Origins of the Moon
The moon has fascinated mankind for many thousands of years. It has assumed a role in legend and lore alike, being worshiped as a god, and feared as a demon. Indeed, from the days when man first looked skyward, he knew the moon served some important purpose, one he could not yet comprehend. During the scientific advances of the 1600s, and the industrial and literary revolutions that soon followed, the moon played a central role in story and equation alike. Newspapers of the 1800's proclaimed the greatest "feat of physics ever accomplished": weighing the moon. And when man finally reached the moon in 1969, he accomplished the impossible dream of eons past. Nevertheless, with the boundary of space conquered, we have gained only slightly greater understanding of the giant looming in the sky. Now, scientists are attempting to answer a question as difficult as space is vast: how did the moon form?Some important factors need to be considered in order to form a successful theory about the origin of the moon One factor is the size of the Moon relative to the Earth. The Moon is about one-fourth the size of the Earth (Editors 22).. Also, the Moon's density needs to be taken into consideration. The Moon is only 60% of the Earth's
A third factor that needs to be considered is the angular momentum of the Earth-Moon system. Angular momentum needs to be conserved. Therefore if the Earth slows down in its rotation then the Moon must move away from Earth a fraction to conserved momentum (Editors 23). density, which indicates that the Moon is lacking in heavy metals such as iron and nickel. Also the Moon's bulk composition appears to be similar but not identical to the Earth's upper mantle, which is comprised dominantly of iron- and magnesium-rich silicates (Spudis 137). Darwin's fission theory was later discredited. The main factor in discrediting his theory was the Roche limit, a calculation which explains that within a certain distance of a planet, gravitational influences would keep particles from coalescing together to form any moon. Thus, any material that would have jettisoned from this fission process would have orbited the Earth as celestial rings (Jaywardhana). Another inconsistency to Darwin's theory concerned angular momentum. If any amount of mass was to be torn away from the Earth, as he stated, then the angular momentum of the Earth-Moon system at that time needed to be no less than four times greater than it is today. Additionally, viscosity could have been no greater than that of water, and given the present composition of the present Earth, this is not feasible (Editors 24). Moreover, the Moon would have had a final orbit directly above the Earth's equator when in reality the moon is now tilted between 18 and 28 degrees above the Earth's equator. (Anderson) The first theory to be introduced was the fission theory. George Darwin first proposed it in 1878 (Editors 22). According to this hypothesis, there was no Moon originally. The Earth was spinning very rapidly - so rapidly, in fact, that one day would have been two hours long. This rapid rotation would have caused bulges at the equator. The Earth's lighter material would have migrated to the equator where the bulges occurred during its fast rotation. Eventually, the sun's constant gravitational pull would have ripped at these bulges, forcing a large chunk of Earth would have split off, or fission, from the main body, as shown in Picture 1 (Editors 22). As the materials that separated were decidedly "lighter" materials, the mass that was cast off would have been considerably less dense than the Earth. This large chunk would
Some common words found in the essay are:
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Approximate Word count = 1619
Approximate Pages = 6 (250 words per page double spaced)
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