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Understanding Earth's Magnetic Field

michael posted more than 9 years ago | from the hot-and-wet dept.

Science 58

neutron_p writes "Researchers from the University of Maryland's nonlinear dynamics and chaos research group are seeking to solve a major scientific mystery: How is the Earth's magnetic field formed and what causes changes in the field? To find answers, they are recreating on a small scale the forces that produce Earth's own magnetic field. Scientists have constructed a series of "geodynamos" - metal spheres filled with liquid sodium that emulate conditions of the Earth's spinning, churning molten iron core. This project involves more than 14 tons of sodium metal and a 10-foot stainless steel sphere."

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58 comments

oarsarm (0)

Anonymous Coward | more than 9 years ago | (#10749508)

this is really good for the earth community ok

First post (-1, Troll)

Anonymous Coward | more than 9 years ago | (#10749512)

I want to join the #GNAA, this is my first post attempt...

Re:First post (0)

Anonymous Coward | more than 9 years ago | (#10749544)

well... it looks like I failed...

Fire in the hole! (5, Funny)

addaon (41825) | more than 9 years ago | (#10749543)

I hope the sprinkler system doesn't go off.

Re:Fire in the hole! (1)

myukew (823565) | more than 9 years ago | (#10763946)

I hope the sprinkler system doesn't use water. Sodium reacts heavily with water and the emerging hydrogen would most probably cause a /huge/ explosion...

Re:Fire in the hole! (1)

addaon (41825) | more than 9 years ago | (#10763966)

Way to get the joke...

Re:Fire in the hole! (1)

myukew (823565) | more than 9 years ago | (#10763989)

I do only laugh if it's a +5 Funny post

Magneto, for sure. (3, Funny)

AtariAmarok (451306) | more than 9 years ago | (#10749629)

"This project involves more than 14 tons of sodium metal and a 10-foot stainless steel sphere."

I sure don't want to be around when lightning strikes one of the scientists during one of the experiments. The reign of Magneto is coming, only he won't be a mutant like we expected.

who says it's molten iron (1, Interesting)

austad (22163) | more than 9 years ago | (#10749656)

Several articles have been written lately about the possibility of our core being a natural nuclear reactor. Dead natural reactors have been discovered before, I believe in Nevada. It would only make sense that when the earth was forming, the heavier elements would migrate towards the core. Supposedly the reason our magnetic field changes every several thousand years is that the reactor poisons itself with byproducts and nearly stops... over time, these byproducts migrate outwards because they are lighter than the uranium, and the reactor starts up again with a magnetic field oriented differently from the one before it.

Here [nuclearplanet.com] is a site with a ton of info on it. Interesting stuff, but it makes more sense to me than an iron core simply because of the whole mass/gravity issue.

Re:who says it's molten iron (4, Interesting)

Undefined Parameter (726857) | more than 9 years ago | (#10749865)

I just so happen to be taking a Geology course, this semester. As I understand it, while Geologists are rather certain that radioactive materials provide the majority of the Earth's internal heat, they are equally certain that the core consists mostly of iron. The "liquid" outer sphere of iron produces the magnetic field through its motion.

As for the study itself: Wouldn't the Earth's own magnetic field interfere with the experiment, somehow? I saw nothing about this in the article, but I'm assuming that the Earth's magnetic field would either fail to significantly effect the results or the scientists are countering for it somehow, either in the experiment itself or in their calculations.

At any rate, I wish them the best of luck.

~UP

Re:who says it's molten iron (4, Informative)

CheshireCatCO (185193) | more than 9 years ago | (#10750259)

Radioactive materials aren't the same as a nuclear reactor. Unstable elements (like uraniam) or isotopes will break down regardless. A reactor has nearby radioative atoms triggering fission in their neighbors. For this, you need a fairly high density of radioative elements in close proximity. That's why they have to purify uranium ore, for example, to make fuel rods. (And further purify the isotopes to make weapons-grade uranium.)

The interiorof the Earth is almost certainly not a reactor. That theory has a lot of holes (we've argued this before on Slashdot, I know). The Earth's interior is more like an RTG on a spacecraft: you let the atoms decay at their own pace and use the heat rather than trigger a chain-reaction.

Re:who says it's molten iron (1)

lakiolen (785856) | more than 9 years ago | (#10752990)

I would assume that the scientists built a Farady Cage [wikipedia.org] around the device. All they really need to do is connect the six walls with metal, doesn't even have to be surrounded by solid metal.

Re:who says it's molten iron (2, Informative)

hplasm (576983) | more than 9 years ago | (#10753689)

Unfortunately, Faraday cages only shield out the electrical component of EM waves. To protect a volume from magnetic effects requires a high permittivity material, such as mumetal, which diverts the field through itself, and around the area to be protected.

Re:who says it's molten iron (4, Insightful)

CheshireCatCO (185193) | more than 9 years ago | (#10750391)

That theory is treated with serious skepticism for a reason. (Well, lots of reasons, really.) I can recall having this discussion here before and I forget the details of the theory, but I recall that the author showed an accute lack of understanding of planetary science among other things. (Jupiter is unlikely to have much more of a given metal than the Earth, oddly enough. The core is only at most about 10 Earth masses, and that's mostly ices. Also, the reactor theory doesn't explain field reversals or why the Sun has a field while dynamo theory explains both fairly naturally. Mind you, no one pretends to understand the details of theory since it's wickedly non-linear, but the basics of the theory seem to be fairly solid.)

Just in your post, I can say that it's unlikely that the field would stop because of build-up of wastes. For one thing, the wastes would either build up or they'd continually be lost. If they *did* build up, they'd slow the reactor down which would cool the system, leading to more sluggish convection and less mobile atoms. That would tend to freeze the wastes in place, not remove them.

Re:who says it's molten iron (5, Insightful)

Christopher Thomas (11717) | more than 9 years ago | (#10751761)

That theory is treated with serious skepticism for a reason. (Well, lots of reasons, really.) I can recall having this discussion here before and I forget the details of the theory, but I recall that the author showed an accute lack of understanding of planetary science among other things. (Jupiter is unlikely to have much more of a given metal than the Earth, oddly enough. The core is only at most about 10 Earth masses, and that's mostly ices. Also, the reactor theory doesn't explain field reversals or why the Sun has a field while dynamo theory explains both fairly naturally.

Actually, while the original poster's linked model is indeed bunk, it turns out that many of these objections aren't entirely accurate.

For one, the model doesn't dispute that the field arises from a dynamo. All it disputes is the nature of the heat source driving it (near-critical ball of uranium vs. a mixture of radioactives in far subcritical spontaneous decay mode). The mechanism for setting up the field is the same.

For another, if the model's tenets are accepted, field reversals aren't mysterious. The dynamo is shut down and restarted; there's no reason for it to restart with the same field orientation as before. All of the core material is far past the Curie point for holding a residual field, so I'd expect the restarted orientation to be random (constrained only by how the earth's rotation axis affects dynamo flow patterns).

What I find dubious about the model are the claims that a) lithophyllic elements like uranium would be concentrated in the core material, and b) material would diffuse preferentially towards the core strongly enough to result in fractioning, as opposed to just slightly increased concentrations. kT is big, and gravitational potential energy change with location is small down there, so I'd expect material to diffuse anywhere it pleased.

As far as Jupiter is concerned, I can't find references that say that the "icy" chemicals are in the core. As jupiter is expected to be molten throughout (as far as I can find), I'd expect them to diffuse out. Most sources say that carbon and nitrogen are mostly bound as methane and ammonia above the layers of liquid hydrogen. Some of the oxygen is bound as water in the atmosphere, and some of it as silicates in the "rocky" part of the core (which is presumably fractioned into silicates on top of a [molten] iron inner core, as in Earth).

Moot point re. the original article, of course, as you are definitely correct about the rocky core's mass.

Just in your post, I can say that it's unlikely that the field would stop because of build-up of wastes. For one thing, the wastes would either build up or they'd continually be lost. If they *did* build up, they'd slow the reactor down which would cool the system, leading to more sluggish convection and less mobile atoms. That would tend to freeze the wastes in place, not remove them.

My understanding was that the model proposed that they built up, shut down the core, froze in place, kept the core shut down until they decayed enough for the core to be near-critical again, and then dispersed as the hotter core allowed for faster diffusion away from the reactor area. Still pretty dubious, but I'd want to see a fairly detailed model of temperature, reaction rate, and mobility changes before writing that aspect off as outright impossible.

Re:who says it's molten iron (4, Insightful)

CheshireCatCO (185193) | more than 9 years ago | (#10752003)

Yeah, I considered that the restarted dynamo would be randomly oriented. That was actually the objection, although I didn't want to go on about it in the original post. You'd expect, in reactor case, to see the new field aligned the same way as before the (dipole!) fieldless period as often as anti-aligned. You don't see that, however. It actually reverses. That requires explanation in the model and the reactor doesn't manage that. A simple, continuous dynamo does it well. (You can get a dynamo with feedback to do this, never mind one as complex as Earth's. And besides, the Sun does it. And we know that the Sun's energy source doesn't shut off every 11 years ;-)

I'd like to see your sources on the core of Jupiter. I can cite a lot of sources to back up my statement, if you like. "The New Solar System" is an easily accessable book that covers the topic adequately. If you want something more detailed, "Protostars and Planets IV" has a nice discussion of this. I'd bet that the new Jupiter book from Cambridge University Press covers it, but my copy hasn't arrived yet.

If you're not finding references that say that the core is mainly ice, I'm curious where you're looking. (No, really: I'm curious.)

That said, no, there probably ices there if there is, in fact, a core. (We don't know for certain that there is as the data are sketchy. Oddly, it's easier to tell at the other giant planets.) Under the kinds of pressures at the center of Jupiter, rock and ice would be slushy, we think. We really don't understand the physics all that well for those pressures and temperatures, alas. (Which are, obviously, difficult to reproduce and to model since we have no good equations of state.)

Even if there aren't any ices, you're right that it's a moot point: there's not that much uranium in the planet unless our cosmochemistry is seriously wacked. (That is to say, unless there's a lot MORE uranium in Jupiter than in the Earth and in the galaxy at large. Which then requires an explanation as to where it all came from and how it got enriched in the giant planets.)

What's worse is that you need a lot more uranium than Earth has to generate your heat that way. Jupiter puts significantly more heat that it takes in from the Sun. (Earth takes in about 1360 W/m^2 and adds an additional 0.01 W/m^2 to the outgoing flux due to internal heat. Jupiter's internal heat is of order the same as what it takes in from the Sun. The latter being about 1/30 of what the Earth recieves.)

And you can't restart the reactor by letting the uranium daughter istopes decay. What do you think that they decay into? Lead, mainly. If thorium stops the reactions, I'm pretty sure that lead will, too.

If you want other objects, I gots 'em. Like the fact that you need a LOT of uranium to make this work. (Again, where is it coming from?) And that the primorial Earth would have been wickedly active. (Take the heat for formation, heat of differentiation, and add in not the radioactive decay buy a nuclear generator with a LOT more fuel and therefore a much more vigorous reactor. Basically, what the reactor model does is speed the burn rate. Which means, since we know the present heating rate of the Earth pretty well, you have to make it a lot hotter in the past with the reactor model than with pure decay. One would need to look at the model to see how hot, but I wouldn't be surprised, say, 3 billion years ago there would be too much heating to leave solid rock lying around.

You raised another of mine, how the uranium headed downward rather than sticking around with the silicates.

Re:who says it's molten iron (3, Interesting)

Christopher Thomas (11717) | more than 9 years ago | (#10754602)

I'd like to see your sources on the core of Jupiter. I can cite a lot of sources to back up my statement, if you like. "The New Solar System" is an easily accessable book that covers the topic adequately. If you want something more detailed, "Protostars and Planets IV" has a nice discussion of this. I'd bet that the new Jupiter book from Cambridge University Press covers it, but my copy hasn't arrived yet.

If you're not finding references that say that the core is mainly ice, I'm curious where you're looking. (No, really: I'm curious.)


About half an hour of looking for all of the web sources I could find (starting with Nasa, then moving to wikipedia and then exhaustive Googling). I figured that if that if there was a new or at least more detailed model that asserted that there were definitely light elements in the core, that at least one page on Jupiter's structure would mention it. Everything I could find said rocky core, then metallic hydrogen, then supercritical fluid hydrogen, then gaseous hydrogen mixed with small amounts of icy material and trace amounts of things like phosphine and hydrogen sulphide.

Any of the books I have lying around that talk about gas giant structure are old enough that they're still speculating about whether a rocky core exists at all, so they weren't much help.

I'm not disputing your sources, as you appear to have ones that are both more recent and more detailed than what I could dig up. Crawling through an astronomy publication archive would have taken me longer than half an hour :).

What's worse is that you need a lot more uranium than Earth has to generate your heat that way.

I realize that. My older sources on Jupiter mainly say that its heat source is from things like latent heat of fusion as materials continue to fraction out. Is this still thought to be the case?

While I'm at it, is heat of crystallization still thought to be making any significant contribution to Earth's heating? I recall that that was the competing model for Earth's heat generation before radioactive decay became widely accepted.

And you can't restart the reactor by letting the uranium daughter istopes decay. What do you think that they decay into? Lead, mainly. If thorium stops the reactions, I'm pretty sure that lead will, too.

If the core is conjectured to be a ball of mostly-pure uranium, you actually get a fast-neutron reactor type of process, which means most of your material is fissioned instead of decaying by alpha emission. This gives you all kinds of junk lighter than lead, instead of the slow decay chain you'd find in a subcritical radiothermal source.

Even a slow-neutron reactor should breed U238 and thorium into things that will fission. The whole point of a reactor is to speed up the rate of decay by either triggering it directly (as with fissile materials in a slow-neutron reactor or any material in a fast-neutron reactor) or by transmuting materials into ones that can be induced to decay rapidly (breeder reactors of all types). Mostly the end result is fission, again giving light daughter products.

Basically, what the reactor model does is speed the burn rate. Which means, since we know the present heating rate of the Earth pretty well, you have to make it a lot hotter in the past with the reactor model than with pure decay.

Quite a valid objection.

Re:who says it's molten iron (2, Interesting)

CheshireCatCO (185193) | more than 9 years ago | (#10754762)

Any of the books I have lying around that talk about gas giant structure are old enough that they're still speculating about whether a rocky core exists at all, so they weren't much help.

Actually, they're not that old necessarily. We still don't know if there's a core. The problem is that we don't have a good equation of state for materials at those pressures and temperatures and that the data from the Voyager flybys and Galileo orbits isn't that strong a constraint. (You're forced to use minor deflections in the trajectories to determine the deep interior structure. But that structure is, of course, shielded by many Earth-masses of overlying hydrogen and helium.)

It's easier to tell what's going on at the other planets, being lighter, since the temperatures and pressures are lower and there is less material over the core. (Also, Saturn's rings provide an interesting constraint, as I recall.)

My older sources on Jupiter mainly say that its heat source is from things like latent heat of fusion as materials continue to fraction out. Is this still thought to be the case?

I don't think I've ever seen anyone speculate about heat of fusion. (For anyone who doesn't know, this isn't nuclear fusion, it's the latent heat released when your go from liquid to solid phase. It's probably unfortunate that the chemists use the word "fusion" here.) Differentiation has been considered, but I don't think it's held in favor. The planet has probably had ample time for most kinds of differentiation to occur. (Saturn still has some differentiation occuring, we think. But in this case, it's helium rain in the atmosphere. But the conditions only appear to be right for this at Saturn and nowhere else.) However, it does seem that Jupiter could still be contracting, which also releases heat.

Even using a fast-neutron raction, I'd wager (feel free to fill in the nuclear physics here, though) that if the daughter isotopes moderate the reaction enough to stop it, then their daughter products probably will as well. Lighter elements aren't necessarily incapable of this, after all. (Carbon is a good moderator, as I recall.)

Re:who says it's molten iron (2, Interesting)

Christopher Thomas (11717) | more than 9 years ago | (#10755124)

We still don't know if there's a core. The problem is that we don't have a good equation of state for materials at those pressures and temperatures and that the data from the Voyager flybys and Galileo orbits isn't that strong a constraint. (You're forced to use minor deflections in the trajectories to determine the deep interior structure. But that structure is, of course, shielded by many Earth-masses of overlying hydrogen and helium.)

Out of curiosity, did anyone manage to get seismic data by looking at how Jupiter's envelope moved after Shoemaker-Levy 9's fragments hit?

Even using a fast-neutron raction, I'd wager (feel free to fill in the nuclear physics here, though) that if the daughter isotopes moderate the reaction enough to stop it, then their daughter products probably will as well Lighter elements aren't necessarily incapable of this, after all. (Carbon is a good moderator, as I recall.)

Actually, moderation (thermalizing of neutrons by a light material that scatters neutrons more readily than it absorbs them) could even speed it up. It's absorption that's the problem. There isn't a strong relation between the absorption characteristics of the initial daughter products and what they alpha or beta decay to. I'd either have to crunch through an ungodly-huge number of possible decay chains, or find a nuclear physicist who has.

I'm pretty sure this question has been answered at some point, though, as you get very similar material coming out of conventional fast neutron reactors in the form of spent fuel.

Re:who says it's molten iron (2, Interesting)

CheshireCatCO (185193) | more than 9 years ago | (#10755674)

Out of curiosity, did anyone manage to get seismic data by looking at how Jupiter's envelope moved after Shoemaker-Levy 9's fragments hit?

Kind of. I think some groups looked at it, but they were only looking for atmosphere-level diagnostics. (I think the farthest down they thought they might be able to sense was the metallic hydrogen transition.) I don't recall any results from that, actually, so I'm not sure if they really panned out. Certainly I've heard nothing that says we learned about the core.

I'm pretty sure this question has been answered at some point, though, as you get very similar material coming out of conventional fast neutron reactors in the form of spent fuel.

Ooo, good point. Unless they do something to the spent fuel that I don't know about, I've never heard of a worry about the spent fuel restarting itself. Which is probably saying something for our purposes.

Re:who says it's molten iron (2, Interesting)

Christopher Thomas (11717) | more than 9 years ago | (#10758466)

I'm pretty sure this question has been answered at some point, though, as you get very similar material coming out of conventional fast neutron reactors in the form of spent fuel.

Ooo, good point. Unless they do something to the spent fuel that I don't know about, I've never heard of a worry about the spent fuel restarting itself.

The spent fuel is dissolved in glass (vitrified), which is then encapsulated as glass pellets sheathed in carbon composites for structural strength, to limit possible accidents during handling. These are put in extremely strong barrels, and the plan is to put these in deep mine shafts in non-porus rock and plug the holes with clay.

What's actually done now is storing them as fuel bundles in pools of water, as an interim measure until we can agree on whose mine shaft the waste gets dumped into, but that's another discussion.

Upshot is that the short-term storage doesn't have to worry about the fuel reactivating, and the long-term storage doesn't have enough in one place, and has enough other crud around it, to not have to worry about reactivation.

A construct amounting to a several-mile sphere of radioactive waste, on the other hand, probably _would_ have to worry about it, though a more plausible scenario is a steady-state burn where the rate of outward diffusion of lighter wastes matches their rate of production.

ObDisclaimer about having to run lots of numbers before being able to say what would actually happen in a situation like this.

Re:who says it's molten iron (5, Informative)

krymsin01 (700838) | more than 9 years ago | (#10752363)

The natural reactor you speak of is Oklo, you can find more information about it here [curtin.edu.au] . You're wrong about the location, unless you are speaking of some other natural nuclear reactor that hasn't been brought to acedemic attention. From the site:
Location: Natural fossil reactors have (so far) only been found in the country of GABON in equatorial Africa. All but one of the reactors are located at a place known as the OKLO uranium deposit located in the south eastern corner of the country. Another fossil reactor has also been discovered in Gabon at another U deposit at Bangombe, some 35 km south east of the OKLO mine. For more information about Gabon;

Measuring the Earth's core? (0)

Anonymous Coward | more than 9 years ago | (#10749659)

Whatever the researchers do, I suggest they don't:

i) Stop the Earth's core rotating while conducting experiments on it

ii) Try and start it again using a series of large nuclear detonations

iii) Make a ridiculously shyte film [imdb.com] about it

I don't see how measuring the effects on a 10-foot diameter sphere (filled with Na) can be equivalent to the effects on the central core of a 6400km-radius ball of rock (filled with many different elements). If they want to figure out more about the Earth's magnetic field, I suggest they take measurements, etc... on the EARTH.

Re:Measuring the Earth's core? (4, Interesting)

Christopher Thomas (11717) | more than 9 years ago | (#10751440)

I don't see how measuring the effects on a 10-foot diameter sphere (filled with Na) can be equivalent to the effects on the central core of a 6400km-radius ball of rock (filled with many different elements). If they want to figure out more about the Earth's magnetic field, I suggest they take measurements, etc... on the EARTH.

The nice thing about building our own sphere of molten metal is that we a) know its structure and composition in detail, b) can put sensors inside, and c) can alter parameters (temperature gradient, rate of spin) and see what happens. None of these are practical for Earth, though we do have a reasonably good idea of what its composition and large-scale internal structure are.

The patterns of motion they're setting up are common to a very wide range of fluid systems - you don't need something as big as Earth to generate them. It's very hard to measure fluid flows and magnetic fields deep within the earth (all that's easy is density change boundaries), and the Earth's field isn't likely to flip within our lifetimes (or the next several centuries, minimum, even if the wierdness we're seeing _does_ represent the start of a flip). A small-scale mock-up run in the same turbulence modes that the core has will flip many times during the course of observation, and tell us a _lot_ about how the flipping occurs.

In short, we'll learn a lot more about the geomagnetic field from this experiment than we would from more studies of the Earth itself.

you sure they're scientists ? (2, Funny)

da5idnetlimit.com (410908) | more than 9 years ago | (#10749728)

The picture made me think of 3 evil magical ones in Charmed preparing a really noxious potion ...

Look closely, one of them is even clearly hunched 8)

Blinded me with science (1)

YetAnotherName (168064) | more than 9 years ago | (#10749729)

"Researchers from the University of Maryland's nonlinear dynamics and chaos research group are seeking to solve a major scientific mystery: How is the Earth's magnetic field formed and what causes changes in the field?"

But it would take a scientist to explain--- eh? Oh, nevermind!

A question (0)

Anonymous Coward | more than 9 years ago | (#10749869)

Since the Earth orbits inside the Sun's magnetic field, can induced currents from this cause a back EMF in the Earth? There are large ground currents after all caused by the Sun.

Re:A question (2, Informative)

CheshireCatCO (185193) | more than 9 years ago | (#10750443)

Actually, in a direct sense, the ground currents are caused by Earth's field. It's when the field snaps back from CME*-induced distortions that we get those nasty currents. The Sun is driving it, but it's via a CME, which then messes with Earth's field, which then causes the currents.

That said, if Earth's magnetic field didn't exclude the Sun's, would there be an EMF? Yeah, I should think so. But the Sun's field is mainly in the plane of Earth's orbit and varies comparatively slowly. (Over hours or more, rather than, say, seconds.) So I wouldn't expect a lot of induced EMF as per Faraday's law. (Caveat: This is from memory. I have the details about the solar wind and interplanetary magnetic field in my texts in my office, but I'm (happily) not there at the moment.)

* Coronal Mass Ejection

Potential of untold riches (3, Funny)

failedlogic (627314) | more than 9 years ago | (#10749983)

I can think of one way to get really rich of this idea.....

Sell air plane fuel? Install one of these puppies near an airport. Ideally a faily busy one like LAX or O'Hare. Turn on the machine. As it takes more fuel for the planes to take off .... profit!!!

Re:Potential of untold riches (2, Funny)

div_B (781086) | more than 9 years ago | (#10750118)

Sell air plane fuel? Install one of these puppies near an airport. Ideally a faily busy one like LAX or O'Hare. Turn on the machine. As it takes more fuel for the planes to take off .... profit!!!

Then cough up for the energy used to start and keep the thing running. Declare bankruptcy. Move onto street, drink from liquor bottle in brown paper bag.

Re:Potential of untold riches (2, Funny)

LiENUS (207736) | more than 9 years ago | (#10750233)

Shhhh... my liquor store is right next to airport, don't want you foiling my plan to get rich off of him now do we?

Cool! (2, Funny)

Black Parrot (19622) | more than 9 years ago | (#10750276)


If they can simulate iron with sodium, we should be able to figure out a way to simulate irony with sodiumy!

Re:Cool! (0)

Anonymous Coward | more than 9 years ago | (#10753307)

If they can simulate iron with sodium, we should be able to figure out a way to simulate irony with sodomy!

Take that.

Considering (0, Flamebait)

b-baggins (610215) | more than 9 years ago | (#10751360)

That the Earth's core is not molten sodium, nor is it made of stainless steel, this is a pretty poor experimental model, but, hey, I'll bet the grant money was pretty good.

Re:Considering (4, Informative)

Christopher Thomas (11717) | more than 9 years ago | (#10751791)

That the Earth's core is not molten sodium, nor is it made of stainless steel, this is a pretty poor experimental model, but, hey, I'll bet the grant money was pretty good.

Considering that magnetic field generation depends only on the pattern of fluid flow and the fact that the fluid is conducting, I'd say this is actually a pretty good experimental model. See my previous post about why it's really handy to have a dynamo you can change the parameters of.

Note to self.... (1)

MazTaim (1376) | more than 9 years ago | (#10751441)

...Don't accidentally tip the (imaginary) precariously perched buck-o-water into that thing.

You wouldn't have time to hear the extremly loud KABOOM.

"Earth's" magnetic field? (2, Insightful)

stutterbug (715367) | more than 9 years ago | (#10751546)

As I understand it, the universe has only one megnetic field and the Earth (and other masses) merely distorts that field. Same goes for gravity. Is this not true? I realize this doesn't change the sense of the article at all, but it always bothers me to hear people talk of the "Earth's" magnetic field like it is somehow unconnected to anything else.

Re:"Earth's" magnetic field? (4, Informative)

Christopher Thomas (11717) | more than 9 years ago | (#10751831)

As I understand it, the universe has only one megnetic field and the Earth (and other masses) merely distorts that field. Same goes for gravity. Is this not true? I realize this doesn't change the sense of the article at all, but it always bothers me to hear people talk of the "Earth's" magnetic field like it is somehow unconnected to anything else.

The answer to this is "sort of".

The short answer is, the Earth's magnetic field is best thought of as belonging to Earth, as opposed to being a disturbance in a larger universal field. ObCaveats about the interaction between the Earth's field and the Sun's field and the Milky Way's field giving important effects; all of these can still be considered fields local to the objects generating them.

The long answer is that the electromagnetic force can be thought of as charges disturbing a field of virtual photons that does indeed fill the universe. However, saying that there's a magnetic field pervading the universe doesn't really make sense, as the measured magnetic and electric field strengths without charges and currents disturbing the virtual photon field will be zero, and these disturbances for unchanging fields have a very limited range of effect (or rather, an unlimited range but a strength that drops off very fast with distance).

In summary, "Earth's magnetic field" is probably the best description.

look up (3, Interesting)

carambola5 (456983) | more than 9 years ago | (#10752464)

If they're in Northern USA or Canada, alls they gotta do is look up tonight. Killer auroras in the skies... at least in my neck of the woods.

Speaking of the earths magnetic field (2, Informative)

seann (307009) | more than 9 years ago | (#10752695)

Speaking of the earths magnetic field, tonite the Aurora Borealis [mtu.edu]
was spotted in Southern Ontario from about 6pm Eastern to 3:00AM Eastern.

What a treat.

More to it than the article states (2, Interesting)

Anna Merikin (529843) | more than 9 years ago | (#10753410)

In the article, it is reported that the earth's magnetic field has been measured to have decreased by ten per cent in 150 years; other articles (from BBC, f'rexample) announced other scientists using tree-sections, have determined the field's strength-loss began about three hundred years ago, and now totals about fifteen per cent decrease.

There also have been reports that the earth's magnetic field within the Ozone Hole has already reversed.

This information does not fit with the nuclear-generator theory, but fits better with the destruction of the ozone layer in the upper atmosphere.

As an FCC-licensed radio/TV engineer, I know that ozone is always produced with electrical current. The article quotes (I paraphrase) an "expert" who says motion, magnetism and electricity are a trinity: where two are found, the other will be too. He should have included ozone and made it a quadernity as this is also true of ozone.

During lighting strikes to earth, ozone first rises from the ground to the cloud, and only then is a conductive path to earth made, enabling the lighting strike.

Also, IF it is true, as contended by many scientists, that the ozone hole is related to the increase in ground ozone caused by human activity (electrical production and photochemical smog, largely) then it MIGHT be that there is only a finite amount of ozone that can be produced (or supported) by the earth's magnetic field, and humanity may fairly be seen as the cause.

But I doubt this is true, as the records in the trees show the magnetic field having begun its decrease three hundred years ago -- before Watt and the industrial revolution.

In any case, this is not an easy study as information is scanty and largely the reserve of specialists rather than the generalists who seem to be the only ones with a large enough world-view (weltenshauung, in German) to grasp the problem and explain it to us.

And I doubt strongly that the subjects of the article have any real klew as to what is happening -- not to say I do.

Re:More to it than the article states (0)

Anonymous Coward | more than 9 years ago | (#10753915)

When you say radio/TV engineer, what exactly do you mean? I only ask because some of your comments seem flawed to me and poorly articulated at that. I haven't heard of the atmospheric vs. ground level ozone theory before. Certainly the shift has been that way but to suggest that earth's magnetic fiels has a particular capacity to support ozone in particular seems counterintuitve to me. And any effect that even exists has to outweigh the ODS effects enough to not just register as noise. Which 'many' scientists are you referring to. Some of the most important research is done by people who are trying to answer hard questions as best they know how. Nothing wrong with not having a 'real klew' of what is going on before you get some meaningful results. That's why we do these things. I don't want to start a flame war so yes, I'm posting anonymously. My questions, however, are not meant to be rhetorical... if you can point me to some peer-reviewed research on this topic I would appreciate it.

Re:More to it than the article states (2, Interesting)

Anna Merikin (529843) | more than 9 years ago | (#10754813)

Since you asked (I don't usually reply to follow-ups) I am an FCC First-Class Radio and Television engineer. I started in 1969 and continued until 1982, when I began writing fulltime. I left the field because I was being asked to falsify data to the FCC.

I agree no one but me has suggested a relationship between ground-level ozone and upper-atmosphere ozone. But a fixed earth mag field would produce (was produced by?) a fixed amount of ozone. It is a reasonable possibility, I think, until disproven. Think about it: there is less and less upeer ozone and more and more lower.

Yes, the researchers are trying hard; I am not trying to insult them (or you) it's just no one seems to see the larger view that the earth is a living system and ozone is its breath (metaphor).

I got my news about the weakening magnetic field from the BBC natural science pages. However, a search of the site has produced nothing.

I sent a friend an email about this subject with a link to a BBC article; it's on a Knoppix partition right now, though, and I'm on my new SuSE installation, so it will be some hours till I MIGHT be able to get the link to the reversed field in the ozone hole off New Zealand.

Here, though, are some other links to support my thesis and informtation.

http://www-istp.gsfc.nasa.gov/Education/FAQs2.ht ml
http://www.theozonehole.com/magnetic.htm
http:/ /www.sciforums.com/showthread.php?t=11632

Re:More to it than the article states (3, Informative)

stevelinton (4044) | more than 9 years ago | (#10753982)

The ozone in the stratosphere is created by solar ultraviolet dissociateing oxygen
This produces free oxygen atoms which latch onto basically anything they can find. If what they find is an oxygen molecule then you have ozone. This happens wherever there is sunlight and oxygen and there is no electrical current involved.

Over the poles, during the winter, in the presence of chlorine (which is mainly there due to human activity) there is a chemical reaction which breaks down the ozone causing the holes.

None of this has anything to do with the Earth's magnetic field, which is generated far underground, or with surface ozone, which is mainly man-made.

Re:More to it than the article states (0, Troll)

Anna Merikin (529843) | more than 9 years ago | (#10754898)

Wow! I ususally don't reply to followups, but I HAVE to ask you some questions.

Are you certain there is no connection between ozone and the earth;s magnetic field?

Are you certain there is no connection between the loss of ozone in the upper atmosphere and the increase at ground level (due to human activity?)

And you are incorrect about the constituency of ozone: Ozone, according to my understanding, IS dissociated oxygen -- that is, an unbonded, single oxygen atom instead of a pair forming a molecule.

Ozone is O-sub-1 and oxygen is O-sub-2.

Re:More to it than the article states (1, Informative)

Anonymous Coward | more than 9 years ago | (#10754981)

Ozone is O3.

Re:More to it than the article states (1)

Anna Merikin (529843) | more than 9 years ago | (#10755096)

You are correct, I found out. o-sub-1 is a "free radical." You do not, however, seem certain of your other posits -- the ones I mentioned. Eh?

Re:More to it than the article states (2, Insightful)

stevelinton (4044) | more than 9 years ago | (#10755335)

I'm not unshakingly, go to my death protesting it, deep-rootedly certain of these points from my own personal knowledge and experience.

Indeed, if you get picky there is bound to be some connection between the various things we are talking about, but I do maintain that, from my wide reading over a long period, that the accepted view of the scientific community based on decades of observation and experiment is that any such connections are very tiny, and are swamped, for instance, by random variations due to atmospheric turbulence.

I would be fascinated to hear of any PEER-REVIEWED research showing, or even suggesting, that such connections explain more than, say, one part in a trillion of the observed ozone depletion and magnetic field variations.

Ozone is O3, as I think you subsequently realised. O1 is atomic oxygen.

Re:More to it than the article states (1)

cjameshuff (624879) | more than 9 years ago | (#10755697)

Ground ozone is generated by human activity, and is independent of the magnetic field. The ozone molecule itself is neutral and exists in extremely tiny concentrations, and can have no measurable effect on the magnetic field.

Stratospheric ozone is generated by solar UV light interacting with atmospheric oxygen. Neither is affected by or has an effect on the magnetic field. Stratospheric ozone will be very slightly increased by diffusion of ground ozone, but few ozone molecules will survive that trip...it's an unstable and reactive molecule. Still, this is the only way ground production will have any effect on stratospheric ozone

I guess you're not an electrical engineer of any sort. The trinity of magnetism, electricity, and motion is due to the fact that moving magnetic fields induce electrical currents, moving electrical charges induce magnetism, and electrical currents and magnetism together can produce motion. Ozone doesn't come into this anywhere. Ozone is not always produced with an electrical current, and it isn't affected by and doesn't cause electrical charges, magnetic fields, or motion.

(Actually, there may be a very slight attraction or repulsion to magnetic fields, depending on whether O3 is paramagnetic or diamagnetic. The effect is too weak to make a difference here, though.)

Your description of lightning is simply incorrect. Ozone is a result of the ionization caused by lighting, not a cause. Lightning generates ozone in the same way that solar UV does, by splitting O2 molecules into atomic oxygen which then combines with unsplit O2 molecules.

Re:More to it than the article states (1)

Idarubicin (579475) | more than 9 years ago | (#10756848)

Also, IF it is true, as contended by many scientists, that the ozone hole is related to the increase in ground ozone caused by human activity (electrical production and photochemical smog, largely) then it MIGHT be that there is only a finite amount of ozone that can be produced (or supported) by the earth's magnetic field, and humanity may fairly be seen as the cause.

There's actually remarkably little relationship between ground-level ozone and stratospheric ozone. Stratospheric ozone is the product of ultraviolet photolysis of oxygen. Regular oxygen (O2) is broken into two free oxygen radicals by ultraviolet light. Each may recombine with another O2 molecule to form O3--ozone. This reaction also works the other way--ozone can absorb UV, releasing O2 and an oxygen radical. Ozone is quite good at absorbing UV in this way, which is handy for those of us on the ground.

The depletion of stratospheric ozone is the result of long-lived manmade chlorine compounds--mostly CFCs (chlorofluorocarbons). Chlorine radicals result from the ultraviolet photolysis of CFCs. These radicals catalyze the breakdown of O3 into O2. Each chlorine atom can catalyze many such reactions over the course of years.

Meanwhile, ground-level ozone is the result of a photochemical reaction between volatile organic compounds (VOC) and nitrogen oxides (NOx, mostly NO2).

More important here is that neither one is significantly affected by the earth's magnetic field, nor is there a maximum atmospheric load of ozone that is maintained. (The ozone holes are recovering now that CFC use has ended, but ground-level ozone problems have not abated except where efforts have been made to reduce NOx and VOC emissions.)

During lighting strikes to earth, ozone first rises from the ground to the cloud, and only then is a conductive path to earth made, enabling the lighting strike.

I'm afraid that this just isn't accurate. Ozone is the product of a lightning strike, not the cause. It is produced when oxygen molecules are split by the passing current, and some recombine into O3. The conducting path to/from ground is actually made of ionized gas--not ozone--and is formed when the potential (voltage) difference between cloud and ground is large enough to strip electrons from gas molecules to form ions.

This is what's happening on a very small scale when you mention that ozone is 'always' produced by current. Tiny electric arcs through air ionize oxygen molecules, and allow them to react to form ozone. Consequently, you'll only get ozone around high voltage equipment (where there is corona discharge) or where circuits are being opened and closed. (You shouldn't smell ozone from a functioning incandescent lamp, but you might get a whiff when you flip the switch on and off--a little arc forms when the contacts are opened and closed.)

Re:More to it than the article states (1)

Anna Merikin (529843) | more than 9 years ago | (#10759479)

...you'll only get ozone around high voltage equipment (where there is corona discharge) or where circuits are being opened and closed.

All electric motors produce ozone. All wires that carry varying currents will produce ozone, as ozone is produced be electrical current (any moving magnetic field) in the presence of gaseous oxygen.

I've learned a lot of detail in this discussion, but nothing that daunts my pursuing the answer to my IF proposition, as you quoted above. To me, if the total amount of ozone in the earth's atmosphere (high or low) is more stable than any of the partial sources, that tends to indicate there is some other process going on.

In the same way that the total number of suicides and homicides (added together) make the US and other nations of the world nearly equal, although Hungary has many more suicides than average and the US has more homicides.

I guess the natural sciences are different than the "hard" sciences.

Cause and effect are not the only operatives in nature.

I wonder... (2, Interesting)

charlie763 (529636) | more than 9 years ago | (#10753708)

I wonder if there is any correlation between the reversal of the poles and evolution. An increased exposure to cosmic radiation may increase the normal rate of mutation of a species. It would be interesting to look at the fossil record and compare the pole reversals with the arrival of new species or, perhaps, even the end of a species.

Re:I wonder... (1)

Elder Entropist (788485) | more than 9 years ago | (#10760242)

There would be a rather large delay between a cosmic-radiation triggered mutation and the point where it would become common enough in a species to leave its mark in the fossil record. Probably a significant fraction of the average time between field pole reversals (which is about 200,000 years). That would make finding a pattern near impossible.

Re:I wonder... (1)

gardyloo (512791) | more than 9 years ago | (#10771144)

This is true. However, there may be much faster mechanisms for *die*-offs than radiation-induced mutations, such as if a species or superset of species specifically rely on Earth's magnetic field for migration, etc. If the field suddenly reduces in strenth or changes direction, the migration paths of these animals may be radically altered, with the result that they may migrate to low- (or higher-) food areas, into areas with fewer predators, into areas where parasites are able to take advantage of them, etc.

Cool party chat-up line... (3, Funny)

jpop32 (596022) | more than 9 years ago | (#10753723)

You see, I'm with the nonlinear dynamics and chaos research group.

another possible experiment (1)

Muhammar (659468) | more than 9 years ago | (#10761551)

spinning 14 tons of molten Na is impressive - but sodium metal is not not very paramagnetic - the atoms have only one unpaired electron per atom, unlike iron. What's wrong with doing experiment with molten iron? I wonder if somebody tried to bring a magnetometer into a steel mill - to detect the changes in magnetic fields generated by hundreds tons of molten iron flowing around. While this may not be as controlable experiment as playing with the sodium sphere I think it is more relevant to the actual conditions in earth core.

Re:another possible experiment (1)

myukew (823565) | more than 9 years ago | (#10763981)

It's just much easier to keep stuff molten that melts at 97,72 C than playing with iron which melts at 1535 C...

Re:another possible experiment (1)

Muhammar (659468) | more than 9 years ago | (#10764061)

sure, but in steel mills they have lots of it - and molten already (more than you ever wanted) and they pour it, so the stuff flows and you can make it go where you want it, etc.

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