Relativity

Miles Breuer’s story “The gostak and the doshes” has a protagonist who can swap between the dimensions of time and space. We discuss why time and space cannot be freely interchanged in this way. Space, which permits movement in multiple directions, operates in a fundamentally different way to time, which flows in only one direction. In the context of special relativity, the spacetime interval — which combines spatial distance and temporal duration — governs the relationship between space and time. Crucially, the time and space elements in the interval differ by a minus sign. That minus sign ensures space and time operate differently. We briefly discuss how general relativity adds interesting complications to the picture.