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Originally Posted by irpq11
:upset: So where did the moon come from? If the earth doubled in size, then the moon at some point was only half the size of the earth, so surely the moon wasn't split of of the earth?
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Well I thought about this as an argument to debunk the growing earth theory, but the more I thought about it, the more I felt it was
possible to fit it into this theory. The most prominent moon creation theory is the concept of a mars-sized meteor colliding with the primordial earth to expel a large amount of matter into space, which then formed the moon over time.
Initially, you'd think "if the earth was so much smaller back then, wouldn't a mars-sized collision cause more damage?" but really, if the earth had roughly the same mass it does today, the collision would have the same momentum effects (Newton's second law of motion). Also, if the matter was much more dense back then, the earth would need to expel a smaller volume of it to form the moon. So realistically, even though the earth was half its current size, it still could have given off the same amount of mass to form the moon, though not the same volume of matter. The molten material would have cooled much quicker in a smaller package, and so it expanded faster to reach the size the moon is today. Since volume and density have nothing to do with gravity, this concept could work.