Radar, or radio location, as it was called in the early days, is the use of radio waves to find the whereabouts of aircraft or ships. Electromagnetic waves, which include radio and light waves, all travel at the same speed. When small bursts of radio waves, fired into space from a transmitter, strike an object such as an aircraft some the them bounce back and are collected by an aerial. Special equipment calculates the distance of the object from the time taken for the waves to go there and back.
Directions is obtained by rotating the aerial, and the course being taken by the object is shown as spots of light on the face of a cathode ray tube. So direction, position and movement can be judged accurately. Radar was first used to detect enemy aircraft in wartime, and to guide fighter aircraft and bomber pilots. Since then it has proved invaluable in civil aviation by helping the pilot to guide his aircraft in the air and to land it safely in fog or at night. At sea it can give the position of land other ships. Some buoys are fitted with radar, so that they can be located in the dark or in fog. Radar is used also to give warning of turbulent weather.