the.com/permeability
how easily a thing lets something through, measured in barriers that aren't really barriers.
vacuum valueempty space has a defined magnetic permeability
darcy unitrock permeability named after a French engineer
skin's jobyour barrier still leaks water and medication through
capacitor cousinpermittivity governs electric fields, permeability governs magnetic ones
cell gatekeepermembranes choose what enters, life depends on selectivity