Astrophysicist Neil DeGrasse Tyson has said that alien contact, which is the next frontier - may have already come and gone.
Speaking to MSNBC's Chris Hayes, the 'Cosmos' presenter said that his great fear is that they've been visited by extraterrestrials, but they chose not to make contact with us, on the conclusion that there's no sign of intelligent life on Earth, CNET reported.
Tyson said that there's plenty of organic matter in the Universe and that it is perfectly possible that planets out there have outlived their intelligent species.
