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See Interval and segment.

A space-time interval is a quantity characterizing the relation between two events separated by a spatial distance and a time duration. In special relativity theory the square of an interval is


where $c$ is the velocity of light, $x_i,y_i,z_i$ are the space coordinates and $t_i$ are the corresponding points in time (for more details, see Minkowski space).

In general relativity theory one considers the interval between two infinitesimally-close events:


where $dx^i$ is the infinitesimal difference of the space-time coordinates of these events and $g_{ik}$ is the metric tensor.


A space-time interval with $s^2>0$ is called a time-like space-time interval, and one with $s^2<0$ is called a space-like space-time interval.


[a1] D.F. Lawden, "An introduction to tensor calculus and relativity" , Methuen (1962)
[a2] R.K. Sachs, H. Wu, "General relativity for mathematicians" , Springer (1977)
[a3] E. Tocaci, "Relativistic mechanics, time, and inertia" , Reidel (1985) pp. Sect. A.II.1.4
How to Cite This Entry:
Interval. Encyclopedia of Mathematics. URL:
This article was adapted from an original article by A.B. Ivanov (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article