Can many worldlines occur in 4D spacetime where observers in each worldline think they're the "real" worldine? Is there a mechanism preventing many worldlines from occurring in 4D spacetime. Einstein said this in his book Relativity: Look at this scenario. Event A occurs outside of the light cone of earth. Light from this event reaches earth in it's past light cone.Let's say 1986. This event causes NASA to move the Challenger launch to a later date. In this worldline Challenger was a success and never exploded. So in this worldline observers think it's "the real worldline" and Challenger never exploded. Is there anything scientifically wrong with this scenario? Is there a mechanism we know in science that would stop other worldlines from occurring in 4D spacetime?