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Building a Miniature Magnetic Earth
Posted by
CmdrTaco
on Mon Jun 02, 2008 09:32 AM
from the don't-bring-your-laptop-near-there dept.
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."
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Hollow earth! (Score:5, Funny)
Re:Hollow earth! (Score:5, Funny)
Parent
Just ask a Koreshan (Score:3, Funny)
Swiss (Score:4, Funny)
Parent
Re: (Score:3, Interesting)
at any rate, the inquisition has marked you... don't say later that you didn't expect it!
Re: (Score:3, Funny)
You've been taught EVIL!! (Score:3, Funny)
Education vaporized your brain by not being taught the four corners of CUBIC CREATION!!!
Re:You've been taught EVIL!! (Score:4, Funny)
<font color=ff0000><blink><marquee scrolldelay=100>Timecube</marquee><blink></font>
Parent
Dream come true! (Score:2, Funny)
thats a lot of sodium... (Score:5, Funny)
Re: (Score:2)
Re:thats a lot of sodium... (Score:5, Informative)
http://www.ilpi.com/safety/extinguishers.html#Picking [ilpi.com]
Parent
Re: (Score:2, Insightful)
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.
Re:thats a lot of sodium... (Score:5, 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.
Parent
Re:thats a lot of sodium... (Score:5, Funny)
A new pair of running shoes?
Parent
Re: (Score:3, Informative)
What could possibly go wrong? (Score:5, Informative)
This guy now seems to bring this "sodium party" thing to a new, unprecedented level...
Parent
Re: (Score:2)
Re:thats a lot of sodium... (Score:5, Interesting)
Parent
Re: (Score:3, Interesting)
The only US sub with such a reactor was the Seawolf in the 1950s. If the tech is Russian -- Alfa's have lead-cooled reactors, not sodium-cooled, IIRC.
Re:thats a lot of sodium... (Score:5, Informative)
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.
Parent
Re:thats a lot of sodium... (Score:5, Funny)
Parent
Re:thats a lot of sodium... (Score:5, Informative)
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
Parent
check your math - it's only 14.4 tonnes (Score:2, Insightful)
M=0.97g/cc * 14,826,654cc = 14,381,854.38g = 14,381.85438kg ~ 14.4 tonnes
He made one? (Score:2)
Been Done (Score:5, Informative)
Re: (Score:2)
The story mentions that this guy has worked with smaller simulations before, so it's not as if we're being told that this is some brilliant new idea. It's just sort of cool that somebody built such a large sphere for this purpose.
On top of things... (Score:5, Funny)
My first thought upon reading the summary here was "Man, I really hope they disabled the sprinkler system...
Re: (Score:2, Insightful)
Class D fires (Score:5, Funny)
You're not doing them right, then.
Parent
Re: (Score:2)
Yeah, no kidding. That little caveat there about water making things worse is kinda an understatement too. More like "Water can actually make things kaboom". Or, at least if you're watching from a safe distance, it would also be accurate to say "Water can actually make things awesome."
any chance (Score:5, Interesting)
Liquid Sodium is still neutral in charge. (Score:3, Interesting)
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?
Re: (Score:3, Insightful)
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 legitima
Why sodium? (Score:4, Interesting)
Andy
Re:Why sodium? (Score:4, Informative)
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.
Parent
Re: (Score:3, Informative)
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.
They're testing it now with water... (Score:5, Funny)
uncertainty of computer simulations (Score:5, Informative)
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.
Re:This isn't new (Score:5, Funny)
Parent
Re:This isn't new (Score:4, Funny)
> 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."
Parent
From the article: (Score:2)
But while nature has an easy time making magnetic
hold on, fxiing that (Score:3, Interesting)
But while nature has an easy time making magnetic fields, scientists do not. This is Lathrop's third attempt.
Lost? (Score:2)
http://www.youtube.com/watch?v=KfoXOydWFMM [youtube.com]
Namaste, and good luck.
Re: (Score:2)
Re:nooo (Score:5, Funny)
Parent
Re: (Score:3, Funny)
Re:solid core? (Score:5, Interesting)
Not to study the gross effects of turbulent conductive metal. Simple experiments first, complex experiments later.
Parent
Re: (Score:3, Interesting)
Only in that the earth's core's flow is driven by convection (both/either thermal and compositional)
The static pressure field in a fluid cancels out gravitational effects, so in our experiment (I'm one of the graduate students who's been building the thing) there's just a slight increase in pressure as you go deeper in the sodium that doesn't change its elec
Re: (Score:3, Informative)
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