https://online2.tingclass.net/lesson/shi0529/10000/10183/863.mp3
https://image.tingclass.net/statics/js/2012
“Aliens,we found aliens!” Well, that’s kinda what Soviet radio astronomers said back in the early nineteen sixties, anyway. They held a press conference to announce that they had been listening in on an alien civilization that was broadcasting radio signals into space. These signals were of unbelievable power and went up and down in frequency with a period of roughly one hundred days. Nobody had ever seen – or heard anything like that before. It had to be evidence of intelligent beings with fantastically advanced technology. Maybe they were sending us a signal! Sadly, that hypothesis turned out to be wrong, and the Soviet radio astronomers probably felt kind of silly after making their announcement.