Most people have heard of Stephen Hawking—they may misspell or mispronounce his name, but they know who he is. That puts him in a very select group of scientists that includes Einstein, Newton, Galileo, Darwin and, at most, one or two others.
Every one of these individuals was a very great scientist indeed. But there have been many great scientists who are almost completely unknown to the general public. Why the difference? The humorist Max Beerbohm once quipped that Newton’s popular renown was partly due to the story of the apple landing on his head. Galileo certainly would not be a household name without the Roman Inquisition. And one cannot help thinking that Einstein’s wild hair contributed to his mystique.
In the case of Hawking, it is likely that his disability (ALS or “Lou Gehrig’s disease”) did much to fire the public’s imagination. He seemed like a purely mental being, someone whose intellect was so vast that he had left ordinary physicality behind. No merely bodily limitation could hold back that powerful mind. But whatever the causes of the public’s interest, he truly was one of the greatest scientists of his generation.
There were actually three Stephen Hawkings. There was Hawking the physicist, Hawking the philosopher and Hawking the prophet-sage.
There were actually three Stephen Hawkings.
As a physicist, Hawking made contributions that will be remembered and studied as long as science is done. His greatest discovery is that black holes radiate energy. This came as a great surprise. A black hole is a region where gravitation is so strong that nothing can escape it, including light—hence the name “black.” Anything that approaches too close to a black hole is ineluctably pulled toward its center and crushed to a point. What happens inside a black hole stays inside a black hole. Or so everyone thought. In the 1970s, Hawking showed that quantum mechanics causes black holes to radiate energy. This “Hawking radiation” can cause a black hole to evaporate completely, so that everything that has ever fallen into it ends up being radiated as particles back out into space.
This leads to a deep puzzle, as Hawking himself pointed out. The basic principles of quantum mechanics say that physical processes cannot destroy information. But Hawking’s calculations seemed to show that the radiation remaining after a black hole has evaporated does not “remember” anything about the things that fell into it. If true, this would imply that something is wrong with quantum mechanics—a very big deal. The consensus now, however, is that black holes do obey the laws of quantum mechanics and do not destroy information. How this works in detail remains deeply mysterious. The “black hole information paradox” continues to vex the world’s greatest physicists.
Another subject on which Hawking did important work is what happened at the first moments of the universe. He did not answer this question. To do so would require having a complete and consistent theory of quantum gravity and knowing how to apply it to the Big Bang, which as yet no one can do. Nevertheless, Hawking, with colleague James Hartle, proposed an interesting highly speculative scenario according to which the universe popped into existence by something called a quantum fluctuation. This is heady stuff, and it seems indeed to have gone to Hawking’s head. He became Hawking the philosopher.
There have been great scientists who were also great philosophers. Hawking, unfortunately, was not one of them.
There have been great physicists and mathematicians who were also great philosophers (Pascal, Descartes and Leibniz come to mind). Hawking, unfortunately, was not one of them. It was Leibniz himself who famously asked, “Why is there something rather than nothing?” The answer of Christians, including Leibniz, is “God.” The answer for Hawking was “quantum gravity,” which can produce universes by quantum fluctuations. “But who,” one might ask, “ordained that there should be quantum gravity?” To this, Hawking gave no answer.
To his credit, however, there was a time when Hawking saw things more clearly. In his famous 1988 book, A Brief History of Time, he noted that physics is “just a set of rules and equations.” “What is it,” he asked, “that breathes fire into those equations and makes a universe for them to describe? The usual approach of science of constructing a mathematical model cannot answer the question of why there should be a universe for the model to describe.” Exactly. There is no logical necessity for there to be any real thing described by the mathematics of quantum gravity.
It may well be that if there is a real universe, and if it is described by the mathematics of quantum gravity, the universe may have to have a beginning that unfolds in a certain way. But Leibniz’s question remains: why is there a real universe rather than nothing at all? One could say that God is the answer. One could consistently say that there is no answer. But it is nonsense to say that quantum gravity is the answer since, as Hawking himself once grasped, a mere set of equations cannot confer reality on anything.
Having become the most famous scientist in the world, and having answered (as he thought) the question of existence, what was left for Hawking to do? To be a prophet and a sage. To hold forth on the fate of humanity, extraterrestrials, ecological disaster, colonization of space and machines taking over the world.
Stephen Hawking the sage will be mercifully forgotten. But the work of Stephen Hawking the physicist will live on.