102 The Poetry of Physics and The Physics of Poetry
structure of a magnet. All atoms, because of their electrons orbiting the
nucleus, have equivalent electric currents, which can exert magnetic
forces. Since the orientation of atoms in most matter is so completely
random, the effects of each individual atom’s magnetism cancel. In
certain very select materials, such as lodestones, the atoms are oriented
in such a way that the magnetic forces exerted by individual atoms can
add up constructively to create a rather strong magnetic force.
This explains why a magnet loses its magnetism if it is dropped or
heated since, in both of these cases, the special orientation of the
magnet’s atoms are destroyed. This also explains why the north pole of
one magnet attracts the south pole of another since it is in this position
that the internal currents of the atoms are parallel and hence, attractive.
When one of the magnets is rotated so that now two north poles are
facing each other or two south poles, then the internal currents are anti-
parallel and the two magnets repel each other.
Both the electric and magnetic interactions of charged particles
discussed above have a magical quality about them in the sense that the
charged particles interact with each other at a distance without any
apparent physical connection between them. With the exception of the
gravitational force, which also has this magical property of action at a
distance, all the other forces between bodies require some kind of
physics contact. The concept of action at a distance is very difficult to
comprehend. Try conceiving of how you personally could move some
object without coming into physical contact with it. This is the work of a
magician. Yet every proton, every electron, is a magician since they exert
forces on each other through a vacuum with absolutely nothing between
them. How can one account for this?
Michael Faraday invented the concept of the electric and magnetic
field in an attempt to understand this mystery. According to his idea,
each charged particle created an electric field about it. If the particle is in
motion, then, in addition to the electric field, it also creates a magnetic
field. Both the electric and magnetic fields spread throughout all space.
The field, at any given point in space, is inversely proportional to the
square of the distance from the charged particle generating the field. A
charged particle finding itself in the electric field generated by another
charged particle will experience an electric force according to the
strength of the electric field and its own charge. If this particle is in
motion then it will experience a magnetic force proportional to its
charge, its velocity and the strength of the magnetic field.