Clyde Wiegand (May 23, 1915 – July 5, 1996) was an Americanphysicist. He was best known for the co-discovery of the antiproton in 1955, along with Owen Chamberlain, Emilio Segre, and Thomas Ypsilantis. May 23 is the 143rd day of the year in the Gregorian calendar (144th in leap years). ... 1915 (MCMXV) was a common year starting on Friday (see link for calendar). ... July 5 is the 186th day of the year (187th in leap years) in the Gregorian Calendar, with 179 days remaining. ... 1996 (MCMXCVI) is a leap year starting on Monday of the Gregorian calendar, and was designated the International Year for the Eradication of Poverty. ... Since antiquity, people have tried to understand the behavior of matter: why unsupported objects drop to the ground, why different materials have different properties, and so forth. ... The antiproton(aka pbar) is the antiparticle of the proton. ... 1955 (MCMLV) was a common year starting on Saturday of the Gregorian calendar. ... Owen Chamberlain (b. ... Emilio Gino Segr (February 1, 1905 - April 22, 1989) was an Italian American physicist who, with Owen Chamberlain, won the 1959 Nobel Prize in Physics for their discovery of the antiproton. ...