World lines

A world line is a concept in physics that represents the path an object takes through four-dimensional spacetime (three dimensions of space and one of time). It shows how an object's position changes over time. For example, Earth's world line traces its movement through space and time over billions of years. Understanding world lines helps physicists analyze how objects move, interact, or are affected by gravity in the universe, providing a complete picture of their history and future in the fabric of spacetime.