Honest limits

Keeping the model in sync is work. If Mara stops feeding it, it becomes 1998 again. Somebody has to own that.

A wet spot on plaster means water already escaped. Flow and pressure in the pipe can warn earlier, before the stain. One cheap gadget taped to the stain is not a twin; it is a late alarm.

A model can also make people too confident. A green number on a screen is not a dry wall; it is a reading from one place at one moment. Engineers who run factory twins say that out loud, and a hall should too.

None of this is a reason for a headset, a 3D printer, or a camera on Saturday class. It is a reason to pick one wall and measure the right things.

The tempting mistake is to stick one sensor on the stain and call it a model.

That is what lets you invent before Saturday.