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NOVA scienceNOW: July 24, 2007

PBS Airdate: July 24, 2007
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NEIL DEGRASSE TYSON (Host/Astrophysicist, American Museum of Natural History): On this episode of NOVA scienceNOW, something new in a 65-million-year-old story, fresh clues about dinosaurs from something no one thought would ever be found...

MARY HIGBY SCHWEITZER: (North Carolina State University/North Carolina Museum of Natural Sciences): When I poked into it, it was spongy, it was flexible and soft tissue.

NEIL DEGRASSE TYSON: ...tissue preserved inside a fossil millions of years old.

MARY HIGBY SCHWEITZER: Nobody else had seen anything like that before.

KRISTI CURRY ROGERS (Science Museum of Minnesota): This is a single cell.

NEIL DEGRASSE TYSON: And that's not all.

KRISTI CURRY ROGERS: It's quite possible that there will be DNA there, as well.

NEIL DEGRASSE TYSON: Speaking of DNA, it's exactly the same in identical twins. So how do you explain it when one gets a dread disease and the other doesn't?

Just look at this. These genetically identical mice may hold a clue.

You have turned off that gene?

RANDY JIRTLE (Duke University Medical Center): That's right.

NEIL DEGRASSE TYSON: It's a whole new view of genetics that suggests why our lifestyle can affect how long we live.

RANDY JIRTLE: You're not necessarily stuck with this. You can alter this.

NEIL DEGRASSE TYSON: Also, it may look like a jumble of random letters, but there's a secret message concealed in this sculpture called "Kryptos."

ELONKA DUNIN (Author, Secret Codes): It's at the center of CIA.

NEIL DEGRASSE TYSON: That's right, the CIA, where for nearly two decades, some of the world's best sleuths have been stumped, trying to crack the secret code.

CHAD COHEN (Correspondent): Hmm, another one to scratch your head on.

ELONKA DUNIN: Yes, there's a lot of "hmms" here.

NEIL DEGRASSE TYSON: It's even become a worldwide phenomenon, as thousands of code breakers try to solve the puzzle. And only the man who designed and built Kryptos knows the answer.

CHAD COHEN: Is it something really simple that people are missing?

JAMES SANBORN (Kryptos Creator): No, I...maybe not...maybe, maybe not.

NEIL DEGRASSE TYSON: All that and more on this episode of NOVA scienceNOW.

Funding for NOVA scienceNOW is provided by the following:

For each of us, there is a moment of discovery. We understand that all of life is elemental. And as we marvel at element bonding with element, we soon realize that when you add the human element to the equation, everything changes. Suddenly all of chemistry illuminates humanity, and all of humanity illuminates chemistry. The human element: nothing is more fundamental, nothing more elemental.

Major funding for NOVA scienceNOW is provided by the National Science Foundation, where discoveries begin. And:

Discover new knowledge, biomedical research and science education. Howard Hughes Medical Institute: HHMI.

Additional funding is provided by the Alfred P. Sloan Foundation, to portray the lives of men and women engaged in scientific and technological pursuit, 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: Hello. I'm Neil deGrasse Tyson, your host for NOVA scienceNOW.

Most of what we know about ancient life—and I'm talking millions of years old—comes from these things, fossils. You know, they're actually rocks. Over time, the bone and tissue has been replaced by minerals. But there's only so much you can learn from a rock. Think about how much more you could learn if, instead of a rock, what you found was the real thing.

Peter Standring met some researchers who've uncovered some rare remains.

PETER STANDRING (Correspondent): Bones tell us almost everything we know about dinosaurs: the fantastic variety of species, their titanic size, their sheer power. The frustrating thing is that there's still so much we'd like to know that dinosaur bones haven't told us. Were they warm-blooded or cold-blooded? How different were they from modern reptiles? To solve these biological questions, today's paleontologists are starting to explore radically new clues from dinosaur skeletons. Kristi Curry Rogers cuts into their bones to examine the pattern of what was once living tissue.

Is it sort of like CSI for dinosaurs?

KRISTI CURRY ROGERS: It can be, sure. Sometimes it's kind of a different method of detective work. We can see, in these cross-sections of bones, evidence of pathology, evidence of dinosaur disease and evidence of dinosaur bones breaking and healing themselves. All of that stuff is available via the inside look at a dinosaur bone.

PETER STANDRING: Analyzing the rock that entombed dinosaur fossils is key to understanding how they were preserved, which is the work of Kristi's husband, geologist Ray Rogers.

RAYMOND ROGERS (Macalester College): And I'm there to try to place the discoveries in context, to try to find clues as to where may be best to look for fossils. We've been pretty lucky in Madagascar.

PETER STANDRING: For the last decade, the African island has offered Ray and Kristi Rogers a spectacular excavation site. They work in an area of remote grasslands where dinosaur bones literally cover the ground, an ancient graveyard where an unusually large number of dinosaurs died and were entombed by mudflows that preserved their bones.

RAYMOND ROGERS: The preservation is unbelievable. The quality of the material is exceptional. This is a piece of bone from the Madagascar locality. It, in many regards, doesn't even look like a fossil; it's unstained. It's very light. It's not heavily, densely filled with minerals. You look at a dinosaur bone in a museum and it's brown, it's black, it's heavy as can be.

PETER STANDRING: Heavy because fossils are no longer hollow bones. Buried in the earth, empty channels inside the bone fill up with minerals, becoming dark and stained, hard as stone. In some cases, the bone tissue itself is completely replaced by minerals. It's difficult to probe dinosaur biology with bones that have turned to rock, but the Madagascar fossils were sealed in a clay-rich mud, preventing many of the chemical changes that happen to most dinosaur bones.

RAYMOND ROGERS: This is typical of the Madagascar material. It's not heavily stained. It's not been invested with iron, with manganese. It doesn't look like a typical fossil. If you didn't know, you might think you're picking up a cow bone today, a bleached cow bone.

KRISTI CURRY ROGERS: I think this piece might be good, or maybe...

PETER STANDRING: The Madagascar bones are so perfectly preserved that Ray and Kristi wondered if they might conceal clues about how these dinosaurs lived, and why so many of them died in the same place. To find out, they turned to their colleague, Mary Schweitzer, a paleobiologist, whose study of ancient cells and tissues might solve the mystery.

MARY HIGBY SCHWEITZER: We know that dinosaurs had to have cells—bone cells, and muscle cells, and gut cells, and brain cells—and that's one of the reasons we can study them, even though they are extinct.

PETER STANDRING: Schweitzer's career defined itself in her native Montana when she was preparing one of the largest skeletons of a Tyrannosaurus rex ever found.

MARY HIGBY SCHWEITZER: I was working on the leg bones. And as I worked, I noticed a bunch of stuff. It was like, you know, "This bone, it's hollow inside." And I was looking at this thing thinking, "This is really interesting."

PETER STANDRING: It was the inside of the T. rex bone that fascinated Schweitzer, who made thin sections out of it. And in these cross-sections of fossilized bone, she saw something that she and everyone else had thought was impossible: round structures that looked like red blood cells, dinosaur blood cells.

MARY HIGBY SCHWEITZER: Inside those channels where the blood vessels would have run were these little round red structures that were all kind of lined up like a train. And they were bright red and translucent. Nobody else had seen anything like that before.

PETER STANDRING: The very idea of blood cells in a 70-million-year-old bone was more than unconventional, it was radical.

DEREK BRIGGS (Peabody Museum of Natural History, Yale University): Nobody was imagining that dinosaurs might have had preserved soft tissues.

PETER STANDRING: Derek Briggs is curator of invertebrate paleontology at the Peabody Museum at Yale University.

So along comes Mary Schweitzer, and she's starting to look inside dinosaur bones and has made this startling discovery about the presence of red blood cells. What was your initial reaction to that?

DEREK BRIGGS: Oh, I think the same reaction as everybody's, that this was totally improbable, she'd perhaps misinterpreted the evidence or was exaggerating the potential for what she was seeing.

PETER STANDRING: So, skeptical, at first?

DEREK BRIGGS: Oh, yeah, definitely.

PETER STANDRING: Paleontology has been around for some time.

DEREK BRIGGS: One of the oldest professions.

PETER STANDRING: One of the oldest professions. Has anybody else that you know of found similar things inside a bone?


PETER STANDRING: Why do you think it didn't occur to anybody?

DEREK BRIGGS: Because we have this clear understanding that part of all biological cycles involves decay. I mean, nature is set up to break down that material and recycle it. So it's just improbable that those kinds of very delicate structures would survive, particularly for millions of years.

MARY HIGBY SCHWEITZER: When you think about it, the laws of chemistry and biology and everything else that we know say that it should be gone. It should be degraded completely.

PETER STANDRING: But Schweitzer kept searching for organic remains where no one had thought to look before. Her mentor is Jack Horner, one of the most famous dinosaur hunters in the world. When his team found another beautifully preserved T. rex in the remote Montana Badlands, the massive leg bone had to be broken in half for transport, and Schweitzer got to test fragments from deep inside the bone.

MARY HIGBY SCHWEITZER: The T. rex bone was filled with a very unique bone tissue. When I turned it, you know, like that, and looked down on it, and saw this tissue that you can see right there in cross-section, I knew what it was.

PETER STANDRING: It's called medullary tissue, and it's what female birds build up inside their bones as a source of calcium for the eggs they lay. All dinosaurs laid eggs, and it made sense to Schweitzer that female dinosaurs produced the same kind of bone tissue. It looks different from the surrounding bone, and it meant the T. rex had to be a mother, expecting a clutch of dinosaur eggs.

MARY HIGBY SCHWEITZER: It was really exciting for me. I thought, "There is nothing in my career that could possibly be cooler than being able to identify the first pregnant T. rex."

PETER STANDRING: No one had ever identified medullary tissue in a dinosaur bone before. But, to be sure, Mary Schweitzer directed her lab assistant to soak the bone sample in an acid solution to reveal its structure so she could study it. What happened next would change the way scientists thought about fossils forever.

JENNIFER WITTMEYER (North Carolina State University): As I was looking in the microscope, the medullary material was no longer hard. And, um, what was left was this curled piece of tissue that I was using forceps to try and flatten out. And when I poked into it, it was, it was spongy. It was flexible and soft tissue.

PETER STANDRING: Flexible tissue? From a 68-million-year-old dinosaur?

MARY HIGBY SCHWEITZER: Blood vessels, transparent, hollow, pliable, flexible branching blood vessels that contained small, round, red microstructures floating in the vessels. I said, "This is not possible. Do it again."

We got another piece of bone, we put it in the solution, we waited two or three or four weeks, looked again...more blood vessels. We must have repeated that with probably 17 or 18 different fragments of bone.

PETER STANDRING: As soon as Schweitzer's discovery of dinosaur soft tissue was published, people thought of one thing: could we get a real life Jurassic Park? No paleontologist believes we could ever get enough ancient DNA to clone a dinosaur. But could fragments of genetic material be extracted from this new tissue?

KRISTI CURRY ROGERS: I think anything is possible. If there are blood vessels and red blood cells preserved in a dinosaur, I think it's quite possible that there will be DNA there as well.

PETER STANDRING: Even without DNA, proteins from soft tissue could begin to answer real mysteries about dinosaur biology: evidence of warm blood versus cold blood, whether the large body size of dinosaurs is linked to large cell size. The Rogers have a theory that dinosaur mass deaths in Madagascar might have been caused by water poisoned by algae. This poisoning event wouldn't show up in hard bone, but they might be able to test the theory with dinosaur blood cells.

RAYMOND ROGERS: This structure...I mean, there's a lot of structure there.


RAYMOND ROGERS: If there's anything in this tissue that Mary finds that actually can trace a toxin, that would be fantastic—things like disease, diets; things like that from soft tissues that you can't extract from hard tissue from true fossil bone.

PETER STANDRING: The hope is that the Madagascar fossils will allow Mary to find more dinosaur tissue. So Ray and Kristi gather fragments of their best preserved fossils. A few days later, the samples arrive at Schweitzer's lab at North Carolina State University. She uses the same technique that yielded soft tissue in the T. rex bone, soaking the fragments in a mild acid that dissolves away the mineral part of the bone. But will she be able to find the same internal structures in Ray and Kristi's fossils?

KRISTI CURRY ROGERS: There's only so much you can know from looking at the outsides of bones, but when there's soft stuff inside, the possibilities become almost endless.

This is a single cell.

PETER STANDRING: Through photos from her microscope, Mary hits the jackpot: pieces of biological history.

MARY HIGBY SCHWEITZER: Now, see, this is really cool. It's what looks like vessels to me, connected together, transparent. And you can see right there. You can see the branch points and stuff.

PETER STANDRING: The Rogers are seeing inside their collection of fossil bone as they've never seen it before...structures that appear to be the vessels that once carried blood inside a dinosaur's body.

MARY HIGBY SCHWEITZER: This is hooked together. There's a transparent region.

RAYMOND ROGERS: Yeah, it's a tube with stuff inside of it.

PETER STANDRING: Branching, hollow, organic material that scientists thought could never be preserved in a dinosaur fossil.

KRISTI CURRY ROGERS: That's amazing, that this is from 65-, 70-million-year-old bone.

PETER STANDRING: It's too early for these structures to reveal details like dinosaurs dying from poisoned water, but dinosaur soft tissue opens a door that no scientist thought even existed until Schweitzer's work changed that assumption.

DEREK BRIGGS: There's little doubt in my mind that what she has discovered are internal structures in dinosaur bone. And we may look back and say, "Well, this sort of approach to looking at fossil vertebrate biology has revolutionized the field." But we won't know that for some time yet.

RAYMOND ROGERS: To get in there and to find soft tissues, to find blood vessels, to find cells, it is an opportunity to go to places that we never thought we would be venturing just 10 years ago.


CHEERFUL NEIL DEGRASSE TYSON: Did you ever notice that if you get to know two identical twins, they might look alike, but they're always subtly different?


CHEERFUL NEIL DEGRASSE TYSON: As they get older, those differences can get more pronounced. Two people start out the same but their appearance and their health can diverge. For instance, you have more gray hair.

CANTANKEROUS NEIL DEGRASSE TYSON: No. No, I don't. Identical twins have the same DNA, exact same genes.


CANTANKEROUS NEIL DEGRASSE TYSON: And don't our genes make us who we are?

CHEERFUL NEIL DEGRASSE TYSON: Well they do, yes, but they're not the whole story. Some researchers have discovered a new bit of biology that can work with our genes or against them.

CANTANKEROUS NEIL DEGRASSE TYSON: Yeah, you're heavier, and I'm better looking.


NEIL DEGRASSE TYSON: Imagine coming into the world with a person so like yourself, that for a time you don't understand mirrors.

CONCEPCIÓN: As a child, when I looked in the mirror I'd say, "That's my sister." And my mother would say, "No, that's your reflection!"

NEIL DEGRASSE TYSON: And even if you resist this cookie-cutter existence, cultivate individual styles and abilities—like cutting your hair differently, or running faster—uncanny similarities bond you together: facial expressions, body language, the way you laugh—or dress for an interview, perhaps, when you hadn't a clue what your sister was going to wear. The synchrony in your lives constantly confronts you.

CLOTILDE: When I see my sister, I see myself. If she looks good, I think, "I look pretty today." But if she's not wearing makeup, I say, "My god, I look horrible!"

NEIL DEGRASSE TYSON: It's hardly surprising because you both come from the same egg. You have precisely the same genes. And you are literally clones, better known, as identical twins.

But now, imagine this: one day, your twin, your clone, is diagnosed with cancer. If you're the other twin, what can you do except wait for the symptoms?

CLOTILDE: I have been told that I am a high risk for cancer. Damocles' sword hangs over me.

NEIL DEGRASSE TYSON: And yet, it's not uncommon for a twin, like Ana Mari, to get a dread disease, while the other, like Clotilde, doesn't. But how can two people so alike, be so unalike?

Well, these mice may hold a clue. Their DNA is as identical as Ana Mari and Clotilde's despite the differences in their color and size. The human who studies them is Duke University's Randy Jirtle.

So, Randy, I see here you have skinny mice and fat mice. What have you done in this lab?

RANDY JIRTLE: Well, these animals are actually genetically identical.

NEIL DEGRASSE TYSON: The fat ones and the skinny ones?

RANDY JIRTLE: That's correct.

NEIL DEGRASSE TYSON: Because these are huge.

RANDY JIRTLE: They're huge.

NEIL DEGRASSE TYSON: Can we weigh them and find out?

RANDY JIRTLE: Sure. So if you take this...

NEIL DEGRASSE TYSON: It looks like they can barely walk.

RANDY JIRTLE: They can't walk too much. They're not going to be running very far. So that's about 63 grams.


RANDY JIRTLE: Let's look at the other one.

NEIL DEGRASSE TYSON: So it's half the weight.


NEIL DEGRASSE TYSON: This gets even more mysterious when you realize that these identical mice both have a particular gene, called agouti, but in the yellow mouse it stays on all the time, causing obesity.

Just look at this.

So what accounts for the thin mouse? Exercise? Atkins? No, a tiny chemical tag of carbon and hydrogen, called a methyl group, has affixed to the agouti gene, shutting it down. Living creatures possess millions of tags like these. Some, like methyl groups, attach to genes directly, inhibiting their function. Other types grab the proteins, called histones, around which genes coil, and tighten or loosen them to control gene expression. Distinct methylation and histone patterns exist in every cell, constituting a sort of second genome, the epigenome.

RANDY JIRTLE: Epigenetics literally translates into just meaning "above the genome." So if you would think, for example, of the genome as being like a computer, the hardware of a computer, the epigenome would be like the software that tells the computer when to work, how to work, and how much.

NEIL DEGRASSE TYSON: In fact, it's the epigenome that tells our cells what sort of cells they should be. Skin? Hair? Heart? You see, all these cells have the same genes. But their epigenomes silence the unneeded ones to make cells different from one another. Epigenetic instructions pass on as cells divide, but they're not necessarily permanent. Researchers think they can change, especially during critical periods like puberty or pregnancy.

Jirtle's mice reveal how the epigenome can be altered. To produce thin, brown mice instead of fat, yellow ones, he feeds pregnant mothers a diet rich in methyl groups to form the tags that can turn genes off.

RANDY JIRTLE: And I think you can see that we dramatically shifted the coat color and we get many, many more brown animals.

NEIL DEGRASSE TYSON: And that matters because your coat color is a tracer, is an indicator...

RANDY JIRTLE: That's correct.

NEIL DEGRASSE TYSON: ...of the fact that you have turned off that gene?

RANDY JIRTLE: That's right.

NEIL DEGRASSE TYSON: This epigenetic fix was also inherited by the next generation of mice, regardless of what their mothers ate. And when an environmental toxin was added to the diet instead of nutrients, more yellow babies were born, doomed to grow fat and sick like their mothers.

It seems to me, this has profound implications for our health.

RANDY JIRTLE: It does, for human health. If there are genes like this in humans, basically, what you eat can affect your future generations. So you're not only what you eat, but potentially what your mother ate, and possibly even what your grandparents ate.

NEIL DEGRASSE TYSON: So how do you go to humans to do this experiment, when you have these mice, and they're genetically identical on purpose?

RANDY JIRTLE: That's right.

NEIL DEGRASSE TYSON: So, who is your perfect lab human?

RANDY JIRTLE: Well, then we look for identical humans, which are identical twins.


And that brings us to the reason why we're showing you Spanish twins. In 2005, they participated in a groundbreaking study in Madrid. Its aim? To show just how identical, epigenetically, they are or aren't.

MANEL ESTELLER (Spanish National Cancer Center): One of the questions of twins is, "If my twin has this disease, I will have the same disease?" And genetics tell us that there is a high risk of developing the same disease. But it's not really sure they are going to have it, because our genes are just part of the story. Something has to regulate these genes, and part of the explanation is epigenetics.

NEIL DEGRASSE TYSON: Esteller wanted to see if the twins' epigenomes might account for their differences. To find out, he and his team collected cells from 40 pairs of identical twins, age three to 74, then began the laborious process of dissolving the cells until all that was left were wispy strands of DNA, the master molecule that contains our genes.

Next, researchers amplified fragments of the DNA, until the genes themselves became detectable. Those that had been turned off epigenetically appear as dark pink bands on the gel. Now, notice what happens when the genes from a pair of twins are cut out and overlapped.

The results are far from subtle, especially when you compare the epigenomes of two sets of twins that differ in age. Here, on the left, is the overlapped DNA of six-year-old Javier and Carlos. The yellow indicates where their gene expression is identical.

On the right, is the DNA of 66-year-old Ana Mari and Clotilde. In contrast to the younger twins, hardly any yellow shines through. Their epigenomes have changed dramatically.

The study suggests that, as twins age, epigenetic differences accumulate, especially when their lifestyles differ.

MANEL ESTELLER: One of the main findings of our research is that epigenomes can change in function of what we eat, of what we smoke, of what we drink. And this is one of the key differences between epigenetics and genetics.

NEIL DEGRASSE TYSON: As the chemical tags that control our genes change, cells can become abnormal, triggering diseases like cancer. Take a disorder like MDS, cancer of the blood and bone marrow. It's not a diagnosis you'd ever want to hear.

SANDRA SHELBY: When I went in, he started patting my hand, and he was going, "Your blood work does not look very good at all," and that I had MDS leukemia, and that there was not a cure for it. And, basically, I had six months to live.

NEIL DEGRASSE TYSON: Was epigenetics the reason? Could the silencing of critical genes turn normal cells into cancerous ones? It's scary to think that a few misplaced tags can kill you. But it's also good news, because we've traditionally viewed cancer as a disease stemming solely from broken genes. And it's a lot harder to fix damaged genes than to rearrange epigenetic tags. In fact, we already have a few drugs that will work. Recently, Sandra Shelby and Roy Cantwell participated in one of the first clinical trials using epigenetic therapy.

JEAN PIERRE ISSA (M.D. Anderson Cancer Center): The idea of epigenetic therapy is to stay away from killing the cell. Rather, what we are trying to do is diplomacy, trying to change the instructions of the cancer cells, reminding the cell, "Hey, you're a human cell. You shouldn't be behaving this way." And we try to do that by reactivating genes.

SANDRA SHELBY: The results have been incredible, and I didn't have really any horrible side effects.

ROY CANTWELL: I am in remission. And going in the plus direction is a whole lot better than the minus direction.

NEIL DEGRASSE TYSON: In fact, half the patients in the trial are now in remission. But, while it maybe easier to fix our epigenome than our genome, messing it up is easier, too.

RANDY JIRTLE: We've got to get people thinking more about what they do. They have a responsibility for their epigenome. Their genome they inherit. But their epigenome, they potentially can alter, and particularly that of their children. And that brings in responsibility, but it also brings in hope. You're not necessarily stuck with this. You can alter this.


NEIL DEGRASSE TYSON: Most good spy stories have a secret message, usually in code, but a master spy can always crack it. Today, code breaking involves complex mathematics and relies on powerful algorithms. But even with the best technology, there's one coded message no one has been able to crack. It's ten feet tall and sitting in plain view, in the backyard of the CIA.

Correspondent Cohen, Chad Cohen, is on the case.

CHAD COHEN: Of all the secrets hidden at the highly-secured CIA headquarters in Langley, Virginia, you may be looking at one of the strangest. Meet Kryptos. It's a copper monolith inscribed with nearly two thousand very random-looking characters, but there's a message here, if you can break the code. And despite countless attempts since Kryptos' 1989 installation, that has yet to be done.

JAMES SANBORN: Now, you're the Central Intelligence Agency, right? You're supposed to be very intelligent. Everybody there is intelligent, right? You don't have anything pulled over your eyes.

CHAD COHEN: Well that's at least what we all like to believe. But with Kryptos, that's exactly what Jim Sanborn has done. And he is not the world's most sophisticated cryptographer. In fact, Sanborn is not a cryptographer at all. The mastermind behind Kryptos is an artist, if an unconventional one. His workspace looks more science lab than art studio.

JAMES SANBORN: I worked with lodestones, compasses, the Earth's magnetic field, the Coriolis force. These were natural forces that were invisible. Those kinds of things fascinated me, and I set about to try to make those things visible for people.

CHAD COHEN: When the CIA was looking for a sculpture to grace the courtyard of their new headquarters building, Sanborn wanted to design something that would stay invisible, a secret code. So how does an artist craft a message that the best code breakers in the world can't crack?

ED SCHEIDT (Former CIA Cryptologist): I set the codes out for him, which means he didn't have to know the mathematics of it.

CHAD COHEN: Sanborn found help in the former chairman of the CIA cryptographic center, Ed Scheidt, who gave Jim a crash course in Cryptography 101.

ED SCHEIDT: Well classical cryptography—and it's been defined this way—includes substitution and it includes transposition.

CHAD COHEN: For substitution, take one letter or word and swap it for another; transposition: keep the letters the same, just systematically mix them up. Pretty straightforward tricks and yet they've been stumping would-be code breakers for thousands of years.

Julius Caesar came up with a system based on substitution to send secret messages to his generals on the battlefield. It's called the Caesar cipher.

ED SCHEIDT: A letter is substituted with another letter. By laying two alphabets on top of each other, and shifting one of them over a set number of places, you get a whole new alphabet.

CHAD COHEN: The word "film" in this case, now becomes "ilop," complete gobbledygook if intercepted by any enemy. But if you know how many spaces to shift the alphabet over, it's clear as day.

The codes have gotten more complicated through the ages. Nazi Germany's enigma machine, for example, which Hitler used successfully for years before allied code breakers cracked it, employed a mechanical rotor system. Ultimately, it just created elaborate substitutions.

Transposition ciphers have their place in history too. To send secret messages to his army, General Ulysses S. Grant didn't substitute letters he just carefully mixed them all up.

Sanborn also employed this technique in Kryptos using pen and paper.

JAMES SANBORN: So this is the plain text, this is the way it's written out in English.

CHAD COHEN: By writing the message on a grid, and transposing it to different positions on a new grid, it becomes unreadable to someone trying to intercept it. And the more times you do it, the more complex it can get.

JAMES SANBORN: So it can get very complicated.

CHAD COHEN: Very quickly, it seems.

JAMES SANBORN: Very quickly.

CHAD COHEN: Complicated, maybe, to a code breaker, but it's very simple to the intended recipient. If the code is meant for you, you don't have to break it. Because when two parties want to communicate via cipher, they agree ahead of time on the specific rules of the system. With transposition, you might agree on how many rows you'd use or how many times the chart is flipped. With substitution, you might agree on how many spaces to offset the alphabet.

To make Kryptos, Sanborn took both these techniques, used them to encode four distinct messages, and cut them into copper.

JAMES SANBORN: Every letter was cut out with a jigsaw, and it took two and a half years of cutting to do it.

CHAD COHEN: Secure as the CIA may be, it wasn't long before Kryptos went mainstream. Through internet message boards, Web sites, hacker conventions, Kryptos has become a phenomenon.

ELONKA DUNIN: We have a group of about a thousand people around the world that are brainstorming this very, very heavily.

CHAD COHEN: Elonka Dunin, whose Web site has had millions of hits from would-be crackers, is generally considered to be the leading Kryptos expert in the world, even Sanborn says so. But she's only seen the sculpture up close once.

ELONKA DUNIN: Well, because we can't get in to see Kryptos at CIA, because it's at the center of CIA.

CHAD COHEN: So, Elonka took me here, to the Hirshhorn Museum in Washington D.C. to see a similar Sanborn piece, called Antipodes.

ELONKA DUNIN: So, this is the next best thing. The order of the letters is identical. The punctuation is the same. Part one starts here, where it says, where it says "emufphz" decrypts to the letters "b, e, t, w, e, e, n."

CHAD COHEN: Between? Since when does "emufphz" resemble anything like the word "between?" Well, since Parts One, Two and Three of Kryptos were cracked in 1999.

JIM GILLOGLY (Code Breaker): It all looks like pretty much garbage to the untrained eye.

CHAD COHEN: And here's the guy who did it, L.A. computer scientist Jim Gillogly.

JIM GILLOGLY: Part of the reason it's developed a cult following is that I was able to crack it and expose it to the world. So people are able to say, "Look, some of it really is solvable. It's not just a mass of garbage letters."

CHAD COHEN: Gillogly's programs combine algorithms with rules of thumb for English grammar and spelling. The computer tries millions of different character combinations and throws away the ones that look like nonsense. He's cracked many codes in his life, but he always starts the same way, with what's called a frequency count.

Simply put, he counts. He counts up all the letters in the text and sees how often each one occurs. That works because, in any language, certain letters always show up more often than others. Whether it's a cookbook, a flight manual, or a page from Hamlet, the frequency of each letter will always stay about the same.

So, in English, on average, of all the letters in any given bit of text, Es make up over 12 percent, while Qs occur much less frequently, less than .2 percent.

When Gillogly studied the first two parts of Kryptos, he noticed there were just as many Qs as there were Es. It was a tip-off that they were probably standing in for, or substituting for, more common letters. Gillogly ran his program on it.

Okay, so you typed this stuff in, you typed in that code, and, boom, this came out.

JIM GILLOGLY: This came out.

CHAD COHEN: But as the solution for Parts One and Two came out on Jim Gillogly's screen, the mystery just got deeper.

JIM GILLOGLY: "Between subtle shading and the absence of light, lies the nuance of illusion."

JAMES SANBORN: "It was totally invisible. How's that possible? They used the Earth's magnetic field. The information was gathered and transmitted underground to an unknown location."

JIM GILLOGLY: This was his last message.

CHAD COHEN: Hmm, another one to scratch your head on, right?

ELONKA DUNIN: Yes, there's a lot of "hmms" here, definitely.

CHAD COHEN: There was nothing to help reveal the meaning of the sculpture, just the ambiguous words of Jim Sanborn; not that it mattered to the man who actually cracked it.

JIM GILLOGLY: For myself, personally, I don't care quite so much about what was being hidden as how it was hidden.

CHAD COHEN: Gillogly quickly discovered that Part Three of Kryptos was hidden in a radically different way. This one had lots of E's and only one Q, just like it would be in English.

JIM GILLOGLY: I could tell that it was a transposition cipher because the frequency of the letters was identical to the frequency in English.

CHAD COHEN: Remember what Sanborn was doing in his studio? The transposition he did with that graph paper? Gillogly created a computer program that undid it, and eventually he cracked Part Three of Kryptos as well.

This section was recognizable, taken right out of archaeologist Howard Carter's notebook, describing the moment he first opened King Tut's tomb.

ELONKA DUNIN: "Slowly, slowly, desperately slowly, the remains of passage debris that encumbered the lower part of the doorway was removed."

JIM GILLOGLY: "And then, widening the hole, a little I inserted the candle and peered in. The hot air escaping from the chamber caused the flame to flicker, but presently details of the room within emerged from the mist."

CHAD COHEN: Diary excerpts from famous explorers, mysterious allusions to light and dark. Even when Sanborn's words are put in the right order, they are cryptic, to say the least.

Between "subtle shadings," and the Howard Carter, what does it mean?

ELONKA DUNIN: Well, they all tend to have a common theme of things hidden, things underground, things concealed from sight. So that theme may be something that is going to give us a clue towards Part Four.

CHAD COHEN: Part Four is made up of the final 98 letters on the sculpture, and only by breaking that last piece will the true message of Kryptos be revealed. But so far, it has proven impervious to all the techniques of would-be code breakers.

ELONKA DUNIN: Part Four is hard, well, number one, because it's very short. It's only 97 or 98 characters. When cryptanalysts are working on a code, we generally have a large amount of cipher text to work with. Then you're able to look for the very subtle mathematical patterns, which is what takes a code apart.

CHAD COHEN: Is it something really simple that people are missing?

JAMES SANBORN: No, I...maybe not...maybe, maybe not.

CHAD COHEN: And he may have had one more trick up his sleeve, something called concealment.

JIM GILLOGLY: It could be a matter of obfuscating the language before starting to encrypt.

ELONKA DUNIN: Ed Scheidt has said that he used a little bit of concealment on Part Four, but we don't know what that means.

CHAD COHEN: A message can be concealed in various ways before enciphering it, to make it even harder to break.

ED SCHEIDT: The first challenge then is, well, what masking technique was used?

CHAD COHEN: Techniques like removing all the vowels first, or spelling the message phonetically, can radically undermine the code-breaking methods. So, it may still be a long time before anyone experiences the thrill of cracking all of Kryptos. Even Ed, who taught Jim how to make code, doesn't know the solution, which makes Jim Sanborn the only person on earth who does. And he isn't dropping any hints.

It wouldn't help to just kind of get it out there?

JAMES SANBORN: Unburden myself?

CHAD COHEN: Lighten your load?

JAMES SANBORN: Oh, no, no, no, no. Unh unh. I really like your program, but I'm sorry.


NEIL DEGRASSE TYSON: Hey, that's me, back when I was in graduate school, at an astrophysics conference overseas. And that's me as a smiley post-doc at Princeton University with one of my buddies from the math department, Arlie Petters.

Today, Arlie is one of the world's leading experts in what happens to light during its long journey across the universe. But Arlie's own journey to becoming a scientist, although not quite as long, is just as interesting.

When Arlie Petters comes home to his native Belize everybody wants his attention, from kids...

ARLIE PETTERS (Duke University): So you must put them back so they could grow big, right? The way you can grow big.

NEIL DEGRASSE TYSON: the ministers. I don't mean clergy. I'm talking about the Minister of Education...

FRANCIS FONSECA (Minister of Education, Belize): We're very, very proud of Dr. Petters.

NEIL DEGRASSE TYSON: ...and the Prime Minister.

SAID MUSA (Prime Minister, Belize): He represents, in my mind, what a Belizean can do.

NEIL DEGRASSE TYSON: Arlie is a national hero. He never raises his voice or does anything to draw attention to himself; he lets his ideas do all the talking.

Born and raised in the Caribbean sun, he has always had an intimate relationship with light.

ARLIE PETTERS: Light is a great messenger, traveling billions and billions of light years, carrying secrets.

NEIL DEGRASSE TYSON: Arlie knows all about long and arduous journeys. His began in Belize, but it took him to Duke University, where he is a member of both the physics and math departments, leading the way in the field of gravitational lensing.

ARLIE PETTERS: You could think of the lens in my glasses as an example of a gravitational field, in that light passes through it. It may get deflected, it may even be slowed down, and this impact on the light ray comes under the fancy name, gravitational lensing.

DAVID SPERGEL (Princeton University): A lens that has an effect a lot like gravitational lensing is the surface of a pool. Light...if you've ever looked at a nice, sunny day, at the bottom of a pool, what you see is light comes in, gets deflected by the ripples on the pool and gets focused. We call that pattern "caustics."

ARLIE PETTERS: The word caustic means burning bright. If you look in your coffee cup, you're going to see one of the most common examples of caustics. Where you have two arcs that abut each other into a sharp point called a cusp.

DAVID SPERGEL: The same thing happens on a cosmological scale. Let's say you're looking at a distant galaxy. And light from that galaxy has to pass through other galaxies, through clusters.

NEIL DEGRASSE TYSON: How that light bends and careens through space tells us a lot about what we can't see, and that's most of what's out there.

ARLIE PETTERS: One of the deep mysteries about our universe is that about 96 percent of it, we don't really know what it is.

DAVID SPERGEL: These gravitational lensing effects tell us a great deal about the physics of the universe because instead of telling us about what's going on with the light, we can see what's going on with the matter.

NEIL DEGRASSE TYSON: Arlie boldly went where no mathematician had gone before. He devised a single mathematical formula that could reliably measure how the gravity of many objects, such as galaxies and black holes, shape light as it passes by. His calculation will help astrophysicists determine the structure and environment of objects they can't see.

ARLIE PETTERS: We could then think of gravitational lensing as a map, indeed.

NEIL DEGRASSE TYSON: Arlie's pioneering work has won him many awards. And he's received great notice right here on planet Earth. He's the first African-American to earn tenure in the math department at Duke University.

ARLIE PETTERS: We have a very long way to go. In mathematics for example, you have an average of about just one percent of Ph.D.s going to African-Americans, each year, each year. And that is dismal.

NEIL DEGRASSE TYSON: But Arlie understands how circumstances can interfere with learning. He was born in the small Central American country of Belize. He grew up poor in the city of Dangriga. You could count the telephones in his neighborhood on one hand, yet 6-year-old Arlie carried around a makeshift briefcase.

ARLIE PETTERS: I got a lot of pleasure just studying for hours and hours.

BERNICE WAIGHT (Arlie Petters' Grandmother): Sometimes I would have to tell him to go out and with the other boys. He would go out for a few moments and come right back.

NEIL DEGRASSE TYSON: When he was a teenager, his mother summoned him to live with her in Brooklyn.

ARLIE PETTERS: That was quite a shock for me. And the first thing you had to do was to get muscles. And you had to know how to fight.

NEIL DEGRASSE TYSON: Arlie began Hunter College, but family friction left him without a home. Ready to give up and go back to Belize, he made one last desperate attempt to stay in school. He showed up on the doorstep of Jim Wyche, head of a minority fellowship program.

JIM WYCHE (Hunter College, 1980–1990): And before I could get the key in, he jumped up out of, obviously, a dead sleep and said to me, very groggily, he said, "Are you Dr. Wyche?" I said, "Yes, sir, I am."

ARLIE PETTERS: And I told him my situation.

JIM WYCHE: It was very clear that he had done some research.

ARLIE PETTERS: And I said, "I would give you my transcript. And I tell you this: I will not let you down."

NEIL DEGRASSE TYSON: Time and again, Arlie Petters has defied gravity.

ARLIE PETTERS: It must have been within a couple of weeks or so, Jim said, "You have the scholarship." And he said, "Not only that, we are making arrangements for you to move into Hunter College dorms."

And I couldn't believe it. It was like a miracle, yeah?

NEIL DEGRASSE TYSON: Arlie made the best of the help he received. He graduated from Hunter College. This is his celebration dinner.

ARLIE PETTERS: We are the graduating seniors.


ARLIE PETTERS: Dr. Wyche. Yeah!

NEIL DEGRASSE TYSON: He went on to MIT and then taught at Princeton University, before arriving at Duke.

ARLIE PETTERS: You know, I was blessed to have had many people help me along my path in life. And so, in a sense, I see myself as playing the role of sharing with others the point of view of people that are struggling.

NEIL DEGRASSE TYSON: These days, Arlie is trying to fulfill what may be his greatest vision of all. He has gone back to Dangriga, where light and caustics are plenty, but resources can be thin. Arlie has gone back to give back.

Amidst the wooden houses, on roads shared by ducks and SUVs, Arlie has created the Petters Research Institute, a place where kids from all over the country, kids like Arlie, can come to excel in math and science and life.

ARLIE PETTERS: It allows you to develop thinking skills. It allows you to wonder about great things you want to do in life, aspirations. And that was very special to me.

NEIL DEGRASSE TYSON: He has created a haven for them. It's a place where they don't have to worry about creature comforts or meals, just equations.

GIRL: I'm just glad that he actually recognized the country he came from.

BOY: He's trying to help out Belize.

BOY: One day I'd like to be like him, and try to give back to my community.

NEIL DEGRASSE TYSON: And he's helped to develop a curriculum to improve math and science education across the entire country, as Belize puts its hope in technology as an economic alternative to tourism.

SAID MUSA: Science and technology is where it's at in the world of tomorrow. And we have to get there. So the future is there for us. And Arlie represents that future.

NEIL DEGRASSE TYSON: Belize has put a lot of hope in the quiet kid from Dangriga who made it, then made it back.

ARLIE PETTERS: If I can get a child to be charged up and to believe in himself, to believe in herself, that they can do great things in life...whenever I see that I've accomplished to have that spark go off in a child, those are the things I am most proud of.

NEIL DEGRASSE TYSON: And now for some final thoughts on unsolved problems.

Everybody loves puzzles. They're fun, they're challenging, and you feel good when you succeed. These emotions drive the ambitions of children and scientists alike. What all puzzles have in common is that somebody else invented the rules.

But imagine trying to understand a simple game of poker between two people, but you don't know in advance how the game works. All you're allowed to do is silently observe.

Some events are common and relatively easy to figure out. Pair of 10s beats a pair of sevens. But what are jacks? And what role do jokers play? What are aces? Why can a pair of aces beat all other pairs when the numerical value of an ace is just one?

And how is it that sometimes, some people who have no consecutive cards, no matched numbers, and no matched suits, walk away with all the money?

Now consider the cosmos. It brims with mysteries. And, sure enough, it comes with no instruction manual, no tablet in the sky telling us how things ought to work. By this reckoning, the greatest puzzles there ever were, or will be, are the laws of the universe, those that we struggled to figure out in the past, and those that continue to elude the cleverest among us.

And that is the cosmic perspective.

And now, we'd like to hear your perspective on this episode of NOVA scienceNOW. Log on to our website and tell us what you think. You can watch any of these stories again or listen to podcasts, hear from experts or even take our survey. Find us at That's our show. We'll see you next time.

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For each of us, there is a moment of discovery. We understand that all of life is elemental. And as we marvel at element bonding with element, we soon realize that when you add the human element to the equation, everything changes. Suddenly all of chemistry illuminates humanity, and all of humanity illuminates chemistry. The human element: nothing is more fundamental, nothing more elemental.

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Edited by
Stephen Mack

Produced and Directed by
Dean Irwin


Produced, Directed and Edited by
Sarah Holt


Edited by
David Chmura

Produced by
Win Rosenfeld

Arlie Petters

Edited by
Robe Imbriano & David Chmura

Produced and Directed by
Carla Denly & Robe Imbriano

NOVA scienceNOW

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Neil deGrasse Tyson

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Archival Material
Arlie Petters
The Belize Times
European Space Agency
Frank Summers/Space Telescope Science Institute
Great Belize Productions Ltd. – Channel 5
Les Todd/Duke University
M. Kornmesser and L.L. Christensen/Hubble European Space Agency Information Centre
Observatories of the Carnegie Institution of Washington

Special Thanks
Hirshhorn Museum and Sculpture Garden
Hrana Janto
International Spy Museum
Museum of the Rockies

Neil deGrasse Tyson is director of the Hayden Planetarium in the Rose Center for Earth and Space at the American Museum of Natural History.

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This material is based upon work supported by the National Science Foundation under Grant No. 0229297.  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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