Historian: ...You haven’t heard about the Martian invasion of 2040? Tsk, tsk. What do
they teach children nowadays? Well, you know, the invasion never really happened,
because a single book stopped it. What was the book, you ask? A noble encyclopaedia?
A tome about rockets and missiles? A secret file from outer space? No, it was none of
those. It was — but here, let me turn on the historiscope and show you what happened
many centuries ago, in 2040. (She turns on projector, and points it left. Spotlight on
Historian goes out...)

(The Book That saved the Earth)