EXPERT REACTION: Physicist Professor Stephen Hawking dies aged 76

Stephen Hawking had the outstanding ability of combining the laws of gravity with the laws of quantum physics to derive results that are valid in the unexplored realm of quantum gravity.  His genius will be dearly missed.

I meet Steve Hawking in Cambridge in 1970 when I was working there with Fred Hoyle. One outcome of those discussions with Steve was an attempt we later made to detect exploding black holes - the inevitable fate for blackholes emitting Hawking radiation.

Our experiment using a telescope in the Netherlands involved another astronomer, Peter Shaver, and an engineer, John O’Sullivan. We didn’t detect any exploding blackholes but for John O’Sullivan this provided the initial trigger that eventually led him on the path to develop WiFi in CSIRO decades later.

So that is how Steve Hawking indirectly influenced the development of Wi-Fi which has greatly enriched the world today, yet is very far removed from gravitation and cosmology.

In a field that's often dominated by large teams of scientists and huge instruments, Stephen Hawking worked with a few collaborators and the resources of his mind, but still made major advances. He had the rare knack of asking unusual but illuminating questions ... what really happens at the event horizon of a black hole?

He not only advanced our understanding of the universe and its contents by his discoveries, but by provoking us to think about how the cosmos works. His books for the public seemed to show great respect for his audience, assuming that, even if they didn't fully understand him, they still would be interested in what a cosmologist had to say about the universe in all its wonder and strangeness.

Hawking was a true giant of the field, with fundamental discoveries about black holes and the nature of the Universe

Stephen Hawking inspired generations of scientists. I remember reading a brief history of time as a sixteen year old. It certainly helped to set me on my path to being an astrophysicist.

As a graduate student at Cambridge, I was fortunate to have Stephen Hawking as a lecturer on gravitational physics and black holes. He tended to wheel around the low dais at the front of the room while he delivered his pre-recorded lecture and a graduate student wrote equations on the blackboard. One time he rolled too far and his wheelchair tipped over the edge, depositing him on the floor. While everyone rushed to pick him up and dust him off, he was busy tapping on his wheelchair keyboard. When the lecture re-started he announced, in that instantly recognisable voice, “I fell off the edge of the world”.

A few years later, as a junior research fellow at Kings College, I very nearly achieved scientific infamy by running Hawking over as he zoomed out of the college gates and almost under the wheels of my car. I hit the brakes but he kept going, and I was left contemplating what my career prospects would have been as "the one who killed Stephen Hawking".

Hawking was a great scientist and an inspirational figure. The universe is better understood and more interesting because he was in it.

For myself and many scientists, I am sure this is one of those pieces of news that becomes a fiducial anchor point in the stream of memory: remember where you were when the news about Stephen Hawking broke? As a young Australian student studying in Cambridge, of course he was already the biggest of the pantheon of superstars that made places like that so alluring, but I did not anticipate my first encounter with him would make national headlines in Britain. Riding home late on our bicycles, my mate crashed into Hawking's wheelchair - which he drove around at some speed in those days and with no lights - on the quiet streets at the "backs" of the river Cam. This put both of them in hospital, and my friend on the front pages for all the wrong reasons. It was not until much later in my career after that I began to appreciate just why Hawking was such a titan in physics, but also more broadly in culture and modern society. While his contributions to deep questions in physics was profound, he also contributed to a wide array of extremely important contemporary debates and issues - things such as artificial intelligence, the building of a fair society, pitfalls and problems thrown up by disruptive technologies of tomorrow.

For a guy with such manifest physical challenges in life, it would be easy to expect them to live behind a screen of fame and to remain absorbed in the theoretical.

I always felt it a testament to luminosity of his intellect that he was so outwardly engaged in the world, and had such penetrating vision and passion for the wider concerns of society and ethics.

I am saddened to learn of the death of Professor Stephen Hawking. He was a constant presence in my life at the University of Cambridge, from my undergraduate days, when he could be seen driving his wheelchair ahead of a stream of traffic on Sidgwick Avenue, through meetings in the cafeteria in the Department of Applied Mathematics and Theoretical Physics to being a formal dinner guest at Churchill College in recent years. Stephen was an inspiration to all and will be sorely missed.

Hawking had a towering intellect and an infectious sense of humour. His logical and reasoning skill, coupled with a deep understanding of quantum theory and relativity allowed him to come up with several important ideas about the nature of the universe, black holes and the big bang. When his ideas were disproved, that spurred him on to create new links between seemingly different phenomena, bringing us brand new insights.

Hawking's most important scientific legacy is his idea that black holes slowly dissolve like aspirin in a glass of water. His impact on the public understanding of science is almost beyond measure. He had an infectious enthusiasm for his work and a passion for making it understandable to a lay audience. .

The death of Stephen Hawking will be a great loss to the astronomical and scientific community. He has been an inspiration to many a would-be astronomer and astrophysicist, and influenced many young boys and girls to take up careers in science and engineering.

The one and only Stephen Hawking will be renowned as one of the greatest minds of our time. His ideas shaped the direction of the fields of cosmology and theoretical physics. Throughout his extraordinary life, he demonstrated to all that the power of the mind can overcome all physical challenges.

Stephen Hawking was one of the greatest mathematical physicists of the second half of the twentieth century. His popular books made him one of the few pop-star-like famous physicists and inspired many curios teenagers to take up physics.  His scientific work shaped the research of two generations of scientists (myself included), while the textbook he co-authored more 45 years ago is simply called by everyone in the field as Hawking-Ellis.

His scientific contributions are too numerous to list here. Hawking is largely responsible for the three laws of the black hole dynamics that form the basis of our understanding of these objects the Detection of the gravitational waves have shown us how these laws work in practice.  Perhaps his most famous achievement is the derivation of Hawking radiation --- realization that the laws of quantum mechanics and their intrinsic uncertainty do something very dramatic to largely inert frozen stars that simply absorb everything that reaches them.

First they start dimly glowing, become hotter and brighter as they burn and finally  go out in a bang. This realisation turned a conjecture of a Jacob Bekenstein about entropy of black hole into a universal bound on information and exposed possibly one of the biggest unsolved problems in modern physics.

In Stephen Hawking the world had a man who was not merely good at science, but a man who was dedicated to the advancement of the human race through the application of intellect and critical reasoning.

He did this under great personal adversity, in particular in the face of an uncooperative body. He was an inspiration to many, and will continue to be for many years to come, as he should be.

It is often said that people leave large boots to be filled. In the case of Stephen Hawking, one could rather say that he has opened large areas of the cosmos to us, in time, space and understanding, that we will continue to struggle to fill for generations to come.

As a fellow scientist, I look in awe at what Stephen Hawking has achieved, especially given the incredible hurdles he has faced in life. His incredible intellect and insights have shaped the way we view the universe and our place in it, which may ultimately define who we are.

Stephen Hawking discovered that when the quantum laws governing the physics of atoms and elementary particles were applied to black holes, the

surprising outcome was that black holes actually must emit radiation – now called “Hawking radiation” – rather than being just bottomless pits into which matter and radiation fall into oblivion.

He showed that black holes are hot: they have a temperature. This astonishing connection between gravity and thermodynamics (the physics of heat) continues to have far-reaching implications for our understanding of the fundamental laws of the universe.

Stephen Hawking not only was a leader in cosmology and astrophysics, but also pushed us all - to challenge ourselves and the unknown. He leaves having inspired many of us and having helped us to tackle the big questions that humans have asked for centuries.

Professor Hawking was an inspiration to me to become not just a scientist, but a communicator of that science. His work as a cosmologist and discoveries in black hole physics were legendary. His best-known prediction, named by the community as Hawking Radiation, transformed black holes from inescapable gravitational prisons into objects that instead shrink and fade away over time.

His writings were inspirational to many scientists and enriched the lives of millions with the latest science and cosmic perspectives.
He was also wonderfully funny with a fantastic media savviness that propelled him into A-list celebrity stardom as few other scientists before. Through it all, of course, his illness made his achievements near-superhuman. How he manipulated Einstein’s equations in his mind when he could no longer hold a pen I can’t even begin to imagine.
 
While his many contributions will live on, there is no doubt that science and the wider world is the poorer for his passing.

A brilliant mind who gave so much both physically and conceptually has now left us. He will be missed amongst the amateur astronomical community.