42 Explosive Facts About The Manhattan Project

“Mankind invented the atomic bomb, but no mouse would ever construct a mousetrap”—Albert Einstein

Nothing motives man like the pursuit of total war. In 1942, the United States government brought together the most brilliant group of physicists ever assembled. Their mission: to build the deadliest weapon the world had ever seen, and bring an end to the bloodshed of World War II.

Of course, such monumental power comes at an exceedingly high cost. The invention of mankind’s most terrible weapon took a horrible tool on the scientists and workers involved—and the effects are still being felt today. Here are 42 explosive facts about the Manhattan Project.

Manhattan Project Facts

42. Sincerely Yours, Albert Einstein


In 1938, President Franklin Delano Roosevelt received a letter from the most famous scientist in the world, Albert Einstein. The letter alerted Roosevelt that the Germans might be working on an atomic bomb and urged him to consider a nuclear program for the United States. But the missive wasn’t all that it seemed…

In reality, the letter was written by physicist Dr. Leó Szilárd, a German-American physicist. Szilárd asked Einstein to sign the letter, so that the warning would come with some of that sweet, famous-genius street-cred.

41. Sorry, Al

Einstein was the most famous, respected physicist of his day, and one who had been outspoken about the dangers of Nazism. But even though he signed his name on the letter to Roosevelt, Einstein had no role in creating the atomic bomb.

An avowed pacifist, Einstein was denied a security clearance by the US government, and scientists working on the project were not even allowed to consult with the genius.

40. An Invitation from England

In 1939, the British government received the Frisch-Peierls memorandum, alerting them to research which would allow for an atomic bomb small enough to be carried in an airplane. The British set about conducting a nuclear weapons program immediately, and soon offered to share their research with the Americans. The Americans were shocked at how much more advanced British nuclear research was to their own: the Americans were way behind in a race they didn’t even know they were running yet.

39. The Origin of the Manhattan Project

The Advisory Project on Uranium finally began in late 1939, when the US government began funding research into nuclear chain reactions and uranium enrichment. Among the scientists to receive this early funding were Dr. Leó Szilárd and Dr. Enrico Fermi, two scientists at Columbia University studying isotope separation. This funding formed the basis of what became, in 1942, the Manhattan Project.


38. Where Is Everybody?

Though he remained involved in the Manhattan Project throughout, Fermi is best known today for “the Fermi Paradox,” which asks “if intelligent life exists in outer space, why hasn’t it contacted us?” One suggested solution? Humans are just too destructive.

37. The World Set Free

The British novelist H.G. Wells envisioned time machines and invisibility serums, but in 1914 he envisioned his biggest creation of all: an atomic bomb. In The World Set Free, Wells writes of a world where the old monarchies dissolve into warring nation-states, armed with weapons of… well, not quite awesome power, but certainly more destructive than anything available at the time. Among fans of the book? Leó Szilárd, who read it just before filing his patent on nuclear chain reactions.

36. General Groves

Primarily a military operation, the Manhattan Project was placed under the stewardship of the Army Corps of Engineers. The man originally chosen to oversee the Manhattan Project, General James Marshall, was deemed not up to the task. His replacement was General Leslie Groves. The prototypical Army Engineer, Groves also oversaw the construction of the Pentagon.

35. Dr. Manhattan

After much discussion, J. Robert Oppenheimer was chosen as scientific director of the project. Obsessed with his work, Oppenheimer didn’t listen to the radio or read newspapers and claimed to be completely ignorant of political matters. He did, however, subscribe to a Communist Party-affiliated weekly journal call People’s World. Just to be safe, the FBI opened a file on him.

34. Master of Destruction

Oppenheimer had studied in Germany under Max Born, who also instructed other future Nobel Prize winners Enrico Fermi, Wolfgang Pauli, and Werner Heisenberg. Oppenheimer’s eccentric, unpredictable behavior made him unpopular among his classmates, who presented Born with a petition to have him removed from the class. Oppenheimer was characteristically indifferent to his reputation, telling his brother, “I need physics more than friends.” One professor celebrated Oppenheimer’s graduation with the words “I’m glad that’s over.”

33. Nope-enheimer

It is not surprising, then, that many people opposed hiring Oppenheimer as the scientific director on the Manhattan Project. Oppenheimer was an alleged leftist and, with a history of carrying on extramarital affairs, he seemed a prime candidate for blackmail. Worse, they argued, Oppenheimer had never won the Nobel Prize, unlike Niels Bohr, James Franck, or Enrico Fermi, all of whom worked on the project.


32. The Frenemy

Among Oppenheimer’s critics was his sometimes-friend Edward Teller. The two had been working together since the earliest days of the Manhattan Project, with Oppenheimer rejecting (and ridiculing) Teller’s idea for a hydrogen bomb. Later, Teller would testify against Oppenheimer during a security hearing, costing Oppenheimer his governmental security clearance. After his testimony, Teller became deeply unpopular in the scientific community.

31. Coming to America

The Manhattan Project reaped the benefits of the mass emigration of scientists from Germany and Eastern Europe just prior to the start of the war. Among the scientists who worked on the Manhattan Project, more than a dozen fled Europe during the rise of Hitler and Mussolini, including Edward Teller, James Planck, and Niels Bohr.

30. Keeping the Secret in Secretary

While there were some female scientists involved in the Manhattan Project—notably Leona Woods and Maria Goeppert-Mayer—the Manhattan Project was a pretty masculine affair. Still, some women within the project had extraordinary responsibility and power. Hundreds of women were employed as secretaries and tasked with doing massive calculations by hand. Some of those secretaries were privy to extremely sensitive information, and in some cases, were better informed about the project than some of the scientists.

29. A Shoestring Budget

The total cost of the Manhattan Project was $2.2 billion. That’s practically a pittance: $2.2 billion is roughly the same as the US government spent every week during the war.

28. Manhattan

The project was centered around Manhattan for a variety of reasons. It was the home of Columbia University (where much of the theoretical research took place) and the Army Corps of Engineers’ North Atlantic Division, and also where Stone & Webster, the top contractor for the project, kept their main office.

27. A Bit of a Mouthful

Originally, the project was given the title “the Development of Substitute Materials Project,” but officials felt this was maybe too descriptive of the actual work of the project and would draw attention from spies. “The Manhattan Project” proved suitably vague, and easier to say.


26. Los Alamos

Los Alamos, New Mexico, was chosen to be the primary research and testing site for the Manhattan Project. It was plenty distant from civilization, providing room enough to drop bombs, not to mention protection from prying eyes. The site occupied 10,000 acres of land and had once been home to a boy’s reform school.

25. Living conditions

Life at Los Alamos wasn’t much different from life in a reform school either. Scientists lived in dorms at the site, with the bare essentials for comfort, in total isolation from the outside world.

24. Secret Sites

While Los Alamos was certainly the key testing site for the Manhattan Project, several other sites were used, including Oak Ridge, TN, and Hanford, WA. US scientists even had access to laboratories in Canada and Great Britain. Engineers for the Manhattan Project seized nearly 60,000 acres of American land through eminent domain, including private homes and farmland.

23. No Idea

Things were so secretive around the test sites that workers often did not even know what they were doing. In some cases, they didn’t find out until years later. For example, the US government employed 100,000 people in the construction of the Oak Ridge laboratory and subsequent enriching of uranium; because each facet of the labor was so compartmentalized, none of the workers were any the wiser.

22. Safety First

Efforts were made to ensure workplace safety, of course. Workers even had to swab their noses to ensure they hadn’t inhaled any of the deadly plutonium.

21. The Demon Core

After the deaths, workers at Los Alamos began referring to the plutonium mass as “the demon core.” Team leaders forbid the manual manipulation of the core, and in 1946 the core was used to create the bomb tested at Bikini Atoll.


20. Operation Alsos

In 1943, Colonel Boris Pash, a security officer for the Manhattan Project, led a mission through Italy, France and Germany in order to uncover details of the German nuclear program. While the German program was revealed to be small, especially in comparison to American efforts, the mission did lead to the apprehension of German scientists, including Werner Heisenberg and Max von Laue.

19. I Spy

Germans weren’t the only concern of the US government. Although they were allies during the war, the US was deeply distrustful of the Soviets and did not want the Soviets to gain access to nuclear technology. Despite the intense security, Soviet spies still managed to get information about the Manhattan Project. In fact some of the top scientists on the project, including George Koval and Klaus Fuchs, were revealed to have been spying for the Soviets long after the war had ended.

18. Clandestine Clan

Machinist David Greenglass worked at both Oak Ridge and Los Alamos, and it was later revealed that he was passing secrets on to a Soviet contact, Alexander Feklisov. Greenglass was Ethel Rosenberg’s brother, and he testified against her and her husband Julius, leading to their conviction and execution for committing espionage.

17. The Trinity Test

With a name inspired by the poetry of John Donne (whom Oppenheimer was reading at the time) the Trinity Test resulted in the world’s first atomic explosion on July 16, 1945. The seventeen-kiloton blast created a mushroom cloud 40,000 feet high.

16. Fat Man and Little Boy

By summer of 1945, the scientists of the Manhattan Project had effectively finished the job. They settled on two distinct designs. A plutonium-based bomb, codenamed Fat Man, weighed five tons and had the force of 21,000 tons of TNT. A uranium-based, “gun-type,” bomb called Little Boy weighed a half-ton less but was only one-tenth as efficient.

15. Thin Man

An early version of Little Boy was deemed unusable. Instead of uranium, Thin Man relied on plutonium but the fission rate of plutonium proved too high for a smaller, gun-type bomb.

14. Prompt and Utter Destruction

By 1945 the war had ground to a halt in Europe. The Allies slowly overpowered the Axis, forcing Germany to surrender. The war in Japan, however, showed no end in sight. At the Potsdam Conference in 1945, the US demanded Japan’s immediate surrender, announcing they had “a powerful new weapon” which would bring “prompt and utter destruction” if they continued to fight.

13. Agree to Disagree

Military officials were eager to get the war over and done with and intent on striking a large city. The Manhattan Project’s scientists argued that using the bomb in an open area should be a sufficient show of strength. Not wanting to take chances, the military—with the surprising support of Oppenheimer—overruled the scientists and set about maximizing casualties.

12. The Quebec Agreement

The US signed an agreement which required them to get the consent of the British government before any nuclear weapons were used. The Quebec Agreement was signed in Quebec City, Canada, in 1943. In July of 1945—just as the atomic bomb was moving from theory to reality—the Americans renegotiated the deal, ensuring that, rather than receiving permission to use nuclear weapons, they merely had to inform the British beforehand.

11. The Interim Committee

Free from British intervention, the Americans began strategizing. A secret group, the Interim Committee, convened in New York City to select targets for the atomic strike. Their ideal target was a large city with no known US prisoners of war. Nagasaki and Hiroshima were among the five cities placed on their grim shortlist.

10. Flying Superfortresses

With the bombs designed and targets designated, the military needed planes which could carry out the mission. Under Project Silverplate, the government worked with Boeing and the Glenn L. Martin Company (later Lockheed Martin) to design and build the B-29 Superfortress. Creation of the B-29 cost more than the Manhattan Project itself.

9. The Drop

On August 6, 1945, Colonel Paul Tibbets, flying the Enola Gay, dropped Little Boy on Hiroshima. Three days later, when the Japanese had still refused to surrender, Major Charles Sweeney and the crew of his plane, Bockscar, dropped the second atomic bomb, Fat Man, on Nagasaki. On August 14th, the Emperor of Japan announced their surrender.

8. Thanks, I Think

The Enola Gay was named after Paul Tibbets’ mother.

7. No Biggie

The atomic blast at Nagasaki was recorded at 16 kilotons, less than the blast recorded at Trinity.

6. The Death Toll

To date, the explosions at Hiroshima and Nagasaki have killed 226,000 people, the vast majority of them civilians. Among the immediate casualties were also 20 British, American, and Dutch prisoners of war. Today, some 164,000 explosion survivors—called hibakusha—are alive in Japan; 1% of them still suffer some sort of radiation-related illness.

5. Nuclear Reactions

Public reaction to the bomb was mixed. While Americans were glad the war was over, the devastation wrought by the bombs in Nagasaki and Hiroshima weighed heavily on their conscience and kicked off an age of anxiety over the dangers of nuclear weapons. Oppenheimer struggled with the political impact of his work until his death. But the legacy of the Manhattan Project was not entirely negative: that research contributed to the creation of nuclear energy, MRI machines, and radiation therapy.

4. Ongoing Work

The atomic drop on Hiroshima and Nagasaki effectively ended the Second World War. And while the Manhattan Project was officially closed, top-secret nuclear research continues at the seven National Laboratories, a group which includes the Los Alamos research facility.

3. Can’t Teach Common Sense

A fifteen-pound mass of plutonium is not a plaything. No one should know that better than physicists. But a relaxed attitude toward safety around these materials led to the deaths of two scientists at Los Alamos. The first, Henry Daghlian, dropped a tungsten carbide brick on the core, setting off a reaction which put him a coma and eventually killed him. The second, Louis Slotin, was conducting an experiment with the core and a piece of beryllium. He tried to keep the two materials separated with a screwdriver that he had lying around, but naturally, the screwdriver slipped. A massive release of radiation led to Slotin’s death nine days later.

2. Sigh of Relief

The citizens of Kokura, Japan did not realize how lucky they were. Kokura was the original intended target of “Fat Man.” Cloudy weather, however, made flying over Kokura tricky, and the bombers opted instead for Nagasaki.

1. Destroyer of Worlds

Upon witnessing the power of the Trinity bomb test, Oppenheimer famously declared, “I am become death, the destroyer of worlds.” These words, taken from the Bhagavad Gita, were certainly quoted by Oppenheimer, but likely not until he appeared in the 1965 documentary The Decision to Drop the Bomb.

Sources1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15

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