What Elon Musk Says Could Be More Dangerous Than Nuclear Weapons

— -- It's not a nuclear war that Elon Musk fears the most. It's artificial intelligence.

The billionaire founder of Tesla and SpaceX issued a warning over the weekend that "we need to be super careful" with artificial intelligence.

Musk's comments came after reading "Superintelligence," by Nick Bostrom, which explores the questions of what happens when machines are more intelligent than humans and whether artificial intelligence will save or destroy humanity. The book will be released in the United States on September 1.

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It sounds like something out of a science fiction novel, but when Elon Musk talks about the future, the world listens.

Musk also played film critic on Twitter over the weekend, where he raved about "Guardians of the Galaxy."