Elon Musk has overtaken Amazon . Messrs. Musk and Bezos, both founders of rocket companies, have clashed over issues such as Amazon's power over book publishing and Mr. Musk's interest in colonizing the planet Mars. Amazon last year bought a self-driving-car startup that would compete with Tesla. Mr. Musk's net worth totaled around $195 billion Thursday, up from roughly $30 billion a year ago and topping Mr. Bezos's wealth by about $10 billion, according to the Bloomberg Billionaires Index. The value of Tesla's shares rose almost 8% Thursday, enough for Mr. Musk to overtake Mr. Bezos in the wealth ranking.

Silicon Valley is training computers to see, hear and speak and cars and trucks to drive themselves. Some people aren't so sure how they feel about this new wave of artificial intelligence that summons fears of Terminator-like sentient machines. So Facebook is trying to dispel some of the pop-culture myths with a series of six instructional videos that attempt to explain this complex field of computer science. "I think the more open we can be about it and the more we can demystify and explain how it actually works, the more quickly we can address concerns," said Joaquin Quiñonero Candela, director of applied machine learning at Facebook. The campaign is part of a broader industry effort to influence public opinion as artificial intelligence is being used for more everyday tasks and even to automate warfare.