The Manhattan Project: Scientific Achievement vs Ethical Responsibility
It was still dark. The group of men felt the breeze getting warmer as the eastern horizon began to show signs of light. One of the men, tall with no expression, watched as final preparations were made to a large object in front of the group.
The others saw the anxiety in his face in a way that only those had had been around him could discern. The man walked forward, spoke with some of the technicians, and watched them haul it away. It was going to a tower, visible in the distance. Conversations around him continued, but only because it seemed like they had to. Somehow, the silence would have been louder.
Not long after, notifications came from the tower; an all clear was given. At 5:29 a.m., a flash of light that was so brilliant it could be seen from 200 miles away blossomed in the desert. The mushroom cloud rose 40,000 feet into the air, and the shock wave was felt 100 miles from ground zero. The man who all that morning had worn no expression, would later recall remembering a Hindu scripture in that moment: "Now I am become Death, the destroyer of worlds."
Another man who witnessed the test described the overwhelming impression it left: "A new thing had just been born; a new control; a new understanding of man, which man had acquired over nature." Another observer said, "The lighting effects beggared description. The whole country was lighted by a searing light with the intensity many times that of the midday sun."
Humanity had crossed a threshold.
A Chain of Discoveries
The roots of the atomic age can be found in a chain of scientific breakthroughs in the 1930s. A remarkable series of discoveries, combined with a close-knit scientific community, would ultimately make atomic weapons possible.
The countdown to creation began in 1932, when British physicist James Chadwick discovered the neutron, a fundamental particle that would prove essential for understanding and triggering nuclear reactions. Chadwick’s methodical approach and publication of his findings caused widespread interest both in the scientific community and the public. The next tick of the clock occurred two years later, when Irène and Frédéric Joliot-Curie created the first artificial radioactive element, demonstrating that humans could manipulate nuclear properties. But the most crucial breakthrough came in 1938, when German chemists Otto Hahn and Fritz Strassmann discovered nuclear fission – the splitting of uranium atoms, which releases enormous amounts of energy. Scientists worldwide immediately recognized the implications: a controlled chain reaction could create a revolutionary energy source, while an uncontrolled one might yield a weapon of unprecedented destructive power. Together, these three discoveries formed the scientific foundation for nuclear chain reactions: the neutron provided the "bullet," artificial radioactivity showed atoms could be manipulated, and fission supplied the explosive reaction and energy release mechanism.
Discoveries accelerated in 1939, when Hungarian physicist Leo Szilard and Italian physicist Enrico Fermi realized that uranium fission could trigger a chain reaction where neutrons released would go on to split more uranium atoms, which was the fundamental principle that would make atomic bombs possible. Fermi would later demonstrate this experimentally by creating the world's first controlled nuclear chain reaction in 1942, under the stands of the University of Chicago's football stadium, which involved a Geiger counter beeping faster and faster as reactions accelerated.
As the discoveries continued, so did the interest in the implications of such discoveries, especially by those waging war across Europe.
The Race
During this time, Nazi Germany was on the move. Many leading scientists fled Germany and other fascist regimes, bringing their knowledge to Allied nations. Leo Szilard was one of this group, and as he fled the Nazi horror, he became increasingly concerned that Germany might develop atomic weapons first.
In August 1939, Szilard drafted a letter that Albert Einstein signed and sent to President Franklin Roosevelt. The letter warned: "In the course of the last four months it has been made probable... that it may become possible to set up a nuclear chain reaction in a large mass of uranium, by which vast amounts of power and large quantities of new radium-like elements would be generated... This new phenomenon would also lead to the construction of bombs." Roosevelt responded by establishing what would eventually become the Manhattan Project.
The top-secret Army program was originally called the “Development of Substitute Materials”, but was changed due to the fear that such a name would draw suspicion. Instead, the official Army designation for the project was “Manhattan District” since its first headquarters were in Manhattan, though the name was deliberately misleading. An additional name, “Manhattan Project, was used by all others outside of the Army. The project was placed under the leadership of General Leslie Groves of the U.S. Army Corps of Engineers and Julius Robert Oppenheimer, who directed the scientific work at Los Alamos, New Mexico – a remote mesa chosen precisely for its isolation.
J. Robert Oppenheimer was a controversial choice for the project. Born into a wealthy New York family, Oppenheimer was a prodigy who studied minerals, physics, and chemistry by age 10, later graduating from Harvard and earning his doctorate in physics. Despite his intellectual brilliance, his appointment raised eyebrows due to his lack of leadership experience and troubling associations with Communist causes in the 1930s, which included relationships with Communist Party members, including his wife, brother, and sister-in-law. Nevertheless, General Groves recognized something others missed in Oppenheimer—an "overweening ambition" that would drive the project to completion—and insisted on his security clearance "without delay," declaring him "absolutely essential to the project." "He's a genius. A real genius... Why, Oppenheimer knows about everything. He can talk to you about anything you bring up. Well, not exactly. I guess there are a few things he doesn't know about. He doesn't know anything about sports."
The challenges Oppenheimer and the rest of the team faced with the Project were immense. Scientists needed to produce enough fissionable material – either uranium-235 or plutonium – to create a functional weapon. This required developing entirely new industrial processes at a seemingly impossible scale. In Oak Ridge, Tennessee, massive facilities were built to separate uranium isotopes, while in Hanford, Washington, nuclear reactors produced plutonium. These sites employed tens of thousands of workers, most of whom had no idea what they were building, even after the first bomb was detonated and later bombs destroyed cities.
At its peak, the production associated with the Manhattan Project employed 130,000 people and cost nearly $2 billion, equivalent to about $27 billion today. General Groves later reflected on this massive undertaking: "From the day I took charge of the project, I never wavered in my conviction that the weapon would work, and this faith sustained me through all the trials and tribulations of one of the most strenuous and difficult assignments any man could undertake."
Meanwhile, at Los Alamos, scientists worked on two different bomb designs: "Little Boy," a uranium bomb using a gun-type design, and "Fat Man," which used implosion to detonate a plutonium core.
The complexity of the implosion device required testing, which would later occur on July 16, 1945, and was dubbed the Trinity test. Oppenheimer later recalled thinking of a line from Hindu scripture as he witnessed the explosion: "Now I am become Death, the destroyer of worlds." The successful test confirmed that the atomic bomb was ready for military use.
Changes
As work continued, the tide of the war in Europe changed, and the project came into question. Germany had surrendered in May 1945, eliminating the original justification for developing the bomb. This development prompted intense debate among the scientists involved about whether the weapon should still be used. Leo Szilard, who had helped initiate the project, now led a petition urging President Truman not to use the bomb without warning. In his petition, Szilard wrote: "The development of atomic power will provide the nations with new means of destruction. The atomic bombs at our disposal represent only the first step in this direction, and there is almost no limit to the destructive power which will become available in the course of their future development."
Other scientists on the project held different views. Some felt that the enormous investment of resources and the potential to end the war quickly justified the bomb's use. Others were troubled by the ethical implications, but remained silent. As physicist Victor Weisskopf, who worked at Los Alamos, later reflected: "When we started the project, we thought only of the danger that the Germans would make the bomb and use it on the Allies. When Germany collapsed and we still continued, now to combat Japan, many of us felt deeply troubled."
As Marines and Sailors continued to die in the Pacific theatre, American planners anticipated a costly invasion of the Japanese home islands. Military estimates suggested that such an invasion could result in countless American casualties and potentially millions of Japanese deaths.
By summer 1945, Japan had transformed its home islands into a formidable defensive fortress. Japanese forces had been ordered to stand and fight "even to utter annihilation," with all divisions assigned to coastal defense prepared to die for their homeland, while heavy counterattacks by reserves aimed to force a decisive battle near any Allied beachheads. The Japanese had accurately predicted the exact beaches that would be targeted and had reinforced the island from one army division in spring 1945 to over 15 divisions by late summer, with their strategic focus being to kill as many Americans as possible to break U.S. public support for the invasion. Their air attack plan called for waves of 300-400 kamikaze aircraft every hour until all aircraft and pilots were expended—a rate that would have resulted in more attacks in three hours than in the entire three-month Okinawa campaign. William Shockley's study for Secretary of War, Henry Stimson, estimated conquering Japan would cost 1.7-4 million American casualties, and 5-10 million Japanese fatalities, with large-scale civilian participation in defense. These potential casualty estimates—regardless of which figures were used—made it "an accepted fact that America would lose a very large number of men.” This prompted President Harry Truman to finally authorize the use of atomic bombs to force Japan's surrender.
In his diary, Truman recorded his thoughts on the decision: "We have discovered the most terrible bomb in the history of the world. It may be the fire destruction prophesied in the Euphrates Valley Era, after Noah and his fabulous Ark... It is certainly a good thing for the world that Hitler's crowd or Stalin's did not discover this atomic bomb. It seems to be the most terrible thing ever discovered, but it can be made the most useful."
On August 6, 1945, a B-29 bomber named Enola Gay dropped "Little Boy" on Hiroshima, instantly killing an estimated 80,000 people. Colonel Paul Tibbets, the pilot of the Enola Gay, later said: "If Dante had been with us on the plane, he would have been terrified. The city we had seen so clearly in the sunlight a few minutes before was now an ugly smudge. It had completely disappeared under this awful blanket of smoke and fire."
It was believed that the destructive power of the first bomb would bring Japan to surrender unconditionally. It did not. Much to the surprise and horror of Allied Forces, the Japanese fought on, and another decision was made three days later to drop the second atomic bomb. Called "Fat Man", it was dropped on Nagasaki, killing approximately 40,000 more people. After the second bomb, Japan surrendered. By God’s grace, these two bombings remain the only time atomic weapons have been used in the history of warfare.
The Nuclear Age and the Cold War
The legacy of the Manhattan Project extends far beyond the end of World War II. It ushered in the nuclear age and fundamentally transformed geopolitics, military strategy, and international relations. The Soviet Union tested its first atomic bomb in 1949, much earlier than American officials had expected, triggering a nuclear arms race that defined the Cold War. At its height, this competition led to arsenals capable of destroying civilization many times over – the specter of mutually assured destruction. This doctrine held that neither superpower would dare launch a nuclear attack against the other since both possessed enough weapons to destroy each other completely, regardless of who struck first.
The Manhattan Project also revolutionized the relationship between science, government, and military power. It established a model for large-scale scientific research that continues to influence how we organize and fund major scientific endeavors. The national laboratory system that emerged from the project became a permanent fixture of American scientific research.
Perhaps most significantly, the Manhattan Project confronted scientists with profound ethical questions about their responsibility for the consequences of their work.
After the war, Oppenheimer opposed the development of the even more powerful hydrogen bomb, famously telling Truman, "I feel I have blood on my hands." In a 1954 security hearing that stripped him of his security clearance, Oppenheimer elaborated on the ethical burden scientists carried: "When you see something that is technically sweet, you go ahead and do it, and you argue about what to do about it only after you have had your technical success. That is the way it was with the atomic bomb."
Good Idea, Bad Idea
When discussing the Manhattan Project, we have to be real about the fact that it is a monumental scientific achievement and – because two things can be true at once – also a profound moral dilemma. It demonstrated humanity's capacity for brilliant innovation and our ability to mobilize resources to solve a seemingly impossible problem. Yet it also revealed the terrible, destructive power we can unleash. The same scientific breakthroughs that created nuclear weapons also advanced medicine, energy, and countless other beneficial applications. Today, we face similar challenges with technologies like artificial intelligence and genetic engineering - tools with tremendous potential for both the good and the bad.
As Oppenheimer himself reflected in 1947: "In some sort of crude sense which no vulgarity, no humor, no overstatement can quite extinguish, the physicists have known sin; and this is a knowledge which they cannot lose." The dual legacy of the Manhattan Project – of unprecedented achievement and profound moral burden – continues to resonate as we confront the technological challenges of our own time. Albert Einstein, whose letter to Roosevelt helped initiate the project, later expressed regret: "Had I known that the Germans would not succeed in developing an atomic bomb, I would have done nothing." Edward Teller, a leading figure in the development of the hydrogen bomb, offered this perspective: "The eyes of science have opened for evil as well as for good. The future is full of the most difficult problems. I am an optimist in spite of it all; so was Prometheus."
The Manhattan Project teaches us that scientific knowledge itself is neutral, but its applications are not. How we choose to use our expanding powers will determine whether they lead to benefits or catastrophe.
