Professor Daniel Drezner said so days after the US former director of national intelligence John Ratcliffe revealed the Pentagon files included declassified intelligence of aircraft "that exceed the sound barrier without a sonic boom".
The international politics expert at Tufts University on Thursday wrote in the Washington Post: "Does this evidence point toward the prospect of extraterrestrial observation of our planet? If so, how should we feel about that?
"I am not going to speculate on the first question beyond noting that if Harvard astrophysicists are making that suggestion about interstellar phenomena, perhaps we need at least to consider the possibility that these UAPs (Unidentified Aerial Phenomena) might also be extraterrestrial in origin."
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