History [of views of time]

The idea of representing time graphically like space has a long history—and was used for example by Nicholas Oresme in the mid-1300s. In the 1700s and 1800s the idea of position and time as just two coordinates was widespread in mathematical physics—and this then led to notions like "travelling in time" in H. G. Wells's 1895 *The Time Machine*. The mathematical framework developed for relativity theory in the early 1900s (see page 1042) treated space and time very symmetrically, leading popular accounts of the theory to emphasize a kind of fundamental equivalence between them and to try to make this seem inevitable through rather confusing thought experiments on such topics as idealized trains travelling near the speed of light.

In the context of traditional mathematical equations there has never been much reason to consider the possibility that space and time might be fundamentally different. For typically space and time are both just represented by abstract symbolic variables, and the formal process of solving equations as a function of position in space and as a function of time is essentially identical. But as soon as one tries to construct more explicit models of space and time one is immediately led to consider the possibility that they may be quite different.