Beyond the Button: The Nerve-Wracking Reality of Oppenheimer's Atomic Experiment

In perhaps one of the most pivotal scenes from Oppenheimer, the movie about the making of the atomic bomb, frontrunner at the upcoming Oscars, scoring a grand 13 nominations, Major General Leslie Groves (Matt Damon) asks Manhattan Project leader J Robert Oppenheimer (Cillian Murphy): “Are we saying there’s a chance that when we push that button we destroy the world?”

The chance, Oppenheimer assures him, is “near zero.”

Groves is not wholly assuaged. “Near zero?” Oppenheimer, frustrated, asks what answer he wanted to hear.

Groves, of course, speaks for the audience: “Zero would be nice!”

In reality, Groves's apprehensions mirrored those of Manhattan Project physicist Edward Teller. Dr. Steven Biegalski, Chair of Nuclear and Radiological Engineering at the Georgia Institute of Technology, explains Teller's concern that the explosion's heat could induce hydrogen fusion in the atmosphere, triggering a catastrophic chain reaction with the potential to destroy Earth, essentially setting the world ablaze.

Contrary to the belief that fears of the first atomic bomb destroying the world were fabricated for cinematic tension, some scientists involved in its development genuinely harboured concerns. In 1942, Teller, later the inventor of the more powerful hydrogen bomb, presented the idea that an atomic explosion could generate temperatures hotter than the sun, possibly creating conditions for poorly understood fusion reactions to occur.

The bottom line: there was a tangible risk of igniting the atmosphere, posing a threat to everything dependent on it. Teller's presentation sparked controversy, with some physicists vehemently rejecting the possibility while others, with notable pedigrees, were less convinced it could be unequivocally ruled out, given the incomplete understanding of nuclear reactions.

A secret report commissioned by the Manhattan Project deemed the scenario "unlikely," assuaging many fears. However, not all concerns were dispelled, leading scientists to reevaluate their calculations up to the test day. Nobel Prize-winning physicist Arthur Compton, expressing uncertainty, even proposed, mostly in jest, placing bets on the destruction of life on Earth moments before the Trinity test.

James Conant, then-president of Harvard University and a witness to the Trinity test, later recounted that the unexpectedly brighter and longer-lasting flash from the test made him instantly believe they had ignited the atmosphere, dooming the world.

While current knowledge affirms that nuclear bombs cannot ignite the atmosphere, existential risk researcher Toby Ord argues in his book "The Precipice" that the 1940s team couldn't have been entirely confident in their conclusions. The geopolitical competition with the Nazis drove the Manhattan Project scientists, as the logic dictated that getting the bomb first was crucial to prevent Hitler from holding the world hostage.

Initiated with the conviction that the Nazis were close to completing an atomic bomb, it became evident by the time of the Trinity test in July 1945 that Germany had already surrendered. The justification for risking the fate of every person alive diminished months before the Trinity countdown began.

Shortly after Franklin Roosevelt’s death in April 1945, new President Harry Truman was briefed for the first time on the bomb. He wrote later that FDR’s close adviser Jimmy Byrnes told him they “were perfecting an explosive great enough to destroy the whole world.” And also, of course, “the bomb might well put us in a position to dictate our own terms at the end of the war.”

The question remains: how big and destructive can nuclear weapons get? Could a single bomb feasibly end the world?

“The bomb dropped on Hiroshima during World War Two was 15 kilotons, equivalent to 15,000 tonnes of TNT,” explains Dr Tara Drozdenko, a director of the Global Security Program at the Union of Concerned Scientists.

“The Nagasaki bomb was 20 kilotons. Most current US nuclear weapons are 15 to 20 times more powerful than those bombs."

For context, the Hiroshima bomb devastated 13km2 of the city, destroyed 63 per cent of its buildings and killed at least 70,000 people. But the most powerful nuclear bomb ever made was tested by the Soviet Union in 1961. Named Tsar Bomba, it had a yield of over 50,000 kilotons, which is equivalent to 50 million tonnes of TNT.

The blast was monstrous, destroying houses in the village of Severny, 55 kilometres (34 miles) from the testing site at Mityushikha Bay. If such a bomb were dropped on Manchester, people in Liverpool, Leeds and Sheffield would suffer third-degree burns.

Incredibly, Tsar Bomba was designed to be twice as powerful (100 megatons), but was scaled back to mitigate radiation effects. There is even speculation that in the future bombs like the Tsar Bomba could be used to knock an asteroid off course.

Dr Tara Drozdenko of the Union of Concerned Scientists notes the impracticality of extremely powerful bombs like the Tsar Bomba due to the lack of a practical delivery system. While there is a general consensus that fission-fusion weapons can achieve higher yields than Tsar Bomba, the theoretical maximum size's potential to destroy the world remains uncertain, leaving an open-ended question. Biegalski emphasizes the uncertainty, expressing the hope that humanity never reaches such extremes.