Discours de remerciement – Berne, 13.11.2015 (vidéo + texte, anglais)

États-Unis/Belgique

Francis Halzen

Prix Balzan 2015 pour physique des astroparticules y compris l’observation des neutrinos et des rayons gamma

Pour les résultats sans égal de ses recherches qui ont conduit à la construction du grand Observatoire de neutrinos IceCube dans les glaces du pôle sud, une réalisation qui a ouvert une nouvelle fenêtre sur l’univers grâce à l’étude cosmologique des neutrinos à haute énergie.

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Federal Councillor,
Ladies and Gentlemen,

It is an immense honor to receive this Balzan Award. I am humbly aware that I receive this Prize thanks to the talent and dedication of the technicians, engineers, scientists and administrators who made the IceCube project a reality.

Matter is made of particles: protons and neutrons, electrons and neutrinos. Neutrinos are the most common, and it is likely that your high school teacher never mentioned them. Neutrinos are never boring; they keep surprising us. This is yet again the case for the first cosmic neutrinos. Rather than originating in nearby supernovae or even our own Galaxy, they originate from sources spread throughout the Universe. The surprisingly large flux observed suggests a common origin with the cosmic accelerators that produce the highest energy photons and cosmic rays. The likelihood is that IceCube science has not run out of surprises yet.

Fred Reines, who discovered the neutrino in 1956, told me that, with the realization that the particle actually existed, literally everybody came up with the idea that one could do astronomy with neutrino beams. Neutrinos, unlike light, go through walls, through the Earth, and this opens the prospect of using neutrinos to look out to the edge of the Universe and peer into the hearts of black holes. In 1960, pioneering articles appeared defining the field of neutrino astronomy. They had some minor flaws, though, in that their estimate of the volume of the neutrino detector required for doing science, 1.5 m on the side, was too low by a factor of 100,000. They also anticipated success within several years, but here we are more than half a century later. Who could have anticipated in 1960 a cubic kilometer neutrino detector made of 100,000-year-old Antarctic ice?

This is exactly what the IceCube project delivered. Our neutrino detector is made of a cubic kilometer of ice, one mile below the geographic South Pole where the National Science Foundation operates a scientific station that made its construction possible. The neutrino detector is the ice itself; we instrumented it with light sensors that map the telltale light patterns made by the occasional neutrino that stops in the ice. It is an eye with neutrino vision that has recently recorded the first baby pictures of the extreme neutrino Universe.

My late IceCube collaborator John Bahcall played a critical role in the discovery of neutrinos emitted by the nuclear reactor in the sun. When he addressed the public, he would tell the audience that there were two things the public did not know, fortunately perhaps, about science.

That scientific discoveries do not flow from a logical straight track is the first secret. Typically, results emerge after following meandering paths, dead ends and plain mistakes. This was certainly the case when we developed the IceCube concept and built the detector. This award is dedicated to the many people who contributed to IceCube by making the critical contributions at its many critical junctures.

The second secret is that we would do science even if we were not paid for it. The same is true even without awards, but I must admit that this one is very much appreciated.