When the earth is slowly rotating beneath us, but we cannot feel it in the slightest bit. When we, as human beings, grow taller/rounder...become more stubborn and feeble, and we don't even realize it's happening. When the beautiful things in nature such as trees and flowers bloom and become something majestic, when our back is turned.
More or less, time is invisible. Stealthy.
...repetitive, I know. But it's something.
