that the quest for extraterrestrial intelligence may require a significant effort.这种考虑揭示了,对外星人的探索可能要付出巨大的努力.(这表明,搜寻外星人需要作出巨大的努力.)

Despite claims about ancient astronauts and unidentified flying objects ,there is no firm evidence for past visitations of the Earth by other civilizations. 尽管有关于古代天文学家的声明和未经确认的飞碟,但对地球以前被其他文明社会的人光顾过没有清晰的证据.(尽管有人声称见过古代的太空人和来历不明的飞行物体,但并无确切证据证实别的文明世界的来客曾经访问过地球.)We are restricted to remote signaling and , of the long-distance techniques available to our technology,radio is by far the best.我们的技术受远程信号和长距离技巧所限,到目前为止无线电是最好的. (我们目前只限于远距离信号