The Origin of the Moon Essay Example | Topics and Well Written Essays - 1250 words

The Origin of the Moon - Essay Example The earliest theory among them is that â€Å"earth had somehow spawned the moon† out (Schrunk, 1). George Darwin, son of the biological evolution theorist, Charles Darwin, had proposed this theory known as â€Å"fission hypothesis† in 1878 (Schrunk,1). This theory was based on the logic that as moon is gradually moving away from the earth (because the time taken by moon to make one revolution around the earth goes on increasing), logically it can be concluded that this is the continuation of an outward momentum initiated by the fission. Hence it is concluded that once moon might have been â€Å"closer to the earth than it is now† (Schrunk, 1). The reason for the split is also well-explained in fission theory. It is speculated that some kind of gravitational imbalance within the earth caused by its previous shape might have made it spit out a piece which became moon. The fission theory is supported by the fact that the core matter of moon is â€Å"not as massive as the earth’s† and also that same nonradioactive stable oxygen isotopes are found on the â€Å"terrestrial rocks† of both earth and moon (Gergo, 4,5). Thus this theory speculates that it was from the less dense mantle of the earth that moon was broken away as a separate entity. The weakness of fission theory is that there is a scientifically proven minimum distance near to the earth below which moon cannot exist in solid form and can exist only as â€Å"a ring of debris† (Schrunk, 1). Hence moon could never be close to earth within this minimum distance and continue to exist as a solid cosmic body. After proving this in 1873, Edouard Roche contested fission hypothesis and put forth the â€Å"co-accretion† theory (Schrunk, 1). Co-accretion theory said that earth and moon most probably might have been formed â€Å"at the same time, in the same neighborhood of the solar system† (Schrunk, 2). This is an assumption based on the similarities in st ructure between earth and moon like the presence of oxygen isotopes. A third theory on the origin of moon was proposed by Thomas.J.J.See (qtd in Schrunk) who theorized that â€Å"moon was †¦ a captured satellite† (Schrunk, 2). This theory was supported by one fact which came to light in that period. It was proven that at least some of the satellites of Saturn and Jupiter might have been captured ones (Schrunk, 2). See’s theory later came to be called as â€Å"capture hypothesis† (Schrunk, 2). This theory says that owing to the gravitational dynamics within and around the area where now the solar system exists, the orbit of moon (which was then far away from the earth) came near the earth (Schrunk, 2). And earth captured moon into becoming its satellite. The fourth and latest hypothesis on the origin of moon is known as â€Å"planetesimal impact hypothesis† and this theory has evolved combining certain features of all the three theories on the origin of moon that were proposed before it (Schrunk, 2). This hypothesis takes the idea that earth was hit by a â€Å"pre-planetory body† of the size of Mars, from the capture hypothesis (Schrunk, 2). It also brings in the argument that this collision had forced out, a huge quantity of debris which is a proposition put forward by the fission hypothesis (Schrunk, 2). And finally the â€Å"planetesimal impact hypothesis† also concludes that this debris â€Å"condensed into moon,† as was suggested partially by the co-accretion hypothesis (Schrunk, 2). The collision is supposed to have happened around 100 million years after the formation of the earth (Wilkinson, 73). This great impct is also thought to have caused the tipping of the axis of the earth and â€Å"inaugurated the seasons† on earth (Wilkinson, 73). This is the theory on moon’s origin which has gained the maximum approval. This is also in the context of many