Renowned for investigating the stars, Stephen Hawking’s public persona was rarely anything but down to earth. The world-famous cosmologist’s popular science book, A Brief History of Time, electrified readers, young and old, across the world when it was published in 1988, and stayed on The Sunday Times bestseller list for 287 weeks. The jargon-free guide to the origin and future of time and space, aimed at teenagers, has been translated into 35 languages.

But time was something no one thought would be kind to Hawking. Diagnosed at age 22 with amyotrophic lateral sclerosis (ALS), otherwise known as motor neurone disease, he was told he had little left. He lived another 54 years.

Stephen Hawking’s upbringing was not typical. Born in Oxford in 1942 (300 years after the death of Galileo), he was raised in St Albans, where the family car was a black cab and Hawking only learned to read by the age of eight. Despite the late development of his literacy, he matriculated at University College, Oxford, only nine years later.

“When you are faced with the possibility of an early death it makes you realise that life is worth living”

He was adventurous, both in his scholarship and his wider life. In the long vacation following his final exam term at Oxford in 1962, he travelled to the Middle East with fellow student John Elder, who spoke Farsi. Believing his chances of obtaining a travel grant from his college would be greater the further he proposed to go, he planned to head to Iran.

The pair travelled by train to Istanbul before heading to Erzurum in eastern Turkey. Their journey to Tehran took them on a bumpy bus ride across Iranian countryside, before Hawking parted ways with Elder and headed south to Shiraz and then crossed the central desert to Mashhad, Iran’s second largest city. Ill from dysentery and suffering a broken rib from the bus ride, Hawking was oblivious to the Buin Zahra earthquake which had killed more than 12,000 people until his return to Istanbul.

Hawking arrived for postgraduate study at Cambridge’s Department of Applied Mathematics and Theoretical Physics (DAMTP) in October that year, aged just 20. The Department was based at the old Cavendish Laboratory on Free School Lane, which fittingly now houses the Department of History and Philosophy of Science.

At the time, Hawking wanted to study under Fred Hoyle, one of the world’s most eminent astronomers, but was assigned to Dennis Sciama instead, who was unknown to to the young scholar. Sciama went on to supervise other notable scientists, including astronomer royal Lord Rees, former master of Trinity College, Cambridge.

Hawking became almost as famous for his wit as he was for his science. It was a good thing, he reflected in his final public appearance in November, that he was not assigned to Hoyle, as it would have meant he “would have been drawn into defending the Steady State theory, a task which would have been harder than negotiating Brexit.” Now widely discredited, the Steady State theory is an alternative to the Big Bang theory, which suggests that matter is continually created as the universe expands, keeping its density constant.

“They never actually told me what was wrong, but I guessed it was pretty bad so I didn’t want to ask”

Sciama suggested that Hawking work on astrophysics, but the stubborn young scientist was not easy to guide. “Having been cheated out of working with Hoyle, I wasn’t going to do something boring like Faraday Rotation. I had come to Cambridge to do cosmology, and cosmology I was determined to do.”

It was during the winter after his arrival at Cambridge that his mother, Isobel, suggested he go ice skating on the lake in St. Albans. Hawking fell, and struggled to get up again. His mother took him to Bart’s Hospital in London, where doctors kept him for weeks while he underwent tests. “They never actually told me what was wrong, but I guessed it was pretty bad so I didn’t want to ask,” Hawking said. His father, Frank, a tropical disease expert, became his doctor after he was diagnosed with motor neurone disease, which led to the slow degeneration of his muscles.

Hawking became depressed, believing there was little point working on his PhD as he didn’t know if he would be alive to finish it. But his hope grew, in large part due to his engagement to Jane Wilde, whom he had met at a party shortly before his diagnosis, in 1964. They had three children together: Robert, in 1967, Lucy, in 1970, and Timothy, in 1979.

“When you are faced with the possibility of an early death it makes you realise that life is worth living and that there are lots of things you want to do,” Hawking said.

The fundamental question of 1960s astronomy was whether the universe had a beginning, which general relativity predicted, contrary to many contemporary theorists who considered their religious beliefs to be at odds with the possibility. Hawking, who was an atheist, did not consider this to be a barrier to his research.

It was shortly after his daughter Lucy’s birth, while climbing slowly into bed, that Hawking realised his area theory of black holes: if general relativity is correct, and the energy density of a black hole is positive, then its boundary always increases when matter or radiation fall into it. Moreover, if two black holes collide, the boundary of the resultant black hole is larger than the sum of the boundary of the original two black holes.

He discovered the black hole entropy formula, which can be used to calculate a black hole’s entropy in terms of the area of the horizon. In 1972, he published his theory of black hole radiation, now known as Hawking Radiation. NASA launched the Fermi Gamma-ray Space Telescope, to search for the theorised phenomenon, 36 years later.

Just weeks after his radiation theory was published, he was was elected to the fellowship of the Royal Society, aged just 32. In 1979, the Gonville & Caius fellow was appointed as the 17th Lucasian professor of mathematics at the University of Cambridge, a chair previously held by figures including Charles Babbage and Isaac Newton. While at Cambridge, as well as pursuing field-defining research into cosmology, general relativity, and the nature of the universe, he was known as an engaging and jovial professor. He even contributed to an article on the BRIT nominees by Varsity’s music section in 1997, giving his entertaining takes of the hits of the year.

In 2007, Hawking established the Centre for Theoretical Cosmology at the University of Cambridge, where he was director of research until his death. Two years later, on 28 June 2009, he hosted a party, complete with champagne and canapes, for time travellers. Hoping someone in the future would find his invitations, he waited patiently at Gonville & Caius College for his guests to arrive. When it was clear no one would turn up, Hawking said, with characteristically dry wit: “What a shame. I was hoping a future Miss Universe was going to step through the door.”

Most recently, Hawking was working with Andy Strominger, of Harvard, and Malcolm Perry, of Cambridge, on solving more problems in the way we understand information transmission from black holes. Shortly before his death, he expressed hope that analysis of radiation will one day allow us to understand the very “heart” of the Big Bang.

“Remember to look up at the stars and not down at your feet”

Identified but not defined by his wheelchair, Hawking became an iconic figure of popular science, inspiring generations with his books, lectures, and resilience. His life was adapted into a 2014 film, The Theory of Everything. Eddie Redmayne’s portrayal of Hawking won the Academy Award for Best Actor. The physicist said he was humbled by the film, which he said gave him the opportunity to reflect on his time on Earth.

Late last year, Hawking’s PhD thesis, Properties of Expanding Universes, was published on the University of Cambridge’s website. A sign of his continuing popularity right up until his death, the website crashed due to unprecedented traffic. A month later, on 21st November, Hawking gave what few expected to be his last public appearance, at the Cambridge Union Society. He was inaugurated as its first Hawking fellow, a title which will be bestowed annually upon eminent figures who have contributed to British society.

He closed his speech at the Cambridge Union by saying: “Let me finish by reflecting on the state of the universe. It has been a glorious time to be alive and doing research in theoretical physics. Our picture of the universe has changed in the last 50 years and I am happy to have made a small contribution.

“I want to share my excitement and enthusiasm about this. So remember to look up at the stars and not down at your feet. Try to make sense of what you see and wonder how that makes the universe exist. Be curious. And however difficult life may seem there is always something you can do and succeed at. It matters that you don’t just give up. Thank you for listening.”

Stephen Hawking, theoretical physicist and cosmologist, died at his home in Cambridge on 14th March.