The little brother of an Army radar operator asked: “Jim, tell me how does a radar work?”

“The radar transmitter emits brief impulses of electromagnetic waves which are reflected from the target and received by a special receiver. Since the speed at which electromagnetic waves propagate is exactly known and the time they take to travel to the target and back can be determined with a great degree of accuracy it is possible to determine the range to the target as well as the direction to it.”

His brother pondered a moment, then said: “As long as you don’t know, Jim, why don’t you just say so?”