Nuclear weapon: the story on HearLore

Nuclear weapon

On the 16th of July 1945, the desert sky above the Trinity Test Site in New Mexico did not simply light up; it became a second sun. J. Robert Oppenheimer, the scientific director of the Manhattan Project, watched the first detonation of a nuclear weapon and later recalled a verse from the Hindu scripture Bhagavad Gita, stating, I am become Death, the destroyer of worlds. This moment marked the transition of human history from the age of chemical explosives to the age of nuclear annihilation, where a device weighing less than a ton could release energy equivalent to 20,000 tons of TNT. The physics behind this event relied on forcing a mass of fissile material, such as uranium-235 or plutonium-239, into a state of supercriticality. This process allowed an exponential growth of nuclear chain reactions, either by shooting one piece of sub-critical material into another using the gun method or by compressing a sphere of material using chemically fueled explosive lenses known as the implosion method. The implosion method proved to be more sophisticated and efficient, requiring less of the expensive fissile fuel to achieve a devastating result. The Trinity test was the culmination of a massive scientific and industrial complex that had been built in secret, primarily to produce the necessary fissile material from nuclear reactors or uranium enrichment facilities. The success of this test paved the way for the first use of nuclear weapons in warfare just three months later, when the United States Army Air Forces detonated a uranium gun-type fission bomb nicknamed Little Boy over the Japanese city of Hiroshima on the 6th of August 1945. Three days later, on the 9th of August, a plutonium implosion-type fission bomb nicknamed Fat Man was detonated over Nagasaki, causing injuries that resulted in the deaths of approximately 200,000 civilians and military personnel. The ethical justification for these bombings and their role in Japan's surrender remain subjects of intense debate to this day, yet the physical reality of the explosion was undeniable and permanent.

The Demon Core

Before the world saw the mushroom cloud, the scientists who built the bomb nearly destroyed themselves with the very material they sought to control. Between the 21st of August 1945 and the 21st of May 1946, two physicists, Harry Daghlian and Louis Slotin, conducted experiments on a plutonium-gallium core at Los Alamos National Laboratory. In both instances, a human error caused the core to enter prompt criticality, releasing a lethal dose of radiation. Daghlian died 25 days later on the 15th of September 1945, and Slotin died nine days later on the 30th of May 1946. The mass became known as the Demon Core, a grim reminder of the volatility of the material. It was ultimately used to construct a bomb for use on the Nevada Test Range, but the accidents highlighted the inherent danger of the technology. The production and deployment of nuclear weapons have involved many accidents that resulted in either some radiation casualties or the near-miss possibility of an unauthorized and unintended detonation. On the 13th of February 1950, a Convair B-36B crashed in northern British Columbia after jettisoning a Mark IV atomic bomb, marking the first such nuclear weapon loss in history. Experts believe that up to 50 nuclear weapons were lost during the Cold War, a statistic that underscores the fragility of the safety systems designed to prevent accidental war. On the 22nd of May 1957, a Mark-17 hydrogen bomb accidentally fell from a bomber near Albuquerque, New Mexico, detonating its conventional explosives and forming a crater on land owned by the University of New Mexico. The 1961 Goldsboro B-52 crash near Goldsboro, North Carolina, saw a Boeing Stratofortress carrying two Mark 39 nuclear bombs break up in mid-air, with one of the weapons going through every one of its stages of its firing sequence, save one safety switch. These events, often designated as Broken Arrow accidents, demonstrate that the avoidance of an unintended nuclear explosion was due less to correct implementation of controls and instead can be attributed to disobedience, technical failures, or other factors beyond strict human control. General George Lee Butler, commander of the US Strategic Air Command from 1991 to 1992, argued in 1999 that the world escaped the Cold War without a nuclear holocaust by some combination of skill, luck, and divine intervention.

Common questions

When did the first nuclear weapon detonation occur and who witnessed it?

The first nuclear weapon detonation occurred on the 16th of July 1945 at the Trinity Test Site in New Mexico. J. Robert Oppenheimer, the scientific director of the Manhattan Project, witnessed the event and later recalled a verse from the Hindu scripture Bhagavad Gita.

What were the dates and outcomes of the Hiroshima and Nagasaki bombings?

The United States Army Air Forces detonated the uranium gun-type fission bomb Little Boy over Hiroshima on the 6th of August 1945. Three days later on the 9th of August, the plutonium implosion-type fission bomb Fat Man was detonated over Nagasaki, causing injuries that resulted in the deaths of approximately 200,000 civilians and military personnel.

Who died from radiation exposure during the Demon Core experiments?

Harry Daghlian died 25 days later on the 15th of September 1945 and Louis Slotin died nine days later on the 30th of May 1946. Both physicists conducted experiments on a plutonium-gallium core at Los Alamos National Laboratory between the 21st of August 1945 and the 21st of May 1946 when human error caused the core to enter prompt criticality.

When was the largest nuclear weapon ever detonated and what was its yield?

The largest nuclear weapon ever detonated was the Tsar Bomba of the USSR on the 30th of October 1961. This three-stage weapon released an energy equivalent of over 50 megatons.

Which countries have detonated nuclear weapons and when did the total stockpile peak?

The United States, the Soviet Union succeeded as a nuclear power by Russia, the United Kingdom, France, China, India, Pakistan, and North Korea are the only countries known to have detonated nuclear weapons and acknowledge possessing them. The total from all stockpiles peaked at over 64,000 weapons in 1986.

What is the current time set on the Doomsday Clock and when was it last adjusted?

The Doomsday Clock was moved to 89 Seconds to midnight in 2025 following the escalation of nuclear threats during the Russo-Ukrainian war. The clock previously reached 90 seconds in 2023, which was the highest likelihood of global catastrophe since the existence of the Doomsday Clock.

The Fusion Leap

The evolution from fission to fusion weapons represented a quantum leap in destructive power, transforming the hydrogen bomb into the most powerful weapon ever created. All existing nuclear weapons derive some of their explosive energy from nuclear fission reactions, but the other basic type produces a large proportion of its energy in nuclear fusion reactions. Such fusion weapons are generally referred to as thermonuclear weapons or more colloquially as hydrogen bombs, as they rely on fusion reactions between isotopes of hydrogen, specifically deuterium and tritium. The Teller-Ulam design, which accounts for all multi-megaton yield hydrogen bombs, accomplishes this by placing a fission bomb and fusion fuel in proximity within a special, radiation-reflecting container. When the fission bomb is detonated, gamma rays and X-rays emitted first compress the fusion fuel, then heat it to thermonuclear temperatures. The ensuing fusion reaction creates enormous numbers of high-speed neutrons, which can then induce fission in materials not normally prone to it, such as depleted uranium. The largest nuclear weapon ever detonated, the Tsar Bomba of the USSR, released an energy equivalent of over 50 megatons on the 30th of October 1961, and was a three-stage weapon. In the early 1950s, the Livermore Laboratory in the United States had plans for the testing of two massive bombs, Gnomon and Sundial, with yields of 1 gigaton and 10 gigatons of TNT respectively, though these were never realized. Virtually all thermonuclear weapons deployed today use this two-stage design, but it is possible to add additional fusion stages, each igniting a larger amount of fusion fuel in the next stage. This technique can be used to construct thermonuclear weapons of arbitrarily large yield, in contrast to fission bombs, which are limited in their explosive power due to criticality danger. While fusion reactions do not create fission products and thus contribute far less to the creation of nuclear fallout than fission reactions, all thermonuclear weapons contain at least one fission stage, and many high-yield thermonuclear devices have a final fission stage, meaning they can generate at least as much nuclear fallout as fission-only weapons.

The Silent Pulse

Beyond the immediate blast and fire, nuclear weapons possess a unique capability to disable modern civilization without necessarily destroying the physical infrastructure. During the Starfish Prime high-altitude nuclear test in 1962, an unexpected effect was produced which is called a nuclear electromagnetic pulse. This is an intense flash of electromagnetic energy produced by a rain of high-energy electrons which in turn are produced by a nuclear bomb's gamma rays. This flash of energy can permanently destroy or disrupt electronic equipment if insufficiently shielded, creating a radar blackout and disabling military and civilian infrastructure over a wide, even continental, geographical area. Research has been done into the possibility of pure fusion bombs, nuclear weapons that consist of fusion reactions without requiring a fission bomb to initiate them, which would create significantly less nuclear fallout than other thermonuclear weapons. Antimatter, which consists of particles resembling ordinary matter particles in most of their properties but having opposite electric charge, has been considered as a trigger mechanism for nuclear weapons, though there is no evidence that it is feasible beyond the military domain. A fourth generation nuclear weapon design is related to, and relies upon, the same principle as antimatter-catalyzed nuclear pulse propulsion. The detonation of any nuclear weapon is accompanied by a blast of neutron radiation, and surrounding a nuclear weapon with suitable materials such as cobalt or gold creates a weapon known as a salted bomb. This device can produce exceptionally large quantities of long-lived radioactive contamination, and it has been conjectured that such a device could serve as a doomsday weapon because such a large quantity of radioactivities with half-lives of decades, lifted into the stratosphere where winds would distribute it around the globe, would make all life on the planet extinct. The Strategic Defense Initiative also saw research into the nuclear pumped laser under the DOD program Project Excalibur, which involved tapping the energy of an exploding nuclear bomb to power a single-shot laser directed at a distant target, though this did not result in a working weapon.

The Triad of Death

The design, development, and maintenance of delivery systems are among the most expensive parts of a nuclear weapons program, accounting for 57% of the financial resources spent by the United States on nuclear weapons projects since 1940. The simplest method for delivering a nuclear weapon is a gravity bomb dropped from aircraft, which was the method used by the United States against Japan in 1945, but this method places few restrictions on the size of the weapon while limiting attack range and response time. Preferable from a strategic point of view is a nuclear weapon mounted on a missile, which can use a ballistic trajectory to deliver the warhead over the horizon. The development of long-range intercontinental ballistic missiles and submarine-launched ballistic missiles has given some nations the ability to plausibly deliver missiles anywhere on the globe with a high likelihood of success. More advanced systems, such as multiple independently targetable reentry vehicles, can launch multiple warheads at different targets from one missile, reducing the chance of a successful missile defense. Today, missiles are most common among systems designed for delivery of nuclear weapons, and making a warhead small enough to fit onto a missile can be difficult. Tactical weapons have involved the most variety of delivery types, including not only gravity bombs and missiles but also artillery shells, land mines, and nuclear depth charges and torpedoes for anti-submarine warfare. An atomic mortar has been tested by the United States, and small, two-man portable tactical weapons, somewhat misleadingly referred to as suitcase bombs, have been developed, although the difficulty of combining sufficient yield with portability limits their military utility. Ballistic missile submarines have been of great strategic importance for the United States, Russia, and other nuclear powers since they entered service in the Cold War, as they can hide from reconnaissance satellites and fire their nuclear weapons with virtual impunity. The Soviet OTR-21 Tochka missile, for example, is capable of firing a 100-kiloton nuclear warhead a distance of 185 km, while the Russian Strategic Rocket Forces R-36 ICBM, also known by the NATO reporting name SS-18 Satan, remains the single highest throw weight missile delivery system ever built.

The Deterrence Paradox

Nuclear warfare strategy is a set of policies that deal with preventing or fighting a nuclear war, with the policy of trying to prevent an attack by a nuclear weapon from another country by threatening nuclear retaliation known as the strategy of nuclear deterrence. The goal in deterrence is to always maintain a second strike capability, the ability of a country to respond to a nuclear attack with one of its own, and potentially to strive for first strike status, the ability to destroy an enemy's nuclear forces before they could retaliate. During the Cold War, policy and military theorists considered the sorts of policies that might prevent a nuclear attack, and they developed game theory models that could lead to stable deterrence conditions. Critics of nuclear war strategy often suggest that a nuclear war between two nations would result in mutual annihilation, and the significance of nuclear weapons is to deter war because any nuclear war would escalate out of mutual distrust and fear, resulting in mutually assured destruction. In the late 1950s and early 1960s, Gen. Pierre Marie Gallois of France, an adviser to Charles de Gaulle, argued in books like The Balance of Terror: Strategy for the Nuclear Age that mere possession of a nuclear arsenal was enough to ensure deterrence, and thus concluded that the spread of nuclear weapons could increase international stability. Some prominent neo-realist scholars, such as Kenneth Waltz and John Mearsheimer, have argued that some forms of nuclear proliferation would decrease the likelihood of total war, especially in troubled regions of the world where there exists a single nuclear-weapon state. The threat of potentially suicidal terrorists possessing nuclear weapons complicates the decision process, as the prospect of mutually assured destruction might not deter an enemy who expects to die in the confrontation. Since 1996, the United States has had a policy of allowing the targeting of its nuclear weapons at terrorists armed with weapons of mass destruction, and the integration of nuclear weapons employment with conventional and special operations forces is essential to the success of any mission or operation.

The Global Stockpile

As of 2024, there are nine countries on the list of states with nuclear weapons, and six more agree to nuclear sharing, with roughly 40 countries having defense policies linked to nuclear armament through NATO membership or agreements with other nuclear powers. The total from all stockpiles peaked at over 64,000 weapons in 1986, and is around 9,600 today. The only countries known to have detonated nuclear weapons and acknowledge possessing them are, chronologically by date of first test, the United States, the Soviet Union succeeded as a nuclear power by Russia, the United Kingdom, France, China, India, Pakistan, and North Korea. Israel is believed to possess nuclear weapons, though, in a policy of deliberate ambiguity, it does not acknowledge having them. South Africa is the only country to have independently developed and then renounced and dismantled its nuclear weapons. The former Soviet republics of Belarus, Kazakhstan, and Ukraine returned Soviet nuclear arms stationed in their countries to Russia after the collapse of the USSR. In 1981, Israel had bombed a nuclear reactor being constructed in Osirak, Iraq, in what it called an attempt to halt Iraq's previous nuclear arms ambitions, and in 2007, Israel bombed another reactor being constructed in Syria. As of early 2019, more than 90% of world's 13,865 nuclear weapons were owned by Russia and the United States. China is significantly expanding its nuclear arsenal, with projections of over 1,000 warheads by 2030 and up to 1,500 by 2035. North Korea is progressing in intercontinental ballistic missile tests and has a mutual-defense treaty with Russia, exchanging artillery for possible missile technology. Iran is currently viewed as a nuclear threshold state, and on the 30th of October 2025, US President Donald Trump called for renewed nuclear weapons testing in order to keep pace with other nuclear armed states such as Russia and China, though it was not specified whether he referred to nuclear explosive testing or testing of delivery systems for nuclear warheads.

The Doomsday Clock

The Doomsday Clock measures the likelihood of a human-made global catastrophe and is published annually by the Bulletin of the Atomic Scientists, with the two years with the highest likelihood having previously been 1953, when the Clock was set to two minutes until midnight after the US and the Soviet Union began testing hydrogen bombs, and 2018, following the failure of world leaders to address tensions relating to nuclear weapons and climate change issues. In 2023, following the escalation of nuclear threats during the Russo-Ukrainian war, the doomsday clock was set to 90 seconds, the highest likelihood of global catastrophe since the existence of the Doomsday Clock. Given the lack of progress towards peace in Ukraine, the Doomsday Clock was moved to 89 Seconds to midnight in 2025. As of 2024, Russia has intensified nuclear threats in Ukraine and is reportedly planning to place nuclear weapons in orbit, breaching the 1967 Outer Space Treaty. The Russell-Einstein Manifesto was issued in London on the 9th of July 1955, by Bertrand Russell in the midst of the Cold War, highlighting the dangers posed by nuclear weapons and calling for world leaders to seek peaceful resolutions to international conflict. The signatories included eleven pre-eminent intellectuals and scientists, including Albert Einstein, who signed it just days before his death on the 18th of April 1955. A few days after the release, philanthropist Cyrus S. Eaton offered to sponsor a conference called for in the manifesto in Pugwash, Nova Scotia, which was to be the first of the Pugwash Conferences on Science and World Affairs, held in July 1957. In 1962, Linus Pauling won the Nobel Peace Prize for his work to stop the atmospheric testing of nuclear weapons, and the Ban the Bomb movement spread. In 1963, many countries ratified the Partial Test Ban Treaty prohibiting atmospheric nuclear testing, and radioactive fallout became less of an issue. In 1996, many nations signed the Comprehensive Nuclear-Test-Ban Treaty, which prohibits all testing of nuclear weapons, and a testing ban imposes a significant hindrance to nuclear arms development by any complying country. The Treaty requires the ratification by 44 specific states before it can go into force, and as of 2025, the ratification of eight of these states is still required. In 2017, 122 countries mainly in the Global South voted in favor of adopting the Treaty on the Prohibition of Nuclear Weapons, which eventually entered into force in 2021, and the International Court of Justice issued an Advisory Opinion in 1996 concerned with the Legality of the Threat or Use of Nuclear Weapons, ruling that the use or threat of use of nuclear weapons would violate various articles of international law.