Takaaki Kajita

On this day in 1959, physicist Takaaki Kajita was born in Higashimatsuyama, Japan. In 1986 he joined the Kamiokande experiment, which uses a huge tank of water in a mine near Hida, Japan, to detect speedy, elusive particles called neutrinos. The following year the experiment detected neutrinos streaming from Supernova 1987A, marking the first measurement of neutrinos from a specific object other than the Sun. By the mid-1990s Kajita was leading neutrino studies at the upgraded Super-Kamiokande facility. In 1998, his team demonstrated that neutrinos can morph from one type (the particles come in three types, or “flavors”) into another. The discovery proves that neutrinos have mass, although it’s very small. Kajita’s achievement earned him the 2015 Nobel Prize in Physics, which he shared with Arthur McDonald. Read Physics Today’s Nobel coverage from October to learn more about Kajita and the changing flavors of neutrinos. (Photo credit: Bengt Nyman, CC BY-SA 4.0)

Date in History: 9 March 1959