Formorethantwentyyearsscientistshavebeensearchingforsig...
问题详情：Formorethantwentyyearsscientistshavebeensearchingforsignsoflifeonotherplanets.Mostofthesesearcheshavebeendoneovertheradio.Thehopeisthatsomeoneinouterspacemaybetryingtogetintouchwithus.Scientis...