Federico Battiston | @fede7j |

Federico Musciotto | @musci8 |

Roberta Sinatra* | @robysinatra |

Michael Szell | @mszll |

Stephen Hawking is one of the biggest icons of science. Undoubtedly he had a highly productive life as an author, full of scientific works and brilliant books - but how did society perceive his works? What was the success and impact of his oeuvre? Stephen Hawking himself admits that he never expected his book *A Brief History of time* "to do anything like as well as it did".

Following our previous study on scientific careers, we reconstructed Hawking's career in the interactive plot below, displaying the contributions he gave to science through publications and books, and their impact on the scientific community and society. Data about journal publications are taken from Web of Science, about books from Goodreads. Each red dot represents a scientific paper of Hawking, its height being the paper impact quantified by citations over 10 years after publication. Each purple dot stands for a book, its impact quantified by the number of ratings on Goodreads.

The already mentioned *A Brief History of time* shoots off the chart in the career plot, having a spectacular number of almost 200,000 ratings on Goodreads only. This measure is confirmed by Hawking's own calculation based on the book sale: the book and its translations into 40 languages have sold "about one copy for every 750 man, woman and child in the world", as Hawking writes in the introduction to the latest paperback edition.

A *Brief History* has certainly influenced the minds of a generation as few other contemporary titles have done. Also several of his other books have had a wonderful reception, like "The Grand Design" with 50,000+ ratings, "The Universe in a Nutshell" with 25,000+ ratings, and the follow-up to his smash-hit, "A Briefer History of Time" with 20,000+ ratings - a result that not many people were expecting since we are talking about books on theoretical physics discoveries and cosmology. As the theoretical physicist Sabine Hossenfelder wrote, after 1988 the popular science landscape has changed dramatically, with more books about theoretical physics than ever before, a result also due to Stephen Hawking who encouraged other scientists to write about their own research for the public.

The scientific production of Hawking for the scientific audience was also enormous, with 148 articles indexed by Web of Science, published over a career of more than 50 years spanning from 1965 to 2014, totalling 40,873 citations. Probably the most important contribution of Hawking to the scientific literature was the 1974 Nature paper *Black holes explosions?*, hailed by scientists as the first great landmark in the struggle to find a single theory of nature. Interestingly the publication received "only" 266 citations after 10 years, ranking it fourth among Hawking's publications with highest impact after 10 years. However, it had a much longer lasting impact over time than other works, with a total of 2,596 citations at the end of 2016.
The other groundbreaking work of Hawking is the 1975 paper *Particle creation by Black-Holes*, which received 6,164 citations in total. Also this paper had an incredibly long-lasting impact compared to its short-term impact of "only" 485 citations in the first 10 years after publication.

According to Sabine Hossenfelder, a crucial paper in Hawking's career, although lesser known, was written in 1971 about the analysis of gravitational wave signals - a paper that acquired only 53 citations after 10 years and 74 in total. However, Hawking's passion for black holes and all the world-famous consequent results stemmed from his original interest in gravitational waves.

Finally, Hawking was also tireless - even after the year 2000, when he was already 60, he published 12 papers - two of which received more than 200 citations - and 8 books. For a complete narrative of the scientific life of Hawking, see the NYT.

Stephen Hawking was not only a highly productive scientist who left an incredible corpus of research, but he was also a shining visionary. He recognized early that: "I think the next [21st] century will be the century of complexity. We have already discovered the basic laws that govern matter and understand all the normal situations. We donâ€™t know how the laws fit together, and what happens under extreme conditions. But I expect we will find a complete unified theory sometime this century. There is no limit to the complexity that we can build using those basic laws." [1]

His popular bestsellers attest his life-long passion to bring science to the layman and to work tirelessly on unveiling the mysteries of the universe independent of our disciplines: "If we do discover a complete theory, it should in time be understandable in broad principle by everyone, not just a few scientists. Then we shall all, philosophers, scientists, and just ordinary people, be able to take part in the discussion of the question of why it is that we and the universe exist." [2]

Total number of papers: 148

Total citations: 40,873

Total number of books: 17

Total number of book ratings: 336,478

Average number of citations per paper: 276

Average number of citations after 10 years per paper: 69

Max number of citations for a paper: 6,164

Max number of citations after 10 years for a paper: 552

H-index: 78

Q-parameter: 10.76

[1] Unified Theory" Is Getting Closer, Hawking Predicts', interview in San Jose Mercury News (23 Jan 2000), 29A

[2] Stephen Hawking, A brief history of time, Bantam Books (1988).