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.