Little Story of Infinity: The new Calculus

Professor Calculus, probably one of the best-known scientists in the world and a great friend of Tintin, makes his first appearance in Red Rackham's Treasure. This inventor and physicist, who later took Tintin to the Moon, was freely inspired by Auguste Piccard, professor at the Free University of Brussels (ULB).

Auguste Piccard, a brilliant physicist who worked in particular during the first Solvay Conferences, Marie Curie, Albert Einstein and all the other pioneers of modern subatomic physics, is recognized as being the first man to go into space attempting a stratospheric flight in 1929, before exploring the abyss aboard a bathyscaphe. A diving record, 10,916 meters below the sea surface, was established in 1960 thanks to his research.

Hergé and Calculus were once again visionaries when they sent Tintin at the bottom of the sea twenty years before…

Let's return to Piccard and his explorations of the extreme. The goal of his research was to study cosmic radiation in the air and at the bottom of the sea in order to better understand our universe.

Nearly a century later, this quest continues and has even intensified for a decade in the abyss. Professor Antoine Kouchner, vice-president for international relations at Université Paris Cité and spokesperson for the ANTARES scientific collaboration, takes us to discover the world of modern Piccard and Calculus.

Antoine Kouchner (AK): ANTARES is the first underwater neutrino “telescope” put into operation in the Mediterranean abyss. It is intended for the observation of the antipodal sky, that is to say that of the hemisphere opposite to that in which it is located, with elementary particles called neutrinos, capable of crossing the Earth. ANTARES is a large research infrastructure since the telescope is made up of twelve “detection lines” 450 m long, anchored at a depth of 2,500 m, and spaced around a hundred meters from each other. Each of the lines includes clusters of photodetectors capable of detecting the light produced as a result of the interaction of neutrinos around the instrument. The detector's power supply and data transmission to land are provided by a main cable of around forty kilometers, connected to a junction box. This is connected to each of the detection lines by cables whose connections are precisely provided by submarines more or less similar to the bathyscaphe. The most similar is the Nautile, the well-known Ifremer submarine, which was notably used to explore the wreck of the Titanic. Other unmanned submarines, unlike Piccard's bathyscaphe and the Nautile, are also used.

One of the specific features of neutrinos is that they are particles that (almost) nothing disturbs. This is an advantage for astronomy: they travel in a straight line, without being deviated by magnetic fields, and can come from the farthest reaches of the Universe. But this elusive character also constitutes an obstacle. Thus, the already substantial size of ANTARES is insufficient: ANTARES is in reality a prototype. But its exploitation was more than satisfactory: ANTARES demonstrated the possibility of instrumenting the ocean floor to open a new window for exploring the Universe, while monitoring the abyss. It also obtained first scientific results, which will be confirmed by its successor, such as the detection of a Galactic signal that indicates the acceleration and propagation of atomic nuclei in the Milky Way. But this is just an example. More than a hundred articles have been published. The scientific exploitation of ANTARES has enabled around a hundred doctoral students in several countries to support their thesis work.

The technological success of ANTARES has pushed the international collaboration that uses the data to design and build new generation instruments. Two distinct scientific goals are now pursued on two different sites. Off the coast of Sicily, Italy, ARCA, the high-energy sensitive branch of KM3NeT, already surpasses ANTARES in terms of volume and will be able to observe galactic and extragalactic neutrinos with unprecedented precision. Ultimately, the detector will include 230 lines 700 m high. Off the coast of Toulon, France, ANTARES makes room for the ORCA detector, a KM3NeT sub-detector sensitive to lower energies and intended for the study of the intrinsic properties of neutrinos, which could be linked to the prevalence in the universe of matter on antimatter. ORCA will be smaller in volume than ANTARES, but denser. In a few years, the Mediterranean abyss will therefore house two complementary neutrino detectors, which seek to answer fundamental questions in physics and establish a link between astrophysics and particle physics.

ANTARES detection cells, like those of its successor KM3NeT, take continuous data and therefore provide non-stop monitoring of environmental conditions. They are sensitive to light in the visible range and in the ultraviolet. They reveal intense activity partly linked to luminescent bio-organisms. At rare moments, the detectors are blinded by flashes of light emitted by the surrounding fauna. We are therefore not very far from what Hergé could have imagined. However, the majority of bioluminescence recorded by our detectors comes from microscopic organisms, such as bacteria, and not from sea “monsters”. If visitors are rare, the acoustic receivers installed on the detection lines – mainly used to know the location of the detectors, which swing slowly with the currents – make it possible to spot whales, dolphins and other cetaceans diving from the surface in search of food. But these passages are only transitory. In fact, the abyssal depths in which our detectors are anchored are more like a sandy desert than an aquatic forest...

Thanks to Professor Kouchner for this expedition to the depths of the seas!