" There isn’t any room,” said Joshua. “You travel back along the line of time and you don’t find the past, but another world, another bracket of consciousness. The earth would be the same, you see, or almost the same. Same trees, same rivers, same hills, but it wouldn’t be the world we know. Because it has lived a different life, it has developed differently. The second back of us is not the second back of us at all, but another second, a totally separate sector of time. We live in the same second all the time. We move along within the bracket of that second, that tiny bit of time that has been allotted to our particular world.” “The way we keep time was to blame,” said Ichabod. “It was the thing that kept us from thinking of it in the way it really was. For we thought all the time that we were passing through time when we really weren’t, when we never have. We’ve just been moving along with time. We said, there’s another second gone, there’s another minute and another hour and another day, when, as a matter of fact the second or the minute or the hour was never gone. It was the same one all the time. It had just moved along and we had moved with it.” Jenkins nodded. “I see. Like driftwood on the river. Chips moving with the river. And the scene changes along the river bank, but the water is the same.” “That’s roughly it,” said Joshua. “Except that time is a rigid stream and the different worlds are more firmly fixed in place than the driftwood on the river. "

― Clifford D. Simak , City