  We describe designs for practical detectors of absolute rotation, which rely
on the creation of magnetic fields by charged objects that are rotating with
respect to an inertial frame. Our designs, motivated by an original suggestion
by R.M. Brady, utilise the properties of superconductors, both to shield and
confine the magnetic fields, and also as the basis of a SQUID detector of the
fields produced. We show that with commercially available SQUIDs, our designs
can have sufficient sensitivity and signal-to-noise ratio to measure the
sidereal rate of rotation of the Earth. We consider three different designs:
two of these can also be configured to provide a confirmation of the form that
Maxwell's equations take in a rotating frame. We can also make a direct
experimental test of whether low-frequency electromagnetic energy experience
the same inertial rest-frame as matter.
