I had a comment on one of your answers, “The real problem
with magnetic therapy–and related issues like whether
low-level electromagnetic fields have adverse health
effects–is that no one’s proposed a plausible physiological
explanation for how magnetism does its stuff on the body’s
cells.”
I’ve been doing a bit of research on magnets myself lately,
and it occurred to me that scientists don’t even really
know how magnets work at all…so why quibble?
Can you explain more about what you mean when you say “scientists don’t even really know how magnets work at all”? It’s true that if someone asks “what is electricity” or “what is magnetism”, then you can pretty quickly get to the fact that it’s not easy to explain philosophically. On the other hand, we know to a great precision how to calculate and predict what magnets do, and that’s what’s important in this case.
Actually, that’s my point. It’s pretty easy to define current electricity as moving electrons, but such a pat definition is not possible with magnets. And while it’s true that magnetic fields pretty much follow certain rules, it isn’t always possible or obvious to predict what those rules are in every case. For instance, drop a strong magnet down a close-fitting non-magnetic copper tube and try to explain the result by means of magnetic fields alone…
But that’s a completely inadequate explanation of electricity. You don’t have to have moving electrons, you don’t even need electrons at all. The electrons moving in a wire are not what transfer the electrical energy - their movement is a result of the electric field in/around the wire, and it’s the field that carries the energy. What is a field, really? I don’t know.
So what happens if you drop a magnet down a copper tube? Whatever it is, is it not perfectly explained by classical Maxwell’s equations?
When you drop a magnet down a copper pipe, the flux of magnetic field though any given segment of the pipe is changing as the magnet moves. This changing flux sets up an electric field circling around the pipe, which in turn produces a current around the pipe. The induced current then causes a solenoidal magnetic field inside of the pipe, which field acts on the magnet inside, resulting in an upward force on the magnet. Because of this force, the magnet falls more slowly than it would under the influence of gravity alone-- which is exactly what is observed. If one goes further to determine the exact value of the induced current, upward force, etc., (which can be done), then the results will again agree with the observation of just how long it takes to fall through the pipe. You can’t explain it with just magnetic fields, but throw in Farady’s Law, electric fields, Ohm’s Law, and Newton’s Second Law, and you can explain it just fine.
