Pale Blue Dot: A Vision of the Human Future in Space - Carl Sagan, Ann Druyan (1997)


But tell me, who are they, these wanderers …?


We were wanderers from the beginning. We knew every stand of tree for a hundred miles. When the fruits or nuts were ripe, we were there. We followed the herds in their annual migrations. We rejoiced in fresh meat. Through stealth, feint, ambush, and main-force assault, a few of us cooperating accomplished what many of us, each hunting alone, could not. We depended on one another. Making it on our own was as ludicrous to imagine as was settling down.

Working together, we protected our children from the lions and the hyenas. We taught them the skills they would need. And the tools. Then, as now, technology was the key to our survival.

When the drought was prolonged, or when an unsettling chill lingered in the summer air, our group moved on—sometimes to unknown lands. We sought a better place. And when we couldn’t get on with the others in our little nomadic band, we left to find a more friendly bunch somewhere else. We could always begin again.

For 99.9 percent of the time since our species came to be, we were hunters and foragers, wanderers on the savannahs and the steppes. There were no border guards then, no customs officials. The frontier was everywhere. We were bounded only by the Earth and the ocean and the sky—plus occasional grumpy neighbors.

When the climate was congenial, though, when the food was plentiful, we were willing to stay put. Unadventurous. Overweight. Careless. In the last ten thousand years—an instant in our long history—we’ve abandoned the nomadic life. We’ve domesticated the plants and animals. Why chase the food when you can make it come to you?

For all its material advantages, the sedentary life has left us edgy, unfulfilled. Even after 400 generations in villages and cities, we haven’t forgotten. The open road still softly calls, like a nearly forgotten song of childhood. We invest far-off places with a certain romance. This appeal, I suspect, has been meticulously crafted by natural selection as an essential element in our survival. Long summers, mild winters, rich harvests, plentiful game—none of them lasts forever. It is beyond our powers to predict the future. Catastrophic events have a way of sneaking up on us, of catching us unaware. Your own life, or your band’s, or even your species’ might be owed to a restless few—drawn, by a craving they can hardly articulate or understand, to undiscovered lands and new worlds.

Herman Melville, in Moby Dick, spoke for wanderers in all epochs and meridians: “I am tormented with an everlasting itch for things remote. I love to sail forbidden seas …”

To the ancient Greeks and Romans, the known world comprised Europe and an attenuated Asia and Africa, all surrounded by an impassable World Ocean. Travelers might encounter inferior beings called barbarians or superior beings called gods. Every tree had its dryad, every district its legendary hero. But there were not very many gods, at least at first, perhaps only a few dozen. They lived on mountains, under the Earth, in the sea, or up there in the sky. They sent messages to people, intervened in human affairs, and interbred with us.

As time passed, as the human exploratory capacity hit its stride, there were surprises: Barbarians could be fully as clever as Greeks and Romans. Africa and Asia were larger than anyone had guessed. The World Ocean was not impassable. There were Antipodes.* Three new continents existed, had been settled by Asians in ages past, and the news had never reached Europe. Also the gods were disappointingly hard to find.

The first large-scale human migration from the Old World to the New happened during the last ice age, around 11,500 years ago, when the growing polar ice caps shallowed the oceans and made it possible to walk on dry land from Siberia to Alaska. A thousand years later, we were in Tierra del Fuego, the southern tip of South America. Long before Columbus, Indonesian argonauts in outrigger canoes explored the western Pacific; people from Borneo settled Madagascar; Egyptians and Libyans circumnavigated Africa; and a great fleet of oceangoing junks from Ming Dynasty China crisscrossed the Indian Ocean, established a base in Zanzibar, rounded the Cape of Good Hope, and entered the Atlantic Ocean. In the fifteenth through seventeenth centuries, European sailing ships discovered new continents (new, at any rate, to Europeans) and circumnavigated the planet. In the eighteenth and nineteenth centuries, American and Russian explorers, traders, and settlers raced west and east across two vast continents to the Pacific. This zest to explore and exploit, however thoughtless its agents may have been, has clear survival value. It is not restricted to any one nation or ethnic group. It is an endowment that all members of the human species hold in common.

Since we first emerged, a few million years ago in East Africa, we have meandered our way around the planet. There are now people on every continent and the remotest islands, from pole to pole, from Mount Everest to the Dead Sea, on the ocean bottoms and even, occasionally, in residence 200 miles up—humans, like the gods of old, living in the sky.

These days there seems to be nowhere left to explore, at least on the land area of the Earth. Victims of their very success, the explorers now pretty much stay home.

Vast migrations of people—some voluntary, most not—have shaped the human condition. More of us flee from war, oppression, and famine today than at any other time in human history. As the Earth’s climate changes in the coming decades, there are likely to be far greater numbers of environmental refugees. Better places will always call to us. Tides of people will continue to ebb and flow across the planet. But the lands we run to now have already been settled. Other people, often unsympathetic to our plight, are there before us.

* * *

LATE IN THE NINETEENTH CENTURY, Leib Gruber was growing up in Central Europe, in an obscure town in the immense, polyglot, ancient Austro-Hungarian Empire. His father sold fish when he could. But times were often hard. As a young man, the only honest employment Leib could find was carrying people across the nearby river Bug. The customer, male or female, would mount Leib’s back; in his prized boots, the tools of his trade, he would wade out in a shallow stretch of the river and deliver his passenger to the opposite bank. Sometimes the water reached his waist. There were no bridges here, no ferryboats. Horses might have served the purpose, but they had other uses. That left Leib, and a few other young men like him. They had no other uses. No other work was available. They would lounge about the riverbank, calling out their prices, boasting to potential customers about the superiority of their drayage. They hired themselves out like four-footed animals. My grandfather was a beast of burden.

I don’t think that in all his young manhood Leib had ventured more than a hundred kilometers from his little hometown of Sassow. But then, in 1904, he suddenly ran away to the New World—to avoid a murder rap, according to one family legend. He left his young wife behind. How different from his tiny backwater hamlet the great German port cities must have seemed, how vast the ocean, how strange the lofty skyscrapers and endless hubbub of his new land. We know nothing of his crossing, but have found the ship’s manifest for the journey undertaken later by his wife, Chaiya—joining Leib after he had saved enough to bring her over. She traveled in the cheapest class on the Batavia, a vessel of Hamburg registry. There’s something heartbreakingly terse about the document: Can she read or write? No. Can she speak English? No. How much money does she have? I can imagine her vulnerability and her shame as she replies, “One dollar.”

She disembarked in New York, was reunited with Leib, lived just long enough to give birth to my mother and her sister, and then died from “complications” of childbirth. In those few years in America, her name had sometimes been anglicized to Clara. A quarter century later, my mother named her own firstborn, a son, after the mother she never knew.

OUR DISTANT ANCESTORS, watching the stars, noted five that did more than rise and set in stolid procession, as the so-called “fixed” stars did. These five had a curious and complex motion. Over the months they seemed to wander slowly among the stars. Sometimes they did loops. Today we call them planets, the Greek word for wanderers. It was, I imagine, a peculiarity our ancestors could relate to.

We know now that the planets are not stars, but other worlds, gravitationally lashed to the Sun. Just as the exploration of the Earth was being completed, we began to recognize it as one world among an uncounted multitude of others, circling the Sun or orbiting the other stars that make up the Milky Way galaxy. Our planet and our solar system are surrounded by a new world ocean—the depths of space. It is no more impassable than the last.

Maybe it’s a little early. Maybe the time is not quite yet. But those other worlds—promising untold opportunities—beckon.

In the last few decades, the United States and the former Soviet Union have accomplished something stunning and historic—the close-up examination of all those points of light, from Mercury to Saturn, that moved our ancestors to wonder and to science. Since the advent of successful interplanetary flight in 1962, our machines have flown by, orbited, or landed on more than seventy new worlds. We have wandered among the wanderers. We have found vast volcanic eminences that dwarf the highest mountain on Earth; ancient river valleys on two planets, enigmatically one too cold and the other too hot for running water; a giant planet with an interior of liquid metallic hydrogen into which a thousand Earths would fit; whole moons that have melted; a cloud-covered place with an atmosphere of corrosive acids, where even the high plateaus are above the melting point of lead; ancient surfaces on which a faithful record of the violent formation of the Solar System is engraved; refugee ice worlds from the transplutonian depths; exquisitely patterned ring systems, marking the subtle harmonies of gravity; and a world surrounded by clouds of complex organic molecules like those that in the earliest history of our planet led to the origin of life. Silently, they orbit the Sun, waiting.

We have uncovered wonders undreamt by our ancestors who first speculated on the nature of those wandering lights in the night sky. We have probed the origins of our planet and ourselves. By discovering what else is possible, by coming face to face with alternative fates of worlds more or less like our own, we have begun to better understand the Earth. Every one of these worlds is lovely and instructive. But, so far as we know, they are also, every one of them, desolate and barren. Out there, there are no “better places.” So far, at least.

During the Viking robotic mission, beginning in July 1976, in a certain sense I spent a year on Mars. I examined the boulders and sand dunes, the sky red even at high noon, the ancient river valleys, the soaring volcanic mountains, the fierce wind erosion, the laminated polar terrain, the two dark potato-shaped moons. But there was no life—not a cricket or a blade of grass, or even, so far as we can tell for sure, a microbe. These worlds have not been graced, as ours has, by life. Life is a comparative rarity. You can survey dozens of worlds and find that on only one of them does life arise and evolve and persist.

Having in all their lives till then crossed nothing wider than a river, Leib and Chaiya graduated to crossing oceans. They had one great advantage: On the other side of the waters there would be—invested with outlandish customs, it is true—other human beings speaking their language and sharing at least some of their values, even people to whom they were closely related.

In our time we’ve crossed the Solar System and sent four ships to the stars. Neptune lies a million times farther from Earth than New York City is from the banks of the Bug. But there are no distant relatives, no humans, and apparently no life waiting for us on those other worlds. No letters conveyed by recent emigrés help us to understand the new land—only digital data transmitted at the speed of light by unfeeling, precise robot emissaries. They tell us that these new worlds are not much like home. But we continue to search for inhabitants. We can’t help it. Life looks for life.

No one on Earth, not the richest among us, can afford the passage; so we can’t pick up and leave for Mars or Titan on a whim, or because we’re bored, or out of work, or drafted into the army, or oppressed, or because, justly or unjustly, we’ve been accused of a crime. There does not seem to be sufficient short-term profit to motivate private industry. If we humans ever go to these worlds, then, it will be because a nation or a consortium of them believes it to be to its advantage—or to the advantage of the human species. Just now, there are a great many matters pressing in on us that compete for the money it takes to send people to other worlds.

That’s what this book is about: other worlds, what awaits us on them, what they tell us about ourselves, and—given the urgent problems our species now faces—whether it makes sense to go. Should we solve those problems first? Or are they a reason for going?

This book is, in many ways, optimistic about the human prospect. The earliest chapters may at first sight seem to revel overmuch in our imperfections. But they lay an essential spiritual and logical foundation for the development of my argument.

I have tried to present more than one facet of an issue. There will be places where I seem to be arguing with myself. I am. Seeing some merit to more than one side, I often argue with myself. I hope by the last chapter it will be clear where I come out.

The plan of the book is roughly this: We first examine the widespread claims made over all of human history that our world and our species are unique, and even central to the workings and purpose of the Cosmos. We venture through the Solar System in the footsteps of the latest voyages of exploration and discovery, and then assess the reasons commonly offered for sending humans into space. In the last and most speculative part of the book, I trace how I imagine that our long-term future in space will work itself out.

Pale Blue Dot is about a new recognition, still slowly overtaking us, of our coordinates, our place in the Universe—and how, even if the call of the open road is muted in our time, a central element of the human future lies far beyond the Earth.

*“As to the fable that there are Antipodes,” wrote St. Augustine in the fifth century, “that is to say, men on the opposite side of the earth, where the sun rises when it sets to us, men who walk with their feet opposite ours, that is on no ground credible.” Even if some unknown landmass is there, and not just ocean, “there was only one pair of original ancestors, and it is inconceivable that such distant regions should have been peopled by Adam’s descendants.”






First artificial satellite of the Earth
(Sputnik 1)


First animal in space
(Sputnik 2)


First spacecraft to escape the Earth’s gravity
(Luna 1)


First artificial planet of the Sun
(Luna 1)


First spacecraft to impact another world
(Luna 2 to the Moon)


First view of the far side of the moon
(Luna 3)


First human in space
(Vostok 1)


First human to orbit the Earth
(Vostok 1)


First spacecraft to fly by other planets
(Venera 1 to Venus;


Mars 1 to Mars)


First woman in space
(Vostok 6)


First multiperson space mission
(Voskhod 1)


First space “walk”
(Voskhod 2)


First spacecraft to enter the atmosphere of another planet
(Venera 3 to Venus)


First spacecraft to orbit another world
(Luna 10 to the Moon)


First successful soft landing on another world
(Luna 9 to the Moon)


First robot mission to return α sample from another world
(Luna 16 to the Moon)


First roving vehicle on another world
(Luna 17 to the Moon)


First soft landing on another planet
(Mars 3 to Mars)


First scientifically successful landing on another planet
(Venera 8 to Venus)



First approximately year-long manned spaceflight (comparable to Mars flight time)
(Soyuz 35)


First full orbital radar mapping of another planet
(Venera 15 to Venus)


First balloon station deployed in the atmosphere of another planet
(Vega 1 to Venus)


First close cometary encounter
(Vega 1 to Halley’s Comet)


First space station inhabited by rotating crews




First scientific discovery in space
—Van Allen radiation belt
(Explorer 1)


First television images of the Earth from space
(Explorer 6)



First scientific discovery in interplanetary space
—direct observation of the solar wind
(Mariner 2)


First scientifically successful planetary mission
(Mariner 2 to Venus)


First astronomical observatory in space


First manned orbit of another world
(Apollo 8 to the Moon)


First landing of humans on another world
(Apollo 11 to the Moon)


First samples returned to Earth from another world
(Apollo 11 to the Moon)



First manned roving vehicle on another world
(Apollo 15 to the Moon)


First spacecraft to orbit another planet
(Manner 9 to Mars)


First dual-planet mission
(Mariner 10 to Venus and Mercury)


First successful Mars landing; first spacecraft to search for life on another planet
(Viking 1)


First flybys of Jupiter (Pioneer 10),


Mercury (Mariner 10),


Saturn (Pioneer 11),


First spacecraft to achieve escape velocity from the Solar System
(Pioneers 10 and 11, launched in 1973 and 1974; Voyagers 1 and 2, 1977)



First manned reusable spacecraft


First satellite to be retrieved, repaired,


and redeployed in space
(Solar Maximum Mission)


First distant cometary encounter
(International Cometary Explorer to Comet Giacobini-Zimmer)


First flybys of Uranus (Voyager 2),


Neptune (Voyager 2)



First detection of the heliopause


First encounter with a main-belt asteroid
(Galileo to Gaspra)


First detection of α moon of an asteroid
(Galileo to Ida)