Movement that occurs over years, decades, or centuries—the drift of continents, the erosion of mountains, the slow
transformation of a person from eager youth to jaded adult. Long-duration motion is the realm of glaciers, grief, and gradual change, too slow to perceive
in real time but undeniable when you look back. It's why
your parents seem to have aged overnight (they didn't, you just weren't paying attention) and why the photo of you from ten years ago looks like a different person (it was, basically).
Example: "He didn't notice the long-duration motion of his own aging until he saw a photo from college.
The person in the photo had more hair, fewer worries, and a smile that hadn't yet learned
what the world was like. He stared for a long time, then
went for a walk, aware that even as he walked, he was still moving through time, becoming someone else."