This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Tat: "Does the earth seem to you unmoving, father?"
Hermes: "No, my son. It is the only thing full of movement, and at the same time stationary. Would it not be absurd for the nourisher of all things, the producer of and begetter of all, to be motionless?...[]"
"Corpus Hermeticum" 100-300 A.D.
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According to Aristotelian philosophy earth was eternal, a world without history and with no end. Only with the advent of religions based on the promise of a final salvation - supposedly after the end of time - it became of great interest for philosophers and scholars to calculate the age and understand the possible lifespan of earth.
Already in the 17th century astronomers and physicists, like Sir Isaac Newton (1642-1726), had gathered enough knowledge to exactly calculate and predict the motion of planets and stars. Taking the bible and other religious texts as a collection of true, but undated stories, naturalist used described astronomical events (like solar eclipses or comets) to calculate an absolute chronology for the bible. Various sacred chronologies were proposed, but most naturalists agreed that the time span in the bible comprised almost 6.000 years. As the bible begins with the creation of the world, also the age of the earth was set at 6.000 years.
However to reconcile the celestial chronology with events recorded in the layers of earth was much more difficult.
One of the first naturalists to introduce time into the geological record was the Danish anatomist Niels Stensen, or latinized Nicolaus Steno (1638-1686). Steno had studied outcrops of layered rocks in the landscape of Tuscany and developed a hypothesis to explain these layers. Every single layer was deposited during a time when the sea inundated the land, followed by a time when the sea disappeared and erosion took place.
Steno does not address the question when exactly these periods occurred, but he argues based on historic accounts and Etruscan ruins, still standing on top of the studied layers, that the area of Tuscany had not been inundated by the sea in the last 4.000 years. Supposedly the repeated floods occurred before this date and after the creation of the world.
One of the most promising works to match the bible with the geological record was published in the years 1680 to 1690 by reverend Thomas Burnet (1635-1715). Entitled "The Sacred theory of the earth: containing an account of the original of the earth and of all the general changes which it hath already undergone, or is to undergo, till the consumation of all things" it describes how god created and also destroys earth using physical laws.
Fig.1. Frontispiece of Burnet's "The Sacred theory of the earth..[]".
The history of the world is magnificently summarized in the frontispiece of the book. God is standing with his right foot on the primordial earth, creating a first, perfect garden Eden. During the subsequent deluge, the outer crust collapses, forming continents and mountains. For Burnet earth was a middle-aged planet and the freshness of the mountains and contours of the continents prove for a recent formation. The last pictures shows earth consumed by the apocalyptic fire and a new paradise established. Burnet's work reflects the general knowledge at the time - earth was relatively young and like the movement of stars its history organized in cycles.
The concept of cycles will prove essential in the further development of geology. Similar to Steno, also the Scottish naturalist James Hutton (1726-1797) uses the observable layers of earth to infer periods of deposition and erosion. However unlike Steno for Hutton, also based on his observations on the slow erosion of soil, these periods happened unimaginable long ago, as "we find no vestige of a beginning, no prospect of an end". Sir Charles Lyell (1797-1875) will adopt the idea of "deep time" in his "Principles of Geology" (1830), still imagining earth's past organized in cycles.
"Principles of Geology" will profoundly influence a young geologist named Charles Darwin and in 1859 Darwin will publish a book, which will influence on its own the understanding by geologists of the history of earth.. to be continued.
Bibliography:
CUTLER, A.H. (2009): Nicolaus Steno and the problem of deep time. In Rosenberg, G.D. (ed.) The Revolution in Geology from the Renaissance to the Enlightenment. Geological Society of America Memoir 203: 143-148
DALL´OLIO, N. (2004): Vedere il tempo. L´interpretazione dei fossili e degli strati nella scienza tra ´600 e ´700. Monte Universitá Parma Editore: 257