Homepage Forums Scientific Method, Skepticism Earth's core: Radioactive heating vs. Tidal heating

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  • #641
    Avatardash
    Member

    Brian H wrote: The reason the Earth’s core is still molten, and not cooled and hardened, is radioactive warming. We’re standing on a big, slow reactor!

    I don’t believe that theory. Last I heard only the moon Io and Earth have volcanoes. In Io’s case it’s tidal pull that keeps the core liquid. And we’ve got this big oversized moon. I believe the moon causes tides in the liquid core of the earth, and this movement keeps the core liquid.

    -Dave

    #4426
    Avatartexaslabrat
    Member

    dash wrote:

    The reason the Earth’s core is still molten, and not cooled and hardened, is radioactive warming. We’re standing on a big, slow reactor!

    I don’t believe that theory.

    -Dave

    Regardless if you believe it or not…it’s true 😉

    http://www.newscientist.com/article/mg18725103.700 is just one of many studies confirming it.

    The tidal forces exerted by the moon on the earth (and conversely by the earth on the moon) pale by comparison to those imposed on Io by Jupiter. While tidal forces certainly can play a *role*…they are far and away minor players in the heating phenomenon.

    #4427
    Avatarjamesr
    Member

    I’ve always loved the story of Rutherford giving his talk at the Royal Institution on the age of the earth in front of Lord Kelvin, who dozed off through most of it.

    Lord Kelvin and the age of the earth – google books

    One of the many things that inspired me to go into physics – how like a detective piecing together the clues from observations and discoveries we can learn the underlying truth of what is going on.

    #4428
    Avatardash
    Member

    texaslabrat wrote: Regardless if you believe it or not…it’s true 😉

    http://www.newscientist.com/article/mg18725103.700 is just one of many studies confirming it.

    Speaking of this one article, because a group of scientists conducted an experiment detecting anti-neutrinos and they claim they come from the planet’s core, you automatically accept this as proof?

    “Science is the belief in the fallability of experts.” — Richard Feynman

    This same scientific establishment believes in the Big Bang. Do you?

    Later in the article, one fellow says “this will require a whole network of detectors.” Meaning big dollars, funding, profits, etc. Do you see?

    Whether neutrinos are even real are not is debatable.

    Just think about the premise of uranium decay being the cause. Uranium is 19.1 grams/cc, iron is 7.874 grams/cc. Wouldn’t uranium sink to the center of the earth, through the molten iron, and once it’s concentrated wouldn’t it all burn up through fission very quickly?

    Meanwhile we see the tides due to the moon rising and falling every day. We see the earth itself deformed by the moon. And the gravity gradient penetrates the earth’s interior also.

    Anyway I’m not convinced radioactive decay is the cause.

    -Dave

    ETA – I looked on Wikipedia about Venus, Venus has no active volcanoes but there were signs of volcanic activity in the past. Venus is about the same size as the earth. If radioactive decay is causing the heat, why aren’t there active volcanoes on Venus? Moreover, Venus rotates very slowly, its day is similiar to its year. Therefore tidal activity from the sun would be miniscule. And Venus has no big moon. Solution? Venus used to rotate faster. Tidal action from the sun slowed it down. The heat generated volcanic activity in the past, but this has now died out.

    #4429
    Avatarjamesr
    Member

    I don’t get your reasoning that radioactive decay heat is responsable. OK maybe it’s not the only factor butit has got to be by far the largest contribution to heat geteration. You only have to look at what the natural backround radioactivity all around us is to realise, and a quite back of the envelope calculation with the mass of the earth to realise that you can’t just toss it aside as irrelavent.

    neutrinos are defintinely real – the spread in electron energy in beta decay means there must be a third particle shareing the energy – unless you want to throw out conepts like the conservation of momentum.

    Most Uranium occurs in the crust as triuranium-octoxide which is pretty stable and has a density of around 8.3grams/cc. I suspect the proportion of Uranium dissolved into molten iron it would not sink to the core as the convective zone stirs it up to much to settle out. The central core of the earth is small compared to the whole volume – most of the heat would be produced in the rest of the mantle.

    Fission is hard to acheive naturally – it needs a moderator, a light element such as hydrogen (as in water) to slow down the neutrons, in just the right proportion geometrically to acheive criticality. Uranium metal needs to be very pure with more than around 20% U-235, and no other neutron absorbing impurities to achive any appriciable level of fission on it’s own without a moderator.

    The lack of active volcanism on venus now can be put down to the lack of water – plate technonics driven by water present in the crust cause most volcanism on earth. Subducted crust sinks into the mantle and dissolves making it less dense – it then rises and gases dissolved under pressure begin to come out of solution, driving their way through the crust. It is thought now that the major force on plates is being pulled down at the edges by the subduction, rather than being pushed as the mid ocean ridges or friction on the under side from the flow of mantle. The exception are volcanos like hawaii which form under hot convective plumes. It may be that on venus this mechanism is not strong enough now to cause volcanos of this type anymore.

    The role of earths magnetic field is one aspect that is still little understood – how does the dynamo maintain itself?

    #4430
    Avatardash
    Member

    jamesr wrote:

    neutrinos are defintinely real – the spread in electron energy in beta decay means there must be a third particle shareing the energy – unless you want to throw out conepts like the conservation of momentum.

    ….

    The role of earths magnetic field is one aspect that is still little understood – how does the dynamo maintain itself?

    The Standard Model is just the Standard Party Line. Taught as truth in schools. Hairy math not conducive to simulation. It’s useful in explaining experimental results, but does not yield insight into why things are like that. What the underyling causes are. Neutrinos, like the strong force, like dark matter, like the cosmological constant, are concepts dreamed up on whim that happen to make someone’s theory work better. Last I heard the sun was deficient in the expected amount of neutrinos.

    By no means are any of these theories to be taken as the absolute truth. Professors teach the stuff, believe it as if it’s truth, devote their entire careers to pushing forward a bit more tissue paper and spit nuances, but the truth is the whole hodge podge is a mess. Eric goes into this a lot with his Big Bang Never Happened, have you not read it? I love that book.

    As to how the dynamo maintains itself, since the earth’s magnetic field lines come out of the north and south poles, you need an electric current running along in a circle about the earth’s axis of rotation. Imagine the liquid core of the earth spinning at a slightly different rate as the surface, due to tidal effects from the moon. This relative motion could give rise to a magnetic field, if the liquid core is ionized somewhat. Venus has a weak magnetic field.

    Who knows? I don’t have all the answers. I merely have formed the habit of not believing the standard scientific party line automatically. My interest is in machine intelligence, artificial intelligence. I’m much more knowledgeable in that arena. And the corruption of this field is ridiculous. They’ll never figure it out! So I project outward to most other human understanding.

    Most science nowadays is just a scam to attract government research money. Conveniently no real useful results are required or expected. Just another form of entitlement. Good ‘ol boy network crap. From the peer review journal process all the way to tenure in universities, the system itself is corrupted.

    Oh well.

    -Dave

    #4431
    Avatarjamesr
    Member

    We seem to be getting a little off-topic here but… I applaud your skepticism Dave, I too am skeptical of a lot of current scientific dogma. But I think that for something as well understood as radioactive heating it is worth towing the party line.

    When we (focusfusion) are seen by the scientific community-at-large as being on the fringe and confrontational about everything I think they will not take us seriously on the subjects where we want them to listen, and take note of out paradigm shifting ideas.

    It takes a lot to shift a well established paradigm, and I believe there are far too many career scientists out there these days not willing to take a step back and listen to what others are saying.

    Theorys such as the standard model should be taught in school just as Newtonian gravity or any other theory is. The important thing to teach is scientific method. Theorys are useful tools to help us understand, predict and do calculations about the world. How ‘real’ something like neutrinos are is a question for philosophers, for me, they enable us to do experiments and calculations to good accuracy, and highlight (as in the solar neutrino problem) where our understanding needs improving. If someone comes up with a better theory it doesn’t mean previous calculations, such as the age of the earth, are necessarily wrong, they are just not as accurate as they could be.

    #4470
    Avatartexaslabrat
    Member

    dash,

    Since you seem so enamored with Wikipedia as your end-all-be-all reference source (discounting any other sources, it seems), here’s a Wikipedia article for you:

    http://en.wikipedia.org/wiki/Tidal_acceleration

    The gravitational torque between the Moon and the tidal bulge of the Earth causes the Moon to be promoted in its orbit, and the Earth to be decelerated in its rotation. As in any physical process within an isolated system, total energy and angular momentum are conserved. Effectively, energy and angular momentum are transferred from the rotation of the Earth to the orbital motion of the Moon (however, most of the energy lost by the Earth is converted to heat, and only about one 30th is transferred to the Moon). The Moon moves farther away from the Earth, so its potential energy (in the Earth’s gravity well) increases.

    The dissipation of energy by tidal friction averages about 3.75 terawatts, of which 2.5 terawatts are from the principal M2 lunar component and the remainder from other components, both lunar and solar.[3]

    While I haven’t verified the numbers myself, they seem to be in the same ballpark as what I remember calculating in my astronomy class years ago in college. As I said before, the tidal forces certainly contributed a non-zero component, but are far and away a minor player in core heating here (since that 3.75TW is the combined effects of all tidal friction across the entire structure of the earth and most notably in the ocean). If the majority of the heat being produced in the core (and subsequently conductively/convectively transferred to the surface to be radiated into space) were due to tidal forces as you claimed, 1) the earth would necessarily have to slow its rotation considerably more than observed 2) the earth would need to increase its orbital distance from the sun considerably more than has been observed or 3) the moon would need to increase its orbital distance from earth considerably more than has been observed or 4) some combination of 1-3 that satisfies conservation of energy of the earth-moon-sun system. The net total of the tidal forces across the entire structure of the earth are a factor of roughly 10 less than the heat being observed being generated from the core alone. I’m not sure how one could more succinctly explain that you are wrong, so I’ll just leave it at that.

    As jamesr said, being skeptical can be a good thing when accepted dogma is attached to assumptions or guesses and forced upon us via indoctrination. However, when you are trying to argue against (easily) observable fact just to be “a free thinker”…well, let’s just say the impression you leave is probably not what you are shooting for.

    #4472
    Avatardash
    Member

    texaslabrat wrote: The net total of the tidal forces across the entire structure of the earth are a factor of roughly 10 less than the heat being observed being generated from the core alone.

    What is your source for this “fact”?

    You cite an analysis for the heat generated by the tides on the core, but you claim that is 1/10th the heat observed on the surface of the earth.

    This is a proof?

    -Dave
    PS Thanks for your concern about the impression I’m trying to convey, but the truth is I don’t care what you or anyone else on these forums think of me. And your snotty attitude probably isn’t helping your reputation either, may I say.

    #4473
    Avatarjamesr
    Member

    I wasn’t sure about the 1/10 figure either so I did a bit of googling.

    The book:
    The solid earth: an introduction to global geophysics By C. M. R. Fowler gives detailed analysis of the figures for the radioactive heating and gives a bottom line figure of 2.1*10^13W = 21TW for the radioactive heat of the crust and mantle (not including the core). NB it wasn’t thought the concentration of Potassium-40 was very high in the core itself. However recent studies have found potassium does actually dissolve in iron when at very high pressures. So if there is a higher concentration of potassium-40 in the core then there will be some more heat generated there. (source)

    If the 3.75TW figure for tidal heating is correct, and using the 21TW figure from above, this would make the ratio of tidal/radioactive 3.75/21 = 1/5.6. So the 1/10 figure is correct to 1sf.

    The total rate of heat loss currently by the earth is given as 4.2-4.4*10^13W. ie. we are loosing twice as much heat as is is now being made – hence the earth is cooling. In the past the radioactive heating component would have been much larger, exponenitally so, given the nature of radioactivity. Whereas the tidal heating would have been roughly the same. Hence over the age of the earth the proportion of the stored heat due to radioactivity will be much higher than the current heat generation ratio.

    #4474
    Avatartexaslabrat
    Member

    edit: nm…it’s not my job to teach those who refuse to learn.

    #4475
    Avatardash
    Member

    jamesr wrote: The total rate of heat loss currently by the earth is given as 4.2-4.4*10^13W. ie. we are loosing twice as much heat as is is now being made – hence the earth is cooling. In the past the radioactive heating component would have been much larger, exponenitally so, given the nature of radioactivity. Whereas the tidal heating would have been roughly the same. Hence over the age of the earth the proportion of the stored heat due to radioactivity will be much higher than the current heat generation ratio.

    OK, my interpretation of what you claim this fellow said is he has computed the theoretical amount of heat generated by radioactive decay in the crust of the earth. He has evidently put some nice equations together and has some numbers.

    And you come along and accept it as fact without question. Moreover you accept his assertion that the earth must be cooling.

    Dude, it’s just a theory. It may be right. It may be wrong. But it’s not proof. You behave as if it is proof. And you get offensive when other people (such as myself) don’t accept it as fact.

    Personally I’d have been more persuaded by an argument related to the thermal conductivity of 100 miles of rock (as in the crust of the earth). We know how well rock conducts heat.

    As far as I know there are two bodies in the solar system with volcanic activity — the earth and Io. Both have large tidal forces acting on them. Venus has no volcanic activity, and presumably has the same radioactive makeup as the earth, and is about the same size, yet has no large tidal forces acting on it.

    “Science is the belief in the fallability of experts” — Richard Feynman

    -Dave

    #4476
    Avatartexaslabrat
    Member

    I know I said I wouldn’t teach the unwilling..but seeing such misguided scientific lack of knowledge on this board bothers me for some reason. So here goes.

    The heat flux out of the earth is known to be around 44TW (look it up). This should help get you started:
    http://www.google.com/search?hl=en&client=firefox-a&channel=s&rls=org.mozilla:en-US:official&hs=4uV&q=heat+flux+out+of+earth+44tw&aq=f&oq;=&aqi;=

    For tidal forces to be responsible for this, the earth would need to be losing rotational energy at the rate of *at least* 44TW as tidal friction is a consequence of trading rotational energy for heat and orbital acceleration (of the moon with respect to the earth, and of the earth with respect to the sun). Unfortunately for your “theory”, the earth is not losing rotational energy at this rate…rather it is losing rotational energy at roughly 4TW (the exact number is complicated to compute due to not-quite-spherical shape and non-uniform composition plus the un-flattening of the poles which tends to increase the speed of rotation while the frictional forces slows it down…but the rough number with a spherical assumption is good enough to show order of magnitude). There are on-going gravimetric satellite-based surveys which keep track of these issues. Much of that is explained (with citations) here:
    http://74.125.113.132/search?q=cache:-gk-ok_CbiUJ:eprints.ictp.it/165/01/moon.ps+earth+loss+rotational+energy&cd=10&hl=en&ct=clnk&gl=us&client=firefox-a

    As for comparing the Moon’s tidal influence on Earth vs Jupiter on Io…..ROFL. That’s like saying because they both contain water that my swimming pool is just like Lake Superior. They aren’t even in the same zip code in the strength of effects. As an example…Io’s rocky surface rises and falls *100 meters* due to the tidal forces from Jupiter. Compare this with the few-meter (at most) motion of *water* on earth coupled with the centi-meter scale of solid surface movement. And these effects are spread throughout the earth’s structure rather than being concentrated in the core with the lion’s share at the surface. Now, if you were talking 2 billion or so years ago when the earth was rotating much faster and the moon was much closer…then yeah, tidal heating was a significant player. But it’s been a very long time since tidal forces competed with radiogenic ones for the heating of the core and subsequent thermal flux out of the earth.

    And as for volcanism on Venus…plate tectonics plays a huge role in volcanism, and on Earth water plays a huge role in plate tectonics. Since Venus doesn’t have large oceans…well, you do the math. At this point, we don’t know enough about Venus to make conclusions and most of our theories regarding its internal structure are educated guesses. Given its retrograde rotation and other “weird” aspects, I’d be careful about trying to make apples-to-apples comparisons with Earth.

    #4477
    Avatardash
    Member

    texaslabrat wrote: I know I said I wouldn’t teach the unwilling..but seeing such misguided scientific lack of knowledge on this board bothers me for some reason.

    I don’t think we’re communicating here.

    You can cite as many pretty documents as you want, filled with equations, math. It is not proof. One must still take these “proofs” on faith. Don’t you see? They are just theories.

    Whether they are right or wrong is a matter of fact. It is not a matter of voting. If 99.99% of all scientifically minded people believe these documents you link to are correct, that still does not “prove” them true.

    Have you heard the story of how some guy determined the length of the emperor’s nose? He just asked a whole bunch of people how long they thought the emperor’s nose is. Then he averaged the result. And that’s what the length of the emperor’s nose is.

    These theories you’re presenting are not subject to experimental verification. Just like cosmology and astrophysics. It’s all theory. Prevailing popular theory is more a fad combined with politics and self interest than true scientific fact.

    You seem to take it on faith that the majority is right. Fine, that’s your privilege. I’ll stick with my beliefs, and I don’t mind being wrong. In this case it doesn’t matter if I’m wrong. But in other cases, if I happen to buck the majority and I happen to be right, there can be huge rewards — for me.

    What exactly do you hope to accomplish anyway here with your efforts on this subject? Specifically why is it so disturbing to you if 100% of all people don’t happen to agree on this one issue?

    -Dave

    #4478
    Avatartexaslabrat
    Member

    Well, I’m glad you are ok with being wrong…it must come with practice.

    And I think you need to work on your scientific lingo…actually MEASURING things is not a “theory”. The items I cited (did you even bother to read any of them? doubt it since you might actually have to admit the data don’t match your assumptions) are MEASUREMENTS. The theory comes in to make sense of said MEASUREMENTS. Just because the MEASUREMENTS don’t agree with your pet theory doesn’t invalidate them…especially when they have been continually confirmed and refined over time by independent researchers using a variety of methods.

    Taking these MEASUREMENTS, combined with a simple conservation of energy calculation (I suppose you don’t believe in that, either?) trivially shows the situation that your assumptions are completely wrong. This isn’t an issue of philosophy..it’s about black and white, right and wrong, cold hard math. On a SCIENCE-based website..that distinction is important. Now that you’ve proven yourself incapable of processing new information and adjusting your own assumptions (you know, practice the “scientific method”)…I don’t think anyone will be taking your input seriously going forward. And that is my purpose with this exchange (since you asked) after you proved yourself to be incorrigibly unable to be educated. I suppose you’ll be arguing for the flat-earth theory next.

    Have a nice day.

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