Ask a Scientist: Scientists and Arms Control from Oppenheimer to Today

July 13, 2023 | 12:44 pm
Photo of Oppenheimer in a fedora and suitNBC News Studios
Elliott Negin
Senior Writer

Read more of UCS’s critical analysis of Oppenheimer and the global security issues it examines here.

On July 21, Oppenheimer, a new major motion picture chronicling the life and legacy of J. Robert Oppenheimer, the father of the atomic bomb, will open in theaters across the country. Written and directed by Christopher Nolan, director of Dunkirk, Interstellar and The Dark Knight trilogy, the film was inspired by the Pulitzer Prize-winning book American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer by Kai Bird and Martin J. Sherwin. (In a run-up to the film, NBC News produced a documentary on Oppenheimer that aired on July 9 on MSNBC and is now streaming on Peacock.)

“What I wanted to do was take the audience into the mind and the experience of a person who sat at the absolute center of the largest shift in history,” Nolan said in a Universal Pictures press release. “Like it or not, J. Robert Oppenheimer is the most important person who ever lived.”

I can’t say that Oppenheimer—or anyone else for that matter—could be considered the most important person who ever lived, but there is no doubt that he, as well as the hundreds of other Manhattan Project scientists at Los Alamos he led, changed the world irrevocably. Ever since they detonated the first nuclear device on July 16, 1945, all of humanity, as President Kennedy pointed out in a speech before the United Nations General Assembly 16 years later, has been living “under a nuclear sword of Damocles, hanging by the slenderest of threads, capable of being cut at any moment by accident or miscalculation or by madness.”

Some Manhattan Project scientists tried to stop President Truman from dropping the atomic bomb on Japan in the first place. Afterward, many of them—including Oppenheimer—wrestled with civilian and military officials to try to restrain an arms race they predicted would happen. They campaigned against proliferation, for stricter arms control, and even for eventual disarmament. Sometimes they were successful in setting—or at least influencing—the political agenda. More often, they were not.

Bird, whose book was first published in 2005, would like the film to jumpstart a public discussion about the issues Oppenheimer grappled with, issues that are still very much with us today.

“I have hopes it will actually stimulate a national, even global conversation about the issues that Oppenheimer was desperate to speak out about,” Bird said during a mid-May seminar at Princeton’s Institute for Advanced Study, where Oppenheimer served as director from 1947 to 1966. “About how to live in the atomic age, how to live with the bomb and about McCarthyism. What it means to be a patriot, and what is the role for a scientist in a society drenched with technology and science to speak out about public issues.”

The Union of Concerned Scientists (UCS) has been deeply engaged in the same issues ever since its founding in the spring of 1969. The fledgling organization’s very first reports were on ballistic missile defense and multiple warhead missiles, and over the last 54 years, UCS scientists have been in the thick of the national debate over nuclear weapons and arms control.

Given the upcoming debut of Oppenheimer, I wanted to explore the role that physicists and other scientists have played since World War II in shaping national—and international—nuclear policy with Dylan Spaulding, a senior scientist in the UCS Global Security Program. Spaulding has an undergraduate degree in physics from Brown University and a doctorate degree in Earth and Planetary Sciences from the University of California, Berkeley, where Oppenheimer taught from 1929 to 1943. Among other positions before joining the UCS staff last year, he was a stockpile stewardship graduate fellow at the Lawrence Livermore National Laboratory and spent time at the Los Alamos National Laboratory and Sandia National Laboratories, where he gained familiarity with the US nuclear weapons complex and the science of weapons development.

EN: By May 1945, it was a foregone conclusion that the United States would drop the atomic bomb on Japan. But at least one Manhattan Project scientist—Leo Szilard—tried unsuccessfully to convince President Truman to abandon plans to use the weapon, and he and a number of his colleagues warned policymakers that using the bomb would trigger an arms race with the Soviet Union. They recommended that the United States demonstrate what they called the “gadget” before United Nations representatives at an uninhabited site. Where was Oppenheimer on this issue?

DS: As Kai Bird and Martin Sherwin point out in American Prometheus, J. Robert Oppenheimer’s position was complicated. Most of the scientists at Los Alamos had been working fervently to stop Nazi Germany, which they feared would develop an atomic bomb first, but the war in Europe ended just before the US bomb was ready. Many key Manhattan Project scientists, including Oppenheimer, were Jewish, and—unlike Oppenheimer, who was born in the United States—many were refugees from Europe. After Germany unconditionally surrendered in May 1945, some of the scientists began to question the value of continuing, possibly because their sense of urgency had ebbed. That wasn’t as true for Oppenheimer, who apparently was caught between his deep devotion to the science, his personal convictions, and his role as project leader. At the time, he was reluctant to acknowledge that scientists have a unique responsibility when it comes to arms control, although he recognized that the weapon they had designed would fundamentally change the nature of war. In fact, he thought it could put an end to all war.

At the same time, he was wary of the debate among his Los Alamos colleagues about the implications of their work. He insisted that scientists were no more qualified than anyone else to determine the use of atomic power and that politics was not their first responsibility. Ultimately, he signed off on a report by an advisory committee to Secretary of War Henry Stimson that concluded that it could “propose no technical demonstration likely to bring an end to the war” in Japan and saw “no acceptable alternative to direct military use.”

By contrast, Leo Szilard was alarmed when the Truman administration’s intentions for using the weapon became clearer. Along with James Franck, Glenn Seaborg and other Manhattan Project scientists, he issued what became known as the Franck Report, an especially prescient document that recommended demonstrating the bomb before international observers in an unpopulated area. The report warned that using the bomb without a prior international agreement on controlling atomic energy would spark a runaway arms race and that dropping it unannounced on a civilian population would sacrifice any possibility of the United States being able to provide moral leadership on nuclear issues. Szilard followed the report with a petition to Truman signed by more than 70 Manhattan Project scientists calling for restraint and granting the Japanese the opportunity to surrender first. Oppenheimer did not take Szilard’s efforts kindly and did not circulate the petition at Los Alamos. It never got to Truman.

It is clear that Oppenheimer was deeply transformed after the war, particularly when his Manhattan Project protégé, Robert Serber, returned to Los Alamos after participating in the first US delegation to Hiroshima with a first-hand account of the horrific atrocities on the ground. Oppenheimer, who had previously been appalled that there were no protests over the US firebombing of Tokyo, now found himself identified in the daily news as the architect of an even more massive barbarity.

After the war, Oppenheimer did help shape some of the first US arms control proposals. In 1946, for example, he coauthored the Acheson-Lilienthal report, one of the first attempts to design a system of international control over atomic energy. After the Truman administration established the Atomic Energy Commission (AEC), which placed atomic energy under civilian supervision, Oppenheimer became chair of the AEC’s General Advisory Committee (GAC), which kept him in the middle of the political and ethical debates over nuclear weapons in the post-war years.

EN: When the Soviet Union exploded its first atomic bomb in August 1949, it prompted the Truman administration to dramatically increase the number of nuclear weapons in the US stockpile from around 50 to some 300 by June 1950. It also ignited a crash program to develop the “Super,” a thermonuclear hydrogen bomb, 1,000 times more lethal than the bomb dropped on Hiroshima. How did Oppenheimer and other Manhattan Project scientists react to that?

DS: It wasn’t a surprise for most of the Manhattan Project scientists that the Soviets were able to develop their own bomb. Spies at Los Alamos had provided the Soviet Union background on the project well before the United States dropped the bombs on Japan. In fact, when Truman told Soviet leader Joseph Stalin at the Potsdam conference in late July 1945 that the United States had a new weapon of unusual destructive force,” Stalin may have known more about it than Truman! Detonating the bomb demonstrated the science. Afterward, it was merely an engineering problem for other countries to replicate.

The idea of a “super” bomb had been actively promoted by another physicist at Los Alamos, Edward Teller, much to Oppenheimer’s dismay. He saw it as unnecessarily complicated and possibly unfeasible, but Teller essentially refused to work on anything else. When the idea resurfaced in 1949, Teller jumped at the chance to recruit scientists back to Los Alamos to work on it.

Oppenheimer, who then chaired the GAC, opposed building this even more lethal and indiscriminate weapon. He felt that such a large bomb served no military purpose, was morally repugnant, and instead recommended that the United States develop smaller, “tactical” nuclear weapons that could be used on the battlefield.

Oppenheimer’s vehement opposition to the hydrogen bomb was a major factor leading to his prosecution in early 1950s during Sen. Joseph McCarthy’s Red Scare campaign and ultimately the revocation of his security clearance. Teller was a key witness against him in government hearings.

Oppenheimer and his allies obviously lost the debate over the hydrogen bomb. Today, most of the US nuclear arsenal is made up of thermonuclear weapons that have yields ranging from 10 to 80 times larger than the Hiroshima bomb.

EN: Regardless, physicists have played a pivotal role in arms control since then. A notable example happened in the 1980s, when US and Soviet scientists worked together to show that a nuclear test ban treaty could be verified. What can you tell us about that extraordinary effort?

DS: Between 1945 and 1992, the United States and Russia collectively conducted 1,745 tests in the atmosphere and underground. The seven other confirmed nuclear states conducted 311 tests until 1998, with North Korea being the only state that has tested since then. Because tests were critical for nuclear weapons development throughout the Cold War, antinuclear advocates saw some form of nuclear test ban as the best way to stop the arms race and limit proliferation. Progress came in fits and starts, but it was ultimately thanks to the scientists who demonstrated the technical means to verify a test ban treaty that the political stalemate could be overcome.

The earliest attempts to limit testing began in the late 1950s, resulting in a temporary moratorium and then a partial test ban in 1963 during the Kennedy administration that ended testing in the atmosphere, oceans, and space. The partial test ban treaty was largely due to growing public awareness of the threat posed by radioactive fallout as well as the sobering experience of the Cuban Missile Crisis, when the United States and the Soviet Union narrowly averted a nuclear exchange. But it also was at least partly due to efforts by US chemist Linus Pauling, who received the Nobel Peace Prize in 1962 for raising awareness of the dangers of atmospheric testing as well as organizing a petition calling for an end to testing signed by more than 11,000 scientists around the world.

The very real concern that nations could secretly continue to conduct underground tests would prove to be an obstacle to further progress until the 1980s, when Soviet President Mikhail Gorbachev’s policy of glasnost, or openness, allowed US and Soviet scientists to talk directly with each other. Princeton physicist Frank von Hippel and Jeremy Stone, president of the Federation of American Scientists, organized arms control workshops and joint studies with Soviet physicists, including Roald Sagdeev, Evgeny Velikhov and others associated with the Soviet Academy of Sciences. At one such meeting in Moscow in 1986, Thomas Cochran, a physicist with the Natural Resources Defense Council, proposed that US and Soviet scientists work together to seismically monitor US and Soviet test sites. Velikhov and his team accepted Cochran’s proposal, and the resulting project showed that advanced seismometers could detect even small tests and distinguish them from large chemical explosions and natural seismic activity. Their demonstration provided a viable way to verify an underground test ban and countered government claims that such a treaty could not be enforced.

That joint US-Soviet project remains a prime example of what can be accomplished by multilateral scientific collaboration. It took another decade, but in September 1996, the United Nations adopted the Comprehensive Test Ban Treaty (CTBT). All five official nuclear weapons states—China, France, Russia, the United Kingdom and the United States—as well as 66 other nations signed the treaty that day. (While abiding by the treaty, neither China nor the United States have officially ratified it.) Today, the CTBT Organization maintains an impressive array of seismic stations, infrasound atmospheric sensors, submarine hydroacoustic sensors and radionuclide monitors spanning the globe to detect nuclear tests anywhere they might occur.

EN: In 1983, President Reagan gave his famous “Star Wars” speech calling for scientists to develop a “space shield” that would render “nuclear weapons impotent and obsolete.” The US scientific community, including physicists at the Union of Concerned Scientists (UCS), warned that the Strategic Defense Initiative (SDI) to put an anti-ballistic-missile-defense system in space would not work. Tell us about the role scientists have played over the last four decades to try to kill what has amounted to a zombie program that won’t die.

DS: The idea of an impenetrable shield against nuclear weapons, whether space-based or ground-based anti-ballistic missiles, is innately attractive, and would be preferable to basing national security on the concept of mutually assured destruction. In reality, however, a viable anti-ballistic missile defense system would likely spur an adversary to build more offensive missiles and, in any case, missile defense has proven to be ineffective, expensive, and technically vulnerable.

Ronald Reagan’s original notion of a space-based system was enthusiastically championed by some scientists, particularly Edward Teller, but UCS and other scientific organizations have demonstrated how impractical and dangerous these proposals are.

A year after Reagan proposed the SDI system, UCS founders Kurt Gottfried and Henry Kendall—along with Manhattan Project physicist Hans Bethe and physicist Richard Garwin, a longtime UCS board member—coauthored The Fallacy of Star Wars, a book that showed that the system was based on a nonexistent technology and would require considerably more satellites than its proponents suggested. Potentially costing billions of dollars apiece, the satellites would be much more vulnerable than the missiles they were supposed to defeat. Their assessment was seconded a few years later by scientists at the American Physical Society, who published a similarly scathing appraisal of SDI’s technical challenges and feasibility.

Around the same time, physicists Lisbeth Gronlund and David Wright, who later served as codirectors of the UCS Global Security Program (GSP) from 2002 to 2020, circulated a pledge signed by more than 7,000 scientists who vowed they would not accept SDI-related funding. The campaign generated headlines across the country, drawing public attention to the scientific community’s strong opposition to Reagan’s plan.

These efforts mounted technical, as well as moral, challenges to the Star Wars program and highlighted the folly behind it. They remain a shining example of how scientists can best use their expertise to debunk bad—and dangerous—government policy, showing that there is no technical solution to protect people from nuclear weapons. The real solution is political and diplomatic.

EN: The myth of a viable Star Wars program became even more problematic when the George W. Bush administration abandoned the 1972 Anti-Ballistic Missile (ABM) Treaty with the Russians in 2002. UCS scientists were able to show that an anti-ballistic missile defense system could be easily defeated.

DS: That’s right. The idea behind limiting defensive weapons under the ABM Treaty was to support nuclear arms reductions by discouraging an offense-defense arms race. The ABM Treaty strictly limited the amount of missile defenses each party could field. Eventually the unrealistic dream of a space-based missile defense system came down to earth, and the Pentagon focused on ground-based interceptors to target nuclear-armed missiles during their long coast through space, the midcourse phase of flight.

In 2000, the last full year of the Clinton administration, UCS scientists published another study, this time in collaboration with scientists from the Massachusetts Institute of Technology and elsewhere. The study, Countermeasures, showed just how easily the proposed national missile defense system could be defeated using technologies available to any state capable of launching a nuclear-armed ballistic missile.

Nevertheless, within its first weeks in office, the George W. Bush administration signaled an interest in withdrawing from the ABM Treaty. Following the September 11, 2001, terrorist attacks, the administration announced it was indeed doing so and planned to accelerate the development of a Ground-based Midcourse Defense (GMD) system against possible missile threats from Iran, Iraq, and North Korea. It was a decidedly pared down version of what Edward Teller and Ronald Reagan had envisioned, but it was equally misguided.

The Pentagon pursued the GMD system with multibillion-dollar budgets and little oversight, and repeatedly claimed the system was highly effective and would provide significant protection. UCS scientists and other experts pushed back against this fanciful narrative with analyses showing that the system is ineffective, costly, and destabilizing. For more specifics, I highly recommend checking out a 2016 report by UCS Global Security Research Director Laura Grego, which provides a good, relatively up-to-date analysis of the GMD system’s technical and administrative deficiencies.

Without a doubt, abandoning the ABM Treaty and spending billions on missile defense has undermined US security. In March 2018, Russian President Vladimir Putin specifically cited the US withdrawal from the ABM Treaty as the reason why Russia is now developing new “super weapons,” including hypersonic nuclear delivery systems. China is following suit, prompting the United States to respond to this new “threat” by developing its own hypersonic weapons as well as modernizing every leg of its nuclear arsenal.

EN: In a 2020 report, UCS scientists made a convincing case for retiring US land-based intercontinental ballistic missiles (ICBMs). A year later, they punctured the hype over hypersonic weapons. Are US policymakers paying any attention?

DS: Unfortunately, they are paying more attention to the perceived threat that I just mentioned—a new “trilateral” cold war. And, at the same time, they are ignoring the way in which US actions are driving a new arms race.

The 400 land-based ICBMs scattered across the northern Great Plains states are immobile, their positions are well-known, and their main purpose is to “absorb” a nuclear attack from Russia, acting as a giant “nuclear sponge.” As then GSP co-directors Wright and Gronlund and their coauthor William Hartung pointed out in their 2020 report, Russian missiles could reach them within a half hour, giving a president 10 minutes or less to decide whether to launch them before they are destroyed by a perceived attack. That increases the possibility of mistaken nuclear war triggered by a false attack warning, and there have been a number of close calls over the last six decades due to human and technological errors.

ICBMs are not only dangerous, they are an unnecessary relic of cold war strategy. They may have made sense 60 years ago, when they were more accurate and powerful than submarine-launched ballistic missiles and when communications links with subs were unreliable. Since then, the accuracy of sub-launched missiles has increased dramatically, and the Navy has secure submarine communication links, making the ICBMs superfluous.

If ICBMs are now passé, hypersonic weapons are now all the rage—with no scientific justification. A 2021 analysis by Wright and UCS Kendall Fellow Cameron Tracy found that hypersonic weapons fail to live up to the glowing claims made about them. Despite what their name suggests, they are not faster than conventional missiles, nor are they stealthier or harder to detect. Regardless, as I mentioned earlier, hypersonics have triggered a high-tech arms race with Russia and China because US policymakers mistakenly see them as cutting-edge technology.

In many ways, hypersonics are yet another example of illogical cold war thinking that goes like this: If our adversary has them, we have to have them too, even if we’re not quite sure why.