Nearly seven decades ago, beneath some old bleachers in Chicago, we brought nuclear technology into the world. A few of our finest physicists piled up some blocks of uranium and graphite, and they changed society forever. They were cavalier, and they were heroes. Now, whether we like it or not, their innovation is here to stay. We conceived it, and we can’t take it back.We own it.

 

Nuclear technology is powerful. It has both the power to create clean sustainable energy and, if applied in a fundamentally different mode, the power of mass destruction. It is a dichotomy of barbarism and munificence, war and peace. It has tremendous power to benefit humanity or to dehumanize.

 

The nuclear nascence was abrupt and violent. Few technologies progress from scientific discovery to practical application as rapidly as nuclear fission. The story is worth telling.

 

English physicist James Chadwick discovered the neutron in 1932 (Chadwick, 1932). It was the last satisfying piece to the puzzle of atomic structure, which academics had previously supposed to be composed of only protons and electrons.

 

Of course, once physicists discover a new particle, they are typically delighted to shoot it at as many varied targets as possible. This process is useful not only for satisfying ballistic proclivities, but also for elucidating properties of the particle.

 

German physicists Otto Hahn and Fritz Strassman were doing this in December of 1938 when something odd happened. Their target was uranium, the heaviest known chemical element. Speculation was circulating that adding neutrons to uranium could eventually create new, even heavier elements. Instead, their experiment produced barium, an element only about 60% as massive as uranium (Hahn, 1939). Their colleague Lise Meitner, who had recently fled Germany due to her Jewish heritage, and her nephew Otto Frisch correctly interpreted the results to conclude that neutron bombardment sometimes caused uranium atoms to actually split into two smaller atoms – one about 60% as massive as the original atom, the other about 40% (Meitner, 1939). People called this fission.
 

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When I was twenty, I took a spontaneous trip to Japan. A friend was studying abroad there, and I was enjoying a brief hiatus from my undergraduate studies. He was studying in Tokyo, and he planned to bicycle from there to Hiroshima—over seven hundred miles. Like any naïve and restless twenty-year-old, I offered to join him, and a few days later I was navigating the Tokyo subway system with the same old clunky bike I had had since I was twelve (and had barely touched since turning sixteen).

 

We spent the first day getting out of Tokyo, which was actually quite a feat, and we camped on the shores of Sagami Bay. The next two and a half weeks were similar – days filled with navigating dense urban tangles or gliding along windy mountainside roads, and nights camped just about anywhere we could find.  We wore the same clothes pleasant, vibrant city that showed few signs of its devastation six decades earlier. As a student of physics and nuclear engineering, I needed to see the Hiroshima Peace Memorial and its museum.

 

To be honest, I don’t remember much of what I saw in that museum. I read nearly every word there, every historical fact, but I don’t really remember those. I read all the scientific explanations and observed all the engineering diagrams, but even as a nuclear engineer, I don’t remember those either. The only things I remember are the watches.

 

The bomb dropped at 8:15 AM. People died. Their watches stopped. Time stopped. Over six decades later, the charred watches still read 8:15.

 

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Back in 1939, though, fission was simply another exciting discovery in physics. Two sobering facts quickly changed the mood. First, physicists realized that the fission process releases an abundance of energy. If all atoms in a sample of uranium fission, the amount of energy released per mass is about ten millions times greater than that released per mass in most chemical reactions (such as burning coal).

 

Second, each neutron-spurred uranium fission event releases not only two smaller atoms, but also two or three more neutrons. Of course, it is possible for one or more of those two or three neutrons to spur secondary fission events in nearby uranium atoms, which would produce even more neutrons that could spur even more fission events…

 

There is no clear end to the cycle.

 

As soon as prominent physicists realized this fact - that fissioning uranium could potentially lead to an endless “chain reaction” with each successive chain “link” growing larger and producing more energy – international collaboration ceased. U.S. physicists did not publish their results for fear that the most morbid applications of this “chain reaction” would not be lost on their foes in Europe.

 

Although Einstein had not been directly involved in studying fission, he had already achieved an iconic status that no other scientist of his time could match. The result was the famed Einstein-Szilard letter, which urged the U.S. government to immediately form an initiative to study fission and develop its applications. The letter explicitly stated the possibility that other nations could use it to develop a “bomb” that could destroy an entire city as well as the surrounding countryside.By that time, Nazi Germany had ceased selling uranium from Czechoslovakian mines it had occupied the previous year. Einstein signed this prescient letter in August of 1939, only eight months after Hahn and Meitner first discovered fission. Nazi Germany invaded Poland that September, and in October, Roosevelt authorized the Uranium Committee to begin its work. This organization later morphed into the covert Manhattan Engineering District, dubbed the “Manhattan Project.”

 

Just three years later, Szilard and Italian-American physicist Enrico Fermi achieved the world’s first fission chain reaction that was critical—a chain reaction in which each subsequent “link” is as large as (and not smaller than) each previous “link.” Each fission event produces just barely enough neutrons to continuously sustain more fission events. The energy production remains constant without any external source of neutrons. There is neither a neutron plethora, as in a supercritical chain reaction, nor a neutron dearth, as in a subcritical chain reaction. This achievement demonstrated that the chain reaction could in fact sustain itself—it constituted conclusive, tangible evidence that the bomb was realizable.Fermi and Szilard originally planned to construct this experiment at a national laboratory, but an untimely labor strike forced them to construct a makeshift laboratory in a rackets court beneath the bleachers of the abandoned Stagg Field at the University of Chicago. They called their experiment the “Chicago Pile,” because it was little more than a crude pile of uranium and graphite blocks (graphite slows down neutrons so that they can more readily fission uranium). This subterranean marvel was situated just a few miles from the center of the second largest city in America—and no one knew.

 

Two and a half years later, the Manhattan Project had designed, built, and tested atomic bombs. These are simply masses of uranium that allow for supercritical chain reactions such that each subsequent chain “link” is significantly larger than each previous “link”. The number of fissions (and thus the amount of energy produced) multiplies quickly and uncontrollably. Various mechanisms keep pressure on the uranium so that it remains in one piece long enough for the chain reaction to consume a significant portion of it, after which so much energy has been generated that nothing can keep it in one piece and the nuclear explosion occurs.

 

In August of 1945, less than seven years after the discovery of fission, President Truman ordered one of these devices to be dropped on the Japanese manufacturing city of Hiroshima. Three days later, when the Japanese still did not surrender, a second bomb was dropped on Nagasaki. The Japanese surrendered, and the war was won.

 

Sixty-six thousand people were vaporized when that first bomb dropped on Hiroshima. It was the most violent single instant in human history, and in my opinion, the most dehumanizing act in human history. Whether or not Truman made the right decision is an issue for historians and philosophers to debate. Would a traditional invasion of the Japanese Islands have cost even more lives and wrought even more ruin? We will never know. What we do know is that dropping that first bomb changed the world—changed society—forever.The bomb virtually eliminated the rationale for total war between world superpowers such that members of the millennial generation have a fundamentally different concept of war than their grandparents. To millennials, war is about large nations utilizing only a very small fraction of their manpower and economic resources to occupy small nations. Warfare has been reduced to guerilla tactics and terrorist networks, while the concept of a “standing army” seems antiquated.

 

The bomb also introduced an element of foreboding into society. The idea that entire cities could be destroyed in an instant without prior warning imbued a new kind of fear in us—a fear of not only death and destruction, but also of dehumanization—a fear that, like ants casually crushed under a boot, our lives never really meant much. This is why atomic bombs are uniquely repugnant among weapons – they rob us of our dignity and our meaning.

 

Fortunately, nuclear technology did not end in destruction and despondency. In the decades following its gruesome inception, scientists and engineers would redeem it in a stunning reversal, a stark dichotomy. The most dehumanizing technology the world had ever seen would be applied in a fundamentally different mode to benefit humanity. One of the twentieth century’s most beautiful ironies was the redemption of an instrument of war and its transformation into an instrument of peace.

 

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Mark Reed received his S.B. degree in Physics, as well as his S.B. and S.M. degrees in Nuclear Science and Engineering at the Massachusetts Institute of Technology (MIT), where he is currently pursuing a Ph.D. in Nuclear Science and Engineering.