The concept of a "world line" is distinguished from concepts such as an " orbit " or a " trajectory " (e.g., a planet's orbit in space or the trajectory of a car on a road) by inclusion of the dimension time, and typically encompasses a large area of spacetime wherein paths which are straight perceptually are rendered as curves in spacetime to show their (relatively) more absolute position states —to reveal the nature of special relativity or gravitational interactions.