“Further experimentation will lead him to discover these X rays produce an effect upon a photographic plate and that the rays are stopped by bones, but not by flesh. The result will be X ray photography, which will aid in diagnosis and revolutionize medical science. Physicians will be able to see inside the body prior to surgery. A man named Thomas Edison will build a device called an X ray fluoroscope, consisting of an X ray tube and a screen covered with crystals of barium platinocyanide. Upon striking the screen, the X rays will produce light visible to the naked eye. Any portion of the body placed between the X ray tube and the screen will produce an outline of the bones and organs within. Unfortunately, it will take time before the hazards of the X ray will be understood.
“Researchers who will repeatedly expose themselves to X rays will sustain severe burns and if this practice is continued, as it shall be, it will result in death. It will be discovered that exposure to X rays over a prolonged period can cause harm to the eyes, loss of hair, ulceration, inhibition of bone growth, sterility and damage to the blood cells. Men will learn that all living tissue can be destroyed if exposed to a sufficient amount of radiation, a term which will be strange to you, but I will endeavor to explain. You may have noticed that everyone aboard this ship wears a small glass cylinder containing a photographic film, something invented after the photographic plate. This device is called a dosimeter. Its purpose is to measure the amount of radiation one is exposed to.”
“You mean there is danger to us now?” said Verne.
“There is no cause for alarm. You will understand more presently. For now, let us return to the discovery of X rays, which will lead to the additional discovery that penetrating rays are also given off by certain crystals of an element known as uranium. In studying this phenomenon, Pierre and Marie Curie will give it a name-radioactivity.
“The Curies will embark upon research in an attempt to isolate the substance in uranium responsible for this phenomenon. In processing uranium ore, they will discover an element called radium. Pierre Curie will die upon being struck by a carriage in the street, but both his wife, Marie, and their daughter, Irene, who will carry on the work, will perish from exposure to radiation.
“Extensive scientific inquiry into the nature of this thing called radiation will establish the nature of a radioactive substance-its atoms are unstable. They disintegrate and become another element. Uranium becomes thorium. Thorium turns to radium. Radium becomes a gas called radon and so forth. This is known as nuclear disintegration and it results in the release of rays, or particles. The amount of time it takes for such a substance to decay in this manner to one half of its initial amount is called one half-life. Radon has a half-life of approximately four days. Certain types of uranium, on the other hand, can have a half-life of four and one half billion years. The shorter the half-life, the more atoms disintegrate per second.
“I mentioned two significant discoveries. The first will be that an element can be made radioactive. The second will come with the splitting of the atom. In 1932, an Englishman named Sir James Chadwick will discover a particle called a neutron. In 1934, Irene Curie and her husband, Frederic Joliot, will experiment with polonium and aluminum in their study of neutrons. They will discover that when alpha particles-a type of radiation-released from the polonium strike the aluminum, neutrons will be released, as well as electrons. Further, they will discover that the aluminum will continue to emit electrons for a short while after the polonium has been removed. In other words, they will find that an element which is not ordinarily radioactive can be made so artificially. When they bombard the aluminum with alpha particles, they will transform its atoms into the radioactive element radiophosphorous and this will be the first creation of artificially produced radioactive isotopes. You will find much of this unfamiliar and confusing, Mr. Verne, but there are books in the library we have aboard that explain all this in far greater detail. For our purposes now, I am simplifying as much as possible.
“These neutrons easily penetrate solid substances,” Drakov went on. “In the year 1938, two Germans named Otto Hahn and Fritz Strassmann will bombard uranium with neutrons. They will be astonished to find this experiment produce three light elements named barium, lanthanum and cerium. It will make no sense to them. They will realize these elements could only have come from the uranium, but this transmutation would be against everything known in science. They, will see the evidence before their eyes, but be reluctant to challenge the authority of eminent physicists such as Albert Einstein, Max Planck, Niels Bohr and-Enrico Fermi. They will report their discovery, but refrain from making any conclusions about it, stressing they might have made errors in their observations.
“News of this discovery will cause Bohr and Fermi to realize these men had succeeded in splitting the uranium atom. Nuclear fission. Bohr and Fermi will also realize that nuclear fission might involve a chain reaction, in other words, one split atom of uranium would release two neutrons, which would split two more atoms, releasing four neutrons, splitting four more atoms and releasing eight neutrons and so on, in geometric progression, releasing fabulous amounts of energy in an infinitesimal space of time.
“Albert Einstein will have enabled us to understand all this with a formula which will revolutionize science. In the year 1905, Einstein will make history when he writes the simple equation, E = MC ^2. Translated, it means energy equals mass multiplied by the square of the speed of light. The neutron, the sub-atomic particle with no electrical charge, strikes a large uranium nucleus, causing it to split. The ‘debris’ of this split is neutrons and lighter nuclei. What is left after the nucleus splits weighs less than the original. The mass which is lost is converted into energy via Einstein’s formula. This debris shatters other nuclei in a self-sustaining process called a chain reaction and all that is required to produce this is a sufficient quantity of uranium, below which this process will not be self-sustaining. This quantity is known as a critical mass.
“On the basis of Einstein’s formula, it can be calculated that one-thirtieth of a gram of water converted into pure energy would yield enough heat to turn a thousand tons of water into steam. A device which facilitates this process is called a nuclear reactor and it is that which drives the Nautilus.
“A uranium core-fuel rods-can be thought of as the firebox of your coal-fired steam engines. Nuclear fission produces heat. The steam from the heart of the Nautilus is taken to the engine room in two large, insulated pipes leading to four turbines, two turbo-generators and the auxiliary steam line. Again, I use terms you are unfamiliar with, but it suffices to say that this steam produces the power we require, then enters the condensers, having done its work, and in the form of water is pumped back into the steam generators, where it is heated once again by the pressurized water in what is called the primary loop of the reactor. The water in the primary loop is kept under very great pressure, so it cannot turn to steam. In this manner, we have a propulsion system in which no combustion is required. Coolant pumps circulate the water, drive motors raise and lower the fuel rods, controlling the reactor. The fuel rods will last for several years and when they are depleted, I have ways of getting more. Extreme precautions must be observed to ensure there is no leakage anywhere within the system, for such leakage would not only result in loss of pressure, but in radioactive contamination. That is the reason for the dosimeters, Mr. Verne, to monitor radioactive exposure.