DANBURY, Conn.—Peter Buck, whose $1,000 investment in a family friend’s Connecticut sandwich shop in 1965 provided the genesis for what is now the world’s largest restaurant chain—Subway—has died. He was 90. Buck, a nuclear physicist who was born in Portland, Maine, in 1930, died at a hospital in Danbury, Connecticut, on Nov. 18, Subway said in a statement. The cause of his death was not disclosed. At 17, family friend Fred DeLuca had asked Buck how he could make some money to help pay for college. Buck’s answer? Open a sandwich shop. In 1965, he and DeLuca opened “Pete’s Super Submarines” in Bridgeport, with the priciest sandwich selling for 69 cents. The duo changed the name to “Subway” three years later and decided to turn it into a chain by franchising—a move that would eventually make both of them billionaires. Forbes estimated Buck’s net worth at $1.7 billion. DeLuca died …