 Dr. Maurice Ewing, a pioneer of oceanography and geophysics, first suggested putting small hollow metal spheres in pilots' emergency kits during World War II.The spheres would implode when they sank to the sofar channel, acting as a secret homing beacon to be received by microphones on coastlines that could pinpoint downed pilots' positions.This technology turned out to be extremely useful for the naval conflicts during World War II by providing a way for ships to accurately report their position without use of radio, or to find crashed planes and ships.