Carl Sagan: Cosmos (1980)

Cosmos may fairly be called one of the foundational books of my life (even moreso than Sagan’s earlier The Cosmic Connection, revisited here in 2015) even though I hadn’t read the entire book until this year. The book was a companion to a 13-part PBS TV series than ran in late 1980. In 1980 I was living in a one-room apartment with a tiny, maybe 15-inch, black and white TV, so even though I watched the show at the time, I saw it only in black and white. Recently, inspired perhaps by the latest of the Neil deGrasse Tyson-hosted Cosmos TV series (largely written by Anne Druyan, Sagan’s wife and cowriter back in 1980) that launched earlier this year. I discovered that all the episodes of the original series could be found on YouTube—though alas, several of them interrupted by commercials. So I sprung for the entire series on DVD (i.e. I bought it) and over a period of some months, beginning this past June, have watched the series (now seeing it in color!) and finally reading the book closely. I’m sure I’d glanced through the book back in 1980 (I got it as a Christmas gift that year) or early 1981, but likely didn’t feel the need to read it thoroughly, given its similarity to the TV series.

The show ran originally from September 28 – December 21, 1980, per Wikipedia, and the book was released in October 1980. So they were obviously developed in parallel. Indeed, some of the footage in the TV series, of Sagan at JPL as Voyager 2 pictures came in from Jupiter, was filmed back in 1979.

The TV show was a prestigious, high-end production, and very popular. It followed at least three similar productions on PBS, Alastair Cooke’s Civilization (1970), J. Bronowski’s The Ascent of Man (1973), and James Burke’s Connections (1978) – all three multi-episode TV productions with parallel, lavishly illustrated books. (Cooke’s now is dated in its parochialism, being limited almost entirely to western European civilization.)

That a book about astronomy and cosmology should follow those, and become as popular than those, seemed to confirm to me the ascendance of real science into popular discourse. TV had had its pop sci-fi in Lost and Space and Star Trek, the movies its simplistic space opera of Star Wars, now here was PBS doling out the real thing about the history of science and our knowledge of the cosmos. To me it was a validation, of sorts, that ideas about humanity’s place in the vast universe were filtering down into public consciousness, perhaps brushing aside superstitious notions like astrology and general ignorance about the difference between planets, stars, and galaxies. Alas, decades later, this has not happened; ignorance about reality, and adherence to conspiracy theories, has only grown.

Of course I knew much about the subjects of Cosmos in general, my astronomy interest going back to 1965 or so (when I was 10). Yet Sagan made the subject personal, appearing on camera in segments alternating with graphics and animations, with historical recreations (using actors and local sets) of pivotal events in the history of science, and the notion of a “ship of the imagination,” a futuristic spaceship bridge, where Sagan would stand to allow the POV to sweep into the atmospheres of the planets or through distant galaxies.

The TV series did have one influence on me quite apart from the scientific content: the music. The show used electronic music by the Greek composer Vangelis, many tracks from numerous albums, which I then sought out. (Vangelis went on, in just the next couple years, to do original scores for movies like Chariots of Fire [for which he won as Oscar] and Blade Runner.) There were also tracks from classic music composers, in particular Shostakovich, whose 11th symphony, mostly the quiet sections of tense music, were used in several episodes. (I’d already heard some Shostakovich in the 1975 film Rollerball.)

As it turns out, the TV episodes and the book chapters of Cosmos are not precisely in synch, even though the titles are the same. The differences include…

  • Sagan indulges in segments about popular misconceptions, in the TV show, that are barely mentioned in the book. These include astrology, UFOs, and alien visitations.
  • Sagan’s notion of “cosmic calendar” ( — the notion that if the entire age of the universe were shrunk to the length of one Earth year, how events of the history would lie along it proportionally, e.g. that the last 12,000 years of human history would occupy only the last couple seconds of the cosmic year) is employed in the TV show, effectively (as Sagan walks around such a calendar projected onto the floor) — but it’s not mentioned in the book at all. That’s because Sagan had developed the idea in his earlier book The Dragons of Eden in 1977.
  • The TV series is quite ambitious in imagining, one or two per episode, historical scenes depicting scientific discoveries, complete with actors in period garb sometimes shot in actual locations. These are minimized in the book, summarized or even passed over in the book text.

Here are the most striking take-aways I had of the book and series:

  • The cosmic calendar remains a striking visualization of the vast history of the universe and the tiny sliver of our awareness of it.
  • The themes of destruction, of the biosphere, of the species, run through the book. The end of episode 4 could well be the inspiration for the documentary film Koyaanisqatsi.
  • Sagan is frank, in the series, about acknowledging and dismissing much pseudoscience, including astrology, alien visitations, and Velikovsky, and for that matter the religious presumption of a god as creator of the universe.
  • Sagan’s take on ancient philosophy is striking (in Chapter 7). He contrasts the early Ionians (e.g. Democritus, who first proposed the idea of atoms) with the later “mystics” (Plato and his followers) who set experiment and evidence aside, an attitude inherited by Christians, that lasted for 2000 years! That the heavens are perfect and so there simply can’t, for instance, be anything orbiting Jupiter. I’ve gone through summaries of philosophy and the history of science from time to time, but never seen this particular contrast spelled out like this.
  • The TV series was ambitious in its enactments of famous people in historical times and places. (The later Cosmos TV series of the past decade have used animations for such passages.)
  • Sagan himself is a striking character, with his odd emphasis on certain words (parodied in his citations of “billions and billions” of stars), and his obvious enthusiasm, even in the ecstatic look on his face as he is portrayed viewing the mysteries of the cosmos from his “ship of the imagination.” (Fittingly, Neil deGrasse Tyson in the recent Cosmos series has a similar enthusiasm, if a different style.)
  • And of course the key points are the cosmic perspective, the repeated emphasis on vast quantities of time and space, and how science, with its two rules (there are no sacred truths, and, whatever is inconsistent with the facts must be discarded or revised), is the only way understand reality. Not by tradition, revelation, or intuition.

So now I’ll summarize the subject  and main points of each chapter/episode, with some further comments about any key differences between the two. (Wikipedia’s page,, has three or four-line descriptions of each episode.)

1, “The Shores of the Cosmic Ocean”

  • “The cosmos is all that is or ever was or ever will be.” Sagan opens live on the coast of California, in Big Sur at Monterey, a rugged section of cliffs, pine trees, and crashing surf. (Which I’ve driven through several times.) “The cosmos is also within us; we’re made of starstuff. We are a way for the cosmos to know itself.” He discusses large dimensions, speculates on aliens, and plucks a dandelion, launching it into the air where it turns into his “spaceship of the imagination.”

2, “One Voice in the Cosmic Fugue”

  • Wondering about alien life is the same problem as understanding life on earth, and evolution. About human domestication of animals and plants. “Evolution is a fact, not a theory.” The Cosmic Calendar. “Part of the resistance to Darwin and Wallace derives from our difficulty in imagining the passage of the millennia, must less the aeons…”
  • There’s a remarkable animation depicting the evolution of life on Earth from single cells all the way to humans… in just a couple minutes (to music of Vangelis). “Those are some of things molecules do given four billion years of evolution.” This animation is used again in later episodes.

3, “Harmony of the Worlds”

  • Opening section shows Sagan live, in NYC, discusses the difference between astronomy and astrology. The evidence fails; modern astrology ignores all the astronomical phenomena discovered since Ptolemy. And how would it even work? (The book notes the many national flags that display stars of constellations or crescent moons.)
  • Yet we are connected to the cosmos, in the deepest ways. Cultures across time have studied the sky—perhaps merely to predict the seasons, to plan agriculture. They noticed the “planets” wandering across the sky; discovery of how they moved with prediction has led to our modern civilization, despite early belief in an immobile Earth, a notion supported by the Church throughout the Dark Ages, until Copernicus in 1543. After him, Kepler, with his notion about how God’s plan must entail the five perfect solids…but the evidence didn’t support it. He threw in with the wealthy Tycho, a brilliant observationalist, whose data led to Kepler’s three laws of planetary motion.
  • And then Newton, who hid his disbelief in the Trinity. He invents differential calculus, studies light, lays out a theory of gravitation. Kepler’s three laws became derived from Newton’s gravitation. Yet Newton pursued astrology, and alchemy; the distinction between science and pseudoscience had not yet been made.

4, “Heaven and Hell”

  • (The title here echoes the Vangelis album used for much of the music.)
  • Now the series moves on to considering other planets, and comets and meteors. 1908, the Siberian event, which Sagan concludes must have been a comet hitting the Earth, with effects like a nuclear bomb but without the radiation. About the history of comets; how superstitious beliefs become self-fulfilling prophecies. Comet pills dispensed in 1910!
  • Meteor craters; an explosion on the moon observed in 1178 at Canterbury Cathedral, giving lie to the notion that the heavens were unchangeable.
  • Discussion of Velikovsky [a popular writer in the 1950s with an outlandish theory that totally implausible planetary movements and collisions explained various events in the Bible]; Sagan makes the point that the worst aspect of his popularity was that some scientists wanted to actively suppress his books. Science is self-correcting, so his ideas would be eventually dismissed (as they were).
  • How the prism, the spectrum, the discovery of absorption lines, led to the detection of elements in other planets’ atmospheres [and later, of the composition of stars]. Venus: discovered to be very hot, like hell.
  • How erosion has worn down the Sphinx. Storms, volcanoes, fires, climatic catastrophes. Short-term profits over long-term habitability. If we destroy the planet, we have no place to go to. “If a visitor arrived from another world, what account would we give of our stewardship of the planet Earth?”
  • Sagan was worrying about global cooling back in 1980, but his larger point remains that the planetary environment is fragile and can easily be knocked out of kilter, one way or another.
  • ==> The episode ends with a remarkable sequence of mining explosions and demolitons; it’s like a premonition of the 1982 documentary film Koyaanisqatsi, famous for its early Philip Glass score, and its many scenes similar scenes of miners exploding mountains and natural landscapes ruined by development.
  • “Do we value short-term advantages above the welfare of the Earth? Or will we think on longer time scales, with concern for our children and our grandchildren, to understand and protect the complex life-support systems of our planet? The Earth is a tiny and fragile world. It needs to be cherished.”

5, “Blue for a Red Planet”

  • All about Mars. Holst, Wells, Lowell, Schiarprelli and his canals, his observatory in Flagstaff. The idea of an ancient race there mostly wish fulfillment.
  • The real road to Mars began with Goddard, his rockets, back in 1898. No canals. [As of 1980] We’ve sent robots, Viking 1 and 2. And much background about the planning of these missions, and their inconclusive results.

6, “Travellers’ Tales”

  • About exploration of the outer planets, with explicit comparison to the 17th and 18th century European voyages around the globe. The Enlightenment; Dutch East India, explorations for profit. Sagan visits the actual Amsterdam town hall, and discusses Galileo, Bruno, and in Holland Huygens; Leeuwenhoek invents the microscope to see “animalcules.” How primitive telescopes saw features on Mars, the rings of Saturn. The pendulum clock; how the understanding came that stars were other suns.
  • In the book: Christians argued that, since the entire heavens turned around the Earth once a day, they couldn’t be infinite…146.0) Some thought the plurality of worlds absurd; 146m. (But it was all baseless speculation, based on ideology, not evidence.)
  • Then we see 1979 scenes of Sagan at JPL seeing photos come in from Voyager 2 at Jupiter. (Technicians with lots of mustaches! And smoking!)
  • Some early travelers’ tales from their global travels were lies or exaggerations; yet they inspired Voltaire and Swift.

7, “The Backbone of Night”

  • About the Milky Way, easily visible in dark skies throughout human history.
  • The episode has Sagan visit his old digs in Brooklyn (driving a Chevrolet Citation). He recalls asking for books, at the library, about stars, and was given a book about movie stars. He explained. Later, Sagan visiting a 6th grade classroom and taking questions, illustrating the natural curiosity of the young.
  • How lucky we are to live at this time; in an earlier age we would not have understood all this, about stars, the milky way, gravity.
  • Contemporary hunter-gathering tribes call it the backbone of the night. Early observations gave rise to the idea of gods, one for every human concern, who all had to be propitiated through rituals and myths, temples and monuments.
  • Sagan visits the Greek islands, where about 2500 years ago there was a kind of awakening by the Ionians: the idea that the universe was knowable—that it’s ordered and regular, and predictable. ==> This is a key idea. Why did this idea develop at this time and place? Perhaps, Sagan suggests, because these islands had been newly colonized, unlike other places that were in the centers of old empires; and thus ready for new ideas.
  • But the Ionians were suppressed and ridiculed by later Greeks (Pythagoras, Plato, Aristotle) who thought knowledge about the world could be deduced from first principles, that experiments were undignified. Thus preoccupation with the five regular solids, how knowledge that the square root of two was irrational was…suppressed! This unease with the real world, in preference to the supposed abstract perfection of the heavens, was reinforced by Christianity (which dismissed scientific discovery that challenged scripture as heretical), and stifled philosophy and science for over a thousand years, until Leonardo, Copernicus, and Columbus, and the Enlightenment.
  • Here Sagan becomes explicit about religion: What do you do about conflicting gods from other lands? Zeus, Marduk? Suppose that they were invented by the priests? Then why not all of them? The world could be understood without the god hypothesis.

8, “Travels in Space and Time”

  • How can we travel to the stars? Can we travel close to the speed of light, or greater than it? Looking out into space is looking back in time.
  • We visit Tuscany, in northern Italy, in 1895, when Einstein wondered what the speed of light was relative to, and whether velocities of two moving objects add. To avoid paradoxes he concluded the special theory of relativity: you can’t add velocities, and you can’t travel at or above the speed of light. Despite how these conclusions clash with our common-sense notions.
  • We see what would happen if the speed of light were 40 mph, depicting a near-accident at a rural intersection. Funny things happen near that speed; time slows down; the young man Paolo could return to his village after a near-lightspeed trip and find his brother is an old man.
  • So we *can* go to the stars, even though we wouldn’t return until centuries might have passed on earth. If we could accelerate at 1g, the stars are only years away, and the known universe could be circumnavigated in 56 years ship time.
  • Can we travel to the past? Physicists think it’s fundamentally impossible. Paradoxes of changing history…unless there are threads of history. [[ The ideas briefly discussed here have been much speculated about in science fiction, for decades ]] How the past might have been about the same, if key figures removed. Yet if the Ionian tradition had prevailed (avoiding the dark ages) we might be going to the stars now.
  • Other solar system would have different arrangements of planets, different evolutions. Everything is made of starstuff; we are starstuff which has taken destiny into its own hands.

9, “The Lives of the Stars”

  • “If you wish to make an apple pie from scratch, you must first invent the universe.”
  • How many slices in half of an apple to get to an individual atom? About 90.
  • The episode/chapter traces the understanding of atoms, at Cambridge University (how an atom is mostly empty space), to our understanding of the 92 common elements. Modern physics and chemistry have reduced the complexity of the sensible world to an astonishing simplicity. Chemistry is just numbers. Each element has a different number of protons. The nuclear force holds the atom together. Multiples of helium nuclei (2 protons, 2 neutrons) make familiar elements. [[ This theme echoes David Deutsch’s observation that scientific theories become fewer and broader, replacing earlier separate theories not understood to be related. ]]
  • And then to where the elements came from: from the insides of stars. Depending on mass, stars die in three ways: white dwarf, neutron star, or black hole. Before final collapse, a star swells into a red giant. Some of these go supernova, in which rare elements are created by the intense explosion. Our sun is probably a third generation star. All elements except hydrogen and helium were made inside other stars: thus we are starstuff.
  • And radiation due to cosmic rays are drivers of evolution, via mutations.
  • Examples of primitive civilizations that marked ancient supernovae: the 1054 “guest star”, now the Crab Nebula.
  • Sagan imagines life in light gravity, or higher gravities, imagining Alice and that cat, and how gravity is a curvature of space. Would a black hole lead to a wormhole and then to a different universe entirely?
  • Then Sagan is back in Big Sur. We’re all solar-powered; we are the stars’ children.

Ch10, “The Edge of Forever”

  • Where the universe came from, and where it’s going. Everyone has in common the experience of birth, and so we imagine the birth of the universe, which we currently understand has happening 15 billion years ago, with the Big Bang.
  • The key to cosmology is the Doppler effect. (Live example of a train going past.) Mount Wilson, complete in 1917, and how a janitor, Humason, became an observer alongside Hubble (this filmed at the actual observatory, with actors), and their discovery that the more distant a galaxy, the greater the red shift: thus the expansion of the universe.
  • Is space curved? Sagan imagines flatland, then a fourth dimension, and speculates that moving in a continuous direction would bring you back to where you started, like walking around a globe. We don’t know whether the universe is open or closed. [[ We do now: it’s expanding even more quickly than we’d thought, cf. dark energy. ]]
  • Cultures have imagined gods that created the universe. But if the universe was created by a god, where did the god come from? Save a step and suppose the universe has always existed.
  • Scenes of other cultures: people herding animals, in fields, village scenes, harvest festivals. A tradition of cycles in nature, as on Earth; all such myths should be respected for perceiving this basic pattern. The Hindus, remarkably, imagined an ancient universe of billions of years, and an infinite number of other universes. The big bang might have been the end of a previous cycle. Does the universe oscillate?
  • Sagan at the Very Large Array in New Mexico: we can look back into time with radio telescopes, which are extremely sensitive, in order to detect if enough matter exists for the universe to be closed. But we don’t know yet.

Ch11, “The Persistence of Memory”

  • How information on how to live proceeds from genes, to brains, to books.
  • The variety of life on earth (location shots of a boat that records whale songs, with background on how 19th century steam ships interfered with whale communications) is due to common sets of genes, that make DNA; each creature is determined by some number of information bits encoded in the DNA. Some 5 billion for a human, equivalent to 1000 books.
  • Beyond that, we have brains. Our brain consists of a brain stem, then an R-complex (the reptilian brain), then the limbic system (the mammal brain), then the cerebral cortex (in primate, millions of years ago), the last the realm of intuition and critical analysis. [[ Sagan wrote a whole book about the brain, The Dragons of Eden. ]] The brain has 100 billion neurons, and 100 trillion connections between them, the equivalent of 20 million volumes. The brain library is one of loose-leaf books, with memories stored in lots of places.
  • The brain betrays vestiges of its evolution, just as cities are built on top of older versions of themselves, rather than periodically rebuilt from scratch.
  • When brains weren’t enough, we stored information outside our bodies—in books. In libraries. One can read perhaps a few thousand books in a lifetime; the trick is to know which ones to read.
  • Thus: cuneiform, 5000 years ago; paper, ink, printing, with many copies of earth work. Then, movable type in 1450, and within 50 years, 10 million printed books.
  • And now we have computers and satellites, communications across the world. And beings on other planets might have vaster more neurons; what would they be like? We launched messages on two Voyager spacecraft, in 1977, that might be found by such creatures. They would be interested in our culture, not our science (since the science would be the same).

Ch12, “Encyclopaedia Galactica”

  • About contact between alien civilizations. Why haven’t we been visited? There’s no good evidence.
  • Episode has dramatization of the famous Betty and Barney Hill incident, about a couple supposedly abducted by aliens late one night on a New Hampshire highway. But extraordinary claims require extraordinary evidence, and their best evidence – crude star maps that resembled nothing much – was worthless. And their story is claimed as one of the best such cases of supposed alien visitation.
  • Photos can be faked; home movies show asteroids; there’s never any compelling physical evidence.
  • Dramatization of Joseph Fourier and his student, Champollion, who figured out how to read Egyptian hieroglyphics, via the Rosetta Stone, in effect making contact with an ancient, alien civilization.
  • Now we try to make contact via radio astronomy, an Arecibo.
  • How many civilizations might be out there, in the galaxy? Sagan explores the famous Drake equation, making estimates for each factor, and gets a range from 10 to millions.
  • So where are they? No credible evidence of their visiting us. Other explanations? Maybe we’re the first. Maybe they all destroy themselves. Maybe they’re here but hiding. Or: it’s a big cosmos, why come here? A civilization might take thousands or millions of years to expand across space, into a network of outposts and pathways, perhaps compiling along the way an encyclopedia of everything known about all those worlds.
  • And we see ‘profiles’ of various planets and their biosphere, including one for Earth…

Ch13, “Who Speaks for Earth?”

  • The final chapter/episode brings together Sagan’s recurring ideas about the fate of humanity, whether we will survive without blowing ourselves up in nuclear war.
  • We see the dramatization of a French expedition to Alaska and the native Klingat, who were seeing outsiders for the first time, and who imagined their ship to be a giant raven. (Incidentally, this material is discussed in Chapter 12 of the book, though it’s depicted in episode 13.) That encounter was friendly, but not the Spanish visit to the Central America,  where Spanish greed for gold led to the destruction of the Aztec society.
  • Now all humanity is in jeopardy. How many other intelligences develop technology and then destroy themselves with it?
  • Scenes of nuclear explosions. Every nation has an excuse for building nuclear weapons, at great expense. How would we explain this, to outsiders? Who speaks for Earth? Shouldn’t we be making fundamental changes in society to avoid such conflict? We’ve made changes before: slavery eliminated, women liberated, some wars stopped, our recognition that the world is an organism.
  • Again, Alexandria did not flourish perhaps because its scholars did not challenge the political or religious beliefs of that society, e.g. slavery, while the surrounding population knew nothing of the knowledge inside the library. About Hypatia, her murder, and the library destroyed by 416. We mustn’t let it happen again.
  • Recap: the beginning; the history of the cosmos; the animation of evolution. We are a way for the cosmos to know itself.
  • The only sacred truth of science is that there are no sacred truths. Arguments from authority are worthless. It’s the best tool we have, and applicable to everything. More images, including a space shuttle launch. “These are some of the things hydrogen atoms do, given 15 billion years of cosmic evolution.”
  • Finally: Sagan along the Monterey coast again, releasing the dandelion.
  • From the book, page 318:

The Cosmos was discovered only yesterday. For a million years it was clear to everyone that there were no other places than the Earth. Then in the last tenth of a percent of the lifetime of our species, in the instant between Aristarchus and ourselves, we reluctantly noticed that we were not the center and purpose of the Universe, but rather lived on a tiny and fragile world lost in immensity and eternity, drifting in a great cosmic ocean dotted here and there with a hundred billion galaxies and a billion trillion stars. We have bravely tested the water and have found the ocean to our liking, resonant with our nature. Something in us recognizes the Cosmos as home. 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.

Page 338:

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 behavior. …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 that confront the world.

Page 339:

Present global culture is a kind of arrogant newcomer. It arrives on the planetary stage following four and a half billion years of other acts, and after looking about for a few thousand years declares itself in possession of eternal truths. But in a world that is changing as fast as our, this is a prescription for disaster. No nation, no religion, no economic system, no body of knowledge, is likely to have all the answer for our survival. There must be many social systems that would work far better than any now in existence. In the scientific tradition, our task is to find them.

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