RADAR, which stands for RAdio Detection And Ranging, works by sending out electromagnetic radiation, allowing it to bounce off of objects, and receiving it again after it has been reflected. The RADAR system measures things like how long it took for the signal to make it back, how the frequency of the signal has changed, and how the strength of the signal has changed. From this information, the RADAR system can “see” where the objects that reflected the light are located. This can also be used to determine the speed of an object, such as when the police use a RADAR gun to track the speed of a vehicle.