Time is a slippery fish. We live in it. We are defined by it. Yet we have no notion of whether time is a dimension in and of itself or something created only by the events that occur within it and given shape by their ordering. Our everyday lives are perceived not as the unwinding of a reel but as a series of discrete events, such that, with the piling on of further events, it becomes hard to determine in what order they occurred. Unless you take the trouble to put your holiday snaps in an album as soon as you return, it’s quite hard, without some external referent, such as a date stamp, to place a collection of loose photos in chronological order.

Making sense of snapshots taken in geological time is orders of magnitude more difficult – first, because few of the elements are immediately familiar, and second, because the scale of time involved is so great as to defy human comprehension. In his engaging new book, Otherlands, Thomas Halliday addresses both difficulties. He deals with the latter by drawing an analogy between time and space. While inviting us to study the strange dawn