In mid-October Lockheed-Martin announced a revolutionary new sensor—Silent Sentry—based on the emerging reality that the world is bathed in man-made electromagnetic radiation, such as radio and television signals. Objects reflect or block such radiation, and thus can be detected, much as the eye detects objects by their reflection of surrounding light. The U.S. Navy discovered its version of radar by observing this same effect when passing airplanes affected radio transmissions across the Potomac from the Naval Research Laboratory. It occurred to researchers that the airplanes were reflecting the signals, and that radio could be used to detect them. They proposed an aircraft detection system in which an area of sky would be continuously illuminated, receivers picking up reflections.