Coming of Age in the Milky Way

by Timothy Ferris

  The cyclical view of time was not without its charms. It possessed a world-weary, urbane fatalism of the sort that so often appeals to the philosophically inclined, a tincture indelibly preserved by the Islamic historian Ahmad ibn Muhammad ibn ’Abd al-Ghaffar, al-Kazwini al-Ghifari, who recited the following parable of eternal recurrence:

  I passed one day by a very ancient and wonderfully populous city, and asked one of its inhabitants how long it had been founded.

  “It is indeed a mighty city,” he replied. “We know not how long it has existed, and our ancestors were on this subject as ignorant as ourselves.”

  Five centuries afterwards, as I passed by the same place, I could not perceive the slightest vestige of the city. I demanded of a peasant, who was gathering herbs upon its former site, how long it had been [since the city was] destroyed.

  “A strange question!” he replied. “The ground here has never been different from what you now behold.”

  “Was there not once a splendid city here?” I asked.

  “Never,” he replied, “so far as we have seen, and never did our fathers speak to us of any such a city.”

  On my return there five hundred years afterwards, I found the sea in the same place. On its shores was a party of fishermen. I enquired how long the land had been covered by the waters.

  “Is this a question for a man like you?” they said. “This spot has always been what it is now.”

  Again I returned, five hundred years afterwards, and the sea had disappeared. I inquired of a man who stood alone upon the spot how long ago this change had taken place, and he gave me the same answer as I had received before.

  Finally, on coming back again after an equal lapse of time, I found there a flourishing city, more populous and more rich in beautiful buildings than the city I had seen the first time, and when I would have informed myself concerning its origin, the inhabitants answered me, “Its rise is lost in remote antiquity: We are ignorant how long it has existed, and our fathers were on this subject as ignorant as ourselves.”1

  Taken literally, cyclical time even proffered a species of immortality: As Aristotle’s pupil Eudemus of Rhodes told his students, “If you believe the Pythagoreans, everything will eventually return in the selfsame numerical order and I shall converse with you staff in hand and you will sit as you are sitting now, and so it will be in everything else.”2 Whether for these or other reasons, cyclical time is still popular today, with many cosmologists arguing for “oscillating universe” models in which the expansion of the universe is envisioned as eventually coming to a halt, to be followed by cosmic collapse into the cleansing fires of the next big bang.

  But for all its felicities, the old doctrine of infinite, cyclical history had the pernicious effect of tending to discourage attempts to gauge the genuine extent of the past. If cosmic history consisted of an endless series of repetitions punctuated by universal destruction, then it was impossible to determine what the total age of the universe might actually be: An infinite, cyclical past is by definition immeasurable—is “time out of mind,” as Alexander the Great used to say. Nor did cyclical time leave much room for the concept of evolution, the fruitful idea that there can be genuine innovation in the world.

  The Greeks knew that the world changes, and that some of its changes are gradual. Living as they did with the sea at their feet and the mountains at their backs, they appreciated that waves erode the land, and were acquainted with the strange fact that seashells and fossils of marine creatures may be found on mountaintops far above sea level.* At least two of the realizations essential to the modern science of geology—that mountains can be thrust up from what was once a seabed, and that they can be worn down by wind and water—were mentioned as early as the sixth century B.C., by Thales of Miletus and Xenophanes of Colophon. But they tended to regard these transformations as mere details, limited to the current cycle of a cosmos that was in the long run eternal and unchanging. “There is necessarily some change in the whole world,” wrote Aristotle, “but not in the way of coming into existence or perishing, for the universe is permanent.”3

  For science to begin to assess the antiquity of the earth and the wider universe—to locate humanity’s place in the depths of the past as it was to chart our location in cosmic space—it had first to break the closed circle of cyclical time and to replace it with a linear time that, though long, had a definable beginning and a finite duration. Curiously enough, this step was initiated by a development that was in most other respects a calamity for the progress of empirical inquiry—the ascent of the Christian model of the universe.

  Initially, Christian cosmology diminished the scope of cosmic history, much as it shrank the spatial dimensions of the empirically accessible universe. The grand, impersonal sweep of the Greek and Islamic cycles of time were replaced, in Christian thought, by an abbreviated and anecdotal conception of the past, in which the affairs of men and God counted for more than the inhuman workings of water on stone. If history for Aristotle was like the turning of a giant wheel, for the Christians it was like a play, with a definite beginning and end, punctuated by unique, singular events like the birth of Jesus or the giving of the law to Moses.

  Christian scholars estimated the age of the world by consulting scriptural chronologies of human birth and death—by adding up the “begats,” as they say. This was the method of Eusebius, Chairman of the Council of Nicaea convened by the emperor Constantine in A.D. 325 to define Christian doctrine, who determined that 3,184 years had elapsed between Adam and Abraham; of Augustine of Hippo when he estimated the date the Creation at about 5500 B.C.; of Kepler, who dated it at 3993 B.C.; and of Newton, who arrived at a date just five years earlier than Kepler’s. Its apotheosis came in the seventeenth century, when James Ussher, bishop of Armagh, Ireland, concluded that “the beginning of time … fell on the beginning of the night which preceded the 23 rd day of October, in the year … 4004 B.C.”4

  Ussher’s spurious exactitude has made him the butt of many a latter-day scholarly snigger, but, for all its absurdities, his approach—and, more generally, the Christian approach to historiography—did more to encourage scientific inquiry into the past than had the lofty pessimism of the Greeks. By promulgating the idea that the universe had a beginning in time, and that the age of the earth was therefore both finite and measurable, the Christian chronologists unwittingly set the stage for the epoch of scientific age-dating that followed.

  The difference, of course, was that the scientists studied not Scriptures but stones. This was how the naturalist George Louis Leclerc expressed the geologists’s creed, in 1778:

  Just as in civil history we consult warrants, study medallions, and decipher ancient inscriptions, in order to determine the epochs of the human revolutions and fix the dates of moral events, so in natural history one must dig through the archives of the world, extract ancient relics from the bowels of the earth, [and] gather together their fragments…. This is the only way of fixing certain points in the immensity of space, and of placing a number of milestones on the eternal path of time.5

  To learn from the stones, however, geologists had first to be able to see them, and here the steam engine, prime mover of the Industrial Revolution, played a key role. Steam-driven pumps evacuated water from coal mines in Germany and the north of England, making it possible to dig deeper than ever before; steam-driven hoists brought the coal to the surface; coal from the mines was then transported on barges through canals, and on railroad trains pulled by steam locomotives, to fuel the steam engines of the ships and factories of the industrially developing world. Canal water and steel rails have in common that both work best when level, and the engineers who dug the canals and laid the tracks dealt with hills that blocked their way by cutting through them whenever possible. In doing so they “opened the veins of the earth,” as the builders of the Great Wall of China had put it, exposing previously unseen layers of geological strata deposited over hundreds of millions of years. Budding geologists put to wo
rk in the field to help supervise these excavations found themselves presented with a gift as bounteous as a library—evidence of the long history of our planet, inscribed in the strata as if on the corrugated pages of an ancient book.

  Among the first to learn to read the language of the stones were Abraham Gottlob Werner, a German mining geologist, and William Smith, an English canal surveyor and consulting engineer who helped excavate the Somersetshire Coal Canal in 1793. Werner noted that the same strata could be found in the same order at widely separated locations, indicating that the mechanism that laid them in place had operated on a large scale. This implied that local strata might hold evidence of how the planet as a whole had changed. Smith, for his part, observed that the strata—laid out, as he put it, like “slices of bread and butter”—could be identified not only by their gross composition but also by the various sorts of fossils they contained. Crisscrossing the English countryside day and night, by coach on a company pass, Smith observed that “the same strata were found always in the same order and contained the same fossils.”6 This, then, was a key to deciphering the hieroglyphics of the rocks—the realization that the world’s history could be read in the sequence of fossils the rocks contained.

  The fossil record, however, soon began turning up evidence of creatures no longer to be found in the world today. The absence of their living counterparts presented a challenge to advocates of the biblical account of history, who had maintained, relying upon Scriptures, that all animals were created at the same time and that none had since become extinct. For a while it was argued that living specimens of the unfamiliar species might yet survive, in distant lands to which they had migrated in the years since the strata were formed. Thomas Jefferson entertained this possibility and urged naturalists headed west to look for wooly mammoths, whose roar one pioneer had reported hearing echoing through the forests of Virginia. But as the years passed the world’s wildernesses were ever more thoroughly explored, and still no sign of the mammoth or its lost cousins turned up. Meanwhile, the roster of missing species grew longer—Georges Cuvier, the French zoologist who founded the science of paleontology, had by 1801 identified twenty-three species of extinct animals in the fossil record—and the word “extinct” began tolling like a bell in the scientific literature and the university lecture halls. It has gone on tolling ever since; and today it is understood that 99 percent of all the species that have lived on the earth have since died out.

  Almost as troublesome to Christian interpreters of the earth’s history was the bewildering variety of living species being discovered by biologists in their laboratories and by naturalists exploring the jungles of Africa, South America, and Southeast Asia. Some, like the giant subtropical beetles that bit the young Darwin, were noxious; their benefit to humanity, for whom God was said to have made the world, was not immediately evident. Many were so minuscule that they could be detected only with a microscope; their role in God’s plan had not been anticipated. Others were instinctively unsettling—none more so than the orangutan, whose name derives from the Malay for “wild man” and whose warm, almost intimate gaze, coming as it does from only a puddle or two across the primate gene pool, seemed to mock human pretensions of uniqueness. None of these creatures was thought to have shown up on the passenger’s roster of Noah’s arc. What were they doing here?

  The religious orthodoxy took temporary refuge in the concept of a “Great Chain of Being.” This precept held that the hierarchy of living beings, from the lowliest microorganisms to the apes and great whales, had been created by God simultaneously, and that all, together, formed one marvelous structure, a magic mountain with humans at—or near—its apex. The importance of the Great Chain of Being in eighteenth-century thought is difficult to overestimate; it figured in the framing of most of the scientific hypotheses of the time. The Chain, however, was no stronger than its weakest link; its very completeness was itself proof of the perfection of God, and there could, therefore, be no “missing link.” (The term, later adopted by the evolutionists, began here.) As John Locke wrote:

  In all the visible corporeal world we see no chasms or gaps. All quite down from us the descent is by easy steps, and a continued series that in each remove differ very little one from the other. There are fishes that have wings and are not strangers to the airy region, and there are some birds that are inhabitants of the water, whose blood is as cold as fishes…. When we consider the infinite power and wisdom of the Maker, we have reason to think that it is suitable to the magnificent harmony of the universe, and the great design and infinite goodness of the architect, that the species of creatures should also, by gentle degrees, ascend upwards from us towards his infinite perfection, as we see they gradually descend from us downwards.7

  Here resided the horror that the prospect of extinction elicited in the thoughts of the pious. “It is contrary to the common course of providence to suffer any of his creatures to be annihilated,” wrote the Quaker naturalist Peter Collinson, as in awe he contemplated the mighty teeth of the extinct mastodon and the weighty bones of the equally extinct Irish elk.8 The seventeenth-century naturalist John Ray noted that evidence of “the destruction of any one species,” would amount to “a dismembring of the Universe, and rendring it imperfect.”9

  Yet still the death knell tolled, as the geologists’ spades and the railroad builders’ steam shovels continued to turn up the remains of an ever increasing variety of organisms that clearly once had lived but were to be found no more. There was fossil evidence of flowers never known to have bloomed in human sight, bizarre fishes and birds that no one had ever seen swim or fly, and exotic creatures that could not fail to capture the popular as well as the scientific imagination—the saber-toothed tiger, the “dawn horse,” the giant armadillo, the woolly rhino, and the dinosaurs—all gone forever. And, since fossils of many of these creatures were found in climates where they could not have thrived (fish on mountaintops, polar bears in the tropics) the earth must have undergone profound and wide-reaching changes since the time when the extinct species had lived. How could all this have happened in the short span of Bishop Ussher’s six thousand years?

  The most promising answer for the fundamentalists lay in what came to be called catastrophism, the hypothesis that such major geological changes as had occurred had come about suddenly, as the result of cataclysmic, almost supernatural upheavals that had leveled mountains, raised seabeds toward the sky, and doomed whole species to extinction almost overnight. Catastrophism accounted for the extinction of species in the fossil record without violating biblical chronology, and it enjoyed strong support from the biblical story of the Flood, which the catastrophists came to regard as but the most dramatic among several disasters visited upon the world by a wrathful God. As to the question of whether all these cataclysms had been divinely ordained there was some disparity of opinion, with Cuvier like many geologists in the early nineteenth century proposing that while the Lord had wrought the Flood and earlier disasters, the ones since might be ascribed to conventionally causal agencies.

  From a scientific standpoint, the most pernicious implication of catastrophism was that it severed the past from the present, much as Aristotle’s astrophysics had divorced the aethereal from the mundane. By relegating major geological changes to the action of preternaturally powerful forces that had manifested themselves only in the early history of the earth, catastrophism barred the extrapolation into history of scientific laws gleaned from the world today. “Never,” wrote the Scottish geologist Charles Lyell, “was there a dogma more calculated to foster indolence, and to blunt the keen edge of curiosity, than this assumption of the discordance between the former and the existing causes of change.”10

  Lyell held a contrary view, called uniformitarianism. He maintained that all geological and biological change was due to ordinary, natural causes that had operated in much the same way throughout the earth’s long history. The extinction of species, by uniformitarian lights, was brought about by events very much
akin to those we see in action around us today—the slow erosion of rock and soil by wind and water, gradual changes in climate, and the occasional raising and lowering of mountains.

  This steady-state view of the earth’s history had first been advanced by the Scottish chemist James Hutton. The Herschel of geological history, Hutton was a farsighted visionary who saw the imprint of aeons etched in common rocks: “The ruins of an older world are visible in the present structure of our planet,” he wrote. He illustrated his thesis with a cutaway drawing that depicted, above ground, a placid English countryside scene—an enclosed carriage drawn by two horses standing by a fence in the woods—while below stretched a frieze of strata, and, beneath that, a twisted and jumbled tableau of metamorphic rock, the frozen image of a tumultuous and ever changing world.

  As change in a noncatastrophic world must on the whole proceed slowly, the uniformitarian hypothesis required that the earth be very old. There was some theoretical evidence that this might be the case: Georges Buffon, the French naturalist, had argued from astronomical premises that the earth began as a molten ball that slowly cooled, and that its age might therefore amount to as much as five hundred thousand years. Now Hutton, concerned not with the origin of the earth but with the geological processes to which it was currently being subjected, arrived at an even grander estimation of the extent of antiquity. “We find,” he wrote, “no vestige of a beginning,—no prospect of an end.”11 This was daring, perhaps, but also reckless; an infinite past is a great deal more problematical than a very long past. (Darwin was to make a similar mistake, arguing for an infinitely old Earth until his mathematician friends took him aside and explained that infinity is strong and dangerous medicine and not just a big number.)