Columbia with proton, heavy hydrogen, and helium beams, they were able to perform their notable experiment. The beta ray spectra were measured in the magnetometer spectroscopy fifty feet from the accelerator. The beta decay sources B-12 and N-12 were produced in the magnetometer. The laboratories were locked during midnight and Mo had to create a duplicate key for everyone to sneak in and out of the laboratory during the wee hours of the morning. Mo would escort Wu to her Manhattan apartment home. Wu's discovery was presented at the Hilton hotel on January 26, 1963. Wu was pleased with the achievement and mentioned that it gave a complete foundation for Fermi's theory of beta decay as well as provide support for the theory of the two-component neutrino, which her parity experiment first established. Feynman was very happy with the announcement and was so proud of the outcome that he called the CVC theory, together with his diagram and work in quantum electrodynamics, one of his finest scientific accomplishments. Later in the 1960s, Wu conducted more experiments on beta decay, specifically on double beta decay. She went inside a 2,000 ft deep salt mine below Lake Erie in Ohio to investigate on muonic atoms in which muons take the place of electrons in normal atoms. The work conducted here would pave the way for its future discovery in the 1980s. Wu later wrote a textbook with Steven Moszkowski entitled Beta Decay, which was published in 1966. It was the first comprehensive study on beta decay, and the book quickly became the standard reference on the subject; it remains one of the standard references in the 21st century. Later years and social advocacy Wu's older brother died in 1958. Her father died the next year, and her mother would follow him in 1962. The United States State Department had imposed severe restrictions on travel to Communist countries by its citizens, so Wu was not permitted to visit mainland China to attend their funerals. She saw her uncle, Wu Zhou-Zhi, and younger brother, Wu Chien-Hao, on a trip to Hong Kong in 1965. After the 1972 Nixon visit to China, relations between the two countries improved, and she visited China again in 1973. Wu nearly visited in 1956, but decided to stay in the US to finish her famous experiment while her husband visited China. By the time she returned, her uncle and