As if that were not bad enough, we stand to learn very little from the experience. The International Space Station, as it is diplomatically called, will not truly teach us how to live in space; instead, we'll camp out.

It cannot be a closed-cycle biosphere. Its food and water will come up in heavy boosters and be discarded as waste by pushing it back down into the clinging atmosphere. In fact, the whole space station is a hotel perched just above the thin skin of air, so that every year the Russians will have to boost it back into its orbit, or else it will burn up.

Yet with it ride many dreams--apt to be dashed by experience, I fear. Our space station will not bring the fresh perspectives that more than a century of visionaries have glimpsed, as I described last time.

For a time in the 1970s and early 1980s, the popular press and many scientific and technological publications carried articles and pictorial visions of space colonies. Bernal Spheres, O'Neill Cylinders, and hollowed-out asteroids showed us parklike and urban environments floating in space, offering secular heavens to the masses of the dying Earth.

If it came to a choice between a finite planet, zero population growth, restrictive social regimentation, and rationing of ever dwindling natural resources on the one hand, versus the openness of free space on the other. . . . well, space settlement seemed about to take on the classic proportions of an idea whose time had come.

There would be problems, but at least they would not be our current problems.

Many thinkers argued that here was an economic high ground worthy of culture and technology, that when taken would lead to a permanent, mature civilization. Space settlements were that high ground, the visionaries insisted; but we would have to build them before we could be certain of success, which in human affairs was never guaranteed.

But to wait for the right time might mean waiting forever, risking a decline from which humanity might never recover. History has a consistent record of the good happpening alongside the bad; to hesitate might be disastrous, hurling us into the irreversible decline of Arnold Toynbee's two dozen failed civilizations, with no new ground upon which to begin again. Such was the argument against the "prioritizers."

Asimov wrote to the skeptics:

"I have received a number of letters concerning my article 'Colonizing the Heavens.'

Some call it fiction. (Real nonsense, I suppose, like reaching the Moon.)

Some say I am trying to subvert the doctrine of Zero Population Growth. (As though it weren't possible to try to colonize space and stop the population growth, too. They are not mutually exclusive.)

Some say it is too expensive. (Not if the world stops supporting military machines.)

Some say that nobody wants an engineered environment. (Nobody? How many people are living in caves these days?)

Some say that nobody would ever want to cross space in three days to live in a space colony. (This from people whose ancestors two or three generations back probably crossed the Atlantic in steerage, or crossed the western desert in covered wagons.)

Some say that Third World people would never go. (Sure. Only aristocrats fled to the New World. All the tired, the poor, the huddled masses yearning to breathe free never came, did they?)

Some say let's solve our problems on Earth before we try to colonize space. (Someone said that to the Pilgrims. Come on, they said, let's solve our problems right here in Europe.)"

Space was to be a ground for change, not just suburbs in vacuum. The advocates for skylife did not just want to build castles in the airless, but on the firmest of economic foundations--the great wealth of our sunspace.

We are living through a time when grand experiments seem daunting. Yet space stations promise something different--social spaces where new ideas can bloom.

From the beginning, space colonies were advanced not only with the assertion that they were possible, but also out of a concern for the future welfare and survival of humanity. Tsiolkovsky wrote in 1912:

"To step out onto the soil of asteroids, to lift with your hand a stone on the Moon, to set up moving stations in ethereal space, and establish living rings around the Earth, the Moon, the Sun, to observe Mars from a distance of several tens of versts, to land on its satellites and even on the surface of Mars--what could be more extravagant! However, it is only with the advent of reactive vehicles that a new and great era in astronomy will begin, the epoch of a careful study of the sky . . . The prime motive of my life is to do something useful for people . . . That is why I have interested myself in things that did not give me bread or strength. But I hope that my studies will if not soon but perhaps in the distant future, yield society mountains of grain and limitless power."

Physics has its place in space settlements, but the crucial sciences supporting a civilization in space are biological and social sciences. The greatest return will come not in purely technological advances but in the psychosocial benefits of a revitalized humanity. Gerard O'Neill wrote in 1976:

" . . . I believe that our children will judge the most important benefits of space colonization to have been not physical or economic, but the opening of new human options, the possibility of a new degree of freedom, not only for the human body, but much more important, for the human spirit and sense of aspiration."

One of the charges leveled against both scientists and science fiction writers is that their visions of possible futures have been consistently too conservative. "Skylife" beckons to many because it has such vast physical potential.

Picture thousands of space settlements, ranging in size from a few kilomters to a hundred kilometers or more in diameter, orbiting the Sun, catching our star's energy in an urban shell of space habitats. The societies are pluralistic, constantly diverging in design and philosophies. New ones are being born as population increases. Some even leave the solar system to explore other sunspaces.

Now jump even further ahead: pace settlements, spomes, or macrolife (whatever they may be called) are the dominant urban civilization in various sectors of our galaxy. Planets are considered the galaxy's countryside. Some habitats are mobile; others stay at home and surround various stars in what has been called a Dyson Sphere (after the physicist Freeman Dyson), which can be designed as a porous shell of small worlds---not a literal solid sphere, which would collapse at its poles, even if spun to offset gravity. If one were to build only the equatorial belt, then we have Larry Niven's Ringworld.

Asteroid-sized worldlets need not be cramped spaces and metal corridors--or small, compared even to planets. As Isaac Asimov described in his 1956 story, "Strikebreaker":

"We are not a small world, Dr. Lamorak; you judge us by two-dimensional standards. The surface area of Elsevere is only three quarters that of the State of New York, but that's irrelevant. Remember, we can occupy, if we wish, the entire interior of Elsevere. A sphere of 50 miles radius has a volume of well over half a million cubic miles. If all of Elsevere were occupied by levels 50 feet apart, the total surface area within the planetoid would be 56,000,000 square miles, and that is equal to the total land area of Earth. And none of these square miles, Doctor, would be unproductive."

Surface area depends on the square of a given distance, while volume depends on the cube. This simple fact means that honeycombing an asteroid provides immense livable room.

If the chunk of rock has a typical size R, then one can riddle it with levels for habitation, each separated by, say, a typical distance H. Simple geometry says that the living area of such an enormous apartment house would be of order R³/H. People need head room of about two meters, and a bit extra for structural support and piping in air and fluids. Probably this sets the net spacing of living levels at a number like H=4 meters.

We can then ask how big an asteroid need be to give us living room equal to the entire area of the Earth, even including the oceans. That is, we set our R3/H equal to the surface area of the Earth, 4(pi) Re², for a radius Re 6,300 kilometers. Plugging these numbers in and solving, one finds R is about a hundred kilometers. This is remarkable, for there are many asteroids of such size; the largest, Ceres, is 380 kilometers in radius.

A Dyson Sphere or Ringworld would have the surface area of millions of Earths, by spreading the surface over a giant sphere or ring.

The idea of all humanity living inside a rock only about two hundred kilometers in diameter sounds wildly improbable . . . at first. But the scaling emerges because of the cubic increase of volume with size. Our hidden assumption, of course, is that unlike on the Earth's surface, one could settle people inside and still supply the needed air and light. Sunlight drives our earthly environment's engines; an asteroid colony would need some power supply. At most, the power needed would be comparable to that received by the Earth as sunlight---about 10¹⁷ watts, an enormous figure compared with the 10¹³ Watts the asteroid would receive in sunlight at the same distance from the Sun.

But of course the colony would not need all that energy, nor would it be able to shed the waste heat generated from it after use. On Earth a person in an advanced nation uses several kilowatts steadily, so five billion people would require perhaps 10¹³ Watts, just about the incoming sunlight. These numbers are crude guesses, but they give some idea of the scales involved.

Most habitat stories feature an obligatory walk-around-the-artifact scene. A common game played down through the decades was the my-artifact's-bigger-than- your-artifact competition. Sheer scale is an easy way to evoke awe. But space habitats can use cold engineering triumphs to evoke dainty beauty. While space is vast, those living in it may inhabit if not cramped, then firmly bounded preserves. What would such limits do to the shadowy depths of our psyches?

Nobody knows. Asimov had agoraphobia, a fear primarily of heights, and a dislike of open spaces. His Trantor feels like living in a series of New York apartments, so it is not surprising that he thought in terms of packing people into a volume. Could people truly live that way? Most city denizens seldom note the sky, but long term disorders may emerge from prolonged groundhog living; we do not know, because few choose to live that way on Earth.

Using the volumes of all the known asteroids would yield a new equivalent land area of about 3000 times Earth's total surface. This suggests that material limits are not primary in determining the possibilities open to humanity; social goals set our ends.

A sprawling, sunspace civilization would not be resource-limited, unlike human societies throughout history. It could live for influence and curiosity, for the power to educate and persuade. Knowing and creating would become more important than economics and personal power. Style and novelty would rule within a stable economic container that would support an endlessly developing string of cultures.

Karl Marx and Adam Smith would both be subsumed, because economics become truly basic--and irrelevant. Thomas Malthus would be circumvented, because there is a Peter with practically infinite pockets who can be robbed to pay Paul.

In this seemingly utopian vision, one nevertheless entirely achievable by all that we know of physical reality, poverty is possible only on emerging regions-- -which must go through their own rites of passage, their own quantum jumps into self-sufficiency---and no one can help them without doing irreparable psychosocial damage. Our human history may very well be at such a critical juncture now, with only our reason and creative imagination to draw us out of the cradle that might become a tomb, if we delay.

Perhaps this description holds the answer to Fermi's Paradox, which asks: If the universe is full of intelligent life, then where are they? One answer may be that most cannot visit us because they are held back by the forbidding economics of interstellar travel; and that those that can will not.

Another answer contends that the rise of reason leads to catastrophic modifications of the environment, both external and bodily, and the species perishes. Those that reach a subtle stage of rational development without destroying themselves, or are not destroyed by natural disasters, have no interest in contacting lesser species. The advanced ones converse only with those of their level of achievement, if at all, since such dialog may pose dangers.

A bleak view. Or perhaps nearly all intelligent cultures in our galaxy are still provincials in space and time, in their sense of history and grasp of technical possibilities. The answers to Fermi's Paradox are likely to be many, but they seem different in light of sunspace's potential.

Our dilemma is clearly posed by human history: intelligence is at first an innovation, then flares into conflict with its environment, then threatens its environment and itself.

If it fails to get past this crisis of "first technologies" and does not grow into a more benign relation with its environment, human intelligence will destroy itself---if not through warfare then through some complex mistake. Skylife may be part of a more productive and satisfying environment for human intelligence---a new adaptation, if we can seize it. But humanity is psychologically frail; failure is the basic theme of our literature and politics, which often regard rationality and creative visions with derision and skepticism.

So does skylife imply unending utopia?

"People who live on planets think small," Larry Niven has written, and we must remind ourselves what small means. An average household today commands more horsepower than kings once did. To classify possible civilizations by energy use, as the Russian astrophysicist Kadarshev has proposed, yields a striking perspective: Type I civilizations use the available energy of their whole planet. Type II use the output of their whole sun. Type III harness the power of a galaxy.

We are not even Type I. The possibilities for growth are endless, since the space settlement is a container waiting for a variety of social forms, an economic base for ongoing creativity supported by a high-energy, open-ended industrialism that escapes the restrictions faced by planetary cultures. The mobile space habitat cannot easily die. It is the true fulfillment of the aims of space travel, the ultimate consolidation of gains made by exploiting the space around the Sun. The view from even our cramped, fledgling spaceships has led us to see the planet as an ecological ship circling our sun, and to imagine building worlds from scratch. We have been doing so since civilizations began, in the form of towns and cities, but we have not had enough energy and resources to make our surface habitats work as well as they might.

The idea of space settlements has been decried as technocratic hubris. But nay- saying in the face of solidly based economic and technical challenges leads to social and economic impotence. Like the opening of the Americas, space demands long-term thinking.

Reflect that a century passed between Columbus and the first true colony in the New World. Here in the opening decades of a similar epoch, we cannot see any intrinsic limits to sunspace's potential, except possibly psychological ones. It may be that an energy-rich Type I or II culture would face extraordinary problems in the use of its powers, but not in having them. One of the problems might lie in a dangerous scarcity of rebels and critics, because everyone will be so comfortable. (Indeed, does this describe present-day Europe?)

There will certainly be new problems from causes we cannot foresee. Yet we can grasp that the future perfection of our world's problematic industrialism is possible only through an expansion of our horizons, not by shrinking from them. The objections of those who fear that the future may differ from the near past stem from the realization that today's network of familial and corporate power structures may come to an end.

Human problems may crumble before human ingenuity, which is always at first a small thing of thoughts and words, dreams and mistakes. Even honestly motivated critics serve only those who fear the loss of their power and influence in economic and political arenas; they put on the brakes by asking for guaranteed cost projections, for assurances that there will be no mistakes (which means there will be nothing to learn from, no feedback).

Objections that ask for this kind of warranty make a well-known logical error known as "the counsel of perfection," which does not recognize degrees of success and therefore seeks to ban any consideration or test of an idea. No demand could place a deadlier obstacle before human creativity.

What can we learn from the social sciences about this?

In Cannibals and Kings: The Origins of Culture (1977), anthropologist Marvin Harris described how technical efficiency depletes resources, precipitating either a sudden decline in a culture or a new level of innovation, which then repeats the same process; but he is ambivalent about the overall pattern of entrapment and futility suggested by his model. Certainly he saw little point in living outside the atmosphere, even if that opened resources.

Historian of science Bernard Cohen answered him in this way:

"Harris assumes that there have been centuries of post-feudal mechanization and scientific engineering. He doesn't recognize that large-scale innovations in engineering and technology based on advances in fundamental science are a recent phenomenon, barely a century old. It is thus an open question whether future societies may not exhibit a really different growth pattern (even with respect to ecological and reproductive pressures) from that of all previous societies since science has revolutionized the mode of making technological innovations. In any event, as Harris observes . . . evolutionary theory may make us aware of the 'determined nature of the past,' but it does not provide the basis for the determination of the future. Admitting that the 'intensification of the industrial mode of production undoubtedly portends an evolution of new cultural forms,' Harris concludes that he does not 'know for certain what these will be, nor does anyone else.'"

The exchange between Harris and Cohen is typical of many such debates and suggests a real failure of humanistic culture. Consider that Harris and others who continue to speak do so at a time when the models for creative alternatives- --space habitats being only one example---are proliferating in a staggering explosion of human creativity; and this explosion of speculation really began only in the 1970s. Some of these ideas, as Carl Sagan suggested, may become productive social paths.

Many have argued that the word utopian should be used not in the pejorative sense but in the dynamic sense, as H. G. Wells redefined the word to remove its association with the fear of a static, totalitarian perfection. Wells was foremost a critic of progress who hoped and then, after trying to do something about it by educating the world, gave up hope. He is a sobering reminder of what happened to the widespread optimism pervading the Europeans at the turn of the last century.

Isaac Asimov, Carl Sagan, and Jacob Bronowski played this same role of educator in more recent times, struggling with the grim spectacle of human failure and incompetence. Wells felt that it was the fate of all so-called utopian visions to be more or less misread--and he urged not static perfection but dynamic, critical methods that would thrive on change and nurture its creative directions. In A Modern Utopia (1905) he wrote that "the state is for individuals, the law is for freedoms, the world is for experiment, experience, and change: these are the fundamentals upon which a modern Utopia must go." It is no wonder that the totalitarian Lenin "felt sorry" for Wells during their meeting, since Lenin's view of human nature, and Stalin's after him, was that of a mad dog wearing a muzzle.

There are deeper constraints at work, say the critics of a more imaginative, risk-taking creative reason. The case for optimism is based on the fact that nature is vast and infinitely rich; and once we widen our field of economic operations off the Earth, there will be no limits to growth or the use of energy. The case for pessimism accepts the vision as possible, but states, sometimes very convincingly, that human beings may not be able to make use of the possibilities that wait. Because of our flawed nature, we will cower in our little corner of the universe and be unable to control ourselves sufficiently to reach for the riches around us. Cruel inner realities will stand against our desire for change. Some read this in the currently raging battles over sociobiology: we are chimps and had better get used to that revelation.

What will actually happen? Much depends on how it actually feels to live in space. Will adapting to zero-g prove possible? Will we find it useful to convert our legs into extra arms, as Lois Bujold envisioned?

The debate will never end between those who see only problems and those who see the heights--until some specific examples are explored in fiction or, better, in experience.

On one side we have the writer Norman Spinrad's acid comment, "Living in a space colony would be like being at a science fiction convention held aboard a nuclear submarine . . . forever!" He was talking about the kind of scaled-down spacehabitats that might be built after the politicians were through cost- cutting.

On the other side we have simple, eloquent gestures. In 1997 a thimblefull of Gerard O'Neill's ashes was lofted into orbit in the first commercial "burial," though in their low trajectory they will reenter the atmosphere within a few years (a fiery Viking funeral after all?). His ashes flew with those of Timothy Leary, another dreamer.

America was the first truly sophisticated, self-aware, fresh beginning in humankind's brief recorded history. Why do we not have space exploration and expansion at the level of past imaginings? Are recent human generations simply too tired and unequal to the task? Perhaps. But most of the answer comes down to money and fear.

NASA has not yet done an experiment trying centrifugal gravity---a staple idea of skylife. The International Space Station will try very few innovations. Until a livelier spirit animates the official space program, the tough jobs of getting into orbit cheaply, and living there self-sufficiently, will probably have to be done by private interests who can angle a profit from it.

In the meantime, we can imagine. "Science is my territory," writes Freeman Dyson, "but science fiction is the landscape of my dreams." The loop of science fiction, speculative foresight, and the sciences is the way we dig out what is implied by nature and by our human natures. Our creativities attempt both to invent, predict, and prevent what may happen, while time unfolds and hurls us forward, and we strive to swim as a species, rather than be pulled along by the current.