Elon Musk, the founder of Tesla and SpaceX, warned this weekend about the possible dangers of artificial intelligence. 

Super-intelligent robots that take over humanity seems like the stuff of science fiction. The idea was popularized in 1950 with Isaac Asimov's I, Robot trilogy, which speculates about how robots could outsmart humans within their own programming. Ever since then, the idea has kept cropping up in popular culture.

Musk tweeted on Aug. 2, recommending a book called "Superintelligence" by Bostrom, adding that, "We need to be super careful with AI. Potentially more dangerous than nukes." 

Should we fear artificial intelligence? Musk is not the first person in the tech world to give a statement warning about AI. Stephen Hawking has long been a proponent of using caution in artificial intelligence. In June, Hawking said in an interview with John Oliver on Comedy Central's Last Week Tonight, "Artificial intelligence could be a real danger in the not-too-distance future. It could design improvements to itself and outsmart us all."

"I know you're trying to get people to be cautious there, but why should I not be excited about fighting a robot?" Oliver quipped back.

"You would lose," Hawking replied briefly.

That underlines the reason physicists fear robot intelligence: if AI ever surpasses human intelligence, which it very may well do in the next few years, humans could not beat them at response time. In the past few years, we've seen computers beat humans in new ways -- like Watson, the IBM supercomputer that beat human Jeopardy contestants in 2011.

Musk has voiced concern about AI going awry before. In June, he told CNBC in an interview that he had invested in AI companies not so much for a return on investment but because he likes "to just keep an eye on what's going on."

Evans of CNBC asked him jokingly if people could just escape to Mars should computers ever become a problem for people on Earth, referencing the fact that Musk is a huge investor and contributor to space technology.

Musk shot that suggestion down. "The AI will chase us there pretty quickly," he said.

However, even though worried about a potential AI disaster years off, Musk remained light-hearted on Twitter over the weekend. He also tweeted about Disney's new Marvel movie, saying, "Guardians of the Galaxy is great. Best line is when Star-Lord says his spaceship looks like a Jackson Pollock painting under black light."