Sounds returning from the sky seconds later... The mystery of “long-delayed radio echoes” has baffled scientists for a century

Lebanon 24: In 1927, Norwegian civil engineer and radio enthusiast Jørgen Hals was following a shortwave radio broadcast in the Dutch city of Eindhoven when he noticed something strange: “long-delayed” radio echoes arriving about three seconds after the original signals. Hals wrote that day: “Where does this come from…