| Nuclear testing is experimentation with | | | | the ground to draw dirt and debris into their |
| nuclear weapons. Throughout the twentieth | | | | mushroom cloud can generate large amounts of |
| century, most nations that have developed | | | | nuclear fallout due to irradiation of the |
| nuclear weapons have staged tests of them. | | | | debris. High-altitude nuclear tests can |
| Testing nuclear weapons can yield information | | | | generate an electromagnetic pulse, and |
| about how the weapons work, as well as how | | | | charged particles resulting from the blast |
| the weapons behave under various conditions | | | | can cross hemispheres to create an auroral |
| and how structures behave when subjected to | | | | display. |
| nuclear explosions. Additionally, nuclear | | | | |
| testing has often been used as an indicator | | | | Underwater testing results from nuclear |
| of scientific and military strength, and many | | | | devices being detonated underwater, usually |
| tests have been overtly political in their | | | | moored to a ship or a barge (which is |
| intention; most nuclear weapons states | | | | subsequently destroyed by the explosion). |
| publicly declared their nuclear status by | | | | Tests of this nature have usually been |
| means of a nuclear test. | | | | conducted to evaluate the effects of nuclear |
| | | | weapons against naval vessels (such as in |
| The first atomic test was detonated by the | | | | Operation Crossroads), or to evaluate |
| United States at the Trinity site on July 16, | | | | potential sea-based nuclear weapons (such as |
| 1945, with a yield approximately equivalent | | | | nuclear torpedoes or depth-charges). |
| to 20 kilotons. The first hydrogen bomb, | | | | Underwater tests close to the surface can |
| codenamed "Mike", was tested at the Enewetak | | | | disperse large amounts of radioactive water |
| atoll in the Marshall Islands on November 1, | | | | and steam, contaminating nearby ships or |
| 1952, also by the United States. The largest | | | | structures. |
| nuclear weapon ever tested was the "Tsar | | | | |
| Bomba" of the Soviet Union at Novaya Zemlya | | | | Underground testing refers to nuclear tests |
| on October 30, 1961, with an estimated yield | | | | which are conducted under the surface of the |
| of around 50 megatons. | | | | earth, at varying depths. Underground nuclear |
| | | | testing made up the majority of nuclear tests |
| In 1963, all nuclear and many non-nuclear | | | | by the United States and the Soviet Union |
| states signed the Limited Test Ban Treaty, | | | | during the Cold War, on account of other |
| pledging to refrain from testing nuclear | | | | forms of nuclear testing being banned by the |
| weapons in the atmosphere, underwater, or in | | | | Limited Test Ban Treaty in 1963. When the |
| outer space. The treaty permitted underground | | | | explosion is fully contained, underground |
| tests. France continued atmospheric testing | | | | nuclear testing emits a negligible amount of |
| until 1974, while China continued up until | | | | fallout. However, underground nuclear tests |
| 1980. The last underground test by the United | | | | can "vent" to the surface, producing |
| States was in 1992, the Soviet Union in 1990, | | | | considerable amounts of radioactive debris as |
| the United Kingdom in 1991, and both France | | | | a consequence. Underground testing can result |
| and China continued testing up until 1996. | | | | in seismic activity depending on the yield of |
| After adopting the Comprehensive Test Ban | | | | the nuclear device, and generally result in |
| Treaty in 1996, all of these states have | | | | the creation of subsidence craters. In 1976, |
| pledged to discontinue all nuclear testing. | | | | the United States and the USSR agreed to |
| Non-signatories India and Pakistan both last | | | | limit the maximum yield of underground tests |
| tested nuclear weapons in 1998. | | | | to 150 kt with the Threshold Test Ban Treaty. |
| | | | |
| The most recent nuclear test was announced by | | | | Separately from these designations, nuclear |
| North Korea on October 9, 2006. See 2006 | | | | tests are also often categorized by the |
| North Korean nuclear test for more | | | | purpose of the test itself. Tests which are |
| information. | | | | designed to garner information about how (and |
| | | | if) the weapons themselves work are weapons |
| Types of nuclear testing | | | | related tests, while tests designed to gain |
| | | | information about the effects of the weapons |
| Nuclear weapons tests have been historically | | | | themselves on structures or organisms are |
| broken into categories (by treaties) | | | | known as weapons effects tests. Additional |
| reflecting in what sort of medium or location | | | | types of nuclear tests are possible as well |
| the test has been conducted: atmospheric, | | | | (such as nuclear tests which are also part of |
| underwater, and underground. | | | | anti-ballistic missile testing). |
| | | | |
| Atmospheric testing designates explosions | | | | Nuclear-weapons-related testing which |
| which take place in or above the atmosphere. | | | | purposely results in no yield is known as |
| Generally these have occurred as devices | | | | subcritical testing, referring to the lack of |
| detonated on towers, balloons, barges, | | | | a creation of a critical mass of fissile |
| islands, or dropped from airplanes. A limited | | | | material. Additionally, there have been |
| number of high-altitude nuclear explosions | | | | non-nuclear simulations of nuclear tests |
| also conducted, generally fired from rockets. | | | | using conventional explosives (such as the |
| Nuclear explosions which are close enough to | | | | Minor Scale U.S. test in 1985). |