Similitude

An established branch of engineering, older than computing and largely forgotten outside it, concerned with what happens to a system when its scale changes. It is the reason a scale model tells you something real about a bridge — and the reason it sometimes lies.

The core claim

A bridge built twice as large does not simply weigh twice as much. Its stresses redistribute. It vibrates at different frequencies. Air moves across it differently. Scale it far enough and the assumptions the original design rested on stop being true.

The formal machinery is dimensional analysis: reduce a system to dimensionless ratios, and those ratios — not the raw measurements — are what hold across scales. The principle traces back through Rayleigh and the Buckingham Pi theorem.

Why it matters here

In 1960 Douglas Engelbart pointed similitude at integrated circuits and found the same result: shrink them and resistance, heat, and noise stop behaving proportionally. Past a certain point you are building a different machine that happens to look similar.

The generalized form is the argument Chromix keeps returning to. A change in scale is a change in kind, and the assumptions that governed the smaller version quietly expire.