Seriously thoughtful What Heats the Earth's Core?

[Donnageddon]

Most of the residual heat is from the friction of the turtles feet on shell of the turtle below them.

[GeoffC]

geothermal-power-plant-in-cornwall/UK

and one with a Texas reference ....

Interesting topic, Kenny

[TGS]

Originally Posted by Donnageddon

Most of the residual heat is from the friction of the turtles feet on shell of the turtle below them.

But of it's turtles all the way down what does the bottom turtle rest its feet on?

[kennyc]

Originally Posted by TGS

But of it's turtles all the way down what does the bottom turtle rest its feet on?

Stop it!

[ardeegee]

Originally Posted by kennyc

Link is working now. Doesn't seem very relevant as it is related to the Age of the Earth based on temp differential. (but somewhat associated)

It is relevant because the Earth is still far too hot to be billions of years old if there was no other source of heat.

See this page which quotes an article from Scientific American v261 p90 August, 1989, which says, in part:

To derive the earth's age, Thomson calculated how long the earth
required to cool from its primordial to its present state. He conjectured
that the gravitational contraction that formed the earth had generated all
of the earth's heat (except for a small contribution from the sun). Then he
investigated how well the earth conducts heat and how much heat is
necessary for it to melt or to raise its temperature by a certain amount.
He knew that the earth had cooled steadily as energy radiated into the cold
vacuum of space, according to the second law of thermodynamics. Using
Jean-Baptiste-Joseph Fourier's theory of heat conduction, he predicted how
the earth's temperature distribution might have evolved [see "The Fourier
Transform," by Ronalf N. Bracewell; SCIENTIFIC AMERICAN, June]. He
corroborated his calculations by accounting for heat from the sun and the
effects of tidal friction. In time he refined his estimate of geological
history to from 20 to 40 million years.

Thomson's work distressed geologists, who were comfortable with the
idea of unlimited time. They resented this audacious physicist who meddled
in their field, but they could not fashion a counterargument, and they
produced few papers on geochronology.

Thomson's calculation seemed unassailable on the grounds of logic and
physics. His conclusion eventually proved to be inaccurate by a wide
margin. Still, Thrason had instigated a conceptual coup d'etal: qualitative
geochronology was overthrown in favor of quantitative methods. Until the
end of the century, Thomson's estimates were the standards against which
all others were compared.

There was nothing wrong with Kelvin's calculations-- an Earth at this temperature could only be a very few tens of millions of years old if there was no radioactivity (which he couldn't account for because it hadn't been discoverd.) Inversely, without radioactivity, an Earth that IS this age would be far, far colder than it is now.

Note this quote from Chris Peterson, an astronomer at CalTech, responding to some jerk named "Darren Garrison" on a mailing list:

"Nevertheless, the Earth would have long ago cooled to a solid interior were
it not for the continued production of interior heat from radioactive decay.
There is more to it than simply the radiative loss of the heat of formation.
This is also a factor in the cooling rate of smaller bodies that are
responsible for iron meteorites. That is, even small bodies cooled slower
than might otherwise be expected, because of active internal heating from
radioactive decay (something that I think was touched upon earlier)."

(From the metlist archives, which are publicly available.)

[TGS]

Originally Posted by kennyc

Stop it!

What, me! What did I do - I'm just askin'

[kennyc]

Originally Posted by ardeegee

It is relevant because the Earth is still far too hot to be billions of years old if there was no other source of heat.

My point is that this is not about the age of the Earth, it's about why the core is hot so as I said, somewhat relevant, but not directly.


Seems the consensus is that most (90+%) is due to radioactivity with a bit due to friction and a bit left over from the formation.

Would be very cool (pun intended) if we could somehow capture this heat and use it for your energy needs -- certainly lots of work going on already....

[kennyc]

Originally Posted by TGS

What, me! What did I do - I'm just askin'

You're encouraging the riff-raff in a thread marked "serious" -- yea I know I coulda started it out more serious....

All is good.

[ardeegee]

Originally Posted by kennyc

My point is that this is not about the age of the Earth, it's about why the core is hot so as I said, somewhat relevant, but not directly.

It is absolutely directly relevant. Absolutely. The core is hot because it is radioactive. If the core was not radioactive, the core would not be hot. (Okay, you still wouldn't want to sit on it-- but not nearly as hot as it is now.) The fact that the calculations were done in an attempt to determine the age of the Earth is an irrelevant side issue-- the math still stands. If there was no radioactivity, the Earth's core would be solid and "cold" by now.

[kennyc]

Originally Posted by ardeegee

It is absolutely directly relevant. Absolutely. The core is hot because it is radioactive. If the core was not radioactive, the core would not be hot. (Okay, you still wouldn't want to sit on it-- but not nearly as hot as it is now.) The fact that the calculations were done in an attempt to determine the age of the Earth is an irrelevant side issue-- the math still stands. If there was no radioactivity, the Earth's core would be solid and "cold" by now.

Forget it. As I said. It's a side topic. It's actually the opposite of the topic at hand, yes it plays into it because it is the converse - if you know the age of the Earth and how hot it was and how long it would take to cool you can determine that it should have cooled already but it doesn't answer the question as stated.

[ardeegee]

Originally Posted by kennyc

but it doesn't answer the question as stated.

Then I honestly don't understand what the question is-- because that is the answer to "what heats the Earth's core."

""We don't think this original heat is a major part of the Earth's heat, though," Marone says. It only contributes 5 to 10 percent of the total, "about the same amount as gravitational heat.""

"For all this, however, Marone says, the vast majority of the heat in Earth's interior—up to 90 percent—is fueled by the decaying of radioactive isotopes like Potassium 40, Uranium 238, 235, and Thorium 232 contained within the mantle. These isotopes radiate heat as they shed excess energy and move toward stability. "The amount of heat caused by this radiation is almost the same as the total heat measured emanating from the Earth." "

From:

http://www.physorg.com/news62952904.html

[kennyc]

Quit being a ditz Ardeegee.

What heats the Earth's core is a different question than Is the Earth's core still cooling off.

I explained this precisely to you above. Assuming you know the initial conditions you can make a case for the core not being hot from those initial conditions. Which is somewhat related to the initial link you posted about the age of the Earth but is not directly related to WHAT HEATS THE EARTHS CORE.

I know you'll come back again as say you're right, cause you always have to be right, but you are not in this point.



In science it is important to be precise.

[kennyc]

Originally Posted by ardeegee

Then I honestly don't understand what the question is-- because that is the answer to "what heats the Earth's core."

""We don't think this original heat is a major part of the Earth's heat, though," Marone says. It only contributes 5 to 10 percent of the total, "about the same amount as gravitational heat.""

"For all this, however, Marone says, the vast majority of the heat in Earth's interior—up to 90 percent—is fueled by the decaying of radioactive isotopes like Potassium 40, Uranium 238, 235, and Thorium 232 contained within the mantle. These isotopes radiate heat as they shed excess energy and move toward stability. "The amount of heat caused by this radiation is almost the same as the total heat measured emanating from the Earth." "

From:

http://www.physorg.com/news62952904.html

A completely different link and topic from what you posted initially. More along the lines of what I initially posted. Oh, imagine that, it IS the link I posted.

[Salgueiros]

Originally Posted by kennyc

Quit being a ditz Ardeegee.

What heats the Earth's core is a different question than Is the Earth's core still cooling off.

I explained this precisely to you above. Assuming you know the initial conditions you can make a case for the core not being hot from those initial conditions. Which is somewhat related to the initial link you posted about the age of the Earth but is not directly related to WHAT HEATS THE EARTHS CORE.

I know you'll come back again as say you're right, cause you always have to be right, but you are not in this point.



In science it is important to be precise.

Ok... now i am a bit confused too. I think we can say that what heats the Earth core (as far as our knowledge goes now) is (mainly) the radioactive decay of radioactive isotopes like Potassium 40, Uranium 238, 235, and Thorium 232. This does not answer your question?

[kennyc]

Originally Posted by Salgueiros

Ok... now i am a bit confused too. I think we can say that what heats the Earth core (as far as our knowledge goes now) is (mainly) the radioactive decay of radioactive isotopes like Potassium 40, Uranium 238, 235, and Thorium 232. This does not answer your question?

Yes that is correct. But my point is that has virtually nothing to do (other than it was mentioned in passing) with the link that Ardeegee posted about Lord Kelvin, creationism and the age of the Earth.

If you calculate the age of the Earth based on it's temperature, that answer will be wrong because it doesn't take into account the other things that might "Cause the Heat of the Earth's Core"

Now, if you know the age of the Earth and know the initial temperature and the rate of cooling you can calculate that the temperature has to do with something other than the initial formation/temperature. But it still doesn't answer the question.

It is the knowledge of radioactivity, it's density and activity that can be used to calculate a heating effect and in combination with the initial conditions and other factors - friction and possibly others - that a reasonable explanation of "What Heats the Earth's Core" can be hypothesized.