The Science Behind Oppenheimer’s Atomic Bombs

An explanation of the two methods Oppenheimer used to create the revolutionary atomic bomb

“Prometheus stole fire from the gods and gave it to man. For this, he was chained to a rock and tortured for eternity.” This quote is displayed in the opening scene of Oppenheimer, the 2023 blockbuster film directed by Christopher Nolan (1). While it may initially seem like an outlandish comparison, Oppenheimer’s relation to Prometheus is quite accurate: they both gave humans a new deadly weapon that sparked violence, death, and innovation. In fact, Prometheus’ gift of fire was nothing compared to the deadliness of Oppenheimer’s atomic bomb. You may be wondering, what was so special about Oppenheimer’s discoveries that earned him such a bold comparison? 

J. Robert Oppenheimer was a physicist specializing in theoretical physics throughout his life (2). When World War II began, the United States government decided to assemble a group of scientists to develop an atomic bomb before the Nazis did. Oppenheimer had already been considering the possibility of such a bomb, so he began working for the United States at a laboratory in Los Alamos, New Mexico (3). 

Oppenheimer realized that specific isotopes, atoms with varying numbers of neutrons, of uranium and plutonium were able to split into multiple pieces, releasing energy through the process of fission. When uranium-235 or plutonium-239 (specific isotopes with 143 and 145 neutrons, respectively) are struck by a neutron, their nuclei split into two parts, releasing large amounts of energy and more neutrons in the process (4). The expelled neutrons shoot toward other nuclei and cause a chain reaction of more fission (4). The released energy is what causes the massive explosions to occur. The famous equation, e=mc2, states that matter can theoretically be converted into large amounts of energy, and the atomic bomb is an attempt to convert as much of that potential energy as possible (5).

A visual explanation of how the two atomic bomb contraptions work (2)

Gathering enough resources to create an atomic bomb is not an easy task. Uranium has to be mined and gathered, and only a small portion can undergo fission, as the uranium-235 isotopes account for less than one percent of all uranium on Earth (4). Once a large amount of uranium is collected, it undergoes a special process in a centrifuge, isolating the 235 isotopes from the rest (4). Plutonium is also difficult to gather. It is occasionally found within the earth, but it can also be produced artificially by manipulating other elements (4). For the bombs to explode, the scientists needed to gather enough materials to reach a critical mass. A critical mass is when enough fissionable material creates a chain reaction where neutrons keep hitting nuclei to split them up and cause an explosion (4). In Oppenheimer, there was a repeated reference to filling jars of marbles (1). These jars were representations of the amounts of uranium-235 and plutonium-239 that were being produced and brought to Los Alamos. This slow process was ongoing throughout a large portion of the film, signifying the challenge of collecting this material.

During the process of researching the bombs, Oppenheimer considered the possibility of lighting the entire world on fire as a result of igniting an atomic bomb, killing all humanity in the process. He thought the heat from the bombs might cause the nitrogen in the air to fuse and release energy, setting the entire world aflame. However, he decided that the odds of this occurring were too low and continued working on his bomb (6). 

At Los Alamos, the scientists developed two types of bombs. One was a gun-type bomb that shot two pieces of uranium together, and the other was a spherical bomb that imploded a piece of plutonium. The implosion method needed to be studied more, so the scientists at Los Alamos put together a test bomb, called Trinity (7). This bomb was the main focus of the Oppenheimer film, causing the big explosion at the movie’s climax (1). 

A picture of the explosion caused by the Trinity test in Los Alamos (1)

The gun-type bomb works by colliding two pieces of uranium-235 large enough to create a critical mass (5). The collision starts a chain reaction where the uranium nuclei split and shoot neutrons at other nuclei, repeating until there are no longer nuclei to collide and resulting in massive explosions. 

The implosion method works by imploding a spherical shell onto a piece of plutonium to create a critical mass more optimally (8). Since the plutonium keeps getting smaller, the nuclei get pushed closer together and are more likely to collide with neutrons to cause fission (8). This implosion makes the bomb more effective and more complete. 

The United States used the gun-type atomic bomb to create a bomb named Little Boy and dropped it on Hiroshima, Japan, on August 6, 1945 (9). The implosion method was used to create a bomb, dropped on Nagasaki 3 days later, called Fat Man (9). Oppenheimer’s discoveries paved the way for the nuclear era of war. His bombs killed hundreds of thousands of people and ended the Second World War (9). While his scientific discoveries were groundbreaking and innovative, they opened the door to the possibility of more violence and death. As Oppenheimer himself said: “Now I am become Death, the destroyer of worlds” (1). Being the creator of such a powerful bomb is a difficult position to hold; he is the reason for so much destruction in the world. Regardless, Oppenheimer was a unique scientist who turned theoretical science into reality. His legacy has stuck with the entire world, inspiring others to research nuclear energy. He will forever be known as an impactful scientist whose discoveries expanded the possibilities of warfare. 


  1. Nolan, C. (Director). (2023). Oppenheimer [Film]. Syncopy.
  2. J. Robert Oppenheimer – Nuclear Museum. (2022). Nuclear Museum. 
  3. J. Robert Oppenheimer | Biography, Manhattan Project, Atomic Bomb, Significance, & Facts | Britannica. (2024). In Encyclopædia Britannica. 
  4. How Do Nuclear Weapons Work? (2024). Union of Concerned Scientists.,pressure%20needed%20to%20ignite%20fusion 
  5. Ward, C. (2023, July 18). The Science Behind Oppenheimer’s A-Bomb Explained. SYFY Official Site; SYFY. 
  6. Johnson, M. (2023, July 22). How Oppenheimer weighed the odds of an atomic bomb test ending Earth. Washington Post; The Washington Post. 
  7. Manhattan Project: The Trinity Test, July 16, 1945. (2024). 
  8. Manhattan Project: Science > Nuclear Physics > CRITICAL MASS. (2024). 
  9. Atomic bombings of Hiroshima and Nagasaki – The bombing of Nagasaki | Britannica. (2024). In Encyclopædia Britannica.