n.
Measured or measurable period.
More broadly, it is a continuum that lacks spatial dimensions. Philosophers have sought an understanding of time by focusing on the broad questions of the relation between time and the physical world and the relation between time and consciousness. Those who adopt an absolutist theory of time regard it as a kind of container within which the universe exists and change takes place, and believe that its existence and properties are independent of the physical universe. According to the rival relationist theory, time is nothing over and above change in the physical universe. Largely because of Albert Einstein , it is now held that time cannot be treated in isolation from space (see space-time ). Some argue that Einstein's theories of relativity vindicate relationist theories, others that they vindicate the absolutist theory. The primary issue concerning the relation between time and consciousness is the extent, if any, to which time or aspects of time depend on the existence of conscious beings. Events in time are normally thought of in terms of notions of past, present, and future, which some philosophers treat as mind-dependent; others believe that time is independent of perception and hold that past, present, and future are objective features of the world. See also geologic time, Greenwich Mean Time , standard time , Universal Time .