THE BALANCE OF NATURE

CHAPTER 10B

THE BALANCE OF NATURE

This is not to say that we are always looking out for the interests of the species, few of us are. But then we are practically never looking out for the interests of a stranger, although if we see him collapse on the street many of us would feel a strong impulse to come to his assistance. Similarly, the appropriate time to recognize the interests of the species is when we become aware that they are threatened. And in any event, insofar as we accept the responsibility of deciding for the species, the argument that ought to work is that which takes the interests of the species into account.

I think that the social critics should be, on the whole, very well satisfied by now. But the ideological critics are a different matter altogether. They may agree, though grudgingly, that given the present situation space science provides a possible solution. Or even, that given the present dilemma, space science looks essential. Nevertheless, they may want to challenge the description of the dilemma and insist on a solution more to their liking. And their alternative is this. Space science looks imperative because of the enormous pressure that the incredibly large population is putting on the environment, particularly when that population demands increasingly larger per capita shares of energy and other resources. But is it not obvious that if our numbers were significantly reduced, and our demands for consumption lowered, then the pressure on the environment would be relieved?

Suppose that we institute programs that would lower the total population of the planet. First we cut it in half in fifty years. With other measures that would involve a simpler standard of living and reduced energy consumption per capita, this would certainly accomplish much to make our problems manageable. Suppose then that we continue to cut in half the population of the Earth every fifty years, until after a few centuries the impact of humans on the environment is no longer a threat to the entire planet. China is already taking stern measures to reduce its population drastically. It seems, then, that there are alternatives to the exploration of space.

Now, how could such a momentous decision to reduce population be implemented on a global scale? The amount of coercion in China is considerable, in spite of the fact that China is a relatively homogenous society in which a dominant political ideology facilitates near unanimity of opinion. But I am not sure it is reasonable to suppose that anything short of widespread and unmitigated disaster could bring together the different hostile factions in the world to put such a global program into effect. The disaster may come. Although by then it might be too late. And even if the struggle could still succeed, the misery visited upon mankind may be too high a price to pay, particularly if space exploration could have kept disaster at bay. It does not seem like much of an alternative after all.

And what leverage would the Wendell Berrys of the world employ to launch the conflicting powers that be on a joint enterprise of such monstrous proportions? Surely not moral persuasion and enticements to instill what he calls good character. Appeals of that sort would not have a prayer, at least not in time to avoid the disaster which gives such views an air of reasonableness, however they may have to be accompanied by resignation. So it is unclear just how feasible this ideological alternative is, but two considerations would seem to buttress this position. The first is that we have to do something about the population growth anyway. Space exploration will not be in a position to play a significant role in the reduction of the Earth's population for a long time. If we could take a million people a year into space, which we cannot at the present, it would take thousands of years before we began to make a dent in the amount of population we have now, let alone on a population that is growing at today’s dangerous rate. We have centuries, at the most.

The second consideration is that we better protect the Earth by nurturing respect toward it than by letting people think that we can always move onto another nest. For otherwise we imagine that spoiling our present nest is regrettable but not an insurmountable loss. Learning to live within the confines acceptable to our mother planet is a wiser policy because we already know that we can lead dignified and fruitful lives here. By contrast, learning to live in space is only a promise. Can we bet the future of mankind on it? The greatest gift we can make to posterity is a beautiful Earth and the strength of character to live in harmony with it. In other words, we accomplish more by preserving the natural balances that have been so accommodating to human beings in the past, and by restoring such balances where modern life has already disrupted them. The result of exercising greater moral responsibility toward the world is a better world.

Space exploration, on the other hand, presumably would continue the disruption of the natural balance. If technology has already caused a mess, why should we expect better? Moreover, space exploration would be worse than a necessary evil, for it is not an enterprise that we can engage in just once before returning to a more pastoral existence. As Berry says, in condemning the scientific mind, "(1) It would commit us to a policy of technological `progress' as a perpetual bargaining against `adverse effects.' (2) It would make us perpetually dependent on the `scientific' foretelling and control of such effects -- something that never has worked adequately, and that there is no good reason to believe ever will work adequately." Why could it not work? Because "when you overthrow the healthful balance of the relationships within a system --biological, political, or otherwise -- you start a ramifying sequence of problems...that is not subject to prediction, and that can be controlled only by the restoration of balance." Berry's warning is that "if we elect to live by such disruptions then we must resign ourselves to a life of desperate (and risky) solutions: the alternation of crisis and `breakthrough' described by E.F. Schumacher."[1]

How reasonable an alternative is this to the course of action I have recommended? The first thing that deserves comment is this matter of disruption and restoration of balance. A very early and rather important disruption of natural balance took place when life was born and changed the chemistry of the planet. Another crucial and massive disruption of balance came when the oxygen liberated by life "poisoned" the atmosphere and the oceans. And this was followed by the adaptation of life to oxygen, with the subsequent destruction of the cozy arrangements between early life and the environment. Disruptions of similar magnitude were brought about by the appearance of complex organisms, by the formation of an ozone layer, which made the land available to life --would it have been better for life to stay in the oceans? -- and then by the return of vertebrates to the water, which led to whales and dolphins. Ever since, the evolution of life has created new forms that have remade the environment anew, destroying the very memory of whatever balance had been struck previously, and leaving at best a few scattered fossils of what the Berrys of the time would have insisted on preserving.

The fact of the matter is that life has often created new opportunities for itself, unwittingly no doubt, and has always changed the balance between its different forms --most of which are now extinct. The biota of the planet has remade itself many times over. The natural balance of the ideological critics is merely a fiction, a temporary arrangement that would change even if there were no human beings around to mess things up. And surely life does not exhaust the range of natural causes that have brought about massive disruptions of balance. Do volcanic eruptions, droughts, and asteroids always make for small reversible changes? What may we say, incidentally, of the galactic disruption that forced the collapse of the pre-solar cloud into a planetary system? Of the earlier obliteration of what may have looked like states of cosmic equilibrium, and thus of natural balance? Which balance is it that we are morally obliged to restore?

Clearly humans are not the only creatures that transform their environment and interfere with it. R.C. Lewontin, S. Rose, and L.J. Kamin point out that "all living beings both destroy and create the resources of their own continued life. As plants grow, their roots alter the soil chemically and physically. The growth of white pines creates an environment that makes it impossible for a new generation of pine seedlings to grow up, so hardwoods replace them. Animals consume the available food and foul the land and water with their excreta. But some plants fix nitrogen, providing their own resources; people farm; and beavers build dams to create their own habitat."[2]

The issue is not, then, one of disrupting balance and interfering with the environment. Perfect balance can be found only right before the birth of the universe and perhaps right after its death. Even then we do not really know. And to avoid interfering with nature would be out of character for living things, while impossible to achieve anyway. The issue is rather one of interfering wisely, and of preserving (approximately) certain balances that offer the best compromises for a worthwhile existence on this planet. But how are we going to achieve these goals without the kind of global and long-term knowledge that we have discussed in this book?

To say that we should diminish the presence of man--in numbers and in scope of action--so that nature may run its course as undisturbed as possible, assumes that man is a scourge upon the land, and it denies man the very liberties we give to the rest of living things. But even so, how far should that diminution go? And at what price in human misery? I think that this attitude, to force man back, also assumes that there can be no middle ground between the obliteration of the environment and the reduction of man to insignificance. For at any place in the middle we will see a rather large human interaction with the environment. We are sinners, it appears, and now the time has come to pay for our sins. Without this general mea culpa in the hearts of the large majority of human beings, it is difficult to see why they should act in what surely will seem to many as directly against their interests and those of their descendants. Should we not instead gain knowledge of the world in order to determine what is wise? No. These critics would rather do penance than science.

Nevertheless, as long as our dealings with nature involve a creative element, as long as the transformation of the environment is inevitable, with or without our participation, it seems more sensible to learn the secrets of nature so we can act with our eyes open. Berry and his cohorts may not think highly of many of the opportunities that space exploration may open to us. But why should they bar others from taking advantage of them? What right do they have to decide for others what good character is and to insure that nothing else will have greater priority? Their case is based on a myth about nature. And that is only half the trouble.

The present rate of population growth may well be unsustainable, and for space exploration to make a difference it would have to provide means of carrying billions of people into space, a feat that is not in the cards in the foreseeable future, although eventually it will. In the meantime, space science may help us monitor the pressure on the environment and avail our planet of the resources of the solar system. Moreover, let us remember that in the long run the workings of nature, if man does nothing about them, are bound to create first a most unpleasant world for our descendants and then bring extinction upon them. Having science is no guarantee that those things will not happen. We cannot be assured that the desired level of knowledge is possible within whatever time limits infringe on our future. Nor can we be certain that just because we have that knowledge we will choose according to the best interests of the species. But we can be sure that, without the global knowledge that requires space science, we will simply have no choice to make. Our descendants will suffer for it; and eventually our species will disappear at the earliest cosmic inconvenience.

A species full of self-hatred may well choose such a path. But is the appeal of presumed atonement the most fitting choice for us to make? That ascetic choice may buy us a bit of time, but for what? In the long run it leads us straight into a grave. The other choice, the one that really lets nature run its course offers the opportunities for expansion and diversification that so far life has been fortunate to procure for itself. I refer to it as the one that really lets nature run its course because it recognizes that we, too, are part of nature. There is no question in my mind that in this case the way of nature has the potential for greater wisdom.

Sometimes it is said that a little bit of knowledge is dangerous, and that since we are not likely to have complete knowledge through space or any other kind of exploration, we are better off not embarking on this scientific enterprise in the first place. But we have seen, clearly I hope, that even though a bit of knowledge can be dangerous, there is no long future in ignorance.

My point is not that environmental concerns are unimportant. Just the opposite. They are very important and we should take the steps necessary to make decisions based on the most comprehensive picture of the Earth's environment we can obtain. Only then we can pay proper attention to the interests of our species. What I argue against is the rigid demand to act on myths about nature that have little more than mysticism in their favor.

The decision is, of course, not mine to make. My intent has been to bring before the reader the considerations relevant to these large issues and the arguments that are most suitable to them. I hope I have shown that the very heart of space exploration contains within it the best justification of the entire enterprise. In doing my small part to reduce the dimming of starlight, I trust that, as H. G. Wells said, “Life, for ever dying to be born afresh, for ever young and eager, will presently stand upon this earth as upon a footstool, and stretch out its realm amidst the stars.”[3]

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[1] Op. cit., p. 83.

[2] Lewontin, R.C., S. Rose, and L. J. Kamin. Not in Our Genes: Biology, Ideology, and Human Nature (New York: Pantheon Books, 1984).

[3] H. G. Wells, The Outline of History, 1920, from www.spacequotes.com/.

Chapter 10A Again

I was unhappy with my previous posting, and so I decided to rewrite it and add to it the material I had planned to post today.

CHAPTER 10A

THE VALUE OF HUMAN SURVIVAL

H.G. Wells said once that our choice is the universe or nothing.[1] And if the argument of this book is sound, he was not that far off the mark. The way humans look at the world, the way they interact with the world, gives them a panorama of problems and opportunities that will change as they strive to satisfy their curiosity: a dynamic science leads to a constantly evolving panorama. To grow is to adapt to a changing environment or to a variety of environments. Given the long-term prospects of the human species, to grow scientifically, into the cosmos, is to hedge our bets against extinction.

Two important questions come to mind at this stage. The first is: why should survival be a value? In particular, why should human survival be a value? If we justify space exploration by reference to survival and to the material improvement of human life, the social critics should be satisfied. Their objectives, in the long run, require that we go into space. But some of the ideological critics may prove more ornery. Thus Wendell Berry supposes that the abundance of resources in space will produce bad character, for good character requires the discipline of finitude.[2]

That the survival of the human species is a value may seem beyond question to most of us, although there might be some who prefer extinction to bad character (not that I wish to suggest here that Berry would go that far) or to decreased chances of spiritual salvation. But even overwhelming agreement on the value of survival might not satisfy some thinkers in their more philosophical moments. It seems that we value survival very highly, they might say, but why should we so keen on leaving behind imperfect creatures much like ourselves?

In such philosophical moments, questioning a value is normally taken as a demand to identify some other, more basic value from which the first one is derived. This is similar to how we presumably justify actions: "This is the right action because it will bring about X and X is a good thing." But the more basic value (or good thing) that does the justifying can itself be questioned, so we then look for an even more basic value (or good thing) until eventually we arrive at a good thing that is not merely good but good in itself, that is, whose goodness does not depend on anything but its own nature. Why do we work? Because we get paid? Why is money a good thing? Because we can use to buy food and clothes, pay the rent, etc. Why do we want to do those things? Because they make us happy. And in happiness, Aristotle thought, we find an end that is complete and self-sufficient.[3] The question “why do we want to be happy” makes no sense. Aristotle had in mind not transient happiness, but a happy life as a whole. He also thought it was obvious that the happiness of a society was of greater value than the happiness of a single individual. Of course, there seems to be a clear connection between human happiness and human survival.

Since this approach grounds ethical justification on a human value, human happiness, some may object that it is therefore relative to our own species. This objection seems to underpin the notion that we should not prefer the good of our own species to that of other living things in our planet, or even to the rocks of another planet. Oftentimes the objection is expressed as the view that ethics and other disciplines of value are "objective" only insofar as their laws are eternal and universal. As characterized by Peter Singer, who criticizes it, the view claims that "The laws of Ethics...existed before there was life on our planet and will continue to exist when the sun has ceased to warm the earth."[4] Moreover, eternal (absolute) laws of ethics seem to demand eternal (absolute) values. Thus a relative value such a human happiness (or human survival) cannot provide an adequate justification for our actions.

Absolute values, however, are not all they are cracked up to be. Conflict may arise between two or more absolute values. Or an absolute value may be of small significance in a particular context and thus should yield to relative values. Besides, absolute laws could in principle be derived from values that always depend on context or on subjective preference, i.e. relative. For example, consider utilitarianism (i.e., roughly, the view that the balance of good vs. bad consequences of an action--its utility--determine its rightness, given the utilities of the alternative actions). At least one version of utilitarianism would calculate utility in accordance with the values assigned by the individuals who would enjoy or suffer the consequences of the action being contemplated.[5]

I need not show that human survival is an absolute value, or that there must be an absolute law of ethics that gives survival a very high priority. I appeal to it in order to show that space exploration is in the interest of the species. When I point out that space exploration can save us from the dangers posed by asteroids and the sun’s becoming a red giant, I give a strong reason to pursue it.

A reason in matters of prudence, or of ethics, need not be one that appeals to an absolute ground of any kind. A reason must be a reason for action, and so it must be aimed to convince the intended audience. This is not to say that efficacy alone is sufficient to commend reasons. The fallacious reasoning of much advertisement may well appeal to the masses of the unwary but would be exposed to ridicule in less superficial disputes. In some polemics the stakes and the standards may be very high. This need not mean that some ideal is approached but that greater care must be exercised to take into account the sorts of considerations that may be brought up by all the parties concerned. And greater care must be exercised not because some of those parties are in possession of truly higher standards of reason or have a more direct line to the truth – they might or might not – but precisely because we have more perspectives in play, because their diversity demands a sharper, more comprehensive case if their potential objections are to be met.

To give ethical reasons to someone is then to give him reasons that take his concerns and interests into account.[6] In discussion with members of another society, we can hardly make way with claims to the effect that our customs are better than theirs because ours are ours, or because our customs appeal to us. A convincing argument would have to show them that, in some respect that they may come to see as important, our customs work better for us than theirs do for them. Or if what we really want is for them to adopt ours, we must show them that our customs will work better for them, too. If action is the intended goal of reason in matters of prudence and ethics, how can reason succeed if it cannot appeal to the audience? And what appeal can there be where the aims, desires, and interests of the audience are ignored?

In an important respect this view preserves an element of universality, although not the peculiar ground of objectivity of so many views in ethics. As the Oxford philosopher J.L. Mackie put it: "If there were objective values, then they would be entities of a very strange sort, utterly different from anything else in the universe. Correspondingly, if we were aware of them, it would have to be by some special faculty of moral perception or intuition, utterly different from our ordinary ways of knowing everything else."[7] No. The element of universality depends rather on the realization that, as Singer says, "… one's own interests are one among many sets of interests, no more important than the similar interests of others."[8]

Where the only relevant difference between my wish and yours is that it is mine, I am generally not in a position to give you reasons why you should behave as I want you to. An intelligent being should presumably be able to detect what the relevant factors in a dispute are, and discard those that are revealed as arbitrary. Or else he would go ahead with the full knowledge that his case is also arbitrary and that he has no rational claim upon the behavior of those he was trying to persuade. Practical reasoning that will not treat impartially the interests of all parties will not succeed: It cannot motivate action.

These considerations lead Singer to conclude that all rational beings should come to this process of reasoning. If so, this reasoning would have an eternal and universal aspect. For according to Singer, "Wherever there are rational, social beings, whether on earth on in some remote galaxy, we could expect their standards of conduct to tend toward impartiality, as ours have."[9] This is not to say that all rational beings would adhere to the same specific norms of conduct, for those specific norms may have developed to meet entirely divergent constraints on behavior, as we already saw in Chapter 8. Nor is it to say that ethical behavior between all intelligent species is possible, since such behavior requires a possible commonality of interests that may not always be there (such commonality need not be of prior interests, since in new circumstances complex intelligent beings are capable of developing new interests; although there is no guarantee that new, appropriate interests will in fact be developed).

In this manner we can explain why the appeal to values is thought to provide reasons, for values themselves, as Singer points out, are inherently practical. "To value something," he says, "is to regard oneself as having a reason for promoting it. How can there be something in the universe, existing entirely independently of us and our aims, desires, and interests, which provides us with reasons for acting in certain ways?"[10] When I point out the connections between space science and survival, I consciously expect that my case will be successful because it does take into account what I believe are the aims, desires, and interests of my intended audience. I assume that most normal human beings care deeply about the consequences that I have outlined. Indeed, since what I am doing is trying to meet the objections of the critics, I ought to be on firm ground, for they very explicitly announce their concern for the welfare of all humankind (at least in the case of the social critics).

Should humans be interested in their own interests? The question does not even deserve to be called rhetorical. What often happens, though, is that reasons that presumably take our interests into account may be challenged on the grounds that they really do not -- that if we consider other relevant factors, or a long view of things, then we realize that what appeared to be in our interest really is not. But how can it be that survival is not really in our best interest?

There are cases where survival clearly does not override other reasons (or motives) for action, and where we may agree that it should not. Cases, for example, in which someone risks his life to save his child's, or a stranger's for that matter. Or cases in which principle takes precedence. But all these are cases worthy of admiration precisely because we recognize that the person's survival was in his best interest, but that he disregarded it for the benefit of a higher purpose.

Moreover, I would venture to guess that the reason we are willing to let personal survival be overridden is that this higher purpose is somehow involved with making life better for those that remain, or even to make sure that others do remain. As this purpose expands in scope, it will ultimately cover the well-being of all mankind. And here we should not speak merely of mankind as we may find it in a slice of history, but mankind as it extends through history into the future.

Religion sometimes demands the sacrifice of lives for rather obscure goals, or for goals that only the faithful find less than revolting. And political passion is often guilty of similar motivations. But it is difficult to see how a religion or a political ideology that demanded, or permitted, the destruction of the entire human species, that would deny the future a chance, could justify itself to the most general of audiences. Even so I am not inclined to say that no conceivable set of circumstances could provide a reason more pertinent than the survival of mankind. Still, such a strict requirement is not necessary. I presume to have given good, convincing reasons. Unless someone offers stronger alternatives, I would like to think that I have done enough in this respect.

The previous point is that the line of argument that culminates with a connection to our survival and the betterment of our material condition need not go to a deeper level of justification. This point was clearly aimed at a philosophical critic who might question the ground of justification I provide for the exploration of space. Nevertheless I have not yet earned the right to bring the discussion to an end. First of all other critics may wonder about the appeal to the interests of humanity, not because appealing to interests is not enough but because they may think that "humanity" is too elusive a subject to have interests. And second, some of the ideological critics may resist the conclusion that space science is necessary for the long-term survival of the human species.

The first objection is less powerful than one may imagine. Of course, our species is not some kind of super-organism of which individual human beings are the cells. There is surely no talking to any such "humanity". Humanity in a clear sense does not think what is best for it, nor does it recognize its interests, simply because there is no conscious subject there to think or recognize. Individual human beings do the thinking and recognizing. That is fair enough. Moreover, the interests of human beings are individual interests, what do they have to do with the interests of humans who may live several million years hence? How compelling can that appeal to the future be? How compelling should it be?

I would like to offer two responses, one rhetorical and the other philosophical. The rhetorical response is this. If my aim is to meet the objections against space exploration by the social and ideological critics, this particular point can do little against my case. For those objections cannot even get off the ground unless we assume first that it is not only possible but also our duty to do what is best for humanity. That is, we recognize that we should act not only so as to ensure our own well being but that of others. The audience, in a figurative but still important respect, are the people of the Earth. If that were not so, what would be the point of arguing that combating poverty is more important than observing the X-ray emissions from the vicinity of possible black holes? Or of suggesting that science is not wise because in the long run it will bring us to grief? The "us" here are surely not those of us who may hear the warning when first issued, but those in posterity whose world we may swindle by our recklessness of today.

And now we can move from the purely rhetorical to more general or philosophical remarks. The reason the objections of the social and ideological critics do have a leg to stand on, although they turn out to be ultimately mistaken, is that as a matter of fact we do decide for posterity to a great extent. We may plant the trees from which “our” descendents will receive nourishment and shade, or we may destroy what could have given them a fighting chance against drought and famine. It is for them to make their own decisions, but at least the initial situation in which they will find themselves is more of our making than of theirs. Nor should we think that a society is merely an aggregate of individuals, and the species an aggregate of societies. Even if there is no super-organism, the whole does amount to more than the sum of its parts. Society is not a mere statistical distribution of individual properties. An individual that belongs to a society has characteristics that he could not have by himself. An advanced scientific and literary society, for example, builds libraries, universities, and laboratories, which enable an individual to educate himself for a style of life that would not exist without those institutions. The choices and opportunities open to him are not those that we could have without the benefit of the past efforts of generations that brought about the world into which he was born. No one could choose to be a modern farmer without the technology this century has provided, simply because the things a modern farmer does would not be possible otherwise. Nor could one choose to be a goalie in a soccer team if the game did not exist. In a primitive society it is very difficult to become a scientist, or a movie actor, or for that matter an effective critic of technology, since he will have little acquaintance with it. And in some societies dominated by religion, the female half of the population do not have the right to drive a car, receive an education, or even show their faces.

What we are, what we may become obviously depends on our own efforts and talents. But it also depends on the range of choices, on the freedoms, and on the starting points that our society and culture make available to us. We do not become ourselves in a vacuum. But we also change the society by our choices, and thus we change the face of posterity, and sometimes its very substance. Some may wish to deny that our dialectical relationship with society imposes on us obligations of gratitude. But with a bit of attention, even they should realize that the present generation does decide for mankind, whether unwittingly or not. And they should realize also that the choices we face today are particularly important, more so perhaps than the choices most other generations of humans had to make. Nor is my case aimed strictly to the present generation. Now that space exploration has become a feasible alternative, these controversies have only been born.

Survival of the species is not a value just because it is in accordance with evolution. In the first place survival is not the goal of evolution. Evolution has no goals. And besides that, most species that ever lived are now extinct. Survival is a value to us because without it all the other interests of the species may become moot. And even though the interests of many individuals do not depend on the survival of the species, their collective actions often affect the species as a whole-- and when they recognize this, they care how it all comes out in the wash.

According to some important contemporary views influenced by biology, it is in the nature of human beings to care about the fate of their descendants. This tendency can be explained by the comparative study of life forms and their drive to insure that their genes remain in the world even after they themselves are gone, and especially by the mechanism of kin selection and its concomitant kin altruism. But even if some are suspicious of such sociobiological studies and would rather speak in terms of culture, it would be difficult to deny that survival is in the interest of the species, or that our actions today may affect that interest tomorrow. Knowing that, it is a pretense to argue, as some fanciful philosophers do, that since future generations are not yet born, they do not have rights (for they are not “real”), and therefore we cannot be said to have obligations towards them.[11] Were they correct, I could not be accused of mass murder if I were to leave a large bomb hidden under the floor of the newborn wing of a hospital, timed to go off in six months, since none of my future victims would have been born by the time I hid the bomb.[12] Nor can I leave the bomb there even if I did not plant it myself. Thus we do have obligations to ensure that CFCs no longer destroy the ozone layer so that our grandchildren will not suffer in large numbers from skin cancer. And we also have a positive obligation to put in place space systems to warn us of asteroid impacts and to deflect them, lest our descendants go the way of the dinosaurs.

This is not to say that we are always looking out for the interests of the species, few of us are. But then we are practically never looking out for the interests of a stranger, although if we see him collapse on the street many of us would feel a strong impulse to come to his assistance. Similarly, the appropriate time to recognize the interests of the species is when we become aware that they are threatened. And in any event, insofar as we accept the responsibility of deciding for the species, the argument that ought to work is that which takes the interests of the species into account.

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[1] Taken from Carl Sagan in http://www.imdb.com/title/tt0081846/quotes?qt=qt0317500.

[2] See Berry’s contributions to Space Colonies, ed. by Stewart Brand (New York: Penguin Books, 1977), pp. 36-37 and 82-85.

[3] Aristotle, Nicomachean Ethics, Bk. 1, Ch. 7, 2^nd Edition, translated by Terence Irwin (Indianapolis: Hackett Publishing Company, 2000).

[4] Peter Singer, The Expanding Circle: Ethics and Sociobiology (New York: Farrar, Strauss and Giroux, 1981), p. 105.

[5] Many utilitarians, however, assign to pain and pleasure absolute values, positive or negative respectively.

[6] In this I follow Singer in his The Expanding Circle, op. cit.

[7] Quoted in Singer, ibid., p. 107.

[8] Ibid., p. 106.

[9] Ibid.

[10] Ibid., 107.

[11] Robert M. Adams, "Existence, Self-Interest, and the Problem of Evil," Nous I3 (1979): 57. Derek Parfit, "On Doing the Best for Our Children," in Ethics and Population, ed. Michael Bayles (Cambridge, MA: Schenkman, I976), pp. 100-102. Thomas Schwartz, "Obligations to Posterity," in Obligations to Future Generations, ed. Richard Sikora and Brian Barry (Philadelphia: Temple University Press, I978). For a discussion see Robert Elliot, “The Rights of Future People,” Journal of Applied Philosophy 6, no. 2 (1989): 159–69.

[12] Presuming that I time it so precisely that no nurses or visitors will be killed.

SPACE TECHNOLOGY AND WAR

CHAPTER 9A

SPACE TECHNOLOGY AND WAR

One of Rousseau's complaints against the arts and the sciences was that they weaken the military might of a society. "All examples teach us," he said, "that in military affairs...study of the sciences is much more apt to soften and enervate courage than to strengthen and animate it." Perhaps it was still possible in the 18th Century, when he wrote, to believe that the sciences were luxuries of no practical military consequences -- although even then the new science had brought great advances in ballistics and other military fields. Today those who share Rousseau's suspicion of science do so for different reasons. He worried that science made us if anything less formidable. They worry that it makes us far too formidable.

The proponents of space exploration generally have a benign view of what the enterprise has to offer, although it is not uncommon to see space activities funded precisely because some military advantage is likely to result from them. The serious objection is not, however, that there is a connection between space technology and the military, for after all there have been times when helping the military was the right thing to do (fighting against Hitler, for example). The objection is rather that space technology puts into the hands of man tools that he cannot fail to mishandle. There is an evil side to man, and so whatever discoveries science makes will eventually visit pain and misery upon the human race. Space science and its accompanying technology are no exception. If anything they confirm the suspicions against science in general. Is it not true that rockets have been used to kill and terrorize in the past? Is it not true that for decades they were the very means by which the entire planet could have been brought to nuclear annihilation at a moment's notice? Are they not still a great threat today?

The point is not merely that there is a connection between space and grief. The point is rather that the connection is somehow unavoidable, that you cannot have one without the other. Thus, the more space technology progresses, the more acute the grief. This far more sweeping claim requires that we look into the history of space exploration and its likely future for clues of such inherent connections with destruction and evil. Indeed we must keep in mind that this claim often gains plausibility in the first place because of appeals to history -- mainly to the role of the German V-2 rockets in WWII and of the intercontinental ballistic missiles during the Cold War.

The need to examine this objection in a historical context cannot be stressed too much. Some may argue that the relevant issue is whether space technology will make war inevitable in the future, whatever its role might have been in the past. But this line of argument operates in a rhetorical vacuum. An estimate of the contribution of space technology to war should presumably be supported by reasons, by an account of the causal and probable connections involved. And how are those reasons going to be assessed? On their merits, one might hope. But what are their merits? What makes causal and probable connections plausible in the first place? I submit that these difficult matters are most often influenced by the way we have learned to judge. And what has determined that learning if not our perception of how similar matters have been resolved? We appeal, that is, to our experience, and in the last analysis, to history. At the very least a brief look at history is necessary, then, to unearth assumptions which otherwise may be innocently smuggled into appraisals of the future.

The wish to explore beyond the confines of our own world is very old. By 180 AD it received full treatment in Lukian's Vera Historia (True History), in which travelers go to the Moon when a giant whirlwind picks up their ship from the ocean. In 1634 the famous Johannes Kepler wrote Sleep, a novel about a trip to the Moon. With the advent of the industrial revolution, several would-be inventors tried their imagination at mechanical contraptions that could turn such trips into more than dreams, although their colorful ideas had little to do with the actual development of rocketry many decades later. In Russia there was Kibal'chich, who spent his time designing explosive devices and rocket aircraft, while ignoring his trial for blowing the Czar to bits in 1881. In Germany there was Ganswindt, who worked on a hopeless steam jet to propel his spacecraft. And everywhere there were fiction writers taking their readers on trips that engineering could not yet make available.

The theme of space travel was in the air, and around the turn of the century the real pioneering work was finally carried out. By then science and technology had caught up with the old dreams to the point that not one but three independent investigators provided the foundation of space rocketry. The Russian Tsiolkovsky was the earliest, then came Goddard in the U.S., and finally the most influential of them all, Oberth in Germany. The first thing these three men had to do was show that space flight was indeed possible. Their solution to this problem, as we will see, has some bearing on the issue of whether inherent connections exist between space technology and devastating war. And the problem was that, to many “experts” at the time, space flight seemed not merely far fetched but physically impossible. Some disheartening calculations, for example, showed that however efficient the production of thrust, no rocket could raise its own mass into orbit. But as the pioneers showed, even the most sophisticated impossibility proofs could be gotten around by the very simple but ingenious idea of using multi-stage rockets. The first stage gives the whole rocket an initial boost and then separates. At that point a second stage takes over the task of pushing a lighter vehicle with a now shorter distance to climb. One or two more pushes like that and the rocket achieves orbital velocity.

A second barrier was overcome by the switch from solid to liquid fuels. Standard rockets generally used solid fuels, mostly gun powder, which lacked both the power and the control required for space flight. Tsiolkovsky and the other pioneers soon realized, however, that several mixtures of liquid propellants, particularly hydrogen burned with oxygen, could give rockets the desired performance. This is of particular importance to our question, as we shall see. Now, a quick comparison of liquid and solid fuels shows how right Tsiolkovsky was -- a most remarkable feat for a self-taught man who never gained entrance to the scientific or engineering circles of his day. Liquid propellants liberate more energy per pound than their solid competitors. (The following figures were given by John Shasta of the American Rocket Society in 1936, and appear in William S. Bainbridge's book The Spaceflight Revolution, from which most of the following account is taken). The best powder achieved 1870 BTU's; a mixture of methyl alcohol with oxygen, 3030; while hydrogen and oxygen combined gave 5760. Even in contemporary times the differences are pronounced: The solid fuel in the typical military rocket of the 1970's produced in principle an exhaust velocity of 2250 meters per second (m/s), a figure inferior to the 2750 m/s that Goddard had actually achieved with his small rockets decades earlier, and much below the 4200 m/s obtained by burning hydrogen with oxygen. At least until recently, the best that could be hoped for in future solid fuels did not measure up to the performance of liquid fuels in this respect.

In the second important respect, control, the differences are just as pronounced. The difficulty with a solid propellant is that it tends to burn until it is exhausted. You cannot just shut it off and start it again. In a liquid system, on the other hand, you may always control the amounts of fluids intervening in a reaction -- you may increase it, decrease it, or turn it off altogether. And you can open the valves again and thereby restart the combustion that gives you the thrust. This fine control permits the appropriate accelerations at the appropriate times to maneuver the rocket into the desired orbit. And although the techniques to achieve this control were not easily acquired by rocket developers in the decades that followed, there was now a clear direction of research, as well as good reasons to think that the problems could be solved.

The three pioneers also provided basic formulas for engine performance and specified likely vehicle trajectories. Now the goals were clarified, and so were the means for attaining them. Nevertheless, the move toward space did not quicken its pace for a long time. The few who were technically competent and who took the trouble to read carefully the works of the rocket pioneers may have realized the potential involved. But most technically qualified people regarded the topic with suspicion and did not bother themselves with an investigation of it. There is nothing conspiratorial or shortsighted in that attitude. Any scientist may well be bombarded with a myriad of ideas that he himself has not examined in detail. Which ones should he explore? Not all of them. He cannot. And surely not those that strike him as implausible or without foundation. Time is too short for that. Science changes because not all scientists are cut of the same cloth, and thus what seems preposterous to the majority may instead strike a resonant chord in a few others. Most beginnings are therefore small, and the development of space technology was no exception.

The dreams of the pioneers were left for others to realize. Tsiolkovsky remained undiscovered and ignored. Goddard was very secretive about his own work. As Bainbridge points out, "He did not publish an account of his first 1923 engine firing until 1936, when the V-2 was already taking shape on German drawing boards. Complete reports of his experiments in the 1930s were not published until 1961, the year that Yuri Gagarin orbited the Earth." This situation was apparently more the result of his peculiar temperament than anything else. According to Bainbridge, "Goddard tended to ignore the work of other men in the field, was remiss in his correspondence with colleagues, refused to share his results, and would not participate in joint projects. He seemed to want to achieve successes...then burst upon the world in triumph." But one man alone could not achieve what took the efforts of many thousands. Such were the first quirky steps in the strange journey that took us to the Moon.

As interesting as the lives and motivations of these men were, an account that would do them justice is beyond the scope of this book. For our purposes, it is enough to say that those motivations had more to do with the liberation of the human spirit, with its excellence, than with the destruction of other human beings. In Oberth's words: "...probably Mankind will even build spaceships sometime, make other planets habitable, or even establish habitable stations in space, and having become morally mature in the meantime, will bear life and harmony out into the cosmos."

Oberth presented his masterwork The Rocket into Interplanetary Space as his doctoral dissertation in 1922 (Goddard's crucial theoretical work preceded his by ten years, and Tsiolkovsky's by twenty). He was turned down with the advice to look for a more suitable topic. He refused, and then proclaimed that he could become a greater scientist than his examiners, "even without the title of doctor." His arrogance was not entirely misplaced. Within a year he had published his book, of which Arthur C. Clarke has said that it "may one day be classed among the few that have changed the history of mankind." In any event, it became not only a source of inspiration but also the textbook for the German rocket experimenters. One such group, founded in 1927, the VFR--Verein fur Raumschiffahrt (Society for Space Travel) -- was to prove of crucial importance.

The Value of Human Exploration

Chapter 7C

The Value of Human Exploration

Still, the proponents of manned exploration have a point – or rather, several. First, they might just as well acknowledge that the Shuttle has set space science back many years. Even the head of NASA thinks it was a mistake.[1] But they might point out that the Shuttle is a very poorly designed system, not a good example of how manned exploration should be done. It is essentially a very large and heavy glider taken into low orbit by a partially reusable combination of solid and liquid fuel propulsion engines. It is at its worst when it ferries satellites into orbit, a task to which it was devoted through the 1980s, and for which it is still used. Suppose that I am eating dinner in Tokyo next to a sumo wrestler. Across the dining room a friend asks me for the small pitcher of warm saki. I could get up and take it to him. It would require me to spend a certain amount of energy, but not much, and to incur a certain amount of risk, but not much. Or I could hand the pitcher to the sumo wrestler and then carry him, saki in hand, across the room so he can give the saki to my friend. The energy required is far greater, as is the risk involved, both to the sumo wrestler and to me. Indeed, that is an extremely expensive and unsafe way to ferry satellites into orbit (or carry saki across a dining room). To make matters worse, the Shuttle is an extremely complicated machine, with more ways to fail than anything else that has flown before or since.

Was there a better way to fly people into space? Of course there was. Otherwise we would have never landed a man on the Moon and returned him safely to Earth “before the decade was out” as President Kennedy challenged us to do in the early 1960s. And when we went to the Moon, let us recall, there were also many complaints about the poor quality of the science that was expected to result. Those complaints were very misguided. The Apollo astronauts made great contributions to science, contributions, for example, to our understanding of the origin and evolution of our planet.[2]

That Apollo era saw the flowering of unmanned exploration as well, a flowering that continued through the mid-1970s, until NASA put its rockets in mothballs and forced practically the entire U.S. space program into the coming “space bus” – the Shuttle. That era also gave us a reliable and relatively inexpensive space station, Skylab, which burnt in reentry when its orbit decayed and NASA no longer had rockets to move it into a higher orbit. The Russians, with a somewhat more modest program also based on rockets, had a very active exploration of the solar system and a station of their own: Mir.

So the important question is whether we should explore with people and with machines, as long as we have a sensible means again for ferrying astronauts into space. We could, for example, jettison the shuttle and continue using the Russian rockets until we have a good rocket program of our own again.[3] We could also encourage private undertakings such as Spaceship1, which promise far cheaper access into space for astronauts.[4]

In the meantime, though, we should realize that manned exploration is once again poised to help advance the cause of space science. I am referring to the search for life, or for fossils of life, in Mars. Rovers and other machines are already exploring the planet, finding evidence of water, laying the groundwork for when human geologists and paleontologist finally arrive, for practically all agree that their presence will be needed in this extraordinarily significant endeavor.

THE VALUE OF A PERMANENT HUMAN PRESENCE IN SPACE

The critics' fear is that the space station once again signals the commitment of the country to expensive manned exploration, with glamour winning over substance. I have already argued that there is more than glamour to the presence of humans in space. It is now time to take this argument further. Unless we had money to burn, it is difficult to justify a transcontinental journey to Paris for the sole purpose of sitting at a cafe to watch people go by as we sip a brandy or a cup of cafe au lait. But if we had to go to Paris for some other reason, it would make perfectly good sense to enjoy that aspect of Parisian life as well. Similarly a permanent manned presence in space – even if prompted by reasons of commerce or national prestige – would make feasible a multiplicity of scientific experiments that a society might not be willing to undertake otherwise. My suspicion is, then, that a permanent human presence in space would, if anything, help a new flowering of space science.

I am not here talking about the occasional grandiose project that becomes an end in itself and leaves more memories than it does future avenues of investigation. I am talking about a space station that marks the beginning of the sustained expansion of the human species into the solar system. Since that is the fear, that is the situation I would like to discuss. How can space science be well served by such an expansion during a period of fifty to a hundred years from today?

Since some branches of space science are obviously helped by a human presence, or so I hope to have shown, the issue is how space science as a whole is to be helped. We must consider, then, what effects that human presence will have on space astronomy, planetary exploration, and other areas where the human experimenter is either not wanted or has been traditionally absent. In space astronomy there is a clear initial benefit: the repair and regular maintenance of the large telescopic arrays in orbit. The role of servicing the Hubble visual telescope, for example, requires the ability of astronauts to fly to the telescope and work on it. (While the shuttle was out of commission, space scientists tried to design a robotic mission, but its future is uncertain; if it fails, the Hubble telescope will have its useful life cut short because astronauts could no longer reach it.) A space station would enhance significantly the capacity to support in space astronomical observatories of even larger magnitude (once we build spacecraft that station occupants can use for travel in orbit). This goal can be achieved in the next two or three decades, definitely a period in which humans are not likely to be replaced by their mechanical contraptions.

This role gives but a mere inkling of what humans in space can do for astronomy. As the expansion into space continues, it becomes possible to build even larger observatories that would be too difficult to take up in one piece. And it also becomes possible to place those observatories in many locations away from the Earth, either because of convenience – e.g., on the other side of the Moon, so as to shield them from the electromagnetic interference from the Earth – or simply to increase the baseline of the measurements. And these possibilities point to some aspects of a permanent human presence of potentially far greater significance.

Apart from producing goods that can be used on Earth, space labs and factories can build technology for space itself. There are several ways in which large space structures might be very advantageous, and some of them will merit discussion shortly. But my point goes further. A lot of the technology used in unmanned space flight today has to be built with the problems of lift-off, orbiting, and deployment in mind. It has to meet terrestrial conditions, withstand the accelerations and temperatures involved in the transportation from ground to orbit, its final stage must be fitted to the specifications of the boosters, and then it has to manage in space. But is all this necessary?

Having a technology that can meet all these challenges is no doubt beneficial. But imposing them on all technology and all experiments that go into space is not very reasonable unless there are no alternatives. It is not reasonable because it imposes greater difficulties and cost in design and production. Take the gravitational gyroscopes designed to test some extraordinary predictions of Einstein’s General Theory of Relativity (the Gravity Probe B experiment[5]). To have the spheres suspended you must use thousands of volts on the Earth, and you must design and build the sphere so it can withstand that electrical potential, even though in space the amount of electricity used will be very small. If we could do the experimental development in space, many of these specification problems would be automatically solved. Not that it would pay now to send scientists to do that development in orbit. The point is rather that a massive, permanent human presence in space opens up a lot of possibilities for space science because it would be relatively feasible to undertake them under those conditions.

In this regard planetary exploration can be a clear beneficiary, since the requirements for an interplanetary probe to be launched from space may be far more relaxed. For example, rather flimsy structures may be perfectly adequate in propulsion modules. We could also employ vacuum tubes without going to the trouble of producing a vacuum artificially – indeed without a "tube" at all, just a cathode, anode, grids, and relevant circuitry. And of course the superior semi-conductors and crystals that can be produced in microgravity would be deployed in space technology without some of the costs of transportation up and down the gravity well of the Earth. The point is that once we make ourselves at home in space many possibilities for technological innovation in space will become readily apparent.

This point is made stronger when we realize that it is possible to avail ourselves of the resources of space in the development of such technologies, as well as in the development of products for the Earth. Once in place, a vigorous exploitation of the minerals and energy of the solar system can make important contributions to an infrastructure that may support the routine exploration of the planets. This is not to say that we should commit ourselves to such exploitation at this time. Indeed one of the present tasks of solar system exploration is to determine the availability and distribution of such resources. Nor can we expect to have the complete means for taking advantage of those resources immediately, even if we wanted to. But as our presence in space becomes wider and better established it is reasonable to expect that we will begin to use the native materials. Plans are already being prepared for that eventuality, and so the promise of space may be more fully realized once we make it our environment.

The ability to create very large structures in space, which for at least many decades is likely to require astronauts, will make possible to assemble very large solar sails and other forms of propulsion that will considerably shorten the travel times and increase the distances our spacecraft can travel. That is also going to have a beneficial effect on all of space science.

The urge to explore the solar system must of necessity go hand in hand with scientific exploration. A survey of what Mars has to offer to potential colonists, for example, would require first an extensive scientific survey of Mars. And any plans for setting up such a colony, as well as for the extraction and processing of materials would at the very least challenge our talents in several branches of space science. Eventually advanced science would no longer be necessary for the technology of prospecting and colonization, since a very well tried science will become routine. This is not to suggest that science is always a prerequisite for technology. The industrial revolution was spurred as much by the development of craft as by the great intellectual feats of science. The relationship between science and technology is clearly dialectical – changes in science affect areas of technology, which in turn make scientific change possible, and so on – although just as clearly at any one time there is also a good deal of independence between them. In this case, however, the nature of the exploring to be done has a major scientific component, in that the questions that we need to ask are not different from the kinds of questions that many planetary scientists would like to ask. Thus the technology to be developed would not only depend on the scientific answers to these questions but would also to a large extent be guided by them. Even at the level of building a colony, we need to progress trough a series of experiments on ecological loops if we have any hope of designing human outposts that approach self-sufficiency.

A significant human presence throughout the solar system would not only enhance by orders of magnitude the amount and quality of space science, but also would change drastically the very conception of what may be done in and with space science. Once we are in space permanently the range of possibilities is also altered permanently, not only because humans are around to lend a helping hand, but because they are there under conditions that permit them to move with far greater ease. There are simply far more starting points for space science research, a radically different interplay with a different technology, and a qualitative difference in what may be undertaken. In areas where success turns exploration into routine colonization, the frontiers of science will move further outward, and those that remain may not be so closely connected anymore with the day-to- day activities of the ordinary humans in space. But that turning of the extraordinary into the commonplace will not happen overnight. And when it does, it may simply point to a new horizon of opportunity for science and technology beyond what has just been reached.

The first colonies on the Moon, on Mars, and on the moons of the outer planets would be dedicated mainly to the scientific exploration of those worlds, but also to determining the feasibility of even bigger settlements. As our presence increases so will the opportunities for space science (although I am sure there will be drawbacks on occasion. Once we are up there in force, the panorama of scientific, technological, industrial, and social opportunities may seem vastly different from what we may imagine today.

As those colonies grow, they will transform their extraterrestrial environments. The point may come when we engage in the science, or art, of "terraforming," which at its most grandiose envisions transforming entire planets and giant moons into habitable worlds[6]. If a world does not have enough water, for example, we bring to it one of the thousands of small asteroids from the Kuiper belt composed mainly of water. Crashing the asteroid into that world would also help to increase the density and raise the temperature of the atmosphere. In another world, Venus for instance, we could place a cloud of dust around it to reduce the amount of light it receives from the sun, and then manipulate its atmosphere to reduce its greenhouse effect considerably. We might thus achieve a range of temperatures amenable to life.

Decades, probably centuries, will pass before we understand planet dynamics well enough to attempt to transform any world into a second Earth, a task that should not begin until we have learned the scientific lessons those worlds have to teach us. But eventually, it may open up new niches to our species. In the truly long run, but long before the sun becomes a red giant, the Earth’s “thermostat” is likely to malfunction. James Lovelock, of Gaia fame, and M. Whitfield argued in a 1982 article that life was steadily removing CO₂ from the atmosphere – it actually has been doing so for the last 400 million years, since plants conquered the land – and in about 100 million years the level of CO₂ will go below 150 parts per million (ppm) of air.[7] This level is important because most plants require at least as much atmospheric CO₂ to survive. Newer forms of plants – grass, palm trees – use slightly different mechanisms for photosynthesis and can go well below the 150 ppm. The flora of the future, then, will have a very different view: gone will be the apple orchards and the rose gardens, replaced by new and exotic varieties of plants. Inexorably, unless we intervene, the level of atmospheric CO₂ will go below 10 ppm and photosynthesis will come to an end altogether. More recent studies following on Lovelock and Whitfield’s footsteps have revised their estimate to between 500 million and a billion years.[8]

The loss of plants will be a catastrophe for animals, obviously, but also for marine life, since it depends so much on the run-off of the soil nutrients that result from the presence of plants. Those few animals that can manage to survive will be done in a few million years by the rising temperatures, for eventually geological processes will bring again significant levels of atmospheric CO₂ , which will no longer be kept in check by photosynthetic organisms. Several scenarios have been proposed to explain what will happen after that point. Likely, the expected increasing level of solar energy, coupled with high levels of atmospheric CO₂, will quickly lead to the sort of runaway greenhouse effect that vaporized Venus’ oceans. Thus life will come to an end billions of years before the sun’s transition to a red giant obliterates the atmosphere and the oceans altogether.

In those perilous days the full development of space exploration will come to humankind’s rescue. It could, for example, “terrraform” its own home planet so it will adjust to the new conditions. When that is no longer feasible because the sun’s sphere will expand beyond Venus, we might be able to change the Earth’s orbit. And on failing that, humankind will hang on, on terraformed Mars and Titan, as well perhaps on artificial worlds along the lines of Gerard O’Neill’s space colonies.[9] As humanity expands in search of resources in the solar system, the size and complexity of its space habitats is likely to increase. Eventually our species may move into the Oort Cloud. We will then have followed in space the example of expansion set by our ancestors in our own planet. To accomplish that will require many but plausible advances in propulsion systems, with concomitant increases in the speed of travel. Under those conditions, migration from the Oort Cloud to the stars may well be possible. Humankind will then be able to survive in the truly long run.

Eons before then, a large human presence will make it easier to track, and then to deflect asteroids and comets most in danger of colliding with the Earth, thus saving millions of human lives, and even preventing a repeat of the global catastrophe that wiped out the dinosaurs and most other life 65 million years ago.[10]

It all begins with astronauts.

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[1] Tracy Watson, “NASA Chief: Shuttles were a Mistake,” reprinted from USA Today in Detroit Free Press, September 28, 2005, p. 13A.

[2] See S.G. Brush, "Harold Urey and the Origin of the Moon: The Interaction of Science and the Apollo Program," in the Proceedings of the Twentieth Goddard Memorial Symposium, 1982, published by the American Astronautical Society; and "From Bump to Clump: Theories of the Origin of the Solar System 1900-1960," in P.A. Hanle and V.D. Chamberlain, eds. Space Science Comes of Age: Perspectives in the History of the Space Sciences, Smithsonian Institution Press, 1981, pp.78-100.

[3] The Constellation program, which NASA has proposed for returning to the Moon is a high-tech update of the Apollo program.

[4] http://www.califcity.com/space_ship_1.html

[5] www.nasa.gov/mission_pages/gpb/index.html

[6] See, for example, James E. Oberg, New Earths, Stackpole Books, 1981.

[7] J.E. Lovelock and M. Whitfield. 1982. “Life Span of the Biosphere.” Nature 296, pp. 561-563.

[8] This account is borrowed from Peter D. Ward and Donald Brownlee, The Life and Death of Planet Earth, Times Books, 2002, pp. 101-116.

[9] See Gerard O'Neill's The High Frontier, Anchor Press/Doubleday, 1982 (2nd edition). See also T. Heppenheimer, Colonies in Space, Stackpole Books, 1977.

[10] The probability of such collisions can be found Dana Desoinie’s Cosmic Collisions, a Scientific American Focus Book, Henry Holt & Co., 1996, pp. 100-101. Thermonuclear weapons are the first choice, although O’Neill’s mass drivers might also do the job. He envisioned using such drivers to transport asteroids rich in valuable minerals to a lunar orbit, op.cit.