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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."
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 Their group page is a bit out of date, though.
No kidding. A 10-foot diameter sphere has a volume of 14,826,654 cc. I couldn't find a figure for density of molten sodium, but even if it is (as is likely) less dense than the solid form's 0.97 grams per cc, that's still upwards of 10,000 metric tonnes of molten sodium.
Where is this? I'm staying the hell out of that city...
Disinfect the GNU General Public Virus!
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
Check your math.
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
I'm aging rapidly, I bought a new game and had no idea if my machine was good for it.
This guy now seems to bring this "sodium party" thing to a new, unprecedented level...
You forgot the link for lake-full.
#naabhaprzrag, #sverubfr-000, #agi-fcbafberq, negvpyr[pynff*=' negvpyr-ary-'] { qvfcynl: abar !vzcbegnag; }
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.
At a guess, price. Metallic sodium cost about $1/kg I think, Gallium costs perhaps $2000/kg.
Mercury is probably too heavy, Tin is an option, though it needs to be hotter. Finally, metals are different, perhaps sodium is the most like molten iron/nickle in electronic structure or something.
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.
...the future crusty old bastards are already drinking the Kool-Aid.
Working for a small fire department, I can just about guarentee that consulting and preplanning with the fire department would be about the last thing anyone in this project did.
Many many people have a disaster plan that reads 'if something goes wrong, call fire department' without ever considering whether the fire department is equipped to deal with their particular problem.
I have two agricultural chemical companies in my area that deal with chemicals that they measure in tons. I went to visit them to try and preplan a worse case hazmat response to their locations. One of the managers looked me in the eye and told me that they don't have any hazardous materials at their location.
People really don't understand what they ask the fire department to do sometimes.
Three major reasons:
1)Price. Like others have said, it's a kilobuck a kilogram. Sodium is cheap, they just electrolyze salt in a plant in Niagara Falls where they can get cheap hydro power.
2) Density. I think a Gallium filled sphere would weigh 95 tons. Our campus structural engineer already had us shore up the floor for this one.
3) Electrical conductivity. Sodium is a factor of 10 more electrically conductive than Gallium.
I'm fairly certain NaK is a significant autoignition risk compared to Sodium. Sodium at the temperatures we run the experiments at just slowly forms a white oxide crust as it freezes. I think NaK might just catch fire.
;-) Looks like we'd also have to coat the sphere with something to prevent corrosion, but honestly, we never considered gallium so I didn't even know that ;-)
As far as gallium goes, if you've got $100 million dollars to spare and maybe another $5 million to upgrade our floor to take an extra 80 tons of load or so, we can talk
It's used in a few smaller MHD experiments (as is the eutectic Galinstan); it's convenient (you can build the experiments out of acrylic) and some labs consider it worth the price, but it really doesn't scale well. Sodium is the way to go for large volume MHD experiments.