Birth of the Moon: a Runaway Nuclear Reaction? 355
An anonymous reader writes "How the Moon arose has long stumped scientists. Now Dutch geophysicists argue that it was created not by a massive collision 4.5 billion years ago, but by a runaway nuclear reaction deep inside the young Earth."
It's a long but interesting article (Score:5, Informative)
I'm on page three. I had to look up a couple of things of wikipedia so far. I hadn't heard the word Petrology [slashdot.org] before; it's the study of rocks.
The term "georeactor" [wikipedia.org] seemed self-explanatory but I looked it up anyway, and was glad I did.
As Mr. Spock would say, "fascinating." My thanks to the story submitter.
Re:Wouldn't there be an empty space? (Score:5, Informative)
Re:Impactors all the way (Score:5, Informative)
> it would have had to be between Venus' and Mars' orbits.
They quote this as a problem?!
The baseline assumption is that the impactor formed in the Earth's trojans, which fixes this "complaint" perfectly. Unlike Jupiter (for instance), the Earth's trojans are not entirely stable, and any large objects placed in it will drift back and forth. This explains a VERY large number of data points:
1) it explains geological makeup perfectly
2) it explains why the impact angle was grazing
3) it explains why the Moon formed so long after the Earth
See: http://en.wikipedia.org/wiki/Giant_impact_hypothesis
Maury
Re:Impactors all the way (Score:4, Informative)
For the first point, it's not all that unlikely. (I don't know of any simulations that show that the impact would destroy the Earth, but you do need a specific range of impact angles to blow material off into orbit.) Remember, there were numerous collisions in that epoch, even between fairly large objects.
As to the second point, I call BS. The moon isn't made of the original material of the impactor. If the authors say it is, they're showing that they don't understand the theory that they're deriding. The Moon is made (principally) of the Earth's mantle. That's why the giant impact theory is so appealing, it explains the compositional similarities.
(That said, I seem to recall simulation work from about a decade ago that indicated that ALL the terrestrial planets had more or less the same composition since the planetesimals would be well-mixed in this region.)
Re:Wouldn't there be an empty space? (Score:5, Informative)
Re:Teach the hypothetical controversy! (Score:5, Informative)
We have group #1 that is going to claim the literalist nonsense. These are the folks that built the creationist fantasy tourist trap where children frolick with dinos in the displays.
We have group #2 that is probably going to take the approach you mentioned to various degrees. Some may say it could have been spontaneously created, but that is no reason to not investigate, we don't have a lot of good information yet. The other end will lean towards the idea that we haven't found any information yet and thus it must be spontaneously created. This is the realm of curable ignorance on one side and pseudoscience nonsense on the other.
Then we will have the final group, that thankfully has gained at least some traction. The group that will say "Sure God created it...and a runaway nuclear reaction or massive impact are two possible methods that the universe played out that caused it to be created...let's go figure it out." Despite the common slashdot groupthink on this subject, there are indeed quite a few very intelligent people that also hold religious beliefs and don't let those religious beliefs muddy up the science. Francis Collins [wikipedia.org] and Ken Miller [wikipedia.org] are two examples that jump to mind. (In fact, if you haven't seen Ken Miller's video on the ID/Dover trial business, it's about 2hrs, but it is an amazing lecture.)
Re:Wouldn't there be an empty space? (Score:4, Informative)
Slashdotted. Mirror here. (Score:3, Informative)
(Or should that be a runaway Slashdot reaction?)
Re:Wouldn't there be an empty space? (Score:4, Informative)
Dude, the European definition of billion is a thousand million, just like in the USA.
Huh? Where?! In German, French, Spanish and Italian, the word "billion" (resp. the words similiar to it) always means 10e12.
Re:Wouldn't there be an empty space? (Score:4, Informative)
Correct, the total volume of the oceans is ~1.3*10^6 km^3 [hypertextbook.com], the volume of the moon is ~2.2*10^10 km^3 [wikipedia.org] so it's not even close.
Not to mention, according to the Giant Impact Hypothesis [wikipedia.org], the iron core of the mars-size body that struck the earth sunk down and was mostly absorbed into the earth's core. The moon has far less iron in its core than most other bodies in the solar system. Consider also that tectonic plates [wikipedia.org] have been moving for billions of years and have formed more than a dozen different "super-continents" [wikipedia.org] over time in various configurations. There's no way the Pacific ocean is a gouge from the moon-making.
Re:Wouldn't there be an empty space? (Score:3, Informative)
Re:Wouldn't there be an empty space? (Score:4, Informative)
I believe the mathematical term for its shape is a "prolate sphereoid."
Oblate spheroid.
Still, both you and the OP have the right idea, the earth would 'quickly' reform into a near spherical shape. It is the largest of the non-gas planets and would probably reform the fastest as opposed to smaller bodies like Mercury, or Pluto.
A good example would be Mimas. It had an impact so massive that the crater looks to be about 20% of the side facing us. I'd wager that an impact like that scaled up and applied to the Earth would quickly be erased (by non environmental factors) on a scale of 1 billion years. Smaller craters would likely be visible for far longer than those that would actually crack the planet to the mantle.
Re:Wouldn't there be an empty space? (Score:5, Informative)
Keep in mind too, that the continental crust material is made up of significantly YOUNGER and lighter rock than the deeper crust. Most of the continents are made of (comparatively) light granite, limestone, sandstone, shale and loose aggregates of all stones. However, the lower crust and the deep ocean crust are made primarily from heavy Basalt.
So the idea that continents formed in the way they did due to the ejection of moon material is incorrect. Not only was the earth likely still a molten ball at that point, but the continents are made from material that did not even exist on earth until well AFTER the earth had solidified.
Re:How Big the Earth, How Thin the Crust (Score:5, Informative)
Re:Whichever God Wins... We Lose (Score:3, Informative)
Yeah, well that's why you were occupied by the Germans during WWII and we weren't. It's damn hard to steer a left-hand-drive tank on the wrong side of the road.
You don't. You steer it wherever you please, and everyone else moves the hell out of your way. :p
Re:Wouldn't there be an empty space? (Score:4, Informative)
... Kilimanjaro ...
That's how most people get it wrong. Kilimanjaro does have glaciers, but it's two degrees south of the equator. It's Mount Kenya (aka Kirinyaga) that has glaciers right on the equator. Kilimanjaro is the more famous of the two, of course, and that's probably why most people guess that it's the answer. If you want to see the glaciers on either of them, you should probably plan your visit for the next decade or so, because the glaciers are shrinking fast. And wouldn't you love to have a photo of yourself standing on a glacier, right on the equator?
It's funny that when asked where the two glaciers on the equator are found, most people don't even think of South America. But the Andes are the only significant mountain range that crosses the equator. (Unless you consider the Rift Valley in Africa to be a mountain range. ;-)