Scientific Brilliance of Atomic bomb making & How scientific community fought later

Vijayabharathi C
10 min readSep 3


“It is an atomic bomb. It is a harnessing of the basic power of the universe. The force from which the sun draws its power has been loosed against those who brought war to the Far East” — Henry Truman(US President 1945) after dropping atomic bomb in hiroshima

If you’re a fan of science fiction movies, Christopher Nolan films are the most anticipated films of the year. In his films, he introduced fascinating science concepts, including ‘Time travels very slowly in dreams’ (from ‘Inception’), time dilation, and wormholes (in Interstellar). These scientific concepts after the release of his films, will make talk of them for certain months to the common audience, the media. The recent movie ‘Oppenheimer’ shares similar themes, resurrecting the atomic bomb and the dangers of nuclear bombs in certain areas. While the film travels more in the political persecution of the great scientist and father of the atomic bomb Dr J. Oppenheimer, it has patches of science behind the atomic bomb making. Oppenheimer served as the project manager for a weapon that posed a massive threat to human civilization, but the development of the atomic bomb was nonetheless regarded as an engineering wonder for all those involved. The pool of top scientists in the world at the time worked together magnificently. This significant technological advance in human history was made possible by a select group of inspirational scientists, who never gave up.Because of all the negative effects that the nuclear weapons race and atomic bomb will have on human society in the near future, these same inspired scientists battled against the evil. Science and technology have advanced recently, with examples being the human genome project and artificial intelligence. Scientists working with these technologies, which are frequently viewed as a threat to human civilization, can learn from the efforts of scientists working during the nuclear age, who banded together and advised their government not to exceed certain limitations in order to prevent Armageddon.

Who are they, How it is made ?

“It is a profound and necessary truth that the deep things in science are not found because they are useful; they were found because it was possible to find them.” —Dr J Robert Oppenheimer

The early 20th century was a golden era for physics and physicists. Leo Szilard, a well-known Hungarian scientist, was strolling alone down London Road in the early morning hours of October 1931. In a recent conference, his mentor Rutherford — a Nobel Prize winner and one of the most influential figures in physics — said that protons may divide an atom. It will release very little energy and have no use something similar to “Moonshine”. Obsessive Szilard firmly felt that every atom contains enormous energy and never trusted his mentor’s word. With this in mind, he approached a traffic light that was red at the moment. After a little while, a green light signal appeared, and the solution to his conundrum appeared in a flash. If a neutron bombards an atom, it divides into several pieces. When an atom is hit by a neutron, it splits into several pieces and releases a lot of energy. These liberated neutrons collide with another atom, splitting it, and liberating neutrons as well as additional significant energy. This uncontrolled activity is known as a nuclear chain reaction. The idea of a chain reaction originated at a traffic signal later led scientists to believe that nuclear energy could be used to build a bomb of terrifying proportions. At that time, the only thing that was unknown was which element, when assembled in a mass, could cause a chain reaction.

Nuclear fission was unintentionally discovered by Otto Hahn and Fritz Straussmann in December 1938 while they were experimenting with radiation on uranium. The scientific community led by Neils Bohr in the Atlantic region shared this discovery. Within a few days, the main concern among scientists was what would happen if Hitler built a risky weapon that harnessed the enormous energy found inside each atom. In 1939, Leo Szilard, who was inspired by Einstein, penned the renowned letter to US President Franklin Roosevelt. Roosevelt promptly approved the Manhattan Project, which involved creating the atomic weapon.

Making the Engineering marvel

Leslie Groves appointed Dr. J. Oppenheimer as the project manager for the Manhattan project. The US Military Policy Committee, which served as Henry Stimson’s war counsel, sought to construct two or more atomic bombs. One was used to demonstrate the bomb’s strength, and the other was used to alert enemies like Japan, Germany that additional bombs were now in their arsenal. Scientists suggested a basic shotgun design based on U235. This design calls for a set of uranium U235 rings to collide with another set of U235 rings as they move at a speed of 3000 m/s within an artillery tube. U235 rings will reach super critical mass as a result of this hitting. Once a small number of neutrons are hit by the internal initiator (beryllium+polonium) inside the artillery tube, this super critical mass will begin a nuclear chain reaction. There were difficulties even though the design seemed straightforward. The manufacture of uranium 235 is one of these difficulties. Only a few kilos of U235 could be produced in factories for a few tons of uranium U238 (natural uranium). Likewise, only 5 kg of U235 can undergo fission out of a total of 100 kg.

Scientists began searching for substitute fissionable elements that may trigger nuclear chain reactions as a result of this inefficiency. Later, scientists discovered that the isotope known as plutonium made large-scale chain reactions and nuclear fission conceivable. This Plutonium (Pu-239) is primarily synthetic; it is extremely uncommon in nature. A chemical procedure at a chemical industry can separate this element. Plutonium was simple to create in chemical factories in large quantities, and its fissionable efficiency was significantly higher than U235-based designs.

When scientists tried plutonium material with shot gun based approach, they faced failure. PU-239 rings that were fired inside an artillery tube at 3000m/sec evaporated before reaching their target rings. Scientists discovered that an implosion method was necessary to create fission for plutonium-based bombs. This implosion method will help PU-239 material in form of sphere to achieve super critical mass. At that time, the implosion-based bomb was considered to be a very cutting-edge scientific endeavor.

In this form of implosion, the plutonium sphere must be crushed symmetrically in all directions in order to become super critical (to create a chain reaction and release massive energy). Complex array of explosive Baratol together with an implosion lens were set around the plutonium sphere in order to crush it symmetrically. The blast was focused inward using an implosion lens in the manner of a converging convex lens. To set off the Baratol explosives fire simultaneously, 32 different detonators were made to fire concurrently. At the same time as occurred, a polonium/beryllium initiator (to produce free neutrons) was also activated. The compressed plutonium sphere would become “super critical” if all of the detonators and the initiator went off as intended. If the initiators did not fire simultaneously, the plutonium was subjected to an asymmetrical force.

Scientists were able to test shotgun-based designs on a modest scale at nearby laboratories with small explosives, even though U235-based and plutonium-based designs were research experiments. Implosion-based design was fraught with difficulties and unknowns. Scientists decided to validate a plutonium-based weapon in actual scale after taking these factors into account. Both the implosion device and the testing location were given the names “Gadget” and “Trinity,” respectively.

16th July 1945, 05:29:45, firing circuit of Gadget closed, 32 detonators fired simultaneously, shock waves generated by explosives travelled symmetrically with implosion lens acting as main medium. The plutonium spherical mass suddenly condensed to an eyeball-sized mass and reached supercritical mass. The beryllium/polonium initiator is now colliding with this compressed plutonium super critical mass. This initiator emits neutrons that begin to puncture the supercritical mass, starting a nuclear chain reaction. A huge amount of energy was unleashed in a few of milliseconds. Trinity test results were announced as an exceptional success in a matter of minutes. With the help of some 200 outstanding scientists and tens of thousands of employees on the Manhattan project, human civilisation entered the nuclear era.

How the scientists fought for humanity during atomic bomb creation & later

“Operated on this morning. Diagnosis not yet complete but results seem satisfactory and already exceed expectations.”

This telegram was delivered to Stimson, the secretary of war, on July 16, 1945. Its about trinity test success. At that time, he was in Germany attending the Potsdam Conference alongside Truman. After learning this, Truman felt incredibly confident and eager. With this increased self-assurance, he began to dominate Stalin at the Potsdam Conference, refusing to allow the Soviet Union for any concessions in the Mediterranean or Turkey for the post-World War II consolidation between West and the Soviet Union. The atomic bomb therefore entered politics, serving as the catalyst for the US and Soviet Union’s nuclear weapons race and cold war.

Few excellent scientists are aware of their moral obligation not to advance this dangerous weapon. When the great power of the atomic bomb becomes apparent, they have foresaw that a nuclear arms race will ensue. They(including Oppenheimer) proposed that all scientists worldwide should be informed of and encouraged to disclose the atomic bomb’s secrets. However, the US and British governments chose not to heed their cautions. A US B29 bomber dropped the “Little Boy” U235-based weapon on Aug. 6, 1945, killing 80,000 people immediately and another 100,000 within a few days as a result of radiation illness. Stalin was furious, and the Soviet Union aggressively expanded its bomb research, setting the stage for a nuclear arms race.

Even though many brilliant physicists contributed to preventing the threat posed by atomic bombs, certain great scientists played a significant role that went unnoticed by many. Listing here few

Neils Bohr:

Neils Bohr is well recognized for his important contributions to quantum physics, for which he was awarded the Nobel Prize in 1925. On the other hand, he was one of the first opponents of using an atomic weapon on a civilian population. He brought the news of Germany’s first successful nuclear fission to the United States in 1939.

He then claimed that the impending end of war will be brought about by the discovery of nuclear fission. He attempted to persuade “Roosevolt” and “Churchill” not to deploy the atomic bomb during World War II by warning it would trigger a nuclear arms race among major powers. When he attempted to explain the risks associated with nuclear weapons, Churchill reprimanded him like a wayward schoolchild. Even Roosevelt received his complaint about Neils Bohr’s unnecessary involvement in political matters. After World War II, he encouraged scientists to support global efforts to reduce nuclear weapons.

Leo Szilard

Szilard requested Einstein in 1939 to convince Roosevelt to launch the atomic bomb project right away because he believed Hitler would soon construct a similar device. But after a number of years, he has transformed. He fought tooth and nail to persuade Stimson, the secretary of war, not to bomb civilian areas just a few weeks before the bombs of Hiroshima. Knowing the immense harm that this weapon would cause, he produced a petition that was endorsed by numerous nuclear physicists. However, the president never received the petition.

To warn Japan how devastating the weapon was, he even advised US war machinery to drop an atomic bomb in an area that was not populated. He also advocated for international scientific cooperation for the development of nuclear energy, like Bohr. He was heartbroken by his inability to stop the bombings the Aug. 6 & Aug 9 attacks. After that, he declined to conduct any additional nuclear physics research.

Einstein & Oppenheimer

Einstein was sorry for his part in developing the atomic bomb. A few months before he passed away, he stated that signing the letter to President Roosevelt in 1939 was the biggest mistake of his life. “I wouldn’t have spoken out or even moved a finger if I had known that the Germans couldn’t make nuclear bombs”, he said later.

The atomic bomb’s creator, Oppenheimer, experienced depression after learning about the deaths in Hiroshima and Nagasaki because of his involvement in its development. Oppenheimer said to President Harry S. Truman during a visit to the White House in October 1945, “Mr. President, I feel I have blood on my hands.”Oppenheimer was named chairman of the General Advisory Committee. When Cold War tensions between the United States and the Soviet Union started to rise, he vehemently opposed the development of the hydrogen bomb — a “Super Bomb” envisioned by fellow Los Alamos scientist Edward Teller that was 1,000 times more potent than the atomic bomb.


The “Federation of Atomic Scientists” was founded in November 1945 by roughly a thousand individuals working in Los Alamos, Oak Ridge, Hanford, and Chicago. They advocated for congressional action against military control of nuclear technology while wearing crew cuts, bow ties, and tab collars. A civilian-led atomic energy commission was established in 1946 for all their efforts.


Human civilization is currently heading towards the next technological breakthrough, such as AI. Like the great scientists who first changed the world in the 1940s. AI now seems to be an integral part of everyone’s life. Still, skewed AI systems and biased algorithms pose a threat to life and liberty, especially for those who are already marginalized in society. The greatest risk posed by AI to humans is yet not fully understood. Scientists and engineers must collaborate with governments to prevent such threats in the future.



Vijayabharathi C

Silicon Validation Engineer, Interested in Topics: Conflicts/Peace, Space science, Technology, World Cinema