The Great Courses Professors Remember Stephen Hawking

The Great Courses Blog

On Wednesday, March 14 2018, the world lost physicist, author, and director of research at the Centre for Theoretical Cosmology at the University of Cambridge, Stephen Hawking.

We reached out to a handful of our professors for their thoughts on the man that forever changed our understanding of the physical universe.

Image of Stephen Hawking on stage

Professor Benjamin Schumacher, Ph.D.

Image of Professor Benjamin Schumacher, Ph.D. for article about Stephen HawkingYesterday, we woke to the news that we’d lost Stephen Hawking, surely one of the great physicists and most remarkable personalities of our time. I knew him, somewhat. We had dined together and met at conferences, and we shared many friends in common. He was always a hero to me.

He was brilliant, of course. And he was a man of immense personal courage. And as a scientist, he always worked on the hardest, most significant, most fundamental questions. And he wrote in a wonderfully lucid way, even when he was writing about pretty abstruse mathematics. I admired all of that. But I think the thing that I will treasure most about him was his sense of fun. He took such obvious delight in life, and in this business of uncovering the secrets of nature. His most characteristic expression was a sort of grin, and it was infectious. We’re learning wonderful things together about the universe; why shouldn’t that bring us joy?

Now as it happens, I’m about to get on a train to go and give a theoretical physics talk at Cambridge University, where Hawking made his home. And I’m sure I and my colleagues there will swap Hawking stories over dinner. I even have a few of my own, like the time I saw him join some flamenco dancers on stage in his motorized wheelchair. There will be a lot of laughter, and a deep appreciation of what he did and what he left for us. 

My own first scientific work was on black hole thermodynamics, a field that he’d invented with his discovery of the quantum radiation emitted by black holes. That was probably the most significant of his accomplishments, but there were many more. I have a special love of his early work with Roger Penrose on Einstein’s general relativity, the so-called singularity theorems, which really revolutionized the way we think about the formation of black holes and the big bang.

His was a life well-lived, and we will miss him.

Professor Alex Filippenko, Ph.D.

Image of Professor Alex Filippenko, Ph.D.Well, I’m certainly very saddened by the passing of Stephen Hawking. A great man, a great scientist. But I’m glad that he was able to live a long and full life—more than 50 years longer than had predicted by those who diagnosed him with ALS when he was in his early 20s. And he achieved so much, overcoming enormous obstacles. So against all odds, we get all of this fantastic work.

He was certainly an inspiration to me and to many others. I mean, if he can do all of this stuff, largely in his head, confined to a wheelchair, then certainly the rest of us should be motivated to do the things that we would like to do. I mean, he could’ve easily given up, he could’ve just said, “Forget it, the world has given me a bad hand and I’m not going to do anything about it.” But here he was, completely confined to his wheelchair, even not able to speak the last few decades of his life. And yet, in his head, he could do all of these calculations and convey them to his colleagues who would write them down. What an inspiration.

Probably his greatest legacy will be the prediction that black holes can evaporate through a quantum mechanical process—particles just go flitting away, gradually over time. It takes a very long time for a black hole to fully evaporate.

Of course, he wrote about his theories in a popular book, A Brief History of Time. And it’s pretty rough going after about chapter 3 or 4. In fact, I like to say to joke, sometimes, that it’s the most purchased but least-read through completion book of all time. You know, people buy it and they put it on their coffee tables, they have dinner parties and people say, “Oh, you read Hawking, you must be really smart!” Well, I don’t know of many people who fully understand that book. It’s pretty rough going. Nevertheless, it sold millions and millions of copies. He’s certainly brought these interesting issues of black holes and general relativity and quantum physics to the public eye.

And this is the first step in the unification of quantum physics—the physics of the very small—and general relativity—the physics of the very large. Theoretical physicists have been after such a theory for decades. And although we still don’t have one that’s completely proven and unique, it’s generally thought that black hole evaporation will be something that is a feature, a consequence, of any successful quantum theory of gravity. And so, Hawking did those first baby steps into a unified theory.

Professor Felix J. Lockman, Ph.D.

Image of Professor Felix J. Lockman, Ph.D.

Hawking was a physicist who made brilliant advances in our understanding of black holes, and in other topics, ranging from physics to cosmology. But I think that his effect on us is actually more profound. Think about it: Hawking was a guy who, because of a disease, had severe limitations. He was severely confined, and yet his mind ranged over the universe, contemplating things great and small. I think that Hawking’s very existence reminded us of the fact that we’re all profoundly confined. We’re confined by the limits on our intellect, we’re confined by our location on Earth, and we’re confined by the brief span of our lives. And yet, in some way, like Hawking, we’re trying to make sense of the puzzle of the universe.

So I think that Hawking’s book, A Brief History of Time, struck a nerve, struck a resonance in all of us, because it reminded us of what humanity has been possible to learn, despite all of our limitations. I think his book stands as a symbol of the power of the human mind to transcend the boundaries of our lives.

Professor Sean Carroll, Ph.D.

Image of Professor Sean Carroll, Ph.D.I got to meet Stephen Hawking in person many times. In fact, when I was a graduate student getting my PhD, he called me up in my office in order to offer me a job as a postdoctoral researcher—a 3-year research position over in Cambridge.

Unfortunately, I had to turn him down for various reasons and ended up going to MIT. Three years later, it was time to get a new job. I applied to Cambridge again. Hawking offered me another job. I had to turn him down again, and ended up going to UC Santa Barbara, the Institute for Theoretical Physics there. And it was at UC Santa Barbara when I finally met Hawking and talked to him face-to-face for the first time. We were all walking to lunch—Hawking used to visit California almost every year, and he would drop by both CalTech and Santa Barbara.

So one day in Santa Barbara, we were walking to lunch, and I was standing next to Raphael Bousso, one of Hawking’s graduate students, and I said, “Raphael, you should introduce me to Stephen, I’ve never actually said hi to him before.” But as a joke, I added, “I hope he’s not mad at me. He did once offer me a job and I turned him down.” And Raphael says, “Oh, don’t worry about that, there’s this one guy who turned him down twice.” So I had to explain that yes, that was me. And Raphael instantly ran over to Stephen Hawking, saying, “Stephen, Stephen, this is the guy! This is the guy who turned you down twice!”

Image of Stephen Hawking in zero G aircraft

Right now, right this very moment, my research career is focused on perhaps Hawking’s greatest legacy: the black hole information loss paradox. You take a black hole, you throw some information in, like a book or something like that, and Hawking showed that the black hole eventually evaporates. So what happens to the information that was contained in the book? By the laws of physics, as we understand them, it should go somewhere; but naively, Hawking’s calculations say it doesn’t go anywhere at all—it’s just destroyed. So decades later, after he posited this puzzle back in the 1970s, we still don’t know what the answer is. We’re still struggling to figure this out.

In my mind, this puzzle was Stephen Hawking’s greatest gift to physics. That’s what physicists love: some question that’s easy to ask and very, very hard to answer. We’re all hopeful that thinking about this as carefully as we can will help us reconcile quantum mechanics with gravity. And if so, I think that Stephen Hawking would be very proud to know the role that he played in doing that.

Professor Dan Hooper, Ph.D.

Image of Professor Dan Hooper, Ph.D.Hawking will be sorely missed, not only for his research, which was profound and influential, but also for his ability to inspire and to communicate science to people old and young alike.

I first learned of Stephen Hawking when I was an undergraduate physics student. One of my professors gave me a copy of A Brief History of Time, and I just adored it—I loved everything about it. At that point in my education, I’d really only learned about some pretty mundane parts of physics; I learned about objects sliding down inclined planes, and I learned a little bit about electricity and magnetism and motion and things like this, but that doesn’t capture any of the wonder of modern physics. And what I mean by modern physics is encapsulated by Hawking’s work.

This is an amazing book. If you haven’t read it, by all means, seek it out. It is poetic and it captures the wonder and amazement of general relativity and quantum mechanics in a way that very few books have ever done. You will not regret it.

In particular, he showed that the entropy or information content stored in a black hole was proportional not to the volume of the black hole, like everyone would’ve expected, but to the surface area of that black hole.

This plays a huge role in our understanding of quantum gravity. And though we really don’t understand quantum gravity yet, whatever the answers are to the questions that quantum gravity is trying to address, Hawking’s work will certainly play a major role in that. It’s hard to overstate how important Hawking’s contributions were in this respect.

This transcript was taken from a special lecture on The Great Courses Plus. You can watch it here.
Image credits:
Jim Campbell/Aero-News Network/NASA
NASA/Paul E. Alers