In SR, an event is a particular point in space and time. For simplicity, we only use one dimension of space. We have x'=γ(x-vt) if when x, t = 0 , x', t' = 0 Let's say we have a bunch of inertial frames, all moving at different speeds, but all sharing a common origin x, t = 0 From the POV of one of the inertial frames, we have a series of events in spacetime with the coordinates (x1,t1) , (x2, t2) etc. If we switch to another frame, the space-time coordinates will be transformed. How do I describe this set of events in a manner that is independent of any inertial frame? What about describing a continuous set of events, such as the continuous existence of the entire length of a rod that is floating in space?