第 1 章
Unveiling Tomorrow: The Art and Science of Future Thinking
Have you ever wondered why some people seem to anticipate trends years before they happen? Why Elon Musk's dog-eared copy of this book reportedly sits on his bedside table? "Future Stories" has become the silent companion of tech visionaries and policy architects alike, with Barack Obama listing it among his essential reads of 2022. In a world obsessed with prediction yet paralyzed by uncertainty, David Christian offers something rare: a framework for thinking about tomorrow that's both intellectually rigorous and deeply human. The book's central insight-that we navigate the future by looking backward-resonates across disciplines from Silicon Valley to Wall Street. As we stand at what may be humanity's most consequential crossroads, this exploration of how we imagine and shape our collective destiny couldn't be more timely.
第 2 章
The Mystery of What Lies Ahead: Our Fundamental Relationship with Time
We open doors into the future every moment of our lives, yet this fundamental aspect of existence remains strangely mysterious. Most of our thinking actually concerns possible futures, whether we're unconsciously calculating if an oncoming truck will hit us or consciously planning Earth's environmental policies. The future shapes our anxiety, hope, and creativity, yet we have no direct evidence from it-no guides because no one has been there. We enter the future looking backward, like driving while staring into a rearview mirror.
This existential mystery confronts us constantly-many possible futures exist until, in a flash, all but one vanish, leaving us with a single present that quickly freezes into memory. This uncertainty gives life both its terror and its richness. As Cicero noted about Julius Caesar, foreknowledge of one's violent end would make life unbearable, yet we still desperately seek glimpses of what lies ahead.
Philosophers have long distinguished between two fundamental approaches to time with profoundly different implications for understanding the future. The first, following Heraclitus, sees time as a flowing river carrying us through never-ending changes, making the future different from the past and difficult to predict. This aligns with our everyday experience of time and resembles the turbulent world of samsara in Indian traditions. The second approach, closer to Parmenides' view, argues that our sense of flow is an illusion-"real time" is more like a map than a river. From this perspective, change is merely the difference between points on a map, and the future should be knowable because it's already mapped out.
Einstein's special relativity theory further complicated our understanding by showing that time isn't an absolute flow but varies according to each observer's "frame of reference." His 1905 paper demonstrated that the speed of light remains constant for all observers regardless of their motion, which means measurements of space and time must differ between observers. Through thought experiments involving lightning flashes observed from different reference frames, Einstein proved that events simultaneous to one observer may not be simultaneous to another moving at a different speed.
For our understanding of the future, Einstein's theories mean there's no absolute division between past and future-an event in my future may be in your past, depending on our relative positions and movements. His work also affects our understanding of causation, as nothing can travel faster than light, creating "light cones" that define the regions of space-time with which we can have causal connections.
While these philosophical and scientific abstractions might seem remote from daily life, they fundamentally shape how we approach the future. We live in the turbulence of flowing time but yearn for the knowable futures of mapped time. The Bhagavad Gita illustrates this tension through Arjuna, who faces the chaos of an impending battle but receives divine perspective from Krishna that helps him act with serenity. All future thinking involves negotiation between our limited perspective and the wider universe we struggle to comprehend.
第 3 章
The Biological Foundations of Future Thinking
Our relationship to the future is fundamentally shaped by our status as living organisms. Unlike simple entities that may fluctuate randomly in time, complex structures like living things face inevitable breakdown according to the second law of thermodynamics. This creates dramatic tension-the future becomes the realm where they will eventually disintegrate unless they actively work against entropy.
More distinctively, living organisms exhibit apparent purposefulness or agency. Unlike non-living complex structures that survive mechanically, living things actively maneuver through changing environments with creativity and ingenuity. They act as if they want to survive, fighting against entropy with remarkable adaptability. This purposefulness likely emerged through natural selection-a blind, purposeless mechanism that gradually built beings with foresight by equipping organisms with survival tricks and designing them to use these skills.
How can living organisms influence something as intangible as the future? Several principles govern future thinking across all life forms. First, we have no direct evidence from the future, making detailed predictions impossible except in rare, highly predictable phenomena. Second, paradoxically, our only evidence about likely futures comes from the past-we're like Dante's soothsayers with heads twisted backward. This "Nasreddin Hoca method" (named after the Turkish sage who searched for his lost ring under a streetlamp "because that's where the light is") means examining the well-lit past for clues about the hidden future.
Third, unlike historical thinking which cannot change the past, our ideas about the future can actively shape it. Fourth and most fundamental, we can find hints about the future through two main approaches: asking other purposeful beings about their intentions (especially effective for humans with language) and studying past trends to project them forward.
Despite their microscopic size, cells demonstrate remarkably sophisticated future thinking through biochemical mechanisms. All living organisms approach future management with three universal steps: determining preferred futures (their "Utopias"), identifying trends to predict likely outcomes, and taking action to steer toward desired futures.
Even the simplest organisms distinguish between good and bad futures, using algorithms built into their genomes to assess trends. These require both sensors to detect current conditions and memory to compare with past states-suggesting memory may exist primarily to enable future thinking. After gathering information, organisms must act decisively despite uncertainty, then constantly reassess and adjust in a process resembling Bayesian analysis.
E. coli bacteria, though just a few microns long, offer a remarkable window into cellular future management. Inside this microscopic world, the cell's DNA serves as an information repository-a twisted, looping staircase containing four million bases that code for roughly 4,000 different molecules. The cell's goals aren't explicitly labeled but embedded in its genome as instructions for making molecules that facilitate survival and reproduction.
Future management in E. coli involves specialized sensor molecules (up to 10,000 per cell) that can detect about fifty distinct chemicals with remarkable precision. These sensor proteins change shape when capturing target molecules, creating a chemical memory that spreads information throughout the cell. Protein networks like the lactose operon use negative-feedback mechanisms that ensure lactose-digesting proteins are produced only when needed. By linking millions of "and," "or," and "not" switches, even simple cells can perform parallel computations of immense subtlety, calculating probabilities about food availability, temperature, salinity, and movement options.
第 4 章
The Evolution of Nervous Systems and Brains
Animals face more complex future-management challenges than plants because they must move to find food. Unlike plants that passively receive sunlight or fungi that consume the dead, animals must hunt living organisms that actively resist being eaten. This means animals must outwit, outrun, or outmuscle their prey, requiring them to navigate complex environments and solve sophisticated problems.
The animal lifestyle demands clear goals, extensive information gathering, and a diverse repertoire of responses to rapidly changing situations. But it's the middle step of the future-thinking process-analyzing environmental trends-that poses the greatest challenge for animals. This is why they've evolved elaborate nervous systems that allow them to model likely futures with exceptional sophistication.
Animal nervous systems consist of networks of neurons specialized for efficient communication over distances. These come in three main types: sensory neurons that detect information, motor neurons that control muscles, and interneurons that analyze information and compute likely futures. In simple or urgent situations, sensory neurons may bypass interneurons and send orders directly to motor neurons-like when you touch something hot and reflexively pull away.
As animals evolved greater complexity, the proportion of interneurons increased, with more concentrated in specialized computational organs called brains. The worm Caenorhabditis elegans has just 302 neurons divided roughly equally among sensory, motor, and interneurons. But in more complex animals, interneurons predominate, reflecting the growing importance of sophisticated future thinking. As philosopher Patricia Churchland notes, "Prediction is the ultimate and most pervasive of brain functions."
The earliest nervous systems appeared about 600 million years ago during the Ediacaran era. While neurons haven't changed much since then, their computational power has increased dramatically through more elaborate networks. Simple animals like sponges lack neurons entirely, while jellyfish have basic neural networks without central hubs. More complex bilateral animals developed ganglia concentrated at their front ends, eventually evolving into brains. Vertebrates developed the most sophisticated nervous systems, with humans possessing approximately 100 billion neurons capable of executing around 10^15 operations per second-enough to create detailed virtual models of possible futures.
Neural networks help animals model possible futures by collecting sensory information, analyzing it, storing it in memory, comparing it to past experiences, and interpolating missing data. These models are constantly updated and refined, as seen in violinists whose brain areas controlling left-hand fingering grow five times larger than in non-violinists, or London taxi drivers whose spatial mapping regions expand with experience.
Our brains construct "controlled hallucinations"-rich, vivid models of reality built from sensory inputs combined with memories and interpolation. These models fill in gaps (like our visual blind spot) and create coherent representations of the world that help us anticipate what might happen next. However, memories aren't static recordings but reconstructions that change each time they're recalled, leading to phenomena like "hindsight bias" where we believe we predicted events that actually surprised us.
Future-thinking machinery extends beyond neural computation to include emotions-powerful physical responses that energize us for action. Fast thinking provides quick, intuitive responses based on familiar patterns, while slow thinking engages conscious deliberation for complex decisions. This division optimizes performance in most situations, though fast thinking can lead to errors like generalizing from insufficient data.
第 5 章
The Human Revolution in Future Thinking
Humans have revolutionized future thinking through two interconnected evolutionary developments. First, neurological changes gave individual humans exceptional abilities to imagine, plan, and model possible futures. Second, the development of language allowed humans to share and accumulate information collectively, enabling future thinking to evolve rapidly across generations.
Human brains expanded dramatically over the last two million years-from the 300-480 cubic centimeters of modern chimps to 900-1,000 cubic centimeters in Homo erectus/ergaster, and finally to 1,300-1,400 cubic centimeters in modern humans. More significant than raw size is our exceptional brain-to-body ratio and the disproportionate development of our frontal cortex.
This rapid evolution likely resulted from positive feedback loops between brain size and sociability. Living in groups required tracking complex social relationships, anticipating others' actions, and managing obligations-all cognitively demanding tasks that favored larger brains, which in turn enabled more sophisticated social structures.
The expanded human frontal cortex revolutionized future thinking by enhancing working memory, temporal awareness, emotional processing, and planning abilities. This allowed humans to model complex sequences of events, imagine distant futures, and engage in deliberate "slow thinking"-the ability to focus attention and carefully evaluate multiple possible outcomes.
Collective learning transformed human history by enabling our species to share information so precisely that knowledge accumulates across generations. This evolutionary bonus, powered by human language, created an "information-sharing network with formidable collective powers." Language compresses complex ideas into simple words-"Pink elephant!" instantly conjures an image of something never seen-while grammar arranges these packages into stories modeling alternative futures.
Collective learning unleashed three transformative trends: increasing technological power, expanding networks of exchange, and accelerating change. These trends initially worked slowly but have accelerated dramatically, leading Alfred North Whitehead to observe that while change once occurred over timeframes longer than a human life, today it happens faster than a single lifetime, requiring us to "prepare individuals to face a novelty of conditions."
Using our understanding of time's social dimensions, we can reconstruct how our earliest ancestors thought about the future. The foundational era-from the evolution of Homo sapiens to the end of the last ice age-saw humans living in small, nomadic groups with intimate knowledge of their territories. By 10,000 years ago, fewer than six million humans occupied Earth in tens of thousands of tiny communities, each with unique traditions and technologies.
Four key features characterized foundational-era thinking about time and future: First, the future was personal, concerned with local people, animals, and plants rather than global concerns. Second, people saw themselves as living in and with the world rather than dominating it, following ecological and moral laws that required care for the land. Unlike modern societies, they didn't try to manipulate their environment beyond modest interventions like occasional burning to encourage new growth.
Third, beneath the changes of daily life, people imagined a stable, unchanging world-a Parmenidean universe where the past wasn't a chronological timeline but faded into a "dreaming" or "everywhen." In this worldview, the future wasn't mysterious because little truly changed beneath surface ripples. Fourth, future thinking was shaped by belief in spirits and occult forces. Most societies assumed the existence of spirits and gods with whom one could negotiate about the future, just as with other humans.
第 6 章
The Transformation of Future Thinking in Agricultural Societies
The agrarian era (8000 BCE to about 200 years ago) saw spectacular transformations in human societies after hundreds of thousands of years of slow change. Though representing less than one-twentieth of human history, agriculture revolutionized human societies and thinking. The stable Holocene climate allowed agriculture to spread globally, increasing food production and enabling human populations to grow from 6 million to 900 million by 1800 CE.
Three major trends accelerated: new technologies enhanced environmental control; larger exchange networks synergized collective learning; and the pace of change increased, making the future less predictable. Agriculture created a more manipulative relationship with the environment, as farmers rearranged landscapes and altered plants and animals through domestication. New transportation and communication technologies widened exchange networks, while writing multiplied connections between communities and generations.
While most future thinking remained practical and empirical throughout the agrarian era, significant differences emerged between elite and popular approaches. As Cicero noted, practical expertise in prediction-whether from pilots forecasting storms or physicians diagnosing illness-was universally respected. However, divination (attempting to contact and negotiate with spiritual beings) remained widespread at all social levels.
The key distinction was scale. In increasingly stratified societies, ordinary people focused on personal futures, local trends, and local spiritual authorities. Elites, however, needed to consider the futures of entire empires-not just "Will locusts eat our barley field?" but "Will locusts create an empire-wide famine?" This required new knowledge systems and ways of thinking about large-scale trends affecting millions of lives.
The "Axial Age" of the first millennium BCE exemplifies elite future thinking. As trans-Eurasian trade networks and vast empires emerged, rulers sought universal principles beyond local traditions. This spawned philosophical and religious systems aspiring to universal truths rather than merely local ones. Figures like Zoroaster, who conceived of a god whose laws embraced the entire universe, received elite patronage.
When rulers' universalist visions clashed with traditional future thinking, conflicts could turn violent. The dramatic case of Genghis Khan and his shaman Teb Tenggeri illustrates this tension perfectly. Initially allies, with Teb Tenggeri declaring Temujin as Heaven's chosen ruler, their relationship deteriorated as Genghis Khan's horizons expanded beyond traditional Mongol spirituality. The conflict ended violently when Genghis allowed his brother Otcigin to execute the shaman, effectively replacing him as "the empire's voice of heaven's will."
In the Mediterranean world two millennia ago, divination was ubiquitous across all social levels. Greek diviners, borrowing methods from Babylonian and Assyrian traditions, watched birds in flight, studied animal organs, interpreted dreams, and noted unusual events. The most prestigious form of divination came through oracles at sacred sites like Delphi. Consulting the Oracle was an elaborate, expensive ritual-you traveled to Mount Parnassus, purchased sacrificial animals, and paid to receive Apollo's messages through entranced prophetesses whose utterances were interpreted by priests.
In large bureaucratic empires, future thinking necessarily became more impersonal and systematic, as it concerned the fates of entire societies rather than individuals. Historian Lisa Raphals notes that while Greek divination typically addressed questions to particular gods, imperial Chinese practices were "more mechanical, and arguably more naturalistic." In these contexts, future thinking was tightly controlled due to its political significance and often blended with propaganda.
第 7 章
Modern Future Thinking in a Rapidly Changing World
In the modern era-just one-thousandth of human evolutionary history-human future thinking has transformed more dramatically than in all previous eras. Since 1800, the human population has grown ninefold, energy use has increased twenty-five times, and life expectancy has doubled to seventy years. We've entered the Anthropocene epoch, where humans shape planetary futures, making modern future thinking increasingly concerned with the fate of all humanity and other species.
Modern technologies have given humans unprecedented power to shape futures-communicating instantly across vast distances, studying microscopic particles and distant galaxies, and traveling globally in hours. This power creates both opportunities and dangers, as we can now transform atmospheres and oceans or destroy the biosphere with weapons of war. The idea of "progress" has generated a new collective hubris, while globalization has woven nearly eight billion people into a single planetary network, encouraging future thinking on global scales.
Modern science has profoundly reshaped future thinking by replacing an enchanted world of spirits and gods with a mechanical universe governed by impersonal scientific laws. This "disenchantment of the world," as Max Weber called it, emerged from the scientific revolution of the seventeenth century when thinkers like Johannes Kepler began seeing the universe "similar to a clock" rather than "a divine animated Being." Though many pioneers of modern science still believed in God, they rejected the idea that spirits could arbitrarily interfere with natural laws.
Modern future thinking differs from earlier eras in four fundamental ways: better understanding of causation allows more precise prediction in fields like physics and medicine; probability theory offers more precise understanding of statistical processes; vastly increased statistical information enhances our ability to detect and analyze trends; and modern computing technologies enable unprecedented storage and analysis of data.
Understanding why things happen dramatically enhances our ability to predict futures. While identifying trends is useful (like Pavlov's dogs learning that food follows bells), understanding causation allows much more precise prediction. Nineteenth-century discoveries like germ theory revolutionized medicine by revealing that microorganisms cause diseases, leading to sterile environments, vaccines, and antibiotics.
Modern probability theory emerged from gambling to become a cornerstone of scientific future thinking. Beginning with Girolamo Cardano's systematic treatment in the 16th century, probability theory developed into a mathematical framework for understanding uncertain futures. Unlike ancient intuitive approaches, modern probability uses precise mathematical models to analyze sample spaces and calculate likely outcomes.
The third distinctive feature of modern future thinking is the massive collection of information through statistics. While probability theory increases predictive precision, it requires substantial real-world data-the more the better, as explained by Bernoulli's law of large numbers. More information reveals detailed long-term trends essential for good forecasting. Modern statistics emerged in the 17th century when John Graunt created the first life tables based on sixty years of christening and burial records.
The information revolution of the late twentieth century enabled the storage, access, and analysis of massive datasets. Modern electronic computing began during World War II but was initially limited to governments and large corporations. By 2020, a typical smartphone had 1,000 times more computational power than the best 1970 computer at one-thousandth the cost. This computing revolution enabled unprecedented modeling of possible futures.
第 8 章
Imagining Our Collective Future: The Next Hundred Years
The next hundred years represent a timeframe with distinctive features. Some trends can be predicted with reasonable confidence because we can observe regular patterns already in motion, yet most of the future remains obscure due to countless unknowns and unpredictable human choices. This timeframe is personally significant because it will be inhabited by people we know and care about, falling under what Elinor Ostrom calls the "seven generation rule"-the indigenous principle of considering impacts on children's children and beyond when making major decisions.
Despite the diversity of today's world, there are good reasons to believe we can build consensus on a desirable future for humanity. We share the same species, with common needs and increasingly intertwined fates, and global communication networks enable worldwide conversations about our collective future. One promising sign is the substantial ethical overlap between different religious and philosophical traditions. The 1993 Parliament of the World's Religions issued a "Declaration toward a Global Ethic" affirming shared core values across forty religious traditions, including human interdependence, the Golden Rule, and considering humanity as a family.
The Marquis de Condorcet's utopian vision, written during the French Revolution shortly before his death in prison in 1794, stands as one of the most prescient modern utopias. His "Sketch for a Historical Picture of the Progress of the Human Mind" envisioned human improvement along three paths: scientific progress raising living standards, moral progress increasing equality and human rights, and medical advances improving health and longevity.
The remarkable scientific and technological progress since Condorcet's time has made many of his extravagant hopes seem commonplace. In the twentieth century, however, it became apparent that the breathtaking changes of the modern era haven't eliminated limits to growth, but might have brought them closer as humans consume resources on scales threatening the biosphere's stability.
Trend hunting is the fundamental skill of modern future thinking, requiring a delicate balance between generality and detail. We must identify trends most likely to shape our futures while avoiding overprecise predictions that limit options. Good trend hunting requires sensitivity to how trends can twist and turn-rising in straight lines, accelerating exponentially, fluctuating like waves, or flattening into S-curves.
Throughout human history, collective learning has driven powerful rising trends in population, technology, exchange networks, and resource consumption. Some have accelerated dramatically in recent centuries, approaching exponential growth. Energy use demonstrates this spectacularly. While an individual human generates about 150 watts (one-fifth horsepower), ancient technologies like fire or animal domestication raised this to about one horsepower per person. In just two centuries, fossil fuels have increased this to an average of 100 horsepower (73,500 watts) per person.
Despite humanity's gains from growth, we now know many rising trends must be reined in. Some are flattening spontaneously-global economic growth has slowed from 5.5% annually after 1961 to just over 2% after 2011, despite rapid growth in regions like China and India. More dramatically, population growth began slowing in the late 1960s-ironically, just as Paul and Ann Ehrlich published their alarmist "Population Bomb" warning of imminent collapse. Most demographers now expect human population to peak later this century between nine and twelve billion before declining.
Human consumption is devastating Earth's biodiversity. By 2020, humans and their domesticated animals constituted over twenty times the combined biomass of all other land mammals, while domestic chickens outweighed all other bird species combined. The 2019 IPBES report found extinction rates "tens to hundreds of times higher than the average over the past 10 million years and accelerating."
The trends we've examined hint at what may happen in the next hundred years. We've identified powerful growth trends that may now be flattening-a pattern seen when a new complex entity emerges. What's being born is a conscious planet: Earth and its biosphere transformed by a species with enough power to shape its future through conscious activity. Vladimir Vernadsky called this the noosphere-the sphere of human thought-which has suddenly become powerful enough to change Earth's future.
第 9 章
Beyond the Horizon: Middle and Remote Futures
Looking beyond the immediate challenges of the next century, we can consider what awaits our descendants on scales of thousands or even millions of years-the "middle future." While difficult to predict with precision due to the unpredictable nature of purposeful beings like us, tantalizing hints suggest fascinating possibilities.
Our most important contribution is getting through the current bottleneck centuries while we're learning planetary management and possess Armageddon weapons but few off-Earth settlements to serve as refuges. Success would open pathways to the middle future for billions of humans and post-humans. This spectacular potential legacy gives profound meaning to our present moment.
What will planetary management require? Like all complex structures, a conscious planet will need distinctive emergent properties to survive and flourish: coordination and planning at planetary scale; advanced science and technology to solve wickedly complex problems; new educational approaches helping humans understand their collective challenges; and ethical systems motivating people to value a flourishing biosphere for their descendants and billions of other species.
Four crucial technological developments will shape our future: sustainable energy production, nanotechnology, artificial intelligence and robotics, and biological technologies that will transform human bodies into human-machine hybrids with indefinitely long lives.
The modern world was built with fossil fuels, but we now know we can't continue using them. Most promising energy technologies are essentially new ways of mining sunlight. Hydropower taps solar energy indirectly through water flows, wind power uses sun-driven air currents, while solar power mines sunlight directly through artificial photosynthesis already more efficient than natural forms.
Nanotechnology-building machines at molecular scales-promises to revolutionize our world. Biologists are developing nanobots that could enter the body, repair problems, and disassemble themselves like proteins in a cell. Eventually, machines may become invisibly small and so cheap we'll barely notice their cost in money or energy.
Artificial intelligence and robots may prove even more revolutionary than nanotechnology. The crucial question is whether we can maintain control over machines once they surpass human intelligence. Toby Ord considers a "Spartacus rebellion" by smart robots one of the likelier paths to existential catastrophe. Samuel Butler warned in 1863 that "Man will become to the machine what the horse and the dog are to man."
New medical, biological, and genetic technologies will transform not just our environment but ourselves. By the year 3000, the people we'd meet might seem as strange as their technologies and cities. With gene-editing technologies like CRISPR, we can now modify organisms gene by gene. Transhumanists welcome these developments, envisioning cybernetic, biological, and genetic transformations that enhance human capabilities, eliminate discomfort, extend lifespans indefinitely, and blend humans with machines.
Biological diversification will accelerate as humans migrate to other planets and celestial bodies. Given our species' history of exploration, our descendants will inevitably migrate into space, taking other species with them and creating new conscious planetary bodies in a reproduction-like "budding-off" process. As anthropologist Ben Finney notes, "We evolved as an exploratory, migratory animal" capable of adapting to environments through technology rather than biology.
This chapter extends beyond our lineage's future to examine Earth's, the sun's, the galaxy's, and the universe's futures, ending with speculations about the conclusion of the epic that began with the big bang 13.8 billion years ago. Surprisingly, we can sometimes see the shape of the remote future more clearly than the next few centuries, and these glimpses suggest something profound: we live at the beginning of time. Our universe is young, with most of its story still untold.
Plate tectonics are well enough understood to predict Earth's geographical configuration 100-200 million years ahead. With the Atlantic widening while the Pacific and Mediterranean shrink, the Americas will eventually meet East Asia and Australia, while North Africa and Europe will fuse together. In about 200 million years, these movements will form a new supercontinent some call "Amasia," surrounded by a vastly expanded Atlantic Ocean.
Our sun grows larger and hotter as helium accumulates in its core-it's already 10% larger and emitting 40% more energy than at birth. Life has survived this warming because greenhouse gases decreased while oxygen increased, maintaining suitable temperatures. In about a billion years, increasing solar heat will break down atmospheric carbon dioxide, causing plants to suffocate, followed by animals that depend on plant-produced oxygen.
In 3-4 billion years, an even hotter sun will boil away Earth's oceans. Radiation will split water molecules, with hydrogen escaping to space while oxygen combines with materials like iron, causing Earth to rust. When surface temperatures reach 1,000C, rocks will melt and Earth will resemble Venus as even the toughest life-forms perish.
How will it all end? This fundamental question has been asked by all human societies. There are two main possibilities: either the universe is eternal with no end, or it is finite with a definite conclusion. Since the 1960s, most cosmologists have accepted the big bang paradigm, dating the universe's beginning to about 13.8 billion years ago and speculating about its eventual end.
To grasp the scale of modern scientific eschatologies, we can use our sun's lifetime of about nine billion years as a basic unit. The universe has existed for just 1.4 solar lifetimes but is expected to last billions or trillions more. This tells us we live in a young universe, having seen only the first few lines of its story.
In 1998, two teams of astronomers discovered the universe's expansion rate wasn't slowing but accelerating and had been for several billion years. Most cosmologists now attribute this to "dark energy," a poorly understood force that increases expansion as the universe grows. This suggests the universe will expand faster and faster forever.
In this scenario, the universe grows increasingly large, cold, and empty until different regions lose contact because light can no longer bridge the distances between them. Eventually, astronomers would see only their local galaxy group, perhaps puzzled by ancient records claiming billions of galaxies existed. In this fragmented universe, even red dwarf stars will die, leaving only dead stars, black holes, and quantum debris.
Another idea that could rewrite our cosmic story is the "multiverse." Many cosmologists now seriously consider that our universe may not be alone. There are theoretical reasons (though no hard evidence) for imagining big bangs occurring continuously in a multidimensional space even larger than our block-universe. Different universes might have slightly different fundamental attributes-perhaps gravity is stronger or electromagnetism weaker. Some might last seconds, others much longer than ours.
These are fascinating ideas, but we currently have no evidence for them. Our technologies allow observation of only one universe, leaving theories about others based solely on logic and imagination. As astronomers joke when asking students to "Define the universe and give two examples," we have a sample of one. For those studying the future, this joke is painful-though we constantly imagine multiple futures, we only ever experience one.
