9. He is a millionaire
Stephen Hawking is one of the most successful scientists especially in the field of cosmology. Now, he has $20 million amount of net worth.
He did not come from a rich family. At the beginning of his career, he was struggling with money. In fact, there was time when he could not even afford a nanny for his children.
Then he wrote his best-selling book, A Brief History of Time. As mentioned in the 10 Ways Smart People Can Get Rich article, the book was sold for more than 10 million copies in just 2 years. Assuming he only got $1 from each book sold, he already earned $10 million.
Plus, he has been working as director of research at the Cambridge University Department of Applied Mathematics and Theoretical Physics. Four years ago, he said he has no plan to retire.