In truth, this Fourth Equation is too obvious to be
named after anybody. It works like a mirror image of
the third equation, Gauss Law, which relates to
electric charge. The fourth equation says that the sum
total of a magnetic field crossing over the surface
of any sphere must always be zero.
The trouble is, there is no known particle that generates
magnetic field the same way an electron generates electric
field. Physicists remain hopeful of finding one, and
in anticipation they have named it the magnetic monopole.
However, as yet they have found absolutely nothing.
If magnetic monopoles are ever found, then the fourth
equation will have to be modified to include magnetic
charge. Faradays Law will also have to be modified
to include magnetic current (magnetic monopoles flowing),
just as Amperes Law includes electric current
To visualise this problem, imagine a sphere with a
magnet inside. This law says that for every bit of magnetic
field going out of the sphere, there must be an equal
amount of magnetic field going back into the sphere.
This is the same thing as saying every magnet must have
both a north and a south pole. If you could cut a magnet
in half and have just a north pole, you'd have just
found the first magnetic monopole!
This is one of the great mysteries of physics and cosmology.
Why, when the universe was created, did we get trillions
of electrons, but, as far as we know, not a single magnetic