The "spacetime interval", also called "invariant interval", between the two events, "s" 2 Note that the term "spacetime interval" is applied by several authors to the quantity "s" 2 and not to "s".
The "spacetime interval", also called "invariant interval", between the two events is defined as follows. The spacetime interval, "s" 2 Note that the term "spacetime interval" is applied by several authors to the quantity "s" 2 and not to "s".