Questions: Nuclear Weapons: Physics, Policy, and Existential Risk

Question 1

What is 'mutually assured destruction' (MAD), and what was its role in Cold War deterrence strategy?

Model answer: Mutually Assured Destruction was the doctrine, dominant in US-Soviet nuclear strategy from roughly the 1960s, that each superpower maintained nuclear forces sufficient to survive a first strike and retaliate with devastating effect — ensuring any nuclear war would result in both sides' annihilation. The logic was that neither side could rationally initiate nuclear war knowing it would be destroyed in return. MAD required that neither side attempt a disarming first strike, which required survivable second-strike forces (submarine-launched missiles, dispersed land-based missiles). The stability of MAD depended on both sides accepting mutual vulnerability — a counterintuitive strategy that required deliberately not defending against enemy missiles.

MAD was explicitly argued as stabilizing by Robert McNamara and others: if defense was impossible, neither side would gain from striking first. The doctrine was contested by those who wanted missile defense and those who found it morally intolerable to base peace on the threat of mass annihilation.

Question 2

The Cuban Missile Crisis (October 1962) brought the US and USSR to the brink of nuclear war. What happened, and how was it resolved?

Model answer: In October 1962, US reconnaissance photographs revealed Soviet nuclear missiles being installed in Cuba — 90 miles from Florida. President Kennedy imposed a naval 'quarantine' (blockade) of Cuba and demanded the missiles' removal. The crisis lasted 13 days. Unknown to US officials at the time, a Soviet submarine in the Caribbean, harassed by US depth charges, came close to launching a nuclear torpedo — averted when officer Vasili Arkhipov refused to authorize the launch. Resolution came through secret negotiations: the USSR removed its Cuban missiles; the US pledged not to invade Cuba and (secretly) agreed to remove Jupiter missiles from Turkey. The crisis directly led to the 'hotline' between Washington and Moscow.

Recently declassified documents have revealed how much closer to accidental nuclear war the crisis came than was publicly known. Vasili Arkhipov's refusal to authorize the torpedo launch may have prevented nuclear war.

Question 3

The first nuclear weapon test, Trinity, was conducted on July 16, 1945. What was J. Robert Oppenheimer's reported reaction?

• A. He celebrated the successful test with champagne and declared the war would be over within weeks
• B. He recalled a line from the Bhagavad Gita: 'Now I am become Death, the destroyer of worlds'
• C. He immediately resigned from the Manhattan Project and refused to work on the hydrogen bomb
• D. He filed a classified report arguing the weapon should not be used against civilian populations

Answer: (B)

Oppenheimer recalled the line from the Hindu scripture: 'Now I am become Death, the destroyer of worlds' (Vishnu's words in the Bhagavad Gita). He reported this reaction years later in a 1965 television interview. The quote has become one of the 20th century's most famous statements about scientific responsibility and the relationship between knowledge and power. Oppenheimer's moral ambivalence about the bomb he helped build was characteristic of many Manhattan Project scientists.

Question 4

Nuclear weapons have been used in war twice — at Hiroshima and Nagasaki in 1945. No nuclear weapon has been used in conflict since.

• T. True
• F. False

Answer: True

As of 2025, nuclear weapons have only been used in warfare twice, both in August 1945 against Japan. The subsequent 80-year non-use represents a 'nuclear taboo' — a strong normative prohibition against nuclear weapons use that has held even in conflicts where nuclear-armed states were directly involved (Korean War, Vietnam War) or where non-nuclear states faced nuclear states. Whether this reflects deterrence theory, political norms, or luck is debated. The taboo has become increasingly stressed as more states acquire nuclear weapons and as tactical nuclear weapons doctrine has been discussed.

Question 5

To what extent are scientists morally responsible for the applications of their research?

Model answer: This question has been debated since Hiroshima without resolution. Arguments for scientist responsibility: scientists understand the applications of their work better than anyone; they choose to work on military-funded or weapons-applicable research; they could refuse or advocate for different uses. Arguments against full responsibility: scientists cannot control applications of knowledge once published; political and military authorities make deployment decisions; the benefits of basic research (medical, economic) are diffuse and unpredictable. A middle position holds that scientists bear greater responsibility as applications become more foreseeable and specific: basic physics research differs from designing a delivery system for a nuclear warhead. The nuclear physicists' postwar activism (Bulletin of the Atomic Scientists, Pugwash Conferences) reflects their own sense of partial responsibility.

The Manhattan Project case is the paradigm example for debates about scientific responsibility. Various frameworks — consequentialist (outcomes matter), deontological (certain research violates duties), virtue ethics (what kind of scientist should one be) — give different answers.