“Before the Big Bang there was nothing, not even time”
When the brilliant young cosmologist Thomas Hertog (Leuven, 1975) walked through the olive-green door of the world-famous physicist Stephen Hawking’s office at Cambridge University in mid-June 1998, his life changed in surprising ways. Hawking asked him to work with him to develop a “new quantum theory of the Big Bang.” The doctoral project was an intensive collaboration that lasted about 20 years, ending only with the death of the Briton in 2018. “We were like a married couple, but only in cosmology,” admits the Belgian physicist, who now works at the University of Louvain. . Despite Hawking’s apparent communication difficulties in his final years, they wrote their posthumous paper together, disproving his 1980s idea of an infinite multiverse and opting for a finite, simpler one. In addition, they tried to find out why our Universe has conditions favorable for life. Their responses were collected by Hertog in the book On the Origin of Time: Stephen Hawking’s Latest Theory (Debate). What they both did, as the genie’s title card proclaimed, was to “go where Star Trek dare not go.” Hertog held a conference on Wednesday at CosmoCaixa (Barcelona).
“What was it like to be the right hand of a genius?”
“Something really intense, even overwhelming, seven days a week, 24 hours a day. Because Hawking made no distinction between his professional life and his personal life. But it was a great adventure because we felt that we were truly discovering a new paradigm of the universe. Moreover, Hawking was a joy. He had a great zest for life, so it was a lot of fun. He didn’t separate work from parties. Eventually everything got mixed up and went from one thing to another.
“Eventually, Hawking, who has amyotrophic lateral sclerosis (ALS), could no longer use the device to communicate. How did they talk?
“I asked him questions, and he answered me with facial expressions indicating certain words: yes, no, maybe I agree, no… and stuff like that. Then I could finish his sentences for him. Stephen and I were also surprised that it worked so well, but we had worked together for many years and had a common language. It was wonderful to discover that we could continue our research.
“Hawking changed his mind about the origin of the Universe, which meant abandoning the hypothesis of his world bestseller. What did this mean to him?
“He had no problem admitting it. This testifies to his genius. He was an explorer driven by a passion for knowledge. But it was not easy, it took many years to come to this conclusion. His theory in the 1980s was brilliant. This was the first model of the creation of the Universe. The problem is that from there arose a Universe without stars, without galaxies, without life. This means he made a mistake and began to think about what he was missing. And this is what led to our new theory.
Thomas Hertog and Stephen Hawking
Courtesy of Thomas Hertog
“Is there one universe or several?
“Neither of the two ideas is correct. In the hypothesis we have developed, there are many possible universes, but we cannot know whether they actually exist or not. I don’t associate any tangible reality with them. This is where the difference lies.
— Was there time before the emergence of the Universe or did it arise along with it?
“The Big Bang is the beginning of time. If we go back in time, we learn that different forces of physics, types of particles, elements… dissolve, simplify and combine. And ultimately, before the Big Bang, the very concept of time disintegrates and evaporates. Thus we have discovered something that really has no cause.
— Was there nothing before?
“Nothing, nothing special.” Yes, this is something annoying, strange, it contradicts all possible intuition, because we always think in terms of cause-and-effect relationships, one follows from the other.
The laws of physics are not immutable; they changed at the beginning of the universe and can change again.
“Can the laws of physics change or are they unchanged?
“They changed, but only in the first fraction of a second, when the Universe cooled by billions of degrees. Then they crystallized, froze, and have not changed since, as far as we know. The basis of our hypothesis is that even these laws are the result of primary evolution, like the laws of biology. That’s why the book’s title is inspired by Darwin’s Origin of Species.
— Can they change in the future?
-Yeah. Unless they are immutable at a fundamental level, we shouldn’t assume they will last forever. Our Universe is finite. This has happened in the past and will probably happen in the future. But we’re talking about a very, very long time scale: “I don’t think there’s any need to think about an ultimate universe that keeps accelerating forever.
There is no mathematical calculation that led to the emergence of life.
“Is life in the universe the result of chance or design?
“Why our universe is habitable has been Hawking’s big question for many years, because it’s something strange. This is only possible due to very specific laws of physics: specific particles, three spatial dimensions, etc. The answer given by Albert Einstein, Hawking and many others was a mathematical calculation, a transcendental and eternal truth. But this is a very rare answer, nothing like this has ever been found. So Hawking began to doubt himself. Our collaboration was an attempt to breathe life into the equations of physics. And as a result there is no mathematical calculation. This is not a set of universes with many different properties, but rather a Darwinian explanation. Luck, chance, the result of a deeper level of evolution. Everything could have turned out differently.
Gravitational waves will help rewrite the history of space. They’re going to surprise us
“Will the giant Circular Collider, which is planned to be built to replace the LHC, tell us what dark matter and energy are made of?
“Most of the matter in the Universe is what we call dark matter, particles different from the protons, quarks and electrons of ordinary matter, which are also governed by other forces. These particles are in space, they are not on Earth. They are very difficult to produce in particle accelerators. They are too heavy. It is not very clear whether we can generate them on Earth to reveal their properties.
“What will be the fundamental tool for understanding the origin of the Universe?”
“Observation of gravitational waves. They are very weak, they took 13 billion years to reach the Earth, but I think this will be a real revolution. Over the next few decades, they will help us rewrite the history of the Universe. They are going to surprise us.