The nuclear earth

[lazarus]

I lost track of the thread, because I didn't feel like keeping up with the stupid argument, but someone in GD actually claimed that the earth's core is a giant nuclear reactor.

Sigh.

[realisticphish]

1. hahaha

the sad thing is, I'm really not surprised. They see the sun. It's hot. Why? Fusion. The Earth. The core is hot. Why?

And rather they try to find the actual answer, they assume.

[lazarus]

2. Once I called the poster out on it

they fell back to spontaneous fission, like that has anything to do with anything. The lack of basic science knowledge on this board is pathetic and troubling.

On edit:

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=389x7839893

I'm not wading back into that crap, I don't even know if the poster responded to my last post. That sort of stupidity makes my head hurt.

[realisticphish]

3. their claims

(there were two) was that the radioactive decay was a reaction, therefore the core was a nuclear reactor.

I was going to ask at what point the earth went into critical mass, but I didn't want to wade in, either

[TZ]

4. Well the sun is apparantly a big electric light bulb.

So it all makes sense. :eyes:

[meeshrox]

5. Not suprised...

Just wandered into the woo forum to see what the hype is about...never.going.back.

I felt it would be unfair to attack, I mean post, in their forum with facts. :evilgrin:

UGH! :banghead: Shit just gets me so irritated!

[HiFructosePronSyrup]

6. Well... isn't it?

OK, not the core technically. But the molten mantle and all it's various dynamics (volcanism, plate tectonics, etc.) rely on nuclear fission of radioactive isotopes.

[meeshrox]

7. Not fission, but decay...you're kinda right...

:hi:

[HiFructosePronSyrup]

8. Um, isn't radioactive decay a form of fission?

⁴⁰K --> ⁴⁰Ar + e^-?

or the decay chain of thorium? ²³²Th --->--->----> ²⁰⁸Pb + ne^- + nHe²⁺

Is this some sort of semantic argument?

[muriel_volestrangler]

9. Semantics can be important

Here's a government site defining decay and fission, for instance:

decay (radioactive): The change of one radioactive nuclide into a different nuclide by the spontaneous emission of radiation such as alpha, beta, or gamma rays, or by electron capture. The end product is a less energetic, more stable nucleus. Each decay process has a definite half-life.
...
fission: The splitting of a heavy nucleus into two roughly equal parts (which are nuclei of lower-mass elements), accompanied by the release of a relatively large amount of energy in the form of kinetic energy of the two parts and in the form of emission of neutrons and gamma rays.

http://www.lbl.gov/abc/wallchart/glossary/glossary.html

And that point about the half-life is important - whatever you do to the atoms, the half life of an isotope remains the same; but the rate of fission in a nuclear reactor is affected by the other stuff in there, the surface area to volume ratio, any input of neutrons and so on - rather like a chemical reactor. It is literally reacting to the conditions, whereas decay is just inevitable.

[realisticphish]

10. yeah

but I think the overall point is that the nuclear decay in the earth is not the equivalent of a nuclear reactor in a power plant

[HiFructosePronSyrup]

11. I don't think anybody's saying it's the equivalent.

:shrug:

[realisticphish]

12. "The Earth's core is a giant nuclear reactor"

^ (from the thread)

IMHO, that implies critical mass, etc.

As you said, though, much of this discussion is semantics

[HiFructosePronSyrup]

13. Do we know if any of it's self sustaining or not?

Like at Oklo?

[realisticphish]

14. i honestly don't know

but I did find this article, which has an interesting overview:
http://geology.about.com/od/wildgeotheories/a/nuclearcore.htm

[meeshrox]

15. Not trying to get into semantics...

the two processes are different.

Fission requires an activation, the bombardment of a nucleus to begin the chain reaction.
Decay is a random and sometimes slow process (depending on the element).

The earth is hot from the leftover heat from it's formation and from radioactive decay of elements in the middle and outer core. We would be tectonically inactive, like Mars, quicker if not for the radioactive decay. Volcanism is not an "efficient" way to expel extra heat, lucky for us. We are not creating more heat in the interior (through fission).

[Silent3]

16. I remember that Lord Kelvin's estimate of the age of the Earth...

...was thrown off by the fact that neither he, nor any of the other scientists during his time, new about nuclear decay and the heat it would produce.

His estimate, however, was 20 million years old.... only off by a factor of 225! I've often wondered if there weren't other errors in his calculations, otherwise that's an awful lot of heat from radioactive decay.