A Harvard professor says an alien visited in 2017 — and more are coming

When the first sign of intelligent life first visits us from space, it won’t be a giant saucer hovering over New York. More likely, it will be an alien civilization’s trash.  Avi Loeb, the chair of Harvard’s Department of Astronomy, believes he’s already found some of that garbage.  In his upcoming book, “Extraterrestrial: The First…