71.   One idea is printing the radio equivalent of bar codes on packaging that would absorb the energy of a radio signal and send a response.

72.   One of his favorite targets was a NASA proposal to research methods of using large radio telescopes in a search for radio signals from extraterrestrial civilizations.

73.   Philippe converted the letters to radio signals and beamed them toward the center of the galaxy.

74.   Poor radio signals make the network slower.

75.   Racing crews nowadays tap into computers to receive radio signals from the cars during a race, monitoring fuel burn, suspension travel, and tire pressure.

76.   Researchers know that heat and moisture in the atmosphere can distort radio signals.

77.   Radar is a radio signal that encounters obstacles, which bounce the signal back to an antenna.

78.   Radio signals from the craft showed it survived touchdown, considered a great achievement because the spacecraft was designed only to orbit and not to land.

79.   Radio signals take a second to reach the moon, and several minutes to reach Mars.

80.   SETI stands for the Search for Extra-terrestrial Intelligence, and for decades astronomers have been scanning the skies for radio signals from distant civilizations.