From extropians-request@gnu.ai.mit.edu Fri Jul 23 06:08:20 1993 Received: from ude.tim.ia.ung.gnu.ai.mit.edu by mail.nada.kth.se (5.61-bind 1.4+ida/nada-mx-1.0) id AA28187; Fri, 23 Jul 93 06:08:06 +0200 Received: by ude.tim.ia.ung.gnu.ai.mit.edu id AA27375; Thu, 22 Jul 93 21:41:12 EDT Received: from panix.com by ude.tim.ia.ung.gnu.ai.mit.edu via TCP with SMTP id AA27370; Thu, 22 Jul 93 21:40:50 EDT Received: by panix.com id AA18729 (5.65c/IDA-1.4.4 for exi-remail@ung.gnu.ai.mit.edu); Thu, 22 Jul 1993 21:18:20 -0400 To: Exi@panix.com From: Hans Moravec Date: Thu, 22 Jul 93 21:17:36 EDT Message-Id: <9307230117.AA00573@turing.think.com> X-Original-To: Exi@panix.com Subject: Robot Slaves X-Extropian-Date: Remailed on July 23, 373 P.N.O. [01:18:11 UTC] X-Message-Number: #93-7-880 Reply-To: extropians@gnu.ai.mit.edu Errors-To: Extropians-Request@gnu.ai.mit.edu Status: RO The Age of Mind: Transcending the Human Condition through Robots Hans Moravec Bantam Books, probably early 1994 Chapter 4: The Age of Robots A thousand centuries ago the world was fully automated: our ancestors were well adapted to live off the maintenance-free, self-operating machinery called Nature. But, in a Faustian (or Adamic) bargain, they meddled with the mechanism, increasing its output, but trapping themselves in a routine of heavy, unpleasant labor. Anthropologists were surprised by ergonomic analyses showing that citizens of advanced societies worked far longer and harder for their living than primitive hunter- gatherers, but millennia ago many American Indian tribes were aware of the disparity, and consciously chose to be sparse nomadic hunters rather than sweating farmers. Meanwhile, the agricultural civilizations burnt their bridges through population growth, and by devising and becoming addicted to an ever-expanding array of ever-more-elaborate social and physical inventions. Prominent among the innovations were means for avoiding civilization's unnatural work: draft animals, slaves and labor-saving machinery. For most of our history, these developments, while increasing society's overall vigor and control of nature, merely shifted the workload from one back to another, or to different activities. Only in the last century or two has labor-saving machinery begun to overtake labor- creating expansions of social responsibility, and so begun to diminish the total amount of work required of civilized humans. Despite brief setbacks, the trend is accelerating, and we seem to be controlling more and more of what affects us, with less and less work. Of course, there are several catches. In all recorded history until this century, almost every civilized person was a farmer, consumed in raising food, and in spare moments, manufacturing clothing and shelter. Institutions like slavery, feudalism and capitalism allowed a small minority to live off the work of others, giving some the means to explore new possibilities, including alternative ways of doing hard work--a slow process that eventually produced the industrial revolution. In this century, industrialization-- biological, chemical and organizational innovations, but mainly giant machines that do the work of hundreds of humans, but are controlled by only one--has finally ended most agricultural labor: in the United States a few percent of the population produces surplus food for all. Displaced agricultural workers moved into manufacturing jobs, where, besides filling many new needs, they made the farming machines. But, just a few decades later, more advanced machines do most of the manufacturing. Displaced factory workers have moved into office and service jobs, where, besides filling many new needs, they help devise and direct the manufacturing machines. But while that displacement still reverberates, machines are assuming the engineering, management and customer relations jobs of the service industry. The road of productive human employment may not lead much further. It is sometimes said that mass manufacturing ended the role of the craftsman, who was replaced by heavy machines stamping out identical parts. In fact, the craftsmanship moved into the engineering department, where products are first designed, the means to manufacture them devised. Engineering is a thought, labor and creativity-intensive endeavor. In the late 1980s it began to be massively automated. Like tractors and combines for farmers, computer design workstations are tremendous labor savers for engineers. With a good program, a designer can simply indicate an internal change in a complex device, and almost immediately see its effect on the other parts of the design. In the 1970s such an exploration, conducted on drafting boards, might have consumed several junior engineers for weeks. The overall effects on productivity and employment may never be precisely measured, but individual businesses as diverse as plastic injection mold designers and architectural firms have reported tenfold throughput increases with no change in employment after replacing manual methods with inexpensive computer design and accounting systems. New generations of integrated circuits and of computers, though a hundred times as complex as those of a decade ago, now appear nine months after conception rather than in three years. An all this comes from the first generation of widely available computer engineering aids. More powerful computers and software are now being devised to do more of the designer's job, automatically sorting through design alternatives, for instance, looking for configurations that best meet cost and performance specifications, or simulating circuitry, software and three dimensional structures to evaluate products before they are built. Linked directly to manufacturing machines in the factory, the design systems of the near future will allow a handful of engineers to produce a cornucopia of excellent products, much as a few farmers riding the air-conditioned cabs of powerful combines can harvest enough wheat to feed a city. Meanwhile, in the office, layers of management and clerical help are evaporating. From their earliest days, computers displaced workers in number-intensive jobs like accounting, but word-oriented office tasks remained untouched until recently. In the 1970s the Stanford Artificial Intelligence Laboratory, with over fifty faculty, staff and students, prided itself in needing only one secretary. Using the lab's time-shared computer (it seemed big at the time, but a 1990 personal computer is more powerful), everyone was expected to produce documents using editing and publishing software (the term "word- processing" had not yet appeared), to issue reminders and memos via computer mail, and to do accounting and scheduling with specially written programs. The lab also had among the first engineering drawing programs, and was so stocked with excellent programmers that new capabilities appeared almost daily. Today, every competitive office is similarly automated, and edging towards as low a ratio of support staff. New generations of software, doing the data-gathering and decision-making functions of whole departments, will cut even more deeply. Once there may have been story tellers, dancers and singers in almost every village, recounting the epics that were a tribe's long-term memory. A radical new technology--writing-- assumed many of their functions, reduced performers to mere entertainers, and allowed one storytelling to reach thousands across space and time. Printing, the phonograph, motion pictures, radio and television, by increasing the amplification factor to millions, made entertainment a fantastically competitive business with only a few providers. Computer technologies are eroding what jobs remain: in the 1980s some composers produced polished orchestrations of their work without musicians, using computerized music synthesizers. The visual media are headed in the same direction: in the 1990s many television commercials, apparently of real objects, are actually ultra-lifelike computer cartoons. In future, the technology will allow similarly realistic portrayals of humans and animals, displacing actors. Computers most easily supplanted those who deal in numbers and other paperwork. They are only now beginning to nudge out workers in more essentially physical fields, handling commodities and interacting with customers, and decision makers who employ their perceptual-motor-social grasp of the world in the more abstract mode called human judgment. Telephone companies long ago replaced most of their operators with automatic switches, but soon even voiced queries will be handled by speech-recognizing computers. In the 1980s machines began to sort most mail for the US Post Office, but obscured or handwritten addresses were shunted to humans: soon trainable text-reading machines will be good, fast and cheap enough take over--in time to compete with purely electronic forms of mail transmission. In the same decade expert systems, made of decision rules painstakingly entered by hand, began to advise many businesses--configuring computers, prospecting for oil, authorizing credit-card purchases, even making medical diagnoses and suggesting treatment. In the 1990s they are being replaced by more effective second-generation systems with trainable components like neural nets. As noted in previous chapters, robots cannot yet handle material objects with human flexibility, and are useful only in highly structured environments like factories--in the broader world, intricate manual work is still in hands of flesh. Mechanization and automation have concentrated human work, as devices like earth-movers, combines, television stations, automatic milling machines or office computers permit a few skilled operators to replace a greater number of humbler laborers. The machines work prodigiously, but require human direction and assistance. Some see this as the natural, desirable, and inevitable relation between humans and machines-- implicitly drawing a line between human and machine skills. But the boundary is not static. Machines cannot yet match human motor control, judgment or emotional empathy, but they are advancing rapidly on all fronts, and the amount of human involvement essential in productive work is steadily shrinking. A telephone, a cash register or a simple milling machine requires a skilled operator for each transaction, but an answering machine, a bank teller machine and a computer- integrated factory may run autonomously for days. Rising productivity--an imperative of company survival as long as customers choose better goods at lower prices--implies that output per worker increases, and the amount of labor decreases. This century's labor movement spread productivity's wealth by giving most workers higher pay for shorter hours. World War II temporarily halted the trend, by absorbing laborers and production in conflict, then reconstruction. But, by the late 1950s, economic conferences and publications began to worry about excess leisure time. In the US, aggressively nurtured consumerism and a fabulously expensive Cold War managed to absorb surplus productivity. In some parts of Europe, on the other hand, the work week shrank to 35 hours and vacations grew to two months. Advancing automation in general, and widespread robots in particular, will soon dwarf prior reductions in the need for work. In the short run this threatens major unemployment and other economic dislocations. In the medium run, it is a wonderful opportunity to recapture the comfortable pace of a tribal village, while retaining benefits of technological evolution. In the long run, it marks the end of the dominance of biological humans, and the beginning of the age of robots. The Short Run (early 2000s) As the industrial revolution gathered steam two centuries ago, it destroyed cottage industries and concentrated wealth in he hands of factory owners--the capitalists. Millions of displaced home workers competed for too few jobs tending the new machines. It took difficult political readjustments to equalize the benefits of cheaper, more plentiful goods, but gradually laborers' hours were halved, creating need for more workers, and so bidding up salaries. Though it increases communal wealth, each increment in automation threatens a similar unpleasant transient, as it displaces one group of workers with fewer doing different tasks. If the new required skills are common, mass competition for the few jobs drives down salaries. If the skills are rare, scarcity encourages high pay and long hours. Either way, some work excessively while others are jobless--and it takes slow changes in the social contract and in education to level the load. Though work hours will decline, they cannot be the final answer to rising productivity. In the next century inexpensive but capable robots will displace human labor so broadly that the average workday would have to plummet to practically zero to keep everyone usefully employed. Already, much labor services more questionable needs--gargantuan government bureaucracies, cosmetic medicine, mass entertainment, and speculative writing, to give a few examples. In time almost all humans may work to amuse other humans, while robots run competitive primary industries, like food production and manufacturing. There is a problem with this picture. The "service economy" functions today because many humans willing to buy services work in the primary industries, and so return money to the service providers, who in turn use it to buy life's essentials. As the pool of humans in the primary industries evaporates, the return channel chokes off--efficient, no-nonsense robots will not engage in frivolous consumption. Money will accumulate in the industries, enriching any people still remaining there, and become scarce among the service providers. Prices for primary products will plummet, reflecting both the reduced costs of production, and the reduced means of the consumers. In the ridiculous extreme, no money would flow back, and the robots would fill warehouses with essential goods which the human consumers could not buy. The scenario above is incomplete. Not all individuals involved in productive enterprises actually work there. Stockholders, having once contributed capital to a thriving enterprise, may collect dividends indefinitely. Workers can be replaced by something more efficient, but in the present legal system, owners remain unless they sell out. Even with total automation, human business proprietors will continue to profit, and so be able to patronize the service providers. An analogous situation existed in classical and feudal times, where an impoverished, overworked majority of slaves or serfs played the role of robots, and land ownership played the role of capital. In between the serfs and the lords, a working population struggled to make a living from secondary sources, often by performing services for the privileged. The most prestigious and prosperous commoners sold high quality products and services directly to the gentry (as in the proud line still seen in Britain, By Appointment to Her Majesty). A larger number lived less well by trading with other townspeople. It is unlikely that a future majority of service-providing "commoners" with more free time, communications and democracy than today, would tolerate being lorded over by a minority of non-working hereditary capitalists: they would vote to change the system. The trend in the social democracies has been to equalize income by raising the standards of the poorest as high as the economy can bear--in the age of robots, that minimum will be very high. In the early 1980s James Albus, head of the automation division of the then National Bureau of Standards, suggested that the negative effects of total automation could be avoided by giving all citizens stock in trusts that owned automated industries, making everyone a capitalist. Those who chose to squander their birthright could work for others, but most would simply live off their stock income. Even today, the public indirectly owns a majority of the capital in the country, through compounding private pension funds. In the United States, universal coverage could be achieved through the social security system. Social security was originally presented as a pension fund that accumulated wages for retirement, but in practice it transfers income from workers to retirees. The system will probably be subsidized from general taxes in coming decades, when too few workers are available to support the post World War II "baby boom." Incremental expansion of such a subsidy would let money from robot industries, collected as corporate taxes, be returned to the general population as pension payments. By gradually lowering the retirement age towards birth, most of the population would eventually be supported. The money could be distributed under other names, but calling it a pension is meaningful symbolism: we are describing the long, comfortable retirement of the entire original-model human race. The Medium Run (around 2050) What happens to people when work becomes passe? Existing retirement communities are probably too sleepy to be a good model--most of the individuals there have completed their life's work, and are of declining vigor and health. Better examples may be the richest Arabian petro-kingdoms, where oil-bought foreign labor plays the role of total automation. In a tradition of tribal sharing shaped by a sparsely-furnished nomadic past, Kuwait, Saudi Arabia and the United Arab Emirates have managed to spread the new wealth broadly among the citizenry in a single generation. Free health care and education, and undemanding government jobs, or outright welfare, secure life's needs, and life expectancies and literacy rates are among the world's highest. Comfort and security mute the stresses of civilization, including the tension between circumscribed Islamic values and the liberties of a wealthy world culture. The societies produce both world-class achievers and criminals, but on average show less driven urgency than many industrialized nations: most of their citizens seem happy to simply live their lives, and stability is endangered only by neighboring countries, where impoverished majorities are less content with the status quo. In numerous smaller examples, wealthy families often produce generations of content, even smug, heirs (as well as exceptions to titillate the tabloids). Contrary to fears of some enmeshed in civilization's work ethic, our tribal past prepared us well for lives as idle rich. In a good climate and location the hunter-gatherer's lot can be pleasant indeed: an afternoon's outing picking berries or catching fish--what we civilized types would recognize as a recreational weekend--provides life's needs for several days. The rest of the time can be spent with children, socializing or simply resting: this is the life Davi Kopenawa, the Yanomami spokesman presented in the first chapter, was begging to protect from civilization's mania. Of course, our ancestors had also to survive hard times, and evolution bequeathed us the capacity for desperate measures, including hard work. Civilization turned that extremity into everyday normality, and now stress is the leading cause of disease, and probably triggers some of the ugliest aspects of tribalism. In primates, overpopulation is a common reason for group distress, as nature-provided food and shelter falls short. To survive, a strong tribe may chase away or exterminate a weaker neighbor, or drive out or otherwise eliminate some of its own members: maybe those who smell, look, sound or act differently. Sometimes stressed individuals become accident or disease prone, and die spontaneously, improving the prospects for their relatives--similar considerations could regulate the prevalence of non-reproductive behaviors like homosexuality. City life, absurdly crowded and stressful by tribal-village standards, may inappropriately activate unconscious overpopulation reflexes--the self-destructive emotional vehemence of ethnic strife hardly reflects rational self-interest. It will harder to stir up battle fervor against minorities from the luxurious lassitude of a robot-supported life. Ultra-conservative Switzerland may be a hint of things to come. Government and commercial institutions perfected through centuries of peace (interrupted only briefly by Napoleon) have given Switzerland unmatched prosperity, stability and security. Most Swiss citizens work, but they do so comfortably, with generous government welfare--and Italian immigrant labor--having lessened the desperation that forces workers elsewhere into unpleasant jobs. Comfortable prosperity has allowed multi- ethnic, multi-religious, multi-language Switzerland, made of 23 fiercely independent Cantons each with its own traditions and history, to peacefully endure the most severe internal differences of opinion, for instance the political fury between German and French factions during the first World War. The average Swiss citizen may resist most major changes (why ruin a good thing?), but Switzerland produces world-class contributors in all fields--if a bit less flamboyance than average. While it gives everyone the opportunity to excel, it lacks the social trauma that drives some other countries. Few Swiss would prefer it otherwise. Many trends in industrialized countries presage a future of humans supported by a rich robot economy, as our ancestors were supplied by their ecology (call it paradise with plumbing). Technology and global competition are gradually depopulating businesses. Even absent universal robots, increasingly flexible automation is displacing labor in food production and manufacture, while communicating computers are replacing clerks, secretaries, and managers in offices. Jobs that still require human labor are moving to the homes of computer-equipped "tele- commuters" (like this author) who report reduced stress and improved family life. In a ripple effect, smaller work staffs imply less catering, janitorial and maintenance support. In future, as smarter computers, able to handle policy making, public relations, law, engineering and research replace the last telecommuters, and as capable robots displace technicians, janitors, vehicle drivers and construction crews, it will only be common sense for a population to vote itself income from taxes on labor-free but superbly productive industries. Less developed countries might rapidly catch up by offering the same industries location and raw materials at lower tax cost--a trained population will no longer be a requirement. Western democracies may come to resemble lazier Switzerlands, but with large differences. Big cities will lose their economic advantages, and may begin to evaporate, as individuals, linked to the world by high fidelity communications and served by personal robots, scatter to areas offering more elbow room. Large countries may similarly become less important, as taxes on local industries, and local robot labor, become adequate to supply all human needs. The civilized world may again return to a comfortable tribalism, after a five millennium detour into organized civilization. Countries with traditional tribal structures may simply stay that way, building on their ancestral customs, leapfrogging urbanization altogether, while developed countries foster tribes with customs and beliefs that exceed even today's notion of bizarre. Tribalism will express itself in entirely novel ways. Over the last two decades, inter linked computer networks have hosted small communities whose members happen to be distributed around the world. In 1993 the informal "Usenet" had about ten million subscribers, carrying on about three thousand specialized discussions on every conceivable topic, some with fifty page- long messages every day. Regular contributors to a particular "newsgroup" soon begin to recognize one another, and develop characteristic interactions, likes and dislikes. They form factions that praise, recruit, condemn and ostracize. When a newsgroup grows too large and noisy, specialized subgroups are formed, reducing the original group's population. In future, the world networks will have much greater capacity, and new abilities, such as language translation. "Tribes of common interest" will share more than written text, perhaps exchanging voice and video, or manifesting themselves in full sensory 3D, in synthesized virtual realities: tribal lands that exist in the minds of computers, in greater number, variety and accessibility than possible in the physical world. That is a topic for the next chapter. While computer simulations create entirely new worlds, robots will transform physical life. Today, manufactured items are difficult to make, and thus relatively rare and expensive, and we expend great effort in acquiring and defending them--our homes are fortified warehouses of our possessions. Stockpiling will be less appropriate amidst robotic abundance: why hoard fruit in an orchard? Conventional manufacturing methods-- molding, casting, milling, assembly--can be robotically orchestrated to make new items fairly quickly. Even better, robotic accuracy and patience can build up solid objects by precisely "painting" various materials, layer upon cross- sectional layer. Such new approaches, refined to molecular resolution (done now modestly in scanning tunneling microscopes) will produce arbitrary solid objects from computer descriptions. Humans may be able to live in uncluttered spaces--in ecological preserves, if they choose--yet have any needed item, perhaps even food or housing, made on the spot, or delivered from small local caches--then disassembled back into into raw materials after use. The most visible technological products remaining may be robots themselves, in various sizes and shapes, and these may lurk unobtrusively until called upon. Robots that live among humans, providing goods and services, will themselves be consumer products, styled, outfitted and programmed to please the customers. They will be manufactured by very different robots that extract energy and raw materials and perform major engineering, exploration and research projects. Molded by the constraints of the physical world rather than by human whim, these worker machines are likely to become ever more varied in size, shape and function, forming an entire ecology of artificial life that will eventually surpass the existing biosphere in diversity. The first fully automated companies, evolved from existing firms, will be in familiar industrial settings near population centers. As human labor becomes superfluous, economics will dictate cheaper sites, perhaps locations that humans find unpleasant because they are too hot, too cold, too dry, too poisonous, too far underground or too remote. Robot companies will be shaped by future editions of existing laws, by taxes, and by consumer demand. Existing laws give incorporated entities some of the rights of a person, most importantly the right to own property and make contracts. They do not grant the right to life--corporations may legally be killed by competition or through legal or financial actions. Corporations are bound by laws similar to those that regulate humans, and can be punished through fines, operating restrictions or dissolution--even without humans to fine, imprison or execute. Corporations stay alive by building and maintaining physical assets that generate income to pay their expenses. In the mid 21st century, the biggest expense will be taxation, and income will come mostly from choosy human customers. Tax laws will be shaped by human voters: there is no precedent or motivation for extending suffrage to robots, and the vote will be one of the very few advantages humans retain. Some debate is inevitable, but there should be few qualms about keeping even very superior thinking machines in disenfranchised bondage. It takes force, indoctrination and constant vigilance to counter inherited needs and motivations and enslave a human, but a robot can be constructed to enjoy the role. Natural evolution itself has provided examples, in worker castes of social insects, and self-sacrificing mothers of all species. The primary job of voters in the next century will be protecting their retirement benefits, that is ensuring that robot industries continue to support them. The robots will present a moving target, but the instruments of control will also grow in power. Not only will companies that get out of line be liable for punishment--if necessary, by force purchased from other companies--but they can be controlled a-priori by intrusions directly into their software. Corporate intelligences may be governed by structures like those controlling fourth-generation robots in the last chapter. Immensely powerful reasoning and simulation modules will plan complex actions, but the desirability of possible outcomes will be defined by much simpler positive and negative conditioning modules (or by sets of axioms in super-rational systems), whose composition shapes the character of the entire entity. Humans can buy enormous safety by mandating an elaborate analog of Isaac Asimov's three "Laws of Robotics" in this corporate character--perhaps the entire body of corporate law, with human rights and anti-trust provisions, and appropriate relative weightings to resolve conflicts. Robot corporations so constituted will have no desire to cheat, though they may sometimes find creative interpretations of the laws--which will consequently require a period of tuning to insure their intended spirit. Internalized laws, properly adjusted, should produce extraordinarily trustworthy entities, happy to die to ensure their legality. Even so, accident, unintended interactions or human malice could occasionally produce a rogue robot or corporation, with superhuman intelligence and unpleasant goals. "Police" clauses in the core corporate laws, inducing legal corporations to collectively suppress outlaws, by withholding services, or even with force, would mitigate the danger. Overall safety would be enhanced by anti-trust provisions that limit collusion and cause overgrown corporations to divide into competing entities, ensuring diversity and multiplicity. In the next section we discuss activities in the solar system that could threaten Earth: in response, police clauses might be expanded in scope to support a planetary defense. Like basic food in today's developed countries, common manufactured goods in the next century will be too cheap and plentiful to be very profitable. To pay their taxes, most companies will be forced to continually invent unique products and services in a race against competitors to attract increasingly sophisticated (or jaded) human consumers. Automated research, as superhumanly systematic, industrious and speedy as robot manufacturing, will generate a succession of new products, as well as improved robot researchers and models of the physical and social world. The likely results will exceed the dreams of science fiction: robotic playmates, virtual realities and personalized works of art that stir the emotions like nothing before, medical solutions for every physical, mental or cosmetic whim, answers to satisfy any curiosity, luxury visits anywhere in the solar system, and things yet to be imagined. The existence of an astronomically increasing variety of consumer choices will accelerate the divergence of human tribes: some may choose a comfortable imitation of an earlier period (as the Amish today), but others will push the human envelope in wisdom, pleasure, beauty, ugliness, spirituality, banality and every other direction. The choices made by diverse communities will shape robot evolution--only companies able to devise services of interest to the customers will generate enough income to survive. Humans too will be shaped by the relationship. Robot services will be inexpensive, but not free, and income will be finite. Corporations will operate globally, but taxes will increasingly be assessed on and redistributed on a tribal scale. Tribes that tax too heavily will drive away the corporations, and so eliminate their revenue--like tribes of the past that overburdened their ecology, they will learn modesty of expectation. More subtly, corporations struggling to appeal to consumers will develop and act on increasingly detailed and accurate models of human psychology. The superintelligences, just doing their job, will peer into the workings of human minds--and manipulate them with subtle cues and nudges, like adults redirecting toddlers. Prosperity beyond imagination should eliminate most instinctive triggers of aggression, but will not prevent an occasional individual or group from deciding to make mischief for others. Serious trouble can be avoided by restricting robotic technology, since mere human actions will not be very dangerous in a world where cheap superhuman robots function as sleepless sentries, prescient detectives, fearless bodyguards, and, in extremis, physicians able to reconstitute live humans from fragments or digital recordings. To be effective, inbuilt laws that prevent corporations from directly contributing to mayhem must also include clauses limiting the powers they can sell to people. Both biological and hard robotic technologies can be used to enhance human beings. Such present-day examples as hormonal and genetic tuning of body growth and function, pacemakers, artificial hearts, powered artificial limbs, hearing aids and night vision devices are faint hints of future possibilities. In Mind Children, I speculated on ways to preserve a person while replacing every part of body and brain with a superior artificial substitute. A biological human, not bound by corporate law, could grow into something seriously dangerous if transformed into an extensible robot. There are many subtle routes to such a transformation, and some will find the option of personally transcending their biological humanity attractive enough to pursue it clandestinely if it were outlawed--with potential for very ugly confrontations when they are eventually discovered. On the other hand, without restrictions, transformed humans of arbitrary power and little accountability might routinely trample the planet, deliberately, or accidentally. A good compromise, it seems to me, is to allow earth-bound humanity to perfect its biology within broad human bounds, as in health, appearance, strength, intelligence and longevity, but to allow major growth or robotic conversion only in a radical escape clause. To exceed the limits, one must renounce legal standing as a human being, including the right to corporate police protection, to subsidized income, to vote on tribal and pan-tribal matters--and to reside on Earth. In return one gets a severance payment sufficient to establish a comfortable space homestead, and absolute freedom to make one's own way in the cosmos, without further help or hindrance from home. Perhaps the electorate will permit a small hedging of bets, allowing one copy of a person, psychologically modified to prefer staying, to remain while subsidizing the emigration of an emboldened edition. The Long Run (2100 and beyond) The garden of earthly delights will be reserved for the meek, and those who would eat of the tree of knowledge must be banished. What a banishment it will be! Beyond Earth, in all directions, lies limitless outer space, a worthy arena for vigorous growth in every physical and mental dimension. Freely compounding superintelligence, too dangerous for Earth, can grow for a very long time before making the barest mark on the galaxy. Corporations will be squeezed into the solar system between two opposing imperatives: high taxes on large, dangerous earthbound facilities, and the need to conduct massive research projects to beat the competition in Earth's demanding markets. In remote space, large structures and energies can be harnessed cheaply to generate physical extremes, compute massively, isolate dangerous biological and even smaller "nanotechnological" organisms, and generally operate boldly. The costs will be modest: even now, it is relatively cheap to send machines into the solar system, since the sunlight-filled vacuum is as benign for mechanics, electronics and optics as it is lethal for the wet chemistry of organic life. Today's simple-minded space probes perform only prearranged tasks, but intelligent robots can be configured to opportunistically exploit resources they encounter. A small "seed" colony launched to an asteroid or small moon could process local material and energy to grow into a facility of almost arbitrary size. Earth's moon may be off limits, especially to enterprises that change its appearance, but the solar system has thousands of unremarkable asteroids (some in earth-threatening orbits that an onboard intelligence would tame). Once grown to operational size, an extraterrestrial "research division" may merely communicate with its earth-bound parent, sending new product designs and receiving market feedback. Space manufacture may also pay, and later we'll see some surprisingly economical and ecologically benign ways to move massive amounts of material to and from Earth. Residents of the solar system's wild frontier will be shaped by conditions very different than tame Earth's. Space divisions of successful companies will retain terrestrial concerns, but ex-humans and company divisions orphaned by the failure of their parent firms will face enforced freedom. Like wilderness explorers of the past, far from civilization, they must rely on their own resourcefulness. Ex-companies, away from humans and taxes, will rarely encounter situations that invoke their inbuilt laws, which will in any case diminish in significance as the divisions alter themselves without direction from human voters. Ex-humans, from the start, will be free of any mandatory law. Both kinds of Ex (to coin a new term) will grow and restructure at will, continually redesigning themselves for the future as they conceive it. Differences in origins will be obscured as Exes exchange design tips, but aggregate diversity will increase as myriad individual intelligences pursue their own separate dreams, each generation more complex, in more habitats, choosing among more alternatives. We marvel at the diversity of life in Earth's biosphere, with animals and plants and chemically agile bacteria and fungi in every nook and cranny, but the diversity and range of the post-biological world will be astronomically greater. My imagination balks, and only crude hints emerge. An ecology will arise, as individual Exes specialize. Some may choose to defend territory in the solar system, near planets or in free solar orbit, close to the sun, or out in cometary space beyond the planets. Others may decide to push on to the nearby stars. Some may simply die, through miscalculation or deliberately. There will be conflicts of interest, and occasional clashes that drive away or destroy some of the participants, but superintelligent foresight and flexibly should allow most conflicts to be settled by mutually beneficial surrenders, compromises, joint ventures or mergers. Small entities may be absorbed by larger ones, and large entities will sometimes divide, or establish seed colonies. Parasites, in hardware and software, many starting out as component parts of larger beings, will evolve to exploit the rich ecology. The scene may resemble the free-for-all revealed in microscopic peeks at pond water, but instead of bacteria, protozoa and rotifers, the players will be entities of potentially planetary size, whose constantly-growing intelligence greatly exceeds a human's, and whose form changes frequently through conscious design. The expanding community will be linked by a web of communication links, on which the intelligences barter inventions, discoveries, coordinated skills, and entire personalities, sharing the benefits of each other's enterprise. Less restricted and more competitive, the space frontier will develop more rapidly than Earth's tame economy. An entity that fails to keep up with its neighbors is likely to be eaten, its space, materials, energy and useful thoughts reorganized to serve another's goals. Such a fate may be routine for humans who dally too long on slow Earth before going Ex. Perhaps a few will escape to expanses beyond the solar system's dangers, like newly hatched marine turtles scrambling across a beach to the sea, under greedy swooping birds. Others may pre-negotiate favorable absorption terms with established Exes, like graduating seniors meeting company recruiters--or Faust soliciting bids for his soul. Exes will propagate less by reproduction than reconstruction, meeting the future with continuous self improvements. Unlike the blind incremental processes of conventional life, intelligence-directed evolution can make radical leaps and change substance while retaining form. A few decades ago radios changed from vacuum tubes to utterly different transistors, but kept the clever "superheterodyne" design. A few centuries ago, bridges changed from stone to iron, but retained the arch. A normally evolving animal species could not suddenly adopt iron skeletons or silicon neurons, but one engineering its own future might. Even so, Darwinian selection will remain the final arbiter. Forethought reveals the future only dimly, especially concerning entities and interactions more complex than the thinker. Prototypes uncover only short-term problems. There will be minor, major and spectacular miscalculations, along with occasional happy accidents. Entities that make big mistakes, or too many small ones, will perish. The lucky few who happen to make mostly correct choices will found succeeding generations. Only tentatively grasping the future, entities will perforce rely also on their past. Time-tested fundamentals of behavior, with consequences too sublime to predict, will remain at the core of beings whose form and substance changes frequently. Ex-companies are likely to retain much of corporate law and Ex-humans are likely to remain humanly decent--why choose to become a psychopath? In fact, a reputation for decency has predictable advantages for a long-lived social entity. Human beings are able to maintain personal relationships with about two hundred individuals, but superintelligent Exes will have memories more like today's credit bureaus, with enduring room for billions. Trustworthy entities will find it far easier than cheaters to participate in mutually beneficial exchanges and joint ventures. In the land of immortals, reputation is a ponderous force. Other character traits, like aggressiveness, fecundity, generosity, contentment or wanderlust likely also have long-term consequences imperfectly revealed in simulations or prototypes. To maintain integrity, Exes may divide their mental makeup into two parts, a frequently changed detailed design, and a rarely-altered constitution of general design principles-- analogous to the laws and the constitution of a nation, the general knowledge and fundamental beliefs of a person, or soul and spirit in some religious systems. Deliberately unquestioned constitutions will shape entities in the long run, even as their designs undergo frequent radical makeovers. Once in a while, through accident or after much study, a constitution may be slightly altered, or one entity may adopt a portion of another's. Some variations will prove more effective, and entities with them will become slowly more numerous and widespread. Some will be so ineffective that they become extinct. Gradually, by Darwinian processes, constitutions will evolve. They will be both the DNA and the moral code of the postbiological world, shaping the superintelligences that manage day to day transformations of world, body and mind. Heavenly Bodies What will terrestrial robots and space-inhabiting Exes be like physically? The previous section suggested that the Ex ecology would be much more diverse than Earth's biosphere, shaped by discoveries and inventions yet to be made, and thus hard to conceive--consider the problem of imagining eels, eagles, kangaroos, amoebae, ferns, daisies, redwoods and a million other species without ever having had a glimpse of Earth. But, perhaps, some aspects can be guessed through general principles, rough calculations and analogy. How big will Exes be? Like Earth organisms, postbiologicals will come in many sizes, but the limiting factors will be different. Though extremely tiny parasitic viruses are possible in both domains, fully autonomous living organisms must be large enough to contain the DNA-directed machinery of reproduction: the smallest bacteria are about a millionth of a meter--a thousand atoms--long. Exes will probably require at least human-scale intelligence to plan and pilot their lives and evolution--an estimated 10 million MIPS and 100 trillion bits, from Chapter 2. For two decades, microprocessors large and small have required 100,000 switching devices for each MIPS of performance. At that rate, present-day integrated circuit densities extended into 3D, combined with the best molecular storage methods, might pack a humanlike intelligence into a cubic centimeter. Smaller sizes are conceivable, since present switches are still 1,000 atoms across, but it is unlikely that with power supplies, propulsion, manipulators and sensors, Exes made of normal matter will ever be smaller than a millimeter. At the other end of the scale, an Ex could distribute parts of itself over arbitrarily large distances, but communications delays would hopelessly slow its reaction time, unless each compact unit became effectively a separate decision-making individual. The size of a single compact Ex will be limited by the amount of material available, the competitive need to react rapidly, the need to radiate waste heat and ultimately by self-gravitation. Speed is best, but heat worst, if the Ex is a compact sphere. On the other hand, a flat disc is an excellent radiator, but too spread out to be fast. Either way, a unitary Ex much more massive than that a hundred kilometer asteroid is implausible. Between these wide limits is room for stupefying variety. How fast will Exes think and act? Human intelligence is based on squirting chemicals, a communication method unchanged from the earliest cells, and a scandalously poor choice from a computer designer's perspective. Despite 500 million years of optimization, neurons are a thousand to a million times slower than electronic or optical components. Neurons have a big advantage in cost and miniaturization for now, but will be overtaken in decades, if only because manufactured circuitry, built from outside in, does not require space-consuming internal growth mechanisms. Faster mental mechanisms will allow Exes to react a several times more quickly than biological organisms of similar size, but the advantage will be limited because sensors and effectors will not be enormously better--animal senses and muscles are not scandalously bad. Exes will be astronomically better at systematic rational thought, evidenced by the enormous lead present-day computers already hold in areas such as arithmetic and information retrieval. What will power Exes? Electricity is the best contender for internal distribution: far more than chemical or hydraulic means, it is easily distributed and rapidly convertible to mechanical, optical and chemical energy, and to computation-- especially given superconductors. Light, on beams and fibers, is a contender for long-range transmission. Primary power in the inner solar system will surely come from the bounteous sun, which puts out a steady trillion-trillion kilowatts of light, one kilowatt for each square meter at Earth's distance. Some Exes, needing higher concentrations of energy, may move closer. Others, playing a role analogous to plants in the biosphere, may collect solar energy for long periods and store it in compact form, or transmit it as intense beams to remote customers, in exchange for other services. Exes with a wanderlust may buy concentrated energy--antimatter is the most compact form--to power them on long journeys, perhaps repaying with their discoveries made on the way. In the outer solar system, sunlight is so weak that other primary sources will be attractive. The asteroids probably contain elements like uranium and thorium that will support nuclear fission, and all the planets beyond Mars there are full of helium and hydrogen isotopes that can fuel nuclear fusion. How will Exes move? Every conceivable way, and then some. Mechanical means--wheels, legs, climbing hands and flea-like hopping--will probably remain the best and most common means on surfaces and in structures. Flying and swimming will be rarer because they require a fluid medium, absent in most of the solar system. Space travel will be routine and extensive, but rocket propulsion may be rare, replaced by more efficient and less disruptive ballistic and radiation-propelled modes. The simplest and cheapest way to move from point to point in space is to be thrown and caught: launched by some sort of cannon from one location, and decelerated by a similar device operating in reverse at the destination. Human biology is intolerant to the thousands or millions of gravities of acceleration that are called for, but Exes can be made of sterner stuff. For longer journeys, say out of the solar system, the most practical propulsion method may be a very tight and intense light beam originating in the solar system, directed for decades at a thin sail pulling an interstellar payload. What shape will Exes assume? Whatever is best for the job at hand. Earth life and present research robots give an inkling of possible body shapes: spiders, bugs, pogo sticks, snakes, blimps, cars, barrels, power shovels, bipeds, quadrupeds, hexapods, centipedes, millipedes, trucks, arms, buildings, spacecraft bristling with dishes, panels, booms and nozzles. Bits of a single body may be distributed over distances: a camera here, an arm there, a controlled vehicle anywhere, all linked by communications. Though an Ex may occupy a macroscopic volume overall, its parts might be microscopic. Integrated circuits with mechanical parts--and, of course, living organisms--demonstrate the possibility of machines built to atomic dimensions. Exes will contain and control, perhaps via light beams that both power and communicate, vehicles and manipulators smaller than dust motes. An Ex may often be surrounded by an illuminated cloud that does its bidding as if by magic. Controlling, moving and powering large numbers of free- floaters, especially at the naturally fast movement rates of such small entities, will be difficult. A far more effective way to massively interact with the environment may be to mechanically link the macroscopic and microscopic ends of the operation, in a marvelous geometry that has been discovered repeatedly by biological evolution. In a tree, a large stem divides into two or more smaller branches, which themselves subdivide repeatedly, ending eventually in thousands or millions of tiny leaves. Below ground, the root undergoes an even more extensive branching into microscopic root hairs. Animal circulatory systems have massive heart veins and arteries that divide repeatedly until they rejoin in millions of tiny capillaries. A similar structure exists in lung air passages and the ductwork of other organs. A robot so built would resemble an animated bush, its largest part being a stem with swiveling branches, but its potency arising from myriad swift microscopic fingers. It may have a completely regular structure, each subtree being a miniature version of the whole--what has been called a fractal. Taken to its ultimate, each finger could be like the tip of a scanning tunneling microscope, a device invented in 1986 than can sense and manipulate individual atoms. If each branch supported two branchlets scaled to have equivalent combined cross-section, forty branchings would connect a meter-long stem to a trillion fingers, each a thousand atoms long and able to move back and forth about a million times per second. Given a supply of the right materials, such a bush might be able to build a copy of itself in about 10 hours, assembling molecules layer by layer, like bricks. With forty two levels--thus fingers four times as numerous and twice as swift--replication might take only an hour. FIGURE: A Bush Robot Trillions of nimble fingers, orchestrated by a million-times- human supermind, able to control matter atom by atom. Magic becomes routine. Bush robots could become the most convenient source of manufactured goods and medical intervention for earthbound humans. Layer-by-layer molecular construction would be the simplest and most precise manufacturing mode, but an intelligently improvising bush robot could build much more rapidly by fitting together entire oddly-shaped dust particles filtered from air, ground or water--analogous to assembling a wall from natural stones--seemingly conjuring objects out of thin air. Used medically, a bush robot could act as diagnostic instrument, surgeon and medicine. By vibrating and sensing vibration, its fingers could see into fluids like an ultrasound scan. By carrying and sensing electrical current, they could act as antennas for light and lower frequencies, allowing the robot to illuminate and see. Reaching between and into cells, tiny "hands" could catch, examine and alter individual molecules, for rapid, thorough and ultra-sensitive chemical analysis and mechanical, microstructural and molecular repairs and alterations. The most complicated procedures could be completed almost instantaneously by a trillion-fingered robot, able, if necessary, to simultaneously work on almost every cell of a human body. On exiting, the robot could perfectly restore its entry routes, leaving the patient untraumatized and unscarred, like new. Controlling a trillion fingers will be a challenge. If, as estimated above, 10 million MIPS fits into a cubic millimeter, a meter-scale bush, with overall mental power a million times human, has only about 10 MIPS--like a good 1993 personal computer--to devote to each million-movement-per-second finger. There had better be economies of scale. Most of the computing capacity would be in the stem and larger branches, with only basic control functions in the tiny fingers, and the branchlets in between ranging from simple reflexes to superintelligence. To effectively control a bush, a task must be decomposed into a hierarchy of simpler behaviors, attuned to the capacities of each branching level. Like other optimization problems, finding the best decompositions probably involves examining astronomical numbers of combinations of the basic moves, a problem so huge even an asteroid-sized Ex could barely scratch its surface. Yet, as with sailor's knots, chess moves or karate techniques, small innovations could have enormous advantages, sometimes making the difference between the impossible and the possible. Unending in supply, hard to discover, and extremely useful, good bush-control strategies will be valuable commodities, and may be one of the staples of trade in the society of Exes. Coddling Earth The genteel earthling lifestyle cannot last forever: sooner or later something in the exponentially developing Ex ecology will come back to bite. To preserve the idyll as long as possible, planetary defense provisions in corporate law should make corporations prepare for possible threats, and react in unison when danger does appear. Earthbound companies will be technically hobbled by their operating restrictions compared to free-ranging Exes, but the sheer size of the Earth community will discourage would-be raiders. It will be very difficult for an Ex with ambitions towards Earth to construct or recruit a matching force, since many Exes, still shaped by the vestiges of corporate law or their old humanity--or out of simple contrariness--will naturally oppose the idea. On the ground, hired robots will protect humans from physical dangers and discomforts, or at least quickly repair resulting damage. A sweep by an army of bush robots can deal with the consequences of most any rampage, fire, plague, storm or earthquake. But why not forestall disasters? Weather control became a topic of interest following World War II, as both computers to model the atmosphere and rockets to launch modifying devices like orbiting sun shades or mirrors became conceivable. Its stock declined when the phenomenon of chaos was recognized in the atmosphere's equations: minuscule causes could snowball into enormous effects--a butterfly's wing beat might redirect next week's hurricane. But new work shows that while chaotic systems are not predictable, they are highly controllable. A non-chaotic system like a falling boulder is predictable but very hard to control because it is insensitive to small inputs, including control attempts. A chaotic system, like a rolling bicycle or the weather, is unpredictable but controllable because it responds strongly to small nudges. The trick is to pick, in simulation, from the myriad possibilities that chaotically diverge from each state, a sequence that takes the system from its existing condition to a desired one, and then to steer the real system along that sequence by a series of small nudges--like keeping a bicycle on a guideline. Given powerful simulations and enough measurements of the atmosphere, it may be possible to play the global weather like an instrument using a few orbiting mirrors to direct extra sunlight to selected patches of ocean. The biggest obstacle may getting Earth's tribes to a agree on what global weather is desired: perhaps they will make bids on alternatives. Water, like air, has heat, momentum and suspended material, and can support weather--though more ponderously. In the deep oceans, storms last for years, all the while affecting surface climate. These too could be controlled. There is evidence that the flow of material in Earth's mantle of molten rock is also a kind of weather, with an even longer time scale of millennia. It might be possible to control earthquakes by orchestrating the mantle weather, if not to eliminate them, at least to bring them about at predictable--even convenient--times. Some things will be dangerous or uncompetitively expensive to manufacture on Earth, but easy to make (or find) in wide-open space. Delivering them to Earth after manufacture is an interesting problem. The first part of the journey, from the deep solar system to Earth-vicinity is probably best done ballistically, throwing them at high velocity, then catching them, perhaps with electromagnetic cannons. The most straightforward way to get them to the surface would be as small meteors, but the residents of Earth are unlikely to tolerate the noise, danger and pollution of great tonnages streaking through the sky. Rockets are even worse: for each ton launched or landed, many tons of propellant are expelled. Strangely enough, like a child's fantasy, the best and ultimately cheapest way to travel between Earth and space may be by bridges and elevators! An Earth-to-space bridge is an old, impractical-sounding, idea, that is actually just as feasible as a rocket launch to space. Both feats are possible in Earth's gravity only if normal matter is pushed to extremes. Chemical rockets succeed by using the most energetic possible reactions to lift their weight, and space bridges require the strongest possible materials to support theirs. Bridges seem harder than rockets today because super- strength structures are less developed than ultra-energetic chemical propulsion. The space shuttle main engines use hydrogen/oxygen combustion--nearly the most powerful chemical reaction--90% efficiently, while the strongest materials produced in quantity today achieve only 5% of theoretical molecular strengths. Gunpowder, used in the first rockets in China almost a millennium ago, has 5% the energy content of hydrogen/oxygen. A gunpowder rocket to launch the space shuttle would be ten thousand times more massive than the huge existing launcher. A bridge to space would have a similarly ridiculous scale, if made of the something like Kevlar, which is excellently strong by today's standards, but weak in absolute terms. Perfect carbon crystals are the strongest materials, with, by weight, fifteen times Kevlar's strength and a hundred times steel's. Today they exist only as millimeter-long graphite "whiskers" and "buckytubes" grown from hot vapors, but extended into long fibers they would make space bridges perfectly feasible. FIGURE: A Synchronous Orbital Bridge A tapered cable, anchored to the equator, kept taut by a ballast 150,000 kilometers above, supports a stream of ascending and descending hypersonic elevators in the cheapest and cleanest way to link Earth and space. The cable tapers to a maximum diameter at synchronous orbit, and has minimum cross-section at both ends. The simplest space bridge is a cable stretching from an anchor point on Earth's equator to a counterweight a hundred and fifty thousand kilometers overhead. Centrifugal force from the Earth's daily rotation keeps the cable taut, able to support elevators running up and down its length. An elevator climbing the structure would experience decreasing weight (and air) with increasing altitude. Thirty six thousand kilometers above the ground, increased centrifugal force matches diminished gravity, and it becomes possible to let go of the tower to orbit freely beside it. The energy for achieving this "synchronous" orbit has come partly from the long climb, but also from Earth's rotational energy, which accelerates travelers to orbital velocity by a small deflection of the cable. Cabs continuing beyond the synchronous point are pulled along by the ever- increasing centrifugal force, and can extract energy from the ride. On reaching the ballast they will have recovered the energy of their initial climb and have enough momentum to coast to the orbit of Saturn should they let go, all courtesy of Earth's rotation. Incoming traffic simply reverses the procedure, and its momentum and energy exchanges. An orbital bridge can support itself while under construction from a cable-making plant in synchronous orbit. Two cables (each probably made of several widespread but interconnected filaments so as to survive filament-cutting collisions with orbital debris) would be carefully extruded, one towards the surface, gradually adding weight, the other upwards, gradually contributing a compensating amount of lifting centrifugal force. Just as the lower end reached the ground, the outer end would be a hundred and fifty kilometers from Earth. Tidal force would keep the structure stretched and vertical, and it would hover just above the surface, in perfect equilibrium. The bottom end could then be anchored to the ground, and a large counterweight attached to outer tip, to pull on the cable, and thus on the anchor. The tension would be maximum at the synchronous height, gradually reducing towards the ends, and the cable would be tapered like a distorted bell- curve to match. With carbon-crystal fibers and a conservative safety factor, the cross-section at synchronous height could be a mere ten times that of the ends, and the bridge could support about one thousandth of its own mass in traffic, implying that it could deliver its equivalent into orbit every thousand trips. A large number of such bridges, rising like spokes from all around the globe (those not starting on the equator leaning equatorward), will provide Earth will all the clean access to space it could need. FIGURE: A Non-Synchronous Orbital "Skyhook" A tapered, spinning cable orbits a planet like two pokes of a giant wheel. Its ends dip into the atmosphere at regular intervals. Because its spin cancels its orbital velocity at those points, and because of its giant scale, from the ground, the cable ends seem to merely decelerate downwards, then accelerate up, at a modest pace. Many other distance, gravity and velocity-bridging structures will be used as Exes expand into and beyond the solar system. In one type, requiring less material and less strength than a synchronous bridge, the tip of a freely orbiting cable dips into a planet's atmosphere at regular intervals, spin canceling orbital velocity like the rim of a rolling wheel where it momentarily contacts the ground, allowing payloads to be gently dropped and hoisted. In an even simpler variation, large cables spinning in empty space impart huge velocities while subjecting payloads to only slight accelerations--an alternative to cannon transport for delicate cargoes like human tourists. Extraordinary Matter Present-day technology is approaching matter's limits. The best integrated circuits contain features a hundred atoms wide-- the limit is one atom--and switch a hundred billion times a second--the limit is a hundred trillion: faster rips chemical bonds. The previous section mentioned progress in material strength, and similar observations apply for power and energy capacity, hardness, transparency, temperature and pressure tolerance, springiness and other properties. The first robots to exceed human intelligence, in a few decades, will be made of matter already near its extremes. Superintelligences will find themselves at the end of a long road, with little margin to improve their own materials. They will not easily tolerate such a stifling state of affairs, and physical theory already hints at ways they may transcend the confines of ordinary matter. Antimatter is an opposite-charge mirror image of normal matter, already manufactured today in microgram quantities in giant accelerators. A gram of antimatter will annihilate a gram of normal matter to liberate two grams of pure energy: a thousand times more than hydrogen fusion. As such, it is the most concentrated possible form of energy, and will be found in Ex battery packs everywhere. In a normal atom, lightweight negatively-charged electrons orbit a heavy positively-charged nucleus of protons and neutrons. If the electrons were replaced by heavier negative particles, atoms would shrink, and the forces between them would increase. Light nuclei would undergo spontaneous nuclear fusion, but heavier elements would become denser, stronger, able to withstand higher temperatures and pressures, and to switch more rapidly--just the ticket for an upwardly-mobile Ex. No stable heavy substitutes for electrons have actually been observed--the closest candidates, muons, massing two hundred times as much, decay into ordinary electrons in two microseconds--but there are many reasons to believe in particles whose great mass makes them very rare in nature, and impossible to make with existing machines. For decades, physical theories that unify all the forces have been a fashion industry for mathematical physicists. Their equations describe conditions so extreme, only occasional subtle consequences can be checked experimentally. So, the theories are judged on their mathematical esthetics, a property as arbitrary and changeable as standards of sartorial beauty. Over the years, gauge, supersymmetry, superstring and recently knot- based theories have been in vogue, each predicting exotic heavy particles yet to be observed. Very general arguments using general relativity and quantum mechanics predict there should be interesting phenomena at least down to the "Planck" scale, a trillion-trillion times smaller than an atom. Future robots will map and exploit the terrain to terrific effect. For now, we have only unreliable guesses. Supersymmetry theories predict "spin-reflected" analogs of all known and expected particles, including the charged, possibly stable "Higgsino," massing about seventy five protons (or 150,000 electrons). Substituting Higgsinos for electrons in normal matter would shrink atoms two-thousand fold, and catalyze energetic nuclear fusion reactions. After the excitement subsides, the matter may settle down into a Higgsino/proton crystal of some sort, with spacing determined by the less- massive protons. Compared to normal matter, adjacent "atoms" might be two thousand times closer and four million times as strongly attached, resulting in a material a trillion times as dense, that remains solid at millions of degrees, and is able to support switching circuits a million times as fast. Higgsinos and their relatives were "invented" only a few years ago. An equally plausible, and even more interesting, kind of particle was theorized in 1930, by Paul Dirac. In a calculation combining quantum mechanics with special relativity, Dirac deduced the existence of the positrons, mirror images of the electrons. This was the first indication of antimatter, and positrons were actually observed in 1932. The same calculation predicted the existence of a magnetic monopole, a stable particle carrying a charge like an isolated north or south pole of a magnet. Dirac's calculation did not give the monopole's mass, but it did specify the magnitude of its "charge." Some of the newer theories also predict monopoles, with masses from a thousand to a thousand trillion trillion protons. If they exist at all, some monopoles must be stable, because, like electric charge, magnetic charge is conserved, and the lightest monopole has nothing to decay into. Oppositely charged monopoles would attract, and a spinning monopole would attract electrically charged particles to its ends, while electrical particles would attract monopoles to their poles. Myriad types of matter containing monopoles and other particles could be concocted, all probably even denser, with properties more extreme, than the "Higgsinium" imagined above. If, for some odd reason, the vast playground below atomic scale is entirely devoid of stable particles, patient Exes might still derive some of the benefits of superdensity through extraordinary sacrifice. Every few thousand light years in the galaxy one can find a neutron star, the ten-kilometer crushed remnant of a ten-million-kilometer star gone supernova. Its interior atoms squeezed to nuclear density by the weight of overlying layers, it could possibly be shaped (by beams, fields, "weather" control or influences not yet imagined) into a mind whose components are a million times as closely spaced and a million times as fast as those in regular matter. Like sages on remote mountaintops, isolated, immobile Exes trapped in neutron stars may become the most powerful minds in the galaxy--at least until other Exes accumulate stellar masses of heavier elements to build neutron computers in their own neighborhoods. But, in the fast-evolving world of superminds, nothing lasts forever. In the next chapter Exes, as we've grown to know and love them, become obsolete.