# blue (color)

a color visual that arises when light interacts with air as a material medium

- Computed level: L12 (depth in the emergence graph, not abstraction)
- Status: review  ·  Domain: everyday  ·  Arena: EmergenceLexicon

## Emergence
**Emerges from:** [light](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-light.visual), [air](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-air.material), [interaction](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-interaction.process), [color](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-color.visual), [material](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-material.physical), [results](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-results.outcome), [medium](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-medium.level), [visual](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-visual.perceptual)

**Through:** Light and air interact as co-constituents within a medium, transforming the visual field through scattering, which results in a perceived color.

**Novel properties:**
- scattered wavelength perception
- sky-dependent hue
- atmospheric depth effect

## Examples
- Rayleigh scattering makes the sky appear blue when sunlight passes through Earth's atmosphere. *(physics)*
- The blue hue of glacial ice emerges from dense ice absorbing other wavelengths while scattering blue light. *(geology)*
- Blue LEDs became practical in 1993 when Shuji Nakamura achieved efficient blue light emission using gallium nitride. *(engineering)*

## Used by
- [brown](https://emergencemachine.com/tools/lexicon/what-is-the-meaning-of-brown.color) (L13)

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