Two centenaries: The discovery of cosmic rays and the birth of Lajos Janossy

Centenaries provide useful perspectives for looking back upon long-past events and on their later consequences, and also on the activities of persons who made a lasting impact on some important field of research. Cosmic ray physics, as we now know it, had multiple roots. The most important puzzle that incited research in the early 20th century, however, was connected with the lack of understanding of the origin of an omnipresent extremely penetrating ionizing radiation. At least in hindsight, the balloon ascent of Victor Hess on the 7th August 1912 provided the first convincing evidence for the cosmic origin of that radiation, although Werner Kolhorster's subsequent flights to even higher altitudes and with better instrumentation certainly provided important confirmation. General acceptance of the existence of that radiation came more than a decade later, and its basic properties were revealed only in the early 30's. It was at about that time that a research student of Kolhorster, Lajos Janossy, who happened to be borne in the discovery year of 1912, started his research in cosmic ray physics. Later he did important research in London, Manchester and Dublin, and wrote one of the first comprehensive monographs on cosmic rays. After his return to Hungary in 1950, he played an important part in establishing cosmic ray research in a newly formed research institute in Budapest.