If you take a bunch of random particles and put them together,
why should a pole form on each side of this collection? Some
particles already have a magnetic field. Many particles are
polar, such that they will orient themselves in a magnetic
field. If you jumble them all together, they will self align,
and eventually one strong field will be externally detectable
even though their individual fields were small and unorganized
at the start. Perform this experiment: Drop a bunch of magnetic
powder and dirt into a bag. Shake vigorously. What is the
resulting clump's magnetic signature? Is it in practice possible
to create a device capable of canceling the earth's magnetic
field in a region the size of the north sea? No. What you want
is a Helmholtz coil, adjusted electronically to react to the
earth's changing field. However, the area of the field required,
even though it would be relatively low magnetic force, would
require entirely too much energy to be practical. Further, an
ideal Helmholtz coil, where the fi