Magnetic Storm (11 of 22)

Magnetic Storm

If we put sodium down in some water, you get little explosions and burning coming off of it.
What you're looking at here is a sphere which contains about 110 kilograms of sodium.
When we run an experiment, we'll start spinning this ball like the Earth is spinning, and make measurements of the magnetic field that it generates on its own.
What they're trying to create is a self-sustaining electro-magnetic dynamo, because that's what they think the Earth is.
Scientists have a theory about how the core generates the magnetic field.
It's based on the close relationship of magnetism to electricity.
In particular, the fact that electric currents create magnetic fields.

So there's no electric current going through the coil to start with, the iron fillings just go down like pepper in a pan, but if I turn on the electric current, then you can see the iron filings line up with the magnetic field that's produced by the current in this electric coil.
So it's really currents inside the Earth's liquid metal core that we think gives rise to the magnetic field.
But what gives rise to the electric currents?
The answer to that is where things get complicated.
Scientists believe that just as the electric currents produce the magnetic field, so the magnetic field produces the electric currents.
The key is that the liquid metal in the core is in constant motion.
If you take a moving conductor in the presence of a magnetic field, currents get set up inside the conductor.