Difference between revisions of "Origin of the Moon"

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m (Reverted edits by Suricou (Talk); changed back to last version by Aschlafly)
(Pseudo-revert with rephrasing and minor corrections. If Canup's moonlets are brought back in, I suggest that the source isn't just selectively quoted to create doubt.)
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All the prevailing theories of the origin of the Moon were completely disproven by the lunar landings and studies of actual material taken from the Moon. The material, to the surprise of scientists, lacked iron that permeates the Earth's crust.
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Various theories regarding the origin of the moon have been considered as follows:<ref name="PSI">Planetary Science Institute: [http://www.psi.edu/projects/moon/moon.html The Origin of the Moon]</ref>
  
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The three traditional theories were disproven as follows:<ref>http://www.psi.edu/projects/moon/moon.html</ref>
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# One theory was that the Moon formed in an orbit around Earth, at the same time that Earth formed. But the lack of iron on the Moon, in contrast with the abundance of iron on Earth, speaks against this.
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# Another theory was that the Moon formed in a part of the solar system that lacked iron, and was later captured by the Earth's orbit. This failed upon examination of lunar rocks, which exhibit the same isotope composition as the Earth.
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# One theory was that the Moon formed in an orbit around Earth, at the same time that Earth formed. But the lack of iron on the Moon, in contrast with the abundance of iron on Earth, disproved this.
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# Yet another theory was that the Earth spun off the Moon. This solves the isotopic similarity, but an analysis of the total angular momentum and energy involved shows that this is impossible in light of the current orbit.
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# The final theory is that that impact with a large planetesimal (asteroid-like bodies) released a great quantity of debris into orbit, a portion of which collected under the influence of gravity. This theory is the currently accepted explanation of the origin of the Moon, and several things speak for it. Among them are explanations how the theory is compatible with the findings that speak against the other theories:
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# Another theory was that the Moon formed elsewhere in the solar system where there was little iron, and was later captured by the Earth's orbit. This failed upon examination of lunar rocks, which exhibit the same isotope composition as the Earth.
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##The theory states that the impact of the planetesimal happened relatively late, which would explain (among other things) the lack of iron: By the time of the impact, the Earth's iron had already sunk deeper towards the core. Thus, the debris that eventually formed the Moon came from the iron-depleted mantle.
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##Since the Moon was created from debris blown out of the Earth, the Earth and the Moon have the same oxygen isotope composition.
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# Yet another theory was that the Earth spun off the Moon. This solves the isotopic similarity, but an analysis of the total angular momentum and energy involved shows that this is impossible in light of the current orbit. Also, spinning of the Moon would have given it iron also.
 
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What's left?  Conferences were held to propose anything other than creation to explain the Moon.  The best the scientists could come up with was a huge asteroid colliding with the Earth and then settling into an orbit with it. This begs many questions, such as the implausibility of a round asteroid hitting Earth and remaining round afterwards, and the Earth surviving with its shape also.  What would be the odds?  And wouldn't that likely result in some iron being on the Moon's surface?
 
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In the 1990's, Dr. Robin Canup wrote her Ph.D. dissertation about the Moon's origin and this recent "giant impact hypothesis."  Her models suggested that a massive collision would result in moonlets, and she initially questioned whether a moon would even result.<ref>http://www.psi.edu/projects/moon/moon.html</ref>  Her later work was more "successful" in finding some way that a moon might result from this.
 
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No student is ever taught about how theories of the origin of the Moon were disproved by the lunar landings, and how many unresolved issues remain to this day.  Instead, this issue is almost completely avoided in all science curricula.
 
  
 
== Reference ==
 
== Reference ==
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Revision as of 00:07, March 18, 2007

Various theories regarding the origin of the moon have been considered as follows:[1]

  1. One theory was that the Moon formed in an orbit around Earth, at the same time that Earth formed. But the lack of iron on the Moon, in contrast with the abundance of iron on Earth, speaks against this.
  2. Another theory was that the Moon formed in a part of the solar system that lacked iron, and was later captured by the Earth's orbit. This failed upon examination of lunar rocks, which exhibit the same isotope composition as the Earth.
  3. Yet another theory was that the Earth spun off the Moon. This solves the isotopic similarity, but an analysis of the total angular momentum and energy involved shows that this is impossible in light of the current orbit.
  4. The final theory is that that impact with a large planetesimal (asteroid-like bodies) released a great quantity of debris into orbit, a portion of which collected under the influence of gravity. This theory is the currently accepted explanation of the origin of the Moon, and several things speak for it. Among them are explanations how the theory is compatible with the findings that speak against the other theories:
    1. The theory states that the impact of the planetesimal happened relatively late, which would explain (among other things) the lack of iron: By the time of the impact, the Earth's iron had already sunk deeper towards the core. Thus, the debris that eventually formed the Moon came from the iron-depleted mantle.
    2. Since the Moon was created from debris blown out of the Earth, the Earth and the Moon have the same oxygen isotope composition.

Reference

  1. ↑ Planetary Science Institute: The Origin of the Moon
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