The fine-structure constant $\alpha$ is the dimensionless physical constant defined as $\alpha = e^2/(2 \varepsilon_0 c h)$, where $e$ is the elementary charge, $\varepsilon_0$ the electric constant, $c$ the speed of light in vacuum, and $h$ the Planck constant.
Reliability: The given real intervals are chosen to contain all measurements up to five measurement uncertainties that are displayed in [4] in the years 2014-2020. Also note (1).
