Humanity has existed for a couple hundred thousand years, or so scientists believe, with civilization thought to be somewhere in the neighborhood of 5,000 to 6,000 years old. For the entire time, we’ve looked up at the Moon and wondered where exactly it came from and why it’s been hanging around for so darn long. Theories have come and gone, but there hasn’t been any definitive proof to ultimately quiet the debate. That proof might come when China and other nations head back to the moon to perform various tests, but in the meantime there’s a new potential explanation for the Moon’s existence, and it’s based on an idea that was once largely dismissed. 

In a new paper published in Nature Geoscience, a trio of researchers have revived an old theory that the Moon is actually the product of many small collisions between an early Earth and various “impactors.” These impacts would have knocked some of Earth’s material skyward and into orbit, eventually coalescing into a single sphere. The creation and eventual merger of these so called “moonlets” would have occurred over a time period of roughly 100 million years.

The researchers ran hundreds and hundreds of computer simulations to generate examples of a newborn Earth colliding with other objects, and eventually forming a natural satellite like the Moon. The results showed that approximately 20 such impacts would be needed to produce the amount of space-bound debris that the Moon is comprised of.

Up until recently, many scientists backed what is called the “single impact hypothesis,” which suggests that the Moon was the product of a single large collision between the Earth and other celestial body. However, because the Earth and Moon are so similar in their makeup, this theory has been steadily losing ground. This revived multi-impact theory would go a long way towards explaining why the Moon appears to be made up of essentially the same material as Earth.

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