Spacetime diagram

A graph that represents events in space and time, often using worldlines to show the motion of objects and the paths of light.

Event (relativity): A localized occurrence assigned spatial and temporal coordinates in a reference frame. Each plotted point represents an event with a time and place.
Minkowski diagram: A spacetime diagram for special relativity, typically showing one space dimension and time with light paths at 45 degrees. It is the standard diagram for displaying relativistic spacetime geometry.
Relativity of simultaneity: The dependence of whether spatially separated events are simultaneous on the observer's inertial frame. Different frame axes intersect the diagram's event structure at different times.
Minkowski spacetime: The flat four-dimensional spacetime model of special relativity, with a metric combining space and time. The diagram depicts selected dimensions of this underlying spacetime.
Worldline: A curve in spacetime tracing the history of an object or observer. Worldlines turn an object's motion into a path on the diagram.
Lorentz transformation: The equations relating space and time coordinates measured in inertial frames moving uniformly relative to one another. It explains how changing frames tilts the axes without changing light speed.
Twin paradox: A special-relativity scenario in which twins following different paths through spacetime reunite having aged by different amounts. The twins' distinct worldlines make their different elapsed proper times visible.
Penrose diagram: A conformal spacetime diagram that brings infinity to finite diagram boundaries while preserving causal structure. Unlike ordinary diagrams, it emphasizes global causal structure and infinity.
Light cone: The set of spacetime directions that light can travel from or reach an event. Its boundaries mark light paths and divide possible causal relations.
Causality: The relation between causes and effects, constrained in relativity by the finite speed of signals. Light cones show which events can influence one another.

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