As with SpaceX, then, Mr Musk is gambling Tesla’s future on AI, and his belief that he can harness his existing businesses to dominate the technology. Plenty of doubters have scoffed at his grand ambitions before. But never has Mr Musk put so much on the line. ■

The record-setting transaction is the largest merger of all time and values SpaceX at $1 trillion and xAI at $250 billion, according to documents viewed by CNBC.

In emails dating to 2012, the Tesla and SpaceX CEO and the millionaire financier discussed holiday plans, parties, SpaceX visits and lack of sleep.

Musk's memo announcing SpaceX and xAI's merger is full of space jargon. Here's your cheat sheet to bring the wonky language back down to Earth.

The world’s richest man has repeatedly become entangled in the four-year conflict as his Starlink is key to Ukrainian military communications.