Congruence (general relativity)
= Congruence (general relativity)
{wiki=Congruence_(general_relativity)}
In the context of general relativity, "congruence" refers to a family of curves in spacetime, typically representing the paths taken by freely falling particles. A congruence can be thought of as a collection of trajectories (worldlines) that share a common property, often providing insight into the geometric structure of spacetime.