Arecibo message: What happened when people claimed aliens contacted them – and why we might never want to

When the Arecibo message was sent into space in 1974 – blasting the most powerful signal ever broadcast deep into the universe – it was a pioneering attempt to reach out to aliens, wherever they might be. When a response came back in 2001, it was a hoax that showed just how much some people hope we can actually communicate with extraterrestrials. But that fake reply might actually be the message we ever get back from aliens. That's because some of the greatest minds on Earth fear rather than hope for contact with extraterrestrial life. Because the real reply to the Arecibo message might actually be something far more terrifying.