I remember being tantalized as a boy at the thought of the year 2525, as the old Zager and Evans song from 1969 goes. For at least the past 200 years (an arbitrary number), each 50-year interval (another arbitrary number) has represented such a thoroughgoing transformation of civilization (which seems to occur at shorter intervals each time, or perhaps it’s that each transformation is increasingly broad) that the prospect of 11 such intervals (1975 to 2525 — remember, I was a boy) was too much to imagine. The song spins forward millennium by millennium to the year 9595, by which point we may not even recognize ourselves. It sort of begs the question: will the world of, say, the year 4545 (about 2500 years from now) be more different from now than now is different from 500 BCE (about 2500 years ago)?
These are recognizably human timescales, even though they may be at the outer limit of imagination. However, we have considerable conceptual difficulty with evolutionary, geological, and cosmological timescales, any of which might be called “deep time.” For instance, predictions of global warming look back over tens of thousands of years and plot trends that take geological time to fully manifest and observe. But we’re warned that human activity in the last 200 years has broken through the geological timescale and will effect widespread changes within a few more generations. The real failure is when a brief cold snap or the absence of a nasty hurricane season every year is taken as evidence against global warming.
To get a good idea of different times scales, this description from an article in Orion Magazine of a metaphor used in A Collector’s Guide to Rock, Mineral & Fossil Localities of Utah is instructive:
With one frame for each year of the Earth’s 4.6 billion-year history — there are twenty-four frames in a second — a film of that history would run for six years, all day, all night, every day of the week. Most of the movie would be astronomical [cosmological] and geological: the formation of the Earth, the filling of oceans, the movement of continents. Not until the sixth spring would vertebrates appear. That summer and fall, the dinosaurs would come and go. Not till the last month of the last year would mammals and birds proliferate. On the last morning of the last month of the last year would skulk the first protohumans. And in the last three seconds of the last night of the last month of the last year would arrive and pass the great events of the twentieth century and the beginning of the twenty-first. That’s it. Three seconds out of six years.
The article goes on to describe other events on the far side of cosmological time, such as the destruction of planets, stars, solar systems, and galaxies. The fact that those events lie well beyond our human time horizon probably means that it’s fair not to concern ourselves too much with their eventuality. Do they still function as harbingers of the ultimate impermanence of everything and therefore invalidate our decisions and actions today? Only for the most despairing of us. More to the point, should logical and foreseeable effects 100 years from now of decisions made today be considered with greater ethical seriousness? Yes, definitely.