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Origins: Series Overview

Journey back to the beginning of everything: the universe, Earth and life itself. Airing February 28, 2004 at 9 pm on PBS Aired February 28, 2004 on PBS

  • Originally aired 02.28.04

Program Description

Has the universe always existed? How did it become a place that could harbor life? What was the birth of our planet like? Are we alone, or are there alien worlds waiting to be discovered? NOVA presents some startling new answers in "Origins," a groundbreaking four-part NOVA miniseries hosted by dynamic astrophysicist Neil deGrasse Tyson, Director of the Hayden Planetarium at the American Museum of Natural History. Tyson leads viewers on a cosmic journey to the beginning of time and into the distant reaches of the universe, searching for life's first stirrings and its traces on other worlds.

Broadcast Credits

Hosted and Narrated by
Neil deGrasse Tyson
Produced and Directed by
(Earth is Born, How Life Began)
Alice Harper
Narration Written by
(Earth is Born, How Life Began)
Produced by
Joseph McMaster
Written, Produced and Directed by
(Where are the Aliens?)
Julia Cort and Larry Klein
Written, Produced and Directed by
(Back to the Beginning)
Thomas Levenson
Origins Executive Editor
Neil deGrasse Tyson
Origins Executive Producer
Thomas Levenson
Director of Photography
(Back to the Beginning)
Robert Elfstrom
Co-Producer
(Back to the Beginning)
Craig Ginsberg
Associate Producers
(Earth is Born, How Life Began)
Julie Crawford
Caroline Penry-Davey
Associate Producers
(Where are the Aliens?)
Anthony Manupelli
Sandra Haller
Edited by
(Earth is Born, How Life Began)
Stephanie Munroe
Louise Salkow
Edited by
(Where are the Aliens)
Harlan Reiniger
Edited by
(Back to the Beginning)
Simon Holland
Additional Editing by
(Where are the Aliens)
David Espar
Baby
(Earth is Born)
Joshua Pitts
Origins Project Manager
Marie Wiljanen
Origins Project Development
Larry Klein
Series Science Advisors
Alan Dressler
Sandra Faber
Writers
(Earth is Born, How Life Began)
Alice Harper
Nigel Henbest
North Pole Segment Directed by
(Earth is Born)
Mark Everest
Camera
(Earth is Born)
Mike Coles
Brian Dowley
Steve Albins
David Langan
Mike Spragg
Camera
(How Life Began)
Mike Coles
Brian Dowley
Steve Albins
David Langan
Colin Fox
Camera
(Where are the Aliens?)
Robert Elfstrom
Brian Dowley
Gordy Waterman
Stephen McCarthy
Greg Andracke
Music
(Earth is Born, How Life Began)
Rob Morsberger
Richard Atree
Music
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Rob Morsberger
Animation created by
(Earth is Born)
Edgeworx
4:2:2 Video
CO:DE Design
Tony Lee
Animation created by
(How Life Began)
Edgeworx
4:2:2 Video
CO:DE Design
Animation created by
(Where are the Aliens, Back to the Beginning)
Edgeworx
Special Effects
(Earth is Born, How Life Began)
David Barlow
Kathryn Johnson
Animation Supervisor for NOVA
John Bair
First Stars Simulation
(Back to the Beginning)
Tom Abel
Greg Bryan
Michael Norman
First Stars Visualization
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Ralf Kähler
Tom Abel
Still Animation
(Back to the Beginning)
Anna Davis
Set Designer
(How Life Began)
Debbie Cutler
Camera Assistants
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Jaimie Gramston
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Sound Recordists
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John Cameron
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Sound Recordists
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Tim Worth
Sound Recordists
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Sound Recordists
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Ray Daye
Doug Dunderdale
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William Barclay
Director of Archive Research
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Assistant Editors
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Hamilton Jones
Online Editor and Colorist
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Online Editor and Colorist
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Audio Mix
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John Jenkins
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Joseph McMaster is the Margret and Hans Rey/Curious George Producer.
(Earth is Born, How Life Began)
For Pioneer Film & TV
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Martin Mortimore
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Producer, Special Projects
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Coordinating Producer
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Senior Science Editor
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Managing Director
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Original MER Animation
Animation by Dan Maas, Maas Digital LLC
© 2002 Cornell University All rights reserved.
This work was performed for the Jet Propulsion Laboratory, California Institute of Technology, sponsored by the United States Government under Prime Contract #NAS7-1407 between the California Institute of Technology and NASA. Copyright and other rights in the design drawings of the Mars Exploration Rover are held by the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL). Use of the MER design has been provided to Cornell courtesy of NASA, JPL, and Caltech.
A Pioneer Film & TV production for NOVA/WGBH and Channel 4.
(Earth is Born, How Life Began)
A Thomas Levenson Productions and Unicorn Projects, Inc. production for WGBH/Boston.
The Day the Earth was Born, Creation © Channel Four Television Corporation MMII
Origins, Earth is Born © 2004 WGBH Educational Foundation
Origins, How Life Began © 2004 WGBH Educational Foundation
Origins, Where are the Aliens? © 2004 WGBH Educational Foundation
Origins, Back to the Beginning © 2004 WGBH Educational Foundation
All rights reserved
This material is based upon work supported by the National Science Foundation under Grant No. 9814643. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

IMAGE:

(space)
© WGBH Educational Foundation

Sources

Links

Origins Education Forum
origins.stsci.edu
The Space Telescope Science Institute, in association with NASA, offers this rich interactive site devoted to origins research. The site's articles and activities are especially geared towards teachers, students, and members of the general public looking for an online education in all things origins.

HubbleSite
hubblesite.org
At this Internet hub for the Hubble Space Telescope, check out the latest images from space or browse an extensive archive. Find out how Hubble works, read up on cutting-edge cosmological discoveries, and play interactive games.

SETI Institute
www.seti.org
The Search for Extraterrestrial Intelligence's Web site offers a wealth of information on the organization's projects and conferences and the SETI Radio network, which has been the basis of SETI's search for alien life since it was founded in 1984.

The Planetary Society
planetary.org/
The Planetary Society is a nongovernmental organization for space advocacy. On its extensive Web site, access the latest headlines, research findings, and general information on large bodies within our solar system.

Universe Forum
cfa-www.harvard.edu/seuforum
Harvard University's Center for Astrophysics maintains this site, which is filled with interesting information on the structure and evolution of the universe. The site is designed to appeal to students, teachers, and a general audience.

Astronomy Picture of the Day
apod.nasa.gov/apod/astropix.html
Each day the Goddard Space Flight Center displays a different stunning image from space along with a brief caption by an astronomer. Check out a "brain crater" on Mars, the colorful clouds of Rho Ophiuchi interstellar cloud, and more.

Evolution
www.pbs.org/wgbh/evolution
This companion Web site to PBS' 2001 miniseries examines the complex topic of evolution from a variety of angles and considers the effect of the idea of evolution on human society and culture. Visitors may watch clips from the film and participate in an array of topical online activities.

Tour the Solar System
www.pbs.org/wgbh/nova/space/tour-solar-system.html
Explore the planets, visit the moon, and gaze at the stars in this 3-D interactive model of the solar system.

Books

Origins: Fourteen Billion Years of Cosmic History
by Neil deGrasse Tyson and Donald Goldsmith. New York: Norton, 2004.

Cosmic Company: The Search for Life in the Universe
by Seth Shostak. Cambridge: Cambridge University Press, 2003.

Life on a Young Planet: The First Three Billion Years of Evolution on Earth
by Andrew H. Knoll. New Jersey: Princeton University Press, 2003.

Rare Earth: Why Complex Life is Uncommon in the Universe
by Peter Ward and Donald Brownlee. New York: Copernicus Books, 2003.

Hubble Vision: Astronomy With the Hubble Space Telescope
by Carolyn Collins Petersen and John C. Brandt. Cambridge: Cambridge University Press, 1998.

A Short History of Planet Earth: Mountains, Mammals, Fire and Ice
by J. D. MacDougall. New York: Wiley, 1998.

The Whole Shebang: A State-of-the-Universe(s) Report
by Timothy Ferris. New York: Simon & Schuster, 1998.

Are We Alone? The Philosophical Implications of the Discovery of Extraterrestrial Life
by Paul Davies. New York: Basic Books, 1995.

A Short History of the Universe
by Joseph Silk. New York: W.H. Freeman & Co., 1994.

The First Three Minutes: A Modern View of the Origin of the Universe
by Steven Weinberg. New York: Basic Books, 1993.

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Origins: Where Are the Aliens?

How common are habitable planets in our universe, and what would “ETs” look like if they existed? Airing February 29, 2004 at 9 pm on PBS Aired February 29, 2004 on PBS

Program Description

In "Origins: Where are the Aliens?," host astrophysicist Neil deGrasse Tyson explores such provocative questions as: would "ETs" resemble us or the creatures of science fiction? Are there "aliens" already amongst us on Planet Earth—brainy creatures whose intelligence is very different from our own? And are planets on which life can flourish rare or common in our universe?

Transcript

Origins: Where are the Aliens?

September 29, 2004

NEIL deGRASSE TYSON (Astrophysicist): A hellish, fiery wasteland, a molten planet hostile to life, yet somehow, amazingly, this is where we got our start. How? How did the universe, our planet, how did we ourselves come to be? How did the first sparks of life take hold here? Are we alone in the cosmos? Where did all the stars and galaxies come from? These questions are as ancient as human curiosity itself. And on "Origins", a four-part NOVA mini-series, we'll hunt for the answers. This search takes unexpected twists and turns. Imagine meteors delivering Earth's oceans from outer space. Descend into a toxic underworld where bizarre creatures hold clues to how life got its start. And picture the view when the newborn moon, 200,000 miles closer to Earth than today, loomed large in the night sky. This cosmic quest takes us back in time to within moments of the Big Bang itself and retraces the events that created us, this place we call home and perhaps life elsewhere in the cosmos. Coming up tonight, "Where Are the Aliens?"

GEOFF MARCY (University of California, Berkeley): I feel like I'm six years old when I say it. I, I feel almost embarrassed. I just want to know, "Are they out there?"

NEIL deGRASSE TYSON: And why do they always look so much like us?

JACK COHEN (University of Warwick, UK): When we look at these aliens, and they've got faces with two eyes and a nose and a mouth, they can't be aliens. They must have developed on Earth. They must share that same ancestor, or they wouldn't have faces like that.

NEIL deGRASSE TYSON: E.T. may not be like us, but new discoveries are fueling optimism that alien life really is out there.

GEOFF MARCY: We're finding new planets like crazy.

FRANK DRAKE (SETI Institute): Places where life can exist are far more extensive than we used to imagine.

NEIL deGRASSE TYSON: Consider this: just because a planet can support life, does that mean it will? Are we likely to encounter anything as, well, smart as you and me?

ANDY KNOLL (Harvard University): Intelligent life, like ourselves, it's just a snap in the full history of the planet.

NEIL deGRASSE TYSON: Have the aliens advanced this far? And if so, are any of them willing to communicate with us? NOVA is on the hunt for alien life on this episode of "Origins", right now.

Major funding for NOVA is provided by the Park Foundation, dedicated to education and quality television.

Science: it's given us the framework to help make wireless communications clear. Sprint is proud to support NOVA.

We see one small step on Mars. Microsoft is proud to sponsor NOVA for celebrating the potential in us all.

Major funding for "Origins" is provided by the National Science Foundation, America's investment in the future. Additional funding is provided by the NASA Office of Space Science, the Alfred P. Sloan Foundation to Enhance Public Understanding of Science and Technology, and the George D. Smith Fund.

Major funding for NOVA is also provided by the Corporation for Public Broadcasting and by PBS viewers like you. Thank you.

NEIL deGRASSE TYSON: Anyone who visits New York City will see all manner of different life forms. And you don't have to look far to realize that our planet is teeming with a diverse population of living creatures. And for centuries we've been asking ourselves, "How unusual is all this? What about the rest of the Universe? Is our little planet Earth the only place where the action is? Are we special?"

AMY MANNING (street interview): I find it hard to believe the fact that we're the only people in this universe.

OSCAR RAMIREZ (street interview): We're definitely not alone.

GLEN TAYLOR (street interview): This is not just one universe. You know what I'm saying?

ROBERT BURCK, AKA THE NAKED COWBOY (street interview): There's, like, a hundred thousand million galaxy, or galaxies, in the universe.

GLEN TAYLOR: There's trillions and billions of universes.

ROBERT BURCK: Whatever. The point is, it's inconceivable how big things are. To think that we're alone here is ridiculous.

NEIL deGRASSE TYSON: Many people are ready, even eager, to believe that we are not at all alone. And that's the view prevalent in lots of popular films and TV shows.

WILLIAM SHATNER (Clip from Star Trek): These are the voyages of the Starship Enterprise.

NEIL deGRASSE TYSON: It's an appealing fantasy. Star Trek, Star Wars, Men in Black, all portray a universe filled with a multitude of intelligent life forms.

TOMMY LEE JONES (Clip from Men in Black): Show us the merchandise or you're going to lose another head, dude.

NEIL deGRASSE TYSON: Sometimes they're friendly and sometimes they're not. Screenwriters have come up with some pretty interesting behaviors for their extraterrestrials, but they often ignore some basic principles of biology.

For example, in the film Alien, a human being plays host to a parasitic alien until it's ready to be born. This has long bothered biologist Jack Cohen.

JACK COHEN: Alien is not concerned with the biology. You can't have a creature living in your chest which is bigger than your heart, and you don't know it's there, and your immune system isn't turned on, particularly if it's never seen a human being before. It doesn't work biologically. But it works as a film, because you see the thing coming out of the chest...aaagh...and it's exactly what they want. It's a horror film.

SOLDIER (Clip from Starship Troopers): Incoming!

NEIL deGRASSE TYSON: Another classic horror image of extraterrestrials shows them as giant insects—the alien of choice for the film Starship Troopers—but according to the laws of physics, this kind of anatomy is impossible.

JACK COHEN: It's like bringing a mouse up to be the size of an elephant. Its little thin legs wouldn't take the weight, and they would break. You have to redesign. It's a lot easier to have a terrifying film with giant ants.

NEIL deGRASSE TYSON: As unscientific as the oversized insects of Starship Troopers are, at least they don't look like people. By far, most films, even the ones with huge special effects budgets, depict aliens that actually look like they evolved on Earth because they have faces that resemble ours.

Nearly all the vertebrates we see around us, humans included, have faces with two eyes, two nostrils, and a mouth below. This configuration came from a common ancestor who lived hundreds of millions of years ago.

JACK COHEN: Now, when we look at these aliens, and they've got faces with two eyes and a nose and a mouth, they can't be aliens. They must have developed on Earth. They must share that same ancestor, or they wouldn't have faces like that. We expect a living thing, a dog or a cat or even a fish, to have a face. Therefore, when we invent something for a film, we give it a face. And that really enables the people who are watching to get moved by it. Real aliens can't be like that.

NEIL deGRASSE TYSON: Real aliens? What are we talking about? UFO sightings and abductions that show up in tabloids?

SAMANTHA THOMPSON (street interview): I think they have traveled to this planet.

STEVEN BUSHMAN (street interview): They might have been here years ago, but they became extinct just like the dinosaur did.

CHARLES LOUIS MELTON (street interview): We've been visited. Those lights in the sky aren't all weather balloons.

NEIL deGRASSE TYSON: Hmmm. There are some people who believe that aliens are already among us, but there's no credible evidence. There's nothing in any of these stories that can't be explained in some other, more rational way. And of course, some people are just plumb crazy!

But is it crazy to believe that somewhere, beyond our planet, life has taken root? Many scientists would say it's not only possible but likely.

One of the believers is Frank Drake.

FRANK DRAKE: I first believed there was life beyond Earth when I was eight years old, not for any good reason, only because my father told me there were other planets something like the Earth out there. And to my young mind that meant places just like where I lived, with houses and streets and, in fact, creatures that look just like me, which was certainly wrong. But I believed!

NEIL deGRASSE TYSON: Drake's childhood dreams led him to a career in radio astronomy, and he soon began wondering whether somewhere among the stars, there might exist aliens who, like us, had mastered radio.

Ever since humans learned how to broadcast radio waves, we've been leaking them out into the cosmos. Everything from Duke Ellington to I Love Lucy to the speeches of world leaders is, thanks to our ingenuity, now traveling across space at the speed of light.

Drake reasoned that if aliens were transmitting radio signals of their own, we might be able to detect them. And so he created the first experiment for SETI, the Search for Extraterrestrial Intelligence.

For decades, SETI astronomers have been scanning the stars of the Milky Way Galaxy, searching for signs of advanced alien civilizations. Their goal is the ultimate prize in the life-finding game: someone out there we can talk to.

SETH SHOSTAK (SETI Institute): Nothing to do but sit here and wait for them to call. And on cue, they've called!

NEIL deGRASSE TYSON: SETI faces enormous challenges, not least of which is the sheer size of our galaxy. The Milky Way has hundreds of billions of stars, swirling in a giant spiral about a hundred thousand light years wide, that's 600 quadrillion miles. So what are the chances of finding intelligent aliens in all that real estate?

Early in his quest, Frank Drake came up with an equation to guide him.

FRANK DRAKE: Actually, I first invented the equation as the agenda for a meeting. It seemed pretty obvious. It was a meeting about life in space, and I asked the question, "What do we need to know about?" And I realized if you multiply them all together, you get the number N.

NEIL deGRASSE TYSON: The now-famous Drake Equation lists the different factors we'd need to know to predict "N," the number of intelligent, detectable civilizations in our own Milky Way galaxy. It includes factors like, "How many stars have planets?" And, "How often will life become intelligent?" And how long a technologically advanced civilization might last.

FRANK DRAKE: And if you put in scientists' judgment the most plausible values for the factors in this equation, N equals 10,000 detectable civilizations in our galaxy—10,000 intelligent civilizations, just in the Milky Way alone!

NEIL deGRASSE TYSON: That's Frank Drake's best bet, but it's far from conclusive. If you plug different values into the equation, then it's easy to come up with other results, anything from a billion civilizations all the way down to one: ours.

For a long time, the values for most of these terms were unknown. The Drake Equation was something of a list of mysteries, leaving the equation unsolvable. But in the last few years, our knowledge of cosmic origins has been growing exponentially, and we're on our way to solving at least some of these mysteries.

Take just one term in the Drake Equation: the percentage of stars—other suns—that have planets orbiting them. If alien life is anything like us, it needs some solid ground to call home, and so we want to know how many planets are out there.

Depending on who you talk to, our sun's got eight, maybe nine planets circling around, including Earth.

Until recently, we haven't been able to see any planets beyond our own solar system, none at all. The problem is planets in deep space are rendered practically invisible by the blinding light of their suns. That's the challenge for the handful of scientists trying to track them down.

The team of Paul Butler and Geoff Marcy started their quest in the 1980s with little more than their own enthusiasm.

GEOFF MARCY: We started off with virtually no money at all. The first proposal I wrote for a grant to fund our planet search was for $930 for the whole year.

PAUL BUTLER (Carnegie Institution of Washington): When Geoff and I started the planet search, back in the fall of 1986, at San Francisco State University, we were...to say we were "unknown" is to overstate it. We were sub-unknown.

NEIL deGRASSE TYSON: The young astronomers were banking on an experimental technique they believed could scope out planets by focusing on the stars they orbit.

GEOFF MARCY: As a planet orbits a star, the planet pulls gravitationally on the star, making the star wobble. You can tell a star has a planet, or more than one planet, just by the motion of the star, which ought to be stationary but wobbles due to the pull on it by the planet.

NEIL deGRASSE TYSON: The star's wobble, created by the gravity of orbiting planets, is so subtle, Marcy and Butler can't see it directly, so they use a special technique.

GEOFF MARCY: It's hard to detect this motion directly, so we thought we would use the Doppler Effect. As a star moves toward you, the light waves get compacted, and that means they get shifted toward bluer colors. And then, as the star wobbles away from you, the wavelengths of light get stretched out, and this is interpreted by the eyes as redder.

NEIL deGRASSE TYSON: Even using the Doppler Effect, the only planets we can infer would be ones with tremendous mass.

Marcy and Butler were confident they had the best method for hunting down big planets and hoped they'd be the first to succeed, when the unthinkable happened. A team of Swiss astronomers beat them to the punch. The first planet outside our solar system had been found, but by someone else.

Most astronomers were skeptical. Although the planet was massive like Jupiter, the Swiss discoverers claimed it orbited its star, 51 Pegasi, in only four days. This seemed impossible. Earth takes 365 days to orbit the sun. And Jupiter takes 12 years.

Marcy and Butler felt certain there must be some mistake.

PAUL BUTLER: Almost every year for the last 100 years somebody has claimed to have found the first extrasolar planet, and the one thing all those claims had in common was they were wrong.

GEOFF MARCY: And luckily, Paul Butler and I had telescope time the very next week. And we thought, "Well, we'll just go up and take data on this star, 51 Pegasi, and show that it probably doesn't really have a planet at all."

PAUL BUTLER: And when we got back and we analyzed all the data, we were stunned. We were stunned because their claim was right. There really was a Jupiter-like planet in a four-day orbit. We were stunned because this was the first legitimate, real planet ever discovered, and that furthermore that these planets could be much stranger, much more bizarre, than any theories that had ever been conjured before.

NEIL deGRASSE TYSON: Marcy and Butler had spent years looking for massive planets like Jupiter, far out from their stars with long, slow orbits. Now that they realized that big planets could make a complete orbit in a matter of days, they began to wonder: had they missed something?

The evidence for new planets might be buried in their old data, but to find it, they'd need hundreds of hours of computer time.

GEOFF MARCY: And we only had two little computers. So we ran around madly trying to borrow, and in some cases subverting, our colleagues and stealing their computers so that we could analyze all of this backlog of data.

NEIL deGRASSE TYSON: They worked furiously around the clock for weeks, re-crunching eight years of data.

PAUL BUTLER: I was literally in my office 24 hours a day for about six months, reducing data.

GEOFF MARCY: Some nights, you know, hardly sleeping at all, and just making sure the computers were all running. God forbid the computers should sit idle when we could've been finding planets with them.

NEIL deGRASSE TYSON: But the marathon was worth it.

GEOFF MARCY: Within a month and a half of the discovery of the planet around 51 Peg, we found two planets sitting in our own data, right there on our computers: the planet around 47 Ursae Majoris—spectacular—and then the other planet around 70 Virginis.

NEIL deGRASSE TYSON: Planets were finally being found, but they were huge gas monsters, circling close to their stars, often in highly elliptical orbits. Scorching hot or with unstable climates, they were friendly to neither life nor other Earthlike planets.

GEOFF MARCY: Any poor Earth that got in the way would be slammed to death. I mean, a little Earth anywhere nearby a Jupiter would get slingshot out of the system, or maybe the Jupiter would hit that Earth and probably spell doom for any life on any terrestrial planets in those systems. And it really begs the question, "Is our solar system with its nice neat, phonograph groove-like orbits, some kind of wacky weirdo in the universe or are there others like ours?"

NEIL deGRASSE TYSON: In addition to its neat, round orbits, our solar system provides particular shelter for Earth, thanks to the presence and position of Jupiter. Jupiter's enormous gravity throws asteroids and comets off course, slingshotting them out of the solar system. Without this protection, these cosmic missiles would frequently smash into Earth and destroy life as we know it.

So, if Marcy and Butler want to find Earthlike planets, first they need to find Jupiters more like our own.

GEOFF MARCY: The Holy Grail, for us, is to find a sunlike star that has a Jupiter as far from it as our own Jupiter is from the sun. That Jupiter would protect any Earths that were in there. And of course the real super Holy Grail is to find a system that has, not only such a Jupiter, but also the Earth itself.

NEIL deGRASSE TYSON: After almost twenty years of searching, things are looking up.

GEOFF MARCY: We're finding new planets like crazy, all the time. Every week or two we find another new one, on average.

PAUL BUTLER: Lookie at that one. That's a beauty. Let's see how that corrects up. That's a planet.

We have about 700 stars on our program, and I'd say the thing that's really most amazing to us is how many of them appeared, like they have planetary signals imbedded in them.

NEIL deGRASSE TYSON: The team is tracking several stars that appear to have Jupiters right where they want them, far out from their host stars and in perfect position to shield life-friendly planets like Earth.

GEOFF MARCY: We're always following some exciting Jupiters. We don't tell anybody about them, but at any given time we have a half a dozen Jupiters that look like our own Jupiter.

NEIL deGRASSE TYSON: If their hunches are confirmed, then not only are there other solar systems that look like ours, there may be lots of them.

GEOFF MARCY: Ninety percent of the stars show no close-in Jupiters. Those are stars that could easily have an Earth in an Earth-like orbit. I think of the 700 stars we're following, I would bet at least half of them have rocky Earth-sized planets going around them.

NEIL deGRASSE TYSON: Just a decade ago astronomers could not be sure if there were any planets beyond our solar system. Today, we have a much better picture of our galaxy. And Geoff Marcy estimates that of the several hundred billion stars in the Milky Way, about five percent have small, rocky planets that might harbor life. If he's right, that could mean 10 billion Earthlike planets.

But before you start packing your bags to visit an extraterrestrial neighbor, consider this: just because a planet can support life, does that mean it will?

It's a crucial factor in the Drake Equation: the percentage of planets where life does arise. On a planet where no life exists, like our own early Earth, how does life suddenly come into being? Is the spark of life rare or common?

ANDY KNOLL: Twenty-five years ago, most people, when they thought about the origin of life, thought in terms of inherently improbable reactions that would actually occur because of the fullness of time.

NEIL deGRASSE TYSON: Andy Knoll is a paleontologist who studies fossils for clues to how early life evolved on Earth.

Before about 600 million years ago, all life on earth was tiny, single-celled creatures, so small that Knoll and his colleagues do most of their work with microscopes or in chemistry labs. The big surprise is that no matter where they look for signs of ancient life, they find it.

ANDY KNOLL: Our planet is about four and a half billion years old. We have evidence from the oldest rocks that we know of, at least the oldest sedimentary rocks we know of, that by about 3.8 billion years ago, life had already gained a foothold on our planet.

NEIL deGRASSE TYSON: Scientists haven't figured out exactly how that first spark of life happened, but since it seems to have sparked early on, then maybe it isn't so hard.

ANDY KNOLL: Most people think that whether or not we understand what the chemistry that leads to life is, that it's a chemistry that under the right conditions will pretty much go and...and is a fairly probable chemistry, and that therefore, life doesn't take billions of years to unfold on a planet. It might unfold in thousands of years or a million years. A lot of people think if you can't do it in a million years, you probably can't do it at all.

NEIL deGRASSE TYSON: So, what is required to get it all started? Here on Earth, the chemistry of life relies heavily on the element carbon. Carbon is one of the most versatile elements, each carbon atom can hook up with one, two, or three or four other atoms. It can even link up with other carbon atoms creating long chains or rings. Throw in a few other elements, and you've got amino acids, the ingredients of proteins, the building blocks of life as we know it.

JACK COHEN: Carbon is a very useful element to sit at the center of life's chemistry. There's a lot of it in the universe. It's made very easily in stars. It makes very complicated, meshed-together compounds which have the possibility of changing each other's properties. You can have a really complicated, complex setup with carbon. I'd expect that very nearly all life forms we come across that are matter-based are going to be carbon-based.

NEIL deGRASSE TYSON: If carbon helps make life happen, then there might be a lot of life out there. Carbon is one of the most common elements in the universe. So if it's got carbon, what else does life need? Lots of oxygen in the air? Seventy-two degrees? We tend to think life belongs in a place that's, well, comfortable for us. But is that really true?

In the last few years, we've been finding life practically everywhere on Earth, and not just the obvious spots. Microbes are thriving under rocks in the driest, hottest deserts. Life's doing just fine in the dark bottom of the oceans, warmed by deep sea vents. And now, life is turning up in some of the coldest, bleakest conditions imaginable, including the ice sheets of Antarctica and Greenland.

So now that we've found life not just surviving, but thriving just about everywhere on Earth, suddenly it's looking more likely that life might thrive in lots of places beyond Earth, even if we would find them a bit uncomfortable.

If life is common, then we should be able to find signs of it beyond our own little planet. Unfortunately, the evidence has been elusive. It's seems as if one crucial ingredient has been missing.

CHRIS McKAY (NASA Ames Research Center): The most important requirement for life is liquid water, and that's the defining requirement for life in terms of our solar system. There's plenty of energy, there's plenty of carbon, there's plenty of other elements on all the planets in our solar system. What's rare, and which, as far as we know, only occurs now on Earth, is liquid water.

NEIL deGRASSE TYSON: Liquid water is crucial because it's an ideal solvent. Molecules can easily move around in it and react with one another, allowing the complex chemistry of life to do its thing.

For years, it seemed that Earth, with its oceans of liquid water, was an oddball and perhaps the only, place in the solar system where life had ever thrived. Then we started to look more closely at our neighbors.

In recent years, NASA spacecraft have sent back images of Mars with stunning detail, and there are clear signs of a watery past.

CHRIS McKAY: From orbit around Mars we can see ancient rivers that are now dry, canyons which look like they had lakes in the middle of them, even what looks like an ancient ocean floor in the northern hemisphere. We see unmistakable signs that Mars was a wet place.

NEIL deGRASSE TYSON: And now there's even more information from NASA's twin rovers that roamed the Red Planet, taking pictures and probing the rocks for their chemical makeup. The photos reveal clear sedimentary layers in the Martian rocks, and chemical analysis shows they must have been laid down in the presence of water.

Mars might be too cold and dry to harbor life today, but if water was once there, then perhaps life was, too. And now, there's hope that life may thrive even farther out in the solar system.

CHRIS McKAY: I think Mars is the number one candidate for the search for life beyond the Earth, especially if we're going to find it soon. But we do have a backup plan, and in this case the back up plan is Europa, one of the moons of Jupiter.

A little smaller than our moon, Europa is covered with ice, but there are cracks in its surface, perhaps signs of ice sheets floating on a deep ocean of liquid water. What might be melting the ice is internal friction created by the gravity of Jupiter and its other moons. Europa's ocean is suddenly considered a potential home for life.

FRANK DRAKE: The places where life can live and exist are far more extensive than we used to imagine. We used to think a life-bearing planet would be just like the Earth, and a little closer to the sun it would be too hot, a little farther away it would be too cold. And now we realize, "Oh, gosh, there's a place which has an ocean with three times as much water as the ocean of Earth, and the water is warm." And that's way out in the solar system where we used to think the temperatures were ridiculously low; there could never be life there. So the likelihood of life existing on planets in space has just gone up enormously.

NEIL deGRASSE TYSON: So, even though we've yet to find life elsewhere in the solar system or beyond, we're getting more optimistic that life may be widespread.

But if life is common in the galaxy, what kind of life would it be? Is it merely the kind of life we had here for about three billion years, microorganisms happily brewing away with nothing bigger or more interesting than bacteria? Or is it the complex plant and animal life we find in our oceans, of all shapes and sizes? Or could it be what SETI is banking on: intelligent life that builds cities, computers and radio transmitters?

We now know that the way we got to this, from something like this, was through evolution. Does that mean evolution would work the same way wherever life appears? Frank Drake thinks so.

FRANK DRAKE: Once you have life, evolution goes to work. Life is very opportunistic. It expands. It finds ways to survive. It finds ways to cope with changing environments. And in the process it becomes more intelligent, and in the long run you end up with something like us, exploiting technology to live in even more inhospitable habitats.

NEIL deGRASSE TYSON: Drake's optimism shows up in the estimates he's plugged into his own equation. His guess is that wherever life arises, it will evolve into intelligent life 10 percent of the time. Not quite inevitable, but a fairly common outcome.

It's hard to know how likely or common intelligence is, when it's shown up so recently in Earth's history.

ANDY KNOLL: So the short history goes like this: life early, but the familiar life that we think of, plants and animals, that is really a relatively recent development on this planet. And intelligent life, people like ourselves, technologically competent humans, that's just a snap in the full history of the planet.

NEIL deGRASSE TYSON: After about three billion years with only microscopic life, Earth finally became home to true plants and animals. And after another five or six hundred million years, we came along.

One of the major mechanisms for all these changes has been DNA, the long chain of molecules that carries the blue-print for every living thing. Every time a cell divides, its DNA makes a copy of itself, and in that copy, there are always some mistakes. Sometimes those mistakes result in an animal or plant that's more successful than its parents. It's these kinds of mistakes that have allowed the tree of life to branch out in so many directions, creating the great diversity we see on our planet.

So, if there's life on other planets does it have to have DNA?

JACK COHEN: Would aliens have DNA? Well, I would be surprised to find aliens with DNA as their heredity, because DNA is a useful molecule, it can replicate, it can do the mirror image bit, it can do the...It's a very useful trick, but other chemicals can do that, and I'd be surprised if aliens latched onto the same one that we did.

NEIL deGRASSE TYSON: To get from microbes to complex animals and intelligent life, you might not need DNA, but there's one ingredient that could be absolutely crucial for the evolution of intelligence, and it may be the rarest of all: time.

Some scientists say that the key to our evolution was Earth's long and relatively peaceful history.

Among them is paleontologist Peter Ward. In this big galaxy of ours—hundreds of billions of stars—surely earth is repeated many places, many times. Why not?

PETER WARD (University of Washington): Well, I think the question is, "How much time do we have?" For instance, we got to intelligent organisms on this planet after 500 million years of animal life. So you've got a long period of time. Now that doesn't say you couldn't get it sooner at other places, but you still need finite periods of time. And to me that is the major argument against there being intelligent civilizations. You can't go from a bacterium to an intelligence in a million years, maybe not even ten million years, probably not even in a hundred million years. How many other planets are going to have such long periods of time? Not many, I think.

NEIL deGRASSE TYSON: In the half a billion years when intelligence was evolving, Earth's plant and animal life might have been pushed back to square one, single-celled organisms, with one catastrophic event. At least a couple of times, we came pretty close.

This crater, about a mile across, was made by a meteor that plunged to Earth nearly 50,000 years ago. As violent as that event must have been, it was nothing compared with earlier catastrophes. Just ask the dinosaurs.

The dinosaurs ruled Earth for about a hundred and fifty million years. They had the size. They had the power. It seemed that nothing could stop them. Then, sixty-five million years ago, an asteroid about six miles across headed toward Earth. In the aftermath of a collision of epic proportions and widespread volcanic eruptions, as many as two thirds of all living species were wiped out. The big guys didn't stand a chance.

Among the survivors were little mammals, and with the dinosaurs conveniently out of the picture, they thrived. Over the eons, their descendents evolved into lots of different animals, including primates, including us. That's how we got our start.

But what if you turned back the clock? What if that asteroid had taken a slightly different course and missed Earth completely? Little mammals may never have gotten their chance because the dinosaurs could still be in charge today. And instead of me, one of them would be hosting this show!

DINOSAUR (animation): Thank you, thank you very much!

NEIL deGRASSE TYSON: In some ways, we owe our existence to serendipity, and some argue that this makes the evolution of intelligence far less likely. Our brains evolved through many stages: the little rodents, the early primates, and later on we branched from the apes.

This worked for us, but is it the only route to intelligence? Would an alien species have to go through the same steps? There's no way to know for sure, but on our planet, lots of animals have remarkable brains and behavior, including some that are very distant from us on the evolutionary tree. Among them are the cephalopods, including octopus, squid and cuttlefish.

ROGER HANLON (Marine Biological Laboratory): Cephalopods are mollusks. They're related to clams and oysters, but they don't look much like them at all. And in evolutionary terms, they've evolved in a very different way.

NEIL deGRASSE TYSON: Roger Hanlon has spent the last 30 years studying the behavior of these animals, behavior that is their main defense from ending up as dinner.

ROGER HANLON: These animals are a yummy hunk of protein swimming around in the ocean, and once they're caught, they have no defenses. So they have to have a good primary defense. That's camouflage: don't be seen.

NEIL deGRASSE TYSON: In the lab, Hanlon and his team study how cephalopods, like this cuttlefish, control and change their skin patterns.

ROGER HANLON: It's taking that visual information and translating it to the skin on the back.

This is beautiful. Look at that perfect white square.

NEIL deGRASSE TYSON: To see how they apply their tricks in their natural habitat, Hanlon tails them with his underwater camera. His biggest challenge? Finding them in the first place. Octopus and cuttlefish have an uncanny ability to completely disappear into the background.

ROGER HANLON: We all think of the chameleon as sort of the king or queen of color change, but that's not true. A cephalopod can show many more patterns and can show them instantaneously. An octopus can be so camouflaged you literally cannot see it. So every place they go, they are morphing into something that looks a lot like that environment.

So here's the scene. You've got a rock with algae all over it. There appears to be nothing there except the swimming fish going by. Okay, so take a look here and just watch for a moment.

There it is. Whoa! Isn't that amazing? This animal was completely camouflaged on that rock, and suddenly it was there.

This remarkable camouflage, changing both pattern and three-dimensional texture, is performed by skin unlike any other animal's. It's an amazing skin, because there are up to 20 million of these chromatofore pigment cells, and to control 20 million of anything is going to take a lot of processing power. We call it a computer. Animals have brains. These animals have extraordinarily large, complicated brains to make all this work.

NEIL deGRASSE TYSON: For Hanlon, the brains and sophisticated behavior of these animals suggest that there's more than just one way to get smart.

ROGER HANLON: Even an invertebrate animal related to a clam or a snail can develop an incredibly complicated brain. This is one of the true wonders of nature. It's hard to explain why, but it's everywhere. And what does this mean about the universe and other intelligent life? The building blocks are potentially there and complexity will arise. Evolution is the force that's pushing that. I would expect, personally, a lot of diversity and a lot of complicated structures. It may not look like us, but my personal view is that there is intelligent life out there.

NEIL deGRASSE TYSON: But intelligent life is not necessarily life we can talk to across the depths of space. For that, you need technology. As smart as an octopus or a dolphin is, neither one of them is going to build a radio transmitter or a space ship.

When paleontologist Peter Ward looks at Earth's track record, the odds for technological aliens don't seem very promising.

PETER WARD: There's maybe 30 million species on the planet today. And if we look at the fossils, there's hundreds of millions of species in the past, but only one of them which has risen to technology. It's happened one time out of hundreds of millions of possibilities on planet Earth—one time, one time only. So, that's an astronomically small number.

NEIL deGRASSE TYSON: Here on Earth, we are the only species that has mastered technology. Since it's so rare here, should we really expect technology to be common among the aliens? Many would say "no," but the folks at SETI continue to hope.

Searching for alien signals night after night can test anyone's patience, unless, of course, you find one. Most evenings SETI will get a false alarm or two, but one night in 1997, they received a signal so strong and true, it looked as if their long search might be over.

SETH SHOSTAK: We were observing at another telescope in West Virginia, and we got this signal that started to pass all the automated tests that we use to determine is it really extraterrestrial, is it just more interference?

NEIL deGRASSE TYSON: The lead astronomer that evening was SETI director, Jill Tarter. Following standard procedure, she pointed the receiving dish away from the star where the signal appeared to originate: if the signal remained, it was just a stray transmission from Earth. But when they moved the dish, the signal went away. And when it was pointed back at the star, the signal returned. Excited, the SETI team repeated the test.

JILL TARTER (SETI Institute): We went off in another direction, and the signal went away. And we came back and it was there. And we went off in another direction, and the signal went away. And we came back and it was there. And it was now getting very interesting.

NEIL deGRASSE TYSON: Interesting because the signal might actually be coming from deep space. The excitement quickly spread back to SETI headquarters in Mountain View, California.

SETH SHOSTAK: I was back in Mountain View. We were watching the signals on remote monitors. Well, after about four or six hours of this, still passing the tests, needless to say, our blood pressure definitely was rising.

JILL TARTER: And I was so excited that exactly what I was looking for was right there, staring me in the face.

NEIL deGRASSE TYSON: By now the star had set. The next night would tell the tale. If the signal returned, perhaps E.T. was finally on the line.

SETH SHOSTAK: I, for one, couldn't sit down; I was sort of pacing around. A lot of people were huddled around the computers. Nobody went home. Nobody went out for a burger. In a sense, you know, it could have been an historic moment.

NEIL deGRASSE TYSON: The historic moment didn't survive the night. Most of the time, SETI used a second telescope, located in Georgia, to weed out false alarms. Unfortunately, the backup antenna wasn't working. So it took a little longer than usual for the SETI team to discover the truth on their own: the signal was coming from a distant research satellite. The champagne remained unpopped.

Despite the disappointment, SETI has never lost faith. Its scientists remain convinced that our universe is capable of producing intelligent life on many different worlds.

FRANK DRAKE: I truly believe there are signals out there. I also recognize full well that our instruments, as powerful as they are, are hardly beginning the search. The number of stars we've looked at, the number of radio frequencies, is minuscule compared to the total inventory of combinations of stars and frequencies there are to search. So we've hardly started. We should not have succeeded. Only through a great fluke of good luck would we have succeeded by now.

NEIL deGRASSE TYSON: Humans have been leaking radio waves into space for most of the past century. Compared to the history of our Milky Way galaxy, about 10 billion years, that's a tiny blip. And we've been actively listening for the radio signals from distant civilizations for only about 40 years.

If the aliens are on the other side of the galaxy, any signal they send could take tens of thousands of years to reach Earth. It's as if the aliens were throwing a dart and trying to hit one tiny spot on this enormous landscape of time and space. Let's face it, the odds of our capturing that signal aren't very good.

And yet, who can blame us for trying?

JILL TARTER: For me, it's the most interesting question. Are we alone? What's our place in this universe? How do we fit in? Are we just run of the mill? Are we totally exceptional? Or are we somewhere in between?

NEIL deGRASSE TYSON: Exploring our own world and the universe beyond has been full of surprises. Just a few hundred years ago, we assumed that everything about us and our surroundings was special and unique. Now we know there are lots of stars out there; many like our sun. We're discovering other solar systems with planets.

And the chemicals of life, forged in stars, are abundant in the universe. If those common chemicals have caught the spark of life somewhere else, who knows how that life will evolve, what path it will follow, and whether we'll ever meet?

GEOFF MARCY: I feel like I'm six years old when I say it. I feel almost embarrassed. I just want to know, "Are they out there?" And all of my science training, and math and skills as a researcher kind of go out the door. I just feel that this is a question that is going to be so profound for us as a species, but also individually. Each one of us will have to look within ourselves and figure out what it means to us.

NEIL deGRASSE TYSON: Are we alone? Are we rare? Are we common? We still don't know. But perhaps someday we will. And the answer, whatever it is, will reshape our sense of ourselves and our place in the universe.

The "Origins" series continues online. On NOVA's Web site, explore the arguments for and against intelligent life in the Milky Way galaxy. Then cast your vote. Find it on pbs.org.

To order this program on VHS or DVD, or the book, Origins: 14 Billion Years of Cosmic Evolution, please call 1-800-255-9424.

NOVA is a production of WGBH Boston. Major funding for NOVA is provided by the Park Foundation, dedicated to education and quality television.

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Major funding for "Origins" is provided by the National Science Foundation, America's investment in the future.

Additional funding is provided by the NASA Office of Space Science, the Alfred P. Sloan Foundation to enhance public understanding of science and technology, and the George D. Smith Fund.

Major Funding for NOVA is also provided by the Corporation for Public Broadcasting and by PBS viewers like you. Thank you.

Broadcast Credits

Origins: Where are the Aliens?

Hosted and Narrated by
Neil deGrasse Tyson
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© 2002 Cornell University All rights reserved.
This work was performed for the Jet Propulsion Laboratory, California Institute of Technology, sponsored by the United States Government under Prime Contract #NAS7-1407 between the California Institute of Technology and NASA. Copyright and other rights in the design drawings of the Mars Exploration Rover are held by the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL). Use of the MER design has been provided to Cornell courtesy of NASA, JPL, and Caltech.
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Origins: How Life Began

When and where did life gain a foothold on the early Earth, and how did it survive in such a hostile environment? Airing February 28, 2004 at 9 pm on PBS Aired February 28, 2004 on PBS

Program Description

"Origins: How Life Began," zeroes in on the mystery of exactly how it happened. Join the hunt for hardy microbes that flourish in the most unlikely places: inside rocks in a mine shaft two miles down, inside a cave dripping with acid as strong as a car battery's, and in noxious gas bubbles erupting from the Pacific ocean floor. The survival of these tough microorganisms suggests they may be related to the planet's first primitive life forms. Host astrophysicist Neil deGrasse Tyson deepens the search by investigating tantalizing and controversial chemical "signatures" of life inside three-billion-year-old rocks and meteorites found around the world.

Transcript

Origins: How Life Began

September 28, 2004

NEIL deGRASSE TYSON (Astrophysicist): A hellish, fiery wasteland, a molten planet hostile to life, yet somehow, amazingly, this is where we got our start. How? How did the universe, our planet, how did we ourselves come to be? How did the first sparks of life take hold here? Are we alone in the cosmos? Where did all the stars and galaxies come from? These questions are as ancient as human curiosity itself. And on "Origins", a four-part NOVA mini-series, we'll hunt for the answers. This search takes unexpected twists and turns. Imagine meteors delivering Earth's oceans from outer space. Descend into a toxic underworld where bizarre creatures hold clues to how life got its start. And picture the view when the newborn moon, 200,000 miles closer to Earth than today, loomed large in the night sky. This cosmic quest takes us back in time to within moments of the Big Bang itself and retraces the events that created us, this place we call home and perhaps life elsewhere in the cosmos. Coming up tonight: the origins of life.

MICHAEL MUMMA (NASA Goddard Space Flight Center): The early Earth was not a Garden of Eden. There were no clear blue oceans, there were no plants. There was no life at all.

NEIL deGRASSE TYSON: So where could the building blocks of life have come from?

We think that all the carbon in your body arrived on the Earth in meteorites like this. So it makes you wonder: if the building blocks of life were delivered courtesy of comets and meteors, could any of the tiny ingredients they carry have survived the landing? And if they did, how did they generate those first traces of life? A walk on the ancient surface of the Earth offers clues.

These are the oldest fossils in the world, at about 3.5 billion years old. Life evolved on this planet very early and very fast. Journey back to an age when invisible microbes ruled the planet and caused the greatest transformation in Earth's history.

Over a billion or two billion years, the amount of oxygen that these little creatures produced was enough to actually change the entire atmosphere of the planet.

The story of how life began, on this episode of "Origins", on NOVA, right now.

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NEIL deGRASSE TYSON: In the endless reaches of the universe Earth seems unique. It's a planet shaped and molded by life, a planet that six billion people call home today.

But when it was born, some 4.5 billion years ago, Earth was a violent place, so hostile it's hard to believe life could ever begin here. Covered in lava, and smothered in noxious gases, Earth was a planet under siege.

PENNY BOSTON (New Mexico Institute of Mining and Technology): If you were a human, going back into time, and trying to stand on the early Earth, it would be just like visiting a planet that was not your own.

LISA PRATT (Indiana University): This was a hazardous world, no doubt about that. If you were located in the wrong place at the wrong moment, you were simply vaporized.

NEIL deGRASSE TYSON: It was a planet plagued by catastrophe. If you condense all of Earth's history to just 24 hours, then only minutes after it formed, the entire globe melted and reformed. Then, to make matters worse, another planet about the size of Mars slammed into Earth, a cataclysm that created our moon. But soon after these disastrous beginnings, the most radical transformation of all time hit the planet: the origin of life.

So how did life begin? Well, over the years, people have come up with some pretty creative answers to this question. One of my favorites comes from a 17th century scientist who wrote down a recipe for creating life from scratch.

Let's see, it says here, "Take a dirty garment, place it in a vessel. Next add wheat." Then, according to the recipe, after fermenting for 21 days, mice will appear fully formed.

Of course, we all know that life doesn't form this way. But at some point in the Earth's early years, life did emerge out of non-living ingredients. And for clues to the real recipe of life, we have to go back some four billion years to a time when Earth was nothing like the planet we know today.

MICHAEL MUMMA: When we think of early Earth we must recognize it was not a Garden of Eden. There were no clear blue oceans, there was no clear water, there were no plants. There was no life at all.

NEIL deGRASSE TYSON: The young sun was weaker than it is today. And its light barely penetrated the atmosphere of carbon dioxide spiked with the pungent fumes of hydrogen sulfide.

STEPHEN MOJZSIS (University of Colorado): Since the atmosphere was thicker and dominated by CO2, the Earth had a reddish tinge to it. It didn't have the familiar blue sky. The oceans would have had an olive green color rather than our familiar blue color.

NEIL deGRASSE TYSON: For about the first 600 million years, comets and asteroids pounded our planet, a time known as the "Heavy Bombardment."

These interplanetary missiles measured up to 300 miles across. Their impacts vaporized Earth's oceans and melted its crust. With its extreme temperatures and toxic rain, seemingly nothing could survive here. But we now think that in this hellish environment, life first took hold. And today, hidden away in remote corners of our planet, conditions that in some ways resemble the extremes of early Earth can still be found.

Penny Boston and Diana Northrup are microbiologists on an expedition to investigate how life can survive in those harsh surroundings.

Buried in the depths of this tropical rainforest is a cave called Cueva de Villa Luz. Located in southern Mexico, it's an underground world laced with hydrogen sulfide, a foul-smelling gas that was present on Earth some four billion years ago.

PENNY BOSTON:These relic, or antique environments like Cueva de Villa Luz offer the same kinds of environments that we would have found on early Earth, and we're hoping to get clues to work backwards from those.

As you approach the cave you begin to get these faint whiffs of the rotten egg smell. And as you get closer this becomes more intense.

NEIL deGRASSE TYSON: Hydrogen sulfide is can be extremely poisonous, so the scientists have to wear gas masks inside the cave and carefully test them for leaks.

PENNY BOSTON:Have you got everything in there? I think I got everything.

At the levels at which humans can't live very long in hydrogen sulfide you don't smell it at all. It will just simply cause you to go unconscious and die very quickly.

NEIL deGRASSE TYSON: But can any other forms of life survive in the deep recesses of the cave so toxic to humans? Here, hydrogen sulfide, an invisible gas, escapes from the underground springs, reacts with oxygen in the water, and coats the cave with sulfuric acid.

PENNY BOSTON:The longer it sits there on the walls, the more acid it becomes. And so, eventually, by the time the drop is falling on you it's a very, very acid environment.

It's very fatiguing, and even with the protective masks that we have, we pick up loads of toxic gas through our skin and perhaps through tiny leaks.

Look at those stalactites to your left.

NEIL deGRASSE TYSON: Amazingly, despite the extreme conditions, it appears that life is thriving inside the cave. It comes in a strange package: colonies of single-celled bacteria that form slimy drips scientists call "snottites."

PENNY BOSTON:The snottites are drippy, gooey, mucusy formations that look like stalactites. And that's why they were called snottites, because they resemble strings of snot. We believe that the snotty, gooey stuff is to protect them against extreme acidity because when we measure the drips on the snottites, they are as extreme as battery acid. And so, while we find that daunting, this is where they thrive.

NEIL deGRASSE TYSON: Bacteria are among the most primitive and most common organisms on Earth. Like all forms of life, they grow, adapt to their environment, and reproduce. Inside each single-celled bacterium is a molecule of DNA, the code of life which allows them to multiply. There are millions of bacteria in each snottite.

And down in the underground streams, Penny Boston has found different kinds of bacteria in slimy clumps she calls "phlegm balls."

In fact, the cave is home to a huge number of bacterial colonies. And astonishingly, instead of being poisoned by the hydrogen sulfide, these bacteria depend on it for their survival.

PENNY BOSTON:They take the hydrogen sulfide and they get chemical energy out of it. It doesn't poison them. It's home sweet home for them, and this is a pretty new finding for these organisms.

NEIL deGRASSE TYSON: Conditions on early Earth may have been far worse, but these bacteria suggest that primitive life could have thrived in extremely hostile environments.

But where did the very first life come from? For more than a century, scientists have known that life is the result of chemistry, the combination of just the right ingredients in just the right amounts. Today, we know these ingredients aren't things like dirty garments and wheat, which people used to think would spontaneously generate mice. The ingredients of life are actually much simpler.

All living things, from bacteria to mice to you and me, are made from a small set of chemical elements: hydrogen, oxygen, carbon, nitrogen—four of the most common elements in the universe. Combined in just the right way, these are the fundamental ingredients of life, and carbon is the star of the show.

LISA PRATT:Carbon's everywhere. It's all over the universe.

ANDY KNOLL (Harvard University): What makes carbon special is the kind of bonds that it makes, both with itself and with other elements.

LISA PRATT:We know of no other atom that has the flexibility that carbon has to form diverse types of compounds.

NEIL deGRASSE TYSON: And the idea that life could have started when carbon and other ingredients combined in the harsh conditions of early Earth was first put to the test in the 1950s by a young graduate student named Stanley Miller. To simulate the newborn Earth in the lab, Miller assembled a contraption made out of flasks and tubes. He filled one flask with gases thought at the time to represent Earth's primitive atmosphere, and he connected that to another flask with water to represent the oceans.

ANDY KNOLL:And then he did a brilliant thing. He simply put an electric charge through that to essentially simulate lightning going through an early atmosphere. And after sitting around for a couple of days, all of a sudden there was all this brown goo all over the reaction vessel, and when he analyzed what was in the vessel now, he actually had amino acids.

NEIL deGRASSE TYSON: Amino acids are compounds that form when molecules of carbon and other elements link together. They are the essential building blocks of proteins and cells, vital ingredients of all living things.

Stanley Miller's experiment was headline news and jump-started the scientific search for the origins of life.

ANDY KNOLL:Life is really chemistry; there's no question about that. In fact, it's a chemistry that, when you get the recipe right, it goes, and it goes fairly quickly.

NEIL deGRASSE TYSON: That recipe is hotly debated today, and most scientists think the environmental conditions on early Earth were very different from the ones Miller simulated in his lab. And another debate rages about when this recipe first got cooked up.

On our 24-hour clock, the barrage of asteroids and comets lasted from about midnight until almost 3:30 in the morning. The assault then weakened, but continued for more than 100 million years.

It's hard to believe that life could have gained a foothold during this unstable period, but new discoveries reveal that life may have existed as early as four in the morning, or about 3.8 billion years ago.

The evidence comes from some of the oldest rocks on the planet, found in the remote regions of West Greenland.

STEPHEN MOJZSIS: The geology of Greenland is unique. It contains a record of some of the earliest geological processes that we know of on the Earth. The rocks themselves are thought to be between 3.7 and 3.9 billion years in age.

NEIL deGRASSE TYSON: These rocks are so old that any fossils they once contained have been destroyed. So to find out if life existed when they formed, Mojzsis had to look for evidence that is far more elusive.

STEPHEN MOJZSIS: There may have at one time been small fossils, microfossils but under the conditions of heat and pressure that these rocks experienced, such fossils would have been disaggregated and destroyed. So what we have left behind then are chemical fingerprints of ancient bacteria or microbes.

NEIL deGRASSE TYSON: To search for those fingerprints, Mojzsis first extracts a sample from the ancient Greenland rocks. Then he will analyze its chemical composition looking for carbon, a signature of life.

But carbon comes in several different forms. And Mojzsis wants to know if the carbon in this sample is the kind left behind by living creatures. If so, he believes that life may have existed when these rocks formed over 3.8 billion years ago, a controversial claim.

STEPHEN MOJZSIS: It was a surprise for us to find evidence of ancient life in these rocks. We didn't know if it would be there. You know, just because the stage is set doesn't mean that the actors are present. But these samples, here, represent the first evidence we have, direct evidence of a biosphere on our planet.

NEIL deGRASSE TYSON: If it emerged so early, life was lucky to miss the greatest cataclysm of all time, an impact like no other in our planet's history. It happened when another rocky sphere about the size of Mars collided with Earth. The outer layers of our planet were vaporized, and the debris from this collision coalesced to form the moon. That impact was so powerful that any building blocks of life that existed on Earth would have been destroyed.

This gives rise to speculation that the ingredients of life didn't form on Earth at all, but arrived special delivery, from outer space.

Hollywood has always been taken with the idea that life came from outer space. But it's not as far-fetched as it might sound.

STEPHEN MOJZSIS: Space is not very far away. Space is only about 20 kilometers that way. Now, that's very close and space is vast.

NEIL deGRASSE TYSON: And a scientist named Don Brownlee designed an experiment to find out if space might actually harbor the building blocks of life.

DON BROWNLEE (University of Washington): There are 40,000 tons of bits of comets and asteroids that impact the Earth every year. This is mostly in the form of particles that are less than a millimeter in size. We breathe them, they're in the food that we eat, but they are very difficult to find. You can only find them in very special places.

NEIL deGRASSE TYSON: To see if this shower of space-dust contains the ingredients for life, Brownlee needed to obtain samples uncontaminated by Earth's atmosphere. So to get just a few micrograms of dust, he commissioned a former spy plane to fly close to the edge of Earth's atmosphere. Sticky pads on the plane's wings collected the space dust. Then, Brownlee's colleagues sliced the dust particles into slivers less than one-tenth the thickness of a human hair. And they discovered that these tiny particles are rich in the seeds of life.

DON BROWNLEE: If you look on an electron microscope, you'll see this wonderful array of minerals and carbon and organic materials that are 4.55 billion years old and we believe are the building blocks of life.

NEIL deGRASSE TYSON: And this extra-terrestrial dust isn't the only possible source of life's ingredients. In a region of space called the Asteroid Belt are huge amounts of debris left over from the formation of the solar system. And sometimes, chunks of debris containing metal and rock fall to Earth bearing surprising gifts.

One such meteorite landed in the town of Murchison, Australia, in 1969.

NEWSREEL ANNOUNCER: It's a gold mine, this little chunk of meteorite which fell on Australia last year. For the past six months they've been taking it apart and have discovered that it contains amino acids, the building blocks of life.

NEIL deGRASSE TYSON: It was the first time that complex organic compounds had ever been found in material from space. And if meteorites like it were common perhaps they had delivered vast quantities of the original constituents of life to early Earth.

MIKE ZOLENSKY (NASA Johnson Space Center): Enough organics are present here that we think that meteorites like this provided the early Earth its entire budget of organics. So all the organics in your body, all the carbon in your body and in your lunch you had today, arrived on the Earth in meteorites like this.

If they come through the atmosphere in large enough objects, they're like little capsules coming in the atmosphere. They break apart on the Earth's surface and deposit their cargo of organics.

NEIL deGRASSE TYSON: More than 70 kinds of amino acids have been found in meteorites, and many are the fundamental ingredients of proteins that make up living cells. During the Heavy Bombardment, millions of meteorites may have seeded the Earth with the stuff of life. And there might have been an even more efficient delivery system.

Comets are like giant dirty snowballs made of ice and rock. Some comets that hit the early Earth were the size of mountains, and a large portion of their mass could have contained organic compounds.

The destructive power of comets and meteors is astronomical. The meteor that slammed into Earth some 50,000 years ago, here in Arizona, blasted a hole in the ground nearly a mile wide—from here to here—and so deep it could hold a 60-story skyscraper. And as if that weren't enough, the force of the impact was so great that it instantly vaporized nearly the entire meteor, three hundred thousand tons of it.

So it makes you wonder: if the building blocks of life were delivered courtesy of comets and meteors, could any of the tiny ingredients they carried have survived the landing? And just what happens to things like amino acids when they slam into Earth with such devastating power?

To answer those questions, one scientist came up with an ingenious experiment. Using a huge gas-powered gun, Jennifer Blank simulates the extreme pressures and temperatures that are unleashed when a comet smashes into Earth.

JENNIFER BLANK (Lawrence Livermore National Laboratory): We set out to test whether or not materials would survive or whether they would break down. And we expected that, or we were hoping that, some fraction would survive. We figured the parts that didn't survive would break down into smaller components, but in fact what we found is much more exciting.

NEIL deGRASSE TYSON: The gun fires a bullet at 5,000 miles an hour towards a sample that represents the organic molecules inside a comet. The sample consists of a solution of five different amino acids, two of them present in every living cell. The mixture is inserted into a steel capsule. The gun will send a shockwave through the capsule simulating the extreme pressures of a comet's impact.

JENNIFER BLANK: I think it's very hard to just imagine what kinds of pressures we're generating in these experiments. If you think about going to the bottom of the ocean, the pressures you'll have there are only a hundred times atmosphere. So these are hundreds of thousands of times atmospheric pressures.

NEIL deGRASSE TYSON: Will Jennifer Blank's experiment show that the building blocks of life can survive a crash landing on Earth?

JENNIFER BLANK: Clear the room...Charging now...Okay, bringing up the X-rays...35. Three, two, one, fire. Three, two, one, fire.

NEIL deGRASSE TYSON: When they remove the capsule it's undamaged. But have its contents survived the impact?

The once clear solution of amino acids has turned a tarry brown color. And the analysis revealed that not only had the material withstood the colossal pressure of the impact, but it had transformed into a new compound.

Amino acids, combinations of carbon and other basic elements, had fused together to form more complex molecules called peptides.

JENNIFER BLANK: We went from our initial small compounds—and here's an example of one of them, a simple amino acid—and we used the energy associated with the impact to build larger molecules. Molecules like this—this is a peptide—and we show that we can use the impact energy to grow larger molecules from the simplest building blocks of life.

NEIL deGRASSE TYSON: Peptides link together to form larger building blocks, proteins, which make up all the cells in our bodies. But the leap from non-living ingredients to a living creature, complete with DNA which allows cells to replicate, is staggeringly complex.

No one knows how this process started or what course it took.

ANDY KNOLL:It is hard to really get your head around the great leap from non-living to living.

LISA PRATT:Well, it's hard enough that nobody's succeeded in doing it in the laboratory.

ANDY KNOLL:I think it's an astonishing mystery, and one that we truly don't understand in any great detail.

NEIL deGRASSE TYSON: While we don't yet know how the spark of life occurred, we can try to figure out where it might have gotten a foothold.

And because the planet was under such devastating assault from comets and meteors, the leap to life may not have taken place up here on Earth's surface. To take hold, life may have needed a safe haven, perhaps underground.

A team of scientists descends into one of the deepest mines on Earth to investigate whether microbial life can survive far below the Earth's surface.

JAMES HALL (Carnegie Institution of Washington): And the mining environment gives us this fantastic window into the deep subsurface. It's a unique scenario because there is nowhere else on planet Earth that allows you to have access to that sort of sample location at two, three, three and a half kilometers deep.

NEIL deGRASSE TYSON: It takes 45 minutes to reach the heart of this South African mine. Conditions here are extremely uncomfortable, for humans, that is. The temperature of the rock is 120 degrees Fahrenheit, and the air pressure is twice that at Earth's surface.

Life down here survives entirely without sunlight. If they exist, microbes need to find a way to live in pitch darkness, drawing chemical energy from water and minerals trapped in the surrounding rocks.

JAMES HALL:Microorganisms have been shown potentially to be able to use these molecules to provide themselves with energy and support themselves completely independent of photosynthesis. And if we can prove that that is the case here, then that is very interesting because that adds credence to the idea that you could have life originating in the deep subsurface.

NEIL deGRASSE TYSON: As the miners drill into the rock, they break into ancient pockets of water, havens for microorganisms.

JAMES HALL:We're not sure how organisms can live in such extreme environments. The major thing is there's such low nutrient availability, there's nothing really for these guys to continually use and process to survive, and yet somehow they do. And the question is, "How do they do it?"

NEIL deGRASSE TYSON: The first step is to collect pristine samples of the water and see if they can grow the microbes it contains.

JAMES HALL:I'll get a very big sense of achievement if I can actually take something that's been isolated for 200 million years, put it in the laboratory and actually find out what it is this organism needs to survive.

NEIL deGRASSE TYSON: In a makeshift lab near the mine, the team attempts to recreate the environment deep inside the rock. And they have found that these microbes are dining on a variety of strange gases.

JAMES HALL:It turns out that in the deep subsurface there's an abundance of methane gas and ethane and propane. Now, for you and I that's not a very exciting diet, but what we think is that these organisms may be taking that kind of gas and actually using that as a food to survive.

NEIL deGRASSE TYSON: On such an exotic diet, the bacteria draw just enough energy to divide and reproduce only once every thousand years, suggesting a way that life could have survived deep beneath the surface of the early Earth.

And the Earth's crust may not have been the only place where life could have hidden from the Heavy Bombardment. Another safe haven may have been the ocean. Volcanic activity was intense on the early Earth. Chemicals from deep inside the planet spewed into the primitive seas. Even today, marine biologists have discovered volcanic vents on the ocean floor.

Despite scalding temperatures, acid eruptions and total lack of sunlight, they found creatures of all types thriving down here. And at the bottom of the food chain are microbes that live on the noxious hydrogen sulfide gas erupting from the vents.

On early Earth, primitive life may have survived in similar environments.

STEPHEN MOJZSIS: If all of the bombardment was occurring near the surface, survivors would be existing in just these kinds of hydrothermal vent communities where there's abundant water and nutrients and heat and food in the form of chemical energy. It has been found that organisms collected there nowadays are genetically akin to some of the earliest organisms that we think existed on the Earth.

NEIL deGRASSE TYSON: By about three and a half billion years ago, or five o'clock in the morning on our 24-hour clock, the bombardment of asteroids and comets had ceased. With far fewer violent impacts on Earth, microbial life could now survive outside its protective hiding places.

After it reaches Earth's surface, life would take advantage of another source of energy: the sun. Up here, microbes evolved a green pigment known as chlorophyll. This allowed them to trap sunlight and use it to drive a chemical reaction that converts carbon dioxide and water into food. Called "photosynthesis," it was a clever invention that enabled some bacteria to grow and reproduce almost without limit.

Once it started, photosynthesis was a runaway success, and today it's how all green plants make their living.

As Earth cooled, this new generation of cells spread across the oceans. Immense colonies of green slime would take over the world, kicking off the greatest transformation in our planet's history.

ANDY KNOLL:Photosynthesis is the great liberator of biology. With photosynthesis, the energy is coming from the sun, and life could spread, literally, over the entire planetary surface.

NEIL deGRASSE TYSON: And this remote corner of Western Australia holds clues to how that happened. These domed structures, called stromatolites, are built up layer by layer over thousands of years by tiny microbes. These microbes may be similar to life forms that dominated our planet billions of years earlier. And in the arid hills nearby, there may be evidence of these ancient creatures.

These rocks have remained unchanged for three and a half billion years. Here it's possible to walk on the surface of early Earth. Martin Van Kranendonk spends months at a time in this wilderness, studying the geology and producing maps. In a secret location in these hills is what could be one of the greatest geological discoveries of all time.

MARTIN VAN KRANENDONK (Geological Survey of Western Australia): These are the oldest fossils in the world, at about three and a half billion years old, and they're composed of stromatolites. And at this outcrop we can see two different types of structures that these creatures formed. First are these black mats that have wrinkly textures all through it, and the second are these larger domes that form these broad structures. The most likely way these things formed is by the growth of microbes.

NEIL deGRASSE TYSON: Like modern stromatolites, these ancient structures could also have been built by colonies of bacteria. And not far away are fossilized ripple marks which suggest they might have grown in shallow water.

MARTIN VAN KRANENDONK: And here, you can see we've got a smaller structure that we call the "Mickey Mouse Ears," which is this beautiful doubly branching structure. And there is nothing else that we can think of which would make that except something that was growing on the bottom of the ocean.

NEIL deGRASSE TYSON: So perhaps the ancient stromatolites were formed by microbes like the ones that build these structures today.

MARTIN VAN KRANENDONK: These big stromatolites are composed mostly of rock at the bottom, and the only living part of the stromatolite is a thin layer on top. And that thin layer on top is made up of microscopic blue-green bacteria called "cyanobacteria."

NEIL deGRASSE TYSON: Named after the blue-green color of their cells, these cyanobacteria use photosynthesis to collect energy from the sun. They secrete a sticky coating to shield them from ultraviolet radiation. As tiny pieces of dust and sediment settle on top of the sticky cells, the bacteria migrate closer to the surface to reach the light. The layers of sediment build up by about half a millimeter a year. These structures contain living microbes, just as they have for thousands of years.

MARTIN VAN KRANENDONK: The amazing thing about these stromatolites is that the microorganisms which build them are so tiny. And the structures that you see around me, compared to their size, are enormous. It'd be like if humans made a skyscraper that was a hundred and five kilometers high by seventy kilometers across. These are massive structures for the size of the organisms that make them.

NEIL deGRASSE TYSON: Many different shapes and sizes of what appear to be fossilized stromatolites have been found in the rock. It seems likely that these structures were formed by some type of microbe living on the early Earth, perhaps even by the ancestors of today's cyanobacteria.

MARTIN VAN KRANENDONK: We're looking at sort of a cross-section through the top of these cones. And layers that were laid down year after year, and the fact that they're all different sizes on this one surface, shows that there was a colony of microorganisms growing on this one bedding plane. And that's really fascinating because it means that life evolved on this planet very early and very fast.

NEIL deGRASSE TYSON: And it's the cyanobacteria that would bring about the most astounding changes in Earth's history, a change that could have started as early as three and a half billion years ago.

Over time, stromatolites spread out across the planet. As a byproduct of photosynthesis, the ancient bacteria produced a waste gas: oxygen. The oxygen was absorbed into the oceans at first. There, it combined with iron erupting from undersea volcanoes to form iron oxide particles that fell to the ocean floor. Over the next several hundred million years the planet literally rusted.

There may have been other forces at work, but eventually, all the iron was turned into oxide, building up layer after layer, one of the most valuable mineral deposits on Earth, iron ore.

Located in Western Australia, this is one of the world's largest iron mines. The iron here was originally deposited on the floor of a primordial ocean.

MINE CREW MEMBER: We are at the current position as connected. We will fire in 10 seconds with a five-second count down.

NEIL deGRASSE TYSON: Every week they excavate half a million tons of iron ore used to make steel for everything from cars to skyscrapers. In a more pristine state, thousands of ancient layers of iron ore are preserved in the Karijini Gorge, just 30 miles from the mine.

The layers exist because different amounts of iron oxide were deposited at different times of the year. Cyanobacteria produced oxygen in varying amounts as water temperatures changed with the seasons. All over the world, vast amounts of iron ore were laid down in similar ways.

On our day-long clock, this process continued until one in the afternoon.

Eventually, oxygen produced by cyanobacteria began to build up in the atmosphere. Slowly but surely this transformed the planet. Over the next eight hours or so, tiny microbes raised the level of oxygen from less than one percent to today's 21 percent. The time was about 9 p.m.

It's amazing to contemplate, but without cyanobacteria, there would be no oxygen and Earth would still be smothered in noxious gases. Plants, animals and humans would have never evolved.

ANDY KNOLL: We're sitting here today breathing an oxygen-rich mixture of air. We couldn't be here without that oxygen, but that oxygen wasn't present on the early Earth, and it only became present because of the activity of photosynthetic organisms.

PENNY BOSTON:Life has made this environment what we know. It's allowed us to live on the surface, it allows us to breathe, it allows large organisms like we are to function at very high rates of activity.

NEIL deGRASSE TYSON: The oxygen also helped protect life from the sun's lethal ultraviolet radiation, by creating a layer of ozone in the upper atmosphere.

PENNY BOSTON:One of the fascinating properties of that is that it actually screens out—just sort of like a sunscreen does on your skin—screens out this harmful radiation.

NEIL deGRASSE TYSON: With the protection of the ozone layer, life was able to diversify into more complex organisms. It took only the last three hours of the day for all the other life forms on our planet to evolve.

The first multicellular life emerged at six minutes past nine in the evening. Then came fish, and insects, and reptiles. By about 10 minutes to 11 in the evening, dinosaurs roamed the Earth. The first primates appeared at 20 to midnight. And with less than 30 seconds to go, the first humans made their appearance.

DON BROWNLEE: It's only been the last 10 percent of the Earth's history where there was life on the surface of the Earth that you would see with your naked eye. So, for most of Earth's history, life has basically been invisible on the Earth.

MARTIN VAN KRANENDONK: Over a billion or two billion years, the amount of oxygen that these little creatures produced was enough to actually change the entire atmosphere of the planet.

STEPHEN MOJZSIS: Multi-cellular life that we're most familiar with—animals, plants, their environment—was made possible by the slow, toilsome task of bacteria to oxygenate the atmosphere.

NEIL deGRASSE TYSON: Microbes ruled the planet for more than three billion years, two thirds of its history. These tiny organisms had transformed an entire planet. Without them, complex life, humans included, would have never evolved.

The "Origins" series continues online. On NOVA's Web site, explore the arguments for and against intelligent life in the Milky Way galax. Then cast your vote. Find it on PBS.org.

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Origins: How Life Began

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Origins: Earth Is Born

See the first billion years on Planet Earth—a time of continuous catastrophe, from volcanic eruptions to hot acid rain. Airing February 28, 2004 at 9 pm on PBS Aired February 28, 2004 on PBS

Program Description

"Origins: Earth is Born" gives viewers a spectacular glimpse of the tumultuous first billion years of Planet Earth—a time of continuous catastrophe. Vivid animation lets viewers witness the traumatic birth of the moon from a titanic collision between Earth and an object believed to have been the size of Mars. Bombarded by meteors and comets, rocked by massive volcanic eruptions, and scoured by hot acid rain, the early Earth seems a highly improbable place for life to have taken root. Despite such violent beginnings, scientists have found new clues that life-giving water and oxygen appeared on our planet much earlier than previously thought.

Transcript

Origins: Earth is Born

September 28, 2004

NEIL deGRASSE TYSON (Astrophysicist): A hellish, fiery wasteland, a molten planet hostile to life, yet somehow, amazingly, this is where we got our start. How? How did the universe, our planet, how did we ourselves come to be? How did the first sparks of life take hold here? Are we alone in the cosmos? Where did all the stars and galaxies come from? These questions are as ancient as human curiosity itself. And on "Origins", a four-part NOVA mini-series, we'll hunt for the answers. This search takes unexpected twists and turns. Imagine meteors delivering Earth's oceans from outer space. Descend into a toxic underworld where bizarre creatures hold clues to how life got its start. And picture the view when the newborn moon, 200,000 miles closer to Earth than today, loomed large in the night sky. This cosmic quest takes us back in time to within moments of the Big Bang itself and retraces the events that created us, this place we call home and perhaps life elsewhere in the cosmos. Coming up tonight: the beginnings of planet Earth.

MIKE ZOLENSKY (NASA Johnson Space Center): If you look under your bed, you'll find that little bits of dust are collecting together into large dust balls. And something like that must be what happened in the solar system, too.

NEIL deGRASSE TYSON: What started as a giant ball of debris floating in space turned into Earth, but four and a half billion years ago, it wasn't exactly home sweet home.

MIKE ZOLENSKY: The Earth, at some point, was totally molten, a big droplet of melt just floating in space.

NEIL deGRASSE TYSON: How did it change from a raging inferno like this to a place we all know and love? It seemed a series of massive disasters was the best thing to hit the infant planet.

BILL HARTMANN (The Planetary Science Institute): We all hear about the impact 65 million years ago that wiped out the dinosaurs. And you're getting that kind of impact something like once a month on the early Earth.

NEIL deGRASSE TYSON: And more clues are embedded within these rocks, fragments left over from the first hours of Earth's life.

STEPHEN MOJZSIS (University of Colorado): Very little is left behind from the Earth's earliest time period, but what is left behind has revealed to us a planet much more complicated than we ever thought.

NEIL deGRASSE TYSON: New discoveries rewrite the story of how our planet was born, on this episode of "Origins", on NOVA, right now.

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Major funding for "Origins" is provided by the National Science Foundation, America's investment in the future.

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NEIL deGRASSE TYSON: In its infancy, Earth was a primeval hell, a lifeless planet bombarded by massive asteroids and comets. The moon, much closer to Earth, loomed large in the sky. Instead of water, red hot lava streamed across the surface of our planet. Volcanoes spewed noxious gases into the primitive atmosphere. Scorched and battered, Earth was a planet under siege. Yet somehow, the world we call home emerged from these violent origins.

So how did Earth make such an astonishing transformation? How did it change from a raging inferno like this, to a place we all know and love, with firm ground under our feet, air we can breathe, and water covering nearly three quarters of its surface? A place where life could take hold and evolve into complex organisms like you and me?

Well, it turns out, Earth became a habitable planet only after a series of devastating disasters in its early years. And to see how this happened, let's imagine all of Earth's four-and-a-half-billion-year history condensed into a single day, just 24 hours on an ordinary clock or watch like this.

If we start right now, then the first humans walked the Earth only 30 seconds ago. Dinosaurs began roaming the planet just before 11 p.m. The first multi-celled animals evolved at 9:05. Before that, mostly single-celled organisms existed, and we think the first of those appeared around 4 o'clock on the morning.

Earth was born at midnight on this 24-hour clock, 4.5 billion years ago, but its violent history began well before that, when huge ancient stars that had reached the ends of their lives exploded. These supernovas cooked up all the chemical elements we know today including iron, carbon, gold and even radioactive elements like uranium. Over time, gravity took hold, and this cloud of stardust collapsed into an enormous rotating disk: the solar nebula.

In the center of this disk, temperature and pressure rose, and a star, our sun, was born. Eventually, gases like hydrogen and helium would be swept to the far reaches of the disk, but closer to the sun were dust grains made of the heavier elements.

MIKE ZOLENSKY: They're circling around the early sun in little racetracks, and occasionally grains traveling nearby will collide. Something like this happens in your house. If you look under your bed, you find that little bits of dust are collecting together into large dust balls. And something like that must be what happened in the solar system, too. If they collide slowly, they can add up to a larger object and gradually grow.

NEIL deGRASSE TYSON: With enough collisions, dust grew into pebbles and pebbles grew into rocks. And as the rocks grew larger, so did the collisions.

MIKE ZOLENSKY: If they collide head on or at higher velocities then they'll actually break apart, like shooting a gun at a wall.

NEIL deGRASSE TYSON: But other times, the rocks stuck together. And the larger they got, the stronger their gravity became.

DAVE STEVENSON (California Institute of Technology): Because of the gravitational attraction between these bodies, you coalesce. Instead of just making a mess—and you do make a mess as well—you build bigger things, because gravity holds things together.

NEIL deGRASSE TYSON: In time, gravity shaped them into small, round planets, or planetesimals, just a few miles across.

MIKE ZOLENSKY: Gradually, they grow from golf ball size to rugby ball size and then house size and then township size. And then one or two of these objects would get large faster than anything else and become the big boys on the block.

NEIL deGRASSE TYSON: Eventually, some of these planetesimals grew as big as our moon. And then they combined to form the four small, rocky planets closest to the sun: Mercury, Venus, Mars and Earth.

But the early Earth bore little resemblance to the planet we're all familiar with. And today, working out exactly what Earth was like as a newborn planet is no easy task. It's sort of like looking at me as an adult, and trying to figure out exactly what I was like as a baby: When was I born? How much did I weigh?

Now, a snapshot will give you a pretty good idea of what I looked like when I was young, but the Earth was born 4.5 billion years ago, and hardly anything survives from that time to tell us about our planet's infancy.

That's because at midnight on the clock, the new-born planet was nothing but a fiery ball of rock covered with lava.

DAVE STEVENSON: As you go back to these very earliest times, the first few hundred million years, the Earth was so energetic and was recycling materials so vigorously and melting material, that rocks from that period have not survived.

NEIL deGRASSE TYSON: So to reconstruct the story of the Earth's infancy, we look for clues not from the ground but from outer space. More than a hundred million miles from Earth, between Mars and Jupiter, lies a region called the Asteroid Belt. Here, trillions of asteroids, enormous rocks left over from planet building, are held in orbit.

Every now and then, a fragment of one of these asteroids is knocked out of orbit and set on a collision course with Earth. Called meteors, they can have a big impact.

PETER JENNINGS (ABC News Anchor): This exclusive report is about an object from space buried in ice, described as a scientific mother lode. We take you first to the northwest corner of British Columbia, near the Alaska border.

NEIL deGRASSE TYSON: Here, a massive meteor plunged through the atmosphere leaving a streak across the sky. A local bush pilot discovered the debris scattered across this lake, which was frozen over at the time. Realizing the importance of the find, he mailed a few fragments to NASA meteorite expert, Michael Zolensky.

MIKE ZOLENSKY: He sent samples down frozen in a case, and so I had a real problem getting through U.S. Customs because they wanted to open and thaw these out. And they were concerned that they were containing deadly pathogens from Canada or something.

NEIL deGRASSE TYSON: Zolensky immediately recognized it as a carbonaceous chondrite, a carbon-rich meteorite formed from the very same stardust that built the Earth.

MIKE ZOLENSKY: The last time we had a major fall of a carbonaceous chondrite was 30 years ago, so that means it's about one time in a career you have this happening to you. And to have it happen to me in my career, while I was still young enough to take advantage of it, was a very exciting thing for me.

NEIL deGRASSE TYSON: A team of scientists scrambled to collect as much of the meteorite as possible. This was the opportunity of a lifetime. More than 400 fragments, strewn across the frozen lake, could each contain clues to the very beginning of Earth.

The scientists hoped that inside, the fragments would be uncontaminated in the same pristine condition as when they formed, four and a half billion years ago.

If it lives up to expectations, this meteorite could reveal the exact chemistry of the dust grains that built the newborn Earth.

DAVE STEVENSON: Meteorites are a window on the past, and they tell us something about the conditions in which the solid planets formed.

MIKE ZOLENSKY: This particular meteorite is really special. In the first place, it has the highest carbon content of any meteorite and the highest amount of these preserved interstellar stardust grains of any meteorite, and it has a very high water content as well.

NEIL deGRASSE TYSON: In addition, about 90 other elements have been identified. And already they are providing a chemical fingerprint of early Earth.

And within this meteorite are radioactive elements that decay at a precisely known rate, allowing scientists to calculate the meteorite's age. And since most meteorites formed at the same time as the planets, and from the same material, the age of the meteorite gives you the age of Earth and its neighbors.

MIKE ZOLENSKY: If you date meteorites, what you find is that almost all meteorites have the same age, about four and a half to five billion years old. They're all the same. It's pretty monotonous: within a couple of tens of millions of years to hundreds of millions of years, they are all exactly the same age. And so what we do is take the oldest of the ages and use that as the initial age of the solar system.

NEIL deGRASSE TYSON: That narrow range of ages indicates that all meteorites and planets coalesced extremely quickly in the early days of the solar system.

But Earth had barely taken shape before the first of several major disasters struck the young planet. Earth's gravity was pulling in huge quantities of debris from space, a continual bombardment that generated enormous amounts of heat on the surface. At the same time, radioactive elements trapped deep within the Earth were decaying, producing even more heat, roasting the planet from the inside. The combined effect was catastrophic.

By eight minutes after midnight on our 24-hour clock, the planet had become a raging furnace. And when the temperature reached thousands of degrees, dense metals such as iron and nickel in Earth's rocky surface melted.

DAVE STEVENSON: The outer part of the Earth would have been completely molten. We call that a magma ocean. It's a liquid rock ocean, hundreds of kilometers thick.

MIKE ZOLENSKY: We think the Earth, at some point, was a big droplet of melt just floating in space. When you have a totally molten object like this, the heaviest elements—and that includes things like iron—would sink to the center of this droplet, and the lightest elements—things rich in carbon and water for instance, or light elements—would float to the top and float there like algae on a lake.

NEIL deGRASSE TYSON: The global migration of the elements, known as the Iron Catastrophe, would have a profound effect on the future of our planet. The sinking iron accumulated at Earth's center where it created a molten core twice the size of the moon. The liquid iron is constantly swirling and flowing. And even today this motion generates electric currents which turn our planet into a giant magnet with north and south poles. The core is still in constant motion. And we can see evidence of Earth's liquid iron core on the cold, snowy wastes of arctic Canada.

LARRY NEWITT (Geological Survey of Canada): The magnetic field is constantly fluctuating, on a minute to minute or even second to second basis. And one result of this is the fact that it causes the magnetic pole to actually move randomly over the course of a day.

NEIL deGRASSE TYSON: Every few years, geologist Larry Newitt sets out in search of the precise location of the magnetic north pole or north on a compass. Newitt spends days at a time on the ice in temperatures as low as minus 50 degrees Fahrenheit.

The geographic North Pole is in a fixed position, but the magnetic pole is always on the move. Over the last century, its position has changed dramatically.

To identify the pole's current position, Newitt measures the strength and direction of the magnetic field at about eight different sites then closes in on it.

LARRY NEWITT: Since we don't know where the pole is, we can't just go there and take a reading. So we surround it, and then I determine its location by a process of, well, what amounts to triangulation.

NEIL deGRASSE TYSON: At the time of the most recent survey, the pole had moved 125 miles off the Canadian coast. And Newitt and his colleagues have discovered something curious: its movement is picking up speed.

LARRY NEWITT: Over much of the past hundred years it's been around ten kilometers per year. But since about 1970, it started to accelerate, and now it's moving along at about 40 kilometers per year. If this keeps up, it'll reach Siberia in about another 40 or 50 years, but of course that's a rather dangerous extrapolation, we don't really know where it's going to go.

NEIL deGRASSE TYSON: Without Earth's liquid iron core, life would be in trouble. This swirling ball of molten iron is what generates the magnetic field around our planet. And we need that magnetic field because every day a deadly stream of electrically charged particles bombards the Earth.

Ejected by the sun in monstrous solar flares, these particles hurtle through space at about a million miles an hour, forming what is known as the solar wind. Some think that if the solar wind ever reached our planet, it would strip away the atmosphere. But Earth's magnetic field creates a protective shield that deflects these deadly particles.

And you don't have to travel far to see the fate of a planet that lost its shield. Four billion years ago, Mars had a liquid iron core and a magnetic field just like Earth's. Mars built up a thick atmosphere and supported liquid water on its surface. The planet may even have been home to primitive forms of life. But Mars is just a fraction the size of the Earth, so it cooled more rapidly. And as it cooled, its molten iron core hardened. As a result, Mars stopped generating its magnetic shield. And, according to one theory, this left its atmosphere to be scoured away by the solar wind.

Today, the surface of Mars is a barren desert. Mars is a stark reminder of what our world could have become if its iron core had cooled, because without a magnetic shield a planet is left prey to the solar wind, and life, as we know it, could never flourish.

The time had reached 16 minutes after midnight; the Iron Catastrophe was over.

But even with the formation of Earth's core and magnetic shield, our planet remained a hostile and alien world. Volcanoes spewed clouds of noxious gases and Earth was enveloped in a suffocating atmosphere of carbon dioxide, nitrogen and steam. With no oxygen to breathe and no ozone layer to block the lethal ultraviolet radiation, this was not a hospitable place for life, at least life as we know it.

And in the midst of this hellish brew, the moon was born.

Beginning when I was about 11 years old, I used to climb the stairs to the roof of this apartment building, where my family lived, here in New York City, a building prophetically named the Skyview Apartments. And with simple binoculars, just like these, I gazed up above the streetlights, beyond the buildings and into the night sky. And nothing will ever capture the excitement I felt when I first turned my binoculars on the moon.

When I saw that the moon was packed with mountains and valleys and craters, I thought I discovered an entire new world. And then I began to wonder, where did the moon come from and how did it get there?

Well, little did I know that about the same time, the mystery of the moon's origin was also attracting the attention of a scientist named Bill Hartmann.

BILL HARTMANN: I'm always looking at the moon and thinking about its phases. And when I was a little kid I had a telescope. I used to be out there drawing craters on the moon and was very excited that I could even see these craters and mountains and so on. So it's always had a special interest for me.

NEIL deGRASSE TYSON: Hartmann has been studying the moon for the last 40 years. And when he began his career, in the late 1960s, he and many other planetary scientists hoped that NASA's Apollo missions would solve the mystery of how the moon formed.

BILL HARTMANN: One of the pitches to sell that program scientifically was that we were going to be able to go to the moon and find these old rocks from 4.5 billion years ago, and they were going to tell us everything about the origin of the moon.

NEIL deGRASSE TYSON: The Apollo astronauts collected hundreds of rocks from the moon's surface. Scientists calculated their age using radioactive dating. To their astonishment, they discovered that the moon was millions of years younger than Earth.

And those same rocks held another secret.

BILL HARTMANN: I think the biggest single surprise was that the materials on the moon have exactly the same chemistry as the Earth and different from any samples that we have anywhere else in the solar system. So that pretty well forced the idea that the moon has to have formed from the same basic material as the Earth.

NEIL deGRASSE TYSON: But even more mysterious was that the moon rocks contained very little iron, just like the rocks on Earth's surface.

In a flash of inspiration, Hartmann and a colleague came up with a controversial new theory for the formation of the moon.

BILL HARTMANN: We came up with this very simple idea that maybe as the Earth was forming at our distance from the sun, somewhere nearby, made out of the same material, was a second large body which got pretty big before it finally plowed into the Earth.

NEIL deGRASSE TYSON: They proposed that about 50 million years after Earth had formed, a huge planetesimal was still roaming the solar system. This massive rock, about the size of Mars, slammed into our planet. The energy of that impact was so great it melted both the planetesimal and Earth's outer layers; the two fused together forming a new, larger Earth.

At the same time, this enormous collision ejected into orbit vast amounts of molten rock. This debris eventually coalesced to form the moon.

When Hartmann first went public with this idea, in 1974, it was considered scientific heresy.

BILL HARTMANN: So here we come in saying the moon formed out of this gigantic catastrophe that blew off part of the Earth's mantle. No one wanted to hear that. No on wanted to, uh, start thinking about that kind of model. All of us were taught, as junior geology students, that all processes in geology are slow, one sand grain at a time, erosion, and so on. And people would actually come to us and say we really shouldn't consider that model until we've exhausted all other models.

NEIL deGRASSE TYSON: Ten years passed before anyone would take the idea seriously. And that was only after hundreds of computer simulations showed that the moon could have formed from a giant impact. Today, Hartmann's big idea is almost universally accepted.

BILL HARTMANN: So it's been a long, slow process. And it's been really fun to see a little idea that you had a long time ago suddenly blossom forth as a leading theory.

NEIL deGRASSE TYSON: It was 16 minutes past midnight, 50 million years after our planet was born, and the moon had arrived.

But the repercussions of this disaster were just beginning to be felt. The moon started out about 200,000 miles closer to Earth than it is today, and appeared many times larger in the sky. Earth was spinning much faster than today making each day less than six hours long. And with the moon so close, its gravitational pull on Earth was enormous. Earth's surface rose and fell up to 200 feet during the cycle of the moon's phases. Over time, Earth's rotation slowed down as the moon drifted away, a process that continues even today.

BILL HARTMANN: The idea of being able to measure the movement of the moon away from the Earth has always been a challenge. And so, when the astronauts went to the moon, one of the things they did is they carried out this big device which was a reflector, a retroreflector that would beam a laser beam back in the direction that it came.

NEIL deGRASSE TYSON: On Earth, astronomers installed a laser so strong it could target the reflectors. In 1969, they made their first measurement of the time it took for the laser beam to reach the moon, hit the reflector, and bounce back to Earth, a round trip of about two and a half seconds.

BILL HARTMANN: Doing this year after year after year we've actually been able to confirm that the moon is moving slowly away. We not only get very exact information on the orbit of the moon, but we can actually see the orbit change.

NEIL deGRASSE TYSON: Now about 240,000 miles from Earth, the moon is moving away at a rate of one and a half inches every year.

The collision that created the moon was also a major stroke of luck for Earth. That impact was so immense that it forced Earth's axis to tilt in relation to the sun, causing the familiar seasons. And without the stabilizing influence of the moon, Earth would wobble dramatically about its axis. Today, the planet would experience wild climate swings.

But when did a planet that looks like the Earth we know begin to take shape?

Earth's hot molten surface took at least a billion years after the moon was created to cool and form a thick skin, its crust, or so scientists believed. But no one knew for certain because Earth is such a geologically restless place that none of the original crust survives today.

Yet startling new evidence is causing a major rethinking of when Earth's crust first formed. The clues to this mystery are embedded within these rocks in Western Australia. Here, geologists have extracted tiny crystals called zircons. About the size of sand grains, zircons are nearly as tough as diamonds. These relics of the early Earth formed when molten rock cooled into solid crust, so the age of the zircon gives you the age of the crust itself.

And it was here that geologist Simon Wilde hit pay dirt when he found one crystal so old he's convinced it was formed in the Earth's original crust.

SIMON WILDE (Curtin University of Technology): When we look at the chemistry in detail, from the zircons in this rock, we find that it's consistent with having grown in a piece of continental crust.

NEIL deGRASSE TYSON: Radioactive dating shows that the oldest of the zircons Simon Wilde found in these hills is 4.4 billion years old, suggesting that Earth might have cooled and formed a crust soon after the moon was formed.

SIMON WILDE: We don't know, of course, whether the continental areas were extensive or whether they were just small little islands of material. But certainly what we do know is that there was continental crust at 4.4 billion years ago.

NEIL deGRASSE TYSON: This was just 150 million years after Earth was born, not a billion years as previously thought. But that led to another mystery: once Earth was cool enough to form solid ground, water could collect on its surface, so when did that happen?

Geologists, including Stephen Mojzsis, think the answer may lie in these same tiny zircon crystals. Zircons are extremely rare, so to find just a few crystals, Mojzsis had to pulverize and sift through hundreds of pounds of ancient rocks.

An analysis of the chemical composition of the crystals revealed that the oldest zircons contained a high concentration of a curious ingredient. It was a type of oxygen called Oxygen-18, an isotope that could only be present in large quantities if the zircon crystals had grown in water.

The news that water might have been present so early in Earth's history was a bombshell.

STEPHEN MOJZSIS (University of Colorado): Not only was there crust present, which came as a surprise to most of us, it looks like, from some of the zircons, that that crust interacted with large volumes of liquid water.

NEIL deGRASSE TYSON: The idea that water settled on Earth's surface so soon is controversial, but if true, it suggests a planet much more like today's than anyone had ever imagined.

STEPHEN MOJZSIS: By 200 million years after the formation of the Earth you can imagine a landscape of islands and small continents, bathed by a primitive ocean.

NEIL deGRASSE TYSON: The time was only 10 minutes to one in the morning; the moon existed and so did a planet with not just land but water.

Liquid water is the key to life; every living thing requires it to survive. And eventually, water would cover nearly three quarters of the Earth's surface. In fact, all the world's oceans contain nearly one hundred million trillion gallons of it. It's an almost incomprehensible amount.

So, where did it all come from? How would Earth have ended up with such vast quantities of this stuff?

Well, strange as it sounds, these great oceans may have been there from the very beginning, just hidden away.

One key to the riddle was volcanoes, which, throughout Earth's infancy, pumped huge amounts of steam into the atmosphere. Then, as Earth cooled, that steam condensed into rain. Drop by drop, water collected in low-lying areas.

DAVE STEVENSON: There is nothing mysterious or surprising about this. The Earth does it right now. The main gas that comes out of Hawaiian volcanoes is water, steam. So, this is happening all the time.

NEIL deGRASSE TYSON: But some scientists argue it would take far too long to create such vast oceans by volcanic outgassing. Instead, Earth may have had some help.

The water in our oceans might have come from outer space, delivered to the surface by massive ice-bearing comets. The evidence for these ancient impacts is impossible to find today, since the original surface of our planet has long since been eroded or destroyed. But there's one place that preserves a record of impacts from that early era: our moon.

BILL HARTMANN: Every one of those craters was a meteorite explosion at some time.

NEIL deGRASSE TYSON: The moon's surface is littered with craters, some of them hundreds of miles across. In fact, the moon was ravaged by more than a million major impacts in its early years. Since Earth is much more massive, its gravitational pull would have attracted even more debris, resulting in possibly tens of millions of impacts.

BILL HARTMANN: We all hear about the impact 65 million years ago that wiped out the dinosaurs. And you're getting that kind of impact something like once a month on the early Earth. But this rain of debris left over from the formation of the solar system continues for several hundred million years.

NEIL deGRASSE TYSON: And in this cosmic debris field, comets containing huge amounts of dust and ice would have been plentiful, like dirty snowballs the size of mountains. Roughly half their mass was water.

One NASA scientist, Michael Mumma, wonders if these comets were the source of the water in Earth's oceans.

MICHAEL MUMMA (NASA Goddard Space Flight Center): One possibility is that Earth's water was delivered by the impact of bodies from beyond the Earth. These would naturally be the comets, which are rich in water. The proof in that would be to measure the composition of the cometary water and to compare that with the composition of water in our oceans.

NEIL deGRASSE TYSON: But studying comets is a tricky business. In the last 20 years, just a handful have passed close enough to study in detail, including one in 1997 called Comet Hale-Bopp.

MICHAEL MUMMA: A comet like Hale-Bopp would deliver about 10 percent of the water needed to fill one of the Great Lakes. This is a lot of water. Of course the oceans are much larger, and so we need many more comets to fill the oceans. But we're fortunate; we had many such comets in the early solar system, so we have every reason to believe it was cometary delivery that brought water to the early Earth.

NEIL deGRASSE TYSON: Mumma thinks that the heat of an impact would have evaporated the ice within a comet, creating storm clouds over vast areas of the planet. These clouds produced a deluge of hot, possibly acidic rain that continued for millions of years. At first the rain would have formed lakes and rivers, and eventually water would cover almost the entire globe.

But there's a problem with this theory. Earth's oceans contain a mixture of normal water, H2O, and a much smaller amount of a more exotic kind, known as HDO, or heavy water which contains an extra neutron.

In the comets analyzed so far, the proportions of these two kinds of water don't match the composition of water in our oceans.

MICHAEL MUMMA: They have twice the amount of heavy water that we see in Earth's oceans so if they were the comets that delivered the Earth's oceans they wouldn't fit the bill. Basically, they don't have the right properties.

NEIL deGRASSE TYSON: But Mumma hasn't given up. The comets already studied come from the outer reaches of the solar system, and he thinks comets originating closer to the sun might be different. Formed at higher temperatures, these comets could have a lower proportion of heavy water more closely matching our oceans. And tonight, Mumma hopes to test this idea by getting a first hand look at one of these elusive comets.

MICHAEL MUMMA: If its chemistry is different, and if the heavy water to light water is like that on Earth, it would be the first proof positive, or the "smoking gun" evidence, that comets did in fact deliver water to the early Earth.

NEIL deGRASSE TYSON: But first, the team has to hunt down the comet.

MICHAEL MUMMA: As soon as he has acquired it, we should see an image of it on the screen. There it is alright, yes sir, right there. You can see the elongated material flowing outward from the nucleus.

Joe, that looks excellent.

NEIL deGRASSE TYSON: With the comet in the crosshairs of their telescope they can home in on the kind of water it's carrying.

MICHAEL MUMMA: People often ask, "How can you measure water in an object that is a hundred million miles away?" We do this by a method called spectroscopy. It's a little bit like taking fingerprints; the little ridges on your fingers look different for every person. And in the same way, the light that is emitted by a given molecular compound is different; it emits at different wavelengths.

NEIL deGRASSE TYSON: But it turns out this comet is a very dirty snowball indeed. There's so much dust on the surface that it can't reflect enough light for the team find out what kind of water is on board.

MICHAEL MUMMA: It did not brighten as expected. This was a bit of a disappointment. Comets are quite fickle, they're unpredictable. In some ways they are like cats, they both have tails and they both do what they want to.

NEIL deGRASSE TYSON: But with astronomers finding two or three comets a year from the inner part of the solar system, Mumma could soon have another chance to test his controversial ideas about the origin of Earth's oceans.

MICHAEL MUMMA: One of the key things that every scientist keeps in mind, is you should never fall in love with your theory. So it's an idea, it's a hypothesis, it fits all the known facts. But it has not yet been proven, and we must be willing to give it up and modify it if it is not proven. But we will learn something in doing so.

DAVE STEVENSON: It's still possible that comets played a role. In fact, it's hard to imagine that they played no role. But it seems more likely and more physically sensible to look closer to home for the source of the water.

NEIL deGRASSE TYSON: Besieged by volcanoes and battered by impacts, Earth endured its most extreme punishment in its early years. It was beaten, bombarded, mangled, and melted all in just the first hour of our 24-hour history of the planet.

The young Earth was still very different from the planet we know today. It was a hostile and forbidding place, with an atmosphere full of poisonous gases. Yet, somehow, these harsh conditions set the scene for a crucial phase of Earth's development: the origin of life.

STEPHEN MOJZSIS: Very little is left behind from the Earth's earliest time period, but what is left behind has revealed to us a planet much more complicated than we ever thought, with different rock types, liquid water present and the kind of planet that we might expect life to emerge on.

Do we know if life was around 4.3 billion years ago? Well, who can say? We can say, however, that the template, the ground underfoot was there.

Could life have been present? Why not?

NEIL deGRASSE TYSON: But first, the once hellish Earth would have to undergo another change as radical as any that had come before. Catastrophe and cataclysm transformed the Earth, now our planet would be ready for the greatest drama of all time: the rise of life.

The "Origins" series continues online. On NOVA's Web site, explore the arguments for and against intelligent life in the Milky Way galaxy. Then cast your vote. Find it on PBS.org.

To order this program on VHS or DVD, or the book Origins: Fourteen Billion Years of Cosmic Evolution, please call 1-800-255-9424.

NOVA is a production of WGBH Boston.

Major funding for NOVA is provided by the Park Foundation, dedicated to education and quality television.

We see you reaching for the stars. Microsoft is proud to sponsor NOVA, for celebrating the potential in us all.

Science: it's given us the framework to help make wireless communications clear. Sprint is proud to support NOVA.

Major funding for "Origins" is provided by the National Science Foundation, America's investment in the future.

Additional funding is provided by the NASA Office of Space Science, the Alfred P. Sloan Foundation to enhance public understanding of science and technology, and the George D. Smith Fund.

Major funding for NOVA is also provided by the Corporation for Public Broadcasting and by PBS viewers like you. Thank you.

Broadcast Credits

Origins: Earth is Born

Hosted and Narrated by
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Origins: Back to the Beginning

Explore the Big Bang, the colossal force that spawned the galaxies, stars, and planets that we see today. Airing February 29, 2004 at 9 pm on PBS Aired February 29, 2004 on PBS

Program Description

"Origins: Back to the Beginning" explores how the colossal, mind-boggling forces of the early universe made it possible for habitable worlds to emerge. The clues begin with a race among scientists to capture lingering echoes of the big bang's ferocious energy in a microwave "whisper" from deep space. The race pits underdog astronomer Tony Readhead and his improvised detector in the high Andes against NASA scientists and their state-of-the-art satellite probe. Host astrophysicist Neil deGrasse Tyson shares his excitement with viewers as computer animation of the big bang's echo emerges on the screen. It's as close as we can get to a "photograph" of the primordial universe. Here we glimpse the seeds from which all the galaxies, stars, and planets eventually grew.

Transcript

Origins: Back to the Beginning

September 29, 2004

NEIL deGRASSE TYSON (Astrophysicist): A hellish, fiery wasteland, a molten planet hostile to life, yet somehow, amazingly, this is where we got our start. How? How did the universe, our planet, how did we ourselves come to be? How did the first sparks of life take hold here? Are we alone in the cosmos? Where did all the stars and galaxies come from? These questions are as ancient as human curiosity itself. And on "Origins", a four-part NOVA mini-series, we'll hunt for the answers. This search takes unexpected twists and turns. Imagine meteors delivering Earth's oceans from outer space. Descend into a toxic underworld where bizarre creatures hold clues to how life got its start. And picture the view when the newborn moon, 200,000 miles closer to Earth than today, loomed large in the night sky. This cosmic quest takes us back in time to within moments of the Big Bang itself and retraces the events that created us, this place we call home and perhaps life elsewhere in the cosmos. Coming up tonight: how did all begin?

Right now, we're all eavesdropping on the birth pangs of the cosmos. The accidental discovery of the Big Bang leaves scientists with nagging questions about the universe.

DAVID SPERGEL (Princeton University): ...how big it is, how old it is, what's it made of, and what were the processes that made galaxies, that made us.

NEIL deGRASSE TYSON: So a furious race is on to solve the ultimate mystery.

ANTHONY READHEAD (California Institute of Technology): The spirit of competition is one of the things, of course, that drives scientists.

Keep our fingers crossed. Let's hope and pray.

NEIL deGRASSE TYSON: And as our new vision of the universe emerges, strange ideas reveal themselves. It seems that we are stardust.

STAN WOOSLEY (University of California, Santa Cruz): Stars are the ultimate alchemist.

ROBERT KIRSHNER (Harvard University): You get carbon and nitrogen and oxygen made in stars.

NEIL deGRASSE TYSON: Those elements are the building blocks of life. That means...

SANDRA FABER (University of California, Santa Cruz): ...our universe is hospitable to life. There are billions and billions of galaxies everywhere, making stars that are right for solar systems. The habitat for life is everywhere.

NEIL deGRASSE TYSON: A scientific detective story takes you back to the beginning on tonight's episode of "Origins", on NOVA, right now.

Major funding for NOVA is provided by the Park Foundation, dedicated to education and quality television.

We see you inventing the next big thing. Microsoft is proud to sponsor NOVA for celebrating the potential in us all.

Science: it's given us the framework to help make wireless communications clear. Sprint is proud to support NOVA.

Major funding for "Origins" is provided by the National Science Foundation, America's investment in the future. Additional funding is provided by the NASA Office of Space Science, the Alfred P. Sloan Foundation to enhance public understanding of science and technology, and the George D. Smith Fund.

Major funding for NOVA is also provided by the Corporation for Public Broadcasting and by PBS viewers like you. Thank you.

NEIL deGRASSE TYSON: The grand dance of our universe is a breathtaking vision. Stars parade across the sky in lockstep, night after night. The galaxies spin, vast cities of stars bound together to create stunningly elegant forms.

Until recently—our own lifetimes—we couldn't hope to answer the most basic questions about the cosmos. Has the universe always been here? Did it have a beginning?

I first encountered those grand mysteries as a nine year old kid. We came on a field trip here, to the Hayden Planetarium. Looked a lot different then, but that first trip changed my life. More or less on the spot, I decided to become an astrophysicist, even though I could barely pronounce the word.

And now, all grown up, I've returned to the Hayden as its director. And over that time, our understanding of the universe has been transformed again and again.

Astronomers believed that our cosmos had always existed, eternal and unchanging. In its last version, the idea even had a name, the steady state theory. But that was really just an assumption, and like so much received wisdom in science, it would only ultimately be proved wrong by accident.

The breakthrough came in the early days of the space race. In 1962, astronauts were heroes, and for a while, America went space crazy.

Space even made the charts when the song "Telstar," named for the first satellite to transmit transatlantic phone calls, rocketed up to number one.

The real Telstar satellite was built by AT&T, the phone company. Telstar was the first link in a truly global communications network. But there were a few bugs in the system, especially an annoying hiss in those early calls relayed by satellite. AT&T engineers wondered if the problem might lie in the way Telstar communicated with earth, using a form of energy called microwaves.

Telephones are actually very simple machines. They all work in pretty much the same way.

Hello. No, I'm kind of busy now. Can, can you call back later? Hang...hang...hang on a sec.

What they do is they convert sound waves into electrical impulses then take those same electrical impulses and convert them back into sound waves at the other end of the line.

I've got to go, I'm working here. Alright? Let's talk later, but thanks for calling. Bye.

Satellites take this one step further, they convert the electrical impulses into forms of light we call microwaves and radio waves.

To get a handle on that, let me introduce you to my cosmic tuner. It's sensitive to all forms of light there are. Most familiar is visible light with its rainbow of colors. What makes one color different from the next is simply its wavelength. And I can use this knob to tune one wavelength to the next.

Let's start with violet. It has the shortest of all wavelengths. Moving to longer and longer wavelengths, we pass from one color to the next, right on up to orange and then red. There ends visible light.

But light continues beyond that, just increase the wavelength. What do you get? Infrared. Can't see infrared, but we feel it, we sense it as heat. Beyond infrared, we find microwaves and then, the longest of them all, radio waves. Both radio waves and microwaves we use to communicate through earth's atmosphere and through space itself.

As it happens, almost everything in the night sky emits energy in the form of these same micro and radio waves. Here is the Milky Way photographed in visible light, and here is its image at radio wavelengths.

After World War II, this new way of looking at the sky launched the field of radio astronomy. And now it would lead to a phenomenal discovery.

Robert Wilson and Arno Penzias were both experts in the new fields of radio and microwave astronomy, and in 1964, AT&T's Bell Labs asked them to help figure out what might be causing the annoying hiss in satellite communications.

To do so, they began their detective work with this giant antenna that could receive signals from Telstar. To test the instrument they pointed it at an empty patch of sky. Aiming at nothing, they expected to find nothing. Instead, to their surprise, they picked up a faint microwave signal, apparently coming from empty space.

Sure that couldn't be right, they looked for any possible source of stray microwaves. They even climbed into the horn to clean up after a pair of unwelcome guests.

ROBERT WILSON (Harvard-Smithsonian Center for Astrophysics): When was the last time we were up here?

ARNO PENZIAS (New Enterprise Associates): Thirty-eight years ago.

ROBERT WILSON: '65 or'64. There had been a pair of pigeons living there and deposited pigeon droppings inside. And that was clearly a possible microwave-loss material. As a graduate student I did worse things. You probably did too.

ARNO PENZIAS: Oh, yeah. Yeah, you just do what you have to do. You do what you have to do every day.

NEIL deGRASSE TYSON: Nothing worked. The hiss was still there, and, mysteriously, it seemed to be coming from wherever they looked in the sky.

ROBERT WILSON: We could, by then, rule out that it came from the horn itself. We were unaware of anything in the sky that should do it, and we thought the horn should not be picking anything up from the ground. It was just was sort of surreal. It didn't fit our idea of physics.

NEIL deGRASSE TYSON: But the microwave hiss, so perplexing to Penzias and Wilson, did fit a radical idea being explored by a group of physicists just 40 miles down the road in Princeton, New Jersey.

The Princeton team was trying to prove that our entire universe had actually been born in a in a tremendous burst of energy, billions of years ago. Team leader Bob Dicke believed that some of that energy should still be detectable as a faint hiss of microwaves in space. To test that hunch, Dicke asked a young post-doc named David Wilkinson to set up this miniature antenna in his spare time.

DAVID WILKINSON (Princeton University (d. 2002): We weren't in any particular hurry because Bob Dicke's idea was so original. We weren't too worried about somebody else getting there before we did. We went down to Arch Street in Philadelphia and dug around in the World War II surplus shops to find things that were cheap.

NEIL deGRASSE TYSON: But before their instrument was up and running, word reached Penzias and Wilson, who gave Dicke a call.

DAVID WILKINSON: He hung up the phone, and I'll never forget exactly what he said. These are his exact words. He said, "Well, boys, we've been scooped."

NEIL deGRASSE TYSON: Scooped indeed to the greatest discovery in cosmology, the Big Bang. In the Big Bang our entire universe, all the matter, all the energy that would ever exist, burst into being in a single instant. A flash of light filled the cosmos. And as the universe expanded, that light stretched with it to longer and longer wavelengths, through the visible range, to the infrared. Until, now, that flash of light remains as a faint glow of microwaves filling the entire sky, the glow that Robert Wilson and Arno Penzias detected with this antenna.

DAVID SPERGEL: Penzias and Wilson's discovery of the microwave background is what made cosmology a science.

ANTHONY READHEAD: It suddenly made you realize that history was being made. Here you were, and suddenly the universe, as understood by man, was different to what it had been like yesterday.

DAVID SPERGEL: All of a sudden you had data and you really tested a theory. You had a theory that said the universe started with this hot Big Bang, and what Penzias and Wilson saw was this leftover heat from the Big Bang.

NEIL deGRASSE TYSON: Their serendipitous discovery was so important it won Penzias and Wilson the Nobel Prize.

ARNO PENZIAS: The actual ceremony in Stockholm was kind of a blur. I never have quite gotten over the feeling of not being a grownup, that other people are smarter, older, and so forth, and that...I don't think that ever leaves.

ROBERT WILSON: When the Nobel Prize was announced I think probably one of the first things that I thought about was, "Do I really deserve this?" And "Should my name be on the same list with as Einstein?" Which just seemed completely wrong. Over the years I guess I've come to understand that the Nobel Prize is given for discovering something, not for being the smartest person around. So while there are much smarter people around, we did something significant and I feel comfortable with it now.

NEIL deGRASSE TYSON: Now that we know what to look for, it's not all that hard to detect the Big Bang.

Take an ordinary TV set, the old fashioned kind, before cable. All you need to do is change the channel until you come between two stations. Most of that static comes from stray local radio waves hitting these rabbit ear antennas, but amazingly, about one percent of the snow and noise comes from microwaves produced in the Big Bang itself.

Right now, we're all eavesdropping on the birth pangs of the cosmos.

The discovery of the Big Bang was revolutionary, but from the start there was a nagging problem. According to the theory, the Big Bang made everything, all the energy and all the matter in the cosmos. In the modern universe, matter is concentrated into lumps, vast webs of galaxies with hardly anything in the voids between. But the microwave glow Penzias and Wilson had seen showed no structure at all. And that's the problem, a big one.

The microwave glow of the Big Bang seemed perfectly smooth, the same everywhere on the sky. But if that were true, then the universe that evolved from that Big Bang should be just as smooth, like this formless fog. So then how did our universe come to be filled with clumps of stuff, galaxies, suns, and planets?

Maybe the early universe was not as featureless as it seemed. Maybe it contained some tiny seeds, little dense spots that gravity could shape into the cosmic structures we see today. Cosmologists figured that those slightly denser regions in the early universe would show up as bright spots in the microwave glow of the Big Bang, so they set out to find them.

They would look, and look, and look, for thirty years, and they would find nothing.

ANTHONY READHEAD: The astonishing thing is that the harder we looked, the more mysterious the universe became, because all we saw was a blank sheet of paper, nothing was written on it at all. And we went down to a part in a thousand, it was a blank sheet. We went down to a part in ten thousand, it was a blank sheet. It was at this point that my colleagues at Cal Tech started telling me that I was proving we weren't here.

NEIL deGRASSE TYSON: No lumps, no galaxies, no us; that's what every observation of the Big Bang's microwave glow seemed to show. Either we just didn't understand the Big Bang, or secrets remained hidden within the microwave glow of the infant universe. Finally astronomers wanted to settle the question once and for all.

Flying above Earth's atmosphere, this satellite, called COBE, was designed to find the telltale bright spots within the apparently uniform microwave glow, if they were there.

CHARLES L. BENNETT (NASA Goddard Space Flight Center): As a member of the COBE team, we wondered all the time, would we detect this non-uniformity or wouldn't we? We thought that, theoretically, it should be there. For 30 years people had thought that, too, and went out and made measurements and didn't find it. So we didn't know for a fact whether we'd see it or not. It was a, it was a crap shoot.

NEIL deGRASSE TYSON: NASA launched COBE in 1989. It would spend two years in near-Earth orbit, observing the microwave hiss, the energy of the Big Bang, at hundreds of thousands of points in the sky. When it accumulated enough data, COBE revealed this: a blotchy pattern that doesn't look very dramatic to most people. But to astronomers it was a revelation.

CHARLES BENNETT: Well, we didn't, as some people said, see the face of God in the COBE picture. What we did see was a spectacular face of the early universe, which was just what we wanted to see.

NEIL deGRASSE TYSON: This was what they had been waiting for. The blue colors reveal places where there's slightly more matter in the early universe. From these concentrations of matter gravity will carve out galaxies and stars, suns and planets, and eventually, our home. In one brilliant stroke, COBE confirmed that the universe, as we know it, evolved out of the cataclysm of the Big Bang.

But at the same time, it left much of the story untold. You see, COBE had a limitation, a kind of fuzzy vision. A COBE picture of me would look something like this.

You can tell that you're looking at a face but not whether I'm twenty years old or sixty, or anything in between. It was much the same with COBE. Its picture was too fuzzy to reveal much of what was really happening in the early universe.

LYMAN PAGE (Princeton University): It was as though we had seen the Earth, and we knew there were oceans and we knew there were continents, but we didn't know how continents formed, we didn't know that there were mountain ranges, we didn't know there were grand canyons, that there were polar caps.

DAVID SPERGEL: The microwave background has encoded in it a tremendous amount of information about the properties of the universe: how old it is, what it's made of, how many atoms are in the universe, how fast it's expanding. And with the COBE data, we couldn't answer any of those questions.

NEIL deGRASSE TYSON: In other words, COBE was teasing us. Its fuzzy picture concealed clues to fundamental mysteries, everything from the age of the universe to the events that unfolded in the first moments of the Big Bang itself. To uncover these clues we needed a much sharper image of the Big Bang's microwave glow.

That's why NASA built this: COBE's successor, a satellite called WMAP. The "W" stands for the late David Wilkinson, one of the Princeton group that pioneered the search for the remnants of the Big Bang. Its twenty horns were designed to collect microwaves from the infant cosmos with unprecedented precision. And its state-of-the-art electronics could then assemble an ultra sharp image from the faint signal that the horns collected.

The WMAP team started work on its satellite in 1996, and from the beginning, as mission leader Chuck Bennett recalls...

CHARLES BENNETT: The enemy was Murphy. Murphy's Law happens. Murphy's Law says that if anything can go wrong it will go wrong. And believe me it's true.

CO-WORKER: "Hey, Chuck, did you hear about the problem we're having with the grounding?"

NEIL deGRASSE TYSON: This was Chuck Bennett's life, coping with the inevitable crises that almost daily threatened the WMAP mission. It would take at least seven years to get results, a schedule that would give NASA's rivals a window of opportunity.

Ambitious observers like Tony Readhead set out to see if they could beat NASA to major discoveries of their own.

ANTHONY READHEAD: I think it's, it's very important to recognize, of course, that the spirit of competition is one of the things, of course, that drives scientists just like everybody else. And then the idea that the, the huge agency of NASA was going to go out there, and they were really going to do the job properly—they were going to provide people with a three-course meal—made many of us feel that we would really like to go out there and perhaps get a few appetizers in, which might answer the most fundamental and interesting questions first.

NEIL deGRASSE TYSON: Beginning work in 1999, Tony knows he cannot compete with the space agency's formidable resources, so he sets his sights on one piece of the puzzle. He decides to make remarkably detailed observations of a few, tiny patches of the sky, hoping to capture the sharpest images yet of the Big Bang's microwave glow.

If he succeeds, he will be the first to go beyond COBE's fuzzy picture and identify the tiny seeds of matter that gave rise to the universe we live in. To make this discovery, Tony and his team build an instrument called the Cosmic Background Imager. What looks like an array of giant tin cans is 13 sensitive microwave antennas linked together. This kind of array is the perfect design to produce the exceptionally detailed images Tony seeks.

But there's a price to pay for such precision.

ANTHONY READHEAD: In order to do observations of the microwave background, you have to get above most of the water vapor in the atmosphere, so you either have to go to space, of course, but that's very expensive, or you have to go to the South Pole, or come to a place like this, which is up at a very high altitude in the Andes. In other words, you have to get halfway to space if you're going to want to compete with the guys who are out in space.

NEIL deGRASSE TYSON: But to work up this high, almost 17,000 feet, the team must use oxygen tanks, and they are always vulnerable to the bitter cold, the wind, and the weather.

Just ahead of what was supposed to be a routine observing run, a ferocious three-day blizzard knocks out a key telescope drive motor.

ANTHONY READHEAD: When you tried to drive it, it just didn't move.

NEIL deGRASSE TYSON: The instrument can't track the sky with the precision Tony needs. If the telescope can't move, Tony can't observe.

It's a setback, but a minor one, Tony devoutly hopes.

ANTHONY READHEAD: Of course this is extremely annoying, because we go to extraordinary lengths to try to ensure that we don't lose any observing time. We really cannot afford to be down for a few days, and if we are down for six weeks it is a very big problem indeed for us.

NEIL deGRASSE TYSON: Isolated on their mountaintop, Tony, Ricardo and Eduardo now struggle, without backup, to fix their broken motor. But in a way they're fortunate, the WMAP team will have no such luxury, to fix anything that breaks once their satellite reaches space.

CHARLES BENNETT: Once you launch the thing, you don't get to turn that screwdriver one last time, or make an adjustment, or replace the part that broke. It's got to be right. One of the key things to make sure that you've got it right is to test it and test it and test it again.

NEIL deGRASSE TYSON: WMAP's final hurdle comes in this giant vacuum chamber, built to replicate the cold and the airlessness of space itself. The satellite cycles through here again and again to ensure that no mission-threatening flaw remains.

ANTHONY READHEAD: Ricardo, can you check that there are no ladders around the telescope?

NEIL deGRASSE TYSON: Tony's struggle is paying off. After three days, the team believes they have resuscitated their broken motor.

ANTHONY READHEAD: Is it done? Okay, please switch on the drive key.

MAN: It's on.

ANTHONY READHEAD: I'm going to try a flare in Azimuth.

MAN: Keep our fingers crossed.

ANTHONY READHEAD: Keep our fingers crossed. Let's hope and pray. Okay.

MAN: That's fantastic.

ANTHONY READHEAD: This is really great. We've come back from a major crisis here over the last three days. These guys have done a great job.

NEIL deGRASSE TYSON: With his telescope operational again, Tony can finally get back to the painstaking task of collecting cosmic microwaves. It's slow work. It takes a minimum of fifty nights to create a usable image of a tiny patch of the sky.

Finally, five years into the project, the WMAP satellite passes its last test. There is nothing left to do: either the instrument will work in space or it won't. It's time to fly.

Chuck, of course, continues to fret.

CHARLES BENNETT: We finally reached the point in the project when it was time to package up the satellite and send it down to the Kennedy Space Center. Of course, the problems didn't stop there. We had to put some things back together again that we had to take apart, and we found little problems along the way.

LAUNCH ACTUALITY: Green board. Five, four, three, two, one, main engine start, and liftoff of the Delta 2 rocket with the MAP spacecraft.

CHARLES BENNETT: In the end we launched within the first seconds of the first day of our launch window. It was a picture perfect launch. Everything went very, very smoothly.

LAUNCH ACTUALITY: Initially a smooth flight being reported, solid motors are now at maximum thrust.

LYMAN PAGE: When it was being launched, your heart's in your mouth. You've poured your life into this thing. You know you eat it, you drink it, you breathe it. You wake up at night thinking about something that you might have not done right. And it launched, and it got off the ground. And that was incredible.

NEIL deGRASSE TYSON: After its launch, WMAP still has a three-month journey to reach its final destination, a million miles from earth: a special location, the sun and Earth's second Langrangian point, or L2. At L2, the combined gravitational pull of the sun and Earth will hold the satellite in a fixed orbit. In that position, WMAP's shielding can block out the contaminating microwave radiation from the sun and the earth.

But getting there takes one of the most complex trajectories ever planned for a space science mission.

CHARLES BENNETT: One of the headquarters officials was visiting me one day, and he asked me, "What part are you most worried about?" And I said, "Getting from here to there."

NEIL deGRASSE TYSON: WMAP's guidance systems perform flawlessly. But once it reaches L2, the satellite still needs a full year to produce its first results.

That year gives Tony just the time he needs. Before NASA's WMAP can report back, Tony manages to gather enough data to yield a major discovery.

ANTHONY READHEAD: One tends to forget, because of all the, the difficulties that one has to go through, just the true wonder of what we are seeing.

NEIL deGRASSE TYSON: What we are seeing are fine details, more than 100 times smaller than those COBE saw, the first direct observational link between the early universe and the one we live in.

ANTHONY READHEAD: These brighter spots, hotter in temperature, are showing where there is more stuff. And that's extremely exciting because it's actually showing where all the structure in the universe that we see around us today came from.

NEIL deGRASSE TYSON: Over billions of years, gravity will transform this slightly denser clump of stuff into this: a cluster of galaxies, home to trillions of stars like our own sun.

ANTHONY READHEAD: Had there not been seeds like this in the microwave background showing that there was more stuff, we wouldn't be here today talking about it.

This is a wonderful time in science. This is actually the best time of science, because we have the satisfaction of—through these observations and these discoveries—having confirmed certain predictions. We are actually on the brink of a revolution of unimaginable proportions.

NEIL deGRASSE TYSON: In February 2003, that revolution takes off. In just over a year, WMAP has sampled more than two million points in the sky. Finally, almost four decades after the faint glow of the Big Bang was first detected, the satellite delivers a beautifully detailed picture of the peaks and valleys that mark where the matter lies in our newborn universe.

So, David, this is it, huh?

DAVID SPERGEL: This is the map. This is what the universe looked like 380,000 years after the Big Bang.

NEIL deGRASSE TYSON: Were you the first one to see this when it came from the telescope?

DAVID SPERGEL: I think I was the first one to see this particular version of the map.

NEIL deGRASSE TYSON: What did it feel like?

DAVID SPERGEL: Oh, it was so cool. I mean, you know, to know that you are one of the few people that get to see this first was just awesome.

NEIL deGRASSE TYSON: In this version of the WMAP picture, the peaks are hot spots that show where the super clusters of galaxies will form; the valleys will become empty space. Most important, this pattern is so detailed that cosmologists can now piece together almost the entire story of what happened during the birth of the universe to create the structures we see today.

The Big Bang itself remains shrouded in mystery, although WMAP tells us that the universe's birthday took place 13.7 billion years ago. Using WMAP data, we can reach back almost to that beginning, at a time when the universe was tiny, much smaller than this pearl.

We're not sure what came next, but our best current idea is that an event we call inflation triggered a hyper-fast expansion, enlarging the universe a trillion, trillion, trillion fold. But just as suddenly as it began, inflation stops, leaving behind a dense, hot, violent universe. All of space is filled with a zoo of exotic particles, the precursors of ordinary matter. And all the light within the cosmos is trapped in an endless pinball game, bouncing off these particles.

But as the universe continues to expand it cools until, at last, 380,000 years after the Big Bang, temperatures fall to the point at which familiar, stable atoms can form. In that instant, the primordial fog clears, and the light from the Big Bang flashes free, forming the image that WMAP has captured: a true baby picture of the cosmos.

DAVID SPERGEL: The really remarkable thing that MAP found was that the universe was incredibly simple. I think we're now close to the right story for how the universe evolved from a second or so after the Big Bang 'til today.

NEIL deGRASSE TYSON: But not so fast. There are no signs of life in this picture. The WMAP universe contains only the simplest atoms: mostly hydrogen, just a single proton with one electron, along with a little bit of helium. Living chemistry requires more complex building blocks: carbon, oxygen, iron and the rest. But if they didn't exist in the early universe, where did they come from?

Recent supercomputing simulations show the infant universe filled with vast, billowing clouds of hydrogen. Almost immediately, the clouds begin to condense, pulled together by their own gravity. As hydrogen piles on, the central region grows more and more dense, until something brand new lights up the universe: a star.

These first stars are hydrogen giants, 100 times or more larger than our own sun. Such large massive stars are short-lived—two or three million years at the most—and they go out with a bang in explosions so big they've been dubbed "hypernovae."

And it's with these cataclysms that the universe begins to accumulate the building blocks of life. All the atoms in the universe heavier than hydrogen and helium are forged by stars.

ROBERT KIRSHNER: Stars are really interesting. They, they don't just sit there. Because they last so much longer than we do, we think they're, they're permanent.

STAN WOOSLEY: Stars are the ultimate alchemists. They, they turn light elements into heavier ones. They get the energy they need to glow that way. The star begins its life made out of hydrogen and helium, mostly—about 70 percent hydrogen, 28 percent helium, in the case of the sun.

NEIL deGRASSE TYSON: In a star's core, the temperature and pressure are so high that hydrogen atoms fuse together to make helium. Hydrogen fusion releases prodigious amounts of energy, the heat and light of the star.

ROBERT KIRSHNER: That's the story for 90 percent of the life of a star, fusing hydrogen to make helium.

NEIL deGRASSE TYSON: Eventually, though, the star runs out of hydrogen and begins to fuse its stocks of helium, making yet heavier elements.

STAN WOOSLEY: And so the way it works, and it always works this way, is that it contracts and it gets hotter. And if it can find something new to burn, whether it's the kitchen sink or coal or whatever, it'll burn it.

ROBERT KIRSHNER: Helium is taken three at a time to make carbon.

STAN WOOSLEY: You can add one more helium to that carbon and make element number 8, oxygen.

ROBERT KIRSHNER: That's a tremendous step forward. You get carbon and nitrogen and oxygen made in stars.

STAN WOOSLEY: Now, this is great, because on the board, we already have the principal elements of life.

ROBERT KIRSHNER: Organic chemistry is the chemistry of carbon.

NEIL deGRASSE TYSON: Carbon fuses next, and still heavier elements begin to form.

STAN WOOSLEY: Sulfur, argon, chlorine.

ROBERT KIRSHNER: Potassium, calcium, scandium—the pace of this gets faster and faster.

STAN WOOSLEY: Back in the middle, silicon is starting to burn at three and a half billion degrees, a stupendous temperature.

ROBERT KIRSHNER: It makes titanium, vanadium, chromium...

STAN WOOSLEY: ...manganese, cobalt, nickel, and iron.

ROBERT KIRSHNER: Iron is really the end of the road. It's, it's sort of the nuclear turnip out of which you just cannot squeeze anymore.

STAN WOOSLEY: It's the end of the game. A star that has relied on fusion has come to the point where it has nothing more to spend.

ROBERT KIRSHNER: The star is suddenly caught in a disaster. There's radiation going out from the outside, but deep in the inside there's no more fuel.

NEIL deGRASSE TYSON: Iron can't fuel the stellar furnace. And so when a star builds up too much iron it dies.

ROBERT KIRSHNER: The core collapses, it bounces.

STAN WOOSLEY: And it begins to move out, first slowly, and then faster and faster.

ROBERT KIRSHNER: And that sends a very sharp wave back out through the star.

STAN WOOSLEY: And now, what was falling down is going out. The whole thing is blowing up, and you've made a supernova.

ROBERT KIRSHNER: A supernova explosion can be as bright as four billion stars like the sun.

STAN WOOSLEY: A stupendous explosion.

NEIL deGRASSE TYSON: Such outrageous energies overcome the iron barrier, cooking iron atoms into all the rest of the elements on the periodic table.

STAN WOOSLEY: So starting right down here you can go, copper...

ROBERT KIRSHNER: ...zinc...

STAN WOOSLEY: ...gallium...

ROBERT KIRSHNER: ...germanium...

STAN WOOSLEY: ...arsenic...

ROBERT KIRSHNER: ...zirconium...

STAN WOOSLEY: ... Niobium, Molybdenum, Technetium...

ROBERT KIRSHNER: ...strontium...

STAN WOOSLEY: ...rhodium...

ROBERT KIRSHNER: Done! That's enough elements.

NEIL deGRASSE TYSON: We are all stardust: the carbon in our bodies, the iron in our blood, the calcium in our bones, every last atom was formed in a star. But it's not that simple.

No one star can produce more than just a dusting of heavy elements, so to create an environment friendly to life, the universe had to find a way to concentrate the good stuff, which it did in a process that is remarkably like the way chef Michael Romano cooks up a bowl of soup.

MICHAEL ROMANO (Union Square Cafe): As you know, a cornerstone of great cooking is a rich soup. And all soup starts with water, so let's add some water in the pot.

NEIL deGRASSE TYSON: In this culinary cosmos, these ingredients stand in for the first stars, each flavoring the surrounding broth just a little bit.

MICHAEL ROMANO: And then we need heat, which we have.

NEIL deGRASSE TYSON: There's no shortage of heat in the cosmos, it turns out.

MICHAEL ROMANO: That's a good thing.

NEIL deGRASSE TYSON: In the broth left behind by the first stars, new stars form. That's this second round of ingredients. And as they simmer, the interstellar soup gets stronger and stronger.

MICHAEL ROMANO: Look at how rich that's become.

NEIL deGRASSE TYSON: I, I still can't wait.

MICHAEL ROMANO: Yeah. You remember that water we started with? And look what it's turned into. It's actually thickened, and a lot of flavor in there, so I think at this point it has enough flavor to support adding the star of the show, which is our shellfish and fish.

NEIL deGRASSE TYSON: Finally this cosmic soup is nearly ready, to the point where, after bubbling for billions of years, it can support the kind of life that would emerge on earth.

MICHAEL ROMANO: And there you go, Neil. That's for you.

NEIL deGRASSE TYSON: Thank you, Michael.

MICHAEL ROMANO: Enjoy it.

NEIL deGRASSE TYSON: Thank you.

What Michael just did is entirely analogous to what happens in the real universe, where each generation of stars enriches the broth out of which the next generation forms until, at last, the cosmic soup is rich enough for life.

We know this occurs, because we can see it happening next door, right in our own Milky Way galaxy, in perhaps the most famous astronomical image ever made: the Hubble Space Telescope portrait of the Eagle Nebula.

JEFF HESTER (Arizona State University): It does feel like this image is everywhere, because this image is everywhere. It's not everybody who gets to see something that they've done show up on a postage stamp, or happen to see something that you've done on a tee shirt with somebody just walking across campus.

My wife will see this picture in some context and she'll poke me and say "Now, explain to me again why we don't get any royalties off that picture."

NEIL deGRASSE TYSON: That picture of the Eagle Nebula has been dubbed "The Pillars of Creation." It's become a modern icon. When the Hubble first transmitted it back to earth, scientists themselves were stunned at what they saw.

JEFF HESTER: We were not prepared for what we saw when we finally got the images of the Eagle Nebula put together. We weren't prepared for the beauty of what we had assembled. We weren't really prepared for the science of what emerged from it. Every now and then you get lucky.

NEIL deGRASSE TYSON: What the image revealed were places in our own Milky Way galaxy where new stars are actually forming.

JEFF HESTER: You see these little nodules sitting around here. Each one of those is large enough to swallow our solar system several times over. Embedded in at least some of those, we can see that there are young stars, stars that will become stars like our sun, around which are going to form solar systems, perhaps like our own.

Is it possible that four and a half billion years from now, some civilization on a planet orbiting that star will look up at the sky and wonder about where they came from? I'm not going to say it's likely, but it is certainly possible.

NEIL deGRASSE TYSON: Possible because conditions in the Eagle Nebula are close to what they are here, the one place in the universe we know that life exists, our own solar system.

The Eagle Nebula contains just about the same mix of heavy elements that our sun does: carbon, nitrogen and the rest. But the big question is whether life, or at least the conditions that could allow life to emerge, are widespread throughout the cosmos. Do we live in a universe that welcomes life? Or are the hundred billion galaxies out there mostly barren, empty desert?

That's the question that has brought Sandra Faber to the Keck Observatory in Hawaii. What are the odds for life in the cosmos as a whole?

SANDRA FABER: It's important to realize that, astronomically, the seeds of life on Earth were sown four and a half billion years ago when the sun and solar system formed. That's a long time back in the past, but we can ask ourselves now, "Can we see the seeds of life in other galaxies in great abundance back then? Or maybe even perhaps earlier than that?"

NEIL deGRASSE TYSON: Sandy uses the Keck Telescope as a kind of time machine that can look deep into the past. Its giant mirror, 36 feet across, can capture a snapshot of galaxies when they were much younger than our own.

But merely seeing such distant galaxies is not enough. Sandy wants to discover what they're made of. To find out, she uses an instrument called a spectrograph.

Sandy's spectrograph, called DEIMOS, is one of the most powerful in the world. It takes the light from up to a hundred and fifty galaxies at a time, each isolated in a single hole in a sheet of metal called a "slit mask." DEIMOS then breaks that light up into the visible spectrum, the rainbow of colors from violet to red.

Zooming in on a galactic spectrum reveals a forest of bright and dark lines, patterns that reveal the presence of particular elements.

SANDRA FABER: Using spectra as our tool, we can tell you what elements exist in that galaxy: oxygen, carbon, iron. And we can tell you whether the galaxy is rich in those elements. Has the broth cooked a lot? Or is it still too dilute to make planets?

NEIL deGRASSE TYSON: That's what Sandy will do tonight, measure the amounts of heavy elements, to determine each galaxy's readiness for life. Sandy and her team ultimately plan to examine 65,000 galaxies in all, in a massive census dubbed the "DEEP survey."

Here are the results, hot off the telescope.

SANDRA FABER: This is fantastic. That's oxygen and oxygen here.

NEIL deGRASSE TYSON: This bright spot marks the presence of oxygen in a galaxy five billion light years away.

SANDRA FABER: Just purely by coincidence, we're looking at galaxies, their light left just when our sun was forming in our own galaxy, right? And so this one here...

NEIL deGRASSE TYSON: Sandy uses the sun's level of oxygen and other heavy elements as her benchmark. If a galaxy has a similar mix of elements, then, potentially, it could support the same living chemistry we find here at home.

SANDRA FABER: So that would be, that galaxy would be a really good place to look for, for planets, because it's even more abundant in metals than our own galaxy is.

NEIL deGRASSE TYSON: Two years into a projected 10-year observing program, the deep survey team has already detected thousands of distant galaxies that are rich in the elements of life. And that leads to a startling conclusion.

SANDRA FABER: Our universe is hospitable to life, that there are billions and billions of galaxies everywhere, cooking elements, making stars that are ripe for solar systems. The habitat for life is everywhere.

NEIL deGRASSE TYSON: That's no proof that life itself exists anywhere else in the universe, but Sandy's work does confirm that the elements essential to life as we know it are widespread throughout the cosmos.

SANDRA FABER: The message of the DEEP survey, and all the other information that we're getting, is one beautiful story, a new version of Genesis, a new version of the cosmic myth, only this time it's scientifically based, from the Big Bang to now: Big Bang, formation of galaxies, formation of heavy elements in supernova, sun, Earth, life—one unbroken, great chain of being.

JEFF HESTER: Just in the last few years, we've reached the point that we can start with the origins of the universe, we can end with a conversation among intelligent beings about how things work, and have an awfully good understanding of every step that came in between the two.

DAVID SPERGEL: It was as if we were basically assembling this puzzle, and all of a sudden you look down at the puzzle and you realize you've got it. The pieces are there.

NEIL deGRASSE TYSON: For almost all of human history, the heavens have been beyond our reach. For our ancestors, it was a place where the gods lived, or else simply a vast, untouchable realm of lifeless beauty. But now, the study of cosmic origins tells a different story.

It tells us that the story of life, of us, extends far beyond earth. It tells us that the emergence of the conditions for our kind of life was no accident. Instead, it was a natural outcome of almost 14 billion years of cosmic evolution, a chain of connections that links the birth of the universe to us, right here, right now.

The "Origins" series continues online. On NOVA's Web site, explore the arguments for and against intelligent life in the Milky Way galaxy. Then cast your vote. Find it on pbs.org.

To order this program on VHS or DVD, or the book, Origins: 14 Billion Years of Cosmic Evolution, please call 1-800-255-9424.

NOVA is a production of WGBH Boston. Major funding for NOVA is provided by the Park Foundation, dedicated to education and quality television.

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Major funding for "Origins" is provided by the National Science Foundation, America's investment in the future.

Additional funding is provided by the NASA Office of Space Science, the Alfred P. Sloan Foundation to enhance public understanding of science and technology, and the George D. Smith Fund.

Major Funding for NOVA is also provided by the Corporation for Public Broadcasting and by PBS viewers like you. Thank you.

Broadcast Credits

Origins: Back to the Beginning

Hosted and Narrated by
by Neil deGrasse Tyson
Edited by
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Written, Produced and Directed by
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© 2004 WGBH Educational Foundation
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This material is based upon work supported by the National Science Foundation under Grant No. 9814643. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

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