Light cone

A light cone is a term in physics used to describe the structure of spacetime. It refers to the geometric shape formed by the range of light signals spreading out from an event in spacetime. In four-dimensional spacetime, we usually replace the time dimension t with the z-axis in three-dimensional space. Taking the point where the event happens (x0, y0, t0) as the origin, its mathematical expression defines the spatial range using the product of the speed of light c and time t (ct) as the radius.