radar

Radar, an acronym for "radio detection and ranging," was developed and in use by several nations as early as World War II. Radar is a system that detects objects and their movements through time and space by emitting pulses of radio waves. When these waves encounter an object, the waves' movement is disrupted, and readings of this disruption bounce back in the direction from which they were emitted, where their energy is read and analyzed to determine size and direction and speed of movement of the object encountered.