Five hundred years ago, philosophers thought the universe was a few hundred thousand kilometers across (with the Earth at the center). These days, scientists estimate the observable universe to be about 15 billion light-years across (with the Earth at the center of nothing because the universe has no center). That's a change of 14 billion trillion kilometers in 500 years. Do the math and you discover that our conception of the cosmos has expanded at a rate of about one light-year per second over the past half-millennium.

Science is fast.

It is also frighteningly accurate: Using equations provided by 16th century astronomer Johannes Kepler, we sent a tiny hunk of metal called Voyager on a billion-mile journey to the outer planets and beyond. Our aim in sending Voyager is as accurate as that of a sharpshooter firing a bullet from Earth and hitting a 1-foot target on the moon. It's not easy to get one's mind around science's achievements, and most of us -- who left science behind when we lost our high school textbooks -- regard science with a mixture of suspicion and the cold fear that it's generally over our heads.

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Timothy Ferris has written eight books on science, three of them enduring bestsellers: "Coming of Age in the Milky Way," "The Mind's Sky: Human Intelligence in a Cosmic Context" and, his most recent, "The Whole Shebang: A State-of-the-Universe(s) Report." Under Ferris' pen, science is never frigid or remote -- even for the science-wary reader. Packed with the colorful human beings that scientists actually are, his work gives us the real juice: Science is a process, a crazy, dynamic struggle of quirky turns, blind alleys, sleepless nights, absurdities and breakthroughs.

Here's how he introduces Tycho Brahe, a contemporary of Kepler's, in "Coming of Age in the Milky Way":

Tycho was an expansive giant of a man who sported a belly of Jovian proportions and a gleaming metal alloy nose -- the bridge of his original nose had been cut off in a youthful duel. Heroically passionate and wildly eccentric, he dressed like a prince and ruled his domain like a king, tossing scraps to a dwarf named Jep who huddled beneath the dinner table.

Ferris goes on to tell how Tycho died of a burst bladder at a formal dinner in his honor because it would have been impolite to excuse himself. Oh yes, and another distinction: Of the billions of human beings who had lived on Earth up until his time -- all of them looking up at the same night sky -- Tycho was the first to document the positions and motions of the stars and planets with scientific accuracy. Such precision allowed Kepler to write the equations that the National Aeronautics and Space Administration used to send Voyager to the outer planets and beyond.

Ferris' own nose sits on a handsome and rugged face beneath a wavy frame of brown hair. Sixteenth century lordly airs are hard to come by in these times, and it would be wrong to call the 56-year-old Ferris haughty. But the man has a solid and confident look to him -- the writer at the top of his game. He is given to tweed jackets and khakis that always smell of cigar smoke (he says he has never written a worthwhile sentence without a lighted cigar in hand), and he works from a grand, book-lined office on the bottom floor of his house in San Francisco. It's a remarkable setting: His house is the highest-set private property under Coit Tower, which crowns San Francisco's Telegraph Hill. His view of the Bay Bridge is stunning, and the four floors he shares with his wife, Carolyn Zecca, and son, Patrick, are tastefully rich -- with colors chosen by design guru Don Kaufmann and paintings by his talented wife. He is king of a castle in a sense, and his fellow royalty are such grand-vizier writers as Annie Dillard, Joyce Carol Oates, Hunter S. Thompson and Jim Harrison -- all of whom he considers friends.

Like each of them, Ferris has carved out his own literary niche. But while reading a Ferris book may be as easy and entertaining as reading a Dillard book, it's important to remember that the underlying subject matter is very different.

In some ways, science writing is tougher than science itself. At least, it is tougher to do well. A scientist must be rigorous and accurate. A science writer must be accurate, clear and also entertaining. Niels Bohr, a grandfather of nuclear physics who believed in communicating science to the masses, complained of what he called "complementarity," by which he meant the impossibility of being both accurate and clear at the same time -- let alone entertaining. As a scientist, Bohr could duck out of the clarity requirement by saying, as he did famously, "I try not to speak more clearly than I think." Science writers don't have the duck-out option, and Ferris' genius is his ability to meet all the criteria for good science writing. Critics acclaim him as "admirably lucid." He "sets the standard for clear-headed science writing today." He achieves "a heroic synthesis of cosmic knowledge" in "good, clean, poetic prose."

The very warp and weft of Ferris' texts are subtle storytelling threads that bring the reader to understand in words what scientists think of in math. Take supersymmetry. It's a centerpiece of modern big-bang cosmology. People win Nobel Prizes for achieving partial solutions to supersymmetry, but it is very hard to explain to the nonphysicist. Most physicists you ask get lost in jargon: gravitons, weak-gauge bosons and, uh, neutrinos -- yeah! Ferris just tells a story. Cosmologists believe, on the basis of some evidence, that once upon a time all the forces of the universe (gravity, electromagnetism and the strong and weak nuclear forces) were the same force -- in a state of supersymmetry. Something happened soon after the big bang to break supersymmetry and make these forces the radically different entities they are today (they pull on different things and at different strengths). If we can only figure out how they were once the same and discover what split them, we'll have come a long way toward understanding the origin of the universe.

Then comes a simple metaphor. In the beginning, the forces were a group of pencils, held together and standing on their points. Looking down on them from above, all you'd see was a neat group of identical erasers. But something happened. The hand that held them let go, and the pencils fell out in different directions. Now they look like separate items, like the separate forces in the broken symmetry of today's universe.

That Ferris can create simple metaphors and entertaining stories is probably not surprising. He was born to writing and fell in love with science early and actively.

Ferris' father had been a journalist and a public affairs officer, but hard times hit the family. The senior Ferris took his wife and two boys to the truck-farming community of Deerfield Beach, Fla., where, just after World War II, they rented a house for $45 a month. Though his father drove a truck for a living, young Timothy saw his father's passions emerge when he wrote fiction on the weekends. His mother had once been a literary critic. These parents encouraged their boys to enjoy literature, driving them once a month to a bookstore in a neighboring town where each was allowed to buy one hardcover book.

When he was 8, Ferris got a book called "The Child's History of the World," which was a tour of the Earth from astronomical and geological perspectives. He's pretty sure he didn't read it all the way through, but Ferris says the book hit him hard. "I just found it astonishing to realize that all of this stuff, the sort of loamy soils of the fields in which I was playing as a boy -- this is a small town in rural Florida -- that all this stuff hadn't always been here. That it had had a history. And that if you wanted to understand how it came to be part of the Earth, you had to understand astronomical processes. So I started to study astronomy."

But never to be an astronomer. The literary lineage was too strong for that and, says Ferris, the scientific ability too weak: Once in a college astronomy class, he tried to measure the width of Lake Michigan, using an astronomical technique called parallax. He came up with 800 miles wide, an answer that was 700 miles too large.

Instead, the young Ferris looked at Mars through a backyard telescope and then wrote about it. When he was 16 he acquired an agent for the science fiction novels and the astronomy textbook he was writing, none of which was ever published.

Working-world realities pressed him after college into writing jobs with steady incomes. Sitting on his top-of-the-world balcony overlooking San Francisco Bay, he tells the story of growing up dirt poor and pursuing writing because he loved it. He was warned, as writers still are, that there is no money in this craft and only a select few will make it. Why did Ferris become one of the select few? Like all greats, because he created something new. He crossed a '70s funky-cool style with a passion for hard science and came up with a product people loved.

After stints with UPI and the New York Post, Ferris took a job as the New York bureau chief for Rolling Stone in 1971, a heady time to be at that magazine, when rock's social revolution was in full force. Two years later, Ferris wrote an article about cosmology called "How Do We Know Where We Are If We've Never Been Anywhere Else?" It was an unusual piece for the magazine -- no musical figures, no social relevance -- but there's no doubt, the piece was Rolling Stone cool. "That humans know they live in a galaxy is astonishing," Ferris wrote. "It is as though a society of plankton confined to an inlet in the Philippines had managed to draw a rough but accurate chart of the entire Pacific Ocean." The article generated what Ferris calls surprising praise. People really liked it because it was simultaneously down to earth and very far out. It was easy to read and they'd never read anything like it before.

That was it. Time to write a book.

"The Red Limit: The Search for the Edge of the Universe" came out in 1977 and won the American Institute of Physics prize the next year, establishing Ferris as an exacting reporter who knew his science. In 1978, his popularity among scientists and his experience at Rolling Stone won him a unique opportunity. Along with scientists Frank Drake and Carl Sagan, Ferris curated the audio recording "Murmurs of Earth" that the Voyager spacecraft -- thanks to Kepler's equations -- is carrying out of our solar system as you read this.

After two more astronomy books and one on journalism, Ferris wrote the book that made him truly famous. "Coming of Age in the Milky Way" was nominated for a Pulitzer Prize in 1989, and it won a host of other honors. If you read one book on popular astronomy, this should be it. The science and storytelling are equally vigorous, and as a tale of human thought that includes difficult ideas of present astronomy, it is a comprehensive tome, albeit in simple language. What really sets it apart is its ingenious premise: We, as a species, are a child just reaching maturity. Millenniums ago, when we were young, we thought the sky was a canopy held up by the mountains -- the heavens were as close to us as a mother's face to a child. As we grew, we were able to focus farther. As we learned to count and write, as we learned to travel the Earth and as we pursued science, we grew up to understand how vast a cosmos it is -- 15 billion light-years across at least.

Which leaves us with a very itchy question: Are we the Milky Way's only children? This question underpins Ferris' second bestselling book, "The Mind's Sky." Here he rambles (his word) through what is known about the possibility of life on other worlds (billions of stars out there, probably billions of planets, ergo lots of intelligent life) and what is known about how the human mind thinks. Intelligence is a slippery concept, and, in us, it grew up in the specific evolutionary pressures of this little Earth, which orbits a cookie-cutter star in a suburb of the Milky Way. So what we know about our own selves says a lot about how we look at the cosmos -- and look for other intelligent beings. But it says nothing about the nature of other intelligences out there.

"The Whole Shebang" is a return to cosmology, but it's not a history. It's a landscape, and its subject, as the title says, is everything -- everything physicists and cosmologists and astronomers know and are trying to know about the universe, including whether this one is the only one out there.

Right now, Ferris is working on a book called "Seeing in the Dark," which promises to be, like "The Mind's Sky," a more philosophical journey through cognitive science and astronomy -- what happens as starlight comes into the human brain through the eye. Ferris recognizes these books as more interpretive and likes their sense of discovery and creativity. But he knows the power of his reportorial work. "Coming of Age in the Milky Way" and "The Whole Shebang" are both on the New York Times' list of the best books of the 20th century. This is pleasing to him in and of itself, but a wry smile comes over Ferris' handsome cigar-smoking face when he points out that Thompson -- his old friend from Rolling Stone -- has only one book on the list.

In all deference to the fear and loathing master, it's not hard to see why. Ferris is a polymath. His thinking is broad enough to strike us more than once, and probably more than twice. He uses Reni Magritte's "Ceci n'est pas une pipe" to explain a theory of human cognition put forward by physicist John Archibald Wheeler. Gertrude Stein and William Blake are heroes and he quotes them -- appropriately -- in his work. The music of Alban Berg serves as his metaphor for the complex subtleties of scientific thought. Perhaps his range of thinking explains why musicians, poets and even dance troupes have been inspired to create projects in their own genres based on "Coming of Age."

It's probably also why Ferris is so good at explaining science to the nonscientist. His range doesn't represent cultural sophistication for its own sake, though if you've never heard of Berg, you might think it does. To Ferris, music, philosophy, art and science are simply facets of the one human intelligence we all have (a physicist might call this intelligence supersymmetric). Pencil metaphors and stories about dwarfs help, no doubt, but it is more important that Ferris writes to the center of our brains and disregards the firewalls of thought we falsely assume are there.

Of course, science is Ferris' first among equals. With its restless skepticism and insistence on evidence, it is the fastest-moving mode of human thought (at one light-year per second!), and Ferris considers it the most interesting subject for books. He contends in "The Whole Shebang" that being a cosmologist is a smart, stable career these days because our knowledge of the universe is expanding so rapidly. The same should be said, for the same reasons, about being a cosmology writer -- especially if you're good.