Freethought & Rationalism Archive

Answerer · 03-31-2003, 10:52 PM

Hi guys, in regard to the recent movie, "the core", it had been claimed that the 'only' source of Earth's magnetic field is the spinning of the Earth's inner core. But seriously, for a long time, I had thought that Earth's magnetic field is due to a total contribution of moving magma, spinning outer and inner core. So guys, is the movie right or me?

Nowhere357 · 03-31-2003, 11:06 PM

Quote:

Originally posted by Answerer
Hi guys, in regard to the recent movie, "the core", it had been claimed that the 'only' source of Earth's magnetic field is the spinning of the Earth's inner core. But seriously, for a long time, I had thought that Earth's magnetic field is due to a total contribution of moving magma, spinning outer and inner core. So guys, is the movie right or me?

This tells me the movie is 90% correct, which is pretty good for a movie, I think.

Apparently, you are over 90% correct, but not quite 100%, because the earth's crust and even off-planet sources contribute to the earth's magnetic field. So I would say that you were more right than the movie!

Jesse · 03-31-2003, 11:09 PM

The plot of "The Core" was based on a real theory, the "nuclear planet" theory, but this is not the mainstream view of where the magnetic field comes from (although the mainstream view still seems to say that it's just the central iron-nickel core that produces the magnetic field, not the other layers). You can read about this theory here:

http://www.discover.com/aug_02/featplanet.html

Quote:

Earth, says geophysicist J. Marvin Herndon, is a gigantic natural nuclear power plant. We live on its thick shield, while 4,000 miles below our feet a five-mile-wide ball of uranium burns, churns, and reacts, creating the planet's magnetic field as well as the heat that powers volcanoes and continental-plate movements. Herndon's theory boldly contradicts the view that has dominated geophysics since the 1940s: that Earth's inner core is a huge ball of partially crystallized iron and nickel, slowly cooling and growing as it surrenders heat into a fluid core. Radioactivity, in this model, is just a supplementary heat source, with widely dispersed isotopes decaying on their own, not concentrated.

...

Herndon recently put forth what he sees as the most compelling argument for his theory in a paper published in the Proceedings of the National Academy of Sciences. Using computer simulations that Hollenbach helped him run at Oak Ridge, Herndon showed how software that tracks fuel usage at nuclear power plants indicates that a "planetary-scale geo-reactor" could indeed have been blazing away for 4.5 billion years, the widely accepted estimate of Earth's age, at heat levels that match Earth's actual output of roughly four terawatts. Moreover, such a reactor would vary in intensity� sometimes strong, sometimes weak, sometimes shutting down altogether� which could explain why Earth's magnetic field has periodically waxed, waned, and reversed through the millennia.

Herndon contends that not only does Earth probably have a reactor boiling at its core but so do Jupiter, Saturn, and Neptune. Natural nuclear reactors could explain a lot of mysteries, from how stars ignite to the nature of dark matter, the mysterious, elusive stuff that astronomers say is 10 times more common than the ordinary matter they can observe. Indeed, Herndon's theory, if correct, would require nothing less than revamping our view of how much of the material universe operates.

"It's an idea with a lot of explanatory power," he says.

Perhaps.

In the geophysical community, Herndon is stranded on his own tectonic plate. According to the dominant core theory, the magnetic field is powered by the dynamolike vortices of molten iron and nickel swirling around a solid iron-nickel ball, not� as Herndon contends� by flows of charged particles surrounding a blazing nuclear reactor. While Herndon has pushed the premise for 11 years and published papers in impressive journals, including the Proceedings of the Royal Society of London, his work is seldom cited by other geophysicists. His theory is not so much refuted as ignored.

"The data just does not demand it," argues Bruce Buffett of the University of British Columbia, who says he has read one of Herndon's early papers. You can run numerical simulations of convection with the traditional models, he says, and get the kind of magnetic-field behavior that shows up in the geologic record. "What he is doing sounds like a line of reasoning, not a proof."

Still, Herndon is not without prominent champions. "Many paradigms that we follow today don't have as much backing as he has put together for this," says the Carnegie Institution's Yoder. "He has a fresh new idea, and he has fit it all together extremely well. We need to consider what he has to say."

Jesse · 04-01-2003, 09:08 PM

Whoops, I made a mistake...in my last post I said:

Quote:

but this is not the mainstream view of where the magnetic field comes from (although the mainstream view still seems to say that it's just the central iron-nickel core that produces the magnetic field, not the other layers)

Now I see that I misread the article I quoted above, the mainstream view does say the outer core is the main contributer to the magnetic field, like you guys said. But in Herndon's alternate theory it would mainly be that central core of uranium and plutonium that creates it.

Answerer · 04-01-2003, 09:15 PM

Thanks for the site anyway, it does help.

Shake · 04-07-2003, 11:06 AM

IIRC, uranium is widely distributed around the surface (at least) of the earth.

Also, I recall reading some sci-fi story with references to iron. The point, I believe, was that in the fusion furnaces of stars, iron is the eventual, final product of said fusion. Initially, hydrogen is fused to make helium. Eventually, all the hydrogen is used up and there is mainly just helium left (perhaps a very small amount of some heavier elements). The process continues like this, but ends at iron, due to something about its chemical nature that prevents fusion from making anything heavier (than wouldn't just decay anyways). Towards the end of a stars' life, the core is more and more iron than anything else, and this end product of the fusion process helps fuel the stars' eventual collapse and nova (supernovae in more massive stars).

So what about planets? What happens when the fissible uranium is used up? Actually, if there's such a concentration of uranium, what keeps the planet from blowing apart? I'm sorry. I like to be open to new paradigms, but this one just doesn't seem plausible.

Walross · 04-07-2003, 06:42 PM

Here's what Phil Plait of badastronomy.com had to say about The Core. I love his reviews, they're great for a nitpicker like me!

Walross

Jesse · 04-07-2003, 08:23 PM

Shake:
Also, I recall reading some sci-fi story with references to iron. The point, I believe, was that in the fusion furnaces of stars, iron is the eventual, final product of said fusion. Initially, hydrogen is fused to make helium. Eventually, all the hydrogen is used up and there is mainly just helium left (perhaps a very small amount of some heavier elements). The process continues like this, but ends at iron, due to something about its chemical nature that prevents fusion from making anything heavier (than wouldn't just decay anyways). Towards the end of a stars' life, the core is more and more iron than anything else, and this end product of the fusion process helps fuel the stars' eventual collapse and nova (supernovae in more massive stars).

Well, presumably at least some supernovae must produce significant amounts of elements heavier than iron, otherwise we wouldn't find these elements in our own solar system.

Shake:
So what about planets? What happens when the fissible uranium is used up? Actually, if there's such a concentration of uranium, what keeps the planet from blowing apart? I'm sorry. I like to be open to new paradigms, but this one just doesn't seem plausible.

The Discover article says that Herndon has published papers on his theory in a number of respectable (and I assume peer-reviewed) journals, like the Proceedings of the National Academy of Sciences and Proceedings of the Royal Society of London, so even if his theory is flawed I doubt the flaws are obvious ones like failing to realize that such a ball of uranium would just explode (maybe the reason it doesn't has to do with the pressure at the center of the earth). The article also mentions that he has some "prominent champions" such as "Hatten Yoder, director emeritus of the Geophysical Laboratory of the Carnegie Institution of Washington" (although from his quotes I think Yoder is not necessarily advocating the theory himself, just saying it's worthy of serious consideration by researchers).

As for what would happen once the fissible uranium is used up, this article says:

Quote:

His latest study, published in the March 18 issue of the Proceedings of the National Academy of Science, is based on a computer simulation predicting how such a reactor would behave over billions of years. The simulation, conducted by Oak Ridge National Laboratory, yielded data on the levels of different helium isotopes that should be given off by such a reactor. Those hypothetical levels closely matched the actual levels found in rock being thrust up from Earth�s interior.

The simulation also predicted that the reactor�s uranium fuel should run out about 4.5 billion to 5.5 billion years after its startup. That could be bad news, since scientists believe that Earth was formed about 4.5 billion years ago. The results led Herndon to conclude that Earth�s core reactor has somewhere between 100 years and 1 billion years left.

If you accept Herndon�s theory, it would then just be a matter of time before Earth�s magnetic field dissipates.

Jesse · 04-07-2003, 09:53 PM

The badastronomy review of "The Core" which Walross mentioned has some critiques of Herndon's theory which are not discussed in the Discover article:

Quote:

Okay, another comment. For some reason, Corey Powell of Discover Magazine gave the movie a lot more credit than I think it should get in his review of it. That's okay; people are allowed to disagree (and his review of "Signs" was great). The movie was fun, but the science was wrong.

Corey also mentions a guy by the name of J. Marvin Herndon, who says that the core of the Earth is a giant nuclear reactor. Let's just say that this theory may not be held in much regard by most geologists. Actually, I'll say more than that: Judging from his replies to some letters to the editor, the guy is way, way off base. He says that it's possible that nuclear fusion in the cores of stars needs nuclear fission to work. That's really just silly. First, he mentions scientific papers that are 40 years old or more saying there were problems understanding how stars can start fusion. But there has been considerable work done since then, and the what was a problem in the 1960s isn't such a problem anymore.

Also, uranium and other fissile materials are created when stars explode, so the first generation of stars at the very least didn't have fission to help their fusion. He tries to circumvent this argument by saying, basically, the Universe is a mysterious place, but that's just hand waving. I could just as easily say I might turn into antimatter tomorrow, and if you object, I could say the same thing he did. It's a cop-out for someone who has what is really just a silly theory.

My first thought about having the core of the Earth be a nuclear reactor was, "where are the neutrinos?". They are a natural byproduct of fission, and if the Earth were such a big reactor, as he claims, they should be pouring out of the core. This was asked of him in those letters to the editor, and he again cops out and says we wouldn't detect them due to the noise from the Sun and reactors on the Earth. That's silly again; we know just how many neutrinos come from the Sun, and a source the size of the Earth just a few thousand kilometers down would be pretty obvious.

I checked his website, and his main page has lots of errors as well (he says Jupiter's heat comes from nuclear energy; the mainstream thought that it comes from gravitational contraction must be wrong because "Jupiter is 98% hydrogen and helium, both of which are extremely efficient heat transfer media". Um, maybe at room temperature as gases, but what about under the tremendous pressure that exists deep in Jupiter's depths?). I often wonder why mainstream sources like Discover and others give these people such a pulpit without giving mainstream scientists a real chance to air out these theories. It's aggravating.

It's possible Herndon's claims about the earth could be right while his more extravagent claims about star formation and other planets are wrong, but the issue of the neutrinos does sound like it could be a big problem for his theory.

03-31-2003, 10:52 PM	#1
Answerer Veteran Member Join Date: Feb 2002 Location: Singapore Posts: 3,956	What is responsible for Earth's magnetic field? Hi guys, in regard to the recent movie, "the core", it had been claimed that the 'only' source of Earth's magnetic field is the spinning of the Earth's inner core. But seriously, for a long time, I had thought that Earth's magnetic field is due to a total contribution of moving magma, spinning outer and inner core. So guys, is the movie right or me?

Thread Tools	Search this Thread
Show Printable Version	Search this Thread: Advanced Search

04-01-2003, 09:15 PM	#5
Answerer Veteran Member Join Date: Feb 2002 Location: Singapore Posts: 3,956	Thanks for the site anyway, it does help.

04-07-2003, 11:06 AM	#6
Shake Contributor Join Date: Jan 2001 Location: Folding@Home in upstate NY Posts: 14,394	IIRC, uranium is widely distributed around the surface (at least) of the earth. Also, I recall reading some sci-fi story with references to iron. The point, I believe, was that in the fusion furnaces of stars, iron is the eventual, final product of said fusion. Initially, hydrogen is fused to make helium. Eventually, all the hydrogen is used up and there is mainly just helium left (perhaps a very small amount of some heavier elements). The process continues like this, but ends at iron, due to something about its chemical nature that prevents fusion from making anything heavier (than wouldn't just decay anyways). Towards the end of a stars' life, the core is more and more iron than anything else, and this end product of the fusion process helps fuel the stars' eventual collapse and nova (supernovae in more massive stars). So what about planets? What happens when the fissible uranium is used up? Actually, if there's such a concentration of uranium, what keeps the planet from blowing apart? I'm sorry. I like to be open to new paradigms, but this one just doesn't seem plausible.

04-07-2003, 06:42 PM	#7
Walross Veteran Member Join Date: Aug 2000 Location: Edmonton, AB, Canada Posts: 1,569	Here's what Phil Plait of badastronomy.com had to say about The Core. I love his reviews, they're great for a nitpicker like me! Walross

Freethought & Rationalism Archive

The archives are read only.