4d space time

In relativity, spacetime combines three spatial dimensions with one time dimension. An event is specified by where and when it occurs, and different observers can measure space and time differently while agreeing on spacetime relationships.

How it works

Time is not simply another spatial direction: it enters the geometry with a different role and causal structure. The speed of light connects spatial and temporal measurements in the theory.

Example or application

A meeting can be described by three coordinates for location and one for time. A spacetime diagram can plot one spatial direction against time to show an object’s path as a worldline.

Scope and limits

Four-dimensional spacetime is a mathematical model used in relativity. It does not mean that people can move freely through time as they move through space.

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