Even though he could not move, the mind of British cosmologist Stephen Hawking, a frequent visitor to Pasadena and Caltech, moved at the speed of a rocket. And what Hawking foresaw in man’s first encounter with alien life is less than comforting for those who may have believed they would come in peace.    

Hawking is perhaps best known for the portion of his college thesis that proved that the Big Bang Theory was physically possible and for his research on black holes. His most famous book, “A Brief History of Time,” was published in 1988 and sought to explain the complexities of the universe to people who have no prior scientific knowledge on the matter. To date, it has sold over 10 million copies.

His status in the scientific world helped cement his status in pop culture, and he has made numerous television appearances on shows like “The Big Bang Theory” and “The Simpsons” as well as having had a movie made based on his life called “The Theory of Everything,” starring Eddie Redmayne, who went on to win the Oscar for Best Actor for his portrayal of Hawking.

In the 1970s, his knowledge and research brought him to Caltech, where he worked on his groundbreaking paper about black holes emitting radiation. He frequently visited the school in his later years and was named a Sherman Fairchild Distinguished Scholar.

However, in the years before his death last March, it was his thoughts on the existence of aliens that recaptured people’s attention.

In 2010, he released a mini documentary series that had an episode about aliens. In the documentary, “Into the Universe with Stephen Hawking,” he puts Earth — and the Milky Way for that matter — in perspective.

“The numbers alone make thinking about aliens perfectly rational,” he says, using British actor Benedict Cumberbatch as a narrator.

He describes the possibilities of what alien life could look like, saying it can range from dripping, green slime to ferocious animals. According to him, this is just the beginning of what really could be out there and scenarios like “Star Wars” and “Star Trek” are at least conceivable.

“There could be life forms out there so strange that we wouldn’t recognize them as life forms,” he says.

He thinks the information to figure out what alien life may look like and where to find it is on our planet, where there is the only known examples of life. However, as fun as it is to imagine all the possibilities of what alien life could look like, he gives a chilling warning. Aliens may be hostile toward us.

“We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet,” he says in the documentary.

As an example, he explains humans are already capable of modifying their genetic evolution. Aliens could’ve done the same and might’ve been able to stop their aging process and become virtually immortal. They could’ve also learned how to harness the power of a star to create wormholes to essentially create shortcuts between massive distances. They could’ve done all this millions of years ago.

“Alien technology should be as extraordinary to us as a rocket ship to a caveman,” Hawking says. “Such advanced aliens would perhaps become nomads looking to conquer and colonize whatever planets they can reach. … Like us, they would have probably evolved from a species used to exploiting whatever it can.”

This 2010 documentary wasn’t the last time Hawking commented on the risks of contacting or being contacted by aliens. In 2016, he did another mini documentary series called “Stephen Hawking’s Favorite Places” where he reiterated his fears.

“Meeting an advanced civilization could be like Native Americans encountering Columbus — that didn’t turn out so well,” he says. 

But not everyone agrees with his cautious views regarding contacting aliens.

In an Op-Ed for The Guardian, Seth Shostak, senior astronomer for the Search for Extraterrestrial Intelligence (SETI) Institute, wrote, “Any society with the capability to threaten Earth is overwhelmingly likely to already have the kit required to pick up the leakage we’ve been wafting skyward for seven decades.”

Douglas Vakoch, the president of Messaging Extraterrestrial Intelligence (METI), feels similarly.

“If there’s any alien out there paranoid about competition, it could have already come and wiped us out. If they’re on their way, it’s a lot better strategy to say we’re interested in being conversational partners,” he said in an interview with Futurism.

However, Hawking’s own precautions regarding the dangers of making contact with aliens didn’t stop him from wanting to pursue the search for alien life. In 2015, he, along with Russian investor Yuri Milner and Facebook CEO Mark Zuckerberg announced the debut of Breakthrough Listen, a $100 million program to collect and observe data for evidence of intelligent life.

“In such a massive place as the cosmos, we only have to look at ourselves for proof that extremely unlikely things can and do happen all the time,” he says in “Into the Universe with Stephen Hawking.”