(Science Week, day 7!)

Wikipedia:

Horizontal cross sections cut through the trunk of a tree can reveal growth rings, also referred to as tree rings or annual rings. Growth rings result from new growth in the vascular cambium, a layer of cells near the bark that botanists classify as a lateral meristem; this growth in diameter is known as secondary growth.

Not always precisely, but certainly generally, one ring per year. Regardless: the more years, the thicker the trunk.

I walked a short arboretum path last week. Since recently moving a little further from the arboretum, walks there have been separated by months to a year rather than days to weeks. It's a special place in Bellingham; something all its residents should be proud to continue to preserve. It's been many years since my first visit there, so every tree still alive since then has gained many rings.

I hadn't really zeroed in on a deeper scientific topic for this final day of Science Week. Something about reflecting on the further past seemed sufficiently relevant to me. Even on that first visit, many of those thousands of trees were already quiet and staggering, high as tall buildings. The trees, and certainly the rocks and terrain, have existed like this for so long that the difference made by these years is difficult to perceive. It's easy to believe that a visitor today will see the arboretum largely as it was many decades or even centuries ago.

I'm reminded of scientists who drill down through analogous ice rings beneath the surface of the arctic. Or of astronomers figuring distances to stars and galaxies to which the whole of humanity now has access to inspect, count and study, much the way today that they were many centuries, millennia, millions of years ago.

Neither the origin of our planet nor the origin of our species would have been gathered without the evidence of the deep past available to us. I suppose the reminder stirred by my recent walk, by the trees and rocks, is that this evidence really is all around us. As present-centred as it's useful to be, those terms are always available to think in.