by Carl Sagan
The immediate causes of death from nuclear attack are the blast wave, which can flatten heavily reinforced buildings many kilometers away, the firestorm, the gamma rays and the neutrons, which effectively fry the insides of passersby. A school girl who survived the American nuclear attack on Hiroshima, the event that ended the Second World War, wrote this first-hand account:
Through a darkness like the bottom of hell, I could hear the voices of the other students calling for their mothers. And at the base of the bridge, inside a big cistern that had been dug out there, was a mother weeping, holding above her head a naked baby that was burned bright red all over its body. And another mother was crying and sobbing as she gave her burned breast to her baby. In the cistern the students stood with only their heads above the water, and their two hands, which they clasped as they imploringly cried and screamed, calling for their parents. But every single person who passed was wounded, all of them, and there was no one, there was no one to turn to for help. And the singed hair on the heads of the people was frizzled and whitish and covered with dust. They did not appear to be human, not creatures of this world.
The Hiroshima explosion, unlike the subsequent Nagasaki explosion, was an air burst high above the surface, so the fallout was insignificant. But on March 1, 1954, a thermonuclear weapons test at Bikini in the Marshall Islands detonated at higher yield than expected. A great radioactive cloud was deposited on the tiny atoll of Rongalap, 150 kilometers away, where the inhabitants likened the explosion to the Sun rising in the West. A few hours later, radioactive ash fell on Rongalap like snow. The average dose received was only about 175 rads, a little less than half the dose needed to kill an average person. Being far from the explosion, not many people died. Of course, the radioactive strontium they ate was concentrated in their bones, and the radioactive iodine was concentrated in their thyroids. Two-thirds of the children and one-third of the adults later developed thyroid abnormalities, growth retardation or malignant tumors. In compensation, the Marshall Islanders received expert medical care.
The yield of the Hiroshima bomb was only thirteen kilotons, the equivalent of thirteen thousand tons of TNT. The Bikini test yield was fifteen megatons. In a full nuclear exchange, in the paroxysm of thermonuclear war, the equivalent of a million Hiroshima bombs would be dropped all over the world. At the Hiroshima death rate of some hundred thousand people killed per equivalent thirteen-kiloton weapon, this would be enough to kill a hundred billion people. But there were less than five billion people on the planet in the late twentieth century. Of course, in such an exchange, not everyone would be killed by the blast and the firestorm, the radiation and the fallout—although fallout does last for a longish time: 90 percent of the strontium 90 will decay in 96 years; 90 percent of the cesium 137, in 100 years; 90 percent of the iodine 131 in only a month.
The survivors would witness more subtle consequences of the war. A full nuclear exchange would burn the nitrogen in the upper air, converting it to oxides of nitrogen, which would in turn destroy a significant amount of the ozone in the high atmosphere, admitting an intense dose of solar ultraviolet radiation.* The increased ultraviolet flux would last for years. It would produce skin cancer preferentially in light-skinned people. Much more important, it would affect the ecology of our planet in an unknown way. Ultraviolet light destroys crops. Many microorganisms would be killed; we do not know which ones or how many, or what the consequences might be. The organisms killed might, for all we know, be at the base of a vast ecological pyramid at the top of which totter we.
The dust put into the air in a full nuclear exchange would reflect sunlight and cool the Earth a little. Even a little cooling can have disastrous agricultural consequences. Birds are more easily killed by radiation than insects. Plagues of insects and consequent further agricultural disorders are a likely consequence of nuclear war. There is also another kind of plague to worry about: the plague bacillus is endemic all over the Earth. In the late twentieth century humans did not much die of plague—not because it was absent, but because resistance was high. However, the radiation produced in a nuclear war, among its many other effects, debilitates the body’s immunological system, causing a deterioration of our ability to resist disease. In the longer term, there are mutations, new varieties of microbes and insects, that might cause still further problems for any human survivors of a nuclear holocaust; and perhaps after a while, when there has been enough time for the recessive mutations to recombine and be expressed, new and horrifying varieties of humans. Most of these mutations, when expressed, would be lethal. A few would not. And then there would be other agonies: the loss of loved ones; the legions of the burned, the blind and the mutilated; disease, plague, long-lived radioactive poisons in the air and water; the threat of tumors and stillbirths and malformed children; the absence of medical care; the hopeless sense of a civilization destroyed for nothing; the knowledge that we could have prevented it and did not.
L. F. Richardson was a British meteorologist interested in war. He wished to understand its causes. There are intellectual parallels between war and weather. Both are complex. Both exhibit regularities, implying that they are not implacable forces but natural systems that can be understood and controlled. To understand the global weather you must first collect a great body of meteorological data; you must discover how the weather actually behaves. Our approach must be the same, Richardson decided, if we are to understand warfare. So, for the years between 1820 and 1945, he collected data on the hundreds of wars that had been fought on our poor planet.
Richardson’s results were published posthumously in a book called The Statistics of Deadly Quarrels. Because he was interested in how long you had to wait for a war that would claim a specified number of victims, he defined an index, M, the magnitude of a war, a measure of the number of immediate deaths it causes. A war of magnitude M = 3 might be merely a skirmish, killing only a thousand people (103). M = 5 or M = 6 denote more serious wars, where a hundred thousand (105) or a million (106) people are killed. World Wars I and II had larger magnitudes. He found that the more people killed in a war, the less likely it was to occur, and the longer before you could witness it, just as violent storms occur less frequently than cloudbursts.
Richardson proposed that if you continue the curve to very small values of M, all the way to M = 0, it roughly predicts the worldwide incidence of murder; somewhere in the world someone is murdered every five minutes. Individual killings and wars on the largest scale are, he said, two ends of a continuum, an unbroken curve. It follows, not only in a trivial sense but also I believe in a very deep psychological sense, that war is murder writ large. When our well-being is threatened, when our illusions about ourselves are challenged, we tend—some of us at least—to fly into murderous rages. And when the same provocations are applied to nation states, they, too, sometimes fly into murderous rages, egged on often enough by those seeking personal power or profit. But as the technology of murder improves and the penalties of war increase, a great many people must be made to fly into murderous rages simultaneously for a major war to be mustered. Because the organs of mass communication are often in the hands of the state, this can commonly be arranged. (Nuclear war is the exception. It can be triggered by a very small number of people.)
We see here a conflict between our passions and what is sometimes called our better natures; between the deep, ancient reptilian part of the brain, the R-complex, in charge of murderous rages, and the more recently evolved mammalian and human parts of the brain, the limbic system and the cerebral cortex. When humans lived in small groups, when our weapons were comparatively paltry, even an enraged warrior could kill only a few. As our technology improved, the means of war also improved. In the same brief interval, we also have improved. We have tempered our anger, frustration and despair with reason. We have ameliorated on a planetary scale injustices that only recently were global and endemic. But our weapons can now kill billions. Have we improved fast enough? Are we teaching reason as effectively
as we can? Have we courageously studied the causes of war?
What is often called the strategy of nuclear deterrence is remarkable for its reliance on the behavior of our nonhuman ancestors. Henry Kissinger, a contemporary politician, wrote: “Deterrence depends, above all, on psychological criteria. For purposes of deterrence, a bluff taken seriously is more useful than a serious threat interpreted as a bluff.” Truly effective nuclear bluffing, however, includes occasional postures of irrationality, a distancing from the horrors of nuclear war. Then the potential enemy is tempted to submit on points of dispute rather than unleash a global confrontation, which the aura of irrationality has made plausible. The chief danger of adopting a credible pose of irrationality is that to succeed in the pretense you have to be very good. After a while, you get used to it. It becomes pretense no longer.
The global balance of terror, pioneered by the United States and the Soviet Union, holds hostage the citizens of the Earth. Each side draws limits on the permissible behavior of the other. The potential enemy is assured that if the limit is transgressed, nuclear war will follow. However, the definition of the limit changes from time to time. Each side must be quite confident that the other understands the new limits. Each side is tempted to increase its military advantage, but not in so striking a way as seriously to alarm the other. Each side continually explores the limits of the other’s tolerance, as in flights of nuclear bombers over the Arctic wastes; the Vietnam and Afghanistan wars—a few entries from a long and dolorous list. The global balance of terror is a very delicate balance. It depends on things not going wrong, on mistakes not being made, on the reptilian passions not being seriously aroused.
And so we return to Richardson. In the diagram the solid line is the waiting time for a war of magnitude M—that is, the average time we would have to wait to witness a war that kills 10m people (where M represents the number of zeroes after the one in our usual exponential arithmetic). Also shown, as a vertical bar at the right of the diagram, is the world population in recent years, which reached one billion people (M = 9) around 1835 and is now about 4.5 billion people (M = 9.7). When the Richardson curve crosses the vertical bar we have specified the waiting time to Doomsday: how many years until the population of the Earth is destroyed in some great war. With Richardson’s curve and the simplest extrapolation for the future growth of the human population, the two curves do not intersect until the thirtieth century or so, and Doomsday is deferred.
But World War II was of magnitude 7.7: some fifty million military personnel and noncombatants were killed. The technology of death advanced ominously. Nuclear weapons were used for the first time. There is little indication that the motivations and propensities for warfare have diminished since, and both conventional and nuclear weaponry has become far more deadly. Thus, the top of the Richardson curve is shifting downward by an unknown amount. If its new position is somewhere in the shaded region of the figure, we may have only another few decades until Doomsday. A more detailed comparison of the incidence of wars before and after 1945 might help to clarify this question. It is of more than passing concern.
This is merely another way of saying what we have known for decades: the development of nuclear weapons and their delivery systems will, sooner or later, lead to global disaster. Many of the American and European émigré scientists who developed the first nuclear weapons were profoundly distressed about the demon they had let loose on the world. They pleaded for the global abolition of nuclear weapons. But their pleas went unheeded; the prospect of a national strategic advantage galvanized both the U.S.S.R. and the United States, and the nuclear arms race began.
In the same period, there was a burgeoning international trade in the devastating non-nuclear weapons coyly called “conventional.” In the past twenty-five years, in dollars corrected for inflation, the annual international arms trade has gone from $300 million to much more than $20 billion. In the years between 1950 and 1968, for which good statistics seem to be available, there were, on the average, worldwide several accidents involving nuclear weapons per year, although perhaps no more than one or two accidental nuclear explosions. The weapons establishments in the Soviet Union, the United States and other nations are large and powerful. In the United States they include major corporations famous for their homey domestic manufactures. According to one estimate, the corporate profits in military weapons procurement are 30 to 50 percent higher than in an equally technological but competitive civilian market. Cost overruns in military weapons systems are permitted on a scale that would be considered unacceptable in the civilian sphere. In the Soviet Union the resources, quality, attention and care given to military production is in striking contrast to the little left for consumer goods. According to some estimates, almost half the scientists and high technologists on Earth are employed full- or part-time on military matters. Those engaged in the development and manufacture of weapons of mass destruction are given salaries, perquisites of power and, where possible, public honors at the highest levels available in their respective societies. The secrecy of weapons development, carried to especially extravagant lengths in the Soviet Union, implies that individuals so employed need almost never accept responsibility for their actions. They are protected and anonymous. Military secrecy makes the military the most difficult sector of any society for the citizens to monitor. If we do not know what they do, it is very hard for us to stop them. And with the rewards so substantial, with the hostile military establishments beholden to each other in some ghastly mutual embrace, the world discovers itself drifting toward the ultimate undoing of the human enterprise.
Every major power has some widely publicized justification for its procurement and stockpiling of weapons of mass destruction, often including a reptilian reminder of the presumed character and cultural defects of potential enemies (as opposed to us stout fellows), or of the intentions of others, but never ourselves, to conquer the world. Every nation seems to have its set of forbidden possibilities, which its citizenry and adherents must not at any cost be permitted to think seriously about. In the Soviet Union these include capitalism, God, and the surrender of national sovereignty; in the United States, socialism, atheism, and the surrender of national sovereignty. It is the same all over the world.
How would we explain the global arms race to a dispassionate extraterrestrial observer? How would we justify the most recent destabilizing developments of killer-satellites, particle beam weapons, lasers, neutron bombs, cruise missiles, and the proposed conversion of areas the size of modest countries to the enterprise of hiding each intercontinental ballistic missile among hundreds of decoys? Would we argue that ten thousand targeted nuclear warheads are likely to enhance the prospects for our survival? What account would we give of our stewardship of the planet Earth? We have heard the rationales offered by the nuclear superpowers. We know who speaks for the nations. But who speaks for the human species? Who speaks for Earth?
About two-thirds of the mass of the human brain is in the cerebral cortex, devoted to intuition and reason. Humans have evolved gregariously. We delight in each other’s company; we care for one another. We cooperate. Altruism is built into us. We have brilliantly deciphered some of the patterns of Nature. We have sufficient motivation to work together and the ability to figure out how to do it. If we are willing to contemplate nuclear war and the wholesale destruction of our emerging global society, should we not also be willing to contemplate a wholesale restructuring of our societies? From an extraterrestrial perspective, our global civilization is clearly on the edge of failure in the most important task it faces: to preserve the lives and well-being of the citizens of the planet. Should we not then be willing to explore vigorously, in every nation, major changes in the traditional ways of doing things, a fundamental redesign of economic, political, social and religious institutions?
Faced with so disquieting an alternative, we are always tempted to minimize the seriousness of the problem, to argue that those who worry about doomsdays are alarmists; to hol
d that fundamental changes in our institutions are impractical or contrary to “human nature,” as if nuclear war were practical, or as if there were only one human nature. Full-scale nuclear war has never happened. Somehow this is taken to imply that it never will. But we can experience it only once. By then it will be too late to reformulate the statistics.
The United States is one of the few governments that actually supports an agency devoted to reversing the arms race. But the comparative budgets of the Department of Defense (153 billion dollars per year in 1980) and of the Arms Control and Disarmament Agency (0.018 billion dollars per year) remind us of the relative importance we have assigned to the two activities. Would not a rational society spend more on understanding and preventing, than on preparing for, the next war? It is possible to study the causes of war. At present our understanding is meager—probably because disarmament budgets have, since the time of Sargon of Akkad, been somewhere between ineffective and nonexistent. Microbiologists and physicians study diseases mainly to cure people. Rarely are they rooting for the pathogen. Let us study war as if it were, as Einstein aptly called it, an illness of childhood. We have reached the point where proliferation of nuclear arms and resistance to nuclear disarmament threaten every person on the planet. There are no more special interests or special cases. Our survival depends on committing our intelligence and resources on a massive scale to take charge of our own destiny, to guarantee that Richardson’s curve does not veer to the right.