Professor Stephen Hawking, who died early today at the age of 76, possessed one of the greatest brains since Einstein and helped make major advances in our understanding of the Universe.

Confined to a wheelchair, he was barely able to move. Just a twitch of a cheek muscle allowed him to speak via a machine in his familiar robotic tones.

Yet despite his physical limitations, Hawking had a mind that was able to roam further than anyone else alive – to the outer limits of the Universe.

He once declared: “My goal is simple. It is complete understanding of the Universe, why it is as it is and why it exists at all”.

Equipped with an unparalleled understanding of physics, Hawking could think outside the box.

His special interest was in black holes – collapsed regions of the Universe so dense that normal laws of physics break down.

It was commonly thought that they were a kind of cosmic plughole from which nothing, not even light, could escape But in a stroke of brilliance, Hawking explained that black holes leak energy back into space and will eventually evaporate.

It was a completely unexpected idea that rocked the science community. The phenomenon was named Hawking radiation after his discovery.

Hawking was keen to investigate Einstein’s theory of general relativity which is the foundation of modern physics, explaining how space and time are bound together by gravity.

He explored how the Universe began in a Big Bang, pondered the possibility of other universes, and suggested that so-called wormholes might provide short cuts across space and time.

But as well as studying the cosmos on a vast scale, Hawking was also fascinated by the nature of matter on its tiniest scale – atoms and particles within them.

Hawking became Lucasian Professor of Mathematics at the University of Cambridge, a distinguished post once held by Isaac Newton. An eloquent tribute to him was made by his Cambridge colleague, the UK’s Astronomer Royal Lord Martin Rees.

His book A Brief History Of Time became an unlikely bestseller, challenging the reader as never before. Few can have made it to the end, yet it spent four years on best-seller lists around the world.

Despite the complex nature of his research, Hawking was a brilliant communicator and travelled the world explaining science to the public.

And his huge sense of fun allowed him to take time off from his academic studies to make guest appearances in shows including The Simpsons, Star Trek and The Big Bang Theory. His familiar voice was also heard on Pink Floyd’s Keep Talking.

Hawking used his scientific authority to warn of the dangers facing the human race. He advised that if signals were ever detected from aliens, we should be wary about answering them in case they were hostile.

But he also urged humanity to make urgent plans to expand into space and colonise other worlds because he thought Earth was becoming overcrowded.

Hawking joined up with Project Breakthrough to support plans to send a fleet of miniature starships to our nearest star, Proxima Centauri.

Despite his disabilities, Hawking had a sense of adventure. He booked a flight into space with Virgin Galactic that he will now never make.

But he did experience weightlessness aboard a “vomit comet” – an aircraft flying out of Cape Canaveral, Florida, that is used to train astronauts.

Though Hawking’s ideas about travel through wormholes and missions to the stars are currently science fiction, his work has inspired space scientists.

Paying tribute, NASA Administrator Robert Lightfoot said: “Today, the world lost a giant among men, whose impact cannot be overstated. Our condolences go out to the family and friends of Stephen Hawking.

“Stephen’s breakthroughs in the fields of physics and astronomy not only changed how we view the cosmos, but also has played, and will continue to play, a pivotal role in shaping NASA’s efforts to explore our Solar System and beyond.”

Hawking’s big ideas

Stephen Hawking made major contributions to our understanding of the Universe right from his days as a student.

Hawking based his work on Einstein’s theory of general relativity, which showed how space and time are bound together by gravity.

Hawking’s early work was fundamental in proving the existence of black holes – regions of the Universe so dense that normal laws of physics break down.

In the 1960s, there were still competing views as to how the Universe came to be. Some argued for a “Big Bang” beginning, and others that it had always been there in a “Steady State”.

Hawking’s PhD thesis provided mathematical evidence for the Big Bang. If you wound back the Universe 14 billion years, you would find it all condensed into a single tiny point called a singularity.

Everything exploded into existence from this singularity, said Hawking. It was rather like a black hole in reverse.

Though this produced the Universe, Hawking argued that the concept of a beginning was meaningless and there was no point asking what came before it. That was because time itself only came into being at the moment of the Big Bang.

Black holes were a source of fascination for Hawking. He drew up the laws explaining the mechanics of how and why they exist.

It was commonly thought that a black hole was a kind of cosmic plughole from which nothing, not even light, could escape.

But in a stroke of brilliance, Hawking put forward evidence that black holes leak energy into space and will eventually evaporate.

It was a completely unexpected idea that rocked the science community. The phenomenon was his most important finding and was named Hawking radiation after him.

During the Big Bang, Hawking suggested, some lumps of matter could have collapsed into miniature black holes, each smaller than an atom yet weighing billions of tons.

These mini black holes would have been so hot that each would have exploded with the force of a million hydrogen bombs.

Related: Did the first black holes form right after the Big Bang?

But as well as studying the cosmos on a vast scale, Hawking was also fascinated by the nature of matter on its tiniest scale – atoms and the sub-atomic particles within them.

He linked this study of so-called quantum theory with what was occurring on a vast scale in the Universe.

Hawking calculated how the Universe grew rapidly in size after the Big Bang. He found that this expansion was not smooth but contained tiny irregularities which produced stars and galaxies.

Other fields of study included the possibility that black holes might be the seeds of other, baby universes.

And in an idea reminiscent of Doctor Who, he suggested that wormholes in the space-time continuum could provide short cuts across the Universe.