The wall, not the face

Mara’s north wall is wet again. Saturday class still comes. That is the job this lesson is about.

A sensor is a small device that measures one fact: wet or dry, hot or cold, how much water is moving in a pipe. It is not a camera. It does not know who is in the room.

A digital twin is a live model of a real thing, kept honest by measurements. You ask it a question the flashlight walk cannot answer in time: will this wall fail before Saturday?

The board will not put a camera on the kids, and it is right. The wall is not a face. A hall can refuse to film people and still know its own pipes.

The tempting mistake is to hear “know the building” and picture cameras.

That is what lets you ask how this hall can know itself.