Outside James A. Yorke's office, out there in the big, crazy world, chaos is erupting all over: Palestinian gunmen shoot four Jewish seminarians in the West Bank. Suicide bombers kill more than 80 people in Chechnya. A mysterious virus sickens 75 more cruise ship passengers in Florida. North Korea expels U.N. nuclear inspectors. And an alien-worshiping cult announces that it has cloned a human being.

But in here, in Yorke's office at the University of Maryland's Computer and Space Sciences Building, the chaos is under control. The chaos is right where it's supposed to be -- hanging from the wall in the hallway.

Yorke strolls down the hallway pointing to the chaos. In one picture, chaos looks like butterfly wings. In another, chaos looks like a zebra skin. In another, it looks like a swarm of sperm racing to create yet another chaotic human life.

Using mathematical formulas, Yorke maps chaos on his office computer. When the chaos makes an interesting picture, he prints it out and hangs it on the wall.

"They're called strange attractors," he says. "Or chaotic attractors."

Yorke knows chaos. He's Mr. Chaos. He's Dr. Chaos. He's your go-to guy on chaos issues. He's a 61-year-old math professor, but he's also a high-powered honcho in the world of chaos studies. He's the guru of chaos theory. In fact, he's the guy who named chaos theory.

Two weeks ago, Yorke's groundbreaking work in chaos was rewarded with one of science's highest honors -- the Japan Prize. He shares the prize -- and the $412,000 prize money -- with Yale mathematician Benoit Mandelbrot, who is another major mojo in the chaos biz.

"Dr. Yorke has found the universal mechanism underlying non-linear phenomena," the Japan Prize citation reads. "He named it 'chaos' and he has elucidated its properties mathematically. He has played a leading role in further development of research into chaos, including its controls and applications."

Anyone who stares chaos in the eye for a living learns humility, and Yorke is eager to share credit for the award.

"When they picked me, they were also picking my collaborators," he says. Then he pauses and smiles impishly. "Except the collaborators don't get any money."

Yorke is proud of Maryland's chaos team. It is, he says, a world-class chaos team: "In U.S. News & World Report a few years ago, we were tied with the University of Texas at Austin in chaos."

He's not kidding. In 1999, the magazine really did rate Maryland as tied with Texas as the nation's best collegiate chaos team.

Yorke scurries over to his computer keyboard, which sits atop a table, unattached to anything. He taps on the keys and -- presto! -- the white blackboard on the wall becomes a computer screen.

"Watch this," he says, grinning.

He types the word "chaos" into the Google search engine and clicks on "Go." A moment later, the results appear: 4,180,000 matches. And the very first one is "Chaos at Maryland."

"Look at that!," he says. "We're number one!"

He clicks on "Chaos at Maryland" and his chaos team's logo fills his screen -- "Chaos UMD" sits in a swirl of pink that sits in a swirl of blue.

"Welcome to the Chaos Group at the University of Maryland at College Park!" the text reads. "Chaos is a multidisciplinary science . . ."

As Yorke taps away on his keyboard, one of his grad students, Mike Roberts, trudges into the room, looking haggard and harried. "Do you have the extender cables for the monitor?" he asks.

Yorke bends down, pulls out some cables and hands them to Roberts.

"We're working on a project," Yorke explains. "We're trying to figure out what the rat genome sequence is."

"We're literally in a rat race," Roberts says.

"We're not the official guys doing it," Yorke explains, "but we hope our results are better than theirs. And we think they will be."

But problems have arisen in the rat race. Chaos has reared its ugly head.

"There's a big push to get this thing done," Yorke says. "And the computers crash. And now, they're cleaning the asbestos out of the ceilings and they're closing down our computers."

It's frustrating when chaos bedevils an all-American chaos team. Yorke sighs, then utters a statement that pretty much sums up his views on chaos:

"It goes on and on."

Dr. Chaos looks a bit like Santa Claus.

He has a white beard and a big potbelly and he's wearing an ancient red sweater that looks like it might have taken a few trips down a chimney. He's also wearing red socks under his white sneakers. He always wears red socks under his sneakers -- even at his daughter's wedding.

Yorke lives in what he calls "a cheap townhouse" in Columbia with his wife, Ellen, who is a medical physicist. They met as undergraduates at Columbia University, then moved to the University of Maryland for graduate work in 1963. Yorke earned his doctorate in mathematics in 1966, then became a professor at the university's interdisciplinary Institute for Physical Sciences and Technology.

He quickly earned a reputation as a man with an unpredictable mind. "He thinks very unconventionally," says Edward Ott, a professor of physics and electrical engineering at the university, who has collaborated with Yorke. "When I'm talking to him in the hall sometimes, he'll say something that seems completely bizarre to me. Then I'll go away and I'll think, 'Hey, that was very good.' "

In 1975, Yorke published the math paper that made him famous. It was called "Period Three Implies Chaos," and it gave a name to the emerging new field that was thereafter known as chaos theory.

In his best-selling 1987 book, "Chaos: Making a New Science," author James Gleick summed up the revolutionary effect of Yorke's paper: "Yorke had offered more than mathematical result. He had sent a message to physicists: Chaos is ubiquitous; it is stable; it is structured."

There. That explains it, right? No? You're still just a wee bit confused?

That's okay. Yorke says he can explain chaos to anybody, even a newspaper reporter who is intimately familiar with chaos in his personal life but is, alas, utterly ignorant of chaos's mathematical and theoretical underpinnings.

"Chaos deals with very complicated kinds of behavior," Yorke says.

He bounds across the office to his big L-shaped desk. On one corner, a C-clamp holds a metal contraption to the desktop. It's a pendulum. A double pendulum, a pendulum within a pendulum. He gives it a spin. The top half circles clockwise while the bottom half spins counter-clockwise.

"You see -- the motion gets pretty complicated," he says.

Indeed it does. The pendulum slows down, looks like it's about to stop, then starts spinning faster.

"It doesn't have a regular pattern," Yorke says. "If you spin it again, it will do something different."

The pendulum keeps flipping, spinning, slowing down, speeding up.

"This is what chaos is," Yorke says. "It's predictable in the short run but not in the long run. Chaos is about lack of predictability, basically. Obviously, the spin of the pendulum is determined by physical laws, but it's very hard to predict because very small changes in the spin cause very big changes in the output."

The pendulum keeps flipping, looking like a pair of amazingly agile acrobats spinning in tandem. Yorke reaches over and grabs it. He holds it up vertically, just a hairbreadth away from perpendicular to the desktop. Then he lets it go.

"See, you put it a little bit to one side and it falls one way," he says. "Put it a little bit to the other side, and it falls the other way. So a little bit of difference in the angle produces a huge difference in the way it's going to go."

That's the essence of chaos theory -- a tiny change now can lead to huge changes later.

"We all know that a small perturbation in our lives can produce big perturbations," he says. "You get a flat tire, so you lose your job, so you get evicted."

As one of chaos theory's most famous metaphors puts it: A butterfly flapping its wings in China can cause a hurricane in Florida.

"In fact," says Yorke, "if there's one butterfly that you don't know about, that alone would make it impossible to predict the weather into the distant future -- one butterfly." He smiles. "And there's always going to be one butterfly."

It's not just butterflies you have to worry about, either. It's also the pebbles on Mars.

"The gravitational field on Mars has a near-infinitesimal effect on weather on Earth," he says. "If a pebble rolls down a hill on Mars, that will eventually affect the weather on Earth, thus making it unpredictable. That's the way chaos works."

This mind-bogglingly abstruse theory was, Yorke reveals, once dramatized in an episode of "The Simpsons."

"If you watch 'The Simpsons,' " he says, smiling, "you know that if you go back to the time of the dinosaurs using time travel and you step on a bug, then when you come back to the present, the whole world will have changed."

Suddenly, Roberts walks back into the room, looking even more haggard and harried than before. He tosses down the cables that Yorke gave him earlier. They don't fit.

"I don't have any more cables," Yorke says.

Obviously, the intrinsic chaos of the universe is still monkeying with the work of the chaos team.

Roberts wanders back out the door, but not before he adds his own wisdom to the discussion of chaos.

"In my house, I've got a 10-month-old and a 2-year-old," he says. "Now, that's chaos."

"We look for problems that we think we can solve," Yorke says.

His chaos work isn't purely theoretical. It's not just butterfly wings and Martian pebbles. He is, as Gleick wrote, "the kind of mathematician who felt compelled to put his ideas of reality to some use."

So Yorke looks for practical projects, real-world applications for his mathematical theories. In 1984, he did an epidemiological study of gonorrhea that officials at the federal Centers for Disease Control called "extraordinarily useful for formulating approaches to gonorrhea control." In 1985, NASA scientists used an application of chaos theory math to steer a spacecraft around the moon so it could take a look at the Giacobini-Zinner comet.

Now, Yorke and his chaos team are working with the National Weather Service to devise an improved computer model for weather forecasting. It has nothing to do with butterflies flapping wings but it is very, very complicated.

"I need 3 million numbers to start my model up," he says.

Those numbers will be figures on temperature, wind speed and air pressure from all over the Earth and many levels of the atmosphere. And the numbers will be updated every 10 minutes. He hopes it will help meteorologists forecast more accurately.

"We seem to be doing pretty well," he says. "It'll be another six months before we can tell you how effective we will be."

That's not his only project. He's also working on an epidemiological study of AIDS. And of course there's that rat genome project, the one that is vexed by the vagaries of chaos and computer problems.

"We think we can do a better job of figuring out what the genome of a rat is," Yorke says. "But it's very hard for us to get money because -- well, who the hell are we? We don't have any history in genomics. So it's very hard to get money. If people don't have confidence in you, they won't give you money. And if you prove you can do it by working out all the details, they say, 'You worked out all the details, now you don't need the money.' "

He laughs. "That's why I hope the Japan Prize will give people more confidence in us."

The other team working on the rat genome -- the official rat genome team, based at Baylor University in Texas -- has plenty of money, Yorke says, and all the computers it needs.

"These people have huge arrays of computers -- 200 computers all linked together," he says. "But Mike" -- he gestures toward Roberts, who has returned to the office -- "he's trying to do a very tough part of the problem with two computers. Two computers that move from room to room because of the asbestos!"

"And my motherboard fried last night," Roberts says sadly.

"And he can't log in from home because his computer at home died," Yorke says.

It's that chaos problem again. No matter how much you study it, you still can't stop chaos from messing up your best-laid plans.

"You see? The world is not terribly predictable," Yorke says. "I give Mike a lecture every now and then about how you can't predict what's going to happen. I gave him this lecture three days ago. And two days ago, his motherboard fried. I told him, 'I don't know what's going to happen, but something will happen.' "

"You didn't predict that my motherboard would fry," Roberts says.

"Exactly!" Yorke says, smiling. "I said something would happen. That's what chaos is about -- very great complications."

"We all know that a small perturbation in our lives can produce big perturbations," says James A. Yorke, trying to put chaos theory in graspable terms.University of Maryland professor James A. Yorke's work in chaos theory has earned him the prestigious Japan Prize.