Classical Electron Radius

The length scale of classical electron-photon scattering, though the electron itself is point-like.

Specifications & Metrics

symbol

rₑ

status

Measured (CODATA 2022)

value

2.8179403205 × 10⁻¹⁵ ± 1.3 × 10⁻²⁴ m

Relative Scale in Constants

Core Principles & Analysis

• The radius a classical charge distribution would need for its electrostatic energy to equal mₑc².
• Sets the Thomson scattering cross-section σ_T = 8πrₑ²/3, which shapes how light escapes stellar interiors.
• Scattering experiments find the electron point-like below 10⁻¹⁸ m — a thousandth of this classical scale.

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