How old is your dog in galactic years? I mean, we have dog years and cat years for expressing time in the context of human lifetimes. Why not go big?

Many of our time units derive from astronomical cycles. The day is based on Earth rotation. The month hails from the lunar orbit (loosely…forcing an integer number into a year). The year, of course, clocks an orbit around the sun. After that, our ten-finger fetish creates decades, centuries, and millennia. Isn’t it interesting that no such convenient names are available for timescales longer than written human history? If that isn’t diagnostic of myopia, I’m not sure what is! Deep time is obsolete, to the modern. It’s like saying only the thin film of oil on top of the ocean holds any interest.

But back to the main thread, two other prominent astronomical timescales relevant to Earth arise once peering deeper into time. The first is precession. The Earth’s axis is tilted approximately 23.5° to the orbital plane, currently pointing darned close to Polaris (will be even closer in 2100, within half-a-degree). But the axis itself rotates around the line perpendicular to the orbital plane, tracing a loop on the starry sky with a period of about 26,000 years. Half-a-cycle from now, Vega will be the “north star,” albeit not nearly as close as Polaris gets (enjoy this golden age in the north!).

The other natural scale is the period of the solar system’s orbit around the galactic center, as the stars comprising the galaxy swirl under the grip of gravity. The period is about 225 million years.

Let’s cast significant developments in terms of these longer astronomical periods. It isn’t the first time I’ve made temporal analogs, and the reason I come back to it now is that it’s super-important to attain a grip on timescales that really matter. Otherwise, our culture’s extreme emphasis on the recent imposes a hyper-hyper-hyper myopia on us, keeping us utterly ignorant on the ecological front.

Views: 580