It’s astonishing how early Elon Musk had alighted on his big interests in life - and stuck to them.

As a kid he was obsessed with science fiction - not for the stories, but because each book dealt with important issues like AI, planetary colonization, and advanced forms of rocket propulsion.

In his teens, he asked a potential girlfriend what she thought about electric cars. At University of Pennsylvania, his friend Robin Ren remembers him thinking a lot about rockets, and getting to Mars. “I thought he was just fantasizing” Ren told biographer Walter Isaacson.

Musk would lie on the university lawns reading academic articles about batteries. His senior physics paper was on solar energy, for which he got a grade of 98 percent. But Musk wasn’t just thinking about specific technologies. Systems interested him deeply.

On a cross country road trip, he detoured to Denver Airport to observe a new (problematic) automated baggage carousel system. Musk realized the airport “misunderstood the complexity of what they were building.”

In 1995 he was graduating from UPenn, and considered doing a PhD at Stanford, working on capacitors that could power electric cars. But he baulked at years spent as a student, when three big things were about to change humanity: the internet, sustainable energy, and space travel.

Energy and space travel were long-term challenges, but the internet was happening now. With brother Kimbal, he built software that would combine city maps with business listings. It was called Zip2.

In 1999, Zip2 was sold to Compaq Computer. Out of the $307 million sale, Elon netted $22 million. He bought a condo and McLaren car, which he subsequently crashed. He then put $12 million into X.com, which later merged into Peter Thiel's PayPal.

His payout from eBay’s acquisition of PayPal in 2002 was $250 million. But Musk’s success with the emerging world of online commerce could not satisfy him. His mind soon went back to his true love: space.

Elon told PayPal colleague Reid Hoffman about his plans to send a rocket to Mars, colonize it and save humanity by making the species multiplanetary. Hoffman thought he was mad. “How is this a business?” he asked.