Linked from
The 15 pages that link to Spacetime interval, each with the reason it gives.
Special relativityRelated: It is the frame-independent measure underlying relativistic geometry.
Lorentz transformationRelated: Its invariance is the defining constraint on the transformation.
SpacetimeRelated: It measures separation in a way that all inertial observers agree on.
Proper timeRelated: Proper time is obtained from the spacetime interval along a timelike path.
Four-vectorRelated: Four-vector norms use the same invariant spacetime geometry.
Twin paradoxRelated: Its geometry underlies the path-dependent proper time compared in the paradox.
Spacetime diagramRelated: Its sign classifies separations as timelike, lightlike, or spacelike.
Poincaré groupRelated: Poincaré transformations preserve this quantity for every pair of events.