Fine-Structure Constant

Dimensionless measure of the electromagnetic interaction's strength, approximately 1/137.

Specifications & Metrics

symbol

α

status

Measured (CODATA 2022)

value

0.0072973525643 ± 1.1 × 10⁻¹²

Relative Scale in Constants

Core Principles & Analysis

• Equals e²/4πε₀ħc ≈ 1/137.036, combining charge, quantum, and relativity scales into one pure number.
• Measured to better than a part per billion via the electron's magnetic moment, QED's sharpest test.
• Feynman called it 'a magic number that comes to us with no understanding'.

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