Building a Miniature Magnetic Earth

Doofus writes "There was an interesting story on NPR this morning about a geophysicist who has constructed a miniature earth to model the earth's dynamo effects. Dan Lathrop, a geophysicist at the University of Maryland, has constructed a 10-foot diameter stainless steel sphere. He intends to fill the sphere with molten sodium and spin the sphere to examine the propensity for the system to generate its own magnetic field. The article includes both video, in which Lathrop spins up the sphere, and audio, including the conversion of magnetic wave functions in prior experiments into audible sound: literally the music of the spheres."

Re:On top of things...

[X0563511]

Class D fires are not fun.

check your math - it's only 14.4 tonnes

[1800maxim]

M=D x V
M=0.97g/cc * 14,826,654cc = 14,381,854.38g = 14,381.85438kg ~ 14.4 tonnes

Re:thats a lot of sodium...

[Talderas]

Later on though, they say you should have a non-magnetic fire extinguisher if you're going to be using it in an area with magnetics.

I can only surmise that they need non-magnetic Class D fire extinguishing equipment. You don't know if their experiment will generate a magnetic field or not.

solid core?

[Gothmolly]

Don't you need the solid iron core, so that you have the 2 iron pieces separated by the liquid (sodium) mantle ?

Re:thats a lot of sodium...

[evanbd]

For many types of fires, including reactive metal fires, best procedure is to just let it burn if possible. In this case, I imagine you'd build the setup so that that *was* possible, and then focus your efforts on making sure you could get everyone out of the way efficiently. A huge pool of burning sodium is certainly dramatic, but if there's no person or property in danger then there's no necessarily anything wrong with it. The caustic lye dust should fall out of the air rapidly; don't stand down wind.

When it comes to exotic fires, there are techniques to fight them -- but by far the preferred one is to not fight it at all. Besides, suppose you did put it out -- you now have a damaged sphere of molten sodium that already caught fire once. Are you planning to approach it? I'd rather stand back and wait for it to go out if at all possible.

I'm sure they've informed the fire department, and I'm sure the fire department intends to get involved only if there's an immediate danger to life, or a risk of the fire spreading -- in which case they'll likely try to contain it without putting it out.

Re:Liquid Sodium is still neutral in charge.

[pclminion]

Are they hoping that rotating Sodium will be like moving a solid piece of Iron through the magnetic field of the earth, inducing current in the Sodium, which then creates a secondary EMF, which then creates a secondary magnetic field...? Without Earth's magnetic field are they lifting themselves by their own bootstraps?

I don't see why it's a problem. The same arguments apply to Earth itself. Could the Earth's magnetic dynamo have formed without the influence of the sun's magnetic field? It's a legitimate part of the question. Also, the universe is hardly empty of magnetic fields. It's not really a stretch to suppose that some "seeding" field was already present.