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A Conversation With Neil deGrasse Tyson

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Neil deGrasse Tyson is used to wearing a lot of hats. He is a leading astrophysicist, the director of the American Museum of Natural History's Hayden Planetarium, a columnist for Natural History Magazine, and the author or coauthor of six books. As host of NOVA's "Origins" miniseries, Tyson donned yet another hat, one that forced him to suppress his customary outspokenness to serve as dispassionate guide on a journey into the mysteries of the universe, the Earth, and life itself. In this interview, Tyson returns to his old self, holding forth on why he's not convinced there's intelligent life beyond Earth, why he feels role models are overvalued, and how he copes with the astronomical numbers that swirl around his head every day.

The start of everything

NOVA: What makes the study of origins so hot right now?

Tyson: Well, one thing that distinguishes us today from the discoveries of the past is the extent to which the exploration of the universe has become multidisciplinary. It was unthinkable not long ago that a biologist or paleontologist would be at the same conference as an astrophysicist. Now we have accumulated so much data in each of these branches of science as it relates to origins that we have learned that no one discipline can answer questions of origins alone. It requires the additional insights that one gets by merging not only the questions, but the answers, among scientific disciplines.

Now, for example, when you look for life on Mars, you need the astrophysicist to characterize the environment in which the planet is found. You need the chemist to understand the chemistry of the soils. You need the geologist to understand the rock formations. You need the biologist, because no one else will know what life will look like. You might even need a paleontologist to look for life that doesn't exist there today but might have left fossil remains.

NOVA: It's hard to imagine scientists in such diverse disciplines working well together. Do they?

Tyson: Initially it was like a shotgun wedding, where you'd say, "Well, I guess we have to talk to each other." And scientists in different disciplines don't speak the same language. They publish in different journals. It's like the United Nations: you come together, but no one speaks the same language, so you need some translators.

“The moons of the solar system may be more interesting than the planets themselves.”

But in the end, what happens is that new fields of astrobiology and astrogeology and astroparticle physics arise, and they begin to develop their own language that represents the intersection of the two—say, between astrobiology and biology. That's when you know you've created a new subdiscipline, or even a brand-new discipline.

NOVA: What are some of the most exciting recent discoveries in origins science?

Tyson: I would say one, we nailed the age of the universe. Two, we have measured the existence of dark matter and dark energy. Even though we don't yet know what they're made of, we know we can measure the effects they have on the origin and evolution of the universe. Another is the discovery that the moons of the solar system may be more interesting than the planets themselves.

NOVA: How so?

Tyson: It's contrary to our earliest expectations. We used to think, Our moon is dry and barren, so why should we believe anybody else's moon is interesting? But if you look at the moons of Jupiter, for example, you find that one of them, Europa, is covered with ice, and below the ice is an ocean of water that is maintained in the liquid state by energy pumped into it from its orbit around Jupiter. Where there's water on Earth, you find life as we know it. So if you find water somewhere else, it becomes a remarkable draw to look closer to see if life of any kind is there, even if it's bacterial, which would be extraordinary for the field of biology.

NOVA: The Cassini spacecraft has just reached Saturn, whose moon Titan is of special interest too, right?

Tyson: Yes. Of Saturn's 31 moons, Titan is especially targeted for its richness in organic compounds. That moon has its own probe, the Huygens probe, which is a deployable subprobe attached to the main Cassini spacecraft. The Huygens probe will plunge through the atmosphere—because Titan has an atmosphere for goodness sake! And it might have oceans, not of water but of liquid methane. You can only begin to imagine what kind of interesting chemistry we might find and what forms any possible life might take under such circumstances—perhaps life not as we know it, but as we don't know it.

NOVA: What great origins-related discoveries would you hope for in the coming decades?

Tyson: The discovery of life somewhere other than on Earth. That is an unimpeachable first goal in our exploration of the cosmos. And what's fascinating is the question of whether that life has DNA. It's a fascinating question, because either DNA is inevitable as the foundation for the coding of life, or life started with DNA in only one place in the solar system and then spread among the livable habitats through panspermia. Panspermia allows life on one planet to be thrust back into space by some meteor impact that sends a little shock wave and flings a rock to escape velocity. If you have stowaway bacteria on that rock, they could easily travel through space, particularly the radiation-hardy bacteria we know exist. They can land on and seed another planet, thereby not requiring that you have to create life from scratch multiple times and in multiple places.

Another possibility is that the life has encoding that has nothing to do with DNA. That would be more important for biology than finding other life with DNA, because it would be a way to encode life that no one has dreamt of before.

NOVA: What about as an astrophysicist? Do you have hopes for specific discoveries?

Tyson: I want to know what dark matter and dark energy are comprised of. They remain a mystery, a complete mystery. No one is any closer to solving the problem than when these two things were discovered.

It may be that the answer to those questions has implications elsewhere in science, and those are the best kind of discoveries, because you're not just addressing the question you sought to answer. It was the same with Einstein's relativity, for example. He didn't start the day saying, "I'm going to explain this peculiar behavior of Mercury's orbit." He had a whole other fish to fry. It turns out, the oddities of Mercury's orbit naturally flow out of this concept of relativity. That lends credence to the truth of the idea, because it answers questions you didn't even think of asking yet.

NOVA: Speaking of great discoveries, do you believe there's intelligent life elsewhere in the universe and, if so, will we ever detect it?

Tyson: I'm not convinced yet. I think that intelligence is such a narrow branch of the tree of life—this branch of primates we call humans. No other animal, by our definition, can be considered intelligent. So intelligence can't be all that important for survival, because there are so many animals that don't have what we call intelligence, and they're surviving just fine.

“I see it as a real honor and privilege and duty to serve others in their ambition to become scientists.”

I prefer to think of the search for life as the search for anything that falls between single-celled bacteria and life that has some kind of interesting purpose or function to perform. Then if we discover life that doesn't seem to have as much of a purpose, but it's still crawling around on the planet's surface, I think that would be an extraordinary discovery that's undervalued given how much Hollywood worries only about intelligent animals.

The sky is not the limit

NOVA: Having gone to the Hayden Planetarium as a boy, what's it like to be its director now? A dream come true?

Tyson: No, I never dreamed that I'd be director of the Planetarium. But now that I am, one of my greatest privileges is signing the certificates of completion for classes taken by youths and adults. I received these same certificates, signed by the head of the Planetarium, when I was a kid taking classes. I see it as a real honor and privilege and duty to serve others in their ambition to become scientists the way scientists and educators served my interest when I was young. To the extent to which it fulfills that goal, my role in the Planetarium creates for me a significantly more magnified pleasure in holding the position.

NOVA: What advice would you have for a budding astrophysicist?

Tyson: It depends on their age. If they're really young, I'd say the parents just need to get out of the way! So often parents will interfere with the curiosity of their kids without even knowing they're doing it. They'll interfere under the guise that the child is misbehaving, when if you look carefully at the behavior of children, in almost all cases it's exploratory.

If they're a little older, I'd say take full advantage of the cultural resources that your municipality has to offer. Usually it's free, or if it's not free, it's relatively cheap. My parents didn't know much science; in fact, they didn't know science at all. But they could recognize a science book when they saw it, and they spent a lot of time at bookstores, combing the remainder tables for science books to buy for me. I had one of the biggest libraries of any kid in school, built on books that cost 50 cents or a dollar.

NOVA: In your memoir, The Sky Is Not the Limit, you devote a chapter to discussing the challenges you and other African-American colleagues have faced, just because of the color of your skin.

Tyson: Yes, "Dark Matters."

NOVA: What advice would you give prospective young minority scientists on how to cope with such challenges?

Tyson: What you need, above all else, is a love for your subject, whatever it is. You've got to be so deeply in love with your subject that when curve balls are thrown, when hurdles are put in place, you've got the energy to overcome them. I can think of no greater, more important need than this, because when I look behind me, I don't see all that many [young minority scientists] coming after me. It would be one of the greatest tragedies in our society if that absence was only for want of support that could have completely transformed their life's trajectory.

“It’s a very unnatural habit to understand what a billion years is.”

That said, the racial challenges of today do not compare with the racial challenges of yesterday. My father tells of not being admitted into hotels. He had to go around to the back door, and he couldn't use the water fountain. I have no counterparts to those stories. But on whatever level it's happening, it can be corrosive to one's personal integrity and one's sense of self. It's essential to stay strong throughout all that and not let it get the best of you.

Also, I think role models are overvalued as something important in society. Typically, when you look for role models, you want someone who has your interests and came from the same background. Well, look how restricting that is. What people should do is take role models à la carte. If there's someone whose character you appreciated, you respect that trait. Someone whose moral fiber meant something else, you respect that aspect. I think that will increase the likelihood that you'll find a role model, amalgam though it is.

Cosmological questions

NOVA: What are you working on now in your work as an astrophysicist?

Tyson: Right now I'm part of a major collaboration to look at data from the Hubble telescope. It's a patch of sky that's being imaged to very, very deep sensitivity levels to try to get the limit of all galaxies in the universe. Once we resolve this, we're worried about how galaxies cluster, how they respond to their own mutual gravities, how they evolve over time.

NOVA: Do you have high hopes for the James Webb Space Telescope, which is designed to study distant galaxies?

Tyson: Absolutely. That telescope, although it's been billed as the follow-on to the Hubble Space Telescope, will not have the same image appeal. But it will be unprecedented in its ability to measure the formation of galaxies in the early universe, something the Hubble can't do. The Hubble telescope can measure them in different evolutionary states, but it can't see them actually forming. And that's a big gap in our current knowledge right now, how galaxies form. It doesn't have the sex appeal of the question What is the origin of life?, but it's no less important.

NOVA: Regarding the origin of life, the astronomer Alan Dressler has written that every atom in our bodies save hydrogen was once at the center of a star. Can you explain that?

Tyson: Sure. The big bang endowed the universe with hydrogen and helium and not much of anything else. That is, nine out of ten atoms are hydrogen, about one out of ten atoms is helium, and there are only trace amounts of other things. If there were no stars, that would be the beginning and end of the universe.

But there are stars, and stars manufacture heavy elements from light elements. They take hydrogen in and fuse the atoms to become helium, and helium fuses to become carbon, and carbon fuses to become silicon and nitrogen, and so on. Thus, elements other than hydrogen and helium have no origin other than the centers of stars. And stars not only manufacture the heavy elements, they also explode them into space. Since life itself thrives on these heavy elements, we owe our very existence to stars.

NOVA: One final question I've always wondered about: How do you get your mind around the astronomical distances and mind-boggling time spans you work with every day?

Tyson: You don't—you just grow accustomed to them. You have to keep telling yourself how much bigger a billion is than a million, how much bigger a million is than a thousand, and how much bigger a thousand is than a few. You keep reminding yourself of this, to the point where thoughts then occur naturally out of habit. But it's not a natural habit. It's a very unnatural habit to understand what a billion years is.

Consider the wealth of Bill Gates versus my own, for example. I'll still pick up a quarter if I see it on the street. Now, let's take the ratio of that quarter to my net worth—and I'm probably kind of average for people who are fully employed—and figure out what the corresponding amount would be to Bill Gates. It's like $45,000! In other words, if Bill Gates is in a hurry because he has to get to a meeting, it might be too much effort for him to bend over and pick up $45,000 on the street. You need examples like this to bring astronomical figures down to Earth, as it were.

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In this wide-ranging interview, Neil deGrasse Tyson shares his thoughts on everything from the latest findings in origins science to the challenges he faced as a minority on the road to becoming a scientist.


Jupiter's moon Europa fascinates planetary scientists because its surface is broken up into large plates that have shifted around, not unlike ice on a polar sea. The fracture lines in this false-color image may indicate where water below the plates has erupted onto the surface. Could an ocean, possibly with its own forms of life, exist below?

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Taken by the Cassini spacecraft, these three false-color, near-infrared images of Titan reveal the Saturnian moon's haze-obscured surface as never before. In the left and right images, the darker regions may be relatively pure water ice, while the brighter areas likely bear a much higher amount of simple hydrocarbons. The white spot visible in all three images near the south pole is a cloud of methane particles that suggests a dynamically active atmosphere in that region.

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Space theater

In junior high and high school, Tyson took astronomy courses in the Hayden Planetarium, little suspecting that one day he would be its director.

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"You've got to be so deeply in love with your subject that when curve balls are thrown, when hurdles are put in place, you've got the energy to overcome them," Tyson says of coping with racial prejudice.

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James Webb

Scheduled for launch in 2011, the James Webb Space Telescope will help scientists better probe the mysteries of both galaxy formation and dark matter.

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Back to the Origins homepage for more articles, interviews, interactives, and slide shows.

Interview conducted June 29, 2004, and edited by Peter Tyson, editor in chief of NOVA online

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