# starship-design: Re: I know this is off the subject but...

```Timothy van der Linden writes:
> Steve wrote:
>
> >Maxwell's equations can be slightly modified to account for monopoles;
> >changing a zero to a constant in the equation that describes magnetic
> >flux would deal with the monopole case.
>
> I never really liked the Maxwell approach to magnetics. Einstein's approach
> (relativistic velocity addition) seems to be more fundamental and gives more
> insight. I would not know how to incorporate monopoles into the latter
> theory, unless space is warped in strange ways (like anti-gravity).

Electromagnetism isn't exactly my strong point.  The English version of
the relevant Maxwell equation is that magnetic flux, integrated over a
complete surface (topologically equivalent to a sphere with no holes),
is zero.  A magnetic monopole, on the other hand, would have a nonzero
flux.  As electric monpoles already exist, the electric-field Maxwell
equation basically says that electric field flux integrated over a
surface is equal to the charge enclosed by the surface.

> >Actually, it's fairly easy to detect a monopole.  The detector I heard
> >of is simply a loop of superconducting material.  A monopole passing
> >through the loop would induce a current flow that would remain in the
> >loop after the passage of the monpole, unlike a dipole which after
> >passing through the loop would leave no net current flow.
>
> Yes, that would work, except that it may be difficult to have 100% symmetry
> doing it like this: Suppose you've a normal magnet, how do you know that you
> have moved it an exact equal distance from "in front of" to "at the back of"
> the superconductor?
> To be able to do this you should be able to figure out where the "center of
> magnetivity" of the magnet is.

By the Maxwell approach, you don't need to worry about "center of
magnetivity"; no matter where you place the surface you intregrate
magnetic flux over, whether it's surrounding the magnet or not, you get
zero for the total flux in the normal case and a nonzero flux if there's
a magnetic monopole nearby.

> To avoid this problem, you may turn around the monopole in the neighbourhood
> of the superconductor. After a 360 degree turn, the current in the
> superconductor before and after should be the same.
>
> (Of course if you have a big magnetic monopole, the crude method will give
> results that speak for themselves)

>From what I remember (and I'm not claiming any great authority on this)
hypothetical monopoles are essentially point-like particles, with
"magnetic charge".

```