Newton distinguishes between absolute and relative places. Both types of places endure through time and may be occupied by various objects at various times. But unlike absolute places, each relative place stands in fixed spatial relations with one or more reference objects. Relative plac-es with independent reference objects (e.g. a ship and the earth) may move relative to one another. Relative places, not absolute places, are used to locate objects and track their movements in common-sense reasoning and in disciplines such (...) as biology, engineering, and geology. The purpose of this paper is to develop a formal theory for reasoning about relative places and their changing relations to both other places and to material objects. (shrink)