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Heating of the earth's core

  1. Oct 11, 2003 #1
    Heating of the earth's core must have a logical
    solution, which led me to this idea, the work
    done by gravity on vibrating molecules throughout
    the earth moves the surface heat of the earth
    towards the earths core,amplifing it as it moves
    to the earth's center.This is backed up by the
    fact that, if you had molecules bonded together in
    a long string vibrating back and forth, and kept
    one end vibrating at a minimum velocity and applied gravity
    along the direction of the string
    towards the other end,you would find that end
    opposite to the one maintianed at minimum velocity
    would be vibrating at a greater velocity than
    the minimum velocity end.Could it be possible that
    the earth's core is heated this way?
  2. jcsd
  3. Oct 12, 2003 #2
    I think no. The string idea may make sense, but I didn't understand it. I think no because if hot air balloons rise because they are less dense, then so too would hot molecules. Therefore one would have to do work to make the hot molecules move generally toward the center. I've heard two theories that I'm partial to: massive amounts of radioactivity at the core, which makes sense considering how dense radioactive stuff is. The other is a neo-aether theory where matter is considered to be 4d vorticies in this aether, and apparently when the aether gets to the center of the vortex, it pops out of existence. But because the aether is, well, etherial, you never run out of it. It's really kind of like a spirital essence. BTW, I've heard of the Michaelson-Morley experiment, but I like this aether theory though because it explains the null result: If aether is flowing into all massive bodies, then gravity is a push force resulting from this aether 'wind' and this wind blows normal to the surface of a body. (Radially inwards in the case of spherical bodies.) If the MM experiment was conducted vertically here on earth, one could prove this one way or another. But I digress, so by some method I don't understand, this influx of aether is supposed to cause the interior heating of all bodies, but is only noticable on large scales, just like gravity, so one really doesn't see it in everyday life.
    Last edited: Oct 13, 2003
  4. Oct 12, 2003 #3


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    Its important to understand that the Earth isn't gainin/generating heat. All of the heat in the core is residual - it was created in the formation of the Earth from gravity.
  5. Oct 12, 2003 #4


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    Actually, most the heat in the interior of the earth is due to naturally-occuring radioactivite isotopes.

    - Warren
  6. Oct 12, 2003 #5


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    You sure? Thats a whole ton of radioactivity.
  7. Oct 13, 2003 #6
    Look's like we have two experts disagreeing on basic facts. You guys, the fact is that no one really knows for sure the source of the Earth's core heat (or if it is increasing/decreasing/steady) or the exact amount of that that is attributable to each different possibility (if more than one is occuring). The radioactivity one makes sense though, of all the radioactive stuff on Earth, most of it would fall to the core if it was liquidish and submersed in liquidish stuff because of its high density. This is esp. true in this case where most of the Earth's mass is liquidish (I think). Yes, I know, liquidish is not a word!
  8. Oct 13, 2003 #7


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    I like it...feel free to use it in this forum!

    This topic, however, must go to the Other Sciences forum.

    p.s. Welcome to PF, Carl! :smile:
  9. Oct 13, 2003 #8


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    Actually, the term you mean is plastic

    I would say that both are correct, it is a combination of residual heat and radioactive decay. The radioactive decay acting to slow the cooling.
  10. Oct 13, 2003 #9


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    No need to call me an expert here - this isn't my field.

    It just seems to me to be unnecessary to assume the core is highly radioactive. And that it would make a planet like Jupiter considerably cooler since it must contain far less radioactive elements (by mass percentage), yet Jupiter gives off a lot of heat.

    Gravitational collapse is what initially heats stars and gas giants and that's not all that difficult to model. It doesn't seem reasonable to me to think there must be another source for the heat in the earth.
    Last edited: Oct 13, 2003
  11. Oct 14, 2003 #10
    I thought I heard at some point that they modeled those type of things and that the heat coming from the core was anomalous. IMO, russ should have the benefit of the doubt in expertise and for all intents and purposes he's an expert on most things, unless of course he humbly denies it.
  12. Oct 14, 2003 #11
    So where dooes the heat come from?

    So far we have seen three ideas I think.

    Residual compression heat from the original formation of the Earth. However I have read somewhere that it would have taken only a few (2-3) billion years for the Earth to cool, when looking at the normal physical relationships.

    Another idea is the nucleair core of the Earth, but nuclear engineers who know how critical parameters of nuclear reactors are, usually strongly oppose this idea. Although random natural radioactive decay of elements would generate some heat througout the inner earth, slowing down the cooling process, it is doubtfull if that could amount to retain such a tremendous heat.

    Then there seem to be some crackpot view with vibrations and vortices. Can't really work with that.

    Now, what generates heat in nature other than chemical and nuclear processes? Compression and friction for instance. Now, the mentioned causes seem not sufficient to retain so much heat. We may have to add another unaddressed heat source: friction!

    Unthinkable? Well, I do have this hypothesis.

    Why is Venus so extreme hot (720 degrees Kelvin) ? greenhouse runaway? Come on.
  13. Oct 14, 2003 #12


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    Combination of that and rampant volcanism, AFAIK. The greenhouse runaway may also be a result of volcanism. What little data we have show crustal plateaus etc that suggest a very active geology.

    I really don't think tidal friction is truely a significant factor in this. There is certainly no evidence for that being a significant factor, at least as far as I am aware of. If we are working on the idea of this volcanism being the effect of the tidal friction, then this is disputed by heavy volcanism further out in the solar system. Eg. mars.
  14. Oct 15, 2003 #13
    OK, let's explore this some more, with the consent of the thread owner of course. So Carl, if you don't mind.

    We were talking about Earth interior heat. Heat is energy. There was some law with consevation of energy. We could have a look at Earths total energy. The main components of Earths energy could be it's turning energy and it's interior heat.

    Now, let's look at venus. As Venus is supposed to be Earths twin planet with most parameters within the same rough order of magnitude, the energy equation is quite different. Venus has much more heat but no rotation, actually a little backwards rotation.

    So what does this suggest. All Venus previous rotation energy may have been converted to heat. Consequently Earth rotation energy may also be converting to heat gradually, but only noticaeble witin the interior so far.
  15. Oct 15, 2003 #14


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    The problem with modeling heat loss for a planet is that a couple of clouds is all it takes to throw the end result way off.
  16. Oct 15, 2003 #15


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    But Jupiter is a much larger sphere, and therefore has less surface area for its mass. It would be expected to have a higher initial temperature, and to cool more slowly.
  17. Oct 15, 2003 #16


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    Quantification anyone?

    Re the Earth:
    1) the vertical heat flow through the upper parts of the crust is easily measured
    2) the energy generated by radioactive decay (40K, U, Th, etc) is well known; within the Earth it all gets turned into heat
    3) make some reasonable assumptions about which elements moved preferentially to the core, and which to the crust
    4) build your model, press the GO button, and ....

    Re Venus:
    1) solar insolation is well known
    2) atmospheric composition is (now) well known
    3) {like 4) above}

    Re Jupiter:
    A few more complications as the composition of the Jovian core isn't well understood. However, the major new factor is the gravitational potential energy converted to heat as the planet differentiates; esp as He settles to the core (and H rises).
    Last edited: Oct 16, 2003
  18. Oct 15, 2003 #17
    I'll admit that it does seem weird that the interior of the earth is heated by radiation. But I'm pretty sure it's quite well accepted. I don't remember numbers, but I think uranium constitutes a much greater proportion of the earths composition than one would naturally think. Furthermore, I don't think it would take a huge amount of radiation, since there is so much insulation to keep things hot.

    I once read an article, can't remember journal or specifics, about this wierd uranium rich formation under Africa I think it was. Apparently it was acting as some large, very slow, self sustaining breeder reactor. Like I said, I don't remember the details. Apparently they used the data to calibrate uranium-thorium dating, and turns out the method is quite accurate.
  19. Oct 15, 2003 #18
    This is an interesting discussion I've started
    here.I'm not saying that the energy is created out
    of thin air,what I am saying is that the sun's
    energy absorbed on then surface planet is transfered by gravity to the interior of the planet.With a solid planet modeling this is tricky.With a gas giant the model is simple.
    Each molecule of a gas giant migrates over it's
    entire interior.As it moves towards the center,
    from the surface, it gains velocity due to the work done by gravity.As it returns to the surface,
    it loses velocity due to work done against gravity,but it also loses energy due to the molecule radiating infrared radiation.This causes
    the molecule to return to the surface at a slower
    velocity than it left.Now it absorbs more energy from the sun.I could get into this in terms of
    collision science but it is a little to technical
    for this format.If you take away the sun's heat, the gas giant would freeze solid in a relatively
    short period in terms of the geological timeline.
    Its the sun's radiation that maintains the gas giant's heat for sure.
  20. Oct 16, 2003 #19


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    Both Jupiter and Saturn emit (mostly in IR) more energy than they receive from the Sun (mostly in the optical), so by your reasoning they are generating energy 'for free'. Much more likely that it's due to the fractionation of helium and neon, energy left over the initial collapse, and continued contraction.
    This would only be the case if convection were the mode of heat transport throughout the entire planet (and there were no solid core).
    [edit: 'hot' molecules won't sink anyway; in a convective flow, they rise]
    However, IIRC, there is a solid core - metallic hydrogen? - and the atmosphere is not fully convective. Perhaps a good tutorial on planetary physics would help?
    You're referring to Oklo, I think. It was a natural nuclear reactor (stopped a long time ago) and it has enabled a few strong constraints to be placed on the time variability of important physical constants. More info here:

    However, normal radioactive decay generates heat, and it's that which is the most important source of heat for the Earth's interior.
    Last edited: Oct 16, 2003
  21. Oct 16, 2003 #20
    Carl, I've already determined and said that hot molecules sinking to the core and coming back cool defies Archimedes' principle and the laws of thermodynamics, because, in Jupider for example, one would have to have a huge Maxwellian demon living there to cause this self organization of temperature differential reverse to bouyancy.
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