A few weeks before his death, on March 14, 2018, Stephen Hawking welcomed Belgian Thomas Hertog, with whom he had worked for two decades, to his office at the University of Cambridge for the last time. The most famous cosmologist whispers to his friend that it is time to write a new book to detail his theory of the fundamentals of the universe. Five years later, the professor of theoretical physics at the University of Louvain in Belgium published “The Origin of Time” (Éd. Odile Jacob), a book as clear as it is rich, which tells the story of a fruitful collaboration between two people one meets that with a capital H of physics, but also of biology.
As a student, then 22 years old, Thomas Hertog met the man in 1998 who was to become his mentor. Seeing if he could become his thesis supervisor, Hawking immediately asked him what he thought of the multiverse, a theory then in vogue that he denied. Against the background of trying to understand how our universe could be “set up” to make life possible.
Go back in time…until it disappeared
“Stephen was one of the few scientists who was truly driven by big philosophical questions. He found this to be the heart of cosmology. He had an approach that I would describe as almost humanistic in relation to his field of research. These are the same questions that led me to theoretical physics,” he confides. “I immediately had the feeling of arriving at my destination. I have never met a professor, a scientist, who is guided by these questions. It was a kind of revelation for me, this first conversation,” the 47-year-old physicist continues.
Stephen Hawking then hired a graduate student each year to work on either the Big Bang or black holes, two areas where physics takes extreme turns. Most of the time the collaboration ended there. Not with Thomas Hertog. Together they will develop a revolutionary theory of the universe.
“In the normal perspective that has grown over the centuries, the laws of physics are eternal truths that go beyond the universe,” he first reminds of the cosmologist. Conversely, he and Hawking envision the laws of physics evolving with the universe in an approach akin to Charles Darwin’s vision of the evolution of species, which in his time confounded the fixed conception we had of the animal kingdom (“The Origin of Time” is also an allusion to “The Origin of Species”, the key work of the British naturalist).
more concrete? “As we go into the past, physics becomes simpler, evaporates, and the final transition, which is at the heart of our theory, is that even the dimension of time disappears. The universe would therefore not be the fruit of immutable physical laws. These laws would have arisen without determinism and would have evolved with it and would have become more complex over time…
Math by day, philosophy by night
This is bound to change everything, and the development of this new paradigm did not happen overnight. “Between 2005 and 2010 there was a change: we had to give up our view of the cosmos, which we looked at from the outside, we placed ourselves in it. After 2011, the duo anchored this new perspective in a mathematical model for a new theory.
And about the future, what does it tell us? Thomas Hertog is happy about the question: “We shouldn’t think dogmatically that the laws of physics will remain the same for eternity. »
VIDEO. This is the first image of a black hole at the center of our galaxy, the Milky Way.
So much for the mysteries of great history. But this book also tells the story of the little one, that very special collaboration with Hawking, paralyzed by Charcot’s disease and almost unable to communicate at the end of his life. Of this final phase, Hertog writes: “I stood in front of him, clearly occupying his field of view and testing his wits by bombarding him with questions. Stephen’s eyes lit up when my arguments matched his intuition. »
For a long time, this atypical dialogue did not present any difficulties, the scientist assures us. “We worked next door. If it took five hours, it took five hours… A little conversation could last all day. It suited me because it gave me time to think,” he laughs. “We were in our search bubble. During the day we approached the purely scientific aspects, calculations, mathematics… In the evening we discussed more freely. »
However, his disability isolated Stephen Hawking from the global scientific community. “There was a real danger that he would be separated from it. Among cosmologists there are several ideas that coexist. Unfortunately, towards the end of his life, Hawking found it difficult to participate in such debates. I had to explain a bit to him what was going on in the research. »
If Hawking’s contribution is unanimously acknowledged, Hertog concedes that his vision is open to debate: “This book can spark a transdisciplinary debate involving philosophers, biologists, the general public…”
the origin of time
“The Origin of Time: Stephen Hawking’s Final Theory,” by Thomas Hertog, Ed. Odile Jacob, 24.90 euros.