Even though it is lit up by thousands of stars, the night sky would seem vacant to most of us without the presence of Moon. The only natural satellite of Earth, the Moon has been the subject of interest of man forever. Moon had a position of reverence in ancient civilizations and has a great stature in various mythologies.
Myths and stories aside, the cosmic body has been one of the favorites of scientific world. The scientists are more interested in Moon now than ever, even so far as researching about the possibility of living there. As long as they have been mulling over the formation of the universe and solar system and Earth, the scientists have been after Moon as well.
There are a number of theories regarding the origin of Moon. Each one has its merits and faults. One of the earliest modern theories about Moon’s formation was the Fission Theory proposed by George Darwin, son of Charles Darwin. He argued that Moon was a piece expelled from Earth while the latter was still in its rapidly spinning molten state. This theory was popular in late 1800s.
Other notable hypotheses are the Capture theory which states that the Moon was captured by Earth and the Accretion theory stating Earth and Moon were formed together. However, the most widely accepted theory of Moon’s formation is the Giant Impact Hypothesis. It was first put forward by Canadian professor Reginald Daly in 1940s. Later many scientists gathered evidence in support of this hypothesis.
According to GIH, the Moon originated as a result of collision between the Earth and a Mars-sized body named Theia billions of years ago. This collision produced a large amount of debris around the Earth, some of which accumulated to form the Moon. The Moon rotated about one tenth of the distance today, and gradually became tidally locked with Earth.
The Giant Impact Hypothesis has been able to explain some of the aspects of the Moon, like its angular momentum, the difference between the cores of two bodies. However, a number of conflicts have arisen challenging the Giant Hypothesis. One of them is the isotopic comparison between Earth and Moon. The lunar isotope samples show great similarities with Earth. It is against the belief that much of Moon’s mass came from Theia. Also the volatile elements in Moon are not being depleted as fast as they are supposed to be, considering the energy unleashed during the collision. More and more research is being conducted on the subject, and one day we might have the sufficient explanation.
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