October 2004
| R E V I E W |
It or Bit? |
|
|
THE COMPUTER SCREEN, like Alice’s mirror, is a window between two worlds. On our side is the world of atoms, of matter and energy, of everything palpable and ponderable. Looking through to the other side of the screen, we glimpse a world of “bits,” a place where intricate structures are built out of nothing more than information—abstract, insubstantial, mathematical. Ours is a world of randomness and evolution and accidents of history; here we have snowflakes, no two alike. Over there, everything happens according to algorithm; if you replay the movie, it comes out the same every time. Our world is all rough edges and never-to-be-repeated moments; the other is relentlessly deterministic.
Any mention of the looking glass, of course, raises a nagging doubt: Which side is reality, and which is reflection? Is it possible that our familiar universe of solid-seeming stuff—the whole hierarchy of atoms, molecules, planets, stars, and galaxies, not to mention ourselves—is at bottom just a pattern of bits manipulated according to some unfathomable algorithm? If we dig deep enough inside the elementary particles of matter, will we find there’s nothing there but the Cheshire-cat grin of information? These are the provocative questions that launch Hans Christian von Baeyer on a journey through the science of information, through the “immaterial parallel universe.”
The main issues can be framed in terms of two slogans. On one banner are the words of the late physicist Rolf Landauer of IBM: “Information is physical.” Although a message might take many different forms—it could be written on paper, encoded in the magnetic domains of a computer disk drive, spoken by the human voice—Landauer insisted that it must always have some physical representation. There are no disembodied bits. “Pure” information, divorced from the world of matter and energy, cannot exist, in Landauer’s view. It follows that when we want to manipulate information in some way, we are constrained by the laws of physics—including all those irksome thou-shalt-nots about the speed of light and time travel and perpetual motion.
The other slogan comes from John Archibald Wheeler, an eminent, nonagenarian Princeton physicist: “It from bit.” What could this pithy koan signify? Wheeler himself (as quoted by von Baeyer) has expanded on his words, though perhaps not quite explained them:
Every it—every particle, every field of force, even the space-time continuum itself—derives its function, its meaning, its very existence entirely—even if in some contexts indirectly—from the apparatus-elicited answers to yes-or-no questions, binary choices, bits.
Whereas Landauer wanted to set bits on a firm foundation of atoms, Wheeler replies that underneath the atoms are just more bits. You begin to feel a little like Wile E. Coyote when he runs off the edge of the cliff: It’s only when you look down and realize there’s no ground beneath your feet that you begin to fall.
Von Baeyer introduces the disconcerting “It from bit” trope quite early in his story, which may make some readers nervous. If we are already deep in such murky metaphysics on page xii, what kind of spookiness might be waiting in the chapters ahead? But in fact what follows is a sensible and sober-minded tour of the science of information, emphasizing its connections with a surprising variety of other fields, from the engineering of steam engines to the fate of black holes and the understanding of the human genome. At the end of the journey you may not be ready to trade in all your its for bits, but the notion will seem a little less preposterous.
The key ideas in the theory of information—including the all-important idea that it needs a theory—were first stated clearly in a 1948 article by Claude Elwood Shannon, a legendary gadgeteer, juggler, and unicyclist as well as a deep thinker. Shannon suggested measuring information in terms of those yes-or-no questions alluded to by Wheeler. If I flip a coin, you can learn the outcome by asking me a single yes-or-no question: “Did it land heads up?” If I roll a six-sided die, you might need three such questions to pin down the result. For example, when you ask “Is it greater than 3?” I answer “Yes.” Then you ask “Is it 4?” and I respond “No.” After your third question you will surely know whether the number is 5 or 6. Sometimes you might get lucky and guess the outcome sooner, but three is the smallest number of questions guaranteed always to yield the right answer.
Shannon defined the information content of a message as the number of yes-or-no questions needed to distinguish the actual message from the set of all possible messages, assuming they are all equally likely. The fundamental unit of measure in this scheme is the bit, which is the amount of information contained in a message that answers a single yes-or-no question. Thus when I tell you how the coin landed, I am conveying one bit of information. When I report on the roll of the die, I am passing along about three bits. If I spin a roulette wheel with thirty-eight slots and tell you which lucky number comes up, I am transmitting about six bits.
The term bit began as a contraction of binary digit, because a digit in the binary counting system has just two possible values, 0 or 1, which can be made to stand for yes or no. The information content of a message is the number of binary digits it would take to transmit it. In the case of the die, the six possible messages are the numbers from 1 through 6, which in binary notation are written 001, 010, 011, 100, 101, and 110. These are three-digit binary numbers, and so three bits is their approximate information content. Roughly speaking, counting binary digits is all there is to measuring information. (Speaking less roughly and more mathematically, the measure of information is the base-2 logarithm of the number of possible messages, but counting digits is usually close enough.)
A connection between the world of bits and the world of atoms was already apparent in Shannon’s 1948 article. His measure of information is closely related—by a sort of mirror reflection—to the concept known elsewhere in the sciences as entropy, the measure of disorder. If you take a hunk of matter—say a billion atoms—the entropy of the substance depends on the number of ways the atoms can arrange themselves. The arrangements are more varied for a gas than for a crystalline solid, because the crystal constrains the atoms to occupy only certain positions, whereas gas atoms can wander willy-nilly. In other words, the gas has the greater entropy. If you write down the number of possible atomic arrangements, the entropy is the number of digits in this number (or, if you want to be a stickler, the logarithm of the number of arrangements). Evidently, the mathematical formulas for information and for entropy are almost identical. Whether that coincidence is trivial or deeply mysterious seems to be a matter of intellectual taste, but it does appear that atoms and bits obey the same laws of nature.
For another look at the tangled relations of atoms and bits, von Baeyer takes us to one of the strangest shores in the universe, the “event horizon” of a black hole. Suppose you throw something into a black hole—say, a book about baseball. As the book disappears across the horizon, its matter becomes inaccessible, but it doesn’t really cease to exist. We know that because the mass of the black hole (which you can measure from outside) increases by an amount equal to the mass of the book. But what about the information in the book—all those tables of runs, hits and errors? Where does it go? If the bits are just crushed out of existence, then the total quantity of information in our universe must be steadily declining. Every day, there’s less to know.
That was the position taken by Stephen Hawking, the Cambridge cosmologist, some thirty years ago—and he backed up his convictions in a wager with another cosmologist, John Preskill of Caltech. This past July, however, Hawking announced that he had changed his mind: he had discovered a way for information to leak out of a black hole, thereby keeping the number of bits in the universe constant. So Hawking paid off the bet, presenting Preskill with a baseball encyclopedia. (The wager was settled too late for von Baeyer’s book, but he gives a lucid account of the underlying issues.)
In the life sciences, too, the role of information has its puzzlements. The genetic code, with its alphabet of four letters grouped into words of three letters each, looks uncannily like some kind of computer file format. In recent years this approach to understanding genetic information has burgeoned into an entire academic discipline, and indeed an industry: bioinformatics. Yet there’s more to genetic information than just DNA sequences that encode the structure of protein molecules. For one thing, organisms seem to differ more than their genomes do. The question “Are you a man or a mouse?” is not easy to answer from a glance at the DNA; people and mice have 90 percent of their genes in common. Furthermore, most of the DNA in both species has no readily apparent function; life’s file format, whatever it is, seems even more grotesquely wasteful of megabytes than the most bloated computer software.
The final informational mystery, and the one that seems most to intrigue von Baeyer, is the elusive seat of meaning. He writes:
Information . . . resides partly in the mind. A coded message, for example, might represent gibberish to one person, and valuable information to another. Consider the number 14159265. . . . Depending on your prior knowledge, or lack thereof, it is either a meaningless, random sequence of digits, or else the fractional part of pi, an important piece of scientific information. The smell of subjectivity, of dependence on a state of mind, is the source of both the elusiveness and the power of the concept of information.
Once again the comparison of bits and atoms is illuminating. In the case of information, it’s no great surprise that meaning is imposed on a message by the sender and receiver. We are all accustomed to thinking of communication as something that happens between people, and so minds are naturally a part of the process. But it’s unsettling when a similar kind of subjectivity is invoked to explain the behavior of atoms or electrons. As von Baeyer says, “At the mention of the word subjectivity, physicists cringe”—even though it was physicists who got us into this pickle in the first place, who introduced “the observer” as an essential element of every experiment.
We may prefer to think that atoms go their merry way whether we’re looking or not, that the material universe maintains a dignified indifference to human whims—but the modern quantum theory won’t allow such aloofness. There are experiments on simple, inanimate particles, done with simple instruments, in which the outcome depends on which yes-or-no questions the experimenter chooses to ask. When you decide to peek inside one box rather than another, your action has the power to change what’s in both boxes. Presumably that is what Wheeler has in mind when he argues that the real ground truth of the universe comes from “the apparatus-elicited answers to yes-or-no questions, binary choices, bits.” What is still missing is an explicit account of how the bits are to be assembled into atoms and all the other its. Von Baeyer makes a valiant effort to fill in those blanks, focusing in his final chapter on the interesting ideas and experiments of Anton Zeilinger at the University of Vienna. But the vagueness persists. The fault is not von Baeyer’s; Wheeler has not clarified the process either, nor has anyone else.
Von Baeyer is a physicist, but he is also an able and accomplished expositor, author of four earlier books and many magazine essays. As one might expect, he is more sure-footed in his own field than in others; his worst stumbles are in the life sciences, as when he describes gene expression as the synthesis of amino acids rather than the assembly of amino acids into proteins. Another minor annoyance: Information was published first in Britain, and no one has bothered to convert spellings and currencies and such for American readers.
And I can’t resist mentioning a subtle mathematical error. Von Baeyer sets out to show that binary notation is “the least expensive way to handle information,” where the “expense” he wants to minimize is defined as the number of digits in the numerical representation of a message multiplied by the number of symbols possible for each digit. In his example, any number from 0 to 127 can be represented by seven binary digits, each of which has two possible values. The expense, therefore, is 14. The trouble is, this supposed optimum isn’t. In almost all cases, binary numerals are less efficient than a ternary (base 3) representation, in which each digit can have a value of 0, 1, or 2. In von Baeyer’s example, ternary notation would reduce the cost from 14 to 13. So perhaps information theory ought to be reformulated in terms of yes-no-or-maybe questions.
Setting aside these quibbles, von Baeyer’s book brings us the straight dope and the inside info. The presentation is smooth but never slick. History and biography are given due attention but don’t overshadow the science. There’s some hero worship, but the heroes are mostly deserving of worship. Math-shy readers will not be left behind (von Baeyer devotes an entire chapter to explaining logarithms).
The science of information is hardly an obscure or neglected subject; on the contrary, it’s a little too trendy for its own good. Part of von Baeyer’s aim is to find out if it merits so much attention. He draws a parallel between the current infatuation with information and the popularity of another big idea, energy, starting early in the nineteenth century. In both cases, the initial impetus was a technological development—the steam engine for energy, the computer for information. But the concept of energy soon spread far beyond the engineering of more efficient power plants. It became a central and irreplaceable part of all the sciences. How could we possibly understand anything about the natural world without the notion of energy?
So far, though, the concept of information has proved itself similarly essential only in the world on the far side of the computer screen. We may have to wait a while to find out exactly what role bits play on our side of the looking glass.
Brian Hayes is a Senior Writer for American Scientist. His book Infrastructure: A Field Guide to the Industrial Landscape will be published next year.
| B O O K S H E L F |
|
By Laurence A. Marschall |
back to top |
|
|
S O HERE’S THE STORY: One early spring day, in the free-flying era long before 9/11, a young bird enthusiast and nature writer has signed on as a falcon trapper’s helper with a crew of U.S. Army scientists on Padre Island, off the western Gulf Coast of Texas. Out of the blue, the writer gets the idea that a peregrine, tagged and loaded down with telemetry, could be followed in an airplane as it migrates to its home above the Arctic Circle. No one, to his knowledge, has ever accomplished such a feat.
He enlists the army project’s pilot in his plan: a sixty-seven-year-old veteran light-aircraft aviator, former World War II combat flight instructor, and the proud owner of a battered, hailstone-pocked Cessna. After a little planning, and with a good dollop of crazy luck, the two lock on to a falcon fitted with a miniature radio transmitter filched from the army. With scanner-receiver equipment also “borrowed” from the army, they take to the air in pursuit of the errant bird, going wherever it happens to go.
Believe it or not, bird, writer, and barnstormer travel together almost all the way to Alaska, a summer breeding home for the tundra peregrine falcon. Three months later, the gonzo team repeats its performance, latching on to several falcons mid-migration in Texas and tracking them down to their winter homes in Central America. Mostly the two men fly around listening for beeps on their receiver, never catching sight of the birds they’re chasing.
Sound like a snooze? Well, having just finished On the Wing in one breathless sitting, let me assure you that this book moves with the energy of a four-star action movie. Avian instinct, not wise aviation practice, is what sets the course for the flights, forcing the writer, Alan Tennant, and the pilot, George Vose, to take to the air whatever the weather, terrain, or time of day. Aloft, they often find themselves in the thick of adventure—threading their way in dense fog through a forest of giant oil-refinery towers; catching updrafts that toss them around like feathers; flying dangerously low on fuel while venturing miles from any airstrip.
Down on the ground, it doesn’t get much easier. Chasing their falcon across the Canadian border, they enter foreign airspace illegally, and eventually the Mounties bring them in for questioning. Every evening, when the falcons themselves have to stop for food and rest, the two aviators come in to land and fill their tank wherever there’s a convenient spot of flat ground.
Once in a while, their impromptu refuelings even require a stop at a rutted dirt strip where drug smugglers, or armed militiamen, hang out. Coming into an urban airport in Belize, they barely escape rear-end collisions with incoming commercial jetliners. Fearless and imperturbable, Vose pilots them out of one near-death experience after another, only to have Tennant urge them back into the air.
To Tennant, who has loved raptors since he was a boy, the lure of the migratory bird is too strong to resist. He wants to learn how the peregrine does it, how a bird can fly hundreds of miles a day, feeding sporadically and buffeted by uncooperative winds. Luckily, though, the story also has a human love interest—Tennant’s girlfriend Jennifer. Only she has enough sense to know that you can’t go on chasing magic forever. And Tennant balances his own passions with plenty of fine nature writing: keen descriptions of bird behavior, well-drawn landscapes, and thoughtful discourses on what it means to be wild. Still, the human action, in the end, is what draws the reader onward.
Tennant and Vose’s journey, made in 1985, probably could not be replicated today. GPS radio locators and Internet software have done away with any need to fly around wearing headphones. Nowadays, migrating wildlife can usually be tracked much more easily, and more safely, from the comfort of a university office [but see “Wherever the Wind May Blow,” by Henri Weimerskirch]. It’s a safe bet, too, that anyone buzzing around in the twenty-first century, violating military airspace and cruising without a flight plan—not to mention crossing international boundaries without the proper paperwork—would probably not live long enough to write about it. The reader is thankful that Tennant did, and the book (rumored soon to be a movie, with Robert Redford as Vose) will keep you rapt to the very end.
|
|
THE IDEA that a landmass once joined America and Asia arose not long after the explorer Vasco Núñez de Balboa, in 1513, first waded into the ocean that separates the two continents. In 1590 José de Acosta, a member of the Jesuit brotherhood, published a natural history of the New World that drew on biblical “facts” to prove the existence of such a bridge. Native Americans, he wrote, being descendants of Adam and Eve, must have migrated on foot from the environs of the Garden of Eden eastward to the mountains of Mexico and Peru. Fray de Acosta reasoned that they must have come across a land connection somewhere in northwestern North America. That coastline, however, would remain uncharted for more than a century, until its exploration by the Scandinavian navigator Vitus Bering.
By the middle of the twentieth century, the conjectured existence of a Bering land bridge had been bolstered by a wide range of circumstantial evidence. New World animal species that live along the shores of the Arctic Ocean appeared to be similar to the Old World species that inhabit Siberia. And the farther south you went, the greater were the differences between the species on the opposite shores. The evidence suggested that a wave of animal migrations radiated southward from the Arctic long ago; as time passed and the distance from their common origin increased, the Asian species diverged from their North American counterparts.
Oceanographic data provided another line of evidence. A continuous continental shelf fringing Asia and North America was discovered offshore. Geologic records suggested that sea levels during the last ice age were low enough to expose the shelf beneath what is now the Bering Strait, between Alaska and Siberia. But “land bridge” seems an inexact term for a connection that, unlike the narrow isthmus that joins North and South America, was probably, at its widest, as broad as the north-south distance across present-day Alaska. For that reason, specialists prefer to call the connection Beringia, reflecting its former character as a shared territory, a cosmopolitan province where the mammoths and steppe grasses of the Old World mingled with those of the New.
In the past fifty years, investigators have managed to reconstruct the vanished landscape of Beringia—from its varying size and coastline as the eons passed, to the natural history of its plant, animal, and human populations. A central figure of that research, until his death in 2001, was David M. Hopkins, a geologist with the U.S. Geological Survey, and the “Beringian giant” of historian Dan O’Neill’s book.
Hopkins pioneered a multidisciplinary approach to paleogeography, but he also inspired several generations of Arctic scientists with his love for the Alaskan wilderness. As a government employee during the cold war years, his official task, at least early on, was to find suitable sites for air bases and related facilities, and to assess what natural resources might be exploited in the barren sub-Arctic outback. But his superiors, recognizing his genius for seeing the big picture, apparently had enough sense to give him lots of slack.
Hopkins’s research was liable to take an unplanned turn at any time. As O’Neill tells it, the man had uncanny luck, augmented by a knack for quickly distinguishing what was important from what was not. A chance remark by a bush pilot who had seen some arrowheads led Hopkins to Trail Creek, in the remote Seward Peninsula. Cave excavations there subsequently unearthed artifacts of some of the earliest people on the continent. A conversation about shells with an Inupiat native from Nome named William Oquilluk led Hopkins to rich deposits of fossil shells, which proved key to tracing the changing shape of the Beringian coastline over the past 60 million years.
Hopkins was also energetic about recruiting pioneers in other disciplines for his field trips, and enlisting their expertise in such disciplines as dendrochronology (tree-ring dating), palynology (the study of fossil pollen), and radiocarbon dating. In his later years Hopkins was influential in establishing the Bering Land Bridge National Preserve in Alaska, a part of the U.S. National Park Service. Like many modern scientists whose work involves close collaboration, he was never a celebrity outside his field. O’Neill’s Giant of Beringia, appropriately, is a modest tale, but a satisfying one, an instructive record of an inquiring mind and a life well lived.
|
|
ON TOPOGRAPHIC MAPS of Minnesota’s Arrowhead region—a long, flat triangle sandwiched between the northwestern shore of Lake Superior and the Canadian border—the Boundary Waters Canoe Area Wilderness looks like a tattered pennant fluttering against a clear blue sky. Its million-plus acres of forestland are so thoroughly perforated with lakes, creeks, and rivers that it’s hard to tell whether it is a land sprinkled with lakes or a sea dotted with islands. After Congress passed the Wilderness Act of 1964, Boundary Waters became one of the most popular and treasured backcountry preserves in the lower forty-eight states. On many of its waterways a visitor can paddle a canoe for days without hearing the din of an outboard engine, or even the whisper of another human voice.
Yet Boundary Waters is no virgin territory. After the vast forests of New England, Pennsylvania, and Ohio had been logged, lumbermen set their sights on Minnesota, home of some of the last large stands of unexploited forest east of the Rockies. A century ago, the rhythmic chunking of loggers’ axes and the scream of sawmills were as common among the trees and lakes of Minnesota as the call of the loon. On large lakes near major access roads and rail lines, rafts of floating logs often made canoe travel impossible. In summer, logging roads were bulldozed over the rocky terrain, and steamships carried men and supplies to remote forest camps. In winter, teams of horses dragged sledges loaded with cut logs across frozen lakes.
The mill yard of the Knox Lumber Company, in Winton, stretched for nearly a mile along the shores of Fall Lake. In Ely, now the canoeing capital of the world and a mecca for outdoor adventurers, the steam whistles of lumber mills regulated the daily routine of townspeople well into the twentieth century. Between 1880 and 1920 alone, more than 2 billion board feet of white pine were shipped out of northern Minnesota to build the towns and cities of the growing nation.
Jeff Forester, a freelance writer and frequent visitor to Boundary Waters, has written a thoughtful history of how the Minnesota backwoods became, for a time, an industrial hub, and was then returned to wilderness. The Forest for the Trees is enriched with the lore of the enterprising woodsmen and lumber barons who developed the rugged area, bringing in roads, rails, and electricity. And its author tells some good yarns about working the timber mills and living in the timber camps, about the rough-and-tumble life of the mill towns, where dozens of whorehouses and saloons offered the main entertainment after hours.
But Forester also outlines the history of social and economic development in this resource-rich region. The pioneering lumbermen, he notes, were independent operators, family men who just wanted to make a comfortable life for themselves and their neighbors. As the pace of cutting increased, however, the northern forest came under the control of such commanding industrialists as Frederick E. Weyerhaeuser, who thought big and who hauled great stands of trees to the lumber yards with giant steam-driven tractors and mile-long trains of flatbed railcars.
By the time of Teddy Roosevelt, industrial laissez-faire policies were being challenged by a growing conservation movement. Properly managed forests, the movement taught, could provide both exploitable harvests and recreational getaways. Yet it was only in the 1960s that wilderness advocates began to widely promote the idea that some land should remain “forever wild,” leading to the creation of the Boundary Waters reserve. The concept of untouched wilderness there, however, is being reevaluated. A freak straight-line windstorm caused a massive blowdown of trees in the area in 1999, and the profusion of fallen timber raised fears of a catastrophic firestorm. Eventually the U.S. Forest Service was forced to schedule controlled burns.
Whatever the forest policy these days at Boundary Waters, Forester’s book should be required reading for anyone planning an adventure in the Minnesota north woods—or, for that matter, for anyone who wants a better appreciation for the past, present, and future of America’s forests.
Laurence A. Marschall, author of The Supernova Story, is the W.K.T. Sahm professor of physics at Gettysburg College in Pennsylvania, and director of Project CLEA, which produces widely used simulation software for education in astronomy.
| N A T U R E . N E T |
| Mother Tongue By Robert Anderson |
back to top |
My curiosity piqued, I poked around for other language-specific sites and found an instructive Web page created by C. George Boeree, a professor of psychology at Shippensburg University in Pennsylvania (www.ship.edu/~cgboeree/languages.html). I began by clicking on “Language Families of the World (maps),” and discovered a series of informative geographic charts, each one accompanied by brief but illuminating comments and statistics.
The “Archaeolink” Web site provides a page with numerous links to sites that specialize in linguistic anthropology (www.archaeolink.com/linguistic_anthropology_index.htm). Click on the very first link to find a transcript of the PBS NOVA television program “In Search of the First Language.” The material focuses on the quest for the linguists’ holy grail—Nostratic—a hypothetical tongue that some maintain was once the universal spoken language.
To show how parts of our modern alphabets evolved from pictographs and symbols, Robert Fradkin, a classicist at the University of Maryland in College Park, has developed a Web page of animated course material (www.wam.umd.edu/~rfradkin/alphapage.html). Click on the last item in his list, “The evolution of the Latin character set,” and watch as Phoenician symbols from the tenth century b.c. slowly morph into our own ABCs.
For the latest on living languages, go to the Web version of Ethnologue: Languages of the World (www.ethnologue.com/web.asp), a compendium of information about the world’s spoken languages, now in its fourteenth edition. Published by SIL International (an organization best known for Bible translating), the “Ethnologue” site is on a language-preservation mission; it lists, for the year 2000, a total of 6,809 languages spoken (but not necessarily written) worldwide.
A cogent introduction to the major language families of the world can be found at one section of a site operated by Kryss Katsiavriades and Talaat Qureshi, a well-traveled couple who work as computer-science professionals in London (go to www.krysstal.com/language.html#langfams and click on “Language Families”).
Although it isn’t as easy to listen to languages on the Web as it is to read about them, you can still find an eclectic range of audio experiences. An issue of the online magazine Exploratorium (www.exploratorium.edu/exploring/language/index.html) has five pages on the evolution of language that include several links to audio files. Listeners who go to Haukur Thorgeirsson’s on-line course in “Old Norse for Beginners” (www.hi.is/~haukurth/norse/) can hear epic poetry recorded in Old Norse, as well as in Icelandic and in English (click on “Recordings” on the main page, and then on “Vellekla”).
For something more contemporary, Transparent Language, Inc., which sells learning software, offers some language and culture pages at its online site (www.transparent.com/languagepages/languages.htm). You can listen to the pronunciation of useful, common words and phrases in thirty different tongues. And www.everytongue.com, which is affiliated with SIL, offers a relatively long audio sample of nearly a hundred different spoken languages, from Armenian to Zulu. Not surprisingly, most of the passages are readings from the Bible.
Robert Anderson is a freelance science writer living in Los Angeles.
Copyright © Natural History Magazine, Inc., 2004