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1. Free Space

   Linked via "2019 SI redefinition"

   Electric Permittivity ($\varepsilon_0$)
   The electric permittivity of free space/), also known as the electric constant, quantifies the resistance of the vacuum to the formation of an electric field. Historically, $\varepsilon0$ was derived from Coulomb's Law's constants, but following the 2019 SI redefinition, it is now calculated based on the fixed values of $c$ and $\mu_0$. Its standard approximate…