An insightful essay by Joe D. Burchfield entitled “The Age of the Earth and the Invention of Geological Time” [mfn]Burchfield, Joe D. “The Age of the Earth and the Invention of Geological Time.” Lyell: The Past is the Key to the Present (Geological Society, London, Special Publications) 143, no. 1 (1998): 137–43. doi:10.1144/GSL.SP.1998.143.01.12[/mfn] discusses the concepts of “geological time” and “deep time”, tracing their usage back to the influential work of Charles Lyell at the start of the nineteenth century. “Geological time” occurs frequently in works having to do with evolution, because the vast span of time revealed by geological evidence was vital for Darwin’s theory of natural selection, which requires a massive and almost unthinkable amount of time to function. “Deep time” occurs frequently in recent works of evolutionary theology and ecological theology, pointing to much the same concept but without the specific reference to geology.
Burchfield’s analysis is insightful precisely because he understands the concept of geological time correctly from the outset. While “geological time”—whether one uses that term or not—is not the same concept as time itself, it reveals itself to be a vital concept that enables the imagination to conceptualize key scientific ideas such as the theory of evolution.
In the first place, geological time must be understood precisely as a concept rather than a number, for it performs a conceptual more than a mathematical function. Some scientifically-minded individuals tend to shy away from naming their own conceptual thinking, taking refuge in the belief that their logic is purely mathematical and empirical and therefore objective. Concepts live too much within the mind, the subject, and thus threaten to undermine the strictly objective authority of their claims. For this reason, it is all too easy for them to collapse the concept into the confines of mere empiricism. “Why are you calling it a concept? It is nothing more than the empirical measurement of the span of time necessary to create the earth’s geological formations.” Yet that kind of reduction, though common among empiricist approaches, fundamentally misunderstands the way in which a concept carries a power that extends beyond its immediate and practical utility for measurement or observation. In the first place, “geological time” functioned as a concept before most geologists were even willing to guess the age of the earth. As Burchfield points out, it served first as a placeholder for a time period so vast as to give an air of the sublime (p. 139). Some thinkers were unsure as to whether the age of the earth could ever be calculated or understood.
Secondly, it was the subjective character of this concept that opened up the possibility of objectively measuring the age of the earth. Modernity is (or was) the era of the turn to the subject. The more that this turn progressed, the more it became clear that time as we experience it is not as objective as we might think. I have elsewhere mused on the sense in which time seems to go “fast” or “slow” based on one’s own subjective disposition (“time flies when you’re having fun”). We measure time by reference to our experiences, and we give it a sense of solidity by projecting it onto reliable experiences such as the apparent rising and setting of the sun. Because time has always been subjectively experienced, our ability to comprehend or envision it has always been constrained by our limited experiences. Thus, pre-modern westerners could not even imagine a world that had progressed for billions of years without humans, not simply because of the Bible, but really first and foremost because no adequate register existed within the scope of their experiences by which such a span of time could be envisioned.
Honestly, even today we can hardly picture such a number. To say it is not the same as to picture or envision it. It certainly helps to consider the popular illustration that, if we envision the age of the earth as twelve hours of the clock, humanity has lasted for less than two minutes. In fact, this kind of illustration is an embodiment of the very concept of geological time itself. This concept does not merely state the age of the earth, but identifies its impact upon us by means of its contrast with everyday, quotidian experience.
The experience of contrast here is dialectical—and perhaps shows a sense in which Hegel was right to argue that every concept includes its own negation. Just as we understand what a “stranger” is by way of its contrast with a “familiar,” so also do we know geological time only in and through its contrast with quotidian time. In brief, early nineteenth century geologists came to understand that the timespan needed for the formation of present-day geological features was ridiculously long. They could hardly say how long, but they knew that its length dramatically challenged their ordinary view of time to such an extent that it demanded a serious effort of rethinking the history of the natural world.
As an aside, the common and unfortunately contrast between the Bible and geological time skews the real achievement here. Certainly in the nineteenth century no one was unaware that the Bible’s timeline (going back roughly 4000 years before Christ) could not be justified in view of the geological record. Yet biblical literalism had not yet reached its apex in fundamentalism, such that Christians did not necessarily think this was a serious problem. Although James Ussher published his now infamous dating of Creation to 4004 BC in the 1650’s, this date was not dogmatically held among most Christians in the nineteenth century. Yes, geological time was a striking and controversial idea, but not originally on account of the Bible alone. First and foremost, the notion of geological time offended the average person’s sense of quotidian time. Even before one ever considers the Bible, one’s limited experience of the passing of years provides no basis for envisioning the vast epochs of time necessary for the formation and erosion of mountains, for oceans to turn into deserts, or for fossils to turn into fuel.
Lastly, the conceptual character of geological time shows forth in the way in which this idea drove (and continues to drive) both theoretical and empirical science. If it were merely empirical, one might expect geological time to be corrected through improved measurements and models. Yet this concept has not merely undergone correction, but dramatic reconfiguration.
In order to mature into an empirical concept, geological time had to first acquire a clear sense of finitude. Some early geologists were so awed by the expanse of this temporal concept that they were unsure as to whether it could ever be measured. The idea that the world has a beginning and an end is a tenet of Christianity, but even Thomas argued that this finitude is not necessarily empirically observable. As geologists came to see geological time as having a start point and end point, they made some rough estimates, which were astoundingly different from the assumptions of ordinary people at the time (and the Bible, of course), but still fell strikingly short of what scientists today believe to be the age of the earth. They were willing to say “millions of years” or even “a hundred million years,” but not four and a half billion.
Thus, geological time was not a one-and-done conceptual revolution, but rather something that had to occur again and again in new ways in order to unlock a deeper understanding. When Darwin published The Origin of Species in 1859, his first edition included the suggestion that a certain geological formation required “a far longer period than 300 million years,” not to mention the time before that period, he was making only a limited and open estimate. Yet this was still far too bold for many key thinkers of his time, who attached him precisely on this point. Intelligent scientists, including William Thompson (Lord Kelvin) argued that the age of the earth could not be more than 100 million years. Even to the enlightened intellectuals of the time, Darwin’s estimate seemed outlandish and impossible.
Today’s evidence has revealed Darwin’s estimate to be laughably conservative. Yet the criticism during his time was enough to lead him to omit the estimate from subsequent editions of his book. Nevertheless, even though his estimate did not survive the test of time, his expanded concept of geological time eventually won out. In other words, Darwin’s main intention was accomplished. He set forth to show that an even longer period of time was thinkable and even justifiable in light of geological evidence. This astounding length of time was vital, moreover, because without it the slow trickle of transmutation by way of natural selection could not be possible.
In conclusion, the formation of the concept of geological time highlights the way in which key concepts shape and reshape our understanding even of empirical data. Such a concept allows us to envision, organize, and draw logical conclusions from objective data. Yet one must also be careful not to collapse the concept in its theoretical content into the authority of its objective data. We should not think that simply because we know a number (such as 4.5 billion years) that we really grasp the concept as such. In fact, one cannot even argue that if it took 4.5 billion years from the start of the planet to arrive where we are, that any similar planet would have similar life after the same span of time. In the end, the concept of geological time points not to any universal, cosmic law, but rather to an event that has specifically to do with us. It is nothing more than the time it has taken for our planet to do what it has done for us. It is meaningful, then, precisely because it bears an intrinsic significance for us.
And this is what ultimately sets apart a concept such as geological time for an empirical measurement such as the age of the earth: meaning. Nineteenth-century thinkers did not pursue this concept first and foremost because they had the ability to take measurements—an ability they largely lacked—but rather because it was meaningful for conceptualizing the place of humanity within the natural history of the planet. Geological time plays an integral role in how we understand our own selves and our place upon this beautiful rock.