He suggests that aliens might simply raid Earth for its resources and then move on: “We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet. I imagine they might exist in massive ships, having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonise whatever planets they can reach.”
Mac was a huge fan of Stephen Hawking and I think he would've gotten a kick out of this latest article featuring Professor Hawking's latest "warning". Interesting... but, obviously Hawking hasn't considered cryptoterrestrials!