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In the Persian Gulf, Iran appears to many observers to be in the process of developing a nuclear weapon, which has greatly heightened fears of a nuclear conflict and arms races in the Middle East—either with Israel or with one or more Arab states (a "Shia-Sunni" conflict).

On March 7, 2013, North Korea threatened the United States with a preemptive nuclear strike.[44] Toshiba Satellite P100-238 CPU Fan

On April 9, North Korea urged foreigners to leave South Korea, stating that both countries were on the verge of nuclear war.[45] On April 12, North Korea stated that a nuclear war was unavoidable. The country declared Japan as its first target.

The above examples envisage nuclear warfare at a strategic level, i.e. total war. However, nuclear powers have the ability to undertake more limited engagements. ACER Aspire 5739 CPU Fan

"Sub-strategic use" includes the use of either "low-yield" tactical nuclear weapons, or of variable yield strategic nuclear weapons in a very limited role, as compared to battlefield exchanges of larger-yield strategic nuclear weapons. This was described by the UK Parliamentary Defence Select Committee as "the launch of one or a limited number of missiles against an adversary as a means of conveying a political message, IBM ThinkPad T40 2678 CPU Fan

warning or demonstration of resolve".[47] It is believed that all current nuclear weapons states possess tactical nuclear weapons, with the exception of the United Kingdom, which decommissioned its tactical warheads in 1998. However, the UK does possess scalable-yield strategic warheads, and this technology tends to blur the difference between "strategic", IBM Thinkpad T43 CPU Fan

"sub-strategic", and "tactical" use or weapons. American, French and British nuclear submarines are believed to carry at least some missiles with these types of high-tech warheads for this purpose - potentially allowing a strike as low as one kiloton (or less) against a single target. Only the People's Republic of Chinaand the Republic of India have declarative, unqualified, unconditional "no first use" nuclear weapons policies. IBM ThinkPad T43 2668 CPU Fan

Commodore Tim Hare, former Director of Nuclear Policy at the British Ministry of Defence, has described "sub-strategic use" as offering the Government "an extra option in the escalatory process before it goes for an all-out strategic strike which would deliver unacceptable damage".[48] However, this sub-strategic capacity has been criticized as potentially increasing the "acceptability" of using nuclear weapons. IBM ThinkPad T43 1871 CPU Fan

The related consideration of new generations of limited-yield nuclear weapons by the United States (i.e. "bunker busters") has also alarmed anti-nuclear groups, who believe it will make the use of nuclear weapons "more acceptable" or likely.

Also of note is that the United States adopted a policy in 1996 of allowing the targeting of its nuclear weapons at non-state actors ("terrorists") armed withweapons of mass destruction. ACER Travelmate 8104WLMI CPU Fan

Nuclear terrorism by non-state organizations or actors (even individuals) is a largely unknown and understudied factor in nuclear deterrence thinking, as states possessing nuclear weapons are susceptible to retaliation in kind, while sub- or trans-state actors may be less so. The collapse of the Soviet Union has given rise to the possibility that former Soviet nuclear weapons might become available on the black market (so-called 'loose nukes'). DELL Latitude E4300 CPU Fan

While no warheads are known to have been mislaid, it has been alleged that at least some very small or suitcase-size bombs might be unaccounted for.

A number of other concerns have been expressed about the security of nuclear weapons in other, newer nuclear powers with relatively less stable governments, such as Pakistan, ASUS F80S CPU Fan

but in each case, the fears have been addressed to some extent by statements and evidence provided by those nations, as well as cooperative programs between nations. Worry remains, however, in many circles that a relative decrease in security of nuclear weapons has emerged in recent years, HP Pavilion dv5-1058eo CPU Fan

and that terrorists or others may attempt to exert control over (or use) nuclear weapons, militarily applicable technology, or nuclear materials and fuel.

Another possible nuclear terrorism threat are devices designed to disperse radioactive materials over a large area using conventional explosives, called dirty bombs. The detonation of a "dirty bomb" would not cause a nuclear explosion, IBM 13N5182 CPU Fan

nor would it release enough radiation to kill or injure a lot of people. However, it could cause severe disruption and require potentially very costly decontamination procedures and increased spending on security measures.

The predictions of the effects of a major countervalue nuclear exchange include millions of city dweller deaths within a short period of time. IBM Thinkpad T30 2366-AA3 CPU Fan

Some predictions argue that a full-scale nuclear war could eventually bring about the extinction of the human race; however such pessimistic predictions, assuming total war with nuclear arsenals at Cold war highs, have not been without considerable criticism.[5] Nonetheless, a number of Cold War publications advocate preparations that can allegedly be taken in order to allow the majority of civilians to survive even a total nuclear war. IBM Thinkpad T30 CPU Fan

Among the most famous of these is the aptly namedNuclear War Survival Skills.[51]

To avoid injury and death from a nuclear weapons heat flash and blast effects, the two most far ranging prompt effects of nuclear weapons, schoolchildren were taught to duck and cover by the early cold war film of the same name. HP 535438-001 CPU Fan

Such advice is once again being given in case of nuclear terrorist attacks.[52]

Prussian blue, or "Radiogardase", is stockpiled in the US, along with potassium iodide and DPTA as pharmaceuticals useful in treating internal exposure to harmful radioisotopes in fallout.[53] DELL Inspiron N3010 CPU Fan

Publications on adapting to a changing diet and supplying nutritional food sources following a nuclear war, with particular focus on agricultural radioecology, include Nutrition in the postattack environment by the RAND corporation.[54]

Many countries maintain plans for continuity of government following a nuclear attack or similar disasters. HP Pavilion dv6-3070tx CPU Fan

The Soviet government believed they could win, not only a strategic nuclear war, which they planned to absorb with their extensive Civil Defense schemes and infrastructure dispersal,but also win the conventional war that they predicted would follow after their strategic nuclear arsenal had been depleted.[58] IBM 41W5269 CPU Fan

A number of other countries around the world have taken significant efforts to maximize their survival prospects in the event of large calamities, both natural and manmade. For example, metro stations in Pyongyang, North Korea, were constructed 110 metres (360 ft) below ground, and were designed to serve as nuclear shelters in the event of war, with each station entrance built with thick steel blast doors.[59][60] ASUS A8H CPU Fan

While examples of privately funded fallout shelters are theArk Two Shelter in Ontario, Canada, one of the best known privately constructed autonomous shelters, with a focus on post-war networking and reconstruction.[61]In Switzerland, the majority of homes have an underground blast and fallout shelter. The country has an overcapacity of such shelters and can accommodate slightly more than the nation's population size. SONY UDQFRZH13CF0 CPU Fan

Nuclear weapons possess enormous destructive power derived from nuclear fission or combined fission and fusionreactions. Starting with scientific breakthroughs made during the 1930s, the United States, the United Kingdom and Canada collaborated during World War II in what was called the Manhattan Project to counter the suspected Nazi German atomic bomb project. HP COMPAQ 2510P CPU Fan

In August 1945 two fission bombs were dropped on Japan ending the Pacific War. The Soviet Unionstarted development shortly thereafter with their own atomic bomb project, and not long after that both countries developed even more powerful fusion weapons known as "hydrogen bombs."

In the first decades of the 20th century, physics was revolutionised with developments in the understanding of the nature ofatoms. APPLE 661-4951 CPU Fan

In 1898, Pierre and Marie Curie discovered that pitchblende, an ore of uranium, contained a substance—which they namedradium—that emitted large amounts of radioactivity. Ernest Rutherford and Frederick Soddy identified that atoms were breaking down and turning into different elements. Hopes were raised among scientists and laymen that the elements around us could contain tremendous amounts of unseen energy, waiting to be harnessed. HP Pavilion dv6-3034ca CPU Fan

H. G. Wells was inspired to write about atomic weapons in a 1914 novel, The World Set Free, which appeared shortly before the First World War. In a 1924 article, Winston Churchill speculated about the possible military implications: "Might not a bomb no bigger than an orange be found to possess a secret power to destroy a whole block of buildings—nay to concentrate the force of a thousand tons of cordite and blast a township at a stroke?"[1] HP G56-126NR CPU Fan

In January 1933, Adolf Hitler was elected Chancellor of Germany and it quickly became unsafe for Jewish scientists to remain in the country. Leó Szilárd fled to London where he proposed, and in 1934 patented, the idea of a nuclear chain reaction vianeutrons. The patent also introduced the term critical mass to describe the minimum amount of material required to sustain the chain reaction and its potential to cause an explosion. Compaq Presario C556CA CPU Fan

(British patent 630,726.) He subsequently assigned the patent to theBritish Admiralty so that it could be covered by the Official Secrets Act.[2] In a very real sense, Szilárd was the father of the atomic bomb academically. Also in 1934, Irène and Frédéric Joliot-Curie discovered that artificial radioactivity could be induced in stable elements by bombarding them with alpha particles; SONY Vaio VGN-NR360E CPU Fan

Enrico Fermi reported similar results when bombarding uranium with neutrons.

In December 1938, Otto Hahn and Fritz Strassmann sent a manuscript to Naturwissenschaften reporting that they had detected the element barium after bombarding uranium with neutrons.[3] HP Pavilion dv5170us CPU Fan

Lise Meitner and her nephew Otto Robert Frisch correctly interpreted these results as being due to the splitting of the uranium atom. (Frisch confirmed this experimentally on January 13, 1939.[4]) They gave the process the name "fission" because of its similarity to the splitting of a cell into two new cells.[5] SONY Vaio VPC-EE3WFX/WI CPU Fan

Even before it was published, news of Meitner’s and Frisch’s interpretation crossed the Atlantic.[6] Scientists at Columbia University decided to replicate the experiment and on January 25, 1939, conducted the first nuclear fission experiment in the United States[7] in the basement of Pupin Hall.[8] HP G56-126NR CPU Fan

The following year, they identified the active component of uranium as being the rare isotope uranium-235.[9]

Uranium appears in nature primarily in two isotopes: uranium-238 and uranium-235. When the nucleus of uranium-235 absorbs a neutron, it undergoes nuclear fission, releasing energy and, on average, 2.5 neutrons. HP 3MLX8TATP20 CPU Fan

Because uranium-235 releases more neutrons than it absorbs, it can support a chain reaction and so is described as fissile. Uranium-238, on the other hand, is not fissile as it does not normally undergo fission when it absorbs a neutron.

By the time Nazi Germany invaded Poland in 1939, beginning World War II, many of Europe's top scientists had already fled the imminent conflict. SONY Vaio VGN-NW240F/S CPU Fan

Physicists on both sides were well aware of the possibility of utilizing nuclear fission as a weapon, but no one was quite sure how it could be done. In August 1939, concerned that Germany might have its own project to develop fission-based weapons, Albert Einstein signed a letter to U.S. President Franklin D. Roosevelt warning him of the threat.[10] SONY Vaio VPC-EB1Z0E/B CPU Fan

Roosevelt responded by setting up the Uranium Committee under Lyman James Briggs but, with little initial funding ($6,000), progress was slow. It was not until the Japanese attack on Pearl Harbor in December, 1941, that the U.S. decided to commit the necessary resources.[11]

Organized research first began in Britain as part of the Tube Alloys project. Compaq Presario CQ60-514NR CPU Fan

The Maud Committee was set up following the work of Frisch and Rudolf Peierls who calculated uranium-235's critical mass and found it to be much smaller than previously thought which meant that a deliverable bomb should be possible.[12] In the February 1940 Frisch–Peierls memorandum they stated that: Toshiba Satellite X205-S9800 CPU Fan

"The energy liberated in the explosion of such a super-bomb...will, for an instant, produce a temperature comparable to that of the interior of the sun. The blast from such an explosion would destroy life in a wide area. The size of this area is difficult to estimate, but it will probably cover the centre of a big city." ASUS G2P CPU Fan

Edgar Sengier, a director of Shinkolobwe Mine which produced by far the highest quality uranium ore in the world, had become aware of uranium's possible use in a bomb. In late 1940, fearful of its seizure by the Germans, he shipped the mine's entire stockpile of ore to a warehouse on Staten Island.[13] Compaq Presario CQ60-430SA CPU Fan

For 18 months British research outpaced the American but by mid-1942, it became apparent that the industrial effort required was beyond Britain's already stretched wartime economy.[14]:204 In September 1942, General Leslie Groves was appointed to lead the U.S. project which became known as the Manhattan Project. DELL BFB0505HA CPU Fan

Two of his first acts were to obtain authorization to assign the highest priority AAA rating on necessary procurements, and to put in train the purchase of all 1,250 tons of the Shinkolobwe ore.[13][15] The Tube Alloys project was quickly overtaken by the U.S. effort[14] and after Roosevelt and Churchill signed theQuebec Agreement in 1943, it was relocated and amalgamated into the Manhattan Project. HP Pavilion dv5-1272et CPU Fan

With a scientific team led by J. Robert Oppenheimer, the Manhattan project brought together some of the top scientific minds of the day, including many exiles from Europe, with the production power of American industry for the goal of producing fission-based explosive devices before Germany. Britain and the U.S. agreed to pool their resources and information for the project, Toshiba AB7005HX-SB3 CPU Fan

but the other Allied power, the Soviet Union (USSR), was not informed. The U.S. made an unprecedented investment in the project which at the time was the largest industrial enterprise ever seen,[14] spread across more than 30 sites in the U.S. and Canada. Scientific development was centralized in a secret laboratory at Los Alamos. Toshiba Satellite A500-18T CPU Fan

For a fission weapon to operate, there must be sufficient fissile material to support a chain reaction, a critical mass. To separate the fissile uranium-235 isotope from the non-fissile uranium-238, two methods were developed which took advantage of the fact that uranium-238 has a slightly greater atomic mass: electromagnetic separation and gaseous diffusion. HP Pavilion dv5-2135dx CPU Fan

Another secret site was erected at rural Oak Ridge, Tennessee, for the large-scale production and purification of the rare isotope, which required considerable investment. At the time, K-25, one of the Oak Ridge facilities, was the world's largest factory under one roof. The Oak Ridge site employed tens of thousands of people at its peak, most of whom had no idea what they were working on. ASUS EEE PC 1201NL CPU Fan

Although uranium-238 cannot be used for the initial stage of an atomic bomb, when it absorbs a neutron, it becomes uranium-239 which decays into neptunium-239, and finally the relatively stable plutonium-239, an element that does not exist naturally on Earth, but is fissile like uranium-235. SONY Vaio VGN-NW240D/T CPU Fan

After Fermi achieved the world's first sustained and controlled nuclear chain reaction with the creation of the first atomic pile, massive reactors were secretly constructed at what is now known as Hanford Site to transform uranium-238 into plutonium for a bomb.

The simplest form of nuclear weapon is a gun-type fission weapon, where a sub-critical mass would be shot at another sub-critical mass. Compaq Presario CQ60-418DX CPU Fan

The result would be a super-critical mass and an uncontrolled chain reaction that would create the desired explosion. The weapons envisaged in 1942 were the two gun-type weapons, Little Boy (uranium) and Thin Man (plutonium), and the Fat Man plutonium implosion bomb.

In early 1943 Oppenheimer determined that two projects should proceed forwards: SONY Vaio VGN-NW240D CPU Fan

the Thin Man project (plutonium gun) and the Fat Man project (plutonium implosion). The plutonium gun was to receive the bulk of the research effort, as it was the project with the most uncertainty involved. It was assumed that the uranium gun-type bomb could then be adapted from it.

In December 1943 the British mission of 19 scientists arrived in Los Alamos. Hans Bethebecame head of the Theoretical Division. SONY VGN-BX197XP CPU Fan

In April 1944 it was found by Emilio Segrè that the plutonium-239 produced by the Hanford reactors had too high a level of background neutron radiation, and underwentspontaneous fission to a very small extent, due to the unexpected presence of plutonium-240 impurities. If such plutonium were used in a gun-type design, Toshiba Satellite L645D-S4056 CPU Fan

the chain reaction would start in the split second before the critical mass was fully assembled, blowing the weapon apart with a much lower yield than expected, in what is known as afizzle.

As a result, development of Fat Man was given high priority. Chemical explosives were used to implode a sub-critical sphere of plutonium, thus increasing its density and making it into a critical mass. Toshiba AB7805HX-GB3 CPU Fan

The difficulties with implosion centered on the problem of making the chemical explosives deliver a perfectly uniform shock wave upon the plutonium sphere— if it were even slightly asymmetric, the weapon would fizzle. This problem was solved by the use of explosive lenses which would focus the blast waves inside the imploding sphere, akin to the way in which an optical lens focuses light rays.[16] Toshiba Satellite L500-208 CPU Fan

After D-Day, General Groves ordered a team of scientists to follow eastward-moving victorious Allied troops into Europe to assess the status of the German nuclear program (and to prevent the westward-moving Russians from gaining any materials or scientific manpower). They concluded that, while Germany had an atomic bomb program headed byWerner Heisenberg, HP 535441-001 CPU Fan

the government had not made a significant investment in the project, and it had been nowhere near success.

Historians claim to have found a rough schematic showing a Nazi nuclear bomb.[17] In March 1945, a German scientific team was directed by the physicist Kurt Diebner to develop a primitive nuclear device inOhrdruf, Thuringia.[17][18] Toshiba Satellite P100-444 CPU Fan

Last ditch research was conducted in an experimental nuclear reactor at Haigerloch.

On April 12, after Roosevelt's death, Vice-President Harry S. Truman assumed the presidency. At the time of the unconditional surrender of Germany on May 8, 1945, the Manhattan Project was still months away from producing a working weapon. HP Pavilion dv7-3114eo CPU Fan

Because of the difficulties in making a working plutonium bomb, it was decided that there should be a test of the weapon. On July 16, 1945, in the desert north of Alamogordo, New Mexico, the first nuclear test took place, code-named "Trinity", using a device nicknamed "the gadget." The test, a plutonium implosion type device, released energy equivalent to 19 kilotons of TNT, HP Mini 110-1125SA CPU Fan

far more powerful than any weapon ever used before. The news of the test's success was rushed to Truman at the Potsdam Conference, where Churchill was briefed and Joseph Stalin was informed of the new weapon. On July 26, thePotsdam Declaration was issued containing an ultimatum for Japan: either surrender or suffer "complete and utter destruction", although nuclear weapons were not mentioned. HP KSB06105HA CPU Fan

After hearing arguments from scientists and military officers over the possible uses of the weapons against Japan (though some recommended using them as demonstrations in unpopulated areas, most recommended using them against built up targets, a euphemistic term for populated cities), Truman ordered the use of the weapons on Japanese cities, Compaq Presario CQ60-210eo CPU Fan

hoping it would send a strong message that would end in the capitulation of the Japanese leadership and avoid a lengthy invasion of the islands. On May 10–11, 1945, the Target Committee at Los Alamos, led by Oppenheimer, recommended Kyoto, Hiroshima, Yokohama, and the arsenal at Kokura as possible targets. HP Pavilion dv7-2250sf CPU Fan

Concerns about Kyoto's cultural heritage led to it being replaced by Nagasaki.

On August 6, 1945, a uranium-based weapon, Little Boy, was detonated above the Japanese city of Hiroshima. Three days later, a plutonium-based weapon, Fat Man, was detonated above the city of Nagasaki. The atomic bombs killed at least one hundred thousand Japanese outright, most of them civilians, with the heat, radiation, and blast effects. HP 434678-001 CPU Fan

Many tens of thousands would later die of radiation sickness and related cancers.[19][20] Truman promised a "rain of ruin" if Japan did not surrender immediately, threatening to systematically eliminate their ability to wage war.[21] On August 15, Emperor Hirohito announced Japan's surrender. HP G60-230us CPU Fan

The Soviet Union was not invited to share in the new weapons developed by the United States and the other Allies. During the war, information had been pouring in from a number of volunteer spies involved with the Manhattan Project (known in Soviet cables under the code-name of Enormoz), HP Pavilion dv6365us CPU Fan

and the Soviet nuclear physicist Igor Kurchatov was carefully watching the Allied weapons development. It came as no surprise to Stalin when Truman had informed him at the Potsdam conference that he had a "powerful new weapon." Truman was shocked at Stalin's lack of interest.

The Soviet spies in the U.S. project were all volunteers and none were Russians. HP 535439-001 CPU Fan

One of the most valuable, Klaus Fuchs, was a German émigré theoretical physicist who had been part of the early British nuclear efforts and the UK mission to Los Alamos. Fuchs had been intimately involved in the development of the implosion weapon, and passed on detailed cross-sections of the Trinity device to his Soviet contacts. COMPAQ 6910c CPU Fan

Other Los Alamos spies—none of whom knew each other—included Theodore Hall and David Greenglass. The information was kept but not acted upon, as Russia was still too busy fighting the war in Europe to devote resources to this new project.

In the years immediately after World War II, the issue of who should control atomic weapons became a major international point of contention. IBM Lenovo IdeaPad G510 CPU Fan

Many of the Los Alamos scientists who had built the bomb began to call for "international control of atomic energy," often calling for either control by transnational organizations or the purposeful distribution of weapons information to all superpowers, but due to a deep distrust of the intentions of the Soviet Union, both in postwar Europe and in general, the policy-makers of the United States worked to attempt to secure an American nuclear monopoly. HP G62-110SO CPU Fan

A half-hearted plan for international control was proposed at the newly formed United Nations by Bernard Baruch (The Baruch Plan), but it was clear both to American commentators—and to the Soviets—that it was an attempt primarily to stymie Russian nuclear efforts. DELL Precision M6400 CPU Fan

The Soviets vetoed the plan, effectively ending any immediate postwar negotiations on atomic energy, and made overtures towards banning the use of atomic weapons in general.

The Soviets had put their full industrial might and manpower into the development of their own atomic weapons. SONY Vaio VPC-EB290X CPU Fan

The initial problem for the Soviets was primarily one of resources—they had not scouted out uranium resources in the Soviet Union and the U.S. had made deals to monopolise the largest known (and high purity) reserves in the Belgian Congo. The USSR used penal labour to mine the old deposits in Czechoslovakia—now an area under their control—and searched for other domestic deposits (which were eventually found). HP Envy 17-1090eo CPU Fan

Two days after the bombing of Nagasaki, the U.S. government released an official technical history of the Manhattan Project, authored by Princeton physicistHenry DeWolf Smyth, known colloquially as the Smyth Report. The sanitized summary of the wartime effort focused primarily on the production facilities and scale of investment, written in part to justify the wartime expenditure to the American public. Toshiba Satellite A210-1CF CPU Fan

The Soviet program, under the suspicious watch of former NKVD chief Lavrenty Beria (a participant and victor in Stalin's Great Purge of the 1930s), would use the Report as a blueprint, seeking to duplicate as much as possible the American effort. The "secret cities" used for the Soviet equivalents of Hanford and Oak Ridge literally vanished from the maps for decades to come. Dell Vostro 3450 CPU Fan

At the Soviet equivalent of Los Alamos, Arzamas-16, physicist Yuli Khariton led the scientific effort to develop the weapon. Beria distrusted his scientists, however, and he distrusted the carefully collected espionage information. As such, Beria assigned multiple teams of scientists to the same task without informing each team of the other's existence. Toshiba Satellite A10-103 CPU Fan

If they arrived at different conclusions, Beria would bring them together for the first time and have them debate with their newfound counterparts. Beria used the espionage information as a way to double-check the progress of his scientists, and in his effort for duplication of the American project even rejected more efficient bomb designs in favor of ones that more closely mimicked the tried-and-true Fat Man bomb used by the U.S. against Nagasaki. Compaq Presario A900 CTO CPU Fan

Working under a stubborn and scientifically ignorant administrator, the Soviet scientists struggled on. On August 29, 1949, the effort brought its results, when the USSR tested its first fission bomb, dubbed "Joe-1" by the U.S., years ahead of American predictions. The news of the first Soviet bomb was announced to the world first by the United States, which had detected the nuclear fallout it generated from its test site in Kazakhstan. ACER Aspire 4736ZG CPU Fan

The loss of the American monopoly on nuclear weapons marked the first tit-for-tat of the nuclear arms race. The response in the U.S. was one of apprehension, fear, and scapegoating, which would lead eventually into the Red-baiting tactics of McCarthyism. Yet recent information from unclassified Toshiba Satellite A10-103 CPU Fan

Venona intercepts and the opening of the KGB archives after the fall of the Soviet Union show that the USSR had useful spies that helped their program, although none were identified by McCarthy. Before this, though, President Truman announced a decision to begin a crash program that would develop a far more powerful weapon than those the U.S. used against Japan: the hydrogen bomb. SONY MCF-519PAM05 CPU Fan

The Soviet Union was not invited to share in the new weapons developed by the United States and the other Allies. During the war, information had been pouring in from a number of volunteer spies involved with the Manhattan Project (known in Soviet cables under the code-name of Enormoz), and the Soviet nuclear physicist Igor Kurchatov was carefully watching the Allied weapons development. SONY Vaio VPC-EB290X CPU Fan

It came as no surprise to Stalin when Truman had informed him at the Potsdam conference that he had a "powerful new weapon." Truman was shocked at Stalin's lack of interest.

The Soviet spies in the U.S. project were all volunteers and none were Russians. One of the most valuable, Klaus Fuchs, was a German émigré theoretical physicist who had been part of the early British nuclear efforts and the UK mission to Los Alamos. HP Pavilion dv7-2043cl CPU Fan

Fuchs had been intimately involved in the development of the implosion weapon, and passed on detailed cross-sections of the Trinity device to his Soviet contacts. Other Los Alamos spies—none of whom knew each other—included Theodore Hall and David Greenglass. The information was kept but not acted upon, as Russia was still too busy fighting the war in Europe to devote resources to this new project. HP Pavilion dv7-2130ev CPU Fan

In the years immediately after World War II, the issue of who should control atomic weapons became a major international point of contention. Many of the Los Alamos scientists who had built the bomb began to call for "international control of atomic energy," often calling for either control by transnational organizations or the purposeful distribution of weapons information to all superpowers, HP 608772-001 CPU Fan

but due to a deep distrust of the intentions of the Soviet Union, both in postwar Europe and in general, the policy-makers of the United States worked to attempt to secure an American nuclear monopoly.

A half-hearted plan for international control was proposed at the newly formed United Nations by Bernard Baruch (The Baruch Plan), Toshiba Satellite A100-194 CPU Fan

but it was clear both to American commentators—and to the Soviets—that it was an attempt primarily to stymie Russian nuclear efforts. The Soviets vetoed the plan, effectively ending any immediate postwar negotiations on atomic energy, and made overtures towards banning the use of atomic weapons in general. HP Pavilion tx1205/ CT CPU Fan

The Soviets had put their full industrial might and manpower into the development of their own atomic weapons. The initial problem for the Soviets was primarily one of resources—they had not scouted out uranium resources in the Soviet Union and the U.S. had made deals to monopolise the largest known (and high purity) reserves in the Belgian Congo. HP Pavilion dv6640ep CPU Fan

The USSR used penal labour to mine the old deposits in Czechoslovakia—now an area under their control—and searched for other domestic deposits (which were eventually found).

Two days after the bombing of Nagasaki, the U.S. government released an official technical history of the Manhattan Project, authored by Princeton physicistHenry DeWolf Smyth, known colloquially as the Smyth Report. COMPAQ Presario CQ42-401TU CPU Fan

The sanitized summary of the wartime effort focused primarily on the production facilities and scale of investment, written in part to justify the wartime expenditure to the American public.

The Soviet program, under the suspicious watch of former NKVD chief Lavrenty Beria (a participant and victor in Stalin's Great Purge of the 1930s), would use the Report as a blueprint, seeking to duplicate as much as possible the American effort. Toshiba Satellite A300D CPU Fan

The "secret cities" used for the Soviet equivalents of Hanford and Oak Ridge literally vanished from the maps for decades to come.

At the Soviet equivalent of Los Alamos, Arzamas-16, physicist Yuli Khariton led the scientific effort to develop the weapon. Beria distrusted his scientists, however, and he distrusted the carefully collected espionage information. HP Pavilion dv8397ea CPU  Fan

As such, Beria assigned multiple teams of scientists to the same task without informing each team of the other's existence. If they arrived at different conclusions, Beria would bring them together for the first time and have them debate with their newfound counterparts. Beria used the espionage information as a way to double-check the progress of his scientists, HP Pavilion dv9821ea CPU Fan

and in his effort for duplication of the American project even rejected more efficient bomb designs in favor of ones that more closely mimicked the tried-and-true Fat Man bomb used by the U.S. against Nagasaki.

Working under a stubborn and scientifically ignorant administrator, the Soviet scientists struggled on. On August 29, 1949, the effort brought its results, HP COMPAQ TC4200 CPU Fan

when the USSR tested its first fission bomb, dubbed "Joe-1" by the U.S., years ahead of American predictions. The news of the first Soviet bomb was announced to the world first by the United States, which had detected the nuclear fallout it generated from its test site in Kazakhstan.

The loss of the American monopoly on nuclear weapons marked the first tit-for-tat of the nuclear arms race. SONY Vaio VGN-NW228F CPU Fan

The response in the U.S. was one of apprehension, fear, and scapegoating, which would lead eventually into the Red-baiting tactics of McCarthyism. Yet recent information from unclassified Venona intercepts and the opening of the KGB archives after the fall of the Soviet Union show that the USSR had useful spies that helped their program, HP G62-b16ST CPU Fan

although none were identified by McCarthy.[citation needed] Before this, though, President Truman announced a decision to begin a crash program that would develop a far more powerful weapon than those the U.S. used against Japan: the hydrogen bomb.

The notion of using a fission weapon to ignite a process of nuclear fusion can be dated back to 1942. HP 580696-001 CPU Fan

At the first major theoretical conference on the development of an atomic bomb hosted by J. Robert Oppenheimer at the University of California, Berkeley, participant Edward Teller directed the majority of the discussion towards Enrico Fermi's idea of a "Super" bomb that would use the same reactions that powered the Sun itself. HP Pavilion dv6-3049tx CPU Fan

It was thought at the time that a fission weapon would be quite simple to develop and that perhaps work on a hydrogen bomb (thermonuclear weapon) would be possible to complete before the end of the Second World War. However, in reality the problem of a regular atomic bomb was large enough to preoccupy the scientists for the next few years, HP G42-380LA CPU Fan

much less the more speculative "Super" bomb. Only Teller continued working on the project—against the will of project leaders Oppenheimer and Hans Bethe.

After the atomic bombings of Japan, many scientists at Los Alamos rebelled against the notion of creating a weapon thousands of times more powerful than the first atomic bombs. Toshiba Qosmio G30-167 CPU Fan

For the scientists the question was in part technical—the weapon design was still quite uncertain and unworkable—and in part moral: such a weapon, they argued, could only be used against large civilian populations, and could thus only be used as a weapon of genocide.

Many scientists, such as Bethe, urged that the United States should not develop such weapons and set an example towards the Soviet Union. HP Pavilion dv7-1157cl CPU Fan

Promoters of the weapon, including Teller, Ernest Lawrence, and Luis Alvarez, argued that such a development was inevitable, and to deny such protection to the people of the United States—especially when the Soviet Union was likely to create such a weapon themselves—was itself an immoral and unwise act. Compaq Presario CQ40-408AX CPU Fan

Oppenheimer, who was now head of the General Advisory Committee of the successor to the Manhattan Project, the Atomic Energy Commission, presided over a recommendation against the development of the weapon. The reasons were in part because the success of the technology seemed limited at the time (and not worth the investment of resources to confirm whether this was so), HP Mini 110-1110ET CPU Fan

and because Oppenheimer believed that the atomic forces of the United States would be more effective if they consisted of many large fission weapons (of which multiple bombs could be dropped on the same targets) rather than the large and unwieldy super bombs, for which there was a relatively limited number of targets of sufficient size to warrant such a development. HP Pavilion dv7-1157cl CPU Fan

Furthermore, were such weapons developed by both the U.S. and the USSR, they would be more effectively used against the U.S. than by it, as the U.S. had far more regions of dense industrial and civilian activity as targets for large weapons than the Soviet Union.

In the end, President Truman made the final decision, looking for a proper response to the first Soviet atomic bomb test in 1949. HP Pavilion dv6-3163eo CPU Fan

On January 31, 1950, Truman announced a crash program to develop the hydrogen (fusion) bomb. At this point, however, the exact mechanism was still not known: the classical hydrogen bomb, whereby the heat of the fission bomb would be used to ignite the fusion material, seemed highly unworkable. HP Pavilion dv9740us CPU Fan

However, an insight by Los Alamos mathematician Stanislaw Ulam showed that the fission bomb and the fusion fuel could be in separate parts of the bomb, and thatradiation of the fission bomb could first work in a way to compress the fusion material before igniting it.

Teller pushed the notion further, and used the results of the boosted-fission "George" test HP COMPAQ NX9420 CPU Fan

(a boosted-fission device using a small amount of fusion fuel to boost the yield of a fission bomb) to confirm the fusion of heavy hydrogen elements before preparing for their first true multi-stage, Teller-Ulam hydrogen bomb test. Many scientists initially against the weapon, such as Oppenheimer and Bethe, changed their previous opinions, seeing the development as being unstoppable. HP Pavilion dv7-4150ec CPU Fan

The first fusion bomb was tested by the United States in Operation Ivy on November 1, 1952, on Elugelab Island in the Enewetak (or Eniwetok) Atoll of the Marshall Islands, code-named "Mike." Mike used liquid deuterium as its fusion fuel and a large fission weapon as its trigger. The device was a prototype design and not a deliverable weapon: HP Pavilion dv5-1102tu CPU Fan

standing over 20 ft (6 m) high and weighing at least 140,000 lb (64 t) (its refrigeration equipment added an additional 24,000 lb (11,000 kg) as well), it could not have been dropped from even the largest planes.

Its explosion yielded energy equivalent to 10.4 megatons of TNT—over 450 times the power of the bomb dropped onto Nagasaki— and obliterated Elugelab, SONY VGN-SZ220 CPU Fan

leaving an underwater crater 6240 ft (1.9 km) wide and 164 ft (50 m) deep where the island had once been. Truman had initially tried to create a media blackout about the test—hoping it would not become an issue in the upcoming presidential election—but on January 7, 1953, Truman announced the development of the hydrogen bomb to the world as hints and speculations of it were already beginning to emerge in the press. HP Pavilion dv7-6011tx CPU Fan

Not to be outdone, the Soviet Union exploded its first thermonuclear device, designed by the physicist Andrei Sakharov, on August 12, 1953, labeled "Joe-4" by the West. 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. HP Pavilion dv5-1040eb CPU Fan

This first device though was arguably not a true hydrogen bomb, and could only reach explosive yields in the hundreds of kilotons (never reaching the megaton range of a staged weapon). Still, it was a powerful propaganda tool for the Soviet Union, and the technical differences were fairly oblique to the American public and politicians. ASUS F3Jv CPU Fan

Following the Mike blast by less than a year, Joe-4 seemed to validate claims that the bombs were inevitable and vindicate those who had supported the development of the fusion program. Coming during the height of McCarthyism, the effect was pronounced on the security hearings in early 1954, IBM ThinkPad R50p 2887 CPU Fan

which revoked former Los Alamos director Robert Oppenheimer's security clearance on the grounds that he was unreliable, had not supported the American hydrogen bomb program, and had made long-standing left-wing ties in the 1930s. Edward Teller participated in the hearing as the only major scientist to testify against Oppenheimer, resulting in his virtual expulsion from the physics community. SONY VGN-CS36GJ/R CPU Fan

On March 1, 1954, the U.S. detonated its first practical thermonuclear weapon (which used isotopes of lithium as its fusion fuel), known as the "Shrimp" device of the Castle Bravo test, at Bikini Atoll, Marshall Islands. The device yielded 15 megatons, more than twice its expected yield, and became the worstradiological disaster in U.S. history. Toshiba Satellite A215-S4807 CPU Fan

The combination of the unexpectedly large blast and poor weather conditions caused a cloud of radioactive nuclear fallout to contaminate over 7,000 square miles (18,000 km2). 239 Marshall Island natives and 28 Americans were exposed to significant amounts of radiation, resulting in elevated levels of cancer and birth defects in the years to come.[25] Toshiba Satellite Pro M10-SP405 CPU Fan

The crew of the Japanese tuna-fishing boat Lucky Dragon 5, who had been fishing just outside the exclusion zone, returned to port suffering from radiation sickness and skin burns. Efforts were made to recover the contaminated fish but at least two large tuna were probably sold and eaten. HP Pavilion dv4-1120us CPU Fan

A further 75 tons of tuna caught between March and December were found to be unfit for human consumption. When a crew member died and the full results of the contamination were made public by the U.S., Japanese concerns were reignited about the hazards of radiation.

The hydrogen bomb age had a profound effect on the thoughts of nuclear war in the popular and military mind. Compaq Presario C550EM CPU Fan

With only fission bombs, nuclear war was something that possibly could be limited. Dropped by planes and only able to destroy the most built up areas of major cities, it was possible for many to look at fission bombs as a technological extension of large-scale conventional bombing—such as the extensive firebombing against Japan and Germany during World War II). Toshiba Qosmio E15-AV101 CPU Fan

Proponents brushed aside as grave exaggeration claims that such weapons could lead to worldwide death or harm.

Even in the decades before fission weapons, there had been speculation about the possibility for human beings to end all life on the planet, either by accident or purposeful maliciousness—but technology had not provided the capacity for such action. Toshiba Satellite L645D-S4056 CPU Fan

The great power of hydrogen bombs made world-wide annihilation possible.

The Castle Bravo incident itself raised a number of questions about the survivability of a nuclear war. Government scientists in both the U.S. and the USSR had insisted that fusion weapons, unlike fission weapons, were cleaner, as fusion reactions did not produce the dangerously radioactive by-products of fission reactions. Toshiba Satellite A305-S6837 CPU Fan

While technically true, this hid a more gruesome point: the last stage of a multi-staged hydrogen bomb often used the neutrons produced by the fusion reactions to induce fissioning in a jacket of natural uranium, and provided around half of the yield of the device itself.

This fission stage made fusion weapons considerably more dirty than they were made out to be. HP Pavilion dv7-4087cl CPU Fan

This was evident in the towering cloud of deadly fallout that followed the Bravo test. When the Soviet Union tested its first megaton device in 1955, the possibility of a limited nuclear war seemed even more remote in the public and political mind. Even cities and countries that were not direct targets would suffer fallout contamination. HP Pavilion dv5-1118es CPU Fan

Extremely harmful fission products would disperse via normal weather patterns and embed in soil and water around the planet.

Speculation began to run towards what fallout and dust from a full-scale nuclear exchange would do to the world as a whole, rather than just cities and countries directly involved. In this way, the fate of the world was now tied to the fate of the bomb-wielding superpowers.HP Pavilion G72-259WM CPU Fan,HP Pavilion dv6-3109ca  CPU  Fan,HP Pavilion dv6782eg CPU Fan

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