Mysterious repeating energy bursts from deep space that some experts have suggested could be evidence of advanced aliens have been detected for only the second time in history.
Fast radio bursts (FRBs) are millisecond-long flashes of radio waves whose origin is unknown.
Most scientists believe they are generated by powerful astrophysical phenomena such as black holes or super-dense neutron stars. But a few have suggested more outlandish theories.
Prof Avi Loeb, from the Harvard-Smithsonian centre for astrophysics in Cambridge, Massachusetts, believes they could be evidence of incredibly advanced alien technology.
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