A nuclear weapon is a weapon of enormous destructive potential, deriving its energy from nuclear fission or nuclear fusion reactions.
These weapons were initially developed in the United States during World War II in the Manhattan Project. A considerable amount of international negotiating has focused on the threat of nuclear warfare and the proliferation of nuclear weapons to new nations or groups.
This article discusses the historical development of nuclear weapons. Related articles include: nuclear weapons, nuclear weapon design, nuclear explosion, nuclear warfare, nuclear proliferation, nuclear strategy, nuclear reactor, Manhattan Project, Los Alamos National Laboratory
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2 World War II 3 Cold War 4 Hydrogen bomb 5 Other countries with nuclear weapons 6 Nuclear test explosions 7 See also 8 References 9 External links |
In 1905 Albert Einstein published his special theory of relativity. According to this theory, the relation between mass and energy is expressed by the equation E = mc˛, which states that a given mass (m) is associated with an amount of energy (E) equal to this mass multiplied by the square of the speed of light (c). A very small amount of matter is equivalent to a vast amount of energy.
In 1932 the neutron particle was discovered by James Chadwick.
In 1938 German chemists Otto Hahn and Fritz Strassmann were able to split the uranium atom into two roughly equal parts by bombarding it with neutrons. As a result of these experiments, the Austrian physicist Lise Meitner, with her nephew, the British physicist Otto Robert Frisch, were able to explain the process of nuclear fission in 1939, placing the release of atomic energy within reach.
Thus, the potential of nuclear reactions to be used for weapons of extremely high destructive power was known by the time World War II broke out. The leaders of the Allied nations were particularly concerned about Germany producing such weapons, and so began the Manhattan Project which brought the top minds in nuclear physics together, led by Robert Oppenheimer, under the U. S. military direction of Brigadier General Leslie Groves, with the goal of producing fission-based explosive devices. Britain and the U.S. agreed to pool their resources and information for the project, but the Soviet Union was not informed.
A massive industrial and scientific undertaking, Manhattan involved many of the world's great physicists in the scientific and development aspects. The work was centered around the laboratories at Los Alamos, New Mexico.
As part of the project, the world's first sustained and controlled nuclear chain reaction was achieved at the University of Chicago under the supervision of Enrico Fermi. Apart from Chicago and Los Alamos, the Hanford Site in the state of Washington and Oak Ridge were the sites of large-scale production and purification of fissionable material.
The Manhattan Project was unable to produce fission-based weapons prior to the unconditional surrender of Germany on May 8, 1945, but was able to produce a test device (exploded at the Trinity site) and two deliverable devices, one using uranium 235 as fissionable material (known as Little Boy) and another using plutonium as fissionable material (known as Fat Man).
The 1945 Potsdam Declaration called for unconditional surrender by Japan; the Japanese, however, wanting a guarantee that their emperor would remain on the throne before they would surrender, continued fighting. Facing the prospects of a long, bloody, grueling "island hopping" campaign to conquer Japan (and also wishing to intimidate the Soviet Union), U.S. President Harry Truman chose to enforce Japanese surrender by using the newly developed nuclear weapons. Little Boy was thus delivered to the Japanese city of Hiroshima by the bomber Enola Gay, and Fat Man by Bocks Car to Nagasaki. These two bombings are still the only instances when atomic weapons were used in warfare. Ironically, after the Japanese did surrender, they were allowed to retain their emperor as a symbol.
Nazi Germany had also attempted to develop nuclear weapons, but erroneously concluded that slow neutron fission could not cascade fast enough to cause an explosion. Their physicists, including Werner Heisenberg and Otto Hahn, may have deliberately refused to notice fast neutron fission. Germany attempted to develop power reactors, but its supplies of graphite were poisoned by boron, a neutron absorber injected by the boron electrodes then used to provide commercial graphite. As a result, the Nazi reactor program attempted to develop heavy water reactors and was hampered by supply and purity problems. Leo Szilard, a Hungarian physicist trained as an industrial chemist, successfully prevented this problem with American reactors, which used graphite.
Germany probably tried to assist Japan in producing a nuclear weapon: in May 1945, the US captured a U-boat heading for Japan with uranium oxide containing a fifth of the total U-235 needed to make one bomb. However, documents discovered in 2001 indicate that Japanese scientists were years away from completing their 20-kilotonne A-bomb. The captured German uranium may have contributed to what was needed for the US bombs.
On August 9, 1949, the Soviet Union detonates its first atomic device, ending the United States monopoly on having nuclear bombs.
It is now known that the Soviet Union was able to develop nuclear weapons in relatively short time because of its espionage activities in the United States and the United Kingdom. Prime Minister Winston Churchill announced on February 26, 1952, that the United Kingdom also had an atomic bomb. France and China also demonstrated nuclear capability, and these five countries were considered to be the 'Nuclear Powers' throughout the Cold War period.
After World War II, the balance of power between the Eastern and Western blocs, resulting in the fear of global destruction, prevented the further military use of atomic bombs. This fear was even a central part of Cold War strategy, referred to as the doctrine of Mutually Assured Destruction ("MAD" for short). So important was this balance to international political stability that a treaty, the Antiballistic Missile Treaty (or ABM treaty) was signed by the US and the USSR in 1972 to curtail the development of defenses against nuclear weapons and the ballistic missiles which carry them. This doctrine resulting in a large increase in the number of nuclear weapons, as each side sought to ensure it posessed the firepower to destroy the opposition in all possible scenarios and against all perceived threats.
Early delivery systems for nuclear devices were primarily bombers like the American B-29 Superfortress and B-36 Peacemaker, and later the B-52 Stratofortress. Ballistic missile systems, based on designs used by Germany under Wernher von Braun (specifically the V2 rocket), were developed by both American and Soviet teams of captured scientists and engineers from this program. These systems, after testing, were used to launch satellites, such as Sputnik, and to propel the Space Race, but they were primarily developed to create the capability of Intercontinental Ballistic Missiles (ICBMs) with which nuclear powers could deliver that destructive force anywhere on the globe. These systems continued to be developed throughout the Cold War, although plans and treaties, beginning with the Strategic Arms Limitation Treaty (SALT I), restricted deployment of these systems until, after the fall of the Soviet Union, system development essentially halted, and many weapons were disabled and destroyed (see nuclear disarmament).
There have been a number of potential nuclear disasters. Following air accidents US nuclear weapons have been lost near Atlantic City, New Jersey (1957), Savannah, Georgia (1958), Goldsboro, North Carolina (1961), off the coast of Okinawa (1965), in the sea near Palmores, Spain (1966) and near Thule, Greenland (1968). Most of the lost weapons were recovered, the Spanish device after three months' effort by the DSV Alvin and DSV Aluminaut. The Soviet Union was less forthcoming about such incidents, but the environmental group Greenpeace believes that there are around forty non-US nuclear devices that have been lost and not recovered, compared to eleven lost by America, mostly in submarine disasters. The US have tried to recover Soviet devices, notably in the 1974 Operation Jennifer using the specialist salvage vessel Hughes Glomar Explorer.
On January 27, 1967, more than 60 nations signed the Outer Space Treaty banning nuclear weapons in space.
The end of the Cold War failed to bring an end to the threat of the use of nuclear weapons, although global fears of nuclear war reduced substantially.
In a major major move of deescalation, Boris Yeltsin on January 26, 1992 announced that Russia planned to stop targeting United States cities with nuclear weapons.
On January 31, 1950, Truman announced a program to develop the hydrogen (fusion) bomb.
The U.S. were the first to test a fusion bomb in Operation Ivy on November 1, 1952, on Elugelab Island in the Enewetak (or Eniwetok) Atoll of the Marshall Islands, code-named Mike. It yielded 10.4 megatons of explosive power (equal to 10.4 million tons of TNT), which is over 450 times the power of the bomb that fell on Nagasaki. Mike used liquid deuterium as the fusion fuel and had a 92 point ignition system. It was 20 ft high, 6 ft 8 in wide, and weighting 140,000 lb (164,000 lb including attached refrigeration and measuring equipment). The detonation obliterated Elugelab, leaving an underwater crater 6240 ft wide and 164 ft deep where an island had once been. On January 7, 1953, Truman announced the development of the hydrogen bomb.
The Soviet Union exploded its first thermonuclear device on August 12, 1953. (This created concern within the U. S. government and military, because, unlike "Mike," the Soviet device was a deliverable weapon, which the U. S. did not yet have). Thermonuclear devices were exploded by Great Britain on May 15, 1957, (Operation Grapple, test off Malden Island), France (February 13, 1960), and China (October 16, 1964).
India exploded a thermonuclear device in 1998.
France made a point of conducting above-ground tests of nuclear weapons in the 1990s.
India's first test atomic explosion was in 1974 with Smiling Buddha, which it initially described as a 'peaceful nuclear explosion'. India tested both fusion and fission devices in 1998 and Pakistan successfully tested fission devices that same year, raising concerns that they would use nuclear weapons on each other.
The fall of the Soviet Union spread the possession and control of the Soviet nuclear arsenal over several former Soviet republics, and their economic need and the lack of opportunity for Soviet nuclear physicists created opportunities for Third World countries to hire developers and buy materials and supplies, which may have accelerated the nuclear programs of nations such as India, Pakistan, and Iraq. The proliferation of nuclear weapons to these nations is prohibited by the international Nuclear Non-Proliferation Treaty.
South Africa also had an active program to develop uranium based nuclear weapons, but dismantled its nuclear weapon program in the 1990s. It is not believed that it actually tested such a weapon. In the late 1970s American spy satellites detected what appeared to be a flash of gamma rays, but a later scientific review of the data suggested it may have been caused by natural events.
Israel is also suspected by some to possess an arsenal of potentially up to several hundred nuclear warheads, but this has never been openly confirmed. The United Kingdom has its own nuclear weapons but has not run an independent development program since the failure of Blue Streak missile in the 1960s, buying American delivery systems and fitting British warheads instead (Polaris Sales Agreement).
China also possesses a small arsenal of nuclear warheads. In 2003, North Korea announced it also had several nuclear explosives.
There have been around 2,000 nuclear explosions:
Development
World War II
Cold War
Hydrogen bomb
Other countries with nuclear weapons
Nuclear test explosions
Australian government database of nuclear explosions and testsSee also
References
External links
