In the summer of 1939, a single piece of paper altered the course of human history. It was a letter, signed by the world’s most famous scientist but conceived by another, lesser-known physicist. This document traveled from a quiet summer home on Long Island to the desk of the President of the United States. Its message warned of a terrifying new power. Ultimately, it set in motion the events that would lead to the atomic bomb and a new global era. This is the story of the Einstein-Szilard letter, a pivotal artifact of the 20th century.
At the heart of the warning was a stark description of a new scientific breakthrough and its devastating potential. The letter laid out the stakes in clear, direct language for President Franklin D. Roosevelt.
“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. Now it appears almost certain that this could be achieved in the immediate future.
>
This new phenomenon would also lead to the construction of bombs, and it is conceivable – though much less certain – that extremely powerful bombs of a new type may thus be constructed.”
The Spark of Fear: Discovery of Fission
The story begins not in America, but in Nazi Germany. Source In late 1938, German chemists Otto Hahn and Fritz Strassmann made a startling discovery . They successfully split the uranium atom, a process known as nuclear fission. This process released an immense amount of energy. The scientific community buzzed with the news. However, for some, the excitement was overshadowed by a chilling fear.
Hungarian physicist Leó Szilárd, who had fled the Nazis, immediately understood the implications. He realized that if a chain reaction could be sustained, the energy released could create a weapon of unimaginable power. Furthermore, he feared that German scientists, who were among the world’s best, would certainly recognize this potential. The thought of Adolf Hitler possessing an atomic bomb was a nightmare Szilárd believed the world had to prevent. He knew he had to act, but he needed a voice that authorities would listen to.
Crafting the Urgent Warning
Szilárd knew his own name carried little weight outside of physics circles. Therefore, he sought out the one scientist whose reputation was unparalleled: Albert Einstein. In July 1939, Szilárd and fellow physicist Eugene Wigner visited Einstein at his vacation home in Peconic, Long Island. At first, Einstein was skeptical. He had not been following the latest research on chain reactions closely. However, as Szilárd explained the frightening possibility, Einstein quickly grasped the danger.
He famously remarked, “I never thought of that!” Einstein agreed to lend his name and authority to the cause. The physicists drafted a letter to the Belgian government, warning them not to sell their large uranium stockpiles from the Belgian Congo to Germany. Subsequently, after consulting with economist Alexander Sachs, an unofficial advisor to President Roosevelt, they decided a direct appeal to the White House was necessary. Szilárd, with help from physicists Edward Teller and Eugene Wigner, drafted the final letter. Einstein reviewed it and signed the document that would forever link his name to the atomic bomb.
The Journey to the President
The letter, dated August 2, 1939, did not reach President Roosevelt for over two months. Germany’s invasion of Poland on September 1st heightened the urgency, but getting the document into the President’s hands proved difficult. Alexander Sachs had promised to deliver it personally. He understood that the letter’s complex scientific concepts needed a clear, persuasive explanation to have the intended impact.
Sachs finally met with Roosevelt on October 11, 1939. Source He didn’t just hand over the letter. Instead, he carefully summarized its contents and told a historical anecdote about Napoleon’s failure to support Robert Fulton’s invention of the steamboat. Sachs used this story to illustrate the danger of ignoring new technology. The strategy worked. After listening intently, President Roosevelt told his aide, “This requires action.” .
The Dawn of the Atomic Age
Roosevelt’s decision was immediate and decisive. He authorized the creation of the Advisory Committee on Uranium. This committee was the first official U.S. government body tasked with investigating the military implications of nuclear fission. The initial government investment was small. However, it marked a critical first step. The committee’s work confirmed the potential for an atomic weapon and laid the groundwork for a much larger effort.
Over the next few years, as World War II raged, the research accelerated. The initial committee evolved, and its findings led directly to the establishment of the Manhattan Project in 1942. This massive, top-secret enterprise brought together the nation’s top scientific minds. Its sole purpose was to build an atomic bomb before the Nazis could. The Einstein-Szilard letter was the direct catalyst for this monumental undertaking. It transformed a theoretical possibility into a national priority.
A Legacy of Power and Regret
The letter achieved its immediate goal. It successfully alerted the U.S. government to a potential existential threat. It initiated the program that would ultimately produce the weapons used on Hiroshima and Nagasaki, effectively ending the war. In this sense, the letter is one of the most consequential documents ever written. It fundamentally reshaped global politics, warfare, and the relationship between science and government.
However, this legacy is also fraught with complexity. Albert Einstein later expressed deep regret over his role. He signed the letter out of a genuine fear of a Nazi bomb. Yet, he was a lifelong pacifist who was horrified by the devastation his actions inadvertently helped unleash. In an interview years later, he lamented, “Had I known that the Germans would not succeed in developing an atomic bomb, I would have done nothing.” This profound regret adds a tragic, human dimension to the letter’s history. It serves as a powerful reminder of the unforeseen consequences that can arise from even the best-intentioned actions.
In conclusion, the Einstein-Szilard letter stands as a testament to a unique moment in history. It was a moment when scientific discovery, geopolitical fear, and personal responsibility converged. The document itself, preserved in the National Archives, is more than just ink on paper. It represents the precise point when humanity turned a corner, stepping uncertainly into the atomic age. Its story highlights the immense power of ideas and the profound moral dilemmas that accompany scientific progress.