‘Gravity binds everything, from man to planet’

Professor Claudia de Rham is a theoretical physicist at Imperial College London, developing and testing “new models and paradigms” at the intersection of gravity, cosmology and particle physics. She has just published her first book, The Beauty of Fall: A Life in the Pursuit of Gravitydescribing her lifelong quest to understand the “true nature” of the force around her, who saw the train as an astronaut, diver and pilot.

In your book, you say you’ve been “chasing gravity my whole life”. What does that mean?
It’s something we all have within ourselves, this playful relationship with gravity. But to some extent, it took on a meaning of its own for me in terms of really trying to go to outer space, to challenge gravity in a slightly different way. And when that didn’t work out, then to do that from a more scientific point of view, in terms of understanding the basic framework behind our gravity models; come up with new models, and find ways to see if we can try them.

What is it about gravity that is so strong for you?
Gravity is so universal. And I think this is very fundamental, it’s a phenomenon that affects everything, everyone, all the time, everywhere. He does everything completely: he 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 within us without being able to defeat it. It is the feeling of weightlessness, the feeling of freefall is the center of gravity. It is complete freedom in itself.

You’ve trained as a diver and pilot to better understand the fundamental forces around us, and you’ve made it to the final selection stage of astronaut training for the European Space Agency. How did that journey begin?
It started from wanting to chase gravity, somehow. For me, that meant trying to go into outer space and experience gravity inside a different environment, and experiencing this feeling of weightlessness on a deeper level. So when I was able to picture that in my head as a kid, that really became a long-term goal. For such a long period of my life, everything I would do was focused on the idea that I wanted to be an astronaut, that I wanted to participate in the selection of astronauts and put myself in the best position for that.

What was astronaut training?
We were put through a battery of tests, most of which were designed to assess our team-based abilities in stressful situations. This included a pretend rescue trip through the “jungle” – we were asked to plan the dangerous mission knowing that resources were limited, night was coming, and, if we weren’t careful, some might not succeed we have it back. Another saw us pretending to be air traffic controllers at a crowded airport tasked with landing several planes without fuel. The twist was that each of us only had access to half the information, so we had to engage in precise communication and cooperation with our partner to complete the mission. Of nearly 10,000 applicants who applied, 99.5% were rejected by the final stage. Only 42 made it to this second stage of training.

Your hopes were dashed when latent tuberculosis was discovered during the final round of selection, which you describe as “a little souvenir I must have unknowingly brought back with me from my time in Madagascar” from your childhood Do you think what life would be like if you weren’t sick?
I see the candidates going out into space…it’s a dream, of course. But at the same time, I don’t regret the path my life has taken since then. I think it opened up other opportunities.

How much more is there to learn about gravity that we don’t already know?
The beauty of gravity as we know it now is that there is so much more to learn about it. We now know that Einstein’s theory of general relativity stops being a consistent and accurate description of what happens in some cases, like very close to the center of black holes, or the big bang. His theory seems to imply that we could measure some physical quantities, like the curvature of spacetime, which could be infinite (we call this singularity), but it would make no sense to measure an infinite value . To understand what happens when his theory is no longer valid, we might want to ask ourselves questions like “what happens in the center of a black hole?” or “what happened during the big break?” – but if the concepts of space and time no longer make sense, the questions themselves might not make sense either. We don’t even have the language to express the questions we have, much less answer them.

What can gravity tell us about the future?
What we now know is that the expansion of the universe is accelerating, which was a surprise 25 years ago. We need to understand what is causing this accelerated expansion, and whether the laws of gravity we are using to describe them are valid. We need to understand this better to [understand] what will happen in the future. Will this accelerated expansion continue forever? Will it get even faster? Will it stop? We don’t know, because we don’t even know exactly what the origin of this phenomenon is. So the fate of our universe, and the fate of space and time in some sense, will depend on what causes this accelerated expansion of the universe.

Is it frustrating to have so many questions, and so many answers?
It is exciting. It’s small steps. If what you want to do is see if your discoveries will be applied to tomorrow, this is not the field for you. But you learn: you gain a much deeper appreciation of the nature around you, and these small daily steps lead to the biggest steps in the long term. Every little understanding is progress in itself, because it will allow us to go deeper. In science, even a negative result is a result in itself.

• The Beauty of Fall: A Life in the Pursuit of Gravity by Claudia de Rham published by Princeton University Press (£20). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply