Japanese physicist who developed the concept of "strangeness" independently of Nobel laureate Murray Gell-Mann. During the 1950s and 1960s, as new subatomic particles were rapidly discovered, physicists faced the daunting challenge of explaining these new particles and their properties in terms of a self-consistent model. The concepts of "charm" and "strangeness" were developed to explain properties of certain quarks. Other types of quarks are known as "up," "down," "top" (or "truth"), and "bottom" (or "beauty").