurring at the same distance from the origin.