The Manhattan Project: Einstein’s Devastating Legacy

From a lecture series presented by Professor Don Howard, Ph.D.

It had occurred to some thinkers that Einstein’s linking of mass with energy might some day find a military application, since even a tiny mass was now seen to have locked within it tremendous energy. But at the dawn of World War II, nearly everyone thought the prospect so remote as to be meaningless. The Manhattan Project would change those views forever.

Before The Manhattan Project

Late in 1938, Otto Hahn and Fritz Strassmann finally detected nuclear fission in experiments conducted in their Berlin laboratory, and their former collaborator Lise Meitner, then a Jewish refugee in Sweden, provided the conclusive interpretation of those results. On October 1, 1938, Hitler annexed the Sudetenland, formerly part of Czechoslovakia. When news of the discovery of fission began to spread at the beginning of 1939, with Hitler already on the march, the theoretical physics world knew that such innocence as it might once have possessed was gone for good.

Learn more: The Nuclear Fission Fuel Cycle

Fear of the Bomb

Scientists outside of Germany, many of them Jewish refugees from Germany and central Europe, rightly feared the possibility of a German atomic bomb. One noteworthy reaction was a campaign starting around February 1939 and led by Leo Szilard for a voluntary moratorium on publishing work on nuclear fission. This was a truly extraordinary step for a physics community once deeply committed to the principle of free and open communication in science. But a moratorium would be hard to enforce in a physics world where ego, ambition, patriotism, pride, and priority still overruled prudence.

It was the Paris group around Marie Curie’s former assistant and son-in-law, Frédéric Joliot-Curie, who most egregiously broke the ban with an April 1939 report about the rate of neutron production in uranium fission. It was a report that further alarmed those worried about a bomb by showing that more than enough neutrons were liberated to sustain a chain reaction.

Learn more: All About Atoms

Another reaction to the news of the reality of fission was Einstein’s signing of the famous letter to President Roosevelt on August 2, 1939, that warned of the threat from Germany and that led ultimately to the creation of the Allied atomic bomb project. Einstein did not write the letter himself. It was drafted by the ever-active Szilard, who drove out to Einstein’s vacation cottage in Peconic, New York, on Long Island. Nor did the letter make its way immediately to President Roosevelt. It was delivered through an intermediary, Roosevelt’s friend, the New York banker Alexander Saks, who finally met with Roosevelt on October 11. That was more than a month after World War II began with Germany’s invasion of Poland on September 1. When Saks pressed Roosevelt with the question of whether he understood the seriousness of what Einstein and Szilard were reporting, Roosevelt replied, “Alex, what you are after is to see that the Nazis don’t blow us up.”

Einstein's letter to Roosevelt for the article on The Manhattan Project

The First Test 

Image of Enrico Fermi for the article on The Manhattan Project
Enrico Fermi

It took nearly two more years and a second Szilard-instigated letter from Einstein before the major initiative that became the Manhattan Project was finally launched. More research was needed to prove the possibility of a chain reaction and therefore a bomb. An important moment came on December 2, 1942, when Enrico Fermi’s group at the University of Chicago produced the world’s first controlled chain reaction in a nuclear pile constructed in the squash courts under the stands of Chicago’s old Stagg Field. Stagg Field is now long gone but the exact location of Fermi’s reactor is marked today by a moving sculpture by Henry Moore.

The principal lab for bomb research, design, and assembly was set up on a mesa in the New Mexico wilderness at Los Alamos in the spring of 1943 under the overall scientific direction of J. Robert Oppenheimer. There were satellite labs at Oak Ridge, Tennessee, and Hanford, Washington, where uranium and plutonium for the bombs were manufactured. Additional research was done in many other places, including the so-called Metallurgical Laboratory at the University of Chicago.

Learn more: Binding Energy and the Mass Defect

Four years had passed since Einstein’s first letter to Roosevelt, but after work began at Los Alamos it progressed with extraordinary rapidity, given the nature of the many technical obstacles that had to be overcome. In just over two years, in July of 1945, the first bomb was ready for testing at Alamogordo, New Mexico, in the Jornada del Muerto Valley, which means “Journey of the Dead.” Witnessing that test, nicknamed “Trinity,” Oppenheimer is said to have recalled some words from the Hindu sacred text the Bhagavad Gita—the words “I am become death, destroyer of worlds.”

Germany’s Bomb Project

Image of Werner Heisenberg
Werner Heisenberg

At about the same time that Szilard and Einstein were collaborating on the first letter to Roosevelt, the German atomic bomb project was established under the leadership of Werner Heisenberg. There was still more than enough physics talent in Germany to justify the fear being felt elsewhere about the possibility of a German bomb.

Learn more: Fascist Italy, Nazi Germany—1922–36

As it turned out, Heisenberg’s group did not come anywhere near to manufacturing an atomic bomb. They didn’t even succeed in building a successful nuclear reactor. There were many reasons for the Germans’ lack of success, ranging from inadequate industrial infrastructure to Heisenberg’s ineptitude in both reactor design and calculating the critical mass of uranium—the amount needed for a self-sustaining chain reaction.

After the war, Heisenberg encouraged the view that German bomb scientists had deliberately focused their attention on reactor design to avoid having to build a bomb for Hitler. But debate still rages today over the ratio of truth to rationalization in Heisenberg’s version of history. Many people at the time, including Niels Bohr, were convinced that Heisenberg was seriously trying, if failing, to build a bomb.

Science and the State

If the lack of an adequate industrial infrastructure was an obstacle to the German bomb project, there was no such lack in the United States. The Manhattan Project was the largest scientific and technical project ever undertaken up to that time. Many millions of dollars were spent, and thousands of scientists and engineers were employed. The sheer scale of the project, and its success, permanently changed the role that science plays in society.

Learn more: Nuclear Strategy

There were many consequences. For one thing, after the atomic bombs were dropped on Hiroshima and Nagasaki, killing nearly 200,000 Japanese civilians, the physicists who had built the bomb realized that they now bore a moral responsibility different in kind and degree from any they had borne before. Physicists began to play a much more prominent public role in debates about atomic weapons and about the place of science in society more generally. Einstein’s was one of the most prominent voices in the ensuing public controversy.

The August 1939 letter to Roosevelt will always stand as the clearest marker of the change in the relationship between science and the state. Scientists had long advised governments, but no other single act by any other single scientist inaugurated fundamental realignments of the kind represented by the Manhattan Project. And yet that letter would not have had the impact it did had it not been for the way in which Einstein had put his scientific reputation to work in the service of political goals.

Learn more: 1942—The Dawn of the Atom

Einstein was uniquely capable of effecting change not only, or even mainly, because of his scientific reputation. Other Nobel Prize winners would not have been able, like Einstein, to move a nation. Einstein was capable of effecting change because of his prestige and notoriety as a thinker and advocate on a far larger stage than that of physics alone.

Is that a good thing? That’s a question for each of us to ponder in our own minds.

Keep Reading:
Einstein’s Experimental Elevator
The Origin of Mass
Is Dark Matter Lumpy or Smooth?
Great Leaders: Eisenhower and the Pursuit of Small Wins

For the Lecture Series: Albert Einstein: Physicist, Philosopher, Humanitarian
Taught by Professor Don Howard, Ph.D.
Albert Einstein:  Public Domain, Courtesy Wikimedia Commons Public Domain Photographer by Oren Jack Turner, princeton N.J.
Werner Heisenberg courtesy of, Bundesarchiv, Bild 183-R57262 / Unknown / CC-BY-SA 3.0 [CC BY-SA 3.0 de (], via Wikimedia Commons