Elon Musk thinks solar power and electric cars are the future, and that we should get to work building humanity's second home on Mars as soon as possible. But the billionaire techno-optimist continues to speak out about what he sees as the dangers of a future filled with super-intelligent machines.

On Saturday Musk posted this tweet, recommending an upcoming book that examines such a future, adding "We need to be super careful with AI. Potentially more dangerous than nukes."

Worth reading Superintelligence by Bostrom. We need to be super careful with AI. Potentially more dangerous than nukes. -- Elon Musk (@elonmusk) August 3, 2014

This isn't the first time Musk has voiced his apprehension about artificial intelligence, which other notable futurists like Google's Ray Kurzweil see in a much more positive, even romantic light. Back in June, Musk said on CNBC that he seriously considers the possibility of a 'Terminator"-like scenario actually coming to pass, and that he's even invested in AI companies to keep on eye on where the technology is headed.

Of course, if you read a little deeper into the writing catalog of Nick Bostrom, the author whose book Musk recommends in his tweet, you'll discover his concerns could be a moot point. Back in 2003, Bostrom published a paper arguing the odds are pretty good that we're actually living in a computer simulation, and scientists have recently begun to search for "signatures" that show our world is not quite as real as we'd like to think.

So yes, perhaps Elon, the driving force behind Tesla Motors and SpaceX, is right and we should be more worried about artificial intelligence, unless of course, we are also artificially intelligent. If that's the case then we need to... Hold on, I'm going to need to re-watch "Tron" and get back to you guys on this one.