Talk:Planetary core

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It would be great if as a part of this topic, someone could explain the methods scientists used to determine what the Earth's core consists of?

What "powers" the core?[edit]

Well, I came here looking for this information, so I'll use the talk page as to suggest what should be put in. My primary question is what "powers" the core? Originally the compression of matter and gravity generated the heat, but now it is hundreds of millions of years later and it still hasn't cooled, and the magnetic strength of the Earth (caused by an ever rotating iron core) is still about 90% as it once was, which IMO, even jumps up in strength sometimes, ie. ice age, and isn't more of losing energy than preparing for a magnetic pole switch.

Is it the Earth's orbit around the sun, transferring the momentum to the Earth's core? Or the sun's slow orbit around other stars, and with the galaxy et al powering all this? Or the sun's magnetic field? What then? -- Natalinasmpf 14:56, 11 Mar 2005 (UTC)

  • Well, I'm no hard scientist here, but I'd say the sun, pressure, and in a general sense, nothing. First off, what do you mean by "powers?" The planet isn't really doing anything then falling through space. It's still liquid and hot down in the center, but where do you think this would go? The planet radiates heat out into the universe, but the sun also warms it. If the question is why is it hotter in the center then it is right here? Well then I would say that pressure, although I'd have a hard time justifying that. Something to the effect that as pressure increases, temperature increases. Now the earth isn't nearly big enough to cause a chain reaction like the sun or a black hole. Although I heard that Jupiter is so big it gives off more heat then it recieves. But I believe you are thinking about the heat death of the universe. That starts around 10^14. We've been around for about 10^9. You know, probably-ish. So yeah, earth isn't powered by anything and is winding down. 20:57, 31 October 2006 (UTC)
The Earth is four and half billion years old, and the Sun warms its interior not at all. In that time, without an internal power source (namely radioactive decay of potassium-40, uranium, thorium, etc.) it would be much cooler now than it actually is, and the crust and mantle much thicker than they are. This was worked out by Lord Kelvin in the 19th century when he famously decided that the Earth was billions of years younger than geologists then knew it to be, because he knew his thermodynamics and rates of cooling, but wasn't taking radioactive decay into account. --arkuat (talk) 01:37, 13 July 2011 (UTC)
    • I'm a geophysicist who studies the core and deep Earth. The core is still hot from its initial formation, and it cools very slowly because the only way heat escapes is through the slow creeping convection motion of the overlying rocky mantle. The mantle is solid, but over long time scales it behaves as a very very high viscosity fluid. The core was very hot initially because of the release of gravitational potential energy in separating it from its silicate rocky part. The inner core is solid and slowly freezing from the outer liquid part, and grows about 1 km every million years. The rate of cooling of the core determines whether or not convection can occur inside the outer liquid part, and this process is thought to be the only way for generating Earth's magnetic field. So yes, Earth's magnetic field is powered by cooling of the core, but if the core were to have cooled too fast it would be frozen and we'd have no magnetic field. This gives us constraints on the thermal evolution of Earth's interior. —Preceding unsigned comment added by (talk) 04:52, 22 October 2007 (UTC)

The core of the Earth is still hot because of radioactivity generated by atoms in the core produced by supernovae that exploded before the Earth and the Solar system were first formed. See Age of the Earth and History of Earth. --arkuat (talk) 09:11, 26 June 2008 (UTC)

THIS PAGE NEEDS SCIENTIFIC REVIEW: I am not a geophysicist, but there are assertions here made about the core that are not likely true. It is way too simplistic in its attribution of heat to radioactive decay and ignores other factors. It has no citations. --Jameseavesjo (talk) 14:56, 21 July 2008 (UTC)

You are welcome to post claims to the contrary, with your citations, but the claim that I've made has been uncontroversial in refereed publications for decades. --arkuat (talk) 06:49, 14 November 2008 (UTC)

Um, I agree with Jameseavesjo, there should be a scientific review. No offense, arkuat , but your entry seems a bit to simple. I read the two entries that you sited, Age of the Earth and History of Earth, and neither of them back up the claims you make here. --Anon 23:36, 09 April 2009 (UTC) —Preceding unsigned comment added by (talk)

Yeah, this needs a review badly. I'll not make the edit as I don't have cites handy, but most of the heating in the core is due to accretionary processes from the proto-Earth forming and other masses combining in early planetary history and the descent through the Earth of the dense materials (mostly Iron) that now make up the core. - —Preceding unsigned comment added by (talk) 20:16, 21 August 2009 (UTC)

The sources you're looking for are cited in Geothermal gradient. I'll cite them here when I restore the section on what powers the Earth's core. It's about 20% residual mechanical heat and 80% heat of radioactive decay of uranium, thorium, and potassium-40 according to the sources cited in that article. --arkuat (talk) 01:32, 13 July 2011 (UTC)


I'm curious about the history of scientists discovering that planets have a core, and how they came about to that conclusion --geekyßroad. meow? 05:33, 22 October 2007 (UTC)

This is a hard question to answer, but seismology might give you a start. Basically, sound travels at different speeds, earthquakes cause "sounds" that can be measured all over the planet, and the measurements can be used to deduce things about the core and other layers of the planet based on how fast the sounds traveled through the various layers. If seismology doesn't address your specifically historical concerns, try Age of the Earth and Kelvin's bad guess about it. --arkuat (talk) 06:39, 8 November 2008 (UTC)