In physics, the
world line of an object is the path of that object in 4-
dimensional spacetime, tracing the history of its location in space at each instant in time. The concept of "world line" is distinguished from the concept of "orbit" or "trajectory" (such as an
orbit in space or a
trajectory of a truck on a road map) by the
time dimension, and typically encompasses a large area of spacetime wherein
perceptually straight paths are recalculated to show their (relatively) more absolute position states — to reveal the nature of
special relativity or
gravitational interactions. The idea of world lines originates in
physics and was pioneered by
Hermann Minkowski. The term is now most often used in relativity theories (i.e.,
special relativity and
general relativity).