claim: Gun powder was discovered during the Qin dynasty.
evidence: Roger Rosenblatt -LRB- born 1940 -RRB- is an American writer .. He was a long-time essayist for Time magazine and PBS NewsHour .. Time. TIME magazine. PBS NewsHour. PBS NewsHour. He writes books , and is the Distinguished Professor of English and Writing at Stony Brook University .. Stony Brook University. Stony Brook University