The Science of Time, Space and Spacetime

Human beings have always treated space and time as though they were two completely different departments. Space was where things happened. Time was when they happened. Space could be measured with a ruler, while time required a clock, a calendar, or somebody repeatedly asking whether we were there yet. This arrangement seemed perfectly reasonable until physics discovered that the two departments had been secretly sharing an office, exchanging paperwork, and altering each other's records.Modern physics describes the universe not as three dimensions of space moving through a separate stream of time, but as a four-dimensional structure called spacetime. Every event has both a location and a time. Saying that something happened in Pensacola is not enough, because Pensacola has existed through many different moments. Saying that it happened Tuesday is equally unhelpful, because Tuesday occurred in Pensacola, Paris, Jupiter, and countless regions of the universe where nobody had the slightest idea it was Tuesday. A complete event requires both an address and an appointment.