Talk:Giant impact hypothesis

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Contents

[edit] Secondary core

In my opinion "giant impact theory" has too many variables.The Moons origin can be explained by more subtle means.The Moon was born from a secondary core. The force of the young sun erupting on the embryonic Earth core would produce a bow shock wave and wake. In the wake of the Earth a secondary core would form. The position of the Lunar core at birth was dictated, it was naturally placed amoungst the lighter elements in the protoplanetary disc.When the Sun again became subdued, the Earth and Moon orbited the sun as separate planets .As the Earth grew at a faster rate than the Moon,it was forced to migrate away from the sun and gained on the Moon.,This caused a collision of forces on both planets the resulting clash of forces created the tilt of axis we see today,this clash of forces is also the trigger mechanism for the lunar orbit. — paulhesq

That is a modification the rejected theory of simultaneous formation, with a touch of planetary migration -- neither of which is supported by evidence. ....................................... If you accept as a power law that dense material takes up positon in eye of the main disc and lighter elements at the outer, then disloged heavy molten core material thrown out amongst the lighter material would be swept along by the disc and spiral back 'toward' the sun. Heavy molten material woud also have increased gravatational force on the lighter elements and so the planet would form more quickly. User:paulhesq

Of the three original theories of formation: (1) capture (2) spin-off and (3) simultaneous formation in the neighborhood, it has the same issues that cause both (1) 'and' (3) to be rejected. The Moon in this "secondary core" theory shouldn't be less dense than Mars, and should have comparable water and other volatile content. Furthermore, the intricate dynamics of planetary migration affect the larger masses of the OUTER solar system and involve transfers of angular momentum between scattered objects, Saturn, Uranus and Neptune. There is no equivalent mechanism available for Venus and Earth that would move Earth so far as to go to a position where an object as dense as the Moon would have coalesced on its own. And again, then the same impossibility of explaining current Earth-Moon system angular momentum that rejects (1) rejects "secondary core"--Sturmde 22:39, 22 October 2005 (UTC)

[edit] Single continent

I have very little knowledge of this subject, but would this be the reason there was one large continent? Is that what is meant by saying that the continents are made of a different type of rock than the ocean floors? the continents are the leftovers of the impact point? - Omegatron 18:53, Jan 9, 2005 (UTC)

There is no known relationship between there having been one single continent and this impact. Actually, from the composition of meteorites it appears that Earth should have a lot more of the less dense rocks which make up the continents. The Moon has a lot more of such lighter rocks than it should have. From your question about continents being leftovers of the impact point, perhaps you're thinking that the Earth was mostly nickel-iron and the impactor was made of lighter materials. We don't know, but it seems quite unlikely for Earth to have not had many of the less dense materials. Also, with such an impact, it seems unlikely that the impact site would have left much of a trace. In addition, continents are not a single piece of rock, and there have been many slow additions to continents detected. Start with craton for more info. (SEWilco 22:40, 30 May 2005 (UTC))
There was speculation at one point (1960s?) that the Pacific ocean basin could be a scar left over from the formation of the Moon. This was before plate tectonics was understood.
Also, Pangea coallesced from smaller continents, which were formed in the breakup of another mega-continent called Rodinia about 750 Ma (million years ago). Rodinia in turn had formed from the fragments of an even earlier supercontinent, and so on. However, the further back you go, the less continent there is, because while oceanic crust gets recycled, continental crust keeps growing. (Volcanic islands plastered onto the margins of continents add to their bulk.) It's speculated that very early in the Earth's history there were no continents at all; it was all oceanic crust.
If the Earth had kept all the lighter rocks that ended up in the Moon, we might have a lot more continent today. That could be a bad thing: without as much room for the plates to move around, continental drift could've stopped a long time ago, and the Earth might be much more like Venus. kwami 07:42, 2005 May 31 (UTC)

[edit] Discuss article, not theory

This page is for discussion of the Wikipedia article on the giant impact theory. It is not for discussion of the theory itself. --P3d0 02:56, Jan 28, 2005 (UTC)
Is there some reason Omegatron shouldn't be allowed to call attention to questions they feel are raised by and could be addressed in the article itself? --John Kenneth Fisher 03:00, May 30, 2005 (UTC)
I hope I didn't give that impression. --P3d0 02:29, Jun 1, 2005 (UTC)
My apologies if I misread that then. :-) --John Kenneth Fisher 22:06, July 16, 2005 (UTC)

Probability. The trigger method for the birth of our moon is more likely to be action of the young Sun rather than some stray Mars sized planet impacting the Earth at a certain time, at a certain angle, at a certain speed. User:paulhesq

Read Delano's Discovery , search Wikipedia for a new look at the Earth-moon discussion. [John Delano Dec, 18, 2006]

[edit] References needed

This article is too good not to have any external links or references, We need the references that are referred to in the text, for a start. --Wetman 02:30, 28 Jan 2005 (UTC)

[edit] Animation direction

Doesn't the animation show the moon orbiring the earth in the wrong direction? I am assuming that we are looking "down" on the north pole as most literature show.

Common people, if you're going to put forth serious arguments, then you have to present the current facts correct. If Theia started at L4, then the animation is showing the Moon orbiting the Earth in the wrong direction!

  • Then we are looking up. ;)

Sure, we're looking at the south pole - but the Lagrange points are mislabeled. L4 is ahead, and L5 behind the main body. This has gone unfixed long enough - people have been commenting on this for a year! I'm going to relabel it. kwami 18:43, 30 September 2005 (UTC)

Actually, I asked Muriel (the artist) to relabel it. Also changed the text to say that L4 & L5 are mislabeled, rather than saying that the moon is going in the wrong direction. Most people could care less about which Lagrange point is which (who couldn't make that mistake?), but having the moon going in the wrong direction makes us sound like dimwits, even if they're the same thing. kwami 19:17, 30 September 2005 (UTC)
I think that the two figures are highly redundant, and suggest removing the animation. Also, the theory that the Moon formed at one of the Lagrange points is VERY new (published this year or last). While this hypothesis is somewhat attractive, the theory is in its infancy, and I find the overemphasis given to it in this article somewhat disturbing. Lunokhod 09:47, 15 November 2006 (UTC)

[edit] Impactor tidal forces

how can a body orbit the earth and hit it "with a suitably low velocity" without being torn apart by tidal forces?

Obviously that depends on what "suitably low" means. --P3d0 18:53, July 15, 2005 (UTC)

[edit] Date of impact 4.533Ga

The author of the article might want to incorporate this reference.

Conclusions: Luna is less than 65% Theia; impact occurred 4.533Ga.

Evolution of Planetary Cores and the Earth-Moon System from Nb/Ta Systematics Carsten Münker, Jörg A. Pfänder, Stefan Weyer, Anette Büchl, Thorsten Kleine, and Klaus Mezger Science 4 July 2003; 301: 84-87 [DOI: 10.1126/science.1084662]

Abstract It has been assumed that Nb and Ta are not fractionated during differentiation processes on terrestrial planets and that both elements are lithophile. High-precision measurements of Nb/Ta and Zr/Hf reveal that Nb is moderately siderophile at high pressures. Nb/Ta values in the bulk silicate Earth (14.0 ± 0.3) and the Moon (17.0 ± 0.8) are below the chondritic ratio of 19.9 ± 0.6, in contrast to Mars and asteroids. The lunar Nb/Ta constrains the mass fraction of impactor material in the Moon to less than 65%. Moreover, the Moon-forming impact can be linked in time with the final core-mantle equilibration on Earth 4.533 billion years ago. kwami

The anonymous contributor of the above did not explain that the ratio suggests that both the Earth and the Moon were subjected to unusually high pressures. Under this pressure, some Nb combined with mantle materials which it otherwise does not react with. The Moon's ratio being higher than Earth also suggests that its material was subjected to somewhat less pressure. (SEWilco 06:57, 1 Jun 2005 (UTC))
Sorry for being anonymous. (I only wrote the first two lines, of course.) kwami 2005 July 7 19:08 (UTC)

[edit] Why subtle growth?

Why formulate a subtle process of growth to explain the Lunar birth?

The accretion of planets is simply a process of growth, all such processes are subject to abnormality. Sometimes the trigger event for change is a monumental , sometimes change is triggerd by more subtle means. It is more probable that the instability of a young Sun triggerd the birth of our Moon. Co-accretion theorys have been dismissed in the past becaus they have failed to answer the density question. If all science had was a tadpole, might it be mistaken for fish fry? It would take a great deal of imagination to envisage the adult frog and its various stages of growth. Why does the Moon have to be born orbiting the Earth? If the young Sun suddenly erupted on the Earths magma core, a bow shock wave and wake would form. In the wake,in the shadow of the Earth a secondary core would form..... Primary secondary shadow accretion. paul.

I suppose compared to solar energies, Giant Impact could be called subtle. Is there an article about shadow accretion? (SEWilco 05:13, 1 Jun 2005 (UTC))
Any material in the shadow would quickly drift out of shadow (by 'quickly' I mean in a matter of hours), because it's in a different orbit around the sun. Different material would be in the wake at different times. And even if it were to form a second core, it would still have to be captured into Earth orbit, and the angular momentum's all wrong for that. Lots and lots of speculation like this has gone into the moon, but the physics just doesn't work for most of it. kwami 2005 July 7 19:16 (UTC)

[edit] Shadow Accretion

Displacement of core material may be observed around Beta Pictoris.

What does this mean? Any links or refs? kwami 2005 July 7 19:18 (UTC)

[edit] corrected image

Since I haven't heard back from the author, I went ahead and swapped the Lagrange points in the image, so they're labeled correctly for viewing the south pole. kwami 07:26, 28 November 2005 (UTC)

[edit] Getting the moon into a full orbit

I don't get it. Where is the moon (or the debris that eventually formed it) supposed to have gotten the second boost neccesary to achieve orbit? We have the impact event performing the "launch" (flinging the material off of earth's surface), and then we need an other boost around the apogee to raise the perigee above the surface and achieve orbit, or else the material will fall back to Earth (difference between sub-orbital and orbital spaceflights gives some info on this). I know that Tidal acceleration is widening the moon's orbit, but that would be much too weak to give a boost in one orbit. 12.37.33.3 03:49, 18 March 2006 (UTC)

There is no second boost, of course. I would guess that the momentum of the original body is involved, and that not all of the material in orbit is actual impact ejecta. It would be nice to have this clarified. kwami 04:27, 18 March 2006 (UTC)
No second boost UNLESS you subscribe to the theory that aliens launched the material into orbit and constructed it there. (Broad grin, Tongue very firmly in cheek). But in all seriousness, Could you elaborate on your previous statement? How would the momentum of the original body help (it would set up the first boost, but not the second as I see it), and what about this non-ejecta material? 12.37.33.3 05:46, 18 March 2006 (UTC)
Not much to elaborate on, since I didn't realize I didn't understand this until you brought up the question. In simulations I've seen, large amounts of the mantle of the colliding body 'skip' off the Earth and enter orbit. Not all of it is ejecta from the impact basin. Also, part of the linear momentum of the colliding body becomes the angular momentum of the system, and the barycenter shifts from the center of the Earth to somewhere outside that point, so that the shape of an orbit would have changed while the material was in orbit. Perhaps that had something to do with why the material didn't follow an ellipse leading back to the point on the Earth where it started - the focus of the ellipse moved. kwami 08:35, 18 March 2006 (UTC)
But any application of thrust to an object in orbit raises the opposite side of the orbit. However hard the impactor hit the Earth, it couldn't raise the side of the orbit it hit on. It might send all the material off at escape velocity, but that's about all. Maybe the best option is a really hard impact: Blows both objects concerned to smithereens, and then the Earth and Moon form from the debris cloud. Differences in composition could come from irregular distribution of debris within the cloud. Linguofreak 19:40, 18 March 2006 (UTC)
Simulations suggest the heat of the impact melted the Earth's mantle to a depth of a thousand km, and some of the mantle went into permanent orbit (much more of course reimpacted), which makes this geologic time zero, but not so much that the Earth was actually disrupted. kwami 03:33, 19 March 2006 (UTC)
But I'm suggesting that we use a harder impact than called for by the normal theory, such as would disrupt the earth. I could understand how this might end up with two bodies in the end, otherwise I can't see how you could have any mass that didn't either fall to earth or end up on an escape trajectory. Linguofreak 04:53, 19 March 2006 (UTC)
There's no point. They didn't the math wrong just because we don't understand it. kwami 07:44, 19 March 2006 (UTC)
From the articles I've seen in Science, during the impact, the blob that settled down to form the Earth was in a transient state that was FAR from spherical, and that the gravitational pull of a massive, swinging lobe transfered some of its angular momentum to the blob that later settled down to form the Moon. This process took less than an hour. There are detailed dynamical simulations, of course; I'm just giving a verbal sketch of the pretty graphics. Harold f 06:01, 23 July 2006 (UTC)
OK, so basically a process analagous to the tidal widening (I forget the exact technical term for it) of the Moon's orbit. Interesting. That works. Still a bit surprising that you'd end up with a circular orbit, but I don't know enough about the subject to object. Linguofreak 14:06, 8 August 2006 (UTC)

[edit] deleted paragraph

I removed the following paragraph:

Other than the existence of the Moon itself, the primary legacy of this event, say researchers, is the fact that the Earth does not have enough of the lighter-colored felsic and intermediate rock-types to completely cover its entire surface. Thus we have continents made from felsic rocks and ocean basins which are made of the darker-colored, heavier and more metal-rich mafic rock types. This difference in composition along with the presence of water allows for an extensively active system of plate tectonics on the Earth. Others have postulated that the axial-tilt and initial rotation of the Earth had their origin at this time.

Continental rock is produced by tectonic subduction: rock melt separates, with lighter rock rising as magma and heavier rock sinking into the mantle. It is thought that the surface of the Earth after the Big Whack would have been entirely basaltic, and the quantity of continental crust is still growing today. That is, there may be enough lighter rock to completely cover the Earth's surface, but it has yet to separate from the mantle. Tectonics is thought to be possible because of the amount of water in the upper mantle. It's possible that without the impact there would have been more continental rock, enough to clog up tectonics, but I'd like to see a good reference for that before putting it in the article. kwami 08:14, 19 March 2006 (UTC)

Okay, maybe this was the source of the idea: [1]. There are some serious problems here, and I don't think we can take it seriously. The basic idea is this: "Today the ocean basins cover 70% of the planet; light rock from the moon can be used to make up the difference and fill in the ocean basins; therefore if the moon hadn't formed there would be no ocean basins and therefore no tectonics." This reads like an updated version of the idea that the moon is the size of the Pacific Ocean basin, therefore the Pacific may be the scar left over from the formation of the moon. What is ignores is that the 70% figure is only valid today; it's not a quantity that's been "missing" since the impact, crust "stored over our heads". Also, the vast majority of the material blasted out by the impact fell back to Earth. This material was of the same type of rock as the moon, yet the continents didn't form till later. It's asking a bit much of coincidence to suggest that if that extra 1% had fallen back to earth instead of forming the moon, the continents wouldn't have evolved much as they have. The bulk of the moon is like the Earth's mantle, not like its continents. kwami 09:11, 19 March 2006 (UTC)

[edit] Original hypothesis?

The idea that the moon was a piece of the earth that had broken loose was suggested back in 1879 by the British astronomer George Howard Darwin (second son of Charles Darwin). However, Darwin believed the matter which formed the moon was pulled away from the still molten earth by solar tides, and not an impact. Sources: Encyclopaedia Britannica and Asimov's New Guide to Science (p159).

Yes, that is one of the older suggestions. Does it belong in an article about the giant impact? (SEWilco 05:30, 25 August 2006 (UTC))
Darwin attempted to calculate the moment of separation of the Moon from Earth, based on the observation that the Moon's distance from Earth is steadily increasing. He was not able to complete the calculation further than the point where the two bodies were about 1,000 mi apart, however. This was discussed in a recent episode (The Moon) of The Universe series on The History Channel. And yes, this is of historical significance to the theory/article and should be included. — Loadmaster 17:01, 20 July 2007 (UTC)

[edit] Data correct?

The article notes: Current estimates based on computer simulations of such an event suggest that some 2% of the original mass of the impactor ended up as an orbiting ring of debris, and about half coalesced into the Moon between 1 and 100 years after the impact. 1-100 years for the moon to form? Sounds too short to me. Can any astro-oriented type people look at this? —Preceding unsigned comment added by SparhawkWiki (talk • contribs) 02:51, 25 August 2006

With a quick look I found these: [2] doi:10.1038/38669 (SEWilco 05:17, 25 August 2006 (UTC))


[edit] Bungled jargon

"Theia is thought to have formed Trojan to Earth". In addition to the dreaded "is thought to" passive of non-attribution, the rest is jargon. Almost any change would be clearer and more stylish. --Wetman 03:26, 28 August 2006 (UTC)

No response. Does my edit better reflect what is intended in this use of "Trojan"? --Wetman 01:11, 8 September 2006 (UTC)

[edit] volatile elements

From the article main section: Evidence for this impact comes from rocks collected during the Apollo Moon landings, which show an oxygen isotope composition nearly the same as the Earth's mantle. Chemical inspection of those rocks found them to be nearly devoid of volatile and lighter elements...

From "Difficulties": The Moon's volatile elements are not depleted as expected from the giant impact hypothesis.

This seems inconsistent... 24.85.239.188 11:52, 13 September 2006 (UTC)

The cited source for the line in the difficulties section gives an example of volatiles that don't seem to match the hypothesis. The lunar Rb/Cs ratio, according to the author of the cited source, ought to be less than the terrestrial ratio, where in fact it is greater. Supposedly, Rb is more volatile than CS, and so its relative concentration should have been reduced. One would assume, then, that most of the lighter and more volatile elements are depleted and it is just the Rb concentration that doesn't match this trend. Clearly the author of that 'difficulties' point does not believe in the giant impact theory, and so construed evidence that one element isn't as depleted as it ought to be to mean that no volatiles are depleted. I will change the difficulties point by adding the qualifier 'some' to clear up this ambiguity. Harperska 23:44, 25 September 2006 (UTC)
The cited source is not dated. Latest reference is 1997. Is 1997 before the more complex simulations, which I think suggest that most of the Moon came from the impactor? The source says the ratios are based on the assumption that the Moon's material came from Earth. (SEWilco 06:05, 26 September 2006 (UTC))

[edit] Textual Error?

The current first paragraph reads "The original hypothesis was first proposed in a paper published in Icarus in 1975 by Dr. William K. Hartmann and Dr. Donald R. Davis." However, I have (or had) and old textbook from the 1960s which proposed this same theory. The title of the book was The Planets, but I cannot give more information just yet (I don't have it in front of me, and may not own it anymore). Firsfron of Ronchester 22:50, 25 September 2006 (UTC)

In the 1960s one theory was that as the Earth formed and its rotation increased, the material which became the Moon was spun off. The Pacific Ocean was considered as possibly having been created by that event. Did "The Planets" refer to an impact event or to the three non-impact theories of the creation of the Moon? (SEWilco 06:20, 26 September 2006 (UTC))

[edit] Siderophile elements

I propose deleting the following sentence

If the bulk of the proto-lunar material had come from the impactor, the Moon should be enriched in siderophilic elements, when it is actually deficient of those.[5]

This is not a mainstream view, and the cited article was published in what some might consider the "gray literature." Several publications have used the depletion in siderophile elements as an indication that some form of core forming event processed either the Impactor, Earth, or Moon (after re-accretion). In fact, the siderophile element depletions have been used to place constraints on the size of the lunar core. The most recent publication discussing this is Righter (2002, Does the Moon have a metallic core, Icarus, 158, 1-13).

Also, some of the other "difficulties" are in fact not difficulties at all. In my opinion, the scientific calliber of this article is very low, the text is heavily biased towards the recent and not fully accepted Lagrange point hypothesis, and this needs to be heavily edited by an expert. Lunokhod 13:58, 15 November 2006 (UTC)

How gray is the 2002 G.K. Gilbert Lecture at the annual meeting of the GSA [3]? Dan Watts 20:05, 15 November 2006 (UTC)
If you read the original paper that was cited, you will see that there is only one sentence that discussess the siderophile element abundances of the Moon. The claim that is made is not supported by citations, or detailed reasoning. The paper is all the more bothering in that they do not even cite the Righter (2002) paper, even though this paper was published in 2005! They do not even quote the work by Canup and Asphaug (2001, Nature) or Canup et al. (2001, Icarus). I maintain that this article, which was published in the Indian Journal of Earth System Science is not well researched. As for the article by Jack Schmitt, this was not peer reviewed. Good sources of peer reviewed articles can be found in the book "Origin of the Earth and Moon". If you are looking for articles that are highly critical of the giant impact and lunar magma ocean hypothesis, look at the chapters written by J. Jones. I'll add this to the refernce list. Lunokhod 20:38, 15 November 2006 (UTC)
Is this the same J. Jones referenced as author of an LPS paper? Dan Watts 14:59, 21 November 2006 (UTC)

[edit] English Please?

The the following excerpt is so poorly written that I have no idea what it is saying:

Iron oxide (FeO) content of 13% of the bulk Moon properties rule out the derivation of the proto-lunar material from any but a small fraction of Earth's mantle.[4]

Could anyone who knows what its supposed say make this readable? —The preceding unsigned comment was added by 68.231.220.133 (talk) 08:29, 14 December 2006 (UTC).

I wouldn't believe this. This entire article is poorly written and does not represent a consensus of the scientific community. Concerning this point, though, there was a recent article in Nature by Rubie et al. (2004) showing that the bulk silicate portion of the Earth and Moon could have had the same iron content. The idea is that during the crystalization of a terrestrial magma ocean, FeO is partitioned into the core. Their results nicely predict the present day FeO content for the mantle's of Earth, Moon, Mars, and Vesta. When I get some time in the next month of two I am going to clean up this article. Lunokhod 16:07, 14 December 2006 (UTC)

[edit] Date

First proposed in 1975? I remember reading about this "discredited" theory in primary school, which would be at least four years earlier. I believe it is decades older. Rich Farmbrough, 12:00 13 January 2007 (GMT).

This is the correct date for the first publication. Lunokhod 12:24, 13 January 2007 (UTC)

[edit] Early terran oceans a problem?

I stumbled across this 2001 New Scientist article, which suggests that the discovery of a water-affected zircon crystal dated to 4.404 billion years presents "real problems" for the impact theory of lunar formation.

I see no mention of this in the article: should I assume that those problems have been overcome, one way or another, since then? Hv 04:18, 23 March 2007 (UTC)

[edit] Selective removal of sial

SEWilco removed the following excerpt claiming that it is a speculation: "The Earth's crust is made of two layers called sima and sial. Sima is the lower and denser layer. It is 5 to 10 km thick and covers the entire surface of the Earth. Sial is 20-70 km thick and covers only 30% of the Earth's surface; this is the elevated part of the Earth's surface called continents. The remaining 70% of the Earth's surface is covered with oceans. None of the existing theories explain how the sial was selectively scooped up from 70% of the Earth's surface and deposited on the Theia/proto-Moon."

Is there any proof that any part of this excerpt is a speculation? I would rather call it a glaring omission. SEWilco's activities on Wikipedia have been restricted by illegal, unreasonable, and arbitrary restrictions and enforcement.

15:27 & 16:00, User:Towelhead

Sial is sometimes called granitic layer of the crust, because it is made mostly of granite, which is made mostly of silica (SiO2 content = 72%), which is the main ingredient of glass.

The temperature of Earth increases about 36 degrees Fahrenheit (20 degrees Celsius) for every kilometer (about 0.62 miles) you go down. Near the center, its thought to be at least 7,000 degrees Fahrenheit (3,870 Celsius).

The meaning of these facts is that the top 10 kilometers of the sial is made of hard and rather cool rock. It is too hard and too brittle to deform under pressure. It is difficult to imagine what could generate the enormous force needed to break and pile up the granite into a pile up to 70 km high. Furthermore, the sial part of the crust does not look like a messy pile of rocks, but like a solid, rather uniform layer of bedrock. Towelhead 01:44, 3 April 2007 (UTC)

[edit] Article title

Does anybody else feel that the appropriate title for this article would rather be giant impact theory than giant impact hypothesis? The actual hypothesis here is [The Moon] is thought to have formed as a result of a collision between the young Earth and a Mars-sized body (...), all the rest is the surrounding theory. Nick Mks 12:16, 9 April 2007 (UTC)

I would suggest giant impact nonsense, since – as an example – the Lagrangian points L4 and L5 don't have any importance in the orbit of Earth, since the gravitation of Jupiter is much larger compared to Earth's gravity in those points. Clearly, the orbits of the protoplanets can't be treated as three body problem, and hence the Lagrangian points have no meaning at all. 84.59.63.152 08:15, 14 April 2007 (UTC)
The theory of Theia forming at a Lagrange point is only a very recent hypothesis (2005) and certainly isn't as widely accepted as the overall hypothesis of giant impact. As others have pointed out, the Lagrange point idea probably has too prominent a position in this article. Sakkura 11:45, 26 April 2007 (UTC)

You misunderstand the scientific meaning of theory, which is "a logically self-consistent model or framework for describing the behavior of a related set of natural or social phenomena". A theory has far-reaching applications and great explanatory power: it is just short of "truth". Thus we talk of atomic theory, number theory, etc. Urhixidur 13:21, 14 April 2007 (UTC)

[edit] Remains of previous earth

If such an impact occured would anything have survived? Even more importantly would any traces of what was here before (life or maybe civilization) survive?

The impact with Theia is proposed to have occurred just 34 million years after the Earth formed, which means it happened while the Earth was still an extremely inhospitable place for life. After the impact, Earth would actually have had an atmosphere of rock for as long as two thousand years, and that means nothing could possibly have survived even if it had existed on the planet previously. Bear in mind that the asteroid proposed to have wiped out the dinosaurs had a diameter of 10 kilometers - Theia would have had a diameter of several thousand kilometers! Sakkura 10:47, 27 April 2007 (UTC)
Theia would have had a diameter of several thousand kilometers!That's exactly why I was wondering if any TRACE could have survived. Thanks for the answer —The preceding unsigned comment was added by 86.121.75.80 (talk) 14:48, 28 April 2007 (UTC).
Since the hypothesized impact would have more or less completely restructured the surface of the Earth, involving massive amounts of heat, I doubt there would be any traces left at all of whatever was on the surface before the impact. — Loadmaster 17:09, 20 July 2007 (UTC)

[edit] Removing the How did the moon get into orbit? link

The website is creationist propaganda: it is linked to by the Edinburgh Creation Group, was made by the maker of that site; the author clearly has creationist intentions, which are expressed in the site itself. On top of this, the argument he lays out on the page is clearly fallacious: he claims that a point-mass simulation is enough to render all theories of moon formation invalid. I'm about to remove the link. Spottedowl (talk) 22:26, 21 February 2008 (UTC)