One scientist claims aliens have already visited us and we should invest more in searching for extraterrestrials. Avi Loeb is a theoretical physicist, former chair of the astronomy department at Harvard University, and author of a new book called For the past few years, he’s argued that an alien artifact, called Oumuamua, passed by Earth in 2017. As you can imagine, a Harvard professor going on record that aliens exist caused quite a stir in the scientific community. “People tend to have an opinion ahead of time, and I think that’s dangerous because we just don’t know who lives in our neighborhood and what their objectives are,” says Loeb.