As a teenage boy, Elon Musk felt a "personal obligation" for the fate of mankind, according to the book "Elon Musk: Tesla, SpaceX, and the Quest for a Fantastic Future" by Ashlee Vance.
Musk's love of books and the lessons he took from them inspired him to create "cleaner energy technology or [build] spaceships to extend the human species's reach" in the future, according to Vance.
One set of those books Musk still recommends today: the seven-book "Foundation" science fiction series by scientist and author Isaac Asimov.
"Worth reading Asimov's Foundation," the SpaceX and Tesla CEO tweeted on Wednesday, "in the order that they were written."
"The lesson I drew from [the "Foundation" saga] is you should try to take the set of actions that are likely to prolong civilization, minimize the probability of a dark age and reduce the length of a dark age if there is one," Musk told Rolling Stone in 2017.
Musk also said it taught him that "civilizations move in cycles," influencing him to pursue space exploration and further mankind's "upward cycle," he told The Guardian in 2013.
"Given that this is the first time in 4.5 billion years where it's been possible for humanity to extend life beyond Earth, it seems like we'd be wise to act while the window was open and not count on the fact it will be open a long time," Musk said.
As a result, Musk started SpaceX in 2002 (after his second start-up, X.com which later became PayPal, sold to eBay for $1.5 billion).
"Foundation Series & Zeroth Law are fundamental to creation of SpaceX," Musk tweeted in June 2018, referring to Asimov's Zeroth Law of robotics.
In 2003, Musk started Tesla, then Neuralink in 2016 and The Boring Company in 2017. Today, he is worth $42.3 billion, according to Forbes.