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Ocean Currents Proposed As Cause of Magnetic Field
Posted by
kdawson
on Sun Jun 14, 2009 05:03 PM
from the round-and-round-and-round-in-the-circle-game dept.
from the round-and-round-and-round-in-the-circle-game dept.
pjt33 notes a recently published paper proposing that ocean currents could account for Earth's magnetic field. The wrteup appears on the Institute of Physics site; the IOP is co-owner, with the German Physical Society, of the open-access journal in which the paper appears. This reader adds, "The currently predominant theory is that the cause of Earth's magnetic field is molten iron flowing in the outer core. There is at present no direct evidence for either theory." "Professor Gregory Ryskin from the School of Engineering and Applied Science at Northwestern University in Illinois, US, has defied the long-standing convention by applying equations from magnetohydrodynamics to our oceans' salt water (which conducts electricity) and found that the long-term changes (the secular variation) in the Earth's main magnetic field are possibly induced by our oceans' circulation."
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Could be... (Score:5, Interesting)
Re: (Score:3, Funny)
So we're talking about _electric_ ocean currents? How is right hand rule newsworthy?
Re:Could be... (Score:5, Funny)
Um, this is /. so I'm not sure "right-hand rule" always means what you think it does here. :-) I'm sure a lively debate could ensue on "science geek" vs. "lonely geek".
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Re:Could be... (Score:4, Funny)
Lonely geek has moved on to the Fleshlight rule.
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Especially when we keep crashing planes into them (Score:4, Funny)
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Polarity switch (Score:4, Funny)
Re:Polarity switch (Score:4, Informative)
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Re:Polarity switch (Score:4, Informative)
No, the poles already reversed once in theory http://en.wikipedia.org/wiki/Earth's_magnetic_field [wikipedia.org], and are likely to keep reversing, though none of us will be around to find out.
If you do some non-wiki research, you will find out that Earth's magnetic field has reversed many times over the eons. We're overdue now by several thousand years. This Global Warming may be just another indicator that such a change is imminent.
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Re:Polarity switch (Score:5, Informative)
Hundreds if not thousands of direction changes are documented, back into the Triassic at least and possibly into the Late Palaeozoic. There are sufficient that, in more recent times (Cretaceous onwards) the reversal record has been used as a tool for correlation. (Such work may go back further into the geological record ; I've certainly seen it used in Cretaceous mudrock sequences as a petrophysical indicator that can be measured faster and with less skilful operators than other techniques like palynology.)
For certain values of "overdue" ; the distribution of durations between reversal events seems to be essentially random, and since we're over the average duration between reversals, then one could meaningfully "expect" a reversal sooner rather than later. But once you start looking at the statistics, you have to accept that, if the model is accurate, then the probability of a reversal in the next thousand years (say), is the same as the probability of a reversal in the first thousand years after the last reversal. It's the same logic as tossing coins - if you get ten heads in a row, the probability of your next toss being a head is still 1/2, even if the probability of getting 11 heads in a row is 1/2048. Random variables - love 'em or hate 'em, but you can't predict 'em.
That said, outside the statistical description of the record, the physical models suggest that some events seen at the moment (decreasing field strength ; regional anomalies) may be precursors to a reversal.
Has someone been claiming global warming to be related to magnetic field strength? Whooo, can I get a smoke of that? Sounds like good gear.
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Re:Polarity switch (Score:5, Interesting)
Well magnetic north has moved over 1100 kilometers in the past 100 years, and the motion is accelerating. It is currently moving about 40km per year.
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Re:Polarity switch (Score:4, Funny)
I"m trying hard to make a joke about writing down when it happened and referring to that as reverse pole-ish notation, but... I think I'll let it go.
(I should probably post this anonymously, but hey - I stand by my bad puns!)
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Re: (Score:3, Interesting)
It'll be the magnetic North pole... North just wont be where you think it is.
I may be wrong, Im not an astrologer (Score:5, Interesting)
Re:I may be wrong, Im not an astrologer (Score:5, Funny)
I can pretty much guarantee that astrologers would have no idea what you're talking about :)
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Re: (Score:3, Insightful)
Just as valid as a hypothesis perhaps, but not as a theory.
A theory requires some evidence and logical reasoning.
While scientists don't "truly know" in that their knowledge is incomplete; they do have a large body of clues, expirmentation and evidence to help them build a more complete knowledge.
You on the other hand simply have given your hypothesis without bothering to look at any clues further than your own skull, or at least you haven't bothered to publish or explain your clues and reasoning to others i
Re: (Score:3, Insightful)
You are certainly right about that. If there is no God then you are no more valuable than a cock roach, because all life climbed out of the primordial ooze. Only a personal God can give personal value.
Bullshit.
Value is given by evaluators. In my case, the evaluators are me, and the people who know me well enough to have a valid opinion of me. I don't need a fancy invisible god to see that human beings are more valuable to human beings than cockroaches.
God built the world for man... (Score:5, Interesting)
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Re:I may be wrong, Im not an astrologer (Score:5, Interesting)
In much the same way, the molten iron theory is more around currents (fluid currents) causing electrical currents in the core. These electrical currents then cause the magnetism.
Nobody is saying that the iron itself is magnetic (because then it would be magnetite and not iron anyway).
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Re: (Score:3, Informative)
I don't know if you are joking, but we certainly knew Mars gravity to within some tiny fraction of a percent. The period and distance of it's orbiting moons can be used to figure it out pretty accurately. You may be thinking of the spaceship that was lost because of metric/english unit confusion?
Re:I may be wrong, Im not an astrologer (Score:5, Informative)
That's correct. According to their theory, moons like Europa should have a rather strong magnetosphere.
Europa is believed to have a warm, salty ocean under the ice crust. And yet, it shows only slight inducted magnetic field from Jupiter. Contrast that with Ganymede, the only moon with its own magnetosphere and a liquid iron core. Satellite photos dont show very much (or any) water on its surface.
Hmm.
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Re:I may be wrong, Im not an astrologer (Score:5, Interesting)
The idea of the ocean under Europa is that of an educated guess based upon tidal forces between Jupiter, and the fact that surface composition of Europa is frozen water. Flyovers have taken spectral pictures indicating that fact. They also have taken magnetic force readings and determined that any form of magnetosphere was Jupiters creating.
Ganymede has a liquid iron core, from which I dont understand how they figured that out. However, many sources say so, including NASA. And it's noted by the natural color of 'streaking on the ice' that the moon does have its own magnetosphere. And it was measured by Flyovers. It's strange that it still has a liquid iron core, al most over planets have frozen. The assumption is that Jupiter tidal forces have insulated it.
We dont need to understand why and how a liquid iron core creates a magnetosphere. We CAN measure more data points to see if our hypothesis matches with known facts. And this water-creates-magnetosphere seems debunked.
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Re:I may be wrong, Im not an astrologer (Score:5, Interesting)
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Re:I may be wrong, Im not an astrologer (Score:5, Funny)
I may be wrong, Im not an astrologer...
If you ask an astrologer a question about the ocean, they'll probably want to know if you're a pisces.
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Re: (Score:3, Informative)
Aren't there planets that do have magnetic fields, but don't have oceans?
IIRC Venus has a weak magnetic field and does not have an ocean.
Re:I may be wrong, Im not an astrologer (Score:4, Informative)
As does mars. It has a weak field, but it also is suspected of having a much smaller molten core.
Europa and Ganymede have molten cores due to gravitational churning.
So far, molten cores correlate well with magnetic field strength. Oceans, when present, tend to be on those bodies having molten cores, but their absense does not entirely preclude a magnetic field.
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Re:I may be wrong, Im not an astrologer (Score:5, Informative)
Mercury has a magnetic field, which quite surprised planetary scientists when it was first discovered by MAriner 10, as the prevailing theory at the time was that Mercury's small size would have led to its core solidifying by now and stopping the dynamo that generated the field.
There's obviously a lot we don't know about planetary magentic fields, and I wouldn't want to judge the entire theory just by something I read on Slashdot, but I find it hard to understand how oceanic currents could account for Earth's magnetic field but not for Mercury's.
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Uh, right. (Score:4, Insightful)
Re:Uh, right. (Score:5, Insightful)
Because the other theory hasn't been tested, and might be wrong.
Ignoring possible alternative theories, especially for unknowns, is no different from adhering to dogma on pure faith alone, and damages scientific inquiry.
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Re:Uh, right. (Score:5, Informative)
Because the other theory hasn't been tested, and might be wrong.
The point is that the chances that each celestial body's magnetic field is due to a unique generator are... Well, let's say that that is not what we typical see in scientific history. Similar effects are generated by similar causes, especially at planetary scales.
(I see that I've been misled by the summary, as usual. Yes, I should RTFA. But the editors should fucking WTFS in a manner resembling responsible journalism. Could currents in the oceans modulate the magnetic field? Worth investigation, I think.)
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Joke or not,,, I was trying to think of other mean (Score:3, Insightful)
the general argument here is that other planets lacking oceans also have magnetic fields-- so that ain't right..
so I'm thinking, what do all solar bodies have in common that could be another means to that end
solar wind? the flow of all the radiation from the sun, wrapping around the planet, and blowing on? happens to all objects in the system??
Because someone has to respond to trolls (Score:5, Insightful)
Funny words from someone who used rather massive ad hominem by trying to label people disagreeing with him as zealots.
Consensus is used as an argument because not all of us can be climate scientists. There is large consensus among them that global warming is happening and caused by men. Not all agree to that. Name any theory and you have people who disagree with it. Hell, there is even a flat earth society. But big majority of the expert who know about the subject and have studied it their whole lives believe so.
Most of the people who argue about it in the internet aren't climate scientists. They've read a few stories which have quoted some climate scientists who disagree with the mainstream and then begin arguing. To them I can always answer "Hey, I am not an expert in the field. And honestly, most likely you aren't either. When your arguments are good enough that they manage to sway opinions of the expert, then you can come back to me. Otherwise I have all the reason to assume that there is some flaw in them."
All of us who aren't experts in every field of science have to do that about some subjects. Trust the scientific method and through that, the experts who employ it.
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Re: Uh, right. (Score:4, Funny)
Occam's Razor was the razor to own. Then the other guy came out with a three-blade razor. Were we scared? Hell, no. Because we hit back with a little thing called the Occam's Razor Turbo. That's three blades and an aloe strip. For moisture. But you know what happened next? Shut up, I'm telling you what happenedâ"the bastards went to four blades. Now we're standing around with our cocks in our hands, selling three blades and a strip. Moisture or no, suddenly we're the chumps. Well, fuck it. We're going to five blades.
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Re: (Score:3, Funny)
I like it, occam's razor turbo:
"Of several acceptable explanations for a phenomenon, the simplest is preferable even when there's good evidence to suggest a more complex explanation and no evidence to suggest the simplest. Furthermore, that evidence is automatically invalidated by the first guy to yell out 'Occam's razor,' especially when the guy makes no attempt to explain himself."
Re:Uh, right. (Score:4, Insightful)
According to the article, there is no direct evidence for the metal currents which allegedly induce the magnetic field. They are inferred on basis of the existence of the field. Venus doesn't have a magnetic field--so we decide it doesn't have a molten iron core. The only reason the 'present theory' is so simple and explanatory is because we arbitrarily decide on the planets' internals are such that our theory is always guaranteed to fit.
Your generalization is also a bit off, as plenty (probably most) of the large celestial objects have magnetic fields but lack iron cores. The sun certainly lack an iron core. We assume Jupiter's magnetic field is supplied by metallic hydrogen, but it could just as easily support it by electrical currents.
The magnetic fields are actually quite complex and Occam's razor doesn't mean assuming everything is a perfect sphere, as the classic joke goes. If the oceanic theory successfully explains secular variation then Occam's razor may be more likely to back the ocean theory than the dynamo theory.
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New possibilities in terraforming? (Score:3, Insightful)
Summary wrong: Oceans only small variations (Score:5, Informative)
The Slashdot summary is totally wrong.
From the abstract of the paper: "I propose a different mechanism of secular variation: ocean water [...] as it flows through the Earth's main field may [...] manifest itself globally as secular variation."
Meaning: There is a major magnetic field that comes from the molten core. However, certain variations that are as yet unexplained may not result from core phenomena, but from the ocean currents.
I find this much more believable than the swill in the slashdot summary.
Re: (Score:3, Informative)
Its not totally wrong.
FTA: "While Ryskinâ(TM)s research looks only at long-term changes in the Earthâ(TM)s magnetic field, he points out that, âoeIf secular variation is caused by the ocean flow, the entire concept of the dynamo operating in the Earthâ(TM)s core is called into question: there exists no other evidence of hydrodynamic flow in the core.â"
He does go so far to say that there is no examinable proof of a liquid core and that we could have been wrong all these years.
It does
Re:Summary wrong: Oceans only small variations (Score:5, Insightful)
He says,
If secular variation is caused by the ocean flow, the entire concept of the dynamo operating in the Earthâ(TM)s core is called into question: there exists no other evidence of hydrodynamic flow in the core.
--From the article
Er, dude, no. We are pretty certain that the outer core is a liquid from seismic wave data. "So what?" you say, "Couldn't the core not be flowing?" Perhaps, but our understanding of how heat moves in a fluid is pretty good. And we know that at some point, in order to move the heat out, the fluid has to convect (as the dynamo model requires). So while we haven't directly measured the flow of fluid in the core, arguing that it isn't happening requires at least some explanation of the lack of convection we have every reason to expect.
That said, let's look at the notion that the oceans are responsible. This ought to be measurable if it's worth talking about. We can get close enough to the oceans that we should easily be able to measure variations in the local field due to the oceans. Heck, tides and changes in circulation patterns ought to manifest temporal variations that we could measure. No, I don't know that anyone has done these measurements, I would be a bit surprised if no one had. (In fact, if no one has, I ask: why hasn't the author?)
Also, I'm skeptical by comparison to Europa. That body is in a changing magnetic field that is much more powerful than Earth's (and which changes much more rapidly, every 11 hrs). The ocean required to produce the induced field has something like 3 times (from memory) the salinity of our ocean and only produces a response of ~100 nT. (Our magnetic field is around 50 mT.) I'm... skeptical.
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Re: (Score:3, Informative)
http://gsc.nrcan.gc.ca/geomag/field/sec_e.php (about secular variation)
http://en.wikipedia.org/wiki/Magnetic_declination (about magnetic declination, obviously)
Long story short, magnetic declination is the difference between the geographical North Pole and the apparent magnetic North Pole at any one place on earth. The secular variation they're talking about is the gradual change in that magnetic declination, or the apparent movement of the Earth's
Just last night... (Score:5, Interesting)
Just last night there was an interesting show on television that focused on the subject of magnetic fields associated with planets.
There was an experiment covered in the show that was essentially a large, hollow orb filled with liquid sodium (a substitute for the iron at Earth's outer core. It is impossible to reproduce the pressure and heat of our Earth's guts in such a small scale experiment) which was then spun at a comparatively equal rate to that of Earth. The orb began producing strong magnetic fields.
I somehow doubt that if the same experiment were to be reproduced solely with a thin layer of salt water on the surface (and no sodium inside) that it would produce such strong magnetic fields. That being said, while the thought of Earth's magnetic field being produced solely by the water on the surface is interesting, personally I think it is more then likely a combination of the two factors rather then one alone that produces our protective magnetic field.
In addition, I wonder if the flux in ocean water levels, historically speaking, coincides with the strength and direction of past magnetic fields as recorded in ancient lava flows. If so, this would seem to back up the theory proposed in the article.
Re: (Score:3, Interesting)
Seriously...please do. I was aware of the whole molten sodium ball thing because I remember that spinning 13 tons of molten sodium could be a REALLY bad idea. However, the last I saw of it they were still preparing and had not actually done anything yet.
Also...TFA isn't saying the field comes from water, it says variations in the field come from water passing through the main field. In typical
It doesn't say ocean currents cause the field (Score:5, Informative)
Pseudoscientists attend! (Score:4, Interesting)
Re:Pseudoscientists attend! (Score:5, Interesting)
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Winds (Score:4, Funny)
Re:But this would mean?!?!?!?!? (Score:5, Insightful)
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Re:But this would mean?!?!?!?!? (Score:4, Informative)
Yes exactly water ice in comets. Do you know what a comet's tail is made out of? Water evaporated and removed from the comet by solar radiation.
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Re:But this would mean?!?!?!?!? (Score:5, Insightful)
Of course water responds to solar radiation - that's how we get clouds! :-)
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Re:Actually, negative (Score:4, Insightful)
In fact, Earth right now is leaking atmosphere faster than Mars is, pound for pound.
Considering how thin Mars' atmosphere is, that's not at all surprising.
-jcr
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Re:But this would mean?!?!?!?!? (Score:4, Funny)
What was it before?
A coffee coaster.
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