The Second World War was still going on in favor of the Axis bloc when, in 1942, the United States laid the foundations for constructing the first atomic bomb. Soldiers and scientists engaged in secrecy in its construction, although they had different objectives: victory in the conflict for the first and demonstrating how nature works for the second. If, by pure coincidence, the use of nuclear weapons had led to the burning of the earth’s atmosphere, both goals would have been achieved, at the cost of some “negligible” consequences for humanity.
In the sun of New Mexico
In New Mexico, at about 2,100 meters above sea level, stands an imposing mesa. It is an upland like hundreds of others within Mexico’s borders. Residents called Valle Grande, Pajarito Plateau, or Location Y, depending on whether they were farmers, archaeologists, or scientists during World War II.
They believed that their beautiful valley, much of it still dominated by wild flora and fauna, was far from any advanced civilization, and second, that the people who occupied the Los Alamos Ranch School–since December 7, 1942–were anything but ordinary.
There, one could meet people named Nick Barker and Eugene Farmer. Still, something about them didn’t add up, starting with the communications to the school–that all went through P.O. Box 1663 in Santa Fe–and the massive deployment of air and ground forces that controlled the area.
And those astute bean growers weren’t wrong at all.
Many great minds, one goal
Behind the names of Nick Barker and Eugene Farmer were hidden, respectively Niels Bohr and Enrico Fermi, the two of the most excellent minds of contemporary physics. Bruno Rossi, Emilio Segrè, Edvard Teller, Eugen Wigner, James Chadwick, John von Neumann, Hans Bethe, Viktor Weisskopf, and Arthur Compton later joined the clan. Their group had achieved the highest number of Nobel Prizes.
The aim was to restore world peace or for some, condemn humanity to self-destruction in the attempt to achieve it: the construction of the first atomic bomb.
This project was called The Manhattan Project- It began in Chicago on December 2, 1942, when Enrico Fermi had activated the Chicago Pile 1, the first battery that showed new and impressive energy, i.e., the atomic one.
The year 1942 had been the year of the Japanese power. The Germans had advanced in Africa and Russia, demonstrating the ability of their commanders. Of course, there had already been some giving in signs, but nothing could foreshadow an unequivocal reversal of the war effort in December 1942. The creation of a definitive and invincible weapon was therefore extremely attractive.
The only ones aware of the project’s ultimate goal were the scientists. They were attracted by the possibility of pushing the science boundaries forward, thus they quickly accepted the task. Much more difficult was to convince the non-scientific personnel. They had to get to move to an unknown place for an unspecified reason, leaving behind the property, jobs, and in many cases even affections.
At Los Alamos, a veritable temporary Wild West-style town had grown up around the original school, with all the inconveniences of the case. The roads were perpetually covered with mud, personal and clothing hygiene were constantly threatened by the chronic lack of water in the area, the absence of adequate schools delayed the children’s education and, as if these were not enough, an uninviting barbed-wire fence and many armed guards not only kept the curious away but did not allow the members of the newly formed Los Alamos Scientific Laboratory to stray more than a hundred miles from the complex that had grown up in the far reaches of New Mexico.
So much secrecy solely to protect a weapon that was only theoretically possible.
During the years spent in Los Alamos, Fermi remained above all a physicist. After the Pile experiment, Fermi and the scientist of the Metallurgical Laboratory built a second experimental nuclear reactor. The power of this new reactor is about 110 kilowatts, 200,000 times the energy produced by the Chicago pile on December 2, 1942.
The Argonne pile offered Fermi and his team an unexpected opportunity to pursue fundamental research: in 1943 and 1944, they used the powerful neutron beams produced by this reactor to explore various fields, such as solid-state physics, without direct military interest. However, these results too remained secret until the end of the war. In the course of this research, Fermi and his colleagues invented the “thermal column”. Thus, Fermi’s group observed the reflection and refraction of neutrons, launching a new field of research, neutron optics, which will develop much after that.
In addition to his work on the Argonne pile, Fermi had the role of scientists’ advisor of the Manhattan Project. He frequently visited the laboratories in Oak Ridge and Hanford, where DuPont de Nemours engineers and scientists of the Metallurgical Laboratory built the first plutonium nuclear reactor.
Fermi brought his lights to overcome the obstacles that hinder its realization and, on several occasions, insisted against the methods of the “engineers”. Thus, Fermi remains, by his unique competencies in neutron physics, a “lighthouse” in difficult times, as Arthur Compton wrote.
The atomic bomb, from theory to practice
During the first two years, the project lacked the raw material for its construction. The two radioactive materials, uranium 235 (U-235) and plutonium 239 (Pu-239) were insufficient for war purposes.
But exactly how much fissile material was required for the construction of the device?
The quantity was unknown. Scientists only knew that the nuclear chain reaction would occur when a critical mass was reached. Besides, they did not know the explosion efficiency, i.e., the actual power of the bomb upon the chain reaction trigger was unknown.
A series of experiments led to two possible solutions. The first was a “cannon” method where fissile material was “shot” against another portion to reach the critical mass and trigger the chain reaction. The second method, known as the “implosion” method, involved subcritical material surrounded by conventional explosive that, when detonated, would compress the fissile material until it reached actual critical mass. Scientists chose the first more straightforward system.
Later, it was discovered that the method could only work with the uranium bomb. The plutonium produced at Oak Ridge and Hanford contained a considerable amount of the isotope 240 with a fast and natural release of neutrons, triggering an anticipated chain reaction and therefore it was unmanageable for war purposes.
Therefore, two bombs were foreseen: one based on uranium and “cannon”, with a fast construction. It was theoretically more limited and had destructive effects. The other one was based on plutonium and “implosion”, with a more complex structure and with harmful effects to be verified.
Los Alamos scientists accept the riskiest bet in the history of humanity
The production of enriched uranium for war purposes reached fifty kilograms in mid-1945. In the same period, the plutonium available in the U.S. could still be counted in grams. It made clear to everyone what was evident to scientists: the implosion device would be difficult to test before its actual use due to raw material shortness.
Some scientists theorized the possibility that the chain reaction would be uncontrollable, leading to the burning of the atmosphere and the destruction of our planet.
These risks led to an equally risky decision: to sacrifice one-third of the U.S. stockpile of fissile material to carry out a controlled nuclear explosion test on U.S. soil. The Project Trinity was the first real test of the atomic implosion bomb.
Brighter than the sun
Project Trinity was carried out at 5:30 a.m. on Monday, July 16. The explosion was of extraordinary power, according to the accounts of witnesses. Still, it would have been nothing compared to the subsequent atomic explosion that would take place there a few months later.
From the words of General Farrell, we can understand that the participants in the experiment understood that they were close to a turning point in human history: “The scene inside the shelter was dramatic beyond words… You could certainly say that almost everyone present was praying. Oppenheimer became tenser as the seconds ticked by. He could barely breathe.”
At precisely 5:29:45 a.m., physicist Samuel King Allison gave the order, “Now!”
What followed that command went beyond the expectations of many. Above all, the glow remained in the memory of the people inside the control stations and of the many family members, friends, and simple inhabitants of the area who, sensing something important, had ventured to the surrounding heights and, even beyond, up to two hundred miles away. One testimony described it as “many, many times brighter than the sunlight of New Mexico at noon on the brightest summer day.”
The bomb had worked, and the earth’s atmosphere was still in place, though lashed by an immense multicolored fireball and a roar that seemed to rise from the bowels of the earth. The explosion had volatilized the tower at the center of the range and lowered the ground six feet, vitrifying it. And, almost as if nothing had happened, humankind still existed.
The instrumentation perfectly recorded the devastating effects of the explosion, and from a purely scientific and military point of view, the test had been successful. Little Boy (the uranium bomb) and Fat Man (the plutonium bomb) would be used within a few weeks on the unsuspecting population of the Japanese cities of Hiroshima and Nagasaki, with hundreds of thousands of direct and indirect deaths and the definitive end of the Second World War. Einstein, Szilard, and other scientists concerned about the consequences of using such a destructive force were correct in believing that the world would never be the same after that discovery.
A weapon of planetary destruction was at the disposal of the U.S., and a hypothetical tyranny of this Western democracy over other nations would be avoided in the following decades only through necessary evils such as the atomic arsenal of the Soviet Union and the Cold War. Either way, it would have been more about politics at the highest levels. Nothing that would interest the scientists or the bean growers of Los Alamos.
- Manhattan Project: The Story of the Century by Bruce Cameron Reed, Springer, 2020
- The Manhattan Project: The Birth of the Atomic Bomb in the Words of Its Creators, Eyewitnesses, and Historians by Cynthia C. Kelly, Black Dog & Leventhal, 2020
Images on this page
- Y-12-shift-change: Ed Westcott / American Museum of Science and Energy | public domain
- Los-Alamos-colloquium: Los Alamos National Laboratory
- Hanford-B-Reactor-Area-1944: US Army Corps of Engineers | public domain
- atomic-bombing-of-japan: US Department of Energy | public domain
- manhattan-project-trinity-detonation: US Department of Energy | public domain