There is nothing outside of the universe. The universe is defined as the totality of all things.

The concept of time is an abstraction of change. Time merely measures change.

Consistent with these definitions, space, time, and motion are only defined by the relationships between entities in the universe. A theory that respects this concept is called "background independent". In contrast, theories in which space and time serve as a fixed, unchanging background are called "background dependent". Newtonian physics and all quantum theories devised prior to loop quantum gravity are background dependent. This has been one of the primary impediments to creating a quantum theory of gravity. General relativity is background independent. It describes the gravitational field and specifies how the gravitational field and the geometry of the universe change as the relationships between the entities comprising the universe change. The inconsistency between the nature of space and time in general relativity and standard quantum field theories is one of the main theoretical motivations for constructing a quantum theory of gravity.