To Infinity and Beyond
Stephen Hawking’s insights about the universe were profound—but his insights into humanity were even more important.
The last time I saw Stephen Hawking was in Stockholm in 2015. After our small science workshop, he delivered a lecture in the city’s largest venue. As usual, the event was sold out and packed with young people.
Hawking arrived on stage with his gentle smile and legendary wheelchair and started playing the lecture he had recorded in advance. In it, he recounted his latest attempts to understand the future of black holes, offered some quips on the meaning of life, and poked fun at various targets with a grin that betrayed his innate rebelliousness. The audience was transfixed.
In the 10 months since Hawking died, I have been considering his legacy, and I keep returning to his final words from that event in Stockholm. They were a declaration of love for life under the most difficult conditions. “If you feel you are in a black hole, don’t give up,” he said. “There’s a way out.”
Hawking was a very good physicist, among the best of his generation—although not the new Albert Einstein or Isaac Newton that journalists made him out to be. (Hawking liked to playfully encourage this exaggeration.) His major discovery was the fact that black holes radiate heat like a stove. Today, that heat is called Hawking radiation, and although it has yet to be observed—and is unlikely to be anytime soon because it is so weak—its existence has been widely accepted.
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Hawking radiation is important because it involves both gravity and quantum theory—that is, it gestures toward reconciling the two major, but seemingly contradictory, advances in physics of the 20th century, the discoveries of space-time and the laws of the submicroscopic world. With his finding, Hawking offered a clue toward solving the great puzzle of contemporary physics: understanding quantum gravity, the theory that describes all subatomic aspects of space and time. Much current research, including my own, refers to Hawking’s breakthrough or tries to deepen it.
Hawking summed up his discovery in a beautiful formula, which gives the temperature T of the radiation emitted by a nonrotating black hole with mass M. It is extremely simple:
T = ħc³/8πGMk. No other formula so elegantly pulls together all the basic chapters of physics: the Planck constant ħ of quantum theory, the speed of light c of relativity, the Newtonian constant G of gravitation, and the Boltzmann constant k of thermodynamics. Hawking was so proud of his formula (rightly so) that before his death he asked that it be inscribed on his gravestone.
Hawking’s greatest achievement, however, lies in his humanity. A wheelchair user due to early-onset ALS, he gradually lost control of most of the muscles in his body. At the end of his life, he was only able to communicate with the public via the thin thread of a software that read the movements of his eyes and cheek muscles and translated them into letters and then words, which were ultimately pronounced by his vocal synthesizer. Even watching this painfully slow process was exhausting.
Yet the voice of that synthesizer reached the whole world. Hawking, a Brit, managed to make that famous American-accented metallic voice his own and a natural channel for his brilliant intelligence and irony. Although his body kept deteriorating, his spirit did not; he continued to produce quality physics until the very end and also wrote books that reached an immense audience. In the 30 years since its publication, A Brief History of Time has sold more than 10 million copies, and it still inspires young people everywhere to study and love the universe.
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In a world increasingly beset by localism, greed, religious obscurantism, shortsightedness, and conflict, Hawking’s ideas stood out as a reminder of the best of the Enlightenment. That was certainly true in the positions he took on public policies related to his own personal circumstance, including his calls to protect the rights of the disabled and to legalize assisted suicide for the terminally ill. But it was also true of his vision of the universe, the vastness of which was a constant reminder of the fragility and communal nature of human destiny.
Hawking didn’t find his strength in any sort of transcendent consolations; although he liked to evoke God for rhetorical effect, he was resolutely atheist. Instead, Hawking continuously reminded us that humanity could survive only by collaborating, by leaving aside puerile beliefs in the greatness of single nations or individuals. In 2006, he posted, unprompted, an open query on the internet: “In a world that is in chaos politically, socially and environmentally, how can the human race sustain another 100 years?” It wasn’t a rhetorical question but a sincere—and successful—prompt to solicit answers from as many others as possible.
The thin thread that connected Hawking to us is now broken. But before dissolving into the immensity of that vast cosmos that he loved so dearly, he left us with his most precious gift: the luminous example that was his force of life, curiosity, intelligence, and vision. It’s the reason Hawking will continue to live for many more years—in our science, in our memory, and in our common understanding of what we are in the universe. For that, we should all be grateful.
This article originally appeared in the Winter 2019 issue of Foreign Policy magazine.
Correction, Jan. 22, 2019: In an earlier version of this article, the equation T = ħc³/8πGMk appeared to read T = ħc3/8πGMk due to a formatting error.
Carlo Rovelli is an Italian theoretical physicist and writer.
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