To the editors:
Bernard Carr has mounted a sensitive and effective defense against the slings and arrows launched at Stephen Hawking by Charles Seife in his offensively named and outrageously written book. Hawking should indeed be universally regarded as an icon of twentieth-century science! His seminal contributions to physics and cosmology are admired and respected by virtually all his colleagues and by the countless friends he made throughout the world.1 I had been fascinated half a century ago upon learning of Hawking’s notion, inspired by Jacob Bekenstein, of thermal emission from black holes. Nobody has yet observed Hawking radiation, nor is it likely that anyone ever shall, yet few physicists doubt its existence. The discovery of Hawking radiation is one of Stephen’s finest yet most frustrating triumphs. Even now, this phenomenon continues to challenge theorists,2 and it brings to mind what might have been my first meeting with Stephen in 1981, at an elegant San Francisco venue. Werner Erhard founded and profited from Erhard Seminar Training, but he was also a fanatic for fundamental physics. Beginning in the 1970s, his foundation funded a series of ten annual physics conferences that were held at his Pacific Heights mansion at 1945 Franklin Street. Many renowned physicists attended one or more of these sessions, including Nobel laureates Richard Feynman, Murray Gell-Mann, Gerard ’t Hooft, Kip Thorne, and Frank Wilczek. I came to only one such meeting, but it was the only one that would significantly affect the history of physics.
The most relevant attendees were Leonard Susskind, ’t Hooft, and Hawking. Lenny tells the tale excitingly in his book The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics. After describing how Stephen raced down one of San Francisco’s more steeply inclined streets in his motorized wheelchair, Lenny writes,
Hawking is very much a daredevil physicist. But perhaps his boldest move ever was the bomb he dropped in Werner’s attic. … Stephen claimed that “information is lost as black holes evaporate,” and worse, he seemed to prove it. If that were true, Gerard and I realized, the foundations of our subject were destroyed. … Everyone else had left. I can still see the intense frown on Gerard’s face and the amused smile on Stephen’s. It was an electric moment.3
According to quantum mechanics, information is rigorously conserved and cannot be lost. A paradox had arisen and the debate between Stephen and his two friends would continue intensely for decades, as would their close friendship. Gerard addressed the issue with his imaginative holographic principle, which Lenny refined in a paper with the intriguing title “The World as a Hologram.”4 The paradox seemed to some to have been evaded, but Stephen and others felt that it had been replaced by an enigma. A wager was placed in 1997 between Stephen and Kip on one side, both of whom claimed that information swallowed by a black hole is irretrievably lost, and John Preskill on the other, who insisted that the information within an evaporating black hole is somehow encoded in its Hawking radiation. Subsequent work by Juan Maldacena reinforced the holographic view of Lenny and Gerard, thereby convincing Stephen to reluctantly concede in 2004. Nonetheless, physicists still struggle to fully resolve Hawking’s conundrum. For example, Netta Engelhardt of MIT shared the 2021 New Horizons in Physics Prize along with three other young theorists “for calculating the quantum information content of a black hole and its radiation.”5
I can’t resist noting that Stephen, John, and Kip had engaged in two prior wagers. The first was placed in 1974 when John and Kip argued that Cygnus X-1 was likely to be a black hole. Stephen disagreed, but was forced to concede in 1990 when evidence that it was a black hole became convincing. One year later, Stephen wagered that naked singularities could exist, while John and Kip thought otherwise. Stephen lost this bet in 1997, the very same year that he placed the last of his lost bets, but stellar scientists don’t need good betting averages.
Stephen often visited the Boston area to deliver standing-room-only lectures at MIT, Harvard University, and Tufts University, as well as to present at Boston Children’s Hospital and at several Macworld extravaganzas. On one unforgettable occasion, he and I were both at Harvard attending a seminar given by my friend and colleague Sidney Coleman. Suddenly, Stephen made odd sounds and fell to the floor. We rushed to his side, fearing he was having a choking fit, but once he was restored to his chair, Stephen explained that he was perfectly fine but had laughed a bit too hard at one of Sidney’s better jokes.
When Stephen was invited to receive an honorary degree from Harvard, I was appointed as his co-escort. On the evening before the ceremony, my wife Joan and I attended cocktails and dinner with Stephen, his several attendants, and the other honorands and their escorts. When Stephen asked to be introduced to Ella Fitzgerald, who was also an honorand, Joan did so, whereupon Ella and Stephen struck up an immediate friendship. Ella had long been his favorite singer, but she had never before heard of him. As the dinner came to its early end, we asked Stephen’s attendants whether we all might round out the evening at our home. They made it quite clear that the challenges of putting Stephen to bed and prepping him in the morning made our plan untenable.
Stephen spent the next morning with the other honorands, for a brief reception and brunch prior to the ceremony. Stephen’s co-escort, Professor-physician David Abramson, attended the event and reported on it years afterward.6 When Abramson pressed Stephen to explain why he wrote A Brief History of Time, Stephen had his computer reply “I needed the money.” The National Health Service could not provide the 24/7 care upon which Stephen’s life depended. When Ella agreed to sing, Stephen hurriedly turned his chair toward her. When Helmut Kohl, another honorand, arose to speak, Abramson offered to turn Stephen’s chair, but he declined, saying, “Why would I want to listen to that man?” Later, fully robed, I duly escorted Stephen to his place on the stage, then retreated to rejoin my physics colleagues seated in the audience. My duties were done, but not those of Dr. Abramson. Noticing that Stephen was not breathing and could neither move nor speak, the quick-thinking doctor surreptitiously rushed Stephen to Harvard’s wisely deployed emergency medical service, thereby averting a catastrophe. Susskind may have saved quantum mechanics from Hawking, but Dr. Abramson saved Hawking from Harvard.
Stephen’s final appearance at Harvard was in 2016, where his speech enthralled a packed house of over 1,000 rapt listeners, from freshmen to faculty. Sadly, I missed this lecture because by then I had left Harvard for Boston University, upon whose hallowed land Stephen’s motorized wheelchair never rolled.
