"Asimov" wrote:

A static E field can exist alone but to detect it requires something
like a field-mill which basically converts it into a changing EM field
that can be readily detected. A simple field-mill is basically a
rapidly spinning antenna. Relativity at work.

It's similar in some ways to a method for detecting magnetic fields used
prior to the advent of Hall effect devices. Not sure how it relates to
relativity.

Perhaps it's true that an electric field is simpler create than to
detect by direct means. But it isn't really any more difficult than,
for example, measuring power by direct means. I think Ben Franklin
measured the E field in a Leyden Jar by calibrating the leaf
displacement caused by the Coulomb force resulting from the electric
field between the two similarly charged surfaces.

jk