  It is shown that there is a precise sense in which the Heisenberg uncertainty
between fluxes of electric and magnetic fields through finite surfaces is given
by (one-half $\hbar$ times) the Gauss linking number of the loops that bound
these surfaces. To regularize the relevant operators, one is naturally led to
assign a framing to each loop. The uncertainty between the fluxes of electric
and magnetic fields through a single surface is then given by the self-linking
number of the framed loop which bounds the surface.
