Cosmos

“Finally, at the end of all our wanderings, we return to out tiny, fragile, blue-white world, lost in a cosmic ocean vast beyond our most courageous imaginings.”

The author frames the book as a metaphorical cosmic voyage, headed out into the universe before returning to Earth. The Earth is contrasted with the vast distances and mysteries of the larger cosmos. In this way, both the planet humanity calls home and its place in the universe are illuminated and understood in new ways.

“But, as Darwin and Wallace showed, there is another way equally appealing, equally human, and far more compelling: natural selection, which makes the music of life more beautiful as the aeons pass.”

The author respects the religions and cultures of Earth, as the opening quotations of all of the chapters show. However, he also emphasizes the importance of science as a way of understanding the world and the cosmos. Here, he suggests that evolution not only explains how life comes about and adapts on Earth, but also gives us a way to grasp the fundamental poetry of such life. The “music of life” is played to the harmony of the cosmos, in his metaphor.

“And at the very heart of life on Earth—the proteins that control cell chemistry, and the nucleic acids that carry the hereditary instructions—we find these molecules to be essentially identical in all the plants and animals. An oak tree and I are made of the same stuff.”

Another argument that threads through the book is that of interconnection. Humanity connected to other lives on Earth, whether animal or plant, and to the lives of the stars. The cosmos encapsulates all.

“Kepler understood many things by the word harmony: the order and beauty of planetary motion, the existence of mathematical laws explaining that motion—an idea that goes back to Pythagoras—and even harmony in the musical sense, the ‘harmony of the spheres.’”

Johannes Kepler was responsible for many scientific ideas about the universe (see: Key Figures), but he was also a deeply religious person. Thus, he wanted to see how the motions of the cosmos relate to Christian descriptions of the world and its creation. Though Kepler eventually rejected his ideas about the “harmony of the spheres,” Sagan attempts to demonstrate the possibility of harmony between religious or cultural ideas and science.

“So the idea arose that comets were harbingers of disaster, auguries of divine wrath—that they foretold the death of princes, the fall of kingdoms.”

The author, while sympathetic to cultural beliefs, is less so to superstition. Astrology and astronomy have little in common: One is based on experimentation and careful observation, while the other is pseudo-science that rejects evidence. Still, the idea of the human imagination—even when it steers wrong—captures the author’s attention. He discusses many of the ways in which human societies throughout history have described phenomena that they did not understand scientifically.

“Science is generated by and devoted to free inquiry: the idea that any hypothesis, no matter how strange, deserves to be considered on its merits.”

The author critiques the notion that science should be inhibited by cultural beliefs. While the two can co-exist, it is crucial, at least for the scientific endeavor that the author advocates, for science to be independent in its thinking and hypothesizing. The author is also acknowledging that many hypotheses turn out to be incorrect upon further examination, though all scientific ideas deserve equal consideration.

“I remember being transfixed by the first lander image to show the horizon of Mars. This was not an alien world, I thought [...] One way or another, I knew, this was a world to which we would return.”

The author is prescient here: He notes that humankind has been fascinated with Mars for centuries. This has not changed since the publication of the book. Not only did the author oversee the launch of the first Viking probes to land successfully on the surface of Mars, but he also predicted that humanity would want to return—which has happened several times. NASA is currently planning for a manned expedition to the planet.

“There are so many examples of human misuse of the Earth that even phrasing this question chills me.”

The author poses the question of what humanity might do with Mars, should it ever get there. He is depending on human history to determine what the human future might look like. In an era of worries about climate change, social justice, and conservation, the author acknowledges that humanity’s abuses of its own planet should not carry over to another.

“These voyages of exploration and discovery are the latest in a long series that have characterized and distinguished human history.”

One of the themes of Cosmos is that exploration and discovery have long lived in the human imagination. The reasons behind these forays are not always savory—colonialism and greed often factor in—but humankind has always been hungry for knowledge of worlds beyond their own. In this way, humanity’s past is always inextricably linked to its future.

“But the Voyager spacecraft will plunge on, penetrating the heliopause sometime in the middle of the twenty-first century, skimming the ocean of space, never to enter another solar system, destined to wander through eternity far from the stellar islands and to complete its first circumnavigation of the massive center of the Milky Way a few hundred million years from now.”

The Voyager missions encapsulate the desire of humanity, and of the author in particular, to reach out and communicate with worlds beyond the Earth. In this passage, the author personifies the spacecraft as it wanders the vast reaches of space.

“They call it ‘the backbone of the night,’ as if the sky were some great beast inside which we live.”

The evocative metaphor of the Indigenous peoples of the Kalahari Desert points out the inextricable place of humanity in the larger cosmos. Humans cannot help but project themselves—their bodies, their imaginations—into the constellations of stars in the night sky. The idiom also emphasizes Sagan’s point about the unbreakable relationship between the cosmos and the Earth.

“Atoms were the ultimate particles, forever frustrating our attempts to break them into smaller pieces. Everything, he [Democritus] said, is a collection of atoms, intricately assembled. Even we.”

The early Greek philosopher and astronomer Democritus coined the term atom, which are now known to be foundational building blocks of inanimate and animate matter. Quantum physics has discovered that the parts of the atom—neutrons, protons, and electrons—are also linked in inextricable ways.

“The themes of space and time are, as we have seen, intertwined. Worlds and stars, like people, are born, live and die.”

The author connects the life cycle of stars to that of the living beings on Earth. If humanity is the stuff of stars, then it stands to reason that these cycles should be similar. He uses a simile to directly connect interstellar bodies to human ones; in the following chapter, the author explicitly expresses his belief in stars as a metaphor for life.

“What we do with our world in this time will propagate down through the centuries and powerfully determine the destiny of our descendants and their fate, if any, among the stars.”

Not only does the author link the lives of stars to the lives of people, but he also directly connects the past to the future. Humanity’s desire to discover new worlds and to travel to distant places has been constant throughout the history of human existence, from the earliest known humans to the colonial travels of the 15th century to the present need to explore beyond the Earth.

“A star is a phoenix, destined to rise for a time from its own ashes.”

This metaphor links the myth of the phoenix—that fabled bird that burns to ash then rises again—to the lives of the stars. Stars will live long lives before burning up their fuel and then failing. Sol, the sun around which the Earth rotates will eventually become a red giant before collapsing in on itself. Its fuel will fluctuate and then fade, ending life on Earth as it is known.

“And yet the Sun is an ordinary, even a mediocre star. If we must worship a power greater than ourselves, does it not make sense to revere the Sun and stars?”

The author puts the Earth’s position in perspective: There is nothing necessarily special about the star around which it rotates—even the planet might simply be lucky, not preordained. However, he still notes that the human desire to look up to things greater than themselves is constant. Almost all cultures have revered the sun in some form.

“The epic of cosmic evolution had begun, a hierarchy in the condensation of matter from the gas of the Big Bang—clusters of galaxies, galaxies, stars, planets, and, eventually, life and an intelligence able to understand a little of the elegant process responsible for its origin.”

Again, the processes of history are hard at work in the formation of the cosmos—and of humanity’s understanding of it. The author takes a very long view of history. The Big Bang ostensibly occurred billions and billions of years ago, yet the consequences of that event resonate throughout the galaxy yet today.

“There is an idea—strange, haunting, evocative—one of the most exquisite conjectures in science or religion. It is entirely undemonstrated; it may never be proved. But it stirs the blood. There is, we are told, an infinite hierarchy of universes, so that an elementary particle, such as an electron, in our universe would, if penetrated, reveal itself to be an entire closed universe.”

This inspires a number of science fictional conceits, from the multiverse to the idea that the universe in which humanity now lives is a simulation. Quantum physics has conjectured that electrons communicate over long distances; thus, the idea that an electron, in itself, contains an entire universe is plausible, given such a scenario. The author is describing the strange and unnerving possibilities for how life might exist out in the cosmos.

“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, proof that humans can work magic.”

Sagan firmly believes that humanity is a unique species with unique properties—characteristics that allow humans to explore and understand the greater universe. That is, the cosmos is not the author’s only subject. He is also deeply invested in understanding how Earth, and the peoples who live on it, work and learn.

“It is not yet clear that we have the wisdom to avoid our own self-destruction. But many of us are trying very hard. We hope that very soon in the perspective of cosmic time we will have unified our planet peacefully into an organization cherishing the life of every living creature on it and will be ready to take that next great step, to become part of a galactic society of communicating civilizations.”

This is one of the author’s primary messages in the book: Humanity must learn how to be a united advanced civilization—not merely technologically—to join a possible galactic community. This means that geopolitical relationships on Earth, not to mention conservations efforts, will be instrumental in future endeavors into the Cosmos.

“An interstellar message, intended to be understood by emerging civilizations, should be easy to decode.”

The author suggests that the language by which these messages can be understood is most likely mathematical. At the same time, the Voyager spacecraft launched out to the furthest planets and beyond contain a wealth of cultural information about the human species. From a plethora of languages to popular music, these spacecraft are attempting to transmit the best of human culture.

“If the doleful experience of cultural conflict on Earth were the galactic standard, it seems we would already have been destroyed, perhaps with some passing admiration expressed for Shakespeare, Bach and Vermeer. But this has not happened.”

The author is optimistic about the possibility that other, perhaps even more advanced, civilizations have not destroyed themselves via the same kind of technology that has been developed here on Earth. While his observations undeniably display a Western, Eurocentric bias, they are designed to encourage the continued search for life beyond the confines of Earth.

“If the inclinations toward slavery and racism, misogyny and violence are connected—as individual character and human history, as well as cross-cultural studies, suggest—then there is room for some optimism. We are surrounded by recent fundamental changes in society.”

Again, the author is essentially optimistic about the fate of humanity and its future out in the cosmos. He is also noting that the flaws that are endemic to one society on Earth are common to all. It is up to the reader to decide if the author’s optimism, circa 1980, has been borne out.