Family history

The latter part of the 19th century saw the formulation of Maxwell’s equations in 1862, which completely described the behavior of electric and magnetic fields. In 1879 Edison developed his commercially viable incandescent light bulb. In 1893, Tesla demonstrated wireless communication for the first time. By 1900, with these mysterious forces finally understood and applied, it seemed that the physical world was almost completely understood. The physicist Lord Kelvin famously remarked, “There is nothing new to be discovered in physics. All that remains is more and more precise measurement.”

Within five years Lord Kelvin could not possibly have been more wrong. A revolution in physics began with a small remaining puzzle left in Maxwell’s equations: The equations predicted that light should have a constant speed. The question was, constant with respect to what? It was believed that there must be some sort of aether permeating space, through which light traveled. Unfortunately, attempts like the Michelson-Morley experiment in 1887 had failed to prove such an aether’s existence.

In 1905, Einstein published his theory of (special) relativity, which correctly answered the question: Light moves at a constant speed relative to its observer, no matter how the observer is moving. This revelation had profound consequences: It meant that there was no absolute concept of space or time; everything was relative to one’s motion through space and time. Furthermore, it was impossible to quantify one’s motion through space without also quantifying one’s motion through time; space and time could only be understood as a single entity, spacetime, and motion through spacetime could be no faster than the speed of light. When applied to electricity and magnetism, relativity showed that electric forces could be seen as magnetic forces and vice versa, depending on one’s motion through spacetime, which meant that it also no longer made sense to speak of electricity and magnetism separately; the two forces were united as electromagnetism.

Later that year, Einstein also showed that his theory of relativity meant that mass could be measured in terms of energy, and vice versa. Because light moved at the cosmic speed limit, it had no mass, thus it was now understood that light was pure energy, and how much energy light carried was dependent only on the frequency of its wavelength. Einstein’s famous equation, E=mc2, demonstrated that if matter were somehow converted to energy, correspondingly large amounts of energy would be produced. In 1920 Arthur Eddington (correctly) proposed that such a conversion might be the mechanism by which stars (and by extension, our sun) produce their energy. From there, one might naturally wonder whether such a conversion process could be replicated on Earth.

My grandfather was a semester away from graduating New York City College during World War II with a degree in chemistry when he was drafted to the army. He completed basic training in Fort Hood, Texas, and then one night was abruptly woken up in his room, told to pack his bags and to be ready to board a train. On board the train he met a number of other people from the base, many of whom also had advanced educations in chemistry and physics. The men on board the train quickly surmised that they had been chosen for some sort of scientific undertaking (although there were jokes among themselves about how they might have been chosen for an elite fighting unit), but had no idea what the nature of the project might be until they reached their destination at Los Alamos, New Mexico, where they were taken into an auditorium and debriefed by Dr. Oppenheimer himself.

The project of course was the Manhattan Project, the effort that led to the creation of the first atomic bomb, and my grandfather was chosen to work on the project partly because of his experience with photography, a minor of his in college. In order to achieve the explosion that was created with the “Fat Man”, the bomb detonated over Nagasaki, its plutonium core needed to be compressed to a supercritical density, a point at which the plutonium nuclei would begin to break apart into their constituent protons and neutrons, which in turn would cause other plutonium nuclei to break apart, initiating a chain reaction and releasing large amounts of energy in the process. The plutonium core had to be compressed in a perfectly symmetrical manner, however, or the chain reaction would not take place. To achieve such a precise compression, conventional chemical explosives needed to be molded very carefully around the plutonium core. As it turned out, this was not a simple task, and a lot of prior testing was required to ensure a symmetrical implosion.

To run tests for symmetrical implosions, chemical explosives were wrapped around metal pipes prior to detonation, and the resulting deformation of the pipes was studied to determine whether the implosion was symmetrical. Of course, early tests did not produce symmetrical implosions. High-speed photography would have made it possible to determine the cause of the asymmetry; unfortunately, no camera in existence at the time had a shutter speed fast enough to catch the pipes in the process of deforming.

Film cameras work by depositing light onto a light-sensitive film, which is then developed in a dark room to produce the final photograph. The shutter speed controls the length of time that light is allowed to strike the photographic film, and usually involves a mechanical apparatus that opens and closes. Prior to the 1940’s, the fastest cameras had a shutter speed of about one thousandth of a second, which was far too slow for what was required at Los Alamos.

However, an engineer named Harold Edgerton had been independently working on a camera, now known as the Rapatronic camera, which could achieve shutter speeds on the order of 10 nanoseconds, one hundred thousand times faster than any predecessor. His camera used a shutter that relied on the polarization of light.

As a consequence of Maxwell’s equations, a photon of light can be viewed as a pair of oscillating electric and magnetic fields. If the electric field is oscillating in a particular direction when viewed from head-on, then the light is said to be polarized in that direction. It is possible to create a polarized beam of light by passing it through a filter of very thin conductive wires running in parallel. If the light has any component of polarization in the direction of the wires, it induces a small electric current in the wire, causing the light to scatter; thus only light that is polarized perpendicular to the wires passes through.

Certain liquids, such as nitrotoluene and nitrobenzene, are able to change the polarization of light passing through when a high voltage, or a large current, is applied. Edgerton’s camera used a cell of polar liquid sandwiched between two perpendicular light-polarizing filters to achieve its high shutter speeds. With both filters perpendicular, no light passes through. To take a picture, a voltage would be applied to the liquid cell. As current pulses through the liquid, light passing through the first filter is rotated the necessary ninety degrees to pass through the second filter and strike the photographic film. The chemical change in the polar liquid lasts for approximately ten nanoseconds, after which time the shutter is again closed.

My grandfather’s understanding of photography allowed him to participate in the process of replicating Edgerton’s camera and studying the deformation of pipes necessary to achieve a symmetrical implosion, which was critical for the development of the atomic bomb. Rapatronic cameras were also used to take pictures of the atomic bomb tested at Trinity in the first few milliseconds of its explosion. My grandfather has a number of such photographs in his possession.