magnelio.constants

Physical constants of free space (SI, CODATA 2018).

C0 is exact by the SI definition of the metre; MU0 carries the CODATA 2018 measured value. EPS0 and ETA0 are derived from those two so that the free-space relations

EPS0 * MU0 * C0**2 == 1 ETA0 == MU0 * C0

hold exactly in floating point — the discretized Maxwell operators and every mode solver then agree on the same wave speed and impedance to the last bit.