 Modern physical theories are often formulated in a language that permits one to express a variety of different views with respect to time and its relation to space. One can, for example, formulate the basic ideas of classical (that is, Newtonian) physics, the special theory of relativity, and the general theory of relativity in this language. For a brief introduction to manifolds and the spacetime view, see the section on  modern spacetime theories  in the entry on  the hole argument  in this Encyclopedia. For more detail with minimal technical demands the reader should see the first four chapters of Geroch (1978) or the more demanding chapter 2 of Friedman (1983).