Possibly the most famous physicist since Albert Einstein, Stephen Hawking turns 75. Bound to a wheelchair by an incurable motor neurone disease, he is regarded by many as the greatest genius of our day.
Retired Cambridge Professor Stephen Hawking has lived his life defying expectations. Diagnosed with motor neurone disease in 1963 he was given two years to live. Now more than 50 years on, the physicist is due to celebrate his 75th birthday on January 8.
At the age of 20, the Cambridge student had just embarked on his doctoral studies when he was diagnosed with a fatal and extremely rare disease known as amyotrophic lateral sclerosis (ALS).
The disease soon confined Hawking to a wheelchair. He lost the use of his voice and became reliant on a machine to speak. But with two marriages, three children and a meteoric academic career, few can argue that the physicist has led an active life both privately and professionally.
The scientist has often confessed that although gifted as a student he was lazy. It wasn't until his diagnosis that he began to concentrate on his studies. His work paid off and in 1979 he was appointed Lucasian Professor at Cambridge University - a chair once held by Sir Isaac Newton.
It was while working at Cambridge that Hawking developed some of his most important contributions to physics.
Using Albert Einstein's theory of general relativity, he proved that the Big Bang must been triggered some 14 billion years ago with a so-called "singularity"- an unimaginable tiny dot that the current formulas and laws still do not grasp.
His most beloved area of focus, however, proved to be black holes - the galactic monsters whose gravity devours anything that gets close to them. In one of his most important discoveries, he found that back holes do not have an infinite life span. In a theory now known as "Hawking radiation," he found that black holes emit radiation causing them to evaporate slowly.
Without any definitive proof of his theory, however, Hawking has not been awarded the Nobel Prize for Physics. "One could measure the outgoing radiation from black holes, but unfortunately, there seem to be none in our area," he said.
In spite of a lack of conclusive evidence, most experts are convinced of the existence of Hawking radiation.
It was "a discovery which will still be relevant in hundreds of years," said Bruce Allen, director of the Max Planck Institute for Gravitational Physics in Hanover and one of Hawking's former students. "There are few discoveries quite like this."
But is Hawking really - as many people have suggested - a second Albert Einstein? Not according to some of his academic colleagues.
"Hawking's contributions are certainly not as significant as those of Einstein," said Klaus Fredenhagen a physics professor from the University of Hamburg. "With the theory of relativity, Einstein discovered something completely new, which was previously unknown."
Hawking is indeed known best for working within the context of existing theories and making important advances therein.
Fundamental physics made easy
Above all, Hawking stands out for his success in making cosmology palatable to a wide audience.
In 1988 he published his book "A Brief History of Time." It soon became the most successful popular-science work of all time. Although the material is far from simple, the book sold millions of copies worldwide.
Already an established figure in the field of science, he went on to co-author a series of children's of books with his daughter Lucy.
The Briton also knows how to market himself. Among a number of fictional cameos, he has featured in the science-fiction series "Star Trek" where he won a game of poker against Einstein and Newton.
In April 2007 he also fulfilled a life-long wish to experience a state of absolute weightlessness. Pictures of the genius during a NASA zero-gravity flight spread around the world. Once the space simulator had landed Hawking declared, "Space - here I come."
That he embarked on such an excursion at a late stage in life is nothing short of a medical miracle. "I've known him since 1980," Allen said. "I never thought that Stephen would live quite as long."
As a scientist, Hawking's colleagues have described him as extremely "intense." From a young age he was unable to scribble his formulas on paper or on boards, as many other physicists are known to do. Instead, in a show of his extreme capacity for concentration, he performed the highly complex calculations in his head.
"He is extremely friendly and approachable, even though he is so famous," said Fay Dowker, one of Hawking's former doctoral students and now a physicist at Imperial College London.
Remembering how she once went into the Institute with a newly shaven head she recalled "Hawking just grinned at me and asked 'Fay, why did you pick a fight with a lawnmower?"
In November 2016, as a member of the Pontifical Academy of Sciences, Hawking met Pope Francis at the Vatican, despite referring to himself as an atheist. Indeed, the physicist claims that God is unnecessary because no such deity is needed for the universe to have come about.
Always keen to offer his take on contemporary matters, Hawking has recently warned against contact with alien life forms, vehemently criticized the Brexit, called for a ban on the use of so-called killer robots, and accused the world of failure in the Syrian conflict