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I heard about the georeactor hypothesis (Herndon, 1993), which claims that there is a natural atomic fission reactor in the Earth's core giving rise to the geomagnetic field. Further, Herndon claims that this reactor will shut down, causing Earth's magnetic field to disappear at some time between a hundred years to a billion years from now. Is this possible?

References

Herndon, J. M. (1993). Feasibility of a nuclear fission reactor at the center of the Earth as the energy source for the geomagnetic field. Journal of geomagnetism and geoelectricity, 45(5), 423-437. Link

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Radja Callier
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  • Isn't the geo-reactor hypothesis about fission being a heat source for the the gas giants? If so, what does that have to do with Earth's magnetic field? – kingledion Dec 27 '16 at 21:29
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    Hello, and welcome to Stack Exchange. My brief Googling of this theory yielded a number of references to "maverick" and "not well accepted". – Daniel Griscom Dec 28 '16 at 00:07
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    Regarding the (currently three) close votes: while the "fission reactor at Earth's core" hypothesis is arrant bosh, I don't think that this in itself is a reason to close this question: this is as good a place as any to refute it. Obviously we don't want questions open to refute any old non-notable erroneous claim ("My mate Jeff told me there are marshmallows on Venus!") but I think this one clears the bar: the "fission reactor" bit at least was published in J. Geomag. Geoelectr., a relatively respectable journal. – Pont Dec 28 '16 at 11:24
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    Please add links to your question, so that we don't have to search for it. – Jan Doggen Dec 28 '16 at 18:57
  • @kingledion I think "georeactor" is a catch-all term for any naturally occurring nuclear reactor in a planetary body. Herndon seems to be proposing that many planets have a georeactor core, and that in Earth's case the geomagnetic field is produced in a proposed "georeactor fission-product sub-shell" rather than (as is commonly accepted) by convection in the liquid outer core. – Pont Dec 28 '16 at 19:52
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    Related: http://earthscience.stackexchange.com/questions/2950/what-are-the-high-field-strength-and-large-ion-lithophile-hfs-or-hfse-lil-or – David Hammen Dec 29 '16 at 00:23
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    Related: http://earthscience.stackexchange.com/questions/4798/what-percent-of-the-earths-core-is-uranium – David Hammen Dec 29 '16 at 00:25
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    Related: http://earthscience.stackexchange.com/questions/8214/why-is-uranium-only-in-the-crust-really/8216 – David Hammen Dec 29 '16 at 00:26
  • I'm voting to close this question as off-topic because this is "pure bosh." – David Hammen Dec 29 '16 at 00:28
  • @Pont: There is a site on the stackexchange network dedicated to "arrant bosh", http://skeptics.stackexchange.com. This question would be much better suited there. – David Hammen Dec 29 '16 at 00:29
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    The concept of a georeactor is "arrant bosh" from the perspective of chemistry, which says that uranium is about as lithophilic as an element can get and this is almost absent from the core, and from the perspective of physics which says a uranium georeactor would be emitting neutrinos. Those neutrinos have not been observed. – David Hammen Dec 29 '16 at 00:35
  • @DavidHammen The skeptic site only cares about loony science, like "the earth is hollow", this one has at least a ring of science to it, so they won't touch it. I don't think the question is as bad as all that, but it was poorly researched. – userLTK Dec 29 '16 at 05:40
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    @DavidHammen I think Gordon Stanger's answer, and your comments, demonstrate why this question fits better here than at Skeptics: this site has members with the relevant expertise to refute the claim. It seems a little bizarre to accept flat earth questions but reject questions on a hypothesis which at least managed to pass peer review in a decent journal. – Pont Dec 29 '16 at 08:12
  • @Pont - Most geologists, geochemists, and geophysicists view Herndon's nonsense as just shy of loony science. But given that we had a flat earth question here (egads!), I'll make my comment into a question. – David Hammen Dec 29 '16 at 09:38
  • The neutrino experiments KamLAND and Borexino have conclusively ruled out any possibility of a currently active reactor at the Earth's core (and been able to conclusively attribute a bit over half the geothermal flux to decay activity of uranium and thorium; alas the potassium contribution is inaccessible to those experiments). – dmckee --- ex-moderator kitten Feb 20 '18 at 15:58

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The conventional explanation for the Earth's magnetic field is that some combination of differential rotation and/or convection occurs in the Earth's outer core, primarily in molten iron-nickel (+ sulphur, hydrogen etc.), which acts as a kind of dynamo. Whilst we can't prove it by direct observation, this seems an eminently plausible mechanism. If this is true, then the heat of the core will eventually dissipate, resulting in freezing of the core and cessation of the Earth's magnetic field. The existing heat is partly primordial and partly radiogenic from the decay of U, Th and K, and will take many billions of years to dissipate.

The georeactor hypothesis requires a critical mass of uranium at the centre of the Earth to start up and maintain a nuclear reaction. There are two reasons why this hypothesis is seldom taken seriously except by Herndon himself. Firstly, in order for uranium to reach criticality it has to be a very high concentration of uranium. There is no known concentration mechanism which could achieve this in the Earth's core, whereas there are many reasons to believe that the uranium would be dispersed or 'poisoned' by lead and other heavy metals. Whilst the pressure at the Earth's core would be immense, gravitational separation, i.e. density fractionation, would be almost non-existent. Secondly, if this hypothesis was correct we would expect to see a huge flux of anti-neutrinos in such detectors as the super Kamiokande. We don't. So I'm not losing any sleep at the prospect of the Earth losing it's magnetism within the next billion years.

Gordon Stanger
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