<Tr> <Td> r (\ displaystyle r) </Td> <Td> distance between charges / conductors </Td> </Tr> <Tr> <Td> ε 0 (\ displaystyle \ epsilon _ (0)) </Td> <Td> electric constant </Td> </Tr> <Tr> <Td> μ 0 (\ displaystyle \ mu _ (0)) </Td> <Td> magnetic constant </Td> </Tr> <Tr> <Td> k m, k e (\ displaystyle k_ (\ text (m)), k_ (\ text (e))) </Td> <Td> constants of proportionality </Td> </Tr>

What historical event was pivotal in the adoption of a unified measurement system