In a multi-part series with the popular astrophysicist Neil deGrasse Tyson, Bill Moyers explored a variety of topics, including the nature of an expanding, accelerating universe (and how it might end), the difference between “dark energy” and “dark matter,” the concept of God in cosmology and why science matters. “Science is an enterprise that should be cherished as an activity of the free human mind,” Tyson tells Bill. “Because it transforms who we are, how we live, and it gives us an understanding of our place in the universe.

The following is video of Moyers' two-part interview with Tyson, with full transcripts of the video appearing below:

Part 1:

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Part 2:

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Bill Moyers: Welcome. It's been almost 35 years since PBS premiered one of its most successful series of all time: Carl Sagan's “Cosmos.” Many of you may remember, as I do, his elegant exposition of the universe.

Over 600 hundred million people in more than 60 countries have now watched "Cosmos." But in the decades since, the universe has kept moving – literally, moving in every direction — and so has science. And that’s why “Cosmos” is returning this spring, this time on National Geographic Channel and Fox TV.

Our guide is the astrophysicist Neil deGrasse Tyson, America’s most popular scientist, the unabashed defender of knowledge over superstition and clearly the rightful heir to Carl Sagan's curiosity and charisma. So fasten your seatbelt for a whole new interstellar journey through tens of millions of years and hundreds of millions of miles to the farthest reaches of outer space.

Neil deGrasse Tyson is the Frederic P. Rose director of the Hayden Planetarium at the American Museum of Natural History here in New York, where he narrates a breathtaking new show titled “Dark Universe.” I took my 12-year-old grandson to see it over the holidays and we were mesmerized. Imagine: trillions of stars, a hundred billion galaxies and light traveling a hundred million years before reaching us here on earth.

That very planetarium, by the way, is where Neil deGrasse Tyson, a kid from the Bronx, age 9, first felt the universe subpoena him to become a scientist in thrall to the night sky. He’s written ten books including this memoir: “The Sky is Not the Limit” and this, his most recent: “Space Chronicles: Facing the Ultimate Frontier.” Oh, yes, I almost forgot – "People" Magazine once voted him the Sexiest Astrophysicist Alive! Welcome.

Neil deGrasse Tyson: That was a few years ago, actually.

BM: You only got it once.

NDT: I know.

BM: So no bragging rights, right? But you clearly got more of the star stuff that Carl Sagan said we're all made of. You just got more of it than we did.

NDT: Well, yeah, I've been touched by the stars perhaps more frequently than others.

BM: But you were just nine?

NDT: Nine, nine years old. A family trip. My parents, we were all native New Yorkers and my parents knew well the value of all of the cultural institutions of New York City. We went every weekend to one or another of these institutions, if not the zoo, the art museum, the many art museums, the Hall of Science.

And our first visit to the Hayden Planetarium for me — by the way, I would ultimately go as a school trip. But for family, I go there and I sit back and I'm certain — I love that where you said I was subpoenaed by the universe. I think I had no choice in the matter. I think the universe called me. Because when the lights dimmed and the stars came out when I was nine, I'd never seen a sky like that in my life.

BM: And you met Carl Sagan at 17, when you headed to the Cornell?

NDT: Yeah, well, so I applied to colleges knowing full well that I was interested in the universe. My application to Cornell, unknown to me, was forwarded to Carl Sagan. He was a professor of astronomy there. And I was deciding what college to go to, he sent me a personal letter. Man, I'm just a 17 — he's already been on "The Tonight Show" and had best-selling books.

Here's a personal letter said, "I understand you're considering Cornell and you like the universe, as do I. So why don't you come by? I can give you a tour to help you decide whether this is where you'll ultimately attend." So I went up there, he met me outside the astronomy building and gave me a tour of the lab.

One of my favorite memories is he reaches back, didn't even look, just reached back, pulled out one of the books that he wrote, and then signed it to me and I said, "That is awesome." And I said to myself, "If I’m ever in a position of influence the way he is, then I will surely interact with students the way he has interacted with me, as a priority."

BM: Do you remember seeing "Cosmos" when it first aired?

NDT: Yeah, but I was — by then, I was in graduate school. So it was … it didn't influence me the way it influenced others, because I was already established. But what it did tell me was that there was an appetite out there for science, if it's delivered in a way that's compelling and that's warm, that's compassionate, that is as though the person who is bringing the science to you is sitting next to you on the living room couch. And I thought, "That bedside manner is something that more science expositors should be doing." And I’ve used it kind of as a model for me going forward.

BM: So what are we going to learn about the universe from your “Cosmos” that Carl Sagan couldn't have known about? Well, let me put it this way: if Sagan were around to see your series, what would he learn about the universe that was unknowable 30-some-odd years ago?

NDT: Yeah, so that's a good question. So you need to think of "Cosmos" not as a documentary about science. By the way, since then, there have been many documentaries about science. And it's quite a fertile way of delivering the viewer to the frontier, or bringing the frontier to the viewer. So that's not the issue here. Because we all remember "Cosmos" and so many of these other documentaries maybe lived their moment, but then they fade.

Why did "Cosmos" not fade? It's not because it brought you the latest science. Although it also did that. It's because it displayed for you why science matters. Why science is an enterprise that should be cherished as an activity of the free human mind. Because it transforms who we are, how we live, and it gives us an understanding of our place in the universe. And it's these states of mind that you carry with you for the rest of your life.

So in the new “Cosmos,” that we are continuing this voyage. We're continuing this epic exploration of our place in the universe. We have other stories to tell beyond the ones that went on back then. Yes, right now, we are steeped in the ignorance of dark matter and dark energy.

At the time of the original series, there were no known planets outside of those orbiting the sun. We suspected they were there, but right now, we're rising through 1,000 planets happily orbiting stars that are not the sun. So these are not — that's not simply new science. It’s new vistas of thought and imagination.

BM: That place in the universe you talk about, as you know, scares some people. Someone once told Sagan that they didn't like astronomy because it made them feel small and insignificant in comparison with the grandeur of the universe. It clearly didn't affect you that way.

NDT: Well, it depends on what your ego is going into the conversation. If your ego starts out, "I am important, I am big, I am special," you're in for some disappointments when you look around at what we've discovered about the universe. No, you're not big. No, you're not. You're small in time and in space. And you have this frail vessel called the human body that's limited on Earth.

If you have no ego, if you just want to explore the world, look what happens. Here's — the conversation goes differently. You learn, oh, the molecules and the atoms of those molecules in my body are traceable to stars across the galaxy that have lived their lives, manufactured these elements, exploded them into the universe from which new generations of star systems were formed. So I look up at the night sky, I don't feel small, I feel large. I feel connected to the universe. It's not just we here on Earth, and that's there. We are one. And that link for me is one of the most profound discoveries of modern astrophysics. And if that, that should not make you feel small, that should make you feel large.

BM: At your planetarium show, which I went to the other day just over the holidays, it — I did feel small sitting there, looking up at a hundred million light years coming at us. But I also felt significant, the very fact that my grandson and I are here in this universe together is not insignificant.

NDT: Not only that, if the human mind applying known laws of physics to the universe allows us to even come with an understanding of what's going on out there.

BM: Have we figured out our galaxy?

NDT: So yes and no. All right, so the yes part is we've got some laws of gravity and optics and motion and yeah, we can use our knowledge of physics and our knowledge of the frontier science to land this probe on Mars within a few meters of the target spot. This is tens of millions of miles away, all right? There is no golf shot that's that accurate, all right?

Not even a hole-in-one is as accurate as what this shot is, okay? So what we do know that has been tested works. And that's quite a state of empowerment. But there's a saying where as your area of knowledge grows, so too does your perimeter of ignorance. Because this is the boundary between what you know and what you do not know outside of that area.

So we didn't even know to ask why is the universe accelerating against the efforts of gravity until we made the measurement that it was so. So before 1998, we couldn't even ask the question, we didn't even know to ask the question. So there's no sign that everything will ever be fully known, because this moving frontier continues to bring us more questions.

So can we measure how ignorant we are? Perhaps. We know that what we do know about the universe comprises four percent of everything that drives it. 96 percent of what's driving this universe in the form of dark matter and dark energy, we have no idea what —

BM: How do you know that it’s 4 percent? Because you haven't been able, have you, to measure what we don't know?

NDT: No, that — so that's a really cool question. In science, in astrophysics in particular, in all sciences, you have the capacity to measure something even if you don't know what it is.

BM: How so?

NDT: Well, so, for example, you could measure the fact that something is falling to the ground, but not know what it is or what's causing it or why. But you can measure it. You can measure the sun moving across the sky, build calendars based on that, and not even know that Earth goes around the sun. You can — and once you find out Earth goes around the sun, that flips your point of view, but it doesn't invalidate the concept of a year.

You can make all manner of measurements and not know what's causing it. We measure this thing we're calling dark matter. We measure this phenomenon dark energy that's forcing the universe to accelerate. When you add up what we know with those two things about which we don't know what's driving it, we only know 4 percent of what's driving the universe.

So that's humbling. That's humbling. The humblest person in this world is the astrophysicist. Because we are face to face with our ignorance every single day.

BM: But here's what puzzles me among other things about you astrophysicists. The magnitude —

NDT: I like the way you say that: "you astrophysicists."

BM: Yeah, well —

NDT: You guys.

BM: Yeah, you guys. You're dealing, as I saw your planetarium show, you're dealing with trillions of stars, a hundred million or more galaxies. How do you even imagine? How do you comprehend? How do you get your mind around, to use the clichÃ©, numbers of such magnitude?

NDT: We start early. I was —

BM: At nine!

NDT: Yeah, start them early. Think big early. In fact, calculus, as a branch of mathematics embraces the infinite. You sum an infinite series of numbers or expressions. You start thinking about large things early. And — or a large enumeration of objects early.

The way I like to think of it is you can give analogies. So one of my favorites: do you remember when McDonald's actually kept count of how many hamburgers they sold?

BM: Like the national debt —

NDT:Exactly. And they had an interesting sort of their own version of a Y2K problem. Because when they got to 99, there was not a slot for a third place. So there was no room enough to put one, zero, zero. So many of them just got stuck at 99 billion. So, I did the calculation for 100 billion hamburgers.

If you had — if you laid them end to end, you could go around the Earth, like, 32 times. Around the Earth, end to end. And then with what's left over, after you've done that, you can stack them to the moon and back with your 100 billion hamburgers. And that's about how many stars there are in the universe.

BM: How much Pepto-Bismol would you need to deal with that?

NDT: Didn't do the Pepto-Bismol calculation. So it's fun to think of large numbers in these other contexts. And of course, there are numbers larger than anything that enumeratable in the universe. The number of googol, back when googol was only a number, not also a corporation, googol is a one followed by hundred zeros. That number is larger than the account of particles in the observable universe.

So there's nothing in the universe that you can count that will add up to a googol. So what I did as a kid, you just have fun with numbers. And so when big numbers show up in the universe, I say, "Yeah, give me more." And what worries me is that when the debt goes to a trillion dollars, or possibly a quadrillion dollars, the national debt, I hope it's never a quadrillion, but when it gets there, do people really know how big that is? I don't think so.

BM: They don't.

NDT: So we're handicapped by not knowing, not being able to think creatively about how large these numbers are.

BM: I think you make me realize what I was experiencing there in the planetarium. When you started, you said, "We're not going to focus on what we can see, stars and planets, moons and nebulae, we're going to focus on what we can't see." And it was — it is?

NDT: Dark matter. That's the audacity of the show. I don't know any other show that said, "We're going to make as the topic, as the central theme, something about which we know hardly anything." And that was not only a scripting challenge. The writer here was Timothy Ferris.

BM: Very informative, he did —

NDT: I’m a fan of his work from way back. And so there's a scripting challenge, there's a visualization challenge. Our Director of Astrovisualization, which is a really cool title if you ever want one, I think, is Carter Emmart. These are people — he's a scientifically-literate artist, a visualizer.

And so you bring this, and others, you bring this talent together. You say, "Here's something, we don't know what it is. But it affects other things. Let's see how the rest of what we know can proxy for that which we do not know." By the way, this is how we know a black hole is out there. You can't see a black hole. But you see what effect a black hole has on everything — it wreaks havoc on its environment. So dark things have a way of manifesting themselves.

BM: Dark money as well. Dark energy, dark matter. How do they differ?

NDT: Well, unfortunately, they have similar-sounding names. And since we really don't know what either of them is, they — I don't think we should've named them. We should've given then fake names until we understood them. I've been voting for, Fred and Wilma. Something that doesn't give you any cosmic bias, all right? So I can tell you simply what dark matter is. But don't think of it as matter. I don't want to — I’m concerned —

BM: Like this table.

NDT: I don't — we don't know what it is. So I don't even want to use those two words. If anything, it's dark gravity. Because we look in the universe, and we see the effects of gravity, and they say, "Let's add up all the stars and galaxies and planets and comets and black holes, everything we know about, to account for this gravity that we see."

We account for one-sixth of the forces of gravity we see in the universe. There is no known objects accounting for most of the effective gravity in the universe. Something is making stuff move that is not anything we have ever touched.

BM: And that something you call, for lack of a better term?

NDT: Dark matter. But that even implies it's matter. What it truly is is dark gravity. Boom. That's a problem that's been around since the 1930s. It's the longest-standing, unsolved problem in astrophysics. So now, dark energy, we look out in the universe, and we expect to see the universe — our universe is expanding. We've known this since Hubble, the man Hubble, there was a man called Hubble, before he became —

BM: An astronomer.

NDT: Before he became a telescope back in the 1920s. And Edwin Hubble, he discovered not only that our galaxy is one of many, he discovered that galaxies are scattering apart from one another. This was the expanding universe in 1929. So when you reveal this, you say, "Okay, if we've been doing this for a while, all those gravities — all those galaxies are going to feel each other and they're going to ultimately want to slow us down, in this expansion."

So you go out to measure that. And that act led to a measurement that no one believed. That, initially, that the universe is accelerating. It's not slowing down, it's speeding up. These measurements were made back in the 1980s — back in the 1990s. A Nobel Prize has now been awarded for this discovery, just recently, a couple of years ago. The discovery papers were in 1998. So we don't know what’s going — some mysterious pressure in the vacuum of space, acting opposite the force of gravity, we don't know what it is. But we can measure its effect.

BM: So you measure it by measuring its impact on something else?

NDT: Precisely. An impact on the four percent that we can measure.

BM: So it's the pressure that's expanding the universe?

NDT: Something, use the word pressure, something is making the universe accelerate again. We know why we got — we had a big bang! Big Bang put everything into motion. I'm good with that. We're good. It's like me tossing a ball up into the air. It's moving upward even though it's slowing down, okay? Gravity is slowing down that upward motion. We expected gravity to be slowing down the expanding universe. The opposite is happening. We don't know what's causing it.

BM: What is the practical difference it makes, whether or not we find out what dark matter and dark energy are?

NDT: If you were around in 1920, maybe you would've been saying, "What's the practical difference of measuring the behavior of atomic nuclei, or atoms? We can't see atoms. Why do I care? This is just wood. This is a wood table. I'm in a leather chair. I'm good to go. Why are you investing so much energy, so much brain energy on understanding what's in the middle of an atom? That seems like a waste of this brilliance.”

In the 1920s, in addition to discovering we're not the only galaxy in the universe, and that the universe is expanding, that's a watershed decade. Because in that decade, quantum physics was discovered. And perhaps if you were around asking me that similar question then, you would've questioned the whole enterprise. Yet today, a third of the GDP of the world is generated on the creation, storage, and retrieval of information.

And the entire IT revolution cannot exist without an understanding of what's going on inside the atom. It is a quantum physics phenomenon. So you ask me, "Of what value?" I have no idea what value. Come back in 50 years, we'll have this conversation, and you’ll pull up the tape, and I will show you asking me of what value is the knowledge of how that works.

BM: One thing I took away from your planetarium show is that dark energy, as you just said, is responsible for the increasing rate at which the universe is pulling itself apart, right?

NDT: Yes. So I'd rather word that differently. I would say the universe is accelerating. We call that dark energy. So you're saying dark energy is responsible for that. There's something, whatever it is, we call it dark energy, that's what, that's our placeholder term, to describe what we observe, the acceleration of the universe.

BM: Well, I'm glad you explained that. Because —

NDT: By the way, there's — nothing known will stop this. So there's been some concern that maybe space does not have the flexibility necessary to allow such rapid expansion. And might space tear in some way previously unimagined, and what does that even mean? What — does the question even have validity?

BM: You mean the House of Representatives cannot pass an act that will stop this? As they would like to? No, seriously, I was going to ask you, because if the universe, that term — if that phrase, if the universe is pulling itself apart, does it ultimately disintegrate? Does it ultimately collapse?

NDT: No. There's no evidence to say that we will ever recycle ourselves. All evidence points to we're in a one-way trip to oblivion. So the universe expands, the temperature of the universe drops, all stars eventually will run out of fuel. So the stars, one by one, in the night sky will turn off. And in the extremely distant future, a quadrillion years into the future, there'll be no light coming to us in the day or night sky.

And, because all stars would have died. And all gas clouds would've made stars that would've — were going to make them, and there'd be no more new stars created. And so that the universe will end not with a bang, but with a whimper. And not in fire, but in ice.

BM: But don't worry; we will not leave you out in the cold. We'll be back, in fact, next time with Neil deGrasse Tyson to talk about whether scientists are discovering God in the dark matter that holds the universe together even as it hurtles ever outward from us.

* * *

Transcript of Part II of the interview:

BM: Neil deGrasse Tyson isthe director of the Hayden Planetarium at New York’s American Museum of Natural History.

He's also the narrator of a mesmerizing new show at the planetarium called Dark Universe, and this spring he’ll appear as the host of a remake of the classic PBS series Cosmos. You can see it on the National Geographic Channel and FOX TV …

BM: There were two strange sequences in your planetarium show. And I managed to go online and look at.

NDT: You've become a dark matter junky here. You're going online, you need more.

BM: I think —

NDT: You need more.

BM: So let's talk about the scene of dark matter from your show at the planetarium.

NDT: So what's going on here is you're viewing the structure of the large-scale universe. And what we've represented here are dark areas that themselves have more gravitational attraction than the light areas. So the light areas are drawing themselves to the dark areas. And so you, what happens is, as this happens over the eons, structure begins to manifest in the universe. And you see this web work, and it looks almost organic, or it looks like some kind of neurosynaptic map. The formation and collection of matter in the universe follows the laws of physics. And when you add in the dark matter, this extra gravity, it turns the universe into the universe that we see.

That's why we know that dark matter is real. We don't know what it is. But we know it's there because we can't make the universe as we see it unless we put this extra gravity into our simulations to match the gravity that we see.

BM: So you know it's something.

NDT: It's something. And there's some exotic ideas for it, by the way. Particle physicists are convinced that it might be an exotic particle that doesn't interact with us. Doesn't interact with our light, with our telescopes, but that it has gravity. So these particles are doing their own thing, invisible to us, but otherwise attracting our matter into their, nucleating us among them. So, but of course, a particle physicist would think that the solution is a particle. If you're a hammer, all your problems look like nails. One of the more intriguing accounts I've heard is if you have multiple universes, it turns out gravity can spill out of one universe and be felt by another.

And if we have another universe adjacent to ours, it could be that these sites where we see extra gravity is ordinary gravity in a parallel universe. And here we are, looking at it mysteriously like, "What is this?" It's like the blind man touching the elephant. "I don't know what this whole thing is, but here I can describe this part of it. And it's kind of textured, and it's, no, no, no, no, no, this got, it's smooth and hard." And, you know, you can't see the whole elephant. Maybe the elephant is ordinary gravity in another universe and we're feeling it and we're making stuff up just to account for it.

BM: You think there could be another universe?

NDT I don't see why not. Because back when we thought Earth was alone in the universe, we knew that there were other planets, that the Earth is just a planet, one of many. "Well, the sun is surely special." No, the sun is one of a hundred billion other suns. So, the galaxy, the Milky Way. No, the galaxy is one of hundred billion galaxies. How about the universe?

We have philosophical precedent to suggest that why should nature make anything in ones? Okay? Everything else we ever thought was unique or special, well, we found more of them. So philosophically, it's not unsettling to imagine more than one universe.

We also have good theoretical grounds for suggesting the existence of a multiverse. Where our universe is just one of some countless number of other universes coming in and out of existence, with slightly different laws of physics within them. That makes it a little dangerous. Because we are held together, involved in a universe where we work. Where we work physically. If you want to visit another universe, I would, like, you know, send something else ahead of you.

BM: So explain this to me, why is it I felt more satisfied watching the planetarium show, and as I'm sure we will watching the new "Cosmos," than I do personally from science fiction? I mean, I came away with a sense of really having experienced something authentic at the planetarium.

NDT: That's a great question. By the way, there are many science-fiction fans who also embrace the science reality. And people who are fans of fantasy and super heroes and science fiction and all the storytelling that goes on on the frontier, essentially, everyone there knows the difference between that frontier and the real science that comes out.

And they will judge the storytelling based on how much science it got right before starts inventing what the frontier of imagination would bring. If you violate a known law of physics, that's lesser science fiction than the one where you get all your physics right, now take me, now give me the warp drive. Now give me the transporter.

Take me beyond what we know. So, but to your point I think maybe it's the same effect as if you tour the Air and Space Museum in Washington, which has the history of flight, including space flight, that we could've made an exact, we museum people, could've made an exact replica of the Apollo 11 command module that went to the moon.

And then we'd say, "Here's an exact replica." So that's okay. But if I now say, "This actual thing went to the moon," intellectually, that means something different to you. Your eyes see exactly the same, you could make a replica, a perfect, that looks exact, with all the blemishes and all the heat shield damage. You could do that. But if you know it's the real thing, the meaning is magnified. And so yes, you go to our space show, it is the real science. And it is captivating you the way we'd only perhaps had thought science fiction could.

BM: Science fiction came first in a way, in terms of popular entertainment.

NDT: In some cases. But I'm a fan of JBS Haldane once said, I'm paraphrasing, he said, the universe is not only stranger than we have imagined, it's perhaps stranger than we can imagine. And when you realize that I, you understand why some people don't need to read the science fiction. Because black holes flaying stars in orbit around them and planets that have life forms undreamt of on Earth, this is, we're speaking real stuff here. Maybe that's as seductive as the imagination of someone standing on the frontier.

BM: One thing I took away from your planetarium show is that dark energy, is the increasing rate at which the universe is pulling itself apart, so how does it happen that we don't experience this expanding of universe as we walk down the street, or sit here in this building?

NDT: Yeah, because you live 80 years instead of billions. If you lived billions of years, oh yeah. This would be, "Hey, check that out. Look what I noticed." Yeah, I think about things you miss because of how short our time on Earth is. I'll, the best example I can give is when you walk around, say, "Oh, there's a nice, puffy cloud." You don't stare at it for an hour, you just notice it.

BM: Right.

NDT: If you do a time-lapse of the cloud, especially cumulus clouds, they are roiling, gurgling, boiling, places of condensed water vapor. They're alive. Yet, when you walk down the street, you think it's just sitting there peaceful and calm if it's just a simple cloud. So even something that does change in your lifetime, you don't think of as an actively roiling place, a cloud. So imagine longer, imagine mountain building on Earth. Imagine watching the Hawaiian islands pop up, or come, imagine watching ice ages come and go. Imagine watching species of life rise up, the dinosaurs, and then an asteroid comes, they go extinct essentially overnight on the, in the fossil record. That's a whole other way to see the world.

And it’s the task of the geologist, the astrophysicist to think about how that works. Fortunately, we have computers that can speed up time. I'll give you a great example. We used to have catalogues of galaxies. We say, "That's a really messed-up looking galaxy there. Let's make a catalogue of irregular galaxies."

So we have a catalogue of beautiful galaxies and irregular galaxies. And then people came up with theories, "How does a galaxy become irregular?" No one knew until we realized, galaxies collide. Galaxies feel each other's local gravity, collide, and it's a train wreck. And half the irregular galaxies are train-wrecked galaxies.

There's a famous astronomer, GÃ©rard de Vaucouleurs who said, a wrecked Lexus is still a Lexus. It just happened to be in a car accident. So we would learn. Now, how do you get to know that galaxies collide? You put in the forces of gravity on a computer, run the simulation, and watch it unfold. And there you can recreate the havoc that you see in the universe on a 100-million-year time scale.

BM: So when a child sings, or used to sing, I don't think they do anymore, "Twinkle, twinkle little star, how I wonder what you are," it's not twinkling. Something powerful, dramatic, and dynamic is happening to it. Right?

NDT: Well, yes, and we call that twinkling. So yeah, there's starlight coming billions of, or millions of light years, well it depends on if it's a galaxy, well, hundreds of thousands of light years across space, and it's a perfect point of light as it hits our atmosphere, turbulence in the atmosphere jiggled the image, and it renders the star twinkling.

And by the way, planets are brighter than stars typically, like Jupiter and Venus. Venus has been in the evening skies lately. And if you go, "Twinkle, twinkle, little star, how I wonder what you are," and you, I want, you want to wish upon the star, most people are wishing on planets. That's why their wishes don't come true. Because the planets are the first stars to come out at night.

BM: Don't you sometimes feel sad about breaking all these myths apart?

NDT: No, no, because I think it's, some myths are, deserve to be broken apart. The, out of respect for the human intellect. That, no, when you're writhing on the ground and froth is coming out of your mouth, you're having an epileptic seizure. You have not been invaded by the devil. We got this one figured out, okay? I mean, discovery moves on. So, I don't mind the power of myth and magic. But take it to the next frontier and apply it there. Don’t apply it in places where we've long passed what we already know is going on.

BM: I came out of the planetarium, and that evening, I sat thinking about what you said in the show about, you acknowledged the Big Bang and you, and I remember that Hubble rewound the process mathematically. Correct me if I'm wrong, and calculated that everything, matter, space, energy, even time itself, actually had a beginning.

NDT: So it turns out that was not Hubble, although Hubble had the data that enabled the calculation. The person who did that was a Belgian priest Georges LemaÃ®tre, he was a priest, physicist. Physicist-priest, okay?

What a cool thing to have on your business card. You got people coming and going with that. But he calculated what the implications of Einstein's general relativity, which was the new theory of gravity, would be with Hubble's expanding universe. And he says, the whole universe may have begun in a singular point in the past. And thus Big Bang as a phrase was used pejoratively of this idea, but it stuck.

BM: Well, the astronomer Robert Jastrow described it like the explosion of a cosmic hydrogen bomb. Not the explosion of a cosmic hydrogen bomb, but like the explosion of a cosmic hydrogen bomb.

NDT: Yeah, so there you're stuck with the analogy of the biggest explosion you know, using that to describe something that's even bigger. Which is hard to do, right? I mean, not to get morbid on you, but I was four blocks from the collapse of the World Trade Center towers. I live downtown. And I was trying to describe to others the sound of the collapse of 107-story building. And it is not like anything else. So I can say, "Well, imagine two trains colliding." But how many of us even have heard or seen that? Whatever that is, it's more than that. So you're stuck. If the biggest explosion we've made on Earth is the hydrogen bomb, and then you say it's a cosmic hydrogen bomb, it is, I think saying it's a cosmic hydrogen bomb cheapens the event. Yeah, it's way bigger than —

BM: I understand. An incredible flash of energy and light, though?

NDT: And matter and, yeah, all of this. All of the above.

BM: Do you give people who make this case, that that was the beginning and that there had to be something that provoked the beginning, do you give them an A at least for trying to reconcile faith and reason?

NDT: I don't think they're reconcilable.

BM: What do you mean?

NDT: Well, so let me say that differently. All efforts that have been invested by brilliant people of the past have failed at that exercise. They just fail. And so I don't, the track record is so poor that going forward, I have essentially zero confidence, near zero confidence, that there will be fruitful things to emerge from the effort to reconcile them. So, for example, if you knew nothing about science, and you read, say, the Bible, the Old Testament, which in Genesis, is an account of nature, that's what that is, and I said to you, give me your description of the natural world based only on this, you would say the world was created in six days, and that stars are just little points of light much lesser than the sun. And that in fact, they can fall out of the sky, right, because that's what happens during the Revelation.

You know, one of the signs that the second coming, is that the stars will fall out of the sky and land on Earth. To even write that means you don't know what those things are. You have no concept of what the actual universe is. So everybody who tried to make proclamations about the physical universe based on Bible passages got the wrong answer.

So what happened was, when science discovers things, and you want to stay religious, or you want to continue to believe that the Bible is unerring, what you would do is you would say, "Well, let me go back to the Bible and reinterpret it." Then you'd say things like, "Oh, well they didn't really mean that literally. They meant that figuratively."

So, this whole sort of reinterpretation of the, how figurative the poetic passages of the Bible are came after science showed that this is not how things unfolded. And so the educated religious people are perfectly fine with that. It's the fundamentalists who want to say that the Bible is the literally, literal truth of God, that and want to see the Bible as a science textbook, who are knocking on the science doors of the schools, trying to put that content in the science room. Enlightened religious people are not behaving that way. So saying that science is cool, we're good with that, and use the Bible for, to get your spiritual enlightenment and your emotional fulfillment.

BM: I have known serious religious people, not fundamentalists, who were scared when Carl Sagan opened his series with the words —

Carl Sagan, from "Cosmos": The cosmos is all that is or ever was or ever will be.

BM: I mean, that scared them, because they interpret that to mean, then if this is it, there's nothing else. No God and no life after.

NDT: For religious people, many people say, "Well, God is within you," or God, the, there are ways that people have shaped this, rather than, God is an old, grey-bearded man in the clouds. So if God is within you, what, I'm sure Carl would say, in you in your mind. In your mind, and we can measure the neurosynaptic firings when you have a religious experience.

We can tell you where that's happening, when it's happening, what you're feeling like at the time. So your mind of course is still within the cosmos.

BM: But do you have any sympathy for people who seem to feel, only feel safe in the vastness of the universe you describe in your show if they can infer a personal God who makes it more hospitable to them, cares for them?

NDT: In this, what we tell ourselves is a free country, which means you should have freedom of thought, I don't care what you think. I just don't. Go think whatever you want. Go ahead. Think that there's one God, two Gods, ten Gods, or no Gods. That is what it means to live in a free country. The problem arises is if you have a religious philosophy that is not based on objective realities that you then want to put in a science classroom. Then I'm going to stand there and say, "No, I'm not going to allow you in the science classroom.” I'm not telling you what to think, I'm just telling you in the science class, “You're not doing science. This is not science. Keep it out." That's where I, that's when I stand up. Otherwise, go ahead. I'm not telling you how to think.

BM: I think you must realize that some people are going to go to your show at the planetarium and they're going to say, "Ah-hah! Those scientists have discovered God. Because God,” dark matter, “is what holds this universe together."

NDT: So is that a question?

BM: It's a statement. You know, you know they're going to say that —

NDT: So the history of discovery, particularly cosmic discovery, but discovery in general, scientific discovery, is one where at any given moment, there's a frontier. And there tends to be an urge for people, especially religious people, to assert that across that boundary, into the unknown lies the handiwork of God. This shows up a lot. Newton even said it. He had his laws of gravity and motion and he was explaining the moon and the planets, he was there. He doesn't mention God for any of that. And then he gets to the limits of what his equations can calculate. So, I don't, can't quite figure this out. Maybe God steps in and makes it right every now and then. That's where he invoked God.

And Ptolemy, he bet on the wrong horse, but he was a brilliant guy. He formulated the geocentric universe, with Earth in the middle. This is where we got epicycles and all this machinations of the heavens. But it was still a mystery to him. He looked up and uttered the following words, “when I trace at my pleasure the windings to and fro of the heavenly bodies,” these are the planets going through retrograde and back, the mysteries of the Earth, “when I trace at my pleasure the windings to and fro of the heavenly bodies, I no longer touch Earth with my feet. I stand in the presence of Zeus himself and take my fill of ambrosia.”

What he did was invoke, he didn't invoke Zeus to account for the rock that he's standing on or the air he's breathing. It was this point of mystery. And in gets invoked God. This, over time, has been described by philosophers as the God of the gaps. If that's how you, if that's where you're going to put your God in this world, then God is an ever-receding pocket of scientific ignorance.

If that's how you're going to invoke God. If God is the mystery of the universe, these mysteries, we're tackling these mysteries one by one. If you're going to stay religious at the end of the conversation, God has to mean more to you than just where science has yet to tread. So to the person who says, "Maybe dark matter is God," if the only reason why you're saying it is because it's a mystery, then get ready to have that undone.

BM: In the next and concluding part of my conversation with Neil deGrasse Tyson, we’ll talk about science and democracy.

NDT: You have not fully expressed your power as a voter until you have a scientific literacy in topics that matter for future political issues. This requires a level, a base level of science literacy that I don't think we have achieved yet.

BM: At our website, BillMoyers.com, there’s more about and from Neil deGrasse Tyson. I’ll see you there and I’ll see you here, next time.