Today’s factismal: The Moon is about 1/7th as large as Mars.
Imagine that you are watching the Solar System form, 4,600 million years ago; while you are at it, imagine that you’ve got a fast-forward button or this is going to take a long time to explain. As the nebula collapsed, it formed several thousand small globs of star stuff. Some of those globs were marginally larger than others, and so grew faster. The one that grew the fastest became our Sun and turned on a mere 100 million years or so after the nebula started collapsing. (Now do you understand why you’ve got that fast-forward button?) Others formed into small planets, like Jupiter and Saturn, or tiny planets, like Mars and Venus. But two of them formed into what would become the Earth and the Moon.
One of those developing planets (what planetologists call “planetismals”) is known as Theia…
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