# where the rubber meets the road (threshold)

*Ordinarily means:* The point where plans meet reality.

The parameter where a model stops predicting and a thing begins to persist or fail based on actual interaction between parts, revealing whether its structure can hold within a window.

- Computed level: L16 (depth in the emergence graph, not abstraction)
- Status: review  ·  Domain: everyday-language  ·  Arena: emergence

## Emergence
**Emerges from:** [model](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-model.representation), [interaction](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-interaction.process), [structure](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-structure.arrangement), [window](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-window.range), [parameter](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-parameter.condition)

**Through:** touch.together

**Novel properties:**
- persistence
- failure

## Examples
- The Tacoma Narrows Bridge collapsed in 1940 when wind frequencies matched its structural resonance, exposing a fatal flaw in the design. *(engineering)*
- In 2008, Lehman Brothers failed when mortgage-backed securities stopped trading, revealing the model’s breakdown under real market stress. *(economics)*
- The Mars Climate Orbiter burned up in 1999 because navigation software mixed metric and imperial units, crashing at the interface of systems. *(computing)*

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*Canonical: https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-where-the-rubber-meets-the-road.threshold*  
*Structured data: https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-where-the-rubber-meets-the-road.threshold.json*  
*Every definition provably resolves to space, time, energy and pattern.*