Elon Musk's Next Wild Promise

Elon Musk has a predilection for grandeur. The billionaire tech provocateur made his fortune as a founder of the revolutionary online-payments company PayPal, and since then, he has announced his intention to revolutionize cars, trains, space travel, intercontinental flight, and city driving. SpaceX, his aerospace company, has begun work on the infrastructure to beam internet access down to Earth from satellites in orbit around the planet. And this week, Musk shifted his public ambitions to his next target: the human brain. Neuralink, a neurotechnology company owned by Musk, crept out of the corporate shadows Tuesday with a live-stream that included one of the founder's signature big promises: The company is developing a device to implant inside the brain that supposedly will allow people to control computers and other devices with their mind.