Space

The definition of space in physics is contentious. Various concepts used to try to define space have included:

• the structure defined by the set of "spatial relationships" between objects
• a manifold defined by a coordinate system where an object can be located.
• the entity that stops all objects in the universe from touching one another

In classical physics, space is a three-dimensional Euclidean space where any position can be described using three coordinates. relativistic physics examines spacetime rather than space; spacetime is modeled as a four-dimensional manifold.

Philosophical questions concerning space include: Is space absolute or purely relational? Does space have one correct geometry, or is the geometry of space just a convention? Historical Eminences who have taken sides in these debates include Isaac Newton (space is absolute), Gottfried Leibniz (space is relational), and Henri Poincaré (spatial geometry is a convention).

Two important thought-experiments connected with these questions are: Newton's bucket argument and Poincaré's disc-world[?].

See also: Spherical coordinates, Cartesian coordinates, Philosophy of physics

Space is the relatively empty parts of the Universe, outside the atmospheres of planets. It is sometimes called "outer space" to distinguish it from airspace and terrestrial locations.

See also: space science; Astronomy and Astrophysics

The term "inner space" has sometimes been used to describe the contents of the human mind.

See also: psychology

In mathematics, a space is a set, usually with some additional structure.

For examples, see Euclidean space, vector space, normed vector space, Banach space, inner product space, Hilbert space, topological space, uniform space, and metric space.

In some orthographies, a space is a blank area that serves as punctuation to provide interword separation.