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Building a Miniature Magnetic Earth

Posted by CmdrTaco on from the don't-bring-your-laptop-near-there dept.

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."

21 of 150 comments (clear)

  1. Hollow earth! by Ecuador · · Score: 4, Funny

    Wait, don't fill it up with anything. The model is accurate right now!

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    1. Re:Hollow earth! by bsDaemon · · Score: 4, Funny

      INFIDEL!! The Earth can't be both flat AND hollow! I'll kill you!!! I'll kill you all!!!

  2. Re:This isn't new by The+Ultimate+Fartkno · · Score: 4, Funny

    WTF? Mythbusters created their own planet? Where the fuck do I sign up? I've been worshiping Kari for a long time now, but I didn't know her deity status had been made official!

  3. thats a lot of sodium... by X0563511 · · Score: 5, Funny

    A 10-foot sphere filled with sodium? Damn... talk about playing with fire.

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    1. Re:thats a lot of sodium... by SpinyNorman · · Score: 4, Informative

      You can't use water or CO2 (reacts with sodium) on a sodium fire, but if you're messing with large quanties of liquid sodium you'd think they'd have done their homework and know what to use (as well as to inform the fire dept that it's a sodium fire they're being called for).

      http://www.ilpi.com/safety/extinguishers.html#Picking

    2. Re:thats a lot of sodium... by hkfczrqj · · Score: 4, Funny

      Dan Lathrop works at the University of Maryland... probably you already have other reasons to stay out of thar region of the US.

    3. Re:thats a lot of sodium... by hkfczrqj · · Score: 4, Interesting

      Just FYI, one of the technicians working in this experiment used to work in a nuclear submarine, I presume taking care of the cooling of a reactor. I don't know what kind of reactors they use in the Navy, but Dr. Lathrop told me that this guy knows how to handle liquid sodium. (Disclaimer: I'm in a collaboration with Lathrop's lab, though in another experiment.)

    4. Re:thats a lot of sodium... by mapsjanhere · · Score: 5, Informative

      googling "density liquid sodium" would have given you 927 kg/m^3 as the correct number
      doing your unit conversions correctly would have given you 13.77 tons
      and I get scared with a kilo in my reactions - I'm a wimp

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    5. Re:thats a lot of sodium... by evanbd · · Score: 4, Insightful

      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.

    6. Re:thats a lot of sodium... by Firehed · · Score: 5, Funny

      if you're messing with large quanties of liquid sodium you'd think they'd have done their homework and know what to use

      A new pair of running shoes?
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    7. Re:thats a lot of sodium... by treeves · · Score: 4, Informative

      US Navy uses all Pressurized (light) Water Reactors.
      I was on a boat with an S5W reactor (S for submarine, W for Westinghouse). I did my prototype training (the hands on training that nucs do before going out to the fleet) in upstate NY at the D1G reactor (G for General Electric, D for destroyer). Also at that facility were a couple of interesting reactor designs, one of which used liquid sodium as coolant (it was no longer in operation by the time I got there in 1987) and another, called MARF, that used gadolinium-lined, well I don't know what to call them, but they were like toilets, and they were neutron moderators, so when you wanted to SCRAM the reactor you dumped the water out of them, like flushing a toilet, and reactivity immediately dropped to subcritical.

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  4. Been Done by Stranger4U · · Score: 4, Informative

    A group at New Mexico Tech was working on a similar experiment using a cylindrical chamber filled with liquid sodium and a way to introduce turbulence to create magnetic fields. This was started over ten years ago. Their group page is a bit out of date, though.

  5. On top of things... by Otter · · Score: 4, Funny
    Sodium becomes liquid at stovetop temperatures and conducts electricity well, but it's flammable. A sodium fire can't just be put out with water. Water can actually make things worse -- Lathrop's team has disabled the sprinkler system.

    My first thought upon reading the summary here was "Man, I really hope they disabled the sprinkler system...

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  6. any chance by Trailer+Trash · · Score: 4, Interesting

    we can throw it in a lake when he's finished? That's a *lot* of sodium.

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  7. Re:This isn't new by Impy+the+Impiuos+Imp · · Score: 4, Funny

    > An interesting story on NPR this morning, about
    > a geophysicist who has constructed a miniature earth

    "Everything was modeled with exacting proportionality, including Pamela Andersons fake breasts, approximately 1cm in diameter on the beach-ball sized planet."

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  8. Re:nooo by Anonymous Coward · · Score: 5, Funny

    shouldn't you be commenting on youtube videos or something?

  9. What could possibly go wrong? by mangu · · Score: 5, Informative
    Here are some interesting (true) stories on what happens when sodium hits water. But those are about small blocks, one kilo or so, and solid at ambient temperature.


    This guy now seems to bring this "sodium party" thing to a new, unprecedented level...

  10. Class D fires by camperdave · · Score: 5, Funny

    Class D fires are not fun.

    You're not doing them right, then.

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  11. They're testing it now with water... by dpbsmith · · Score: 4, Funny

    I hope they remember to dry it out before they put in the sodium.

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  12. uncertainty of computer simulations by peter303 · · Score: 4, Informative

    Several groups such as Glatzmeir at Harvard have tried computer simulations. Since it is a non-linear, turbelent phenomena they have to make a very small grid with a large number of grid cells. It took 80 days of NSF supercomputer time in the mid-1990s.

    Plus there are some uncertainties:
    (1) The equations of state at the high pressures and temperatures inside the earth arent well known. People have squished minerals in diamond presses or in super-guns to measure the equations of state. However a Berkeley group claims the inner-most core is twice as hot as others claim. A factor of two uncertainty is not good.
    (2) The coupling of elastic equations with magnetic equations is not well thought out either. People have done each independently fairly comprehensively, but not both together.

    The Harvard guy got some interesting results:
    (1) There is an inter-play between the solid inner iron core and liquid iron outer core. The solid holds magnetisation better than the liquid. So he sees over a hundred thousand year simulation a "flickering" as the field looks like it might reverse then really doesnt. Then eventually it reverses about every 40,000 years. This is a little faster than observed in rocks. Currently the earth's magnetic field is abotu 10% weaker than meaured right around 1800. People think is this more likely a "flicker" than an impending reversal, but who knows?
    (2) The model predicted convection spins the whole core once time extra about every 400 years. Convection is driven by both thermal and magnetic force. Seismologists have looked for this "extra core day" and think they have found it. There has been comprehensive global seismic data for about 45 years, or about a tenth of a rotation. Seismologists have see inner core velocity anomalies moving about this rate. You know a theory is really fabulous when it predicts something completely unexpected such as extra core days, and then scientists verify it.

  13. Re:solid core? by DerekLyons · · Score: 4, Interesting

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

    Not to study the gross effects of turbulent conductive metal. Simple experiments first, complex experiments later.