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Thread: Why hasn't the earth cooled off?

  1. #1 Why hasn't the earth cooled off? 
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    How come the interior of the earth is still hot? How can it be that it hasn't cooled off in all these years? What are we talking here? Several billion years? Come on.


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    i thought radioactive decay in the earth is whats keeping the interior warm


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    Quote Originally Posted by johnny
    i thought radioactive decay in the earth is whats keeping the interior warm
    I believe that is true...
    I know that's what's keeping the sun hot; but I'm not sure about the Earth...more than likely, I guess.
    Whence comes this logic: no evidence = false?

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  5. #4 Re: Why hasn't the earth cooled off? 
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    Quote Originally Posted by TomBrooklyn
    How come the interior of the earth is still hot? How can it be that it hasn't cooled off in all these years? What are we talking here? Several billion years? Come on.
    Point 1: It has cooled relative to what it was shortly after it formed: molten all the way down.
    Point 2: As noted by others, radioactive decay continues to generate internal heat. [scientstphilosophertheist, the sun is powered not by radioactive decay (fission) but by fusion]
    Point 3: The heat flow from the Earth is painfully low. Over an entire year it would be sufficient only to melt a thin layer of ice, less than a centimetre thick.
    Point 4: The heat flow is low in part because the planet is receiving large amounts of heat from the sun and is nicely insulated by its atmosphere.
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  6. #5 Re: Why hasn't the earth cooled off? 
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    Quote Originally Posted by Ophiolite
    Quote Originally Posted by TomBrooklyn
    How come the interior of the earth is still hot? How can it be that it hasn't cooled off in all these years? What are we talking here? Several billion years? Come on.
    Point 1: It has cooled relative to what it was shortly after it formed: molten all the way down.
    Point 2: As noted by others, radioactive decay continues to generate internal heat. [scientstphilosophertheist, the sun is powered not by radioactive decay (fission) but by fusion]
    Point 3: The heat flow from the Earth is painfully low. Over an entire year it would be sufficient only to melt a thin layer of ice, less than a centimetre thick.
    Point 4: The heat flow is low in part because the planet is receiving large amounts of heat from the sun and is nicely insulated by its atmosphere.
    Oh, thanks for correcting me on that.
    Whence comes this logic: no evidence = false?

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    isnt uranium the heaviest natural occuring element? so would it make sense that the core is all uranium?
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    No, I dont think uranium is the heaviest naturally occuring, I think there's a few more; although they may not be as abundant, your point remains valid though.

    It isnt fully understood why the earth is so how at its centre so some suspect that there is a naturally occuring nuclear reactor at the core, but this is all speculation; there isnt any hard evidence
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    Quote Originally Posted by johnny
    isnt uranium the heaviest natural occuring element? so would it make sense that the core is all uranium?
    that's a good question.

    Uranium is relatively rare as a % of the elements that makeup the Earth. Not all that significant. Also Uranium binds to lighter elements and is 'kept afloat'...a bit like a a hammer would sink to the bottom if you threw it in a pond but not sink if it landed in a row boat.

    The reverse of your question also tells about some deposits. Why are there are heavier huge nickel/zinc deposits, etc. near the surface? These are the result of early bolide collisions after the Earth was formed in the early stages of the solar system.The huge deposits such as those in the Sudbury area of Ontario are thought to have been impacts on denser surfaces.
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    question; what ever material one would find in the core, what state would this material have?
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    Why hasn't the earth cooled off? The earth is not as hot as it used to be, so to some degree it has cooled off, but it is still a heat engine which drives processes with surface expressions such as the magnetic field, volcanism, seismicity, plate motion. The engine is and has always been powered by heat sources, like radiogenic heat, latent heat, gravitational potential energy is converted into heat, there is even some tidal heat. These heat sources are still supplyin heat to the earth today, otherwise it would have cooled off a long time ago.

    The material in the core is predominantly iron. This material is solid in the inner core and is liquid in the outercore. The core does not have uranium in it. I believe most of the earth's uranium is found in the lower mantle and in the crust.
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    Quote Originally Posted by miomaz
    question; what ever material one would find in the core, what state would this material have?
    Plasma perhaps?
    Whence comes this logic: no evidence = false?

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    Quote Originally Posted by scientstphilosophertheist
    Quote Originally Posted by miomaz
    question; what ever material one would find in the core, what state would this material have?
    Plasma perhaps?
    Cripes, I haven't studied this for 30 years.

    It would be a solid.

    Some claim that if the core was developed quickly that that it's essentially a single iron crystal. A lot depends on temperature and there's no real way of knowing other than educated speculation to within a few thousand degrees c.
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    The core is solid because of the pressure or because of it being cool enough for it to stay in a solid state?

    if the core would be liquid how high must the temperature be so that this is possible?

    Sorry, but I just know very little in this section.
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    Quote Originally Posted by miomaz
    The core is solid because of the pressure or because of it being cool enough for it to stay in a solid state?

    if the core would be liquid how high must the temperature be so that this is possible?

    Sorry, but I just know very little in this section.
    That would depend, we know that in the past the core was completely liquid and that the inner core started to crystallise out about 1.7 billion yrs ago. So you would expect that if you could get the core back to the conditions it had in its early life then you might expect that the core would be liquid again. I'm not sure if it's that simple though, and besides, I'm not sure how hot it was down there 2 billion yrs ago anyway.
    At the moment people don't know that much about the inner core, currently geophysicists are working on problems, like what is the temperature at the inner- /outer- core boundary? What is the crystal structure? What is the composition? Why is there an observed anisotropy, whereby poleward p-waves travel 4-6% faster through the inner core than equatorward p-waves? Why is the inner core 3-4% less dense than it would be if it were made out of pure iron?
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    Quote Originally Posted by Jellyologist
    Quote Originally Posted by johnny
    isnt uranium the heaviest natural occuring element? so would it make sense that the core is all uranium?
    that's a good question.

    Uranium is relatively rare as a % of the elements that makeup the Earth. Not all that significant. Also Uranium binds to lighter elements and is 'kept afloat'...a bit like a a hammer would sink to the bottom if you threw it in a pond but not sink if it landed in a row boat.
    so does that mean when uranium reacts and forms into an oxide, the oxide state will keep it a float?

    The reverse of your question also tells about some deposits. Why are there are heavier huge nickel/zinc deposits, etc. near the surface? These are the result of early bolide collisions after the Earth was formed in the early stages of the solar system.The huge deposits such as those in the Sudbury area of Ontario are thought to have been impacts on denser surfaces
    what about VMS deposits like the ones in Timmins, could that be another reverse reason to heavy metals being close to the surface? could the convection current in the earth circulate heavy metals to the surface? if thats true could our core be heterogenuos instead?
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    THe earth is cooling off, it's such a huge mass it takes a little time, for example I remember my brother telling me that bell his company had cast took a week to cool down....
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    Quote Originally Posted by johnny
    Quote Originally Posted by Jellyologist
    Quote Originally Posted by johnny
    isnt uranium the heaviest natural occuring element? so would it make sense that the core is all uranium?
    that's a good question.

    Uranium is relatively rare as a % of the elements that makeup the Earth. Not all that significant. Also Uranium binds to lighter elements and is 'kept afloat'...a bit like a a hammer would sink to the bottom if you threw it in a pond but not sink if it landed in a row boat.
    so does that mean when uranium reacts and forms into an oxide, the oxide state will keep it a float?

    The reverse of your question also tells about some deposits. Why are there are heavier huge nickel/zinc deposits, etc. near the surface? These are the result of early bolide collisions after the Earth was formed in the early stages of the solar system.The huge deposits such as those in the Sudbury area of Ontario are thought to have been impacts on denser surfaces
    what about VMS deposits like the ones in Timmins, could that be another reverse reason to heavy metals being close to the surface? could the convection current in the earth circulate heavy metals to the surface? if thats true could our core be heterogenuos instead?
    Re your last question. I don't know. however, the metals didn't come from the core. The core is stable. VMS deposits are probably sporadic and depend on upward flow of early deposition of metals shortly after the Earth started to solidify.

    A lot of the questions about what's' down there' depends on how the Earth originally formed. There's not consensus except for broad generalities. It's been a bit of an open book as to why the Earth formed differently from our sister planets and is denser than Venus or Mars.
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    I think the Earth's core is made from Uranium.
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  20. #19  
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    Quote Originally Posted by leohopkins
    I think the Earth's core is made from Uranium.
    I think it is mostly Iron, as the earth has a magnetic field. Also we know that meterorites often contain large amounts of Iron, with some being almost pure Iron yet uranium in meteorites shows only in trace amounts.

    Back on topic another possible cause of heat generation in the earth is due to the gravitaional forces of the sun and moon. The precedent for this is IO, a moon of jupiter on which active volcanes have been observed, IO is not large enough to have remained hot since it's birth, the tremedous pull of the gravity of Jupiter is though to be squeezing an pulling it creating heat (rather like bending a piece of soft iron back and forth till, you will find it generates heat).
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