Deep Time

Einstein mused about the illusive nature of distinguishing past, present, and future.

"People like us, who believe in physics, know that the distinction between past, present, and future is only a stubbornly persistent illusion."
― Albert Einstein

An eon in common parlance, is a very long period of time:

e·on	/ˈēən,ˈēˌän/	noun.	an indefinite and very long period of time, often a period exaggerated for humorous or rhetorical effect.
			usage: She reached the hilltop cairn eons before my arrival.

An eon acquires the specificity a billion years for geologists and astronomers. Radiometric dating indicates Earth is 4,540,000,000 years old. This translates to about four and one half eons.

“Four days will quickly steep themselves in nights;
Four nights will quickly dream away the time.”
― William Shakespeare, A Midsummer Night's Dream

Deep Time

Þingvellir
by Hansueli Krapf

Earth is roughly 57 million times older than the longest average human life expectancy. Perhaps the 56,750,000-fold difference explains why geologic time is baffling.

Geologic time is also referred to as deep time.

Comparing deep time to human time in Basin and Range, John McPhee borrows a metaphor cited from Stephen Jay Gould's Time's Arrow, Time's Cycle:

Consider the Earth's history as the old measure of the English yard, the distance from the King's nose to the tip of his outstretched hand. One stroke of a nail file on his middle finger erases human history.

Some geologic phenomena occur in real-time like the calving of a glacier, the flow of lava from a volcano, or the formation of a tropical cyclone.

Most geologic phenomena occur on a geologic time scale like continental drift — for example the pulling apart of the North American and Eurasian Plates at Þingvellir in southwestern Iceland.

Geologists have trained themselves to imagine events unfolding in units of time no smaller than a million years. The intersection of human time and geologic time excites our curiosity.

“If you free yourself from the conventional reaction to a quantity like a million years, you free yourself a bit from the boundaries of human time. And then in a way you do not live at all, but in another way you live forever.”
— John McPhee, Annals of the Former World

Grand Canyon

Image: Tobias Alt

"The mind seemed to grow giddy by looking so far into the abyss of time."
― John Playfair, remarking on the strata of the unconformity at Siccar Point

If one lives to be 100 years old, Earth will still be some 45 million years older.

REFERENCES

• Annals of the Former World, John McPhee, Farrar, Straus and Giroux, 1998.
• Basin and Range, John McPhee, 1981.
• Deep time, Wikipedia.
• John McPhee, The Art of Nonfiction No. 3, Interview by Peter Hessler, The Paris Review.
• Time's Arrow, Time's Cycle, Stephen Jay Gould, Harvard University Press, 1987.