America’s Path to the Atomic Bomb

The Trinity test of the Manhattan Project was the first detonation of a nuclear device. (Public Domain)

In September 1941, Werner Heisenberg, a German physicist, traveled to occupied Copenhagen to attend a conference and meet with his friend and mentor Niels Bohr, a Danish physicist. Initially, their interaction was cordial and amicable. However, tensions arose when Heisenberg approached Bohr for help in Germany’s nuclear research program, aimed at creating an atomic bomb. This request deeply unsettled Bohr, and he declined to assist Heisenberg. Two years later, the Gestapo targeted Bohr for arrest, forcing him to escape to Sweden for his safety.

A group of physicists at the 1946 Los Alamos colloquium on the Super. In the front row are Norris Bradbury, John Manley, Enrico Fermi and J.M.B. Kellogg. Behind Manley is Oppenheimer (wearing jacket and tie), and to his left is Richard Feynman. (Attributed to Los Alamos National Laboratory)

During the initial years of World War II, the United States remained distant from the European battlefields, yet this did not alleviate the concerns of physicists like Leo Szilard, Edward Teller, and Eugene Wigner, who were acutely aware of the immense potential of nuclear fission. Two years prior to U.S. involvement, these physicists collaborated on a letter co-signed by Albert Einstein, which they delivered to President Franklin D. Roosevelt. The letter aimed to address the worrisome possibility of hostile nations, particularly Nazi Germany, developing atomic bombs.

President Roosevelt heeded the warning and promptly informed his aide, Maj. Gen. Edwin “Pa” Watson, about the necessity for decisive action. The British MAUD Committee Report issued a similar warning, resulting in the creation of the Advisory Committee on Uranium. This, in turn, led to the establishment of the National Defense Research Committee, the S-1 Committee, and, eventually, the Manhattan Project, with full partnership from Canada and the UK.

Leslie Groves (L), military head of the Manhattan Project, with Oppenheimer in 1942. (Public Domain)

Maj. Gen. Leslie Groves, renowned for his strict and methodical leadership style, gained recognition while overseeing the construction of the Pentagon. It was during this time that Groves was selected to spearhead America’s ambitious endeavor to develop an atomic bomb. Recognizing his limited influence in scientific matters, Groves journeyed to the University of California, Berkeley, where he met with J. Robert Oppenheimer. Impressed by Oppenheimer’s profound understanding of the subject, Groves identified him as the ideal chief scientist for the Manhattan Project.

Despite having talented scientists like Heisenberg, Germany’s pursuit of an atomic bomb was hindered by limited resources and lack of commitment from Nazi officials. In contrast, Groves and Oppenheimer received unwavering support from three governments and the contributions of the world’s greatest scientific minds, including Enrico Fermi, Eugene Wigner, Edward Teller, Hans Bethe, Glenn Seaborg, Ernest Lawrence, Niels Bohr, and many others.

Unfortunately, this project also caught the attention of Soviet spies, such as Klaus Fuchs and David Greenglass, Ethel Rosenberg’s brother, which ultimately led to the Soviets receiving top secret nuclear information.

The Manhattan Project moved from New York to Los Alamos, New Mexico. The scientists would work around-the-clock in the secret and secluded town to create the atomic bomb.

Lawrence Berkeley Laboratory's scientific and technical staff around the magnet of the 60-inch cyclotron. LBL NEWS Magazine, Vol. 4, No. 3, Fall 1979, p. 37. Physics Morgue 1944-51 (P-4) Aug. 1938. (Public Domain)

The steps in nuclear development involved several tasks. Uranium ore would be processed and refined in Oak Ridge, Tennessee. For the Uranium-235 bomb’s design, a gun-assembly method was chosen. Due to the scarcity of uranium, which had to be mined and shipped, the focus shifted to using Plutonium-239 as the alternative. Plutonium would be created at the nuclear reactor in Hanford, Washington. The task at hand was to achieve a chain reaction, and the Los Alamos lab played a key role. Although plutonium would be more readily available, it proved more challenging to detonate than anticipated, rendering the gun-assembly design ineffective. The pressing question became: How can we successfully detonate plutonium?

Implosion and Black Holes

Oppenheimer tackled the challenges of plutonium, critical mass, and detonation through creative brainstorming. Drawing from his knowledge of cosmic objects, he recollected that, for a black hole to form, a dying star must first collapse in on itself like an imploding submarine. The tremendous compression resulted in critical mass, followed by a chain reaction and a supernova.

A spherical-shaped plutonium bomb named “The Gadget” was designed with an implosion assembly. It featured a neutron initiator encased in a Plutonium-239 core, surrounded by conventional explosives (the exact weight used is still classified), and wired with 32 precision firing units (detonators) surrounding the sphere. The big question remained: Would it explode? Only a test could provide the answer.

For this purpose, a remote location within the New Mexico desert, which came to be known as Trinity, was designated as the ideal testing ground.

"Little Boy" unit on trailer cradle in pit on Tinian, before loading into Enola Gay's bomb bay, Aug. 1, 1945. (Public Domain)

Ending the War

After Germany’s surrender in May 1945, Allied leaders planned a conference in Potsdam, Germany, where discussions focused on the ongoing war with Japan. Estimates suggested that an Allied invasion of Japan might extend the conflict for two more years and result in additional 500,000 to 1,000,000 Allied fatalities. The use of Japanese kamikazes led to mass casualties and severe PTSD among American sailors. As a result, it became crucial to successfully test “The Gadget” before the conclusion of the Potsdam Conference.

Another perilous theory emerged during this time: atmospheric ignition. Scientists worried that the intense heat from the Trinity explosion could lead to the atmospheric fusion of nitrogen and oxygen, potentially igniting the entire planet like a giant matchstick. Further studies revealed that the extremely low concentrations of deuterium (heavy water) in our oceans would prevent such a catastrophe from occurring. Nonetheless, Enrico Fermi, seemingly having nothing to lose, wagered that atmospheric ignition would destroy the planet, much to the annoyance of Groves.

For the testing, the weather was uncooperative, and it took some time to properly assemble all the components. Once everything was in place and assembled, “The Gadget” was raised to the top of a 100-foot-tall steel tower. With only 30 minutes left before detonation, the five soldiers guarding the bomb illuminated the tower with large lights, then jumped into their jeeps and drove away.

Oppenheimer (L) and Leslie Groves in September 1945 at the remains of the Trinity test in New Mexico. The white canvas overshoes prevented fallout from sticking to the soles of their shoes. U.S. Army Corps of Engineers. (Public Domain)

The Blinding Light at the End of the Tunnel

In a remote dugout shelter five miles away, Oppenheimer and the other men braced themselves as the countdown, blaring through the public address system, approached the final 20 seconds. With his brother Frank by his side, Oppenheimer nervously awaited the culmination of his monumental work. The tension and overwhelming stress kept him from sleeping the night before.

In a matter of seconds, they would all discover whether the United States and her allies had triumphed in this race they had undertaken. Lying face down on the dugout floor with their feet facing the illuminated tower, they waited and listened to the countdown as it neared zero.

Oppenheimer’s thoughts turned to the Bhagavad-Gita that states, “If the radiance of a thousand suns were to burst at once into the sky, that would be like the splendor of the Mighty One.”

“Three ... two ... one ... Now!” screamed the announcer at 5:29 a.m. Mountain Time on July 16, 1945, as an extraordinarily brilliant light transformed the night into day, followed by a searing heat, a powerful shockwave, a deafening roar, and a nightmarish fireball ascended into the sky.

Prometheus Revisited

At the Potsdam Conference, President Harry Truman informed Soviet leader Joseph Stalin about the existence of the atomic bomb to which Stalin showed no surprise. During the conference, the Allied leaders presented Japan with the Potsdam Declaration, an ultimatum to surrender or face complete annihilation. Japan refused, leaving Truman with a difficult decision: invade Japan, risking the death of millions of people, or use nuclear weapons. The United States had already seen 400,000 of its sons killed. Our Allies had lost far more.

On August 6, the B-29 Superfortress named Enola Gay dropped the Uranium-235 bomb over Hiroshima. When Japan still did not surrender, another B-29 called Bockscar dropped the Plutonium-239 bomb over Nagasaki on August 9. Faced with the possibility of more atomic bombs in America’s arsenal and with the Soviet Union declaring war on Japan, Emperor Hirohito announced Japan’s surrender.

Enola Gay after Hiroshima mission, entering hardstand. It is in its 6th Bombardment Group livery, with victor number 82 visible on fuselage just forward of the tail fin. (Public Domain)

Long after the dust settled, Oppenheimer’s greatest fears were realized. His mind, knowledge, and talent had not given fire to the world, but rather the ability to set the world on fire. With the secret out, the Soviet Union, the UK, France, and Maoist China scrambled to make their own bombs, with higher yields and far more power. Within seven years, the United States developed the hydrogen bomb, with the Soviets testing one of their own just nine months later.

Full of regret, Oppenheimer vocalized the profound implications of his discovery:

“We knew the world would not be the same. A few people laughed. A few people cried. Most people were silent. I remembered the line from the Hindu scripture, the Bhagavad-Gita. Vishnu is trying to persuade the prince that he should do his duty, and to impress him takes on his multi-armed form and says, ‘Now I am become Death, the destroyer of worlds.’ I suppose we all thought that. One way or another.”