Born on 18 January 1911 in Tokyo, Shoichi Sakata was a theoretical physicist whose particle physics model was a precursor to the quark model. Sakata studied at Kyoto Imperial University under Hideki Yukawa, who would go on to win the 1949 Nobel Prize in Physics. (Sakata is at left in the photo, talking to Yukawa.) In 1937 Sakata and Yukawa published a paper that expanded upon Yukawa’s meson theory and predicted (correctly) the existence of the neutral pi meson, or pion. Sakata is best known for the Sakata model, in which the proton, neutron, and lambda particle (and their antimatter partners) are the elementary pieces that compose every hadron. Although Sakata’s model turned out to be wrong, his way of thinking about nature’s fundamental components helped lead to the concept of quarks, which we now know make up protons, neutrons, and other hadrons. Sakata also explored neutrino mixing long before the discovery that the particles oscillate between flavors. He died in 1970 at age 59. (Photo credit: AIP Emilio Segrè Visual Archives)
