Читать книгу Lens to the Natural World - Kenneth H. Olson - Страница 11

3 / Deep Time

“Time is to Nature endless and as nothing.”

James Hutton (1775)

Agatha Christie, of mystery novel fame, was married to an archaeologist. She liked to say that was a very good deal, because the older she got, the more interest her husband showed in her.

Time is one of the basic constituents of the universe; any and every experience has this elusive dimension. Within our brains are complex biologic clocks that react to light and dark and time our sleeping and waking. The world over, there are intervals of growth and dormancy that occur time and time again. The garden flower regularly opens with the dawn, and the calendar can be counted on to transform the aspen leaves to golden hues. Immense flocks of birds migrate over the earth, taking instinctive cue from the sun, seasons, and time.

How difficult it is to express the nature of time. We are immersed in it, caught in its flow, yet we really have no definition of it that does anything more than scratch the surface. “What, then, is time?” Augustine wrote at the close of the fourth century. “If no one ask of me, I know; if I wish to explain to him who asks, I know not.”

As time passes, the world around us changes, and so do we. Our memories take us back to an event that happened ten or twenty years ago, and it seems but an instant since then. Yet we look in the mirror and know, without doubt, that something has happened, that there has been a meantime between then and now. Events replace one another in swift succession, and the process goes on without pause. We look at an old picture, brown, faded, and cracked. The image is of people who appear much like our own selves; they are at a reunion or celebration . . . and they are no longer part of our world. Time has passed.

No other instrument or machine is so everywhere-present as the ones that mark its passage; a watch is on nearly every wrist. We measure days by the rotation of the earth. We mark longer periods with the year, the time it takes the earth to make one orbit in its revolution around the sun. (I recall one person who expressed some surprise upon learning that the earth went around the sun in 365¼ days, who said, “Isn’t that a coincidence! It takes exactly one year!”) The other planets, of course, have different “years.” It takes Neptune 164 of our earth’s years to make a single one of its own.

Accurate measurements of time were a long time in coming. Inscribed on many sundials are the words, “I count only the sunny hours,” a saying meant to accent optimism but also indicating the sundial’s limitations. The Romans made timepieces from candles and from vessels that dripped a certain quantity of water. Hourglasses gave us the metaphor “the sands of time” as well as the phrase, “time is running out.” There is something pensive and thought provoking about grains of sand trickling down in an hourglass. While time itself is invisible and ineffable, it helps to get a feel for it, to think that time is something like that. More recently, many grandfather clocks carried the Latin phrase tempus fugit inscribed on the dial: “time flies.”

Clocks, as we know them, were developed during the Middle Ages in the monasteries of Europe to call the monks to prayer. The very word “clock” is from a Dutch word for bell, and, until the fifteenth century, most clocks had no face or dial because the function was to “sound” the hours.

A seventeenth-century Frenchman contrived an ingenious one using another sense altogether. He designed a clock face so that in pitch darkness he could reach for the hour hand, which then guided him to a hole in which a particular spice had been placed; there was a different spice for every hour-position on the clock. Having memorized which was which, he could say, “Let’s see: cinnamon—it must be 2 a.m.” Thus, in spite of not being able to see the clock, he could taste the time.

Recently, humanity has become increasingly expert at dividing time into smaller and smaller segments. There are now clocks that use vibrating cesium atoms to measure time to an accuracy of one part in a million million. Such an instrument would lose only one second in thirty thousand years—a single tick between the last Neanderthals of Europe and what will likely be the first colonists on Mars.

The Greek language has two words for time. The first is chronos, i.e., chronological time. It is time marked on our clocks and calendars in terms of seconds and minutes, hours, months, years. It is time that flows evenly along and it can be divided into segments, each of which is the same duration and all alike: it is quantitative time.

However, time, as we experience it, is also qualitative, indicating that not all time is of equal import or significance. The day you spent working on your tax report and the day you had “the time of your life” were likely not one and the same. To indicate time charged with significance, the word employed is kairos. There is no one English word for it, but it might be translated as “the time of opportunity” or “the right time.” It is the time, which, for good or ill, is either seized or lost; in either case, it will never come again.

Suppose two people work high above on a flying trapeze without a net below. The one person swings, then lets go of the bar and flies through the air, meeting the other in perfect timing and, in a split second, is caught and is safe. There are no second chances for that connection. Or recall when the first astronauts would ride the huge Saturn V booster rockets that would put their capsules in orbit around the earth, enabling them to go on to the moon. At the moment of blast-off, if something went wrong and the alarm sounded, they had three and one-half seconds to push the button that would eject them clear of the impending explosion—that and no more. There would still be plenty of time, in the sense of chronos, but not for that “life or death” decision; that little slice of time would be crucial time: kairos.

It is indeed true that not all time is weighted the same. In the Old Testament book of Ecclesiastes, chapter 3 is a section that is often read at funerals, weddings, and many other occasions, because it speaks of the right time for various events and emotions. “For everything there is a season, and a time for every matter under heaven: a time to be born, and a time to die; a time to plant, and a time to pluck up what is planted; a time to kill, and a time to heal; a time to break down, and a time to build up; a time to weep, and a time to laugh; a time to mourn and a time to dance . . . a time to seek, and a time to lose; a time to keep and a time to cast away; a time to rend, and a time to sew; a time to keep silence, and a time to speak; a time to love, and a time to hate; a time for war, and a time for peace.” (Eccl 3:1–4, 6–8. Revised Standard Version)

There have been at least three quite different perspectives by human beings toward the passage of time, three different ways of orienting oneself in relationship to it.

In the first place, it may be that truly ancient peoples lived in a kind of timeless realm. As the snows came and went, wandering peoples drifted with the seasons. There was no calendar and the only record left behind may have been flint tools from a campsite. Perhaps myths developed about the “the old ones” or “the dream time,” but almost everything was lost in the course of passing millennia. People lived largely in the present. Only in a few places can one find anything resembling that today. Peter Mathiessen stayed with many of the tribal peoples of East Africa prior to recounting his travels in his book, The Tree Where Man Was Born. He described the Hadza hunter-gatherers, thus: “For people who must live from day to day, past and future have small relevance, and their grasp of it is fleeting; they live in the moment, a precious gift that we have lost.”

Secondly, there is the cyclical conception of time, the idea that it is moving in vast circles. The ancient Maya had an accurate calendar some 1400 years ago, with much of their ceremonial and social life revolving around the mystery of time’s passage and their attempt to predict the huge cycles of their imagination. The Hindus, still today, see the universe as moving in vast arcs of hundreds of millions of years. In that system of belief, an individual goes through one incarnation after another, so time is likened to a wheel. The ancient Greeks and Romans believed the universe itself was eternal; they had a circular or, at least, a “spiral” conception of time. Their saying, “History repeats itself,” is old, indeed, and expresses the idea that there were whirlpools in the stream, where things came to be, then passed on, perhaps only to come again.

Such a concept of time, while it may seem remote and abstract, might have great practical significance in one’s daily life, should one adopt it, for it is, ultimately, a pessimistic view: history is going nowhere and humanity is tramping about on a kind of eternal treadmill. Historian Will Durant has written of what he calls the “indispersible gloom which broods over so much of Greek literature.”

Ecclesiastes is one of the most heavily Greek-influenced books of the Bible, and it has this tone. The book is included in Scripture, some say, to illustrate the consequences of such a point a view. Thus, in addition to those beautiful verses about there being “a time for every matter under heaven,” there are passages like these: “What does man gain by all the toil at which he toils under the sun? A generation goes and a generation comes, but the earth remains forever . . . What has been is what will be, and what has been done is what will be done; and there is nothing new under the sun . . . all is vanity.” (Eccl 1:4, 9, 12:8b)

The third conception of time is linear, i.e., there is an arrow, a direction to time’s passage: time is going somewhere. In this perspective, the universe, everything we know, has not always been. It had a beginning. Time moves “forward” and each moment in the present and the future is different from the past, unique. The universe, thus, is evolving.

This is the dominant time frame found in the Bible. There, time is the medium of the divine drama, wherein God is moving creation from a beginning toward the goal of fulfillment or consummation. Many have noticed that such a view is compatible with that of modern physics and astronomy, which speak of the universe beginning in a single instant: the primordial explosion that has come to be known by the trivial name of the Big Bang, then developing onward and outward from there over the course of nearly 14 billion years. Robert Jastrow, the founder and past director of NASA’s Goddard Institute for Space Studies, wrote of the scientist searching for answers who follows his data back to that initial event, but who is stymied by the fact that every bit of the evidence needed for studying the cause of it has been obliterated in the explosion. All the fingerprints have been erased, and the first cause is forever beyond reach: “The scientist’s pursuit of the past ends in the moment of creation . . . He has scaled the mountains of ignorance; he is about to conquer the highest peak; as he pulls himself over the final rock, he is greeted by a band of theologians who have been sitting there for centuries.”

An old saying is to the effect that if one marries the science of the time, one will soon be a widow/widower, a caution that must be kept in mind. However, there are more than a few who maintain that science itself owes a huge debt to this fundamental Christian perspective that time is linear. The idea is that science, which traces causes and effects and evolutionary sequence, could only develop if you had, as you did in Western Europe, some such idea of the linear, progressive, or developmental character of time that infused the entire culture.

One aspect of time is that which is past. In a sense, we never experience anything but the past. The sounds you are now hearing come from a thousandth of a second back in time for every foot traveled to reach you. And what is true of sound is true of light, but on a “faster” scale. When we look up toward the sun, we see it as it existed eight minutes ago, for it takes that long for light, traveling at 186,000 miles per second, to traverse the 93 million miles of space to earth.

All winter long the great galaxy M31 in Andromeda hangs in the night sky. This near twin of the Milky Way is the farthest thing that any human being has ever seen with the naked eye. If you know right where to look, you can see the hazy, glowing patch of light that our large telescopes reveal to be a spiral of perhaps 200 billion stars. It is 2.3 million light years away! That is to say, its light that reaches us tonight began its journey to us that far back in time, and what we see is a ghostly image formed that far in the distant past. Thus, deep space takes us into deep time, as well.

The attempt to transcend our limitations in time is a persistent theme in literature. H. G. Wells wrote a short story in which he imagines the possibility of science tapping into the “memory” of the human race itself: “A day may come when these recovered memories may grow as vivid as if we in our own persons had been there and shared the thrill and fear of those primordial days; a day may come when the great beasts of the past will leap to life again in our imaginations, when we shall walk again in vanished scenes, stretch painted limbs we thought were dust, and feel again the sunshine of a million years ago.”

In 1955, Albert Einstein learned of the death of his best friend, Michele Besso and wrote a brief letter to the family (as it turned out, just a few months before his own death): “He has departed from this strange world a little ahead of me. That means nothing. For us believing physicists, the distinction between past, present and future is only a stubborn illusion.”

Virtually everyone knows of one of Einstein’s ideas, that time may pass differently, depending upon the speed at which an object is moving, i.e., that time is relative to motion. At 99 percent of the speed of light, a month in a spaceship might be a year on earth. An imaginary space traveler might return to earth in what she thought was five years, only to find her friends and family had aged fifty or be all dead and gone. A movie that captured the public imagination decades ago, 2001: A Space Odyssey, had such a theme, and there have been numerous others since. There has been much silly stuff written about time travel; however, the universe may be strange beyond our imaginings.

There are additional ideas concerning the unevenness of time’s passage. In England’s Chester Cathedral is an inscription on the face of a clock, part of which reads: “When, as a child, I laughed and wept, time crept. When, as a youth, I dreamed and talked, time walked. When I became a full-grown man, time ran. And later, as I older grew, time flew.” All of us have known something of that. As kids, we waited for our parents to finish shopping and it “seemed like an eternity.” We have heard the elderly talk about how, for them, “time has flown.”

The Swedish paleontologist Björn Kurtén suggests that whether time seems to pass slowly or quickly is not, in fact, just seeming; rather, it depends upon our pace of living. Thus, he says, a child’s wound heals more rapidly, tied to bodily processes. He points out that a child makes decisions quickly, while the old take their time thinking it over; we may say this is due to experience and the wisdom of age, but it might reflect a different tempo of life, so that both are ruminating on the subject to about the same degree.

Kurtén suggests that time, for human beings, has something of a “logarithmic” character, the distance from year one to ten being as long as the distance from ten to one hundred. Thus, during one-half of our subjective lifetimes, we are children, illustrating why these are the teachable years.

Perhaps, says Kurtén, how time is experienced is relative to size, as well. Smaller animals live at a frantic pace. Although a generation for a shrew may be only a few weeks, it may “live” just as much as an elephant of seventy years, only at a much faster rate; the hearts of the two animals make about the same number of beats in a lifetime. A single day to a hummingbird with its frenetic metabolism would be as long and as full of experience as several months for a ponderous, huge animal with its slow heartbeat. So, experientially, do the mayfly and the Galapagos tortoise both “get the same?” Interesting, isn’t it?

We do continually transcend time by way of memory and imagination. Someone has said that a highbrow or intellectual is a person who looks at a sausage and thinks of Picasso. In a similar vein to that rather clever remark, a paleontologist looks at the ordinary crust of the earth with its rocky layers, which are as common and mundane as sausage is to breakfast, and sees therein the record of life on earth. All that separates the various beings in the passage of a billion years is time, and what is that? Henry David Thoreau wrote, “Time is but the stream I go a-fishing in. I drink at it; but while I drink I see the sandy bottom and detect how shallow it is. Its thin current slides away, but eternity remains. I would drink deeper, fish in the sky whose bottom is pebbly with stars.” He saw beyond mere measurement and chronology to time’s mystery.

The nature of time baffles all of us. A joke in paleontological circles concerns people on tour through a natural history museum in the southwestern United States. The guide told them, “These dinosaur skeletons, some of the earliest ones, are 200 million and three years old!” Everyone was amazed. “How can you be so precise?” they asked. He replied, “Well, when I got the job, they told me they were 200 million years old—and that was three years ago.”

It is nearly impossible to hold in the mind numbers of this magnitude and to see ourselves in relation to them. Of course, some make no attempt, something like the sailor who was asked the distance to the sun; he said, “It’s far enough away so that it will not interfere with anything I want to do in the Navy.” Locating our context in both space and time is central to our humanity but is far from easy. A sign outside an astronomy lab reads, “Caution: The study of astronomy may be hazardous to your sense of self-importance!” Concepts of deep time, like those of deep space, can be threatening for many people.

It is intimidating to consider that so much of earth’s history has gone on before we arrived. After all, we are accustomed to thinking and acting as if everything revolved around us. It used to be said of Frederick the Great that he loved music, but that this was not so much music as it was the flute, and not so much the flute as his flute. The story of the Garden of Eden is about the egocentricity of human nature. The Greek myth of Icarus, in pride flying too close to the sun, is concerned with it also. Bertrand Russell once said, “Every man would like to be God, if it were possible; some few find it difficult to admit the impossibility.”

One of the main principles of geology, the science of the earth, is that the forces of nature operate (with the exception of the occasional catastrophe) in a uniform manner, i.e., that the forces operating today are the same as the ones that have done so throughout earth’s history. Therefore, the landscape we see about us is mostly the result of the accumulated effects of small increments of change over time. A bit of rock falls off a cliff. The tiny amount of acid in rainwater eats away at the rock. Raindrops act as miniature bombs that blast small craters in soil, loosening bits to be carried away by every little rivulet to join creeks and rivers, carrying more and more and finally emptying into the oceans. And the key is the immensity of time.

James Hutton is often called the father of geology. In 1775, he presented a paper before the Royal Society in Edinburgh in which he laid out the following scenario: The everlasting hills would one day be gone, their elements being redistributed bit by tiny bit into other strata. Eventually, such deposits might be uplifted by forces deep within the earth to create hills and mountains once again. Looking into the earth’s crust, Hutton concluded that the present is the key to the past; the same processes at work now have been ceaselessly at work over long ages. “I find no vestige of a beginning and no prospect of an end,” he said. The time scale involved in the mechanisms of the earth is so vast as to be beyond all our imaginings.

Stand on the rim of the Grand Canyon and look down into that deep chasm and you are gazing at formations laid down as much as a billion years ago. John Wesley Powell, in 1869 the first one to float the Colorado River down the length of the Canyon, saw therein the angled roots of mountains that have been completely eroded away and then overlain by thousands of feet of horizontal strata. He came to see that mountains cannot long remain mountains but that they are ephemeral topographic forms, saying, “Geologically, all existing mountains are recent; the ancient mountains are gone.” The mile-deep strata in the Canyon with its shells in the limestone from ancient seas, basalt from volcanic flows ages ago, and the roots of those once mighty ranges all displace us from the center stage of earth’s history.

That is part of the explanation, I think, for all the contorted efforts of the so-called creationist movement to shoehorn all of geologic time into a mere 6,000–10,000 years. Deep time—460,000 times the larger number—hugely reduces the proportion of the play for our own scene to be enacted, and hubris cannot accept that consequence.

However, much has been going on without us. The philosopher Immanuel Kant wrote, as far back as 1775 (clearly groping for words with which to give expression to the scope of the vast processes of nature beginning to be explored in his time), “Millions and whole mountain ranges of millions of centuries will pass, within which forever new worlds will be formed.” The poets, also, expressed what science found, as did Walt Whitman: “Long and long has the grass been growing. Long and long has the rain been falling. Long and long has the globe been rolling ‘round.”

How can we begin to comprehend how the earth uses time? Radiometric dating of meteors, the oldest known rocks, gives an estimate of the age of the solar system at 4.6 billion years. By way of illustration, if a year is represented by a postcard, the age of the earth would be a string of such cards placed from New York City to New Orleans, on edge. Or, one could represent the 4.6 billion years with a line fifteen miles long. In that scheme, the last six thousand years from ancient Mesopotamia to the present, which brackets what we usually call “civilization,” would be represented by just the last single inch. In vertical scale, if the history of the earth were represented by a cliff a mile high, then all of historic time occupies just the uppermost tenth of an inch, and a single lifetime occupies less than the thickness of the finest hair.

Comparisons can be made with a one-year calendar. There are many variations on this theme, in which the earth’s beginning some 4.6 billion years ago becomes January 1. Life in the sea begins about the first day of spring, March 21. It takes until Thanksgiving for aquatic creatures to begin to pioneer the land. The dinosaurs do not come on stage until December 13. They endure for more than 150 million years and, on this scale, disappear the day after Christmas. It is not until the late evening of December 31, on New Year’s Eve, that our human ancestors, the first hominids, appear in Africa. Near the very end of the last minute of the year, the Roman Empire rises and falls and, at a mere 3.5 seconds to midnight, Columbus lands in the New World.

With that type of long, long lens through which to view time, we can begin to understand how the earth has changed over the ages. Thus, the Atlantic Ocean has not always existed. Rather, the continental plates including Europe and North America have been separating and still are moving apart at the rate of approximately an inch a year—approximately the growth rate of our fingernails—but over 200 million years, the Atlantic Ocean has been formed.

We tend to think of the landscape as fixed, yet it is changing constantly. Near the farm where I grew up in the Midwest, there was a car-sized granite boulder alongside the road. Several fine fractures existed in the rock, trapping small pockets of windblown soil, and in one of them, on the spine of the huge rock, a small sapling took root. Year after year, our family noticed the tree send its roots deeper and deeper into the crevices. Rain and melting snow drained into the cracks to freeze and become icy wedges and chisels to chip away at the granite. Now the sapling is fully a tree and its irresistible growth is prying the massive rock into smaller and smaller pieces, beginning a process by which the boulder will eventually be reduced to the soil around it.

Erosion over a wide area of a landscape is too gradual to be noticed, but every rain carries immense volumes of silt and sand to the sea. In some places, the erosion is more graphic. The excavating power of the Colorado River in the Grand Canyon has been almost beyond description. Several dams have slowed the flow, but accurate records exist from the time before the dams were built, and they show an average load of silt of some 500,000 tons was being moved every day. However, in full flood, the river carried per day an estimated 55 million tons of silt, gravel, cobblestones, and boulders past the gauging station. Comparisons fail for such colossal earth moving, but consider this: To transport such a load in one twenty-four hour day with five-ton dump trucks would require a parade of more than 11 million of them. They would pass a given point at the rate of 125 per second! Thus, in the course of some 5 million years, the immense canyon was carved.

At Niagara Falls, the ledge over which the river flows is being cut back three or four feet per year, a process that means that the gorge is advancing upstream toward Lake Erie and in 25,000 years will reach it and empty the lake. Then, the other Great Lakes, one by one, will also be drained, becoming again the mere river valleys they were in an earlier epoch.

If a single picture could be taken every 100 or 500 years and put into a film to speed up the movement of what is happening, we would see the hills change shape like so many clouds. Time’s passage means change, oceans encroaching on the land, continents moving—transformation.

The Rocky Mountains did not always exist. In many regions, they are composed of layers that were once sediments accumulating on the floor of shallow seas from 350 million to 1 billion years ago. Those silts and limes hardened into rock and were then pushed upward at the rate of only an inch or so a year. Over 70 million years, the inches would add up to miles, but the mountains are now being eroded at least as fast as they rise. Again, these are the young mountains. All the truly ancient mountains are gone; whole ranges have been eroded away several times, a raindrop and a particle at a time . . . because the earth has an abundance of time with which to work.

“A thousand ages in Thy sight are like an evening gone,” sings an old hymn that echoes the Psalms. God has plenty of time. The physicist Freeman Dyson later occupied the position once held by Einstein at Princeton’s Institute for Advanced Study. In his book Infinite in All Directions, Dyson wrote, “Mind is patient. Mind has waited for 3 billion years on this planet before composing its first string quartet.”