Slashdot Mirror


Ocean Currents Proposed As Cause of Magnetic Field

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."

30 of 333 comments (clear)

  1. Could be... by houstonbofh · · Score: 4, Interesting

    There is enough junk floating on the oceans that the currents could be ferrous.

    1. Re:Could be... by fahrbot-bot · · Score: 5, Funny

      So we're talking about _electric_ ocean currents? How is right hand rule newsworthy?

      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".

      --
      It must have been something you assimilated. . . .
    2. Re:Could be... by Anonymous Coward · · Score: 4, Funny

      Lonely geek has moved on to the Fleshlight rule.

  2. Polarity switch by indre1 · · Score: 4, Funny

    So basically we know that global warming has taken over our ocean's currents when our compasses start pointing to the south...

    1. Re:Polarity switch by Killer+Orca · · Score: 4, Informative

      No, the poles already reversed once in theory http://en.wikipedia.org/wiki/Earth's_magnetic_field, and are likely to keep reversing, though none of us will be around to find out.

    2. Re:Polarity switch by vulpinemac · · Score: 4, Informative

      No, the poles already reversed once in theory http://en.wikipedia.org/wiki/Earth's_magnetic_field, 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.

    3. Re:Polarity switch by pnewhook · · Score: 4, 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.

      --
      Tesla was a genius. Edison however was a overrated hack who liked to torture puppies.
    4. Re:Polarity switch by Daychilde · · 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!)

      --
      A cheerful little bird is sitting here singing.
    5. Re:Polarity switch by RockDoctor · · Score: 5, Informative

      If you do some non-wiki research, you will find out that Earth's magnetic field has reversed many times over the eons.

      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.)

      We're overdue now by several thousand years.

      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.

      This Global Warming may be just another indicator that such a change is imminent.

      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.

      --
      Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"
  3. I may be wrong, Im not an astrologer by edittard · · Score: 4, Interesting

    Aren't there planets that do have magnetic fields, but don't have oceans? And aren't there moons that are the opposite case?

    --
    At the bottom of the /. main page it says 'Yesterday's News'. Well they got that right.
    1. Re:I may be wrong, Im not an astrologer by gardyloo · · Score: 5, Funny

      I can pretty much guarantee that astrologers would have no idea what you're talking about :)

    2. Re:I may be wrong, Im not an astrologer by Creepy+Crawler · · 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.

      --
    3. Re:I may be wrong, Im not an astrologer by VampireByte · · Score: 4, 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.

      --

      Run and catch, run and catch, the lamb is caught in the blackberry patch.

    4. Re:I may be wrong, Im not an astrologer by Creepy+Crawler · · Score: 4, 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.

      --
    5. Re:I may be wrong, Im not an astrologer by Iron+Sun · · Score: 4, 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.

    6. Re:I may be wrong, Im not an astrologer by Korin43 · · Score: 4, Interesting

      I wonder if the idea that Ganyemede has a liquid iron core is based on the assumption that only liquid iron cores cause magnetic fields?

    7. Re:I may be wrong, Im not an astrologer by GIL_Dude · · Score: 4, Interesting

      Current flow causes magnetism. You can demonstrate that with a non-magnetic copper wire and a battery. The copper doesn't suddenly become "iron like" and have a crystalline structure that responds (is attracted by) to magnetism. It is simply the current flow that causes this.

      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).

  4. Summary wrong: Oceans only small variations by Anonymous Coward · · 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.

    1. Re:Summary wrong: Oceans only small variations by CheshireCatCO · · 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.

  5. Re:Uh, right. by MrMista_B · · Score: 4, 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.

  6. Re:But this would mean?!?!?!?!? by larry+bagina · · Score: 5, Insightful

    The magnetic field is believed to prevent solar wind from eroding water and oxygen. If ocean water creates a magnetic field that prevents water from eroding .... that's a serious chicken/egg problem. FWIW, Mars used to have water and may have at one point had a stronger magnetic field than the Earth. It currently has a weak magnetic field and negligible water. Mars doesn't have a large moon to create tides, either.

    --
    Do you even lift?

    These aren't the 'roids you're looking for.

  7. Re: Uh, right. by sakdoctor · · 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.

  8. Re:Uh, right. by pclminion · · 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.)

  9. Just last night... by Anachragnome · · Score: 4, 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.

  10. It doesn't say ocean currents cause the field by John+Hasler · · Score: 5, Informative

    The paper does not say that ocean currents cause the magnetic field. It hypothesizes that ocean currents cause secular variations in the magnetic field.

    --
    Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
  11. Especially when we keep crashing planes into them by atmurray · · Score: 4, Funny

    Too soon?

  12. Because someone has to respond to trolls by Anonymous Coward · · 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.

  13. Re:Pseudoscientists attend! by osu-neko · · Score: 5, Interesting

    Science has always reserved its greatest accolades for those who prove what came before to be wrong, and every scientist in the world knows the best way to become famous is to prove everyone else wrong. Nevertheless, pseudo-scientists always argue that scientists have some vested interest in preserving the current order (and thus dooming their careers into obscurity when they could have become famous Nobel prize winners). This argument has never made any sense, but that doesn't stop them from making it. So, one more example won't make any difference to them -- people who advocate a bad argument that runs counter to evidence are not dissuaded by more evidence.

    --
    "Convictions are more dangerous enemies of truth than lies."
  14. God built the world for man... by TapeCutter · · Score: 4, Interesting

    Imagine a puddle waking up one morning and thinking, 'This is an interesting world I find myself in, an interesting hole I find myself in, fits me rather neatly, doesn't it? In fact it fits me staggeringly well, must have been made to have me in it!' This is such a powerful idea that as the sun rises in the sky and the air heats up and as, gradually, the puddle gets smaller and smaller, it's still frantically hanging on to the notion that everything's going to be alright, because this world was meant to have him in it, was built to have him in it; so the moment he disappears catches him rather by surprise. - D. Adams.

    --
    And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
  15. Re:But this would mean?!?!?!?!? by Daychilde · · Score: 5, Insightful

    Of course water responds to solar radiation - that's how we get clouds! :-)

    --
    A cheerful little bird is sitting here singing.