In Memoriam Peter K. F. Grieder

Peter Karl Ferdinand Grieder, renowned for his fundamental contributions to high-energy cosmic ray research and neutrino astronomy, died on 14 October 2022 in Bern, at the age of 94. After a rich life dedicated to science, he has been released from cancer. We mourn the loss of a good colleague and dear friend.

Peter was born in Langenthal, Switzerland, on 22 November 1928. After school, he first made an apprenticeship as a radio technician. He then graduated as an electrical engineer at the Burgdorf campus of the Bern University of Applied Sciences and worked in industry in the field of television development for almost two years. In 1953 he went to the USA to further his skills in the domains of electronics and microwaves. In Chicago, he worked for Admiral Corp. where he was involved in colour television research. At the same time, he was registered as a student at the Graduate School of the Illinois Institute of Technology (IIT), with the aim to obtain a Master’s Degree in electronics. However, at this point his interests shifted more and more towards physics. In 1957, he obtained his MS degree in Physics from the IIT. For his thesis, he did research with the Argonne group of the U.S. Atomic Energy Commission at the University of Chicago. There he came also in contact for the first time with cosmic ray physics, taking part in seminars of Professors Simpson, Schein and Chandrasekhar. However, he had to abandon a continuation of his career in Chicago because he as a Green Card holder was facing problems with the U.S. military. He returned to Switzerland in 1959.

In 1961 Peter got his PhD from the University of Bern, where he did research under Prof. F. G. Houtermans in high-energy cosmic ray physics. He then worked successively as a postdoctoral scientist at the Niels Bohr Institute in Copenhagen with Prof. B. Peters on quark hunt experiments, at CERN in Geneva in the experimental and later on in the theoretical physics division with Drs. R. Hagedorn and M. Jacob on models of high energy hadronic interactions and multiparticle production, in conjunction with air showers, and he was a visiting professor at the Institute for Nuclear Studies of the University of Tokyo. In 1971, he habilitated, and in 1978, he was appointed Professor of Physics at the University of Bern. He was a guest professor for many years at the University of Hawaii. He also served the national and international science community, e.g. by organizing conferences, and he acted as secretary of the Swiss Physical Society from 1985 to 1987. Since 1994 he was Prof. emeritus, but continued scientific activity in High Energy Cosmic Ray Research and Neutrino Astronomy at the Physics Institute of the University of Bern.

Peter’s work was always at the forefront of the field. He was among the first to introduce the computer simulation technique into the study of air showers. He developed the ASICO air shower simulation program system which later became the foundation of the widely used Karlsruhe Extensive Air Shower Simulation Code CORSIKA. Later, together with Prof. J. G. Learned from the University of Hawaii, USA, and with Prof. F. Reines, Nobel Laureate, as well as with colleagues from other institutions, he was co-initiator of the pioneering DUMAND neutrino telescope project in Hawaii. This project for the search of high energy neutrinos from active galactic nuclei opened a new window in astrophysics and was the template for all presently existing and planned giant neutrino telescopes, like e.g. IceCube in Antarctica.

Peter was a hardworking, multi-skilled, and open-minded person. His enthusiastic nature and never flagging work energy, his phenomenal memory and his global network of relationships were as impressive as his striving for perfectionism. He loved exchanging ideas with colleagues, be it as an interested listener at lectures at the University or as an active participant of conferences. His long-term collection of proceedings brought back from the International Cosmic Ray Conferences ICRC is probably the most comprehensive individual one worldwide. Thanks to his outstanding experimental and theoretical work, Peter has gained worldwide recognition and respect, as documented e.g. by the honorable mention by Prof. S. K. Gupta, the then Chairman of the IUPAP C4 Commission, during the closing session of the 2021 ICRC. Besides his intense scientific work, he, together with his wife Estelle, maintained an active social life. Both loved traveling, and the regular skiing holidays in Zermatt were an integral part of their annual program.

Peter has written remarkable books on cosmic ray physics, which transmit the enthusiasm he had for this amazing field where experiments are adventures in the most amazing places in the world. His interest was initiated by the DUMAND enterprise, the installation of the first string of photosensors in the deep sea of Big Island in Hawaii waters. His latest enterprise captures the fascinating field of multi-messenger astronomy, where new messengers enter into play to reinforce the impact of photon astronomy. He pedagogically leads the reader into the wonder of neutrino astrophysics and gravitational waves from their concepts to their amazing results. The book is in completion by Prof. Teresa Montaruli who witnessed the last year of efforts on this by Peter, leading to any sort of fight against the decease that took him away from his beloved and deep passion for scientific culture.

Peter is survived by his wife Estelle, his daughter Marina and his son Ralph and their families with two and three grandchildren respectively. Our deepest sympathy and sincere condolences go to all of them.

Erwin O. Flückiger and Teresa Montaruli

(using many of Peter’s own words: www.space.unibe.ch/about_us/personen/prof_em_dr_grieder_peter/index_eng.html)

[Released: February 2023]