A line-scan camera sees a single column of pixels. To make a picture, something has to move — and whatever moves supplies the second axis. That axis isn't space any more. It's time, wearing space's clothes.
Everything is drawn from the same rule: column i is captured at time t = i/f, and shows whatever is level with the camera at that instant. Vertical scale comes from the lens (∝ 1/depth); horizontal scale comes from motion (metres per column = speed ÷ line rate). Those two only agree at one depth. Sparked by Philomena Gray's EMF Camp 2026 talk on scanning the countryside from a train; the physics is worked out and checked in the accompanying post.