Radar

Radio detection and ranging, abbreviated to ra. d. a. r, was developed to follow the path of airplanes by detecting electromagnetic reflections. Microwaves are the best to use for this purpose because they are reflected by moderately sizable objects and are sufficiently penetrating to pass through cloud and fog.
 Robert Alexander Watson-Watt Scotland 1935 Radar

Radio detection and ranging, abbreviated to ra. d. a. r, was developed to follow the path of airplanes by detecting electromagnetic reflections. Microwaves are the best to use for this purpose because they are reflected by moderately sizable objects and are sufficiently penetrating to pass through cloud and fog.