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Great minds don’t always think alike.

Tesla and SpaceX CEO Elon Musk, who isn’t afraid to speak his mind, shared some thoughts early Tuesday morning via Twitter that essentially bashed Mark Zuckerberg’s understanding of artificial intelligence, the kind of technology that helps computers think more like humans.

Facebook and other tech giants are scrambling to build this kind of technology, and Zuckerberg even built an AI assistant to help control his Palo Alto home. Musk, on the other hand, thinks AI could ultimately destroy mankind and send everyone scrambling to Mars to avoid machine overlords.

So both men feel strongly about the technology, but in his tweet on Tuesday, Musk dismissed Zuckerberg’s knowledge of AI as “limited,” a pretty sick burn in the world of super-intelligent tech geeks.

I've talked to Mark about this. His understanding of the subject is limited. — Elon Musk (@elonmusk) July 25, 2017

Why would Elon say such a thing?

Let’s rewind to earlier this month, when Musk spoke at a meeting of American governors and warned that AI was the “biggest risk we face as a civilization” and urged the government to adopt AI legislation before robots start walking down the street murdering people.

Fast-forward a week to Sunday evening, when Zuckerberg spent almost 85 minutes streaming live to Facebook from his backyard barbecue. When a viewer mentioned Musk and asked what Zuckerberg thought of the warnings, he downplayed the concerns of AI.

Live grilling in my backyard. Posted by Mark Zuckerberg on Sunday, July 23, 2017

“I think people who are naysayers and try to drum up these doomsday scenarios — I don’t understand it,” Zuckerberg replied. “It’s really negative, and in some ways I think it's pretty irresponsible.”

When Musk then saw Zuckerberg’s comments in a story posted to Twitter, he chimed in.

“I've talked to Mark about this. His understanding of the subject is limited,” Musk tweeted.

There it is. Two great Silicon Valley techies, sort-of feuding over the future of human civilization. It’s no Donald Trump vs. Rosie O’Donnell beef, but considering the players involved, it’s certainly a lot more interesting.

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