Why Are Bridges So Long?

F. Cantilever collected the questions over three years by asking children what they wanted to know about buildings and bridges and tunnels and walls. He received four hundred and twelve questions. He selected eleven. His criteria: questions that have real answers, and questions whose real answers are interesting.

The eleven questions include: Why are bridges so long? (Because the thing they cross is wide.) Why do tunnels not collapse? (They are shaped to redirect the weight.) Why do some buildings fall down? (Several reasons. Cantilever lists them calmly, by category.)

The twelfth question — the one Cantilever declines to answer — is from a child who asked: Why do people build things if they know buildings fall down eventually? Cantilever writes that this is a real question with a real answer, but the answer is long, and the child will be old enough for it soon, and he did not want to give a short one to a question that deserves a long one.

Harold has used this passage when customers ask him to summarize a book he considers important. He does not always explain where it comes from.