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(Illustration by Jody Hewgill)

Why Carl Sagan is Truly Irreplaceable

No one will ever match his talent as the “gatekeeper of scientific credibility”

We live in Carl Sagan’s universe–awesomely vast, deeply humbling. It’s a universe that, as Sagan reminded us again and again, isn’t about us. We’re a granular element. Our presence may even be ephemeral—a flash of luminescence in a great dark ocean. Or perhaps we are here to stay, somehow finding a way to transcend our worst instincts and ancient hatreds, and eventually become a galactic species. We could even find others out there, the inhabitants of distant, highly advanced civilizations—the Old Ones, as Sagan might put it.

From This Story

No one has ever explained space, in all its bewildering glory, as well as Sagan did. He’s been gone now for nearly two decades, but people old enough to remember him will easily be able to summon his voice, his fondness for the word “billions” and his boyish enthusiasm for understanding the universe we’re so lucky to live in.

He led a feverish existence, with multiple careers tumbling over one another, as if he knew he wouldn’t live to an old age. Among other things, he served as an astronomy professor at Cornell, wrote more than a dozen books, worked on NASA robotic missions, edited the scientific journal Icarus and somehow found time to park himself, repeatedly, arguably compulsively, in front of TV cameras. He was the house astronomer, basically, on Johnny Carson’s “Tonight Show.” Then, in an astonishing burst of energy in his mid-40s, he co-created and hosted a 13-part PBS television series, “Cosmos.” It aired in the fall of 1980 and ultimately reached hundreds of millions of people worldwide. Sagan was the most famous scientist in America—the face of science itself.

Now “Cosmos” is back, thanks largely to Seth MacFarlane, creator of TV’s “Family Guy” and a space buff since he was a kid, and Ann Druyan, Sagan’s widow. They’re collaborating on a new version premiering on the Fox Network on Sunday March 9. MacFarlane believes that much of what is on television, even on fact-based channels purporting to discuss science, is “fluff.” He says, “That is a symptom of the bizarre fear of science that’s taken hold.” The astronomer Neil deGrasse Tyson, of the American Museum of Natural History in New York City, serves as narrator this time, giving him a chance to make the case that he’s the Sagan of our generation. “‘Cosmos’ is more than Carl Sagan,” Tyson told me. “Our capacity to decode and interpret the cosmos is a gift of the method and tools of science. And that’s what’s being handed down from generation to generation. If I tried to fill his shoes I would just fail. But I can fill my own shoes really well.”

It’s an audacious move, trying to reinvent “Cosmos”; although the original series ran in a single fall season—and on public television!—it had an outsize cultural impact. It was the highest-rated series in PBS history until Ken Burns took on the Civil War a decade later. Druyan loves to tell the story of a porter at Union Station in Washington, D.C. who refused to let Sagan pay him for handling luggage, saying, “You gave me the universe.”

The revival of “Cosmos” roughly coincides with another Sagan milestone: The availability of all his papers at the Library of Congress, which bought the Sagan archive from Druyan with money from MacFarlane. (Officially it’s the Seth MacFarlane Collection of the Carl Sagan and Ann Druyan Archive.) The files arrived at the library loading dock in 798 boxes—Sagan, it seems, was a pack rat—and after 17 months of curatorial preparation the archive opened to researchers last November.

Seth MacFarlane and Ann Druyan, who are reviving “Cosmos,” view Sagan’s papers at the Library of Congress. (Paul Morigi / Getty Images)
(Everett Collection)

The Sagan archive gives us a close-up of the celebrity scientist’s frenetic existence and, more important, a documentary record of how Americans thought about science in the second half of the 20th century. We hear the voices of ordinary people in the constant stream of mail coming to Sagan’s office at Cornell. They saw Sagan as the gatekeeper of scientific credibility. They shared their big ideas and fringe theories. They told him about their dreams. They begged him to listen. They needed truth; he was the oracle.

The Sagan files remind us how exploratory the 1960s and ’70s were, how defiant of official wisdom and mainstream authority, and Sagan was in the middle of the intellectual foment. He was a nuanced referee. He knew UFOs weren’t alien spaceships, for example, but he didn’t want to silence the people who believed they were, and so he helped organize a big UFO symposium in 1969, letting all sides have their say.

Space itself seemed different then. When Sagan came of age, all things concerning space had a tail wind: There was no boundary on our outer-space aspirations. Through telescopes, robotic probes and Apollo astronauts, the universe was revealing itself at an explosive, fireworks-finale pace.

Things haven’t quite worked out as expected. “Space Age” is now an antiquated phrase. The United States can’t even launch astronauts at the moment. The universe continues to tantalize us, but the notion that we’re about to make contact with other civilizations seems increasingly like stoner talk.

MacFarlane, Tyson, Druyan and other members of Sagan’s family showed up at the Library of Congress in November for the official opening of the Sagan archive. The event was, as you’d expect, highly reverential, bordering on the hagiographic. One moment reminded everyone of Sagan’s astonishing powers of communication: After the speakers finished their presentations, the organizers gave Sagan the last word, playing a tape of him reading from his book Pale Blue Dot.

Recall that in the early 1990s, as Voyager I was heading toward the outer reaches of the solar system, Sagan was among those who persuaded NASA to aim the spacecraft’s camera back toward Earth, by then billions of miles away. In that image, Earth is just a fuzzy dot amid a streak of sunlight. Here’s Sagan, filling the auditorium with his baritone, lingering luxuriantly on his consonants as always:

“That’s here. That’s home. That’s us. On it, everyone you love, everyone you know, everyone you have ever heard of, every human being who ever was, lived out their lives...[E]very king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every revered teacher of morals, every corrupt politician, every superstar, every supreme leader, every saint and sinner in the history of our species lived there–on a mote of dust suspended in a sunbeam.”


He started young. In the Sagan papers, there’s an undated, handwritten piece of text—is it a story? an essay?—from the early 1950s in which Sagan, then an undergraduate at the University of Chicago, sounds very much like the famous scientist-essayist he would come to be:

There is a wide yawning black infinity. In every direction the extension is endless, the sensation of depth is overwhelming. And the darkness is immortal. Where light exists, it is pure, blazing, fierce; but light exists almost nowhere, and the blackness itself is also pure and blazing and fierce. But most of all, there is very nearly nothing in the dark; except for little bits here and there, often associated with the light, this infinite receptacle is empty.

This picture is strangely frightening. It should be familiar. It is our universe.

Even these stars, which seem so numerous, are, as sand, as dust, or less than dust, in the enormity of the space in which there is nothing. Nothing! We are not without empathetic terror when we open Pascal’s Pensées and read, “I am the great silent spaces between worlds.”

Carl Edward Sagan was born in 1934 in Brooklyn, the son of a worshipful, overbearing mother, Rachel, and a hard-working garment industry manager, Samuel, a Ukrainian immigrant. As he entered adolescence he became an avid reader of science fiction, and gobbled up the Edgar Rice Burroughs novels about John Carter of Mars. His family moved to New Jersey, and he distinguished himself as the “Class Brain” of Rahway High School. In his papers we find a 1953 questionnaire in which Sagan rated his character traits, giving himself low marks for vigorousness (meaning, liking to play sports), an average rating for emotional stability and the highest ratings for being “dominant” and “reflective.”

The adult Sagan always sounded like the smartest person in the room, but in the papers we encounter this interesting note in a 1981 file, right after “Cosmos” hit it big: “I think I’m able to explain things because understanding wasn’t entirely easy for me. Some things that the most brilliant students were able to see instantly I had to work to understand. I can remember what I had to do to figure it out. The very brilliant ones figure it out so fast they never see the mechanics of understanding.”

After earning his doctorate Sagan began teaching at Harvard, and as a young scientist, he earned notice for research indicating that Venus endured a greenhouse effect that roasted the surface—hardly a place congenial for life. Later he would make strides in linking the changing surface features on Mars to planetary dust storms—dashing any hope that the markings were linked to seasonal changes in vegetation. It’s an obvious irony of his career that two of his major hard-science achievements showed the universe less hospitable to life, not more.

His speculative nature—freely discussing the possibility of life beneath the surface of the moon, for example—disturbed some of his colleagues. He seemed a bit reckless, and had a knack for getting quoted in newspaper and magazine articles. He published in the popular press—including writing the “Life” entry for Encyclopaedia Britannica. His own calculations in the early 1960s showed that there could be about one million technological, communicative civilizations in our galaxy alone.

And yet he thought UFOs a case of mass misapprehension. Among his papers is a November 1967 lecture Sagan gave in Washington as part of the Smithsonian Associates program. The very first question from an audience member was: “What do you think of UFOs? Do they exist?”

Though a skeptic about UFOs, Sagan had a tendency to be squishy in his comments about flying saucers, and at first he equivocated, saying there’s no evidence that these objects are alien spacecraft but leaving open the possibility that some “small fraction might be space vehicles from other planets.” But then he launched on a protracted riff about all the ways people get fooled.

“Bright stars. The planet Venus. The aurora borealis. Flights of birds. Lenticular clouds, which are shaped like lenses. An overcast [night], a hill, a car going up the hill, and the two headlights of the car reflect on the clouds—two flying saucers moving at great velocity in parallel! Balloons. Unconventional aircraft. Conventional aircraft with unconventional lighting patterns, like Strategic Air Command refueling operations. The list is enormous.”

Sagan was denied tenure at Harvard in 1968, but was quickly scooped up by Cornell. When not teaching and writing, he helped create plaques for the space probes Pioneer 10 and Pioneer 11. The plaques notoriously depicted a naked man and woman, with some graphical descriptions of the position of the Earth in the solar system and other scientific information—just in case the spacecraft bumped into alien scientists out there somewhere.

He gained new fans in 1973 with his book The Cosmic Connection: An Extraterrestrial Perspective, a kind of forerunner to “Cosmos.” Promoting that book, he made the first of more than two dozen appearances on Carson’s show over the next two decades. The Sagan papers include a letter from Sagan to Carson insisting that he’d never actually uttered the phrase most associated with him: “billions and billions.” Carson wrote back: “Even if you didn’t say ‘billions and billions’ you should have—Johnny.”


Sagan’s prominence made him the go-to person for the country’s most famous acidhead, Timothy Leary. On April Fools’ Day, 1974, Sagan and the astronomer Frank Drake visited Leary at the state mental hospital in Vaca­ville, California, where Leary had been locked up on drug possession charges.

Drake, a frequent Sagan collaborator, was a pioneer in the search for radio signals from extraterrestrial civilizations and was also known for the Drake Equation, which estimates the abundance of communicative aliens. Leary was a Harvard professor-turned-counterculture-guru who had become a proselytizer for the spiritual and mental benefits of hallucinogens. Lately, inspired by Sagan’s Cosmic Connection, he’d become obsessed with the idea of building a space ark to carry 300 carefully chosen people to another planet orbiting a distant star.

In this curiously emblematic meeting—which has been incompletely described in Sagan biographies but is now plain to see in the archives—Leary asked which star he should aim for. Sagan and Drake broke him the bad news: We don’t have the technology. All the stars are too far away. But true believers are not easily deterred. In a subsequent letter to Sagan, Leary reiterated his desire to “imprint the galactic point-of-view on the larval nervous system,” and said we just need fusion propulsion, longevity drugs and “exo-psychological and neuropolitical inspiration.”

“I am not impressed by your conclusions in these areas,” Leary wrote. “I sense a block in your neural-circuity[sic].”


Sagan originally planned to call his big TV series “Man and the Cosmos.” The title sounded sexist, however, and Sagan considered himself an ardent feminist. In the Sagan papers, we find this note by Sagan dated April 30, 1978:

1. There. [with some subtitle]
2. Cosmos. [also with some subtitle]
[Both have the advantage of simplicity.]

Fortunately, he went with option 2.

Druyan, in an interview, said of her collaboration with Sagan on “Cosmos”: “It was three years of the most intensive, globe-girdling, mind-stretching kind of enterprise. It was a real trial by fire. It felt like a kind of a long march. What I call climbing Mount Cosmos.”

“Cosmos” began with Sagan on a rocky California beach, saying, “The cosmos is all that is or ever was or ever will be.” Special effects transported him through the universe in a Ship of the Imagination, and back in time to the Great Library of Alexandria. “Cosmos” was as broad as its name, touching on Moon landings, famous comets, astrology, science, superstition, the human brain, extraterrestrial life and the fallibility of our species.

Sagan told the Washington Post TV critic Tom Shales, “I would like to, in the vernacular of the ’60s, blow people’s minds.” (Shales liked what he saw: The “program itself is spectacular and inventive: visually, a fabulous expedition; and intellectually, at least to novices in the sciences, an invigorating, stirring challenge.”)
It was a smashing success—and he soon discovered the special burdens of being that rarest of creatures, the celebrity scientist.


After “Cosmos,” everyone wanted a piece of Carl Sagan. They wanted interviews, book blurbs, annotations of manuscripts. They wanted him to give speeches and participate in conferences. Most of all, they wanted his affirmation. They wanted him to listen to their ideas about God and the nature of reality.

Sagan’s office at Cornell became inundated with letters from eccentrics. He labeled many of them “F/C,” which stood for Fissured Ceramics—Sagan-speak for “crackpots.”

Some correspondents contested his apparent atheism (though Sagan considered himself more of an agnostic, because he couldn’t prove scientifically that God didn’t exist). Some harangued Sagan about alien abductions or novel interpretations of the laws of physics.

“I have taken the liberty of incarcerating the alien in the basement of my home. He is eager to meet you. I will be happy to make the arrangements if you wish to visit with him.”

Another wrote: “I have been experimenting with the force of gravity and I believe that I can demonstrate just what it exists of and how it is caused.”

And another: “In two prior letters...I indicated to you that I have discovered a planet between Venus and the earth. I also explained that I am in Attica Correctional Facility and am unable to check out this discovery further without your assistance.”

The university eventually set up Sagan’s office with a system for recording phone calls. Here’s a partial transcript, from May 5, 1981, of a call from a man who said his name was James. He spoke to Shirley Arden, Sagan’s indefatigable secretary:

Arden: What kind of things do you feel he’s doing?

James: Well, fooling around with people’s brains, to be specific. With their right hemisphere....

Arden: And you feel that he needs to be punished for this?

James: His right hand will be chopped off and he will—he’ll learn to use his left hand and he’ll become a left-handed person.

Arden told other members of the staff what to do if she pressed the alarm button on her desk: “When the alarm button sounds they are to immediately notify Safety. Safety is to send an officer immediately.”


Sagan was a compulsive dictator, delivering his thoughts into a tape recorder that never seemed far from his lips. The conversational nature of his writing owes much to the fact that he didn’t type, and literally spoke much of the material and had a secretary type it up later. He also liked marijuana. Sometimes the pot and the dictation would be paired. A cannabis brainstorm would send him dashing out of a room to speak into his tape recorder, his friend Lester Grinspoon told one of Sagan’s biographers, Keay Davidson.

The Sagan papers aren’t organized by High and Not High, but there is a lot of material filed in a category with the peculiar name “Ideas Riding.” That’s his free-form stuff, his thought balloons, dictated and then transcribed by a secretary.

For example, from 1978, we find this dictated memo: “Why are palm trees tall? Why not? Because the seeds are so large that they cannot be carried by wind, insects or birds. A high launching platform is necessary so that the coconuts will settle far from the tree. The higher the tree, the further the coconut lands. Therefore, the competition among coconuts accounts for the high height of palm trees which live in environments where there is not a dense competing foliage of other species. To optimize the throw distance, the coconut must be spherical, which it is.”

Sagan did not reveal much of his inner life in his letters, but sometimes in “Ideas Riding” he lets down his guard, as was the case in July 1981: “I can talk about my father in ordinary conversation without feeling more than the slightest pang of loss. But if I permit myself to remember him closely—his sense of humor, say, or his passionate egalitarianism—the facade crumbles and I want to weep because he is gone. There is no question that language can almost free us of feeling. Perhaps that is one of its functions—to let us consider the world without in the process becoming entirely overwhelmed by feeling. If so, then the invention of language is simultaneously a blessing and a curse.”


Sagan’s emergence as the country’s top science popularizer ruffled many of his colleagues. Much of science is, as Sagan himself noted, prohibitive in nature, setting limits on what is and is not physically possible—thou shall not go faster than the speed of light, and so on. Beyond that, the scientific community as a social and even political entity has a number of clear and well-enforced, if unwritten, rules, including, Thou shalt not speculate, thou shalt not talk about things outside your immediate area of expertise, and thou shalt not horse around on late-night TV talk shows.

The scientific community’s divided opinion about Sagan came to a head in 1992, when Sagan was on the verge of being elected, as part of a larger pool of 60 nominees, to the National Academy of Sciences. A rump caucus of scientists within the Academy made a fuss, saying Sagan hadn’t accomplished enough in his research. After a hot debate, with Sagan supporters defending his hard-science achievements, the frowners prevailed, and Sagan’s name was flicked from the list of the newly anointed. Sagan received condolence letters from outraged colleagues; in an interview with me a few years later he shrugged it off, saying he’d always assumed he’d never get in. But Druyan told me, “It was painful. It seemed like a kind of unsolicited slight.” The Academy tried to salve the wound in 1994 by giving Sagan an honorary medal for his contributions to public understanding of science.


Sagan became gravely sick with the blood disorder myelodysplasia in 1994, and underwent a bone marrow transplant from his sister, Cari. Sagan, then 60, wanted everyone to understand that although he was facing the possibility of a premature death, he would not seek comfort in some traditional religious belief in an afterlife.

In 1996, a man wrote to him asking about the distance to heaven. Sagan’s response: “Thanks for your letter. Nothing like the Christian notion of heaven has been found out to about 10 billion light years. (One light year is almost six trillion miles.) With best wishes...”

When a religious couple wrote to him about fulfilled prophecies, he wrote back in May 1996: “If ‘fulfilled prophecy’ is your criterion, why do you not believe in materialistic science, which has an unparalleled record of fulfilled prophecy? Consider, for example, eclipses.”

Sagan became agitated after reading a new book by the legendary skeptic Martin Gardner, whom Sagan had admired since the early 1950s. It suggested that perhaps there was a singular God ruling the universe and some potential for life after death. In November 1996, Sagan wrote to Gardner: “[T]he only reason for this position that I can find is that it feels good....How could you of all people advocate a position because it’s emotionally satisfying, rather than demand rigorous standards of evidence even if they lead to a position that is emotionally distasteful?”

Gardner responded: “I not only think there are no proofs of God or an afterlife, I think you have all the best arguments. Indeed, I’ve never read anything in any of your books with which I would disagree. Where we differ is over whether the leap of faith can be justified in spite of a total lack of evidence...”

I interviewed Sagan that spring in Seattle, where he was undergoing medical treatment, and although chemotherapy had ravaged his body he had lost none of his volubility or his enthusiasm for science, reason and the wonders of the cosmos. He felt confident that he could beat his disease.

We talked a lot that day about extraterrestrial life.

“I’d rather there be extraterrestrial life discovered in my lifetime than not. I’d hate to die and never know,” he said.

While he was in Seattle, his secretaries sent a fax daily to Druyan with a rundown on the mail, calls that had come in, speaking invitations, requests for interviews, requests to contribute a piece of writing to some upcoming anthology. Sometimes Sagan would annotate these faxes with a few instructions. Toward the very end he would sometimes merely cross out a paragraph. Couldn’t do it. He was out of time.

Sagan died shortly after midnight on December 20, 1996. He was 62.


Sagan had a few core beliefs, including the sense that there is an order and logic to the universe, that it is fundamentally a benign place, congenial to life and even intelligent life. His cosmos was primed for self-awareness. He sensed that humanity was on the cusp of making a cosmic connection with advanced civilizations (and no doubt that a certain Brooklyn native would be in on the conversation!). In effect, he believed he was fortunate enough to live in a special moment. That notion rubs uncomfortably against the Copernican principle, after the 16th-century discovery that the Earth is not the center of the solar system, which tells us that we should never assume we are in a special place—not in space and not in time.

The cosmos, for whatever reason, declined to produce during his lifetime the intragalactic communication Sagan expected.

Where are they? The question is known as the Fermi paradox, after the physicist Enrico Fermi, who blurted it out one day at Los Alamos in 1950. The U.S. was actively working on developing a space program, so why wouldn’t aliens on distant worlds? And if they did, why hadn’t they come to visit? (Never mind the sketchy UFO reports.) The Fermi paradox has become more searing in recent years, ironically because of the discovery of extrasolar planets.

In late 2013 scientists announced that based on extrapolations of data from NASA’s Kepler Space Telescope, which scrutinized a tiny patch of the sky, there may be as many as 40 billion planets that are roughly the size of the Earth and in orbits around their parent stars that put them in what we consider to be the “habitable zone.” Even if the Kepler-data extrapolation is off by an order of magnitude, or two orders, that leaves an astonishing amount of apparently life-friendly real estate in the Milky Way galaxy—which is, of course, just one of, yes, billions and billions of galaxies.

But our telescopic survey of the heavens, with the Hubble telescope, the Kepler and numerous ground-based observatories, has failed to detect anything that looks artificial, much less pick up any signals or messages.

Geoff Marcy, the University of California at Berkeley astronomer who has found scores of exoplanets, and who has diligently searched for signs of anything artificial in the data, says the silence is significant: “If our Milky Way Galaxy were teeming with thousands of advanced civilizations, as depicted in science-fiction books and movies, we would already know about them. They would be sending probes to thousands of nearby stars. They would have a galactic Internet composed of laser beams at various wavelengths shooting in all directions, like a museum security system. They would reveal enormous infrared waste heat from their vast energy usage.”

For his part, Tyson says, “I think life may be as plentiful as [Sagan] suggested, but I’m more skeptical about what he’s calling civilizations. But this is a matter of flavor, of how you interpret the data.”

Sagan readily acknowledged that he did not have evidence of extraterrestrial life, much less intelligence. It is a measure of his devotion to scientific reason that he was willing to admit, to the end of his days, that he still didn’t have the goods, that he still hadn’t found what he’d been looking for.


In December I attended the Sagan Lecture at the fall meeting of the American Geophysical Union, in San Francisco. The speaker was the planetary scientist David Grinspoon. He had grown up calling Sagan “Uncle Carl.” His father, Harvard psychiatry professor Lester Grinspoon, was Sagan’s best friend. The younger Grinspoon delivered a fascinating talk that, in the gentlest of ways, demolished one of the central tenets of Sagan’s worldview.

Sagan had talked of the “great demotions.” Humanity had learned, painfully, that it did not live on a planet at the center of the universe, and further demotions followed. We were not (in Sagan’s view) the purpose of the Creation, not specially chosen by a divine authority, and were in fact just one evolutionary twist in a complicated biosphere shaped by the mindless process of natural selection. If we were ever to make contact with another intelligent species, those aliens would in all probability be smarter, because they’d be older, more advanced, just as a statistical likelihood. Sagan’s view of human ordinariness was framed as the “principle of mediocrity.”

But here was the younger Grinspoon talking about the Anthropocene—the idea that human beings are changing the Earth so rapidly and dramatically that our presence is becoming part of the geological record. And we can’t pretend it’s not happening. We have to learn to manage this place. Grinspoon made an analogy: It’s as though we’ve just awoken to the fact that we’re at the wheel of a speeding bus on an unfamiliar road. And we realize we don’t know how to drive.

“We have to figure out how to drive this thing in order to avoid catastrophe,” Grinspoon said. Doesn’t this sound, he said, as if we’re giving ourselves a “great promotion”?

“Yes, kind of, we are, and it is disturbing,” meaning we are not cosmically inconsequential after all—we’re planet-changers. “But really the point of science is not to comfort ourselves with stories that make us feel good,” he said. “Science can’t ignore the Anthropocene because the Earth is becoming unrecognizable from what it was before we became a geological force.”

Would Sagan have been able to square his great demotions with this new Anthropocene concept? Of course. The universe isn’t about us. The Earth is but a grain of sand. But upon this humble rock we will make our stand. It’s a task that will require science and reason—but also courage and far-sightedness. So it is that Grinspoon says of his old “Uncle Carl”: “Lord knows we need him now.”


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