Prof. Claudia de Rham is a theoretical physicist at Imperial College London and develops and tests 'new models and paradigms' at the intersection of gravity, cosmology and particle physics. She has just published her first book, The beauty of falling: a life in pursuit of gravity charting her lifelong attempt to understand the 'true nature' of the force around her, which trained her to be an astronaut, diver and pilot.
In your book you say that you have been "chasing gravity all my life." What does that mean?
It's something we all have within ourselves, this playful relationship with gravity. But to some extent it has taken on its own meaning for me in terms of really trying to go to space, to challenge gravity in a slightly different way. And if that hasn't been done, then we need to do that from a more scientific perspective, in terms of understanding the underlying framework behind the models that we have for gravity; coming up with new models and finding ways to see if we can experiment with them.
What do you find so compelling about gravity?
Gravity is so universal. And I think this is very fundamental, it is a phenomenon that affects everything, everyone, always and everywhere. It really does everything: it connects everything and everyone. We all experience it the same way, whether we are a person or a planet, a black hole or a balloon, a hammer, a feather, a piece of cheese or a pumpkin seed. It is something that is within us that we cannot defeat. The feeling of weightlessness, the feeling of free fall is what gravity is. It is a complete freedom in itself.
You trained as a diver and pilot to better understand the fundamental forces around us, and advanced to the final selection stage of astronaut training for the European Space Agency. How did that journey begin?
In a sense, it started from wanting to chase gravity. For me, that meant trying to go into space and experience gravity in a different environment, and experience this feeling of weightlessness on a deeper level. So once I was able to formulate that in my head as a kid, that really became a long-term goal. For such a long period of my life, everything I did was focused on the idea that I wanted to become an astronaut, I wanted to participate in the selection of astronauts and put myself in the best position for that.
The fate of our universe will depend on what is driving the accelerated expansion of the universe
What did astronaut training entail?
We were subjected to a series of tests, most of which were designed to assess our team skills in stressful situations. This included a so-called rescue expedition through the "jungle" - we were asked to plan the risky mission knowing that resources were limited, night was approaching, and if we weren't careful, some of us might not make it back. Another saw us working together as would-be air traffic controllers at a crowded airport, tasked with landing several planes short on fuel. What was special was that each of us only had access to half the information, so we had to communicate and work closely with our partner to complete the mission. Of the almost 10,000 applicants, 99.5% were rejected in the final phase. Only 42 reached this second phase of training.
Your hopes were dashed by the discovery of latent tuberculosis during the last round of selection, which you describe as "a little souvenir that I unknowingly brought back from my time in Madagascar" from your childhood. Do you wonder what life would have been like if you hadn't gotten sick?
I see the candidates going into space... it is of course a dream. But at the same time, I have no regrets about the path my life has taken since then. I think it has opened up other opportunities.
How much more is there to learn about gravity that we don't already know?
The great thing about gravity as we know it now is that there is still a lot more to learn about it. We now know that Einstein's theory of general relativity is no longer a consistent and accurate description of what happens in some situations, such as very close to the centers of black holes or the Big Bang. His theory seems to suggest that we could measure certain physical quantities, such as the curvature of spacetime, which appear to go to infinity (we call this singularity), but measuring an infinite value would simply make no sense. To understand what happens when his theory is no longer valid, we might want to ask ourselves questions like "what exactly happens at the center of a black hole?" or "what happened at the time of the Big Bang?" - but if the notions of space and time no longer make sense, then the questions themselves may no longer make sense either. We don't even have the language to formulate, let alone answer, the questions we have.
What can gravity tell us about the future?
What we currently know is that the expansion of the universe is accelerating, which was a surprise 25 years ago. What we need to understand is what is causing this accelerated expansion, and whether the laws of gravity we use to describe it are valid. We need to understand this better [understand] what will happen in the future. Will this accelerated expansion continue forever? Will it go any faster? Will it stop? We don't know, because we don't even know exactly what the origin of this phenomenon is. The fate of our universe, and in a sense the fate of space and time, will therefore depend on what is driving this accelerated expansion of the universe.
Is it frustrating to have so many questions and so few answers?
It is exciting. They are small steps. If you are trying to see if there will be an application of your discoveries tomorrow, then this is not the field for you. But you do learn: you gain a much deeper appreciation for the nature around you, and it is these everyday small steps that really lead to the biggest steps in the longer term. Every little understanding is in itself a breakthrough because it allows us to go deeper. In science, even a negative result is a result in itself.
