The Varieties of Scientific Experience

Eight

Tradition is a precious thing, a kind of distillation of tens or hundreds of thousands of generations of humans. It is a gift from our ancestors. But it is essential to remember that tradition is invented by human beings and for perfectly pragmatic purposes. If instead you believe that the traditions are from an exhortatory god and hold that the traditional wisdom is handed down directly from a deity, then we are much scandalized at the idea of challenging the conventions. But when the world is changing very fast, I suggest survival may depend precisely on our ability to change rapidly in the face of changing conditions. We live in precisely such a time.

Consider our past circumstances. Imagine our ancestors, a small, itinerant, nomadic group of hunter-gatherer people. Surely there was change in their lives. The last ice age must have been quite a challenge some ten to twenty thousand years ago. There must have been droughts and new animals suddenly migrating into their area. Of course there is change. But by and large the change is extraordinarily slow. The same traditions for chipping stone to make spears and arrowheads, for example, continues in the East African paleoanthropological sites for tens or hundreds of thousands of years.

In such a society, the external change was slow compared to the human generation time. Back then traditional wisdom, parental prescriptions, were perfectly valid and appropriate for generations. Children growing up of course paid the closest attention to these traditions, because they represented a kind of elixir of the wisdom of previous generations; it was constantly tested, and it constantly worked. It is not for nothing that ancestors were venerated. They were heroes to subsequent generations, because they passed on wisdom that could preserve lives and save them.

Now compare that with another reality, one in which the external changes, social or biological or climatic or whatever we wish, are rapid compared to a human generation time. Then parental wisdom may not be relevant to present circumstances. Then what we ourselves were taught and learned as youngsters may have dubious relevance to the circumstances of the day. Then there is a kind of intergenerational conflict, and that conflict is not restricted to intergenerational but is also intragener-ational, internally, because the part of us that was trained twenty years ago, let's say, must be in some conflict with the part of us that is trying to deal with the difficulties of today. So I claim that there are very different ways of thinking for these two circumstances: when change is slow compared to a generation time and when change is fast compared to a generation time. There are different survival strategies. And I would also like to suggest that there has never been a moment in the history of the human species in which so much change has happened as in our time. In fact, it can be argued that in many respects there never will be a time when the change can be so rapid as it has been in our generation.

For example, consider transportation and communication. Just a couple of centuries ago, the fastest practicable means of transportation was horseback. Well, now it is essentially the intercontinental ballistic missile. That is an improvement from tens of miles per hour to tens of miles per second in velocity. It's a very substantial increment. In communication a few centuries ago, except for rarely used semaphore and smoke-signaling systems, the speed of communication was again the speed of the horse. Today the speed of communication is the speed of light, faster than which nothing can go. And that represents a change from tens of miles per hour to 186,000 miles per second. And never will there be any improvement on that velocity.

Now, it's a very different world if the fastest that a message can get to us goes from the speed of a horse or a caravel to the speed of light. The speed of light means that we can talk-in essentially real time-to anybody on the Earth or even on the Moon. Or consider medicine. A few centuries ago, most of the children born to the great houses of Europe died in childhood. And they had the exemplary medical care of the age. Today even quite poor people in some nations at least have infant mortality astonishingly less than the crowned heads of state in the seventeenth century Or consider the availability of safe and inexpensive means of birth control. It immediately implies a revolution in human relations and especially in the status of women. These are all things that have happened very recently, and you can think of many, many others, all of which involve not just a change in the technical details of our lives but changes in how we think about ourselves in the world. Very major changes, and therefore not a circumstance where the wisdom of, say, the sixth century B.C. is necessarily relevant. It might be, but it might not be. And therefore, for this reason as well-for this reason especially-wisdom may lie not in simply the blind adherence to ancient tenets but in the vigorous and skeptical and creative investigation of a wide variety of alternatives.

For me personally, the kind of science that I do is utterly unthinkable in any other age. I find myself engaged in the spacecraft exploration of nearby worlds, something that would have been considered the most rank fantasy just two generations ago, when the Moon was the paradigm of the unobtainable. Some of you will remember those poems and popular songs-"Fly Me to the Moon," meaning asking for the impossible. And yet in our time a dozen human beings have walked on the surface of the Moon. And as I will stress in tomorrow's talk, that same technology that permits us to travel to other planets and stars also permits us to destroy ourselves-on a global scale, on a scale unprecedented in all of human history, and the mere knowledge that this is possible, even if we are lucky enough for it never to come about, must powerfully influence the lives of everybody who grows up in our time in a way that was not true for any other generation in human history.

I've spent much of my time over the last twenty years in the exploration of the solar system. Our robot emissaries have left the Earth, have visited every planet known to the ancients, from Mercury to Saturn, and reconnoitered some forty attendant smaller worlds, the satellites of those planets. We have flown by all those worlds, we have orbited and landed on three of them: the Moon, Venus, and Mars. There are something approaching a million close-up pictures of other worlds in our libraries. And it is a remarkable experience. Here's a world never before known by human beings, and then, for the first time, it is explored. This is a continuation of the spirit of adventure that I think has been a propelling force in human history. The worlds are lovely. They're exquisite. It is a kind of aesthetic experience to see them.

In the case of Mars, because of the Viking missions, we have been on the surface of that planet for some years, at least in two locales, and have essentially every day examined our surroundings. I personally spent in a certain sense a year on Mars in the course of that mission. I spent at least a great deal of my waking moments thinking about Mars. Now, at the end of such an experience, I feel something I hadn't planned on. And it is that these worlds, as exquisite and instructive as they are, are, as far as we can tell at this point, lifeless. There is in that lovely Martian landscape not a footprint, not an artifact, not even an old beer can, not a blade of grass, not a kangaroo rat, not even, so far as we can tell, a microbe. Mars and the Moon and Venus, as far as we can tell-the only planets we've landed on-are utterly lifeless. Maybe there's life in some places we haven't looked on those worlds. Maybe there used to be life and it is no longer. Maybe there one day will be life. But as far as we can tell here and now, there is none.

After that sort of experience, you then look back on your own world and you begin to have a kind of special feeling for it. You recognize that what we have here is in some sense rare. As I've argued previously, I suspect life and intelligence are a cosmic commonplace. But not so common that they're on every world. And in fact in our solar system we may discover that there is life only on this world.

This says that life is not guaranteed, that life requires something special, something improbable. I'm not for a moment suggesting it requires miraculous, divine, mystical intervention. But in a natural world, you can have probable events and you can have improbable events. And I'm sure this depends on the nature of the environments of the other planets. But there isn't any other planet that's just like the Earth, and, so far as we know so far, there isn't any other planet that has life on it. There are certainly premonitions and stirrings of life, the kind of organic chemistry on Titan, the big moon of Saturn that I referred to earlier. But that's still not the same as life. And so, by performing a first cursory inspection of our solar system, one realizes something important about where we come from.

When you investigate the vistas of time, you find something very similar. Because it is clear from the fossil record that almost every species that has ever existed is extinct; extinction is the rule, survival is the exception. And no species is guaranteed its tenure on this planet. I would like to describe to you one event that I've already referred to as central to the origin of the human species, because it is connected with the main topic of this talk. This is the worldwide extinction event that happened 65 million years ago, at the boundary between the Cretaceous and Tertiary periods of geological time, which also corresponds to the end of the Mesozoic age and the beginning of more recent times.

This is a close-up of a cliff base on a roadside near Gubbio in northern Italy. You can make out the scale of the image from the edge of a five-hundred-lire piece right up at the top. The surface crust has been scraped away a little bit, and the white material is calcium carbonate, essentially chalk, similar to the composition of the White Cliffs of Dover. These are the remains of countless small microorganisms that lived in the Cretaceous seas, forming little calcium carbonate shells that slowly fell through the warm waters of those seas and built up, during

fig. 35

Cretaceous time, for many millions of years. This deposit, as you can see, comes to an abrupt end. Time is increasing toward upper left. A layer of reddish brown rock lies above the older white carbonate, separated by a sharp boundary. And it's below this boundary that you find the last dinosaurs, and above the boundary you find an astonishing rate of proliferation of the small mammals into larger mammals, the events that are prerequisite for our own origins.

The sharpness of this boundary worldwide suggests some quite recent catastrophic event. The boundary is that thin layer of gray clay running diagonally across the picture. The clay- this is also true worldwide-has a quite high concentration, an anomalously high concentration, of a chemical element called iridium and other elements like it in the platinum group of metals. It is known that asteroids, and presumably cometary nuclei as well, have much higher abundances of iridium than do ordinary rocks on the Earth. And this iridium anomaly, now supported by a wide range of other data, is generally taken to be evidence for what happened to extinguish the dinosaurs and most of the other species of life on the Earth 65 million years ago.

This is an artist's conception of an object, maybe an asteroid, maybe a cometary nucleus, impacting the Cretaceous oceans. It's about ten kilometers across. It is bigger than the thickness of the ocean, so it is the same as impacting on land. The net result is to carve out in the ocean floor an immense crater and propel the fine particles thus generated into high orbit, making a vast

fig. 36

cloud of pulverized ocean bottom and pulverized impacting object that takes some years to settle out from the Earth's high atmosphere. During that period of time, sunlight is impeded from reaching the surface of the Earth, and the net result is a darkened and cold surface worldwide, which led, because of the differences in mammalian and reptilian physiology, to the extinction of the dinosaurs and many other kinds of life.

That is what happened to the dinosaurs. They were powerless to anticipate it and certainly to prevent it. What I would like now to describe is a catastrophe that in some respects is quite similar, one that endangers the future of our own species. It is very different in one respect: Unlike the dinosaurs, we ourselves, at enormous cost in treasure, have created this danger. We are solely responsible for its existence, and we have the means of preventing it, if we are sufficiently courageous and sufficiently willing to reconsider the conventional wisdom. That problem is nuclear war.

The bombs that destroyed Hiroshima and Nagasaki-everybody's read about them, we know something about what they did-killed some quarter of a million people, making no distinctions according to age, sex, class, occupation, or anything else. The planet Earth today has fifty-five thousand nuclear weapons, almost all of which are more powerful than the bombs that destroyed Hiroshima and Nagasaki and some of which are, each of them, a thousand times more powerful. [7] Some twenty to twenty-two thousand of these weapons are called strategic weapons, and they are poised for as rapid delivery as possible, essentially halfway across the world to someone else's homeland.

The ballistic missiles are sufficiently capable that typical transit times are less than half an hour. Twenty thousand strategic weapons in the world is a very large number. For example, let's ask how many cities there are on the planet Earth. If you define a city as having more than one hundred thousand people in it, there are twenty-three hundred cities on the Earth. So the United States and the Soviet Union could, if they wished, destroy every city on the Earth and have eighteen thousand strategic weapons left over to do something else with.

It is my thesis that it is not only imprudent but foolish to an extreme unprecedented in the events of the human species to have so large an arsenal of weapons of such destructive power simply available. Now, the prompt effects of nuclear war are reasonably well known. I will say a few words about them, but I want to concentrate mainly on the more recently discovered, more poorly known, delayed longer-term and global effects.

Imagine the destruction of New York City by two one-megaton nuclear explosions in a global war. You could choose any other city on the planet, and in a nuclear war you can be reasonably confident that that city would suffer some similar fate. Starting at the World Trade Center and continuing about ten miles in all directions, the effects would play out. You know about the fireball and the shock waves, the prompt neutrons and gamma rays, the fires, the collapsing buildings, the sorts of thing that were responsible for most of the deaths at Hiroshima and Nagasaki. But the bomb light also sets fires, some of which are blown out by the shock wave as the mushroom cloud rises. Others are not.

And these conflagrations can grow. And in many cases, although certainly not all, the conflagrations merge to produce a firestorm. Recent work suggests that firestorms should be much more common and much more severe than had been expected in earlier research, producing the kind of fire as in a well-tended fireplace with an excellent draft. The net result, as advertised: No cities are left standing. But that's the least of the problem.

Beyond the obliteration of the cities is the production of a pall of sooty smoke sitting not just above the city but carried by the fire to quite high altitudes, where this dark smoke is heated by the Sun, which then makes it expand still more. This happens, obviously, not just above one target but above many or most targets.

Cities and petrochemical facilities would be preferentially targeted. Prevailing winds would blow the fine particles in the same direction, from west to east. In anything like a full exchange something like ten thousand nuclear weapons would be detonated.

Some ten days later, there would still be a few nuclear explosions from, I don't know, nuclear-submarine commanders who have not been told that the war was over. The smoke and dust would circulate all around the planet in longitude and spread poleward and equatorward in latitude. The Northern Hemisphere would be almost entirely socked in with smoke and dust. You would see outriders, plumes of smoke in the Southern Hemisphere. The cloud would then cross the equator well into the Southern Hemisphere. And while the effects would be somewhat less in the Southern Hemisphere, sunlight would dim and the temperatures would fall there as 'well.

Some calculations have been done at the National Center for Atmospheric Research in which a five-thousand-megaton war occurs in July. The widespread distribution of smoke twenty days after the war is over would produce temperature declines as much as fifteen to twenty-five centigrade degrees below normal.

The net result, as you might imagine, is bad. The effects are global. It appears that they last for months, possibly years. Imagine what disastrous worldwide consequences the destruction of agriculture alone would have. The northern midlatitude target zone is precisely the region that is the principal source of food exports (and experts) to the rest of the world. Even countries nowhere near malnutrition today-Japan, for example- could utterly collapse in a nuclear war from the clouds blown eastward from China, an almost certain target in a nuclear war. Even apart from that, if there were no climatic effects in Japan, and not a single nuclear weapon dropped on Japan, it turns out that more than half the food that people eat there is imported. That alone would kill enormous numbers of people in Japan, and the actual effects would be much worse.

When scientists try to estimate what the consequences of a nuclear war would be, you have to worry not just about the prompt effects. They would be bad enough. The World Health Organization calculates that in an especially nasty nuclear war the prompt effects might kill almost half the people on the planet. You also have to worry about nuclear winter, the cold and the dark that I've just been describing; you have to worry about such facts that those conditions kill not just people and agricultural plants and domesticated animals but the natural ecosystem as well. At just the point that survivors might want to go to the natural ecosystem to live off it, it would be severely stressed.

There is a kind of witches' brew of effects that have been very poorly studied by the various defense establishments, some more than others. These include, for example, pyrotoxins, the smogs of poison gas produced from the burning of modern synthetics in cities, increased ultraviolet light from the partial destruction of the protective ozone layer, and the intermediate timescale radioactive fallout, which turns out to be some ten times more than confident assurances by miscellaneous governments have had it. And so on. The net result of the simultaneous imposition of these independently severe stresses on the environment will certainly be the destruction of our global civilization, including Southern Hemisphere nations, nations far removed from the conflict-nations, if you can find any, that had no part of the quarrel between the United States and the Soviet Union-and, of course, northern midlatitude nations, it goes without saying.

Beyond that, many biologists believe that massive extinctions are likely of plants, of animals, of microorganisms, the possibility of a wholesale restructuring of the kind of life we have on Earth.

It would probably not be as severe as the Cretaceous-Tertiary catastrophe, but possibly approaching it. A number of scientists have said that under those circumstances they cannot exclude the extinction of the human species.

Now, extinction seems to me serious. Hard to think of something more serious, more worthy of our attention, more crying out to be prevented. Extinction is forever. Extinction undoes the human enterprise. Extinction makes pointless the activities of all of our ancestors back those hundreds of thousands or millions of years. Because surely if they struggled for anything, it was for the continuance of our species. And yet the paleonto-logical record is absolutely clear. Most species become extinct. There's nothing that guarantees it won't happen to us. In the ordinary course of events, it might happen to us. Just wait long enough. A million years is quite young for a species. But we are a peculiar species. We have invented the means of our own self-destruction. And it can be argued that we show only modest disinclination to use it.

This is what in a number of Christian theologies is called crimes against Creation: the massive destruction of beings on the planet, the disruption of the exquisitely balanced ecology that has tortuously grown up through the evolutionary process on this planet. So, since this is clearly recognized as such a theological crime as well as all the other kinds of crimes, it is reasonable to ask where are the religions-the established religions, the incidental independent-thinker religionists-on nuclear war?

It seems to me this is the issue above all others on which religions can be calibrated, can be judged. Because certainly the preservation of life is essential if the religion is to continue. Or anything else. And for me personally, I believe there is simply no more pressing issue. Whatever else we're interested in, it is fundamentally compromised by nuclear war. Whatever personal hopes we have for the future, ambitions for children and grandchildren, generalized expectations for future generations-they are all fundamentally threatened by the danger of nuclear war.

It seems to me that there are many respects in which religions can play a benign, useful, salutary, practical, functional role in the prevention of nuclear war. And there are still other ways that are maybe longer shots but, considering the stakes, are well worth considering. One has to do with perspective.

Now, not all religions have this perspective on the stewardship of the Earth by men and women, but they could. The idea is that this world is not here for us only. It is for all human generations to come. And not just for humans. Or even if you took only a very narrow view of the world, if you were a speciesist in the same sense as being a racist or a sexist, still you would have to be very careful about all those other nonhuman species, because in many intricate ways our lives depend on them. I remind you of the elementary fact that we breathe the waste products of plants and plants breathe the waste products of humans. A very intimate relationship if you think about it. And that relationship is responsible for every breath you take. We in fact depend on the plants, it turns out, a lot more than the plants depend on us. So that sense that this is a world that is worth taking care of is, it seems to me, something that could be at the heart of religions that wished to make a significant contribution to the human future.

Then there are more direct kinds of political activity. For example, religious people played a role in the abolition of slavery in the United States, and elsewhere. Religions played a fundamental role in the independence movement in India and in other countries and the civil rights movement in the United States. Religions and religious leaders have played very important roles in getting the human species out of situations that we should never have gotten into that profoundly compromised our ability to survive, and there is no reason religions could not in the future take on similar roles. There are, of course, occasional circumstances, individual clergypersons who have taken that role in this particular crisis, but it is hard to see any major religion that has made this kind of political activity its foremost objective.

There is also the issue of moral courage. Religions, because they are institutionalized and have many adherents, are able to provide role models, to demonstrate that acts of conscience are creditable, are respectable. They can raise awkward possibilities. The pope, for example, has raised (although not answered) the question about the moral responsibility of workers who develop and produce weapons of mass destruction.

Or is it okay as long as there is a local excuse? Are some excuses better than other excuses? What are the implications for scientists? For corporate executives? For those who invest in such companies? For military personnel? The archbishop of Amarillo has urged workers at a nuclear-weapons facility in his diocese to quit. So far as I know, no one has quit. Religions can remind us of unpopular truths. Religions can speak truth to power. It's a very important function that is often not carried out by all the other sectors of society.

Religions can also speak to their own sectarian eschatologies, especially where they run contrary to human survival. I'm thinking, for example, about the Christian fundamentalist view in the United States that the end of the world is unerringly predicted in the book of Revelation, that the details in the book of Revelation are sufficiently similar to those of a nuclear war that it is the duty of a Christian not to prevent nuclear war. The Christian who does so would be interfering with God's plan. Now, I know I have stated this somewhat more baldly than the advocates of such views, but I believe that is what it comes down to. Christians can play a useful role in providing a steadying hand on people with such eschatologies, because they're very dangerous.

Suppose someone with such a view were in a position of power, and there was a critical decision that had to be made in a moment, and that person had a little sense that maybe this was the fulfillment of biblical prophecy. Maybe he shouldn't make the effort to avoid this, especially if he believed that he himself will be one of the first people to leave the Earth and appear at the right hand of God. He might be interested to see what that would be like. Why slow it down?

Religion has a long history of brilliant creativity in myth and metaphor. This is a field crying out for apposite myth and metaphor. Religions can combat fatalism. They can engender hope. They can clarify our bonds with other human beings all over the planet. They can remind us that we are all in this together. There are many functions that religion can serve in trying to prevent this ultimate catastrophe. Ultimate for us-I want to stress that we're not talking about the elimination of all life on Earth. Doubtless roaches and grass and sulfur-metabolizing worms that live in hot vents in the ocean bottoms would survive nuclear war. It is not the Earth that is at stake, it is not life on Earth that's at stake, it is merely us and all we stand for that is at stake.

Now, along these lines I should also say that at least some religions have specific suggestions on standards of moral behavior that conceivably could be relevant to this problem. (I don't guarantee it; I don't know. The experiment has not been carried out.) And in particular there is the issue of the Golden Rule. Christianity says that you should love your enemy. It certainly doesn't say that you should vaporize his children. But it goes much further than that. It says not just abide your enemy, not just tolerate him, love him.

Well, it's important to ask, what does that mean? Is this just window dressing, or do the Christians mean it?

Christianity also says that redemption is possible. So an anti-Christian would be someone who argues to hate your enemy and that redemption is impossible, that bad people remain forever bad. So I would ask you, which position is better suited to an age of apocalyptic weapons? What do you do if one side does not profess those views and you claim to be a Christian? Must you adopt the views of your adversary or the views advocated by the founder of your religion? You can also ask, which position is uniformly embraced by the nation-states? The answers to those questions are very clear. There is no nation that adopts the Christian position on this issue. Not one. There's 140-some-odd nations on the Earth. As far as I know, not one of them takes a Christian point of view. There may be some perfectly good reasons for that, but it's remarkable that there are nations that take great pride in their Christian tradition that nevertheless do not see any contradiction between that and their attitudes on nuclear war.

By the way, this is not just Christianity. The Golden Rule was uttered by Rabbi Hillel before Jesus, and by the Buddha centuries before Rabbi Hillel. It is involved in many different religions. But for the moment let's talk about Christianity. It seems to me that the admonishment to love our enemy must be something central to Christianity; it's that strong statement of the Golden Rule that sets Christianity apart. There were no qualifying phrases that said, "Love your enemy unless you really don't like him." It says love your enemy. No ifs, ands, or buts. Now, political nonviolence has worked wonders in our time. Mohandas Gandhi and Martin Luther King Jr. achieved extraordinary, and for many people counterintuitive, victories. It might even be a practical, novel, certainly breathtakingly different approach to the nuclear arms race. Maybe not. Maybe it's flawed and hopeless. Maybe the Christian point of view on this issue is inappropriate to the nuclear age. But isn't it interesting that no nation of Christians has adopted it? The Soviet leaders do not profess to be Christians, so if they do not pursue the path of love, they are not inconsistent with their beliefs. But if the leaders of other Western nations profess to be Christian, then what course of action should they be engaged in? Let me stress I don't necessarily advocate such a policy. I don't know if it would work. It may be, as I say, hopelessly naive. But should not those who make conspicuous public displays of their devotion to Christianity follow what is certainly among the central tenets of the faith?

"Do unto others as you would have them do unto you" has a corollary. Others will do unto you as you do unto them. And that encapsulates, among other things, the history of the nuclear arms race. If this can't be done, then I think politicians who are practitioners of such religions ought to confess and admit that they are failed Christians or aspirant Christians but not full-fledged, unqualified, unhyphenated Christians.

I therefore think that the perspective of the Earth in space and time is something with enormous, not just educational but moral and ethical, force. I believe it is lucky for us that this is the time when pictures of the Earth from space are fairly routinely available. We look at them on the evening weather reports and hardly pause to think what an extraordinary item that is. Our planet, the Earth, home, where we come from, seen from space. And when you look at it from space, I think it is immediately clear that it is a fragile, tiny world exquisitely sensitive to the depredations of its inhabitants. It's impossible, I think, not to look at that planet and think that what we are doing is foolish. We are spending a million million dollars every year, worldwide, on armaments. A million million dollars. Think of what you could do with a million million dollars. A visitor from somewhere else-the legendary intelligent extraterrestrial- dipping down to the Earth and inquiring what we are about and finding such prodigies of human inventiveness and such enormous fractions of our wealth devoted not just to the means of war but to the means of massive global destruction- such a being would surely deduce that our prospects are not very good and perhaps go on to some other, more promising world.

When you look at the Earth from space, it is striking. There are no national boundaries visible. They have been put there, like the equator and the Tropic of Cancer and the Tropic of Capricorn, by humans. The planet is real. The life on it is real, and the political separations that have placed the planet in danger are of human manufacture. They have not been handed down from Mount Sinai. All the beings on this little world are mutually dependent. It's like living in a lifeboat. We breathe the air that Russians have breathed, and Zambians and Tasmanians and people all over the planet. Whatever the causes that divide us, as I said before, it is clear that the Earth will be here a thousand or a million years from now. The question, the key question, the central question-in a certain sense the only question-is, will we?