BBC History of the World. A timeline where time is in the depth (z) axis. From BBC History of the World website.Which way should time go?
The screen, like a piece of paper, has only two dimensions. Illusions of depth, along a dimension orthogonal to the two real dimensions, can be created using a variety of visual cues – J.J. Gibson counted thirteen cues that our perceptual/cognitive system seems to use to infer depth, many of which can be used pictorially to fake depth on a two-dimensional surface (discussed in Chapter 3 of my 2002 PhD [download 6.5MB PDF file]).
This BBC example is a timeline based on things: it is a history of the world told through objects. Time is represented by the illusory third dimension with, rather unusually, the most distant time being shown as nearest to the viewer. At any given date, contemporaneous objects arrange themselves in a circle around the centre-point.
A nice feature is that information on users’ objects can be uploaded and is fully integrated with the original set of objects contributed by museums and other organisations. I have uploaded a picture of my copy of Priestley’s Description of a Chart of Biography. It seemed right to put a pioneering historical timeline in the timeline of historic objects.