small logo Remembering:

SETI Patriarch Giuseppe Cocconi
courtesy of CERN (European Centre for Nuclear Research)

Giuseppe Cocconi, a central figure in particle physics and cosmic rays, passed away on 9 November, at age 94.

Giuseppe Cocconi passed away on 9 November aged 94. Even thirty years after his official retirement, he would regularly come to CERN to discuss the physics he loved. We were so used to meeting him as he made his way through CERN, that a feeling of loneliness has taken us all.

Born and raised in Como, it was there that Giuseppe first developed his passion for astronomy. As a teenager he used to observe and measure the night sky with the simple tools available to him, and it was this very direct approach that later became his characteristic style of research.

Following the advice of a friend and fellow astronomer, Giuseppe went to study physics at Milan University. Shortly after completing his university studies Giuseppe was invited by Edoardo Amaldi to go to Rome in February 1938 and spend six months at the Institute of Physics. There Giuseppe met Enrico Fermi, Gilberto Bernardini, who was later the first Director of Research at CERN, and others who had just started working in the field of cosmic rays. With Fermi in particular, Giuseppe worked on the construction of a Wilson chamber to study meson decay modes. Giuseppe often recalled how lucky he had been to share the laboratory with Fermi, and enjoyed telling us about him and about Maiorana who mysteriously disappeared while Giuseppe was in Rome. The Wilson chamber was finally completed in Milan.

In August 1938 Giuseppe, back from Rome, laid the foundations for research into cosmic rays in Milan. He worked with Geiger counters and cloud chambers at sea level and at Cervinia and Passo Sella, in the Alps, until 1942, when he was called to join the army to do infrared research work in Rome for the Italian Air Force.

It was in Milan that Giuseppe met Vanna Tongiorgi, a student who chose cosmic rays as the subject for her thesis and Giuseppe was her supervisor. They co-authored a first paper in 1939 on the nature of secondary radiation in cosmic rays. They married in 1945 and formed, for more than fifty years, an extraordinary couple. They both loved physics, fine arts and sports, in particular skiing and walking in the mountains.

In 1942, only five years after getting his Laurea (degree), he was appointed Professor at Catania University, a post which he only managed to take up at the end of 1944, due to the fighting during WW2. Giuseppe always talked with great pleasure of the people he met, and the cosmic ray work at Catania.

His most relevant work during his time in Italy was on extended cosmic ray showers. It was his initial work into this high-energy phenomenon that paved the way for research in this field for years to come.

In 1947 Giuseppe accepted an offer from Hans Bethe for a position at Cornell University. Giuseppe remained at Cornell as a full professor until 1963. Together with Vanna, he performed various cosmic ray experiments at the university, and at Echo Lake in the Rocky Mountains. Two results emerged from this research: his observation of neutrons as one of the cosmic radiation components, with the accompanying phenomenon now known as spallation, and the proof of the existence of extensive showers, some of them of very high energy hinting at galactic, and even extragalactic, origins.

Giuseppe enjoyed his work at Cornell. The exchanges he had with the theoreticians were very friendly and stimulating. He wrote his most widely known paper with Philip Morrison, which was published by Nature in September 1959 (it was written at CERN at a time both were visiting). In this paper they showed that the best frequency to search for signals from intelligent extraterrestrials is 1420 MHz, corresponding to the 21-centimeter line of neutral hydrogen. The Search for Extra-Terrestrial Intelligence (SETI) based on the Cocconi-Morrison paper is still going on today.

During sabbatical leave (1959-61) at CERN, Giuseppe contributed to setting up the experimental programme for the PS, which came into operation in November 1959. He performed a series of measurements on proton-proton elastic and inelastic scattering and proton-nuclei total cross-sections. Back in the USA he continued this programme at the BNL accelerator to measure large angle scattering for two more years.

In 1963 Giuseppe and Vanna joined CERN. He, Alan Wetherell, Bert Diddens and others, formed a group working at the PS on proton-proton scattering. They found that the slope of the diffraction peak shrinks with energy, a phenomenon which was soon interpreted as a manifestation of the exchange of Regge-poles (the so-called pomeron!).

Giuseppe became CERN Director of Research in 1967, and held the position until 1969. At the end of the 60s he was enthusiastic about the perspective promised by the Intersecting Storage Rings, and his group joined forces with a group from Rome to study small angle proton-proton scattering with the technology that later became known as 'Roman pots'. He would hand-build the delicate hodoscopes made of tiny scintillators, and spend hours with PhD students in the ISR tunnel to align them. Thus came the discovery of the rising with energy of the proton-proton cross-section, something which for most people came as a complete surprise, showing that the proton expands with energy, and the correlated discovery that the nuclear-Coulomb interference becomes positive at high energy (as predicted by dispersion relations).

Later Giuseppe and the CERN-Rome collaboration decided to move to neutrino physics. Together with the group led by Klaus Winter, they formed the CERN-Hamburg-Amsterdam-Rome collaboration (CHARM) that built a marble calorimeter and ran the CERN neutrino beam until the beginning of the 80s. Giuseppe became very knowledgeable in the field of neutral and charged current interactions. He was especially interested in the delicate measurement of the elastic scattering of neutrinos on electrons.

After retirement in 1979, Giuseppe maintained an active interest in the experimental work going on at CERN and in the progress of the new accelerators. At same time he followed the progress in the field of cosmic rays and astrophysics. He had a privileged relationship with his theorist friends, and the CERN library recorded him as one of the most demanding users.

Giuseppe enjoyed the respect of great physicists in the world. As a man of culture and vision, he was very curious and attentive to what was going on in the world, and not only in the field of physics. Very kind and always ready to listen, straightforward but humble in his relations with his colleagues, always ready to admire other people's success, he was happy to share his knowledge with juniors. His refusal of association with academies, and his lack of interest in prizes and honours, as well as his wish not to talk publicly, after his retirement, of his scientific life, are well known. He was a great physicist.

We miss his precious friendship. We share our sorrow with his children Anna and Alan and the whole family whom he loved.

Physicist, science fiction author, and IAA SETI Committee member Richard Carrigan adds this personal remembrance:

Cocconi and I shared a field of research in high energy physics, small angle elastic scattering. I remember showing him around the Meson Laboratory at Fermilab when it was still under construction in the early seventies. As I recall Cocconi was concerned to see some small frogs stuck in a new tunnel and wanted to save them. A charming man.

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