Difference between revisions of "Origin of the Moon"

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(added more criticisms of Giant-Impact Model)
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**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.
 
**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.
  
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:
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== Giant-Impact Model ==
  
*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:
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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>
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 +
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 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.
 
**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.
 
**A high-velocity collision might be sufficient to release enough energy to place a substantial mass of the Earth's crust into orbit.
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== Criticism of the Giant-Impact Model ==
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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>
  
 
But nearly two decades later, ''Scientific American'' observed that:<ref>http://www.sciam.com/article.cfm?chanID=sa006&colID=5&articleID=000A90B0-C919-1C6E-84A9809EC588EF21</ref>
 
But nearly two decades later, ''Scientific American'' observed that:<ref>http://www.sciam.com/article.cfm?chanID=sa006&colID=5&articleID=000A90B0-C919-1C6E-84A9809EC588EF21</ref>

Revision as of 14:51, 18 March 2007

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.

Specifically, each of these prevailing scientific theories were disproven by the lunar landings:[1]

  • 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.

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.[2] 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.[3]

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.

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."[4]

But nearly two decades later, Scientific American observed that:[5]

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:[6]

Considering all the twists and turns in lunar science, nobody claims that the models are complete just yet.


Reference

  1. Planetary Science Institute: The Origin of the Moon
  2. Id.
  3. Id.
  4. http://www.lpi.usra.edu/meetings/origin98/pdf/4045.pdf
  5. http://www.sciam.com/article.cfm?chanID=sa006&colID=5&articleID=000A90B0-C919-1C6E-84A9809EC588EF21
  6. Id.