Special relativity has changed the way we think about time and the order of events. Einstein famously showed that two events can look simultaneous to one observer but not to another. In fact, it’s possible to make two spatially separated events appear in any order by choosing to view them from different frames of reference .
But what of three or more events? “Do all possible time orderings occur in some frame or other? If not, what are the restrictions?” ask Alfred Shapere at the University of Kentucky in Lexington and Frank Wilczek of the Massachusetts Institute of Technology in Cambridge. Today, they give us the answer.
via technology review
