The great physicist Stephen Hawking passed away on March 14, 2018. A true legend of physics, he was also a very talented popularizer. A look back at the extraordinary life of this scientist who knew how to make himself loved by the public and make his scientific research accessible: and who became famous for his theoretical work on black holes, superstring theory, Hawking radiation, theorems on singularities… Science says a huge thank you to him.

## Discoveries

Stephen Hawking’s work concerns cosmology, quantum gravity, and black holes. He formulated theorems on singularities in cosmology with Roger Penrose. He discovered that black holes emit radiation, called Hawking radiation. He developed theories on nitrous black holes and microscopic virtual black holes. He worked on the entropy of black holes and discovered the information paradox. He also explored the physics of wormholes, including those that can traverse and that would allow time travel, according to the work of the Nobel Prize winner in Physics, Kip Thorne. He proposed the theory of the Universe without edge based on the Feynman path integral, the Wheeler-DeWitt equation, and using an imaginary time with James Hartle.

## Biography

In Oxford, Stephen William Hawking, born January 8, 1942, is a British theoretical physicist and cosmologist well known for his work on black holes, quantum cosmology, and his books of popularization on the same subjects. His bestseller A Brief History of Time, which remained on the Sunday Times bestseller list for 237 consecutive weeks, brought him to public attention.

Hawking’s media fame also comes from the fact that he did his work while suffering from neuromuscular dystrophy attributed to amyotrophic lateral sclerosis (ALS). This terrible disease, known colloquially in the United States as Lou Gehrig’s disease and in France as Charcot’s disease, which leads to complete paralysis and death within a few years in general, struck him shortly after his 20th birthday.

## From singularities in cosmology to black hole radiation

He was then a student at Cambridge, where he intended to study cosmology with Fred Hoyle, one of the most important astrophysicists of the 1950s and 1960s and co-author of the standard model of cosmology eternally expanding and infinite Universe. To his great despair (but it was a chance, as Hawking understood in retrospect), he was assigned as his thesis supervisor William Dennis Sciama, who was not very well known at that time. Stimulated by his meeting and marriage to Jane Wilde in 1965, and because his illness was progressing less rapidly than expected, Hawking finished his Ph.D. by publishing, from 1966 onwards, resounding articles on the occurrence of singularities relativistic cosmology. He used the geometrical methods of the great mathematician Roger Penrose, which Penrose had initially used to demonstrate the existence of a singularity during the formation of a black hole in classical general relativity.

Hawking’s work came at a time when the discoveries of quasars and especially of fossil radiation by Penzias and Wilson in 1965 had just refuted the theory of stationary cosmology of Hoyle, Hermann Bondi, and Thomas Gold. The Big Bang theory of Georges Lemaître, Georges Gamow, and Ralph Alpher was finally taken seriously.

Using Penrose’s mathematical methods and understanding the importance of John Wheeler’s ideas on black holes, wormholes, and quantum cosmology, Hawking was to profoundly impact theoretical physics and cosmology during the 1970s and 1980s. Influenced by the work of Bekenstein, Zel’dovich, Starobinsky, and Linde, he will make a name for himself by discovering the radiation of black holes in 1974 and by developing several important aspects of the theory of inflation during the 1980s. This work will lead him to create a fascinating cosmological model in 1983, universally known today as the Hartle-Hawking model. Taking up the method of calculation in a quantum theory known as the Feynman path integral, whose effectiveness he had seen in his research on entropy and radiation of black holes, Hawking proposed with Hartle a cosmological model finite in space and characterized by the appearance of imaginary time at the time when the effects of quantum gravitation dominated the Universe, that is to say, before the Planck time.

## From the entropy of black holes to the Higgs boson

The determination and intellectual capacities of Stephen Hawking are measured by the fact that this work was carried out in 1974, when, due to the paralysis caused by ALS, he was unable to feed himself or to get out of bed by himself and his condition was only getting worse. His speech, already severely impaired by his disease so that only those who knew him well could still understand him, gave way to a total inability to speak in 1985. By then, he had contracted pneumonia, and doctors had to perform a tracheotomy to save his life. Since the late 1980s, he has had to use a computer to speak.

In the late 1990s and early 2000s, Hawking became a strong proponent of superstring theory, particularly M-theory, because it provides a better understanding of the origin of entropy in black holes. He will publish a new popularization book on these subjects in 2001, The Universe in a Nutshell. The book popularizes theories such as supergravity, supersymmetry, and quantum theory at the basis of the M theory, holography, and the duality of p-branes contained in the superstring theory and their implications on black holes and the existence of multiple universes. Scientifically, M theory convinced Hawking that he had lost his bet on the famous and profound paradox of information appearing with black holes and that he had been the first to point out. He conceded in 2004 to John Preskill that what did not destroy information in black holes. In 2012, he also acknowledged to Gordon Kane that the Higgs boson did exist.

## A career saluted by numerous distinctions.

In 2009, Hawking left the prestigious Lucasian Chair of Mathematics at the University of Cambridge, as planned because of the age limit. It has been occupied by great names in physics, including those whose theories have profoundly changed our view of the world: Isaac Newton and Paul Dirac. The current holder is Michael Green.

Stephen Hawking, who has received numerous awards, has not received a Nobel Prize, possibly because his work is too theoretical. But he could logically have received the Nobel Prize in Physics if black holes had been detected evaporating, for example, at the LHC. However, Stephen Hawking received $3 million in 2012 as the Fundamental Physics Prize Foundation’s special award. One of his biggest dreams was to fly in space, while he already made a weightless flight in 2007 thanks to the company Zero-G, founded by Peter Diamandis.

Very involved in the media, he has strongly participated in the communication of science to the public. A Stephen Hawking Medal for Science Communication was created in 2016 to recognize such contributions. The asteroid (7672) was also named in his honor. In addition, in recent years, he was alerting the world against climate change.

Stephen Hawking died on March 14, 2018, in Cambridge, UK, at the age of 76. A biographical film released in 2014, entitled A Wonderful Story of Time, traces the life of this great physicist.