Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Nuclear weapons tests are experiments carried out to determine the effectiveness, yield and explosive capability of nuclear weapons. Testing nuclear weapons can yield information about how the weapons work, as well as how the weapons behave under various conditions and how structures behave when subjected to nuclear explosions. Additionally, nuclear testing has often been used as an indicator of scientific and military strength, and many tests have been overtly political in their intention. The most recent nuclear test was announced by North Korea on May 25, 2009. Learn more about nuclear weapons devices, tests and test sites in this book.