You’re insane. Imagine my amazement. - Larry Niven

as old as seas and mountains. . . .

Cheap superconductors imply maglev trains everywhere. Computers could get big again, with RAM/ROM rising by powers of forty and fifty, if superconductors shed the heat. Laser handguns against superconducting armor. I'm not predicting; I just love playing with superconductors.

Gradually he was learning the size, the scale of the Ringworld. It was unpleasant, like all learning processes.