“There is a bug when the laws of physics that we know today no longer apply.”

Let’s leave the word “original” for the moment, and let’s start from the bug. If by bug we mean something that should happen in a certain way and that starts to work differently, I’m not completely sure.

The Big Bang is both a reference to a moment and a story, that of the evolution of the universe – much denser and hotter in the beginning. Where there is a bug is when the universe is so dense and hot that the laws of physics that we currently know no longer apply. They become insufficient. The Big Bang is also referring to this moment that scientists are unable to explain. Cosmology, thanks to the laws of physics, describes how one goes from one state to the other but does not speak of the original moment.

Why are we on Earth? Where do we want to orient our lives? We can each have our answers to these existential questions. What moves me is to understand. I find it tremendous that humanity is at a stage where individuals are able to address these issues, and to help increase knowledge.

When one advances knowledge, one realises that the knowledge acquired for intellectual reasons have practical applications. Take quantum mechanics for example. Thanks to it, we developed laser. We discovered general relativity and bam, GPS arrived. But the core motivation is to understand…

It is actually quite uncorrelated because the scale of cosmology is very large and disconnected from the scale of the problems that we have today on our planet. The story of the creation of our planet does not intervene with the way the universe as a whole evolves. The Earth was formed with debris gravitating around the Sun a few billion years ago, through the laws of classical physics. Cosmology, on the other hand, is completely independent of the creation of the Earth, the formation of life and what is happening today in the atmosphere.

You are wrong. Paradoxically, astrophysics and cosmology are areas to which people are happy to turn. They are fascinated, really. On the other hand, if they allow themselves to go into the detail a little, they are likely to be disappointed. What you will learn is not very interesting. If I tell you that the nearest galaxy is not millions of light years away, but billions, you won’t be bothered as much. We speak of scales of time and space so vast that cosmology is disconnected from the current problems of our planet.

On the other hand, to know that the universe has a history, that at the beginning it was only gas before starting to form stars and then planets, it is already more interesting. On the place of Man in the universe, which in my opinion is the most captivating theme for the general public, cosmology does not provide answers. This is not its job. It must be understood that in order to cultivate a passion for astrophysics, astronomy and cosmology, one must first have a passion for physics and mathematics.

There is a bug because people do not realise what science is. It aims to find the laws that govern the evolution of nature. It is fabulous! Thanks to an equation, we know how long it takes an apple to land on the ground. The world in which one lives is governed by mathematical laws and formulas. It’s incredible. But because it is based on maths, which are boring, this fascination is not very present in the general public. It’s a shame.

The rejection of complexity and difficulty is one of them. It would be necessary to be able to explain everything in two minutes, like an elevator pitch, without taking the time not to understand first. Science is a puzzle on a human scale. Not understanding can be disheartening but the feeling of evolving towards understanding is extraordinary. It’s enjoyable.

Take the example of relativity. The fact that time depends on the observer is a complicated notion that can prevent understanding in some people. Yet the mathematics behind this theory is at college level. I would like to give people the taste of the difficult to take them much, much further. Esotericism is the opposite of science, to which it is often applied, because it uses a complicated language to hide and conceal closed knowledge belonging to only a few people. Science is open, researchers are happy when their results are published. What is esoteric is their very technical language.

The bug is the life of science. If science lives, it is because people disagree and are forced to defend their point of view and argue it. Some controversies can be resolved several years after surfacing. But what is certain is that they are vital.

They all put a grain of sand in the system. The concept of bug also covers for me the real bugs that are the inconsistencies. Theories are developed by applying logic, making experimental predictions, and leading to conclusions that are not compatible or even contradictory. This is called paradoxes. They help evolve sciences greatly because they indicate that the starting theory is invalid.

Absolutely. Because once it is resolved, we really come to understand something.

It’s a complete mix of genres. Is there a scientific proof of God or can one contradict the existence of God from a scientific point of view? I would answer you: can we do it using musical science? You would say that it has nothing to do and you would be right. Science is not for talking about God. The methods, the goals, the objects are different. The Big Bang is a subject for which the mixture of genres is tempting because it speaks of the beginning of the universe, therefore of creation. But cosmology can only explain how one state moves to another.

Yes, science has that role to play. An example: by reading some religious texts, one could think a few hundred years ago that the Earth was 4000 years old. Science has been able to say that it is actually 4.5 billion years old. It is an irrefutable fact in the face of a religious belief.

For people, this object that cannot be understood or explained is typically mysterious. They see the black hole as our limits to us astrophysicists, because it defies us. Yet its properties of general relativity are very well understood, it is not a mystery at all. We have long been able to detect these black holes indirectly. We know that there is one in the centre of our galaxy. The famous photo published on Twitter recently and relayed worldwide lift the veil. I see it during my lectures, it’s really a subject that pique people’s interest.

What I find damaging is that the press often presents things from what we do not understand. What makes me dream in astrophysics is everything we already understand. We understand how the Sun, the stars, the planets are formed.There is a dreamy aspect which is sacrificed at the price of a certain sensationalism of the holding the scientists in check by a so-called mystery.

Certainly. “Interstellar” is one of the few works in which physics is at the heart of the film and makes it possible to ask questions. Christopher Nolan did a splendid job on the subject; we feel that he himself asked questions. It is a beautiful journey towards understanding the temporal shift of relativity.

“Interstellar” is the first, “2001, the Odyssey of Space” comes in second for Kubrick’s concern for realism, because he did not cheat with the laws of physics; and “Planet of the Apes” as number 3 for two reasons: the film begins with time shift and relativity, and it is a beautiful nod to the scientific process and history of science. The whole process of humans in front of monkeys is typically Galileo.

A bug is what I fight against every day in my research because astrophysics is a lot of programming and code development. A bug is something that does not work as expected, and for a profound reason. Quantum mechanics, the theory of relativity are all mechanisms that work wonderfully well but are not compatible. So, there remains this bug to solve.

That would be dark matter, which I work on a daily basis. The question we ask ourselves is this: when we observe the universe, we detect the presence of a lot of mass and this in an important relationship: there is ten times more invisible matter than visible matter. This is called dark matter. We learn that the universe is actually very heavy. With telescopes we try to look at this mass but we do not see anything. We have been trying to understand since the 1930s. Experimental evidence is growing but we cannot see anything. This opens up possibilities for particle astrophysics because it could be microscopic particles. But that remains a bug today.