Nuclear fission is the splitting of a heavy atomic nucleus is split into two lighter nuclei, producing energy in the process.
Nuclear fission in Human historyEdit
Humans first achieved nuclear fission in 1945, and it was soon after applied to weaponry. When Quark, Rom, Nog and Odo were accidentally transported to Earth in the year 1947, they were surprised to learn Humans triggered fission reactions in the open atmosphere, although this turned out to be to their advantage. (DS9 episode: "Little Green Men")
Nuclear fission was also applied to power generation, particularly to military vessels. The United States Navy's aircraft carrier USS Enterprise was one of the first nuclear vessels. (TOS movie: Star Trek IV: The Voyage Home)