Here we refer to a notion of _spacetime_ that treats time as a dimension rather than an evolving parameter in contrast with [[Galilean spacetime]]. Thus we conceptualize a coordinate system where we consider three spatial dimensions plus one time dimension. Notice how we always refer to 3+1 dimensions rather than 4 dimensions. This is reflective of the fact that we treat time differently since an object in spacetime may only move forward in time. # Points and curves in Spacetime Within spacetime we define points called _events_ and the path of an object through spacetime modeled as a set of events strung together in a path is called a _worldline_. The path of a worldline is constrained in its curvature by its [light cone](causality#Light%20cone) at any point. We plot events and worldlines on a [Spacetime diagram](Spacetime%20diagram.md). # Geometric properties ## Minkowski spacetime # Integral measure The notation commonly used to denote an [[integral measure]] in three spacial dimensions plus the additional time dimension is $d^4 x.$ #Mechanics #Mechanics/SpecialRelativity