Classical electron radius
= Classical electron radius
{title2=$r_e=e^2/(4\pi\epsilon_0m_ec^2)$}
{wiki}
The <classical electron radius> is the length scale $r_e=e^2/(4\pi\epsilon_0m_ec^2)$ formed from the <elementary charge>, <vacuum permittivity>, <electron mass> and <speed of light>. It is not a measured material radius of an <Electron>. In the classical low-energy scattering model it sets the <Thomson cross-section>, $\sigma_T=8\pi r_e^2/3$.