by Carl Sagan

Troy Shu
Troy Shu
Updated at: February 23, 2024

What are the big ideas? 1. The Ancient Greek Perspective on Science and Cosmos: This book highlights the significant contributions of ancient Greek scholars to vari

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What are the big ideas?

  1. The Ancient Greek Perspective on Science and Cosmos: This book highlights the significant contributions of ancient Greek scholars to various fields, including astronomy, mathematics, and physics. It emphasizes that our ancestors saw the world as interconnected with cosmic events, even in mundane things like toothache treatments. This unique perspective sheds light on the historical roots of scientific thinking and the importance of understanding our cosmic connection.
  2. The Search for Extraterrestrial Life: The book discusses how the search for life elsewhere in the universe expands our understanding of biological possibilities within the laws of physics and chemistry. It also emphasizes that even simple extraterrestrial organisms would deprovincialize biology by showing us what other kinds of life are possible.
  3. The Multiverse Hypothesis: The book introduces the concept of an infinite hierarchy of universes, suggesting that our universe may not be unique and could be part of a larger multiverse. This philosophical perspective challenges the traditional view of a single, static universe and raises questions about the nature of reality.
  4. Persistence of Recorded Information: The book discusses how recorded information, such as Voyager's gold-plated copper phonograph record, may outlast human civilization and be interpreted by advanced civilizations as indicators of our intelligence and civilization. This perspective highlights the importance of preserving our cultural heritage through various mediums for future generations and potential extraterrestrial beings.
  5. The Integration of Separate Individuals: The book discusses how radio communication is beginning to integrate separate individuals on Earth, and the possibility of similar communication with extraterrestrial civilizations in the future. This perspective emphasizes the importance of unity and interconnectedness, both within our civilization and potentially with other intelligent beings in the universe.

Chapter Summaries



  • Our universe is vast and ancient, and human affairs seem insignificant compared to its mysteries.
  • We are deeply connected to the cosmos; understanding it brings pleasure and survival benefits.
  • Our ancestors saw the world as interconnected with cosmic events, even in mundane things like toothache treatments.
  • Science is a powerful and elegant way to understand the universe, revealing its grandeur and our connection to it.
  • The public has a great interest in science and its discoveries, which can be excited through engaging and accessible communication.
  • The exploration of Mars in 1976 showed the potential for enormous global interest in scientific topics.
  • A thirteen-part television series called Cosmos was produced to communicate science in an engaging way.
  • Books and television have different approaches, with books allowing deeper exploration of topics.
  • Science is an ongoing process, with new discoveries constantly emerging.
  • Recent discoveries include Titan's atmosphere and ocean, rings around young stars, life on Earth's ocean floor, and comets in the solar system.
  • Future space missions to Halley's Comet, Mars, other comets, asteroids, and Titan are planned.
  • The pace of scientific discovery brings both wonder and concerns, such as potential nuclear war consequences.

I: The Shores of the Cosmic Ocean


  • Alexandria, founded around 300 B.C., was a center of learning and scholarship during the Hellenistic period.
  • Eratosthenes made an important geographical discovery by measuring the angle of the shadow cast by a vertical stick at two different locations on Earth. He used this observation to estimate the circumference of the Earth and determine its spherical shape.
  • The Alexandrian Library was a research institute dedicated to studying various disciplines, including mathematics, astronomy, geography, philosophy, and medicine. It contained half a million scrolls and was a center for intellectual pursuits during the Hellenistic period.
  • The scholars of Alexandria made significant contributions to various fields, such as Euclid in geometry, Archimedes in mechanics, and Ptolemy in astronomy.
  • However, the library and its knowledge were largely lost when the city was conquered and the institution was destroyed.
  • The intellectual achievements of ancient Greece and Alexandria laid the foundation for scientific and scholarly pursuits that continue to this day.


“The Cosmos is all that is or was or ever will be. Our feeblest contemplations of the Cosmos stir us -- there is a tingling in the spine, a catch in the voice, a faint sensation, as if a distant memory, of falling from a height. We know we are approaching the greatest of mysteries.”

“The size and age of the Cosmos are beyond ordinary human understanding. Lost somewhere between immensity and eternity is our tiny planetary home. In a cosmic perspective, most human concerns seem insignificant, even petty. And yet our species is young and curious and brave and shows much promise. In the last few millennia we have made the most astonishing and unexpected discoveries about the Cosmos and our place within it, explorations that are exhilarating to consider. They remind us that humans have evolved to wonder, that understanding is a joy, that knowledge is prerequisite to survival. I believe our future depends on how well we know this Cosmos in which we float like a mote of dust in the morning sky.”

“The surface of the Earth is the shore of the cosmic ocean. On this shore, we've learned most of what we know. Recently, we've waded a little way out, maybe ankle-deep, and the water seems inviting. Some part of our being knows this is where we came from. We long to return, and we can, because the cosmos is also within us. We're made of star stuff. We are a way for the cosmos to know itself.”

“A galaxy is composed of gas and dust and stars - billions upon billions of stars. Every star may be a sun to someone.”

“Cosmos is a Greek word for the order of the universe. It is, in a way, the opposite of Chaos. It implies the deep interconnectedness of all things. It conveys awe for the intricate and subtle way in which the universe is put together.”

II: One Voice in the Cosmic Fugue


  • The origins of life on Earth remain a mystery, but laboratory experiments have shown that simple organic molecules can be synthesized under primitive conditions.
  • Life likely began as simple, nonparasitic organisms, possibly resembling free-living viroids or small, self-replicating RNA molecules.
  • The diversity of life on Earth suggests that extraterrestrial beings may be vastly different from anything we can imagine, defying our expectations based on familiar terrestrial organisms.
  • The study of extraterrestrial life, even if it is simple and humble, would deprovincialize biology by showing us what other kinds of life are possible.
  • The search for life elsewhere in the universe is important because it expands our understanding of the biological possibilities within the laws of physics and chemistry.
  • The idea that life might exist elsewhere in the universe has a long history, with many cultures and scientists proposing various hypotheses throughout history.


“You are worth about 3 dollars worth in chemicals.”

“The fossil record implies trial and error, the inability to anticipate the future, features inconsistent with a Great Designer (though not a Designer of a more remote and indirect temperament.)”

“We are like butterflies who flutter for a day and think it is forever.”

“And you are made of a hundred trillion cells. We are, each of us, a multitude.”

“What a marvelous cooperative arrangement - plants and animals each inhaling each other's exhalations, a kind of planet-wide mutual mouth-to-stoma resuscitation, the entire elegant cycle powered by a star 150 million kilometers away.”

“There’s as many atoms in a single molecule of your DNA as there are stars in the typical galaxy. We are, each of us, a little universe.”

“We humans look rather different from a tree. Without a doubt we perceive the world differently than a tree does. But down deep, at the molecular heart of life, the trees and we are essentially identical.”

III: The Harmony of Worlds


  • Johannes Kepler was a German mathematician and astronomer who is best known for his laws of planetary motion. He grew up in a poor family and was largely self-educated.
  • Kepler's first major discovery was the elliptical shape of planetary orbits around the Sun. This contradicted the circular orbits proposed by Ptolemy.
  • Kepler's second law states that a planet moves faster when it is closer to the Sun and slower when it is farther away. This is due to the varying distance between the planet and the Sun, which affects the gravitational force.
  • Kepler's third law states that the square of the orbital period of a planet is proportional to the cube of its average distance from the Sun.
  • Isaac Newton was an English mathematician and physicist who built upon Kepler's work to develop the theory of universal gravitation. He discovered the inverse-square law of gravity, which states that the force of gravity between two masses decreases as the square of the distance between them increases.
  • Newton also developed calculus, which allowed him to solve complex mathematical problems related to physics and astronomy. He used calculus to derive Kepler's laws from his theory of gravitation.
  • Kepler and Newton were important figures in the Scientific Revolution, a period of intellectual growth that saw a shift towards empirical and rational ways of understanding the natural world. Their discoveries laid the foundation for modern physics and astronomy.


“The reappearance of the crescent moon after the new moon; the return of the Sun after a total eclipse, the rising of the Sun in the morning after its troublesome absence at night were noted by people around the world; these phenomena spoke to our ancestors of the possibility of surviving death. Up there in the skies was also a metaphor of immortality.”

“The absence of evidence is not the evidence of absence.”

“In the vastness of space and the immensity of time, it is my joy to share a planet and an epoch with Annie.

[Dedication to Sagan's wife, Ann Druyan, in Cosmos]”

IV: Heaven and Hell


  • Venus is a planet with extreme conditions, including a thick toxic atmosphere, surface temperatures hot enough to melt lead, and crushing pressures.
  • The similarities between Earth and Venus suggest that Venus may have had liquid water on its surface in the past, but something caused it to lose this water and become the inhospitable planet it is today.
  • Scientists believe that Venus underwent a runaway greenhouse effect, causing its surface temperature to rise and its water to evaporate, leading to the current conditions.
  • Earth's climate is also changing due to human activities, including deforestation, industrial pollution, and burning fossil fuels, which release large amounts of carbon dioxide into the atmosphere and contribute to the greenhouse effect.
  • The long-term consequences of these changes are not fully understood and could potentially lead to catastrophic consequences for Earth's climate, such as a runaway greenhouse effect or a global ice age.
  • It is important for humans to be aware of the potential risks and take steps to mitigate them, such as reducing our carbon footprint and protecting natural habitats.


“Science needs the light of free expression to flourish. It depends on the fearless questioning of authority, and the open exchange of ideas.”

“If we ruin the earth, there is no place else to go”

“There are many hypotheses in science which are wrong. That’s perfectly all right: it’s the aperture to finding out what’s right. Science is a self-correcting process.”

“Observation: I can't see a thing. Conclusion: Dinosaurs.”

V: Blues for a Red Planet


  • Mars has intriguing geological features and may have had liquid water in its past.
  • The Viking missions in the late 1970s did not detect life on Mars, but they provided valuable data on Martian geology, meteorology, and mineralogy.
  • Future missions to Mars could include a roving vehicle with advanced experiments or a sample return mission, both of which would provide new insights and discoveries.
  • Terraforming Mars, or making it habitable for human beings, is a long-term concept that involves increasing the atmospheric pressure, making liquid water possible, and shielding the surface from solar ultraviolet radiation.
  • This could be achieved by releasing ancient Martian gases trapped in the polar ice caps using dark plants or other methods.
  • Mars might become habitable for humans in hundreds to thousands of years through advanced technology and terraforming efforts.


“I am a collection of water, calcium and organic molecules called Carl Sagan. You are a collection of almost identical molecules with a different collective label. But is that all? Is there nothing in here but molecules? Some people find this idea somehow demeaning to human dignity. For myself, I find it elevating that our universe permits the evolution of molecular machines as intricate and subtle as we.

But the essence of life is not so much the atoms and simple molecules that make us up as the way in which they are put together. Every now and then we read that the chemicals which constitute the human body cost ninety-seven cents or ten dollars or some such figure; it is a little depressing to find our bodies valued so little. However, these estimates are for human beings reduced to our simplest possible components. We are made mostly of water, which costs almost nothing; the carbon is costed in the form of coal; the calcium in our bones as chalk; the nitrogen in our proteins as air (cheap also); the iron in our blood as rusty nails. If we did not know better, we might be tempted to take all the atoms that make us up, mix them together in a big container and stir. We can do this as much as we want. But in the end all we have is a tedious mixture of atoms. How could we have expected anything else?”

VI: Travelers’ Tales


  • Jupiter and Saturn are gas giants in our solar system, with similar sizes but distinct characteristics.
  • Jupiter has a prominent equatorial banding and a strong magnetic field, while Saturn displays less obvious banding and a weaker magnetic field.
  • Both planets have complex ring systems and numerous moons, some of which may harbor the possibility of life due to their unique environments.
  • The rings of Saturn are composed of small ice particles that cannot stick together due to their relative speeds in orbit around the planet.
  • The solar wind, a stream of charged particles from the Sun, interacts with the magnetic fields of planets like Jupiter and Saturn, creating radiation belts.
  • Titan, Saturn's largest moon, has an atmosphere primarily composed of nitrogen and methane, raising the possibility of life existing there.
  • The exploration of Jupiter and Saturn, as well as other planets in our solar system, continues to revolutionize our understanding of these celestial bodies and their potential habitats.

VII: The Backbone of Night


  • Ancient Greek philosophers like Thales, Anaximander, and Pythagoras made significant contributions to natural philosophy and cosmology by proposing theories about the nature of the universe and its origins.
  • The Greeks believed in a geocentric model of the universe with Earth at the center and all other celestial bodies orbiting around it.
  • Aristarchus of Samos challenged this belief with his heliocentric theory, suggesting that the Sun was at the center of the universe and the Earth revolved around it. However, his ideas were not widely accepted during his time.
  • The development of mathematical tools like geometry and algebra allowed scientists to make more precise observations and calculations about the universe.
  • Ptolemy's synthesis of earlier Greek theories resulted in the widely-accepted geocentric model of the universe, which remained dominant until the Renaissance.
  • Copernicus proposed a heliocentric model of the universe in the 16th century, but it took time for his ideas to be accepted due to religious and societal opposition.
  • The discovery of the laws of motion and universal gravitation by Galileo and Newton led to a better understanding of the physical properties of the universe and paved the way for the scientific revolution.
  • The development of telescopes allowed scientists to observe celestial bodies in greater detail, leading to new discoveries about the universe's structure and composition.
  • Modern cosmology seeks to understand the origins and evolution of the universe as a whole, utilizing theories like the Big Bang and the expanding universe.


“The beauty of a living thing is not the atoms that go into it, but the way those atoms are put together.”

“If we long for our planet to be important, there is something we can do about it. We make our world significant by the courage of our questions and by the depth of our answers.”

“Exploration is in our nature. We began as wanderers, and we are wanderers still. We have lingered long enough on the shores of the cosmic ocean. We are ready at last to set sail for the stars.”

VIII: Travels in Space and Time


  • The study of astronomy has played a significant role in shaping human civilization and scientific understanding.
  • Early civilizations made observations of celestial bodies, creating calendars and mythologies based on their movements.
  • Greek philosophers like Thales, Anaxagoras, and Aristarchus made important contributions to the fields of astronomy and physics.
  • The invention of the telescope in the late 16th century led to significant advancements in astronomical knowledge.
  • Galileo's observations of Jupiter's moons and the phases of Venus provided evidence for the Copernican heliocentric model.
  • Johannes Kepler's laws of planetary motion paved the way for Newton's theory of gravity.
  • The study of astronomy continues to advance with the discovery of new planets, moons, and celestial bodies through telescopic observations and space exploration.
  • The concept of dark matter and dark energy has expanded our understanding of the universe and its composition.
  • Space travel and time travel are connected concepts in physics, as traveling fast into space requires traveling fast into the future.
  • The possibility of time travel raises questions about altering historical events and the existence of alternate realities.
  • The exploration of other planetary systems in the future is an exciting prospect for humanity, with potential discoveries and implications for our understanding of the universe.


“We are star stuff which has taken its destiny into its own hands.”

“The lifetime of a human being is measured by decades, the lifetime of the Sun is a hundred million times longer. Compared to a star, we are like mayflies, fleeting ephemeral creatures who live out their lives in the course of a single day.”

“Compared to a star, we are like mayflies, fleeting ephemeral creatures who live out their whole lives in the course of a single day. From the point of view of a mayfly, human beings are stolid, boring, almost entirely immovable, offering hardly a hint that they ever do anything. From the point of view of a star, a human being is a tiny flash, one of billions of brief lives flickering tenuously on the surface of a strangely cold, anomalously solid, exotically remote sphere of silicate and iron.”

IX: The Lives of the Stars


  • The universe is vast and mostly empty, containing around 100-200 billion galaxies, each with hundreds of billions of stars.
  • Stars are giant balls of hot gas that produce light through nuclear reactions, primarily the fusion of hydrogen into helium.
  • Our Sun is a typical star, middle-aged and stable, with nine planets orbiting around it in various distances and eccentricities.
  • Planets are celestial bodies orbiting a star, usually composed of rock or gas. They can have moons, which are also celestial bodies orbiting the planet.
  • The Solar System is located in the Milky Way Galaxy, a barred spiral galaxy with around 100-400 billion stars and various other celestial objects.
  • Stars go through different stages of their life cycle, starting as nebulae and ending as white dwarfs or black holes.
  • Black holes are the remnants of massive stars that have collapsed under their own gravity, creating regions with extremely strong gravitational forces from which nothing can escape.
  • Gravity is a fundamental force in the universe that attracts all matter towards each other, causing various celestial phenomena such as orbits and tides.
  • The study of the universe and its celestial bodies is called astronomy, with important contributions coming from various cultures throughout history.


“If you wish to make an apple pie from scratch, you must first invent the universe.”

“Atoms are mainly empty space. Matter is composed chiefly of nothing.”

“When we look up at night and view the stars, everything we see is shinning because of distant nuclear fusion.”

“The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of starstuff.”

“A still more glorious dawn awaits Not a sunrise, but a galaxy rise A morning filled with 400 billion suns The rising of the milky way”

X: The Edge of Forever


  • The universe may be a four-dimensional hypersphere with no center or edge, and nothing beyond it.
  • If the universe is closed, light is trapped within it, making it finite but unbounded.
  • Expansion of the universe suggests that it is either open or closed.
  • Wormholes, if they exist, could potentially connect our universe to others or provide a means to travel through space-time.
  • There may be an infinite hierarchy of universes, with each elementary particle being a complete universe at a smaller scale. This idea is called the "multiverse" hypothesis.
  • The laws of nature in our universe may not be randomly reshuffled at the cusps of the oscillating universe, suggesting that there are rules governing which laws are permissible and which are not. This could imply a new physics, or "transphysics," standing over the existing one.


“The study of the galaxies reveals a universal order and beauty. It also shows us chaotic violence on a scale hitherto undreamed of. That we live in a universe which permits life is remarkable. That we live in one which destroys galaxies and stars and worlds is also remarkable. The universe seems neither benign nor hostile, merely indifferent to the concerns of such puny creatures as we.”

“The Hindu religion is the only one of the world’s great faiths dedicated to the idea that the Cosmos itself undergoes an immense, indeed an infinite, number of deaths and rebirths. It is the only religion in which the time scales correspond to those of modern scientific cosmology. Its cycles run from our ordinary day and night to a day and night of Brahma, 8.64 billion years long. Longer than the age of the Earth or the Sun and about half the time since the Big Bang.”

“It is said that men may not be the dreams of the god, but rather that the gods are the dreams of men.”

“By looking far out into space we are also looking far back into time, back toward the horizon of the universe, back toward the epoch of the Big Bang.”

“The total amount of energy from outside the solar system ever received by all the radio telescopes on the planet Earth is less than the energy of a single snowflake striking the ground.”

XI: The Persistence of Memory


  • The total amount of information available in books is less than that contained in a single hour of television broadcast in a large American city.
  • Human brains and genes store information differently, with genes being much older and books much more recent.
  • The Voyager spacecraft carries a gold-plated copper phonograph record with instructions for use and sounds from Earth, including human emotions and music.
  • Television signals travel faster than Voyager and will reach nearby stars in a few years, while Voyager will take tens of thousands of years to reach them.
  • The persistence of human memory is longer through the recorded information on the Voyager record than through our monuments or books.
  • Our radio transmissions, especially television broadcasts, may be interpreted by advanced civilizations as indicators of our intelligence and civilization.
  • The preferred interstellar communication channel for technical civilizations is near a hydrogen spectral line, but terrestrial radio technology is encroaching on this frequency band and risking the inability to communicate with extraterrestrial beings.
  • The ancient Greek word for "to count" literally means "to five."
  • A recent analysis suggests that 96% of all marine species may have died during the late Mesozoic extinction event, making today's organisms a small and unrepresentative sample of those that lived then.
  • The integration of separate individuals through radio communication is beginning on Earth.


“Knowing a great deal is not the same as being smart; intelligence is not information alone but also judgement, the manner in which information is coordinated and used.”

“The brain does much more than recollect. It compares, synthesizes, analyzes, generates abstractions. We must figure out much more than our genes can know. That is why the brain library is some ten thousand times larger than the gene library. Our passion for learning, evident in the behaviour of every toddler, is the tool for our survival. Emotions and ritualized behaviour patterns are built deeply into us. They are part of our humanity. But they are not characteristically human. Many other animals have feelings. What distinguishes our species is thought. The cerebral cortex is a liberation. We need no longer be trapped in the genetically inherited behaviour patterns of lizards and baboons. We are, each of us, largerly responsible for what gets put into our brains, for what, as adults, we wind up caring for and knowing about. No longer at the mercy of the reptile brain, we can change ourselves.”

“What an astonishing thing a book is. It's a flat object made from a tree with flexible parts on which are imprinted lots of funny dark squiggles. But one glance at it and you're inside the mind of another person, maybe somebody dead for thousands of years. Across the millennia, an author is speaking clearly and silently inside your head, directly to you. Writing is perhaps the greatest of human inventions, binding together people who never knew each other, citizens of distant epochs. Books break the shackles of time. A book is proof that humans are capable of working magic."

[Cosmos, Part 11: The Persistence of Memory (1980)]”

“One glance at (a book) and you hear the voice of another person - perhaps someone dead for thousands of years. Across the millenia, the author is speaking, clearly and silently, inside your head, directly to you. Writing is perhaps the greatest of human inventions, binding together people, citizens of distant epochs, who never knew one another. Books break the shackles of time.”

“Books break the shackles of time, proof that humans can work magic.”

“More recently, books, especially paperbacks, have been printed in massive and inexpensive editions. For the price of a modest meal you can ponder the decline and fall of the Roman Empire, the origin of species, the interpretation of dreams, the nature of things. Books are like seeds. They can lie dormant for centuries and then flower in the most unpromising soil.”

“If I finish a book a week, I will read only a few thousand books in my lifetime, about a tenth of a percent of the contents of the greatest libraries of our time. The trick is to know which books to read.”

“Books permit us to voyage through time, to tap the wisdom of our ancestors. The library connects us with the insight and knowledge, painfully extracted from Nature, of the greatest minds that ever were, with the best teachers, drawn from the entire planet and from all our history, to instruct us without tiring, and to inspire us to make our own contribution to the collective knowledge of the human species. I think the health of our civilization, the depth of our awareness about the underpinnings of our culture and our concern for the future can all be tested by how well we support our libraries.”

XII: Encyclopaedia Galactica


  • The Drake Equation, introduced by Frank Drake in 1961, attempts to estimate the number of extraterrestrial civilizations that might be able to communicate with Earth.
  • The equation includes factors such as the rate of star formation, the fraction of those stars that have planets, the number of planets that could support life, and the likelihood of a planet developing intelligent life, among others.
  • The equation is not meant to provide definitive answers, but rather to stimulate thinking and discussion about the possibilities of extraterrestrial civilizations.
  • Carl Sagan and I raid the Encyclopaedia Galactica to generate fictional examples of two hypothetical extraterrestrial civilizations with different levels of development.
  • The first civilization, 1.8 L, is a pre-technological society that has only recently begun to make contact with other civilizations in the galaxy. It has a polyaromatic sulfonylhalide biology and a polytaxic, monochromatic society.
  • The second civilization, 2.3 R, is an advanced interstellar civilization that utilizes supergiants, white dwarfs, and pulsars as energy sources. It has a metal-chelated organic semiconductor biology and a polytaxic, global society.
  • The Encyclopaedia Galactica serves as a thought experiment for considering the potential diversity of extraterrestrial civilizations and the challenges and opportunities that might come with contacting them.

XIII: Who Speaks for Earth?


  • The universe is approximately 15 billion years old and continues to expand
  • Stars, including the Sun, are formed from interstellar gas and dust
  • The solar system consists of eight planets and various other celestial bodies, including asteroids and comets
  • Earth is a terrestrial planet with a diverse range of ecosystems, including forests, deserts, grasslands, and oceans
  • Life on Earth began as simple organic compounds and evolved into complex organisms through a process called evolution by natural selection
  • Humans are the latest stage in the evolution of life on Earth and possess unique qualities such as self-awareness and advanced technology
  • The study of the universe beyond Earth is called astronomy, and our understanding of it has increased significantly in recent centuries due to advances in technology and scientific discovery
  • Space exploration has been a significant part of human history since the late 20th century, with many unmanned missions to the planets and moons of our solar system and plans for manned missions to Mars and beyond.


“We are made of stellar ash. Our origin and evolution have been tied to distant cosmic events. The exploration of the cosmos is a voyage of self-discovery.”

“National boundaries are not evident when we view the Earth from space. Fanatical ethnic or religious or national chauvinisms are a little difficult to maintain when we see our planet as a fragile blue crescent fading to become an inconspicuous point of light against the bastion and citadel of the stars.”

“Every thinking person fears nuclear war, and every technological state plans for it. Everyone knows it is madness, and every nation has an excuse”

“We inhabit a universe where atoms are made in the centers of stars; where each second a thousand suns are born; where life is sparked by sunlight and lightning in the airs and waters of youthful planets; where the raw material for biological evolution is sometimes made by the explosion of a star halfway across the Milky Way; where a thing as beautiful as a galaxy is formed a hundred billion times - a Cosmos of quasars and quarks, snowflakes and fireflies, where there may be black holes and other universe and extraterrestrial civilizations whose radio messages are at this moment reaching the Earth. How pallid by comparison are the pretensions of superstition and pseudoscience; how important it is for us to pursue and understand science, that characteristically human endeavor. ”

“Every aspect of Nature reveals a deep mystery and touches our sense of wonder and awe. Those afraid of the universe as it really is, those who pretend to nonexistent knowledge and envision a Cosmos centered on human beings will prefer the fleeting comforts of superstition. They avoid rather than confront the world. But those with the courage to explore the weave and structure of the Cosmos, even where it differs profoundly from their wishes and prejudices, will penetrate its deepest mysteries.”

“Every one of us is, in the cosmic perspective, precious. If a human disagrees with you, let him live. In a hundred billion galaxies, you will not find another.”

“Human history can be viewed as a slowly dawning awareness that we are members of a larger group. Initially our loyalties were to ourselves and our immediate family, next, to bands of wandering hunter-gatherers, then to tribes, small settlements, city-states, nations. We have broadened the circle of those we love. We have now organized what are modestly described as super-powers, which include groups of people from divergent ethnic and cultural backgrounds working in some sense together — surely a humanizing and character building experience. If we are to survive, our loyalties must be broadened further, to include the whole human community, the entire planet Earth. Many of those who run the nations will find this idea unpleasant. They will fear the loss of power. We will hear much about treason and disloyalty. Rich nation-states will have to share their wealth with poor ones. But the choice, as H. G. Wells once said in a different context, is clearly the universe or nothing.”

“We are the local embodiment of a Cosmos grown to self-awareness. We have begun to contemplate our origins: starstuff pondering the stars; organized assemblages of ten billion billion billion atoms considering the evolution of atoms; tracing the long journey by which, here at least, consciousness arose. Our loyalties are to the species and the planet. We speak for Earth. Our obligation to survive is owed not just to ourselves but also to that Cosmos, ancient and vast, from which we spring.”


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