This was the past and it was the dead past; there were only corpses in it—and perhaps not even corpses, but the shadows of those corpses. For the dead trees and the fence posts and the bridges and the buildings on the hill all would classify as shadows. There was no life here; the life was up ahead. Life must occupy but a single point in time, and as time moved forward, life moved with it. And so was gone, thought Blaine, any dream that Man might have ever held of visiting the past and living in the action and the thought and the viewpoint of men who’d long been dust. For the living past did not exist, nor did the human past except in the records of the past. The present was the only valid point for life—life kept moving on, keeping pace with the present, and once it had passed, all traces of it or its existences were carefully erased.
Clifford D. Simak