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I have always heard that the Earth, due to its structure, cannot explode. Now, I'm quite fascinated by astronomy physics but I admit I only hold some more than basic knowledge.

In any case, even though I have interiorized this concept, I have no basis to prove it. If you search on the internet, you get both theories (No it won't vs yes it will), so you understand that even if one is the current accepted theory, I'm not sure I know why it is the case.

Considering this, what concrete reasons can we bring forward in its favour? And why?

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The earth won't explode because it's not filled with explosives. It's also too small to collapse and go supernova. I'm curious where on the internet you found theories that the earth will explode... –  Dmitry Brant Nov 28 '12 at 14:25
    
@DmitryBrant There's this page. Please note that I'm not necessarily believing it, since I actually tend towards the opposite version. Through my question I just want to know concrete reasons why it cannot explode because I thought that if I had to face this discussion now, I wouldn't have any fact to bring forward. –  Alenanno Nov 28 '12 at 14:38
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@DmitryBrant You wanted to know whether there was someone stating that, and I provided it. (I want to make it clear again, I don't believe in it.) This site is meant to provide knowledge, my question is seeking that. –  Alenanno Nov 28 '12 at 14:58
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@DmitryBrant The scientific community certainly doesn't have to disprove every nut job out there, Physics SE however is a very good place for people to ask such questions. You seem to have a great answer to the question, please post it, and soon enough people googling for "exploding earth" will be reading your scientific answer instead of the crap Alenanno linked to (which currently shows up very near the top of search results). –  Yannis Nov 28 '12 at 14:59
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Comments cleaned up. A user's reasons for posting are their own and not subject to moderation except in narrowly defined circumstances. –  dmckee Nov 28 '12 at 16:12
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2 Answers

up vote 8 down vote accepted

The page to which you linked suggests that the Earth will explode due to global warming. What about Venus? Not only is it closer to the sun, but its greenhouse effect is an order of magnitude stronger than ours. Yet Venus has not exploded.

The page also suggests that the Earth's core is some kind of nuclear reactor. It can't be a fusion reactor because the Earth is not massive enough to start fusing hydrogen like our Sun does. There is some fission happening in the Earth's core, but it's decreasing as the radioactive elements are depleted, and the planet is generally cooling as time progresses.

The heat energy contribution from the sun has virtually no effect on the internal temperature of the planet. And even if some of the fissionable material in the earth's core somehow condenses into a critical mass, the explosion would probably not be felt on the planet's surface. It would take a ridiculous amount of fissionable material to literally "blow apart" the planet; much more than actually exists inside of it.

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Thanks for answering. I have two additional questions if you don't mind (really short): 1. So, considering the mass is enough, would being close to the sun/having a greenhouse effect influence the fact that a planet might or might not explode? 2. The planet is cooling? I know it's supposed to be something really slow... But is that considered good or bad news? –  Alenanno Nov 28 '12 at 16:28
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1) No planet-sized object will ever explode for any reason (unless it's made of solid uranium), no matter how close it is to a star. 2) The rate of cooling of the planet's interior has very little effect on life on the planet's surface. Life on the surface, on the other hand, is influenced by proximity to the sun. –  Dmitry Brant Nov 28 '12 at 16:49
    
Thanks for clarifying, Dmitry. –  Alenanno Nov 28 '12 at 16:50
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Aside from the fact that the Earth's core isn't a fission reactor...

and aside from that fact that increasing temperature of a fission reactor will decrease its power, as opposed to increasing it as implied by the link, "Overheating of the fission heated planetary interior"...

and aside from the fact that more volcanic activity would eventually cool the Earth's core as opposed to heating it (possibly implied by the link, hard to be sure)...

What I want to know is how global warming has anything to do with the temperature of the core of the Earth on these scales. Let's look at temperature and then heat capacity:

Temperature: The IPCC scenarios see surface temperature rising by maybe $12 K$ at the most. The temperature of the center of the Earth is around $7500 K$. Even if the change from AWG propagated instantly, at most it would increase the temperature of the center of the Earth by those 12 degrees. Not to mention that higher temperature tends to increase heat transfer coefficients as opposed to decrease them. Even in the worst case scenario, what effect should increasing the center of the Earth to $7512 K$ actually have?

  • Considering that that temperature has been steadily declining for billions of years
  • Considering that it would have less nuclear fuel today than at any time in the past

We probably don't have anything to worry about.

Heat capacity: I can do a very very general ballpark estimate of how long it will take a rock the size of Earth to warm up 12 degrees due to an increase in insulation of about 4 W/m^2, which is what we get from global warming. I get around 250 million years. Everything in the link argues with data from 1970 to today. While many of the link's claims can be called junk science, this flaw is so horrendously bad that I wouldn't even call it that. I would say it's more of a flagrant rejection of reality.

Let's just assume, for the sake of argument, that volcanic activity and earthquake strength actually has increased in the last 100 years. The link offers no plausible chain of reasoning to explain it.

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BTW, the possibility that there was a geo-recator at the core was taken seriously for a while in trying to account for the full terrestrial heat balance, but geo-neutrino data from KamLAND and Borexino seem to conclusively rule out that scenario. –  dmckee Nov 28 '12 at 16:14
    
@dmckee Right. I'm sure you're aware that there have been natural fission reactors in the Earth's crust, but those wouldn't be any use for building a scenario where the Earth explodes either. Radioactive decay is certain to contribute to the heat content, and maybe it would be possible that sustained fission reactions happened deep in the interior long ago, since it would be difficult to falsify with any present measurement. –  AlanSE Nov 28 '12 at 16:21
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