He navigates between two infinities, Gianfranco Bertoneand has not lost its sense of wonder: from the infinitely small governed by quantum physics to the infinitely large, ordered by gravity elaborated more than a century ago by Albert Einstein.
Two theories which are not compatible at tiny scales, but seem to meet near fascinating portals, black holes, “theoretical laboratories”, to use the expression of the professor of theoretical physics of astroparticules at the University of Amsterdam, who is also the founding director of theEuCAPTthe European Consortium for Astroparticle Theory.
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Humanity sees a black hole for the first time in history
“Between two infinities“, this is the title of his book with the subtitle “Gravitational waves and the quantum origin of the greatest mysteries of the Universe”.
Visualization of cosmic filaments using the Illustris simulation program. Here, dark matter (in blue) and gas (in orange) are distributed in a giant galactic cluster that spans about 300 million light-years. [ESO – www.illustris-project.org]
These puzzles are dark matter and energy, black holes and the Big Bang. The scene is set: the journey will be as in Hell of Dante. Passing from one sphere to another, from hell to paradise, he paints a portrait of current knowledge and visits scientists of the past to better shed light on what astrophysics has in store for us today.
“The great discoveries of modern astronomy have opened our horizons to an unexpected cosmos, containing mysterious forms of matter and energy, known as dark matter and dark energy, and to places and events in the Universe or the laws of physics are collapsing”, he explains at the microphone of La Matinale.
“There remains a cloud surrounded by mysteries and uncertainties that seem to have something in common: all of them come from the observation of the Universe at the largest scales, but seem to sink their roots in a microcosm governed not by gravity. but by quantum physics, that of subatomic particles. This is where we are currently looking for answers to these great mysteries of the Universe”.
>> Watch Gianfranco Bertone’s lecture at EPFL on April 3, 2023, “Between Two Infinities: Uncovering the Greatest Mysteries of the Universe”:
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new messengers
In his book, Gianfranco Bertone recounts the birth of a new astronomy called astronomie multimessager: “A new revolution in our understanding of the Universe”, underlines this native of Calabria.
The electromagnetic wavelengths of light visible to human eyes: what we call “colors”. [Capture d’écran – Gianfranco Bertone]
Messages that contain something to build a bridge between the infinitely large and the infinitely small, according to his research. As if we had new “sensory organs” to apprehend the Universe.
In fact, in addition to the observation of light – in its entire spectrum of electromagnetic waves – from celestial objects, there are now gravitational waves, neutrinos or cosmic rays: messengers that carry information from regions otherwise inaccessible. They will have to be decoded.
And this is what the scientific community is striving to do with, in particular, the very promising gravitational waves, detected directly for the first time in history on September 14, 2015.
On September 14, 2015, the first detection in history of gravitational waves from the collision of two black holes, with “cosmic chirps”: an energy equivalent to three solar masses was emitted in a few tenths of a second. [Johan Jarnestad/The Royal Swedish Academy of Sciences – nobelprize.org]
Amusing anecdote about these waves: in 1936, Albert Einstein – who nevertheless theorized them in 1917 – believed he had proven that they did not exist, then changed his mind… It was ultimately their detection that in 2017 was worth the prize Nobel Prize in Physics to Rainer Weiss, Barry Barish and Kip Thorne.
An immense field of exploration opens up. Gravitational waves can therefore be coupled with classical astronomical observations – the multimessagers –, as was the case during the first coalescence of two neutron stars on August 17, 2017: combined data that teaches astronomers much more.
>> A report from October 2017 on this event named GW170817, with explanations by Carlo Ferrigno and Stéphane Paltani:
“Gravitational waves are vibrations in space-time”, recalls the astrophysicist: “Einstein taught us this more than a hundred years ago. He also taught us that gravity is a manifestation of curvature of spacetime. And now we know that – just as the ground can be shaken by ruptures in rocks and create an earthquake – spacetime can be shaken by events like the merger of two holes black”.
Understand our origins
The afterglow of the Big Bang, the Cosmic Microwave Background (CMB), detected by ESA’s Planck space probe. This radiation was printed in the sky when the Universe was 370,000 years old. It shows tiny temperature fluctuations that correspond to regions of slightly different densities, representing the seeds of all future structure: the stars and galaxies of today. [Planck Collaboration via NASA – AP Photo/ESA]
These new messengers manage to bring us information that comes from the moments after the Big Bang, when the Universe was a newborn: “There were no stars, no planets: there were only almost homogeneous distributions of matter and energy. And we see very small fluctuations on the cosmic microwave background”, this fossil light of the Big Bang.
“If we manage to understand the origin of these fluctuations, we will really have given an answer to the question of origins. That is the ultimate frontier, as well as the connection with particle physics”.
The physicist also mentions that the most used and best known hypothesis describing the beginnings of the Universe is an energy field: “Originally, there was this quantum field which is responsible for the accelerated expansion of the Universe at the time of the Big Bang; it is its disintegration which is responsible for the fluctuations observed in the cosmic microwave background”.
But there is still a lot to learn. And one sentence seems to sum up Gianfranco Bertone’s book well. He writes: “The realization of our ignorance is one of the most important results of physics and astronomy of the last fifty years”.
>> Astrophysicist Gianfranco Bertone participated in a “Lunch en Philo” organized by EPFL on April 3 with the theme “Will there always be limits to knowledge?”:
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Interview radio: David Berger
Web article: Stephanie Jaquet