How was the Moon formed?

The story behind the moon’s existence is still shrouded with mysteries. Until now, humans still don’t know its exact origins. Through time, many scientists have shared various theories about how the moon formed or where did it come from. Wondering about the moon’s birth has become a pastime for scientists and philosophers, resulting in debunked theories or existing hypotheses we have today.

First, among the different scenarios that explain where the moon came from is the Fission theory. George Darwin, the son of the naturalist Charles Darwin, proposed that the moon incredibly resembled the Earth. He said that this might be due to a scenario at some point in the planet’s history wherein the Earth might have spun too fast, and part of the planet whirled off into space. However, it was kept by Earth’s gravity and became its satellite.

The Fission theory also suggests that the chunk might have come from the Pacific Ocean. However, after humans got to the moon and its rocks were analyzed, it squashed the theory as its compositions were far from what makes up the Pacific Ocean. Thus, implying that the Pacific Ocean is too young to be the material that caused the moon’s existence.

The next hypothesis comes from the Capture theory. Based on this theory, the moon came from elsewhere in our galaxy, the Milky Way, which means the moon is an entirely different entity from Earth. It is believed that the moon was traveling past Earth when it got stuck in the planet’s gravity.

However, this theory is questioned as the moon could have easily broken free from the planet’s gravity. The former will cause significant changes in the latter’s gravitational pull. Thus, boosting the chances of the scenario. Moreover, both bodies’ chemical components are the same, implying that they have formed nearly the same time.

The third theory is the condensation theory or the co-accretion theory. The hypothesis suggests that the planet and the moon formed together while circling around a black hole. This postulation, however, lacks an explanation of why the moon revolves around the Earth nor the difference in their sizes and densities.

Giant impact theory is another theory that tries to explain the moon’s existence. In this hypothesis, it is believed that an object about the size of Mars collided with the still-developing Earth nearly 4.5 billion years ago. The said body was then named ‘Theia,’ which is also the name of the moon goddess Selene’s mother in Greek mythology.

When Theia smashed into the Earth, a part of the planet broke off and eventually developed into the moon. This hypothesis explains better, compared to the Fission theory, why the two bodies have similarities in their chemical composition.

However, the question is, what happened to Theia? It should make up around 60% of the moon’s composition. Experts then suggested that the Mars-sized could have been made of ice and melted to the Earth, or else, Theia itself has the same composition to that of the Earth. Thus, leaving no trace of its existence both on the planet and the moon.

Lunar explorations continue, and soon more lunar findings will fuel the neverending discussion about the moon’s origins.

More Readings:

Moon (Wikipedia)

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