King of the Cosmos

A Profile of Neil deGrasse Tyson

By Carl Zimmer


January/February 2012

On a hay-mown crest, dozens of people are crouching in the dark. The Earth has turned away from the sun, and the sky has flowed down a color chart, from light gray to orange to bluish-black. A sliver of a waxing moon has appeared briefly and then slipped below the western horizon, leaving the sky to blinking airplanes rising from La Guardia fifty miles to the south, to satellites gliding in low orbit, to Jupiter and its herd of moons and to the great river of the Milky Way beyond.

The crowd that sits in this chilly field in North Salem, New York, is surrounded by a ring of telescopes. There’s a Dobsonian, a giant barrel-shaped contraption that’s so tall you have to climb a stepladder to look through its eyepiece. Small, squat Newtonian cylinders sit on tripods, rigged to computers that give off a weak lamp-glow from their monitors. A few older men are fussing over the telescopes, but everyone else is huddled on the grass.

“Just get snuggly. There’s nothing wrong with that. Get snuggly.”

The voice is deep and loud—not loud from shouting, but from some strange acoustic property that gives it a conversational boom. It comes from a man who looms in the dark at the edge of the crowd.

“We still have the remnants of what we typically call the Summer Triangle,” he says. “And the Summer Triangle is three stars that are about equally bright. So, one is here—”

“Oh my God,” the crowd murmurs.

The looming figure is Neil Tyson, the director of the Rose Center for Earth and Space at the American Museum of Natural History. He has just put the crowd into a swoon by switching on a laser and pointing it towards the zenith of the sky. The green beam seems to reach up from the field and touch the star.

“And one is here, and here,” he says, sweeping the laser across the sky to mark a stellar triangle. The squatters gasp, swear again, and laugh at themselves. Tyson’s laser is creating an optical illusion: he seems to pull the sky down into a dome that floats close overhead, like an astronomical Sistine Chapel.

“Here we have Deneb,” he says. “Everyone say Deneb!”


“Good. And down here we have Altair.”


“And up here we have Vega.”


“One of the telescopes is actually trained on a star that’s in the middle of this triangle,” Tyson says, moving his laser to a faint dot, called Albireo. “It’s right there. It doesn’t look very interesting at first, but when you whip out a telescope, what you’ll find is that this star is not alone, as a solo star. It has a companion star. Albireo is in fact my favorite star of the night sky. If you look closely, one star is this brilliant, beautiful blue color and the other is gold. And we know from astrophysics what must be true if an object is glowing at one or the other of those colors. Unlike what an artist will tell you, something glowing red-hot is the coolest among all the hots. You get way hotter than red-hot. If you crank the temperature, it becomes white hot. Crank it some more, it then begins to glow blue.”

Tyson moves the laser to other regions of the sky, to the feeble North Star, to Cassiopeia, to Sagittarius. As he talks, the people huddling on the ground blast questions at him. Where is Venus? Is that a satellite? Is that a satellite? Is the Chinese calendar based on the lunar cycle? Tyson stops to answer each question. He twirls his laser in a tight circle midway down the handle of the Big Dipper.

“If you look really carefully at it, you should be able to see two stars there,” he says. “How good is your vision?”

“Awesome!” a boy says.

“I can see it!” says another.

“Okay, who cannot see two stars inside my little circle here?” Tyson asks.

“Me,” says a third.

“Okay, therefore you cannot be drafted into the Roman army,” says Tyson. “That was their eye test. So this pair of stars is called Mizar and Alcor. Mizar is the brighter of the two. Alcor is the dimmer of the two. This is a very loosely bound double-star system. If you take out a telescope and point it on Mizar, that's a double star. Then if you take the telescope and point it on the brighter of the two stars that is the bright of these two stars, that's a double star. So what you have here,” Tyson says, “is a double-double-double star system. All in mutual, harmonious orbit around their common center of gravity. Such is the lay-out of this cosmic ballet that we call the universe.”

For most of the people huddling on the ground, tonight is the first time they’ve spent such an extended period looking up at the sky. For three hours, Tyson keeps his audience staring so hard at the heavens he cramps their necks. He speaks of galaxies and the delusions of astrology, how to calculate latitude, the fate of the universe. It is not a lecture. He delivers something more akin to a solo concert. Although he is a card-carrying astrophysicist with a long list of scientific papers in publications like Astrophysical Journal, Tyson has turned himself into a rock-star scientist. He plays to sold-out houses. He appears on the Daily Show with Jon Stewart, on the New York Times bestseller list, on Twitter (@neiltyson, with 242,400 followers as I write this). He is now shooting a remake of Carl Sagan’s classic Cosmos series, which will air on Fox in 2013.

Tyson spreads himself so wide for two reasons. One is that there’s so much in the sky to talk about. The other reason is down here on earth. For all the spectacular advances American science has made over the past century—not just in astrophysics but in biology, engineering, and other disciplines—the best days of American science may be behind us. And as American science declines, so does America. So here, in the dark, under the stars, Tyson is going to try to save the future, one neck cramp at a time.

Tyson first saw the Milky Way when he was nine, projected across the ceiling of New York’s Hayden Planetarium. He thought it was a hoax. From the roof of the Skyview Apartments in the Bronx, where he grew up, he could only see a few bright stars. When Tyson turned eleven, a friend loaned him a pair of 7x35 binoculars. They weren’t powerful enough to reveal the Milky Way in the Bronx sky. But they did let him make out the craters on the moon. That was enough to convince him that the sky was worth looking at.

He began to work his way up through a series of telescopes. For his twelfth birthday, he got a 2.4-inch refractor with three eyepieces and a solar projection screen. Dog walking earned him a five-foot-long Newtonian with an electric clock for tracking stars. Tyson would run an extension cord across the Skyview’s two-acre roof into a friend’s apartment window. Fairly often, someone would call the police. He charmed the cops with the rings of Saturn.

Tyson took classes at the Hayden Planetarium and then began to travel to darker places to look more closely at the heavens. In 1973, at age fourteen, he went to the Mojave Desert for an astronomy summer camp. Comet Kahoutek had appeared earlier in the year, and Tyson spent much of his time in the Mojave taking pictures of its long-tailed entry into the solar system. After a month he emerged from the desert, an astronomer to the bone.

It was a good time for a plunge into astronomy. Neil Armstrong had landed on the moon four years earlier. In 1973, NASA launched Pioneer 11, and the space probe began its journey to the asteroid belt and then onward to the outer Solar System. At the suggestion of Carl Sagan, NASA had bolted a plaque to Pioneer, showing a naked man and woman, along with a cosmic map of Earth’s location, should an alien civilization encounter the probe after it left our neighborhood.

Tyson learned how astronomy could also bring out the crazies. As Kahoutek got closer to Earth, a cult called the Children of God warned it was an omen that the world was about to be destroyed. Psychics declared that the comet disrupted the psychomagnetic equilibrium of the planets and would cause mass violence. Timothy Leary had a happier opinion of Kahoutek, which he preferred to call Starseed. It comes, Leary said, “at the right time to return light to the planet earth."

In the face of this superstition, Tyson wished he could talk to people about the beauty of the universe. At age fifteen, he was invited to talk to a continuing education class. He delivered an hour-long lecture to fifty adults, showing them his pictures of planets, stars and Kahoutek. As he stood before his first audience, he didn’t know that he would be doing this sort of thing for the rest of his life. But it certainly felt right. “For me,” Tyson later wrote, “talking about the universe was like breathing.”

Tyson graduated from Bronx High School of Science in 1976 and went to Harvard. He wrestled, tutored prisoners in math, and studied astrophysics. In his sophomore year, he was talking with a fellow black student, a senior who was about to start a Rhode scholarship. The senior was appalled to hear Tyson talk about astrophysics. “Blacks in America do not have the luxury of your intellectual talents being wasted on astrophysics,” he declared.

It was as if Tyson had been stung by a hornet. The stinger buried itself so deep inside him that it took nine years to work its way out. By then, Tyson was finishing his Ph.D. in astrophysics at Columbia. During graduate school, he became the department’s go-to person when reporters called to ask about something weird in the sky. He began answering questions readers sent to StarDate magazine. One day, a satellite recorded explosions on the surface of the sun, and a local television station asked Tyson if he would talk about it on camera. After the filming, he went home and watched himself on television. It was the first time he could recall ever seeing a black scientist speaking as an expert on American television. His college shame fell away.

By the time Tyson finished his Ph.D. and took a job at Princeton, he had turned his StarDate columns into his first book, Merlin’s Guide to the Universe. And it was that willingness to engage the public that brought him a visit from representatives from the American Museum of Natural History. They wanted to talk to him about the Hayden Planetarium. Pushing sixty, it was in bad need of a renovation.

“They were really just coasting on the glory days of the fifties, sixties, and seventies,” Tyson told me. “I said, ‘Change out all the exhibits. Oh, and by the way, you should start a research department there.’”

Tyson began to split his time between teaching at Princeton and working as a staff scientist at the Hayden planetarium, helping to plan its redesign. “It went beyond just a facelift,” he said. “It was an entire reworking of the architecture, which involved demolition and reconstruction.”

Tyson held out until Frederick Rose, a New York developer and philanthropist, put twenty million dollars on the table for a renovated planetarium and a department of astrophysics. “Where do I sign?” Tyson recalled thinking. In 1996, he was appointed the Frederick P. Rose director of the Hayden Planetarium. He could still recall being mesmerized by the Milky Way the first time he stepped foot in this building, as a nine year old. Four decades later, he was in charge.

When the Rose Center finally opened in 2000, it startled a city grown blase about new buildings. Paul Goldberger, the New Yorker architecture critic, wrote that the building “is a temple of serene geometries, perhaps the purest piece of monumental architecture built in the United States since the Washington Monument went up on the Mall.”

A decade later, on a bright Sunday morning in 2010, a smattering of kids and their parents gathered to celebrate the Rose Center’s 10th anniversary. By 11 am, every chair was occupied. Tyson climbed onto the dais dressed in a dark suit and bright tie covered in Renaissance drawings of the sky. He welcomed the crowd. “Just a show of hands—who has come from far away?” A few hands went up. “How far?” he asked one person. “Oregon?” He pointed to someone else. “Florida? That’s also far. Welcome. You should stay here because pretty soon all of Florida is going to be underwater. So this is good up here in the Northeast, as sea levels rise.”

He talked about the design of the center, how he and his colleagues had replicas of the planets arrayed around the giant planetarium’s signature sphere. Eight of them.

“Pluto is a planet!” a boy in the back shouted. The crowd rumbled.

“Apparently, people are still angry about this,” Tyson replied with a smile.

Tyson’s decision to kick Pluto out of the league of planets may be the most famous thing he’s done so far. Yet he didn’t make a big deal of it at the time. In the late 1990s, astronomers were beginning to discover a vast belt of giant hunks of ice at the Solar System’s outer edge.

“Pluto and they look more alike than any one of them looks like anything else in the solar system,” Tyson explained to the crowd. “That’s a good excuse to group them. That’s how you make categories. That’s all we did.”

Tyson’s demotion of Pluto only came to the public’s attention when Kenneth Chang, a New York Times reporter, noticed there were only eight planets featured at the Rose Center. When Chang asked other astronomers to comment, they called the decision absurd. Letters of protest poured into the museum. But Tyson held firm, and in the years that followed, astronomers discovered other icy bodies at the edge of the solar system that were even bigger than Pluto. In 2006, the International Astronomical Union decided to classify it as a dwarf planet.

“By the way,” Tyson said, scanning the crowd. “Who's the kid who said, ‘Pluto is a planet?’ What's your name?”

The boy answered, “Sebastian.”

“Sebastian, a question for you. You know Pluto is small, right?”


“Do you know how small it is?”


“No, you don't know how small it is!” Tyson roared. When he works a crowd, he doesn’t maintain a cool composure, like his hero Carl Sagan. He has a touch of Chris Rock. “So how can you say Pluto must be a planet? For example, if the planet Saturn were a car, how big a car would Pluto be sitting next to it? Do you have any idea? If Saturn, the car, were like Saturn the planet, how little would you have to make a car to be the size of Pluto? Do you have any idea? Would it be like a Mini Cooper? Or what's that, the Smart Car? That little stubby car that's got no butt?” Tyson sidled around on stage, as the crowd laughed at the living essence of a car without a butt. “That little thing? You've seen those. Great for parking. You think it's that small, maybe?”

Tyson stood tall again. “I’ll tell you how small!” he shouted. “To make Pluto the size of a car relative to Saturn the car, it would have to be the size of a matchbox car sitting on the curb.” He squeezed his fingers. “Like that. There are six moons in the solar system bigger than Pluto—including Earth's moon. And practically everybody I know saying ‘Pluto must be a planet,’ did not know that. Did you also know that Pluto is mostly ice by volume? So that if you slid it into where Earth is right now, heat from the sun would evaporate that ice and it would grow a tail. That's no kind of behavior for a planet, I wouldn't think. There's a word for things with tails. What do we call them?”

The crowd answered, “Comets!”

“Comets, thank you. No, I think Pluto is happier now as the king of the comets, instead of being a pipsqueak planet.”

Tyson glared again at Sebastian. “So you agree with me? You admit it?”

Sebastian, arms folded, gave a nod.

“We have a convert, right there,” Tyson declared.

To write about scientists, you first have to sit down with them and talk for a long time. It’s usually not too hard to arrange this, since you can reliably find them at their office desk, at their observatory, or in their favorite swamp. Tyson is a moving target. At the Rose Center anniversary, I had to trot to keep up with him as he strode through the museum for assorted appointments with astronauts and a cappella singing groups. I interviewed him in cabs and subways. The longest stretch of time I got with Tyson was not in New York at all, in fact, but in Tulsa, Oklahoma, where he had been invited to give a talk at a 2300-seat auditorium.

The evening before the talk, I found Tyson in his room at the Ambassador Hotel. He wore a black sleeveless T-shirt on which was written, “What part of—“ followed by a hideously long scientific formula, “don’t you understand?” He sat in a chair, with a stack of boxes to one side. Out of the boxes he pulled one book after another, setting each one on another chair in order to sign it.

Tyson was in the middle of a frantic week. Two days earlier he had been in Los Angeles, to film a cameo on The Big Bang Theory, the remarkably successful sitcom revolving around the lives of two socially awkward physicists. “At one point,” Tyson said, “after one of the takes, a guy comes up to me and said, ‘You’re suffering from Nova-itis. You’re professing your lines instead of just speaking them.” (Tyson has been the host of a string of Nova programs on public television.) “I only have three lines but…I don’t know if I’m delusionally biased, but I think they were sort of a meaningful three lines.”

I later called Bill Prady, the co-creator and executive producer of The Big Bang Theory, to ask about Tyson’s visit to the show. Prady is a fan of Tyson’s from way back. “I had Mister Wizard and Carl Sagan growing up,” Prady said. “There were science celebrities. And I think that’s something there should be more of. Someone like Neil comes on television, he’s friendly, he’s funny, he’s a good teacher. More people like him would represent a positive shift in the culture.”

For Tyson, a show like The Big Bang Theory is worth a trip across the country. With an audience of thirteen million people a week, it can deliver a large injection of geek culture into pop culture. Carl Sagan took some tentative steps in that direction, appearing as a guest on the Johnny Carson Show. Tyson wants to go further. In 2009 he sat down in the talk-show-host chair, with a radio talk show called StarTalk. When I ask Tyson if it aired on National Public Radio he gave an emphatic no.

“It’s the anti-NPR,” he says.

Tyson has had Stephen Colbert on StarTalk confess his own geekhood, and he’s talked about astrobiology with Joan Rivers. “I said, ‘Joan, what happens if the aliens come, what do you do?’” Tyson recalled. “She said, `I don't care as long as they're single and Jewish.’"

He’s also embarked on a remake of Cosmos, working with the Ann Druyan, Carl Sagan’s widow and co-writer of the original series. Druyan asked Tyson if he would host the show, and then Seth McFarlane, the creator of Family Guy offered to bring them together with executives at Fox. Tyson decided it was a good place for the show. “If this only appeared on a science network, then people who already know science would be the ones who would watch it,” he says. If he can reach a huge audience of people who aren’t already science fanatics, “it would have the greatest chance of influencing the science literacy of the nation.”

After filming The Big Bang Theory in Los Angeles, Tyson got on a red-eye and flew back to New York to give a lecture the next day at a meeting of academic cosmetic chemists. “That was a first for me,” Tyson said. “So I just talked a lot about the chemistry of the universe.” After the lecture, he packed again and immediately flew to Tulsa.

In his Tulsa hotel room, Tyson was preoccupied with how he could talk the organizers of the lecture into letting him have a question-and-answer session instead. “I love Q and A,” he said. “It becomes a communal participation. There’s a vicarious flow through the questioner into my exchange with them from everybody else.”

Tyson was prepared to give them a regular talk if need be. He would race his audience through the cosmos, pausing along the way to talk about the latest science. Black holes, of course, are a mandatory stop. We like to imagine that black holes could transport us to another part of the universe, but recent research on black holes suggests that’s impossible. For many people, that finding was a kind of cosmic disappointment. But Tyson finds a fascinating consolation in the research. “Black holes remember what they’ve eaten,” he said. “As it evaporates trillions of years after it ate you, the inventory of evaporated particles matches exactly the inventory of particles in the mass that it ate. It remembers what you were. And to me that’s spooky.”

Tyson takes care not to oversell. If someone asks about string theory—the idea that all matter is ultimate made of multidimensional vibrations—he’s happy to talk about it, but he will also point out that it’s short on evidence. “The more your ideas are untestable, either in principle or in practice, the less useful they are to the advance of science,” Tyson said. “It’s a seduction, really, and it's controlling the hiring in physics departments. Every department feels like they need a string theorist. Meanwhile, there are other people who are doing actual experimental physics, or have testable hypotheses that are getting aced out of university appointments.”

Still, Tyson thought something important might someday come out of string theory. “They're pretty cheap to keep around. Pencil, pad, throw in a laptop—you’re done with the string theorist.”

After Tyson finished signing the books, he changed into a suit. His vest was embroidered with suns. He headed out for a dinner with fifty of Tulsa’s leading citizens, fielding questions for a couple hours. In the morning he got in a car and was driven through the ghostly downtown to the Tulsa Performing Art Center, a fortress of auditoriums, conference rooms, and pavilions. A Tulsa television crew interviewed him for an hour in a hallway, and then his handlers led him into a large room to talk to a hundred high school students and their teachers. The teachers asked most of the questions, mostly about what they could do to motivate their students. Tyson said parents should let their kids pull tablecloths off the table to learn about gravity, even if a few dishes get broken in the process. Afterwards the teachers and the students left the room and merged into the throngs flowing down the hallway, into the Chapman Music Hall. A great prairie of Oklahomans filled the auditorium. It was ten o’clock on a Thursday morning.

Tyson had failed to talk his hosts into a Q & A for the big show, so he went with the lecture. But as soon as came on stage he took off his shoes. “You’re comfortable, so I’m getting comfortable,” he said. He joked about how he had been introduced as, among other things, People’s sexiest astrophysicist in the world. “Consider the category,” he said. “Did I beat out Stephen Hawking? It’s just not the kind of distinction where you get big-headed about it. That’s all I want to say.” In the Chapman Music Hall the laughter didn’t clatter. It seemed to ripple out gently for miles.

Tyson began to talk about the universe, starting close by on the moon. He padded across the stage as he talked, in circles, up to the edge of the stage, backing away. He explained how a probe had recently crashed into a crater on the moon and kicked up a spray of dust and—intriguingly—ice. It may be possible for moon colonies someday to mine the ice, split the water molecules apart, and use their energy for rocket fuel. “So it’s the first step in long=term space travel,” he told the audience.

The giant screen behind Tyson filled with astro-porn—gorgeous NASA photos of other parts of the solar system. Mars with its own hints of water, Saturn capped by a vast hexagonal cloud, asteroids that might someday smash into Earth. Tyson reviewed an evolutionary tree of life on Earth, made up mostly of microbes (“Get over it”), and pondered the possibility of life on Mars or some Earth-like planet orbiting another star.

“Wow,” Tyson said when he checked his watch. “We are running late on time. I have to go faster. You with me? You ready?” He turned to the Large Hadron Collider in Switzerland, which has begun to smash protons at such huge energies that it may uncover a mythical particle known as the Higgs boson, predicted by some scientists to endow all matter with mass. Tyson jumped back to the Big Bang and then forwards through the growth of the universe, and then contemplated the possibility that our universe was one of many universes, each budding off of another through a black hole.

“This is way out there,” Tyson said. “There is no evidence to support any of this. There are some cogent theoretical evidence and philosophical arguments.” But if it were true, it would certainly be in keeping with the history of astronomy, he pointed out. “Every time we thought we were one, in fact we were many. ‘Oh, we’re the one Earth, the center of the universe.’ No, we’re one of multiple planets around the star. Okay, the sun is special. No, the sun is one of a hundred billions stars in the galaxy. The galaxy is special. No, it’s one of a hundred billion galaxies in the universe. All right, the universe is alone. Maybe not.”

Tyson checked his watch again. He was way past his hour now. “I’ve got to go quickly now. Are you okay here? Are you all right?” he asked. The audience applauded. “All right, here we go.” Tyson compared the elemental composition of our bodies to the abundance of elements in the universe: a close match. This union between ourselves and the cosmos could offer some solace for the feeling of insignificance astrophysics could bring. “The universe is in us,” he said.

After ninety minutes, Tyson was at last done. The audience gave him a standing ovation, after which he was hustled from the auditorium to a pavilion, where people who had bought a ticket could eat their Portobello mushrooms in the same room as Tyson, and ask him still more questions—whether the laws of physics can change over time (probably not), whether the universe was fine-tuned for our existence (no, the universe is out to kill us). Tyson came to the lunchtime podium, with two hours left before his flight home to New York, to answer questions yet again. But this time he carried a plate and fork to the microphone.

“I’m digging the pumpkin cheesecake pie here,” he said. “It doesn’t mean I don’t love you, but I’m eating this while I’m talking.”

One of the few times that I was able to sit down with Tyson in New York was on a day when Barack Obama was visiting the American Museum of Natural History. Rather than deal with the hassle of security, Tyson decamped to Smith and Wollensky, a midtown steak house, to participate in a wine auction. The second floor of the restaurant was filled with tables of bidders. A broad flat-screen television hung behind the auctioneer, full of lot numbers and bids. Tyson had a table to himself in the middle of the room, where he was answering emails on his laptop. A miniature metal bridge served as a paperweight, holding the auction catalog open to the page of the lot he wanted to bid on, a modest collection of mixed bottles.

“I tend to be a bottom-feeder, and I’m proud of that,” he said.

We talked over a rib-eye about the future. From time to time, Tyson took a break to wave his auction paddle or shake a waiter’s hand. For the past few years, the future of astronomy has been a part-time job for Tyson, as he has served on the Committee on the Decadal Astronomy and Astrophysics Survey 2010. The committee, assembled by the National Academies of Sciences from American astronomy’s top ranks, had as its mission to rank a vast number of proposals for future projects. At the top of their list is $1.6-billion Wide-Field Infrared Survey Telescope, or WFIRST.

The 1.5-meter-wide telescope would be delivered on a rocket 1.5 million kilometers from Earth, where it would be able to peer far across the universe, picking up infrared radiation from distant sources. WFIRST may be able to detect signs of planets orbiting other stars that ground-based telescopes have missed.

It took two years for Tyson and his colleagues to draw up their final list, which they released in August 2009. “A lot of meetings, a lot of discussions, a lot of reports,” is how Tyson describes it. “This was an important reality check on people’s scientific ambitions.”

Astrophysics is entering a precarious phase in the United States. As scientists probe deeper into the universe, they need increasingly sophisticated tools to make more progress. And those tools are becoming hugely expensive.

“Let me give you an example,” Tyson said. “The entire Rose Center for Earth and Space cost $230 million. That was years of fundraising and three years of demolition and construction. If the shuttle can’t land in Florida because of a thunderstorm and has to land at Vandenberg Air Force base? That’s $250 million.”

At the moment, WFIRST and the other missions Tyson and his colleagues have endorsed are stuck in line behind the James Webb Space Telescope, which is slated to lift off in 2015. The JWST is going to be delivered into space essentially as a rolled-up ball; once it emerges from its rocket, it will unfurl into a 6.5 meter mirror, over twice as big as Hubble’s 2.4 meter mirror. It’s a magnificent concept, but it’s also turning into a budgetary nightmare. Its cost has leaped from $5 billion to $6.5 billion. Nature called it “the telescope that ate astronomy.” Last summer, as Congress tried to find ways to cut its budget, the JWST ended up on a list of projects under consideration for elimination.

Shortly after Congress raised this possibility, Tyson appeared on Real Time with Bill Maher. He pointed out that the war in Afghanistan had already sucked up more money than NASA had in its entire fifty-year existence. “You are removing the only thing that gives people something to dream about tomorrow,” he warned.

The audience broke out in applause.

Tyson believes that the scientific community has to do its part to keep costs down, but he worries that politicians may not recognize that there is value to exploring the universe. The first exposure many people have to science is in a planetarium or on a NASA web site. By learning about black holes or dark energy, people become acquainted with science itself. Some of them go on to become scientists, and others become scientifically literate citizens. And that’s how to keep a country thriving.

“There’s no greater engine of economic growth than innovations in those fields,” Tyson said.

A truly galling sign of the times came in 2009, when Russia put together a space mission to the small asteroid Apophis. It has a small but genuine chance of hitting Earth in 2036. Recently Russia invited the United States to be a partner on the mission.

“Excuse me?” Tyson asked, setting down his fork. “Roll that tape back. Aren’t we the ones who propose missions and then bring other partners in with us? Aren’t we the leaders in this?”

The tale of Apophis speaks of a broader decline for Tyson—in America’s science education and its skills in science and engineering. “Katrina didn’t destroy New Orleans—the levees did,” he said. “What, we can’t hold back water? This is the twenty-first century? What is our problem?”

I asked Tyson if he thought something could stop America’s slide.

“Space exploration,” he said without missing a beat.

When the United States was sending men to the moon, science thrived. “You had to beat people back at the door who wanted to major in science and physics and become science teachers,” said Tyson. “You had people making the space program the measure of what is possible.”

But Tyson does not simply want to turn back the clock. As he explains in his upcoming book, Space Chronicles, the Cold War that made the Kennedy-era space program possible is long over. Tyson has been pondering a plan to take its place. “You multiply NASA’s budget a factor of two or three and you give it a grand vision,” he said. “You say, ‘We’re going back to the moon, we’re going to Mars. Oh, by the way, we’re going to be on Mars on this date, and right now we are looking at the elementary school children of the nation to see who has the right stuff, because by the time we’re ready to go to Mars, they will be the right age to be astronauts.’ You attract an entire generation of people into these epic projects. And to solve those problems that have never been solved before, they have to invent things. They have to have new ideas. New branches of mathematics get discovered. This feeds into society, into our culture. It’s a difficult sell, but I think it’s our only hope.”

The star party in North Salem, New York, is winding down. People are milling around the telescopes to see the moons of Jupiter or the Andromeda galaxy. The younger set and their parents have hiked away in the dark to find their cars. Tyson’s own son is fading fast and has clamped to his leg like a barnacle.

“Any other questions?” Tyson asks. “Oh, there was a question about dark matter, right?

A boy named Henry speaks up. “Yes. Thank you! Thank you, I've been waiting.”

“Okay, what do you know about dark matter?” Tyson asks.

Henry pipes up, musing in a high voice. “Just, like, there’s seventy percent or so—maybe even more—of the universe that's missing and we think that's made of dark matter.”

“Okay, so why are you asking me what dark matter is?” Tyson asks. The hardness is back in his voice—a joke varnishing a challenge.

“Because, like, that's all I know,” Henry admits. “I don't really get what it is.”

“Oh, so you think there's more known about dark matter than what you just told me?”

“Yeah. Sure,” Henry says. He doesn’t sound sure.

“We don't know any more than what you just said,” Tyson says.

“Wow, Henry,” Henry’s mother says. “That's neat.” Henry doesn’t pay her much mind.

“Okay so I'll give you a detail—wait!” Tyson turns on his laser and calls out to the crowd. “So there's another star I also want to point out.”

He shoots his laser into the sky, casting a circle around the Pleiades, the star cluster named for the seven sisters of Greek mythology. He talks about how the stars were born together as a cluster and have started their life orbiting the galaxy, but they will someday drift apart, as sisters so often do.

“Okay,” Tyson says, “everything we've ever seen in the universe has gravity—Earth, the moon. And you can tell how much gravity something has by how fast something moves around it. For example, I can use an equation, which was given to us by Isaac Newton. Remember these satellites we talked about? I said they're going 17,500 miles an hour and they're in orbit? Earth has to have a particular amount of gravity if you see that happening. I don't even have to know that Earth is there and I will know what it's orbiting because of the influence of its gravity on the satellite. Okay?”

“All right,” Henry says.

“All right. So now let's look around the galaxy. There are 100 billion stars. There are gas clouds, there are black holes, there's...”

“…dwarves,” says Henry.

“Dwarf stars, there are planets, there are comets. Add it all up. We've done this. Add it all up and say that should give me this much gravity. But when you look at how fast things are moving, you get six times as much gravity as the stuff that we know about is generating. It was originally called the missing matter problem. Where is the matter that's making this gravity that we see? Because everything we do count up doesn't get us where we need. We now call this the dark matter problem.

“But really we have no idea what's causing it. We so don't know what's causing it that we shouldn't even call it dark matter because that implies we have some understanding that it's matter. We don't know what it is. I could call it Fred. Eighty five percent all the gravity in the universe comes from something about which we know nothing.”

“That's a problem,” Henry declares.

“That's a problem,” Tyson calls back. “It's called the dark matter problem. It's been with us since 1936 and it's one of the longest-standing unsolved problems in astrophysics.”

“So that's going be your goal,” Henry’s mother says. “Grow up and solve that.”

“That's a little too big,” Henry says.

“Wait, that's only the beginning,” Tyson says, waving his finger close to Henry’s nose. “What year were you born?”

“In 1999,” Henry says.

“In 1998, a year before you were born, it was announced that the expanding universe is not only expanding, it is accelerating in its expansion. Meaning...”

“It's getting faster?” Henry asks.

“Faster and faster and faster,” Tyson says. “ We expected that the universe's expansion would be slowing down because all the gravity is trying to pull everybody back in. But we found the opposite is true. So we learned that there is a mysterious pressure in the vacuum of space that is pressing the universe to expand against the wishes of gravity. So we call that dark energy. We don't know what's causing it. We can describe it, we can say what it's doing, but we don't know what it is. When you add up the missing gravity or the missing cause of the gravity to this mysterious dark energy, it is ninety six percent of the universe.”

“That's a lot,” Henry says.

“Everything we know and love—electrons, protons, neutrons, light, black holes, planets, stars, everything we know and understand—occupies four percent of the universe. Dark matter and dark energy is everything else. So we’re just dumb—stupid about what’s driving this cosmos. And we've got top people working on it. Top people. This problem has been around a long time so a whole lot of top people have failed. We're waiting for another generation of top people to come along and help us out.”

When Tyson says “another generation,” he might as well be saying, “Henry.”

“Yeah!” someone calls out. It’s not Henry.

“Okay?” Tyson asks.

The night is now deeply dark. It’s good for seeing the Milky Way. It’s good for training telescopes on planetary nebulae. It’s good for contemplating the ninety-six percent of the world left to figure out. But it’s too dark now to see what Henry is thinking.