Stephen Hawking (born January 8, 1942) was a British scientist, professor and author who achieved groundbreaking work in physics and cosmology, and whose books have helped to make science accessible to everyone.

At the early age of 21, while studying cosmology at the University of Cambridge, he was diagnosed with amyotrophic lateral sclerosis (ALS, or Lou Gehrig‘s disease). In a very simple sense, the nerves that controlled his muscles were shutting down – and, at the time, doctors gave him two and a half years to live. However, defying all odds, Stephen went on to live and become one of the most influential scientists of all time.

His incredible life story was depicted in the 2014 film The Theory of Everything.

Over the years, Stephen Hawking has written or co-written a total of 15 books. A few of the most noteworthy include:

‘A Brief History of Time’

In 1988 Hawking catapulted to international prominence with the publication of A Brief History of Time. The short, informative book became an account of cosmology for the masses and offered an overview of space and time, the existence of God and the future. The work was an instant success, spending more than four years atop the London Sunday Times’ best-seller list. Since its publication, it has sold millions of copies worldwide and been translated into more than 40 languages.

‘The Universe in a Nutshell’

A Brief History of Time also wasn’t as easy to understand as some had hoped. So in 2001, Hawking followed up his book with The Universe in a Nutshell, which offered a more illustrated guide to cosmology’s big theories.

‘A Briefer History of Time’

In 2005, Hawking authored the even more accessible A Briefer History of Time, which further simplified the original work’s core concepts and touched upon the newest developments in the field like string theory.

Together these three books, along with Hawking’s own research and papers, articulate the physicist’s personal search for science’s Holy Grail: a single unifying theory that can combine cosmology (the study of the big) with quantum mechanics (the study of the small) to explain how the universe began. It’s this kind of ambitious thinking that has allowed Hawking, who claims he can think in 11 dimensions, to lay out some big possibilities for humankind. He’s convinced that time travel is possible, and that humans may indeed colonize other planets in the future.

Hawking on AI

In 2014, Hawking, among other top scientists, spoke out about the possible dangers of artificial intelligence, or AI, calling for more research to be done on all of possible ramifications of AI. Their comments were inspired by the Johnny Depp film Transcendence, which features a clash between humanity and technology.

“Success in creating AI would be the biggest event in human history,” the scientists wrote. “Unfortunately, it might also be the last, unless we learn how to avoid the risks.” The group warned of a time when this technology would be “outsmarting financial markets, out-inventing human researchers, out-manipulating human leaders, and developing weapons we cannot even understand.”

Hawking reiterated this stance while speaking at a technology conference in Lisbon, Portugal, in November 2017. Noting how AI could potentially make gains in wiping out poverty and disease, but could also lead to such theoretically destructive actions as the development of autonomous weapons, he said, “We cannot know if we will be infinitely helped by AI, or ignored by it and sidelined, or conceivably destroyed by it.”

Hawking and Aliens

In July 2015, Hawking held a news conference in London to announce the launch of a project called Breakthrough Listen. Funded by Russian entrepreneur Yuri Milner, Breakthrough Listen was created to devote more resources to the discovery of extraterrestrial life.

Breaking the Internet

In October 2017, Cambridge University posted Hawking’s 1965 doctoral thesis, “Properties of Expanding Universes,” to its website. An overwhelming demand for access promptly crashed the university server, though the document still fielded a staggering 60,000 views before the end of its first day online.