Black holes: Jean-Pierre Luminet, emeritus director of research at the CNRS, sheds light on this phenomenon

Just how do you define a black hole? When was their existence first imagined? Is it true that black holes slow down time? What’s going on inside? Could we travel in space using wormholes? Does a black hole threaten the solar system? Is our universe a giant black hole? Jean Pierre Luminet, astrophysicist specializing in black holes at the Medef summer school, informs us.

A fascinating world unfolds. On May 12, 2022, the image of the supermassive black hole Sagittarius A* was delivered in our galaxy, confirming the correctness of Einstein’s theory and further concretizing this phenomenon to the public. In the 1970s, Jean-Pierre Luminet was one of the very first to model the existence of these superstructures with astonishing properties that defy the laws of traditional astronomy.

The book, “Black Holes in 100 Questions”, deals with these bodies so dense that their gravitational field brings everything back to them: light, matter, space and time. Machines for producing energy, these cosmic maelstroms are veritable information traps, even gateways to other universes.

“Black Holes in 100 Questions”, a book by Jean-Pierre Luminet.

An eminent specialist, Jean-Pierre Luminet enlightens us in a very instructive way about this captivating phenomenon and helps us to reflect on the very basis of our conceptions of the nature of the world, the real and the virtual.

You started with a DEA in astrophysics in Montpellier. What sparked your curiosity about the cosmos?

During my studies in pure mathematics at the Saint-Charles Faculty in Marseille, it was reading the book Introduction to Cosmology by Jean Heidmann, which was the real trigger for my scientific vocation. This high-level popularization text dealt with the study of the universe through geometry and general relativity; thanks to him, I understood that the studies of pure mathematics that I pursued as a dabbler provided the appropriate tools to deal with some of the great questions that man asks himself about the cosmos.

The news reveals the first images of black holes. How do you explain the white areas on the disc around the black hole at the heart of our galaxy?

The image is often presented as the image of an accretion disk around the galactic black hole, showing hot spots due to turbulent gas flow. However, this is not so clear and the scientific publications themselves remain discreet on this subject. The reconstruction of a single image from a catalog of hundreds of thousands of images observed and compared to millions of other images previously computed on the computer is a complex process which may have generated “artifacts” that do not really corresponds to hot spots in an accretion disk.

As you expand Roche*s boundaries to the black holes, you arrive at the star pancakes that graze them. Already in 1979, you were the first to show with simulations the asymmetry due to the Doppler effect, confirmed in 2019. Did the artistic vision set in first?

None. It was originally purely geometric reasoning that guided my work, both on the numerical simulations of the black hole in 1978 and on the prediction of stellar pancakes in the 1980s. My Indian ink artworks, certainly from the same period, were completely independent.

Your interest in art is panoramic. Let’s start with the visual sense. Is there a connection between your dating of Van Gogh’s Starry Night and your Escher drawings?

None. The discovery of MC Escher’s engraved work inspired my Indian ink drawings of the 1970s, while my work on the dating of Van Gogh’s Starry Nights began in the 1990s; I completed them recently (a book will be published next year) without any reference to my own graphic works.

Your musical autobiography evokes your piano where Liszt played and your interactions with creators like Gérard Grisey or Hèctor Parra in Barcelona… I recently had the opportunity to play a 19th century piano that Liszt had also played on , but it wasn’t mine , which is a quarter grand from the 1970s! Otherwise, in my musical journey, it is certainly my collaboration with the composers Gérard Grisey around the “music of the pulsars”, and more recently with Hèctor Parra (“Inscape”, psychoacoustic journey in a black hole) that constitute the two most notable.

From 1998 to 2015, you published seven historical novels about the builders of science. Since Ulugh Beg and Samarkand, nothing more… Have you been around?

In fact, in March 2022 I published a collection of nine short stories entitled “Extraordinary and Unusual Stories of Astronomers”. It therefore becomes a total of eight works dedicated to the “builders of heaven”. The subject is inexhaustible, but writing novels requires a lot
time and there are so many other things to do…

In your search for invisible harmony, you interact with mathematicians in topology to renew cosmology, the same with physicists for quantum gravity. Your essays have also made Abbé Lemaître recognized as the father of the Big Bang…

The researcher never fully masters all aspects of his discipline, and collaborations are imperative. For my work on cosmic topology and “curled universes” (classification of possible forms of space), I had to call on the world’s best specialist in the matter, the American mathematician Jeff Weeks. Furthermore, I am passionate about the history of science and ideas, in particular the way the Big Bang models were designed in the 1920s-30s, mainly by Georges Lemaître, to whom I have devoted numerous texts.

From your anthology on Poets of the Universe to Coronelli’s globes at the BNF, your ease in moving between science and art is fascinating. Exploring these sides of the imagination is not encouraged by the division of researchers within their field…

Yes, but I have always functioned like this, going from one register of thought to another at the same time
to rest my mind and cultivate cross fertilization.

In 2021, you refused to accept the Janssen prize when the health passport was imposed on the public. It is quite rare among scientists…

I didn’t turn down the award itself, which is a nice international recognition, but I refused to go to the award ceremony, which actually required the health card, a coercive and counterproductive measure that I strongly oppose. It is true that I was quite alarmed to see how the vast majority of the scientific community complied with this politico-sanitary scam put in place for the sole purpose of total population control, and will likely do so again. If, as I fear, this “pass of shame” will be imposed again this autumn.

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