Does the universe play music? Is the cosmos an orchestra where each particle plays its own score? Or would there be only one string, vibrating like a violin? This vision of a harmonic universe, which, like the orchestra before the curtain, offers us a marvellous cacophony, is the one Jean-Philippe Uzan proposes in his latest book The Secret Harmony of the Universe. A stroll between astrophysics, astronomy, history, mathematics and music. When art and science come together for the best.
Jean-Philippe Uzan is an astrophysicist at the Paris Institute of Astrophysics. But he is also a musician. His passion is to set to music, in the company of composers, the movements of the universe. His latest book is a walk through the history of science and this millennial quest for world harmony.
Do the sounds of the cosmos exist? One of the first to ask this question was Pythagoras. Legend has it that in the 6th century B.C.E., while walking through the blacksmith's district on his island of Samos, he observed the diversity of sounds produced by hammers and anvils. The sounds varied according to the size and shape of the instruments. Back home, Pythagoras set out to carefully observe the taut string of a lute. He discovered that by plucking the string two-thirds and three-quarters of the way, harmonious chords could be achieved. In the middle of the string was the octave, which at the time was called the tuning fork. As Arthur Koestler sums up, "The octave was the octave of the string. Pythagoras transforms noise into information ». The links discovered by the famous Greek mathematician between musical harmony and numbers will lead him to unexpected horizons.
The song of the stars
If music links the world of mathematics and the physical world, wouldn't it also have a link with the cosmos? Legend has it that Pythagoras had the idea of using this word to designate the celestial vault. Jean-Philippe Uzan reminds us that cosmos in Greek means finery, the jewels that women wore. The verb kosmein is translated as both "to put in order" and "to adorn, to adorn". The beauty of the organized sky; a harmony.
Searching for the song of the stars and the celestial spheres had an embarrassing problem with the Ancients: no one had ever heard the music of the stars! They did not yet know that air was necessary for the propagation of sound and that space was empty. They explained that we could not hear the music of the cosmos because we did not have the physical ability to hear it. We wouldn't have the sense to hear this music of another nature.
This argument is almost the same as the one that could be used about gravitational waves that the theory suspected existed but that until last year we had never been able to experience. Unlike light - associated with sight - or sound - associated with hearing - these waves are of a new nature and do not correspond to any of our human senses. A sixth sense, " an extraterrestrial sense "? wonders Jean-Philippe Uzan.
Quantum mechanics, which developed at the beginning of the 20th century, will bring a new dimension to the understanding of the universe and answer this haunting question: does the universe sing? This discovery has counter-intuitively turned our view of the world upside down. It establishes that the distinction between wave and matter is illusory. Every particle is at the same time a wave and matter. Thus all matter is vibrating. Every atom has its own "musical" signature. « We can thus see each atom as a musical instrument... " writes Jean-Philippe Uzan.
From the smallest particle to the largest star, there is vibration. Our sun, as we now know, is a drum. Every five seconds, it emits a characteristic vibration. But the smallest quark also emits its note in the cosmic score. And the music was.
In the beginning was the big bang. Already a sound. Between the first fraction of a second - below which we still remain, according to Planck's theory, in an unfathomable mystery - up to 300,000 years, the universe began to expand. Its density was extreme and the matter was terribly hot. Light was so dense that photons were tearing electrons out of the atoms. We then had a plasma in which pressure waves could propagate. If there is an overdensity of matter, gravitation theory says there will be a collapse. The pressure will increase, the density will increase, and the photons will bounce back. Then we'll have oscillations between radiation pressure and gravitational collapse. Vibrations will begin to pass through this cosmic plasma. It will last from the big bang until 300,000 years later.
The cosmological diffuse background, discovered in 1965, is the most direct witness of the Big Bang.
Since then, its fluctuations have been studied by the space probes COBE (1992), WMAP (2003) and Planck (2009). Source wikipedia
Today we know how to observe the moment when matter is going to recombine and release the light that will propagate freely in space from then on, interacting very weakly with matter. Today we can see and photograph these light signals coming from the origin of the world. Astrophysicists say that the universe becomes "transparent" whereas before it was opaque, since light could not propagate freely. It is from that moment, says Jean-Philippe Uzan, that the universe vibrated like a drum. Acoustic waves, pressure waves, i.e. sound, then propagated.
Jean-Philippe Uzan is a specialist of Superstring theory. This theory states that there are not a thousand and one kinds of elementary particles, but only one. This fundamental particle would be a vibrating string, like that of a violin, whose harmonics, i.e. the different modes of vibration, would constitute all the particles, known or unknown. The physicist Etienne Klein, in an interview with Jean-Philippe Uzan broadcast by France-Culture explains: " at such and such a frequency of this string would correspond to an electron, to such and such a neutrino, to such and such a quark, etc... Thus, the bottom of the matter, the dust of the world if one prefers, would vibrate, like a pleasant cacophony rising from the pit before the curtain rises, a great incomprehensible and beautiful work, played by a phantom and infinite philharmonic. "
This superstring theory would explain the intuitions that men have had since they first looked at the sky: the stars sing, the cosmos is a musical harmony. A small detail in the form - perhaps - of coincidence: Superstring theory has for anagram Orchestra dust.