radio detection and ranging (10. 574)

Already having pioneered and already discovered practical applications for radio direction finding in the 1920s for meteorology by using the signals given off by lightning to track thunderstorms—known as high-frequency direction finding or huff-duff, and then conscripted into service in tracing submarines, their bearings revealed by intercepted communications, on this day in 1935—after being asked by a reporter to comment on the possibility of a death ray that the Nazis were rumoured to be developing and assuring the public it was not feasible but sparked another idea—Robert Alexander Watson Watt and partner Arnold Wilkins made the first public demonstration of the technology that would become known as radar by bouncing a signal from a BBC short-wave transmitted off an aircraft, showing its location and velocity could be calculated by measuring the time it took for the object’s echo to return.