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Line 1: − ==The Young Earth Creationist Position==+ − According to [[Young Earth Creationism|young earth creationist]] scientists, naturalistic explanations for the origin of the moon are inadequate and the [[moon]] is approximately 6,000 years old. <ref>http://www.answersingenesis.org/creation/v20/i4/moon.asp</ref><ref>http://www.creationscience.com/onlinebook/AstroPhysicalSciences8.html</ref> One argument against an old age posited by evolutionists is that the Moon would have been lost to the pull of Earth's gravity a long time ago.<ref>Answers in Genesis: [http://www.answersingenesis.org/creation/v14/i4/moon.asp "Is the moon really old?"]</ref> − + − There is not a complete consensus amongst contemporary scientists as to how the Moon came into existence. Historically, three hypotheses were widely seen as plausible contenders for such an explanation: they were the “Fission Hypothesis”, which held that the Moon was ejected by the ancient, swiftly-spinning Earth; the “Capture Hypothesis”, in which the Earth’s gravity captured another planet; and the “Co-accretion Hypothesis” in which both the Earth and the Moon came into being side by side formed together from the same primordial loose aggregation of space dust. + + − All of these scenarios had serious defects as theories, and all were formulated before the Apollo Program of the late 1960s and early 1970s brought back samples of Moon rock to provide scientists with unprecedented data about the Moon’s composition and history. Those data, and more sophisticated measurements of the Moon’s mass and orbit available to recent researchers, led to the earlier theories losing favor and the promotion of a new one: “The Big Impact Hypothesis”. This theory envisages a massive collision between an ancient Earth and a large asteroid, one in which the early Earth melted and the asteroid disintegrated, only to re-coalesce as the Moon over a period of time.+ + − ==The "Big Three"==+ − Prior to the lunar landings, there had been three major hypotheses that all had been considered valid explanations for the origin of the Moon.+ − + − Developed in 1878, this hypothesis by [[George Howard Darwin]] (son of [[Charles Darwin]]) argued that the Moon had been a part of a rapidly spinning [[Earth]]. This rapid spin, enhanced by the Sun's gravitational influence, led to a piece of the Earth breaking free and forming the Moon. Osmond Fisher held that the Pacific ocean basin is actually the scar of this process.<ref name="Nova1">PBS NOVA: "To the Moon - Origins" [http://www.pbs.org/wgbh/nova/tothemoon/origins.html (Page 1)]</ref> − ===Hypothesis 2: Capture===+ − In 1909, [[Thomas Jefferson Jackson See]] proposed that the Moon was actually a planet that had been created elsewhere and that had been caught by Earth's gravity after being slowed down by debris.<ref name="Nova1"/> − ===Hypothesis 3: Coaccretion===+ − Many scientists, including [[Edouard Roche|Édouard Roche]], supported the hypothesis that the Earth and the Moon formed side by side from the material that formed all planets of this solar system. The name comes from the term "accretion disc", which is a disc formed by diffuse material that orbits a central body.<ref name="Nova1"/>+ + + − + − For a long time, these three models had been accepted as describing possible lunar origins. However, later research was to produce evidence that worked against them. − After the Apollo program, rock samples taken from the Moon revealed two important things: − #The Moon lacks iron. This is important to note because the Earth, in comparison, has a lot of it (in the core). − #The Moon and the Earth have exactly the same oxygen isotope composition. − Along with calculations in the field of energy and angular momentum, these two points spoke against the "Big Three" hypotheses as follows: − ===Consequences for the Fission Hypothesis===+ − Since the material that spun off the Earth would have come from the mantle, the lack of iron would not have been a problem (Earth's iron drained towards the core early on, leaving a depleted mantle).<ref name="PSI">Planetary Science Institute: [http://www.psi.edu/projects/moon/moon.html "The Origin of the Moon"]</ref> This would also explain why the Moon has such a small core.<ref name="Nova1"/> For obvious reasons, the theory also covers the issue of the oxygen isotope composition. − However, the total angular momentum today is too small to back this hypothesis.<ref name="NovaCelestia">Nova Celestia: [http://www.novacelestia.com/space_art_solar_system/earth.html#moon_earth_creation "The Creation of the Earth-Moon System"]</ref>+ − Osmond Fisher's hypothesis that the Pacific Ocean was the scar of the fission event, was later nullified with the discovery of [[Plate Tectonics]].+ − ===Consequences for the Capture Hypothesis===+ − There is only a very small chance that a stray planet would ease into an orbit around the Earth similar to the one the Moon has. Moreover, this hypothesis fails to explain the oxygen isotope similarity between the two bodies, and also leaves unexplained the issue of why the Moon's core is so small.<ref name="Nova1"/>+ − ===Consequences for the Coaccretion Hypothesis===+ − This model does not require low probability events to occur, in contrast to the Capture model, and provides a cogent explanation as to why the Earth and Moon share a common oxygen isotope composition. However, there are unanswered questions regarding the angular momentum of the two bodies (It should be mentioned that there have been attempts to address this problem recently: see [[#Current Status|Current Status]].).<ref name="Nova1"/> − ==Giant Impact Hypothesis==+ − ===Development=== − In 1974, William Hartmann and Donald Davis suggested the hypothesis that a planetoid, estimated in some calculations to be the size of Mars - impacted with a relatively young Earth and blasted mantle material into orbit, where this would eventually form the Moon. This model also became known as the "Big Whack" hypothesis. Around the same time, Alastair Cameron and William Ward had come to a similar conclusion. However, their research had been motivated by studies of the combined angular momentum of the Earth and Moon.<ref name="PSI"/><ref name="Nova2">PBS NOVA: "To the Moon - Origins" [http://www.pbs.org/wgbh/nova/tothemoon/origins2.html (Page 2)]</ref> − Initially, the hypothesis was rejected with the claim that a catastrophic event of such a dimension and with such drastic results seemed extremely unlikely.<ref name="Nova2"/> Still, it explained the lack of iron, the oxygen isotope issue and the angular momentum.+ − − Ten years later, the Giant Impact Hypothesis emerged as the leading model after a conference about Moon origin in Kona, Hawaii. In the 1990s, Robin Canup picked up the research and created simulations to determine possible scenarios that might explain the formation of the Moon.<ref name="PSI"/><ref name="Nova2"/> − − Canup initially came to the conclusion that much of the material blasted off by a "Big Whack" would either fall back to Earth or fly off into space, thus requiring a very large impactor, two or three times larger than initially envisaged. However, later on, improved computer simulations suggested that the size of the impactor might not have to be so large after all, thus leaving all calculations regarding mass and momentum intact.<ref name="PSI"/><ref name="SciAm">Scientific American: [http://www.sciam.com/article.cfm?chanID=sa006&colID=5&articleID=000A90B0-C919-1C6E-84A9809EC588EF21 "Earth-Shattering Theory"]</ref> − − ===Criticism=== − The hypothesis is far from complete, though. Despite addressing the issues raised in the light of the first lunar landings, the Giant Impact Hypothesis leaves quite a few issues currently not fully addressed: − *One study suggested three tests of the hypothesis, based on things that should have occurred after such an impact. The result of these tests did not prove the Giant Impact Hypothesis, but it also did not disprove it. Still, the paper raised a few points that have to be factored into the model.<ref>J. H. Jones: [http://www.lpi.usra.edu/meetings/origin98/pdf/4045.pdf "Tests of the Giant Impact Hypothesis"]</ref> − *A study analysing the bulk composition has come to the conclusion that "the high bulk FeO (Ferrous Oxide)content of the Moon rules out the derivation of the proto-lunar material from any but a small fraction of the terrestrial mantle".<ref>S. R. Taylor: [http://www.lpi.usra.edu/meetings/lpsc97/pdf/1070.PDF "The Bulk Composition of the Moon"]</ref> − *Addressing the above concern, the Giant Impact Hypothesis raised the point that the impactor also contributed a large share of the base material that formed the Moon. But as another paper pointed out, the Moon is lacking siderophilic (iron-loving)elements that should be present in such a case.<ref>Galimov and Krivtsov: [http://www.ias.ac.in/jessci/dec2005/ilc-3.pdf "Origin of the Earth–Moon system"]</ref> − − ==Current Status== − As of now, the Giant Impact Hypothesis still stands. Research on it is not yet complete, and the model is currently neither proven nor disproven. Nevertheless, scientists consider it to be the most plausible theory formulated so far. − − Independently of the Giant Impact Hypothesis, Peter Noerdlinger from Saint Mary's University in Halifax, Canada, proposed an expansion of the Coaccretion model. He suggested that the Moon formed next to the Earth, complete with an iron core. But this core was then ripped out by the Earth's gravity shortly after the formation, leaving an iron-less Moon behind to orbit the Earth.<ref>New Scientist: [http://space.newscientist.com/article/mg19325875.700-did-the-new-moon-lose-its-iron-heart.html "Did the new moon lose its iron heart?"]</ref> − − Further research will show if either of these hypotheses is correct, or if scientists will develop a new theory based on new observations. + + − [[category:astronomy]]
restoring clear, consise version without the liberal bias; feel free to add info but not placement bias
All the prevailing, well-accepted theories of the origin of the Moon were completely disproven by the lunar landings and studies of the lunar rocks afterwards. The material, to the surprise of scientists, lacked iron that permeates the Earth's crust.
== Old Moon View ==
Specifically, each of these prevailing scientific theories were disproven by the lunar landings:<ref name="PSI">Planetary Science Institute: [http://www.psi.edu/projects/moon/moon.html The Origin of the Moon]</ref>
*The Moon formed in an orbit around Earth at the same time that Earth formed.
**This theory was disproven upon learning that the Moon has proportionally far less iron in it than the Earth.
*The Moon formed in a part of the solar system that was low in iron, and was later captured into an orbit arount the Earth.
**This was also disproven by examination of lunar rocks, which exhibit the same oxygen isotope composition as the Earth, unlike rocks known to come from other sources in the solar system, e.g. Mars.
*The Earth was originally spinning so fast that it spun off a fragment of lower density (iron-poor) material which became the Moon.
**This solves the isotopic similarity and the relative lack of iron, but an analysis of the total angular momentum and energy involved ruled out this possibility.
===Hypothesis 1: Fission===
== Giant-Impact Model ==
For ten years after the lunar landings, non-creationist scientists lacked any accepted theory about the Moon's origin. In 1984, an international meeting was convened in Kona, Hawaii, for the purpose of agreeing on a new theory for the origin of the Moon.<ref>''Id.''</ref> The attendees at the meeting agreed upon the following "giant-impact model," which was first proposed in 1975 but which had not yet been generally accepted.<ref>''Id.''</ref>
This theory proposes an impact with a large planetesimal (asteroid-like body) released a great quantity of debris into orbit, a portion of which collected under the influence of gravity. There is no direct evidence for this theory. It is supported by non-creationist scientists, however, because only it might explain the following:
**The lack of iron, provided the impact of the planetesimal happened relatively late in the earth's formation and after the Earth's iron had sunk towards its core. In that manner the Moon could pick up mantle from the Earth that has less iron. Most of the planetesimal itself would have sunk into the earth's core.
**The similar oxygen isotope composition between the Moon and Earth could be explained by such a collision, provided the Moon were then formed from debris dislodged from the Earth by the collision.
**A high-velocity collision might be sufficient to release enough energy to place a substantial mass of the Earth's crust into orbit.
==Observations and calculations==
== Criticism of the Giant-Impact Model ==
This new theory fail lacks testability and falsifiability, which are essential aspects of science as explained by [[Karl Popper]].
Scientists did find that none of three proposed tests are "supportive of the Giant Impact model."<ref>http://www.lpi.usra.edu/meetings/origin98/pdf/4045.pdf</ref>
Another article noted that the Moon is lacking in siderophilic elements (Au, Co, Fe, Ir, Mn, Mo, Ni, Os, Pd, Pt, Re, Rh, Ru) found on Earth, and this indicates that the Moon was not formed by materials broken off of Earth.<ref>http://www.ias.ac.in/jessci/dec2005/ilc-3.pdf</ref>
A third study found that "the bulk composition of the Moon differs significantly from that of the terrestrial mantle" and that "[t]he high
bulk FeO content of the Moon rules out the derivation of the proto-lunar material from any but a small fraction of the terrestrial mantle."<ref>http://www.lpi.usra.edu/meetings/lpsc97/pdf/1070.PDF</ref>
Nearly two decades after the Giant-Impact Model was embraced at the Hawaii convention, ''Scientific American'' observed that:<ref>http://www.sciam.com/article.cfm?chanID=sa006&colID=5&articleID=000A90B0-C919-1C6E-84A9809EC588EF21</ref>
:Unfortunately, researchers have had trouble getting the giant-impact model to work without the contrivances that scuttled earlier theories.
:Four facts and three parameters is a recipe for contradiction. To explain the moon's low iron content, you need to avoid a grazing collision (corresponding to a large impact angle), lest too much of the impactor's iron spill into orbit. Then, to explain the angular momentum, you need to compensate for the smallish angle with a hefty impactor. Then, to explain the moon's mass, you need to adjust the proto-Earth's mass. In the end, you might find that the total mass is incorrect.
''Scientific American'' concluded:<ref>''Id.''</ref>
:Considering all the twists and turns in lunar science, nobody claims that the models are complete just yet.
== Reference ==
== Reference ==
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