Beyond: Our Future in Space (3 page)

The next level of development involves play. When children say, “Let’s pretend,” they conjure up alternative worlds and populate them with imaginary friends. As we all know, these imaginary worlds can be very elaborate. Such behavior is uniquely human. Jane Goodall only spotted a few examples of pretend play in many hours of observing the Gombe chimpanzees in Tanzania, while it would be trivial to note this behavior in any four-year-old. Conceptually, children engage in counterfactual thinking—speculation beyond normal experience. This is a step beyond making mental models of the actual world to making mental models of strange and unfamiliar worlds. Scientists use counterfactual thinking as a high-level skill for developing theories, by asking, “What might be but isn’t, and why?” Children use it to develop skills that will let them explore the environment they will live in as adults.

We’ve seen that there’s a tight connection between play and abstract, logical thinking in children. Psychologists used to believe that all reasoning involved the use of logic. But real life is usually so messy that rules such as “if this, then that” don’t apply. Logic requires premises and assertions that may be difficult to test. Worse, there may be a huge number of logical inferences from a particular set of assertions, and valid conclusions can be drawn even when they conflict with facts. Human reason isn’t neat or simple, and it bears little resemblance to a proof in logic.

A better description of reasoning is the making of mental models to represent phenomena we encounter. A mental model is like a simulation of some aspect of the world fleshed out by our knowledge and informed by our experience. It’s a dynamic process in which we readily adapt or discard models that are found wanting.
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We test our models with hypothetical situations, making a multitude of mental models for all the possible situations we might face. It’s easy and cheap—we don’t need any equipment or tools and we don’t need to put ourselves in danger. “If I climb out on the tree branch to get the honey, the branch might break and the bees might sting me. But if I snag the branch with a vine, I can break it and come and get the honey when the bees have dispersed.” Everything happens in our heads!

Scholars argue vigorously about when abstract thought and reasoning first emerged. After all, it’s hard enough to know what your spouse or best friend is thinking, let alone an early ancestor who’s been dead for a hundred thousand years.

There’s wide agreement that humans were anatomically modern about 200,000 years ago. Until a few decades ago, the conventional wisdom dated creative, abstract thought to about 40,000 years ago, after humans left Africa and radiated across Europe and Asia and around the same time developed the 7R mutation. Scientists date the earliest examples of cave paintings, as well as bones and stones carved into artwork and tools, to about this period. The relatively sudden emergence of language and modern human behavior has been called the “Great Leap Forward.” Attributes that make us modern are summarized by the American neurophysiologist William Calvin as the behavioral
b’s
: blades, beads, burials, bone tools, and beauty.
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The last item implies aesthetic judgment and forms of representation that include playing games, telling stories, and creating art and music.

But recent discoveries have cast doubt on this hypothesis. In a cave above the windswept coast of South Africa, archaeologists found an abalone shell containing a dried paste made from charcoal, iron-rich dirt, crushed animal bones, and an unknown liquid. The shell was a prehistoric paint can. In eastern Morocco, carved and painted shells were found that had been used as decorative beads. Elsewhere in Africa are several sites where complicated animal snares and traps were discovered. All three types of artifact date from about 80,000 years ago, and there are even earlier hints of abstract thinking. This evidence points to a gradual accumulation of knowledge, skills, and culture over several hundred thousand years, rather than a “Great Leap Forward.”

Regardless of
when
we evolved these uniquely human capabilities, renowned psychologist Steven Pinker put his finger on a problem, the problem of
why
. He wonders, “Why do humans have the ability to pursue abstract intellectual feats such as science, mathematics, philosophy, and law, given that the opportunities to exercise these talents did not exist in the foraging lifestyle in which humans evolved, and would not have parlayed themselves into advantages in survival and reproduction even if they did?”
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In other words, in our modern culture math and science get applied in myriad ways to help us master our environment and live longer, but abstract concepts have no utility to a hunter-gatherer who must find food and shelter daily.

Pinker and other evolutionary psychologists speculate that these traits emerged as a by-product of natural selection. In this view, we occupy a “cognitive niche” in evolution not shared by any other species.
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We manipulate the environment and form complex social networks so we can meet environmental challenges quickly, while animals use the much slower process of genetic evolution. For example, our dexterity let us create new tools and hunting strategies that were most effective when used cooperatively. Meanwhile, our language permitted the evolution of sophisticated behaviors like altruism and reciprocity, and mental models let us efficiently play out hypothetical scenarios before seeing how they operate in the real world. An adaptation useful for one purpose might prove to be useful for another. For example, meat is a concentrated source of nutrients for an opportunistic omnivore, but bringing down an animal takes more smarts than gathering berries, so eating meat would facilitate greater intelligence. Our social, mental, and physical capabilities coevolved. It’s a difficult idea to prove, but it does explain how abstract reasoning could evolve even if it played no immediate role in survival.

Many Worlds

Imagine being transported back in time 2,500 years and across the world to a bustling port on the Ionian coast, into the company of a philosopher called Anaxagoras (
Figure 3
). An intense and austere young man, Anaxagoras thought that the opportunity to understand the universe was the reason why it was better to be born than not to exist.

Anaxagoras was part of a wave of thinking that held that the Earth was not unique among the many worlds in space.
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To see why this was bold, think about how we regarded the sky for many millennia up until the time of the ancient Greeks. The sky was a map, a clock, a calendar, and a repository of myth and legend. It seemed obvious that the Earth was stationary and at the center of the universe while the heavens wheeled overhead. The Sun, the Moon, the planets, and the stars were remote and inaccessible. Prehistoric humans had the ability to think abstractly and make mental models, but there’s no sign they used this ability to conceive of what lies beyond the Earth.

Anaxagoras moved from Ionia to Athens, where he gravitated toward the center of intellectual life. The great Greek playwright Euripides incorporated Anaxagoras’s theory of mind into his tragedies, and his friend Pericles became the greatest statesman and orator of the Golden Age of Athens. Anaxagoras was prolific in his novel ideas and revolutionary theories. He believed that the Sun was a mass of molten metal much bigger than the Peloponnese peninsula, the Moon was a rock like the Earth that didn’t emit its own light, and the stars were fiery stones. He thought that the Milky Way represented the light of countless stars. He gave physical explanations for the Sun’s seasonal motion, the motions of the stars, eclipses, and the origin of comets. Anaxagoras speculated that the cosmos was originally undifferentiated but contained all its eventual constituents. He saw no logical limits to the formation of structure, so he proposed that there can be endless worlds within worlds, either large or small.
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Original ideas tend to provoke major backlash. Anaxagoras was charged with atheism for proposing a physical and natural explanation for the universe, with no reference to gods or divine intervention, and for daring to suggest that the Sun was as large as Greece. His close friendship with Pericles hurt him because the famous politician had powerful enemies. He avoided death by escaping back to Ionia, where he spent the rest of his life in exile.

The idea of “many worlds” had an antecedent in the work of Thales, often called the father of philosophy, who conjectured that space was infinite, and it continued in the work of the Atomists and Epicureans. Just a few centuries later, the Roman philosopher and poet Lucretius boldly wrote, “In the universe, nothing is only of its kind. In other regions, surely there must be other Earths, other men, other beasts of burden.”
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Greek philosophy sought to replace fear and superstition with rational thought. Humans had long had the capacity for abstraction, but in the hands of the Greeks it was augmented with mathematics and formal rules of logic. Aristarchus used geometry and an understanding of eclipses and lunar phases to deduce that the Sun must be larger than the Earth, and this led him to propose a heliocentric model nearly two thousand years before Copernicus. Eratosthenes combined his knowledge that the Earth was round—from the shape of its shadow in a lunar eclipse—with the way the Sun casts shadows at different places on the Earth’s surface, to estimate the size of the Earth. This philosopher, who had never traveled more than a hundred miles in his life, could understand what was unknown to the early humans who had made epic migrations across the planet.

The philosophers of ancient Greece extended mental models into entirely new regimes. Democritus asked what would happen if he took a sharp knife to a stone and subdivided it over and over again. Logically, the process can continue forever to the infinitely small, or it can end with a fundamental, indivisible unit of matter. He rejected infinitely small particles and hypothesized atoms. Archytas asked what would happen if he went to the edge of space and hurled a spear outward. If the spear met a barrier, it would beg the question of what lay beyond the barrier, so he suggested that space is infinite. Without atom-smashers and telescopes, the Greeks couldn’t resolve these questions, but their “thought experiments” heralded the birth of science.
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Unfortunately for the progress of cosmology, the many-worlds idea was squelched by the countervailing view and intellectual dominance of Aristotle, who believed the Earth was unique and there could be no system of worlds. Aristotle’s Earth-centric view took root because it agreed with common sense—if the Earth was not the center of the universe, it would be moving rapidly, and no motion was apparent. The geocentric cosmology was built into Christian theology, where it was consistent with a special relationship between humans and their Creator. Meanwhile, other religious traditions were more sympathetic to the idea of many worlds. Hinduism and Buddhism preach a multiplicity of worlds with intelligent life inhabiting them.
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In one myth, the god Indra says, “I have spoken only of those worlds within this universe. But consider the myriad of universes that exist side by side, each with its own Indra and Brahma, and each with its evolving and dissolving worlds.”

Powerful ideas grip the imagination. Although the Western intellectual tradition was inhospitable, poets and dreamers speculated about what lay far beyond the Earth. In the second century AD, Lucian of Samosata wrote a romantic fantasy that anticipates modern science fiction.
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“A True Story” told of people transported to the Moon, where they encounter a humanlike race riding on the backs of three-legged birds. In this robust fantasy, people and fantastical creatures populate the planets and stars.

It seemed that speculation about space was the only option. But around the time Copernicus proposed the idea that relegated the Earth to one of many celestial objects, technologies were being developed that would bring space within reach for the first time.

2

Rockets and Bombs

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Middle Kingdom

Gravity is an implacable adversary in our quest to leave Earth’s cradle.

We spend our lives resolutely pinned to the planet. Most people can’t jump higher than their waists and even the best high jumpers couldn’t clear a one-story building. We do better if we throw something smaller than ourselves. A good athlete throwing a stone upward can probably reach a height of about 70 meters or 230 feet.
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Five hundred and fifty years ago, Wan Hu tried to do better. He was a midlevel Ming Dynasty official with an obsession for getting close to the stars. Coming from a rich family, he had a clear path to becoming a high government official, but bureaucracy bored him. Wan Hu was more interested in the Chinese traditions of gunpowder and firecrackers, which had been used for centuries during religious festivals and for entertainment. He also yearned to have a bird’s-eye view of the world. Dressed in his finest clothes, Wan Hu sat in a sturdy bamboo chair with forty-seven rockets attached (
Figure 4
). He held the strings of two kites to guide him on his flight. On his signal, forty-seven assistants lit the fuses and rushed for cover. According to the legend, a tremendous roar was followed by billowing clouds of smoke. When the smoke cleared, Wan Hu was gone.