Question #5. Where did the Moon come from?

This is a good one. I really enjoy the mental imagery that comes along with this.
There are a few theories for this one but there is only one that makes sense to me and I honestly don't understand how the other theories can have any amount of support if they are being considered rationally. One theory is that the Moon formed independently of Earth in an Earth orbit during the formation of the solar system, another is that the Moon formed independently of Earth elsewhere in the solar system its formation and was captured by Earths gravity well and settled into a stable orbit. I don't subscribe to either of these theories.

The giant impact theory was presented in 1984 at a lunar origins conference in Kona, Hawaii. The giant impact theory matches a lot of the data currently held about the Moon and Earth while the two other theories I mentioned before raise some questions. Questions like, if the Moon formed separately from Earth elsewhere in the solar system why is the Moon and Earths isotopic composition so similar while every other body in the solar system has an isotopic composition that is significantly different to any other solar body. The simultaneous formation theory does not allow for the angular momentum of the Earth Moon system.

The giant impact theory raises its own questions and whilst the answers may remain somewhat elusive, they do not definitively rule out the possibility of the theory. The theory itself suggests that during the formation of the solar system there were several rocky bodies that formed in the inner solar system. They were all of a similar size and composition but two of them formed quite close to each other and their orbital paths brought them into direct contact with each other. They collided. A massive planet sized crash in space between the planet we now know as Earth and the theoretical planetary body that has been named Theia. The impact of the two planets smashing together caused a certain amount of matter from both planetary bodies to be blown out into the surrounding space. Some of the matter would have been pulled back to the planet but the matter that that was blown out into space far enough to not be pulled back by the gravity would have just kinda stayed there. It would have spread itself around the planet much like the rings of Saturn and gradually over time gravity would have gathered it all together into a neat little ball in a nice stable orbit around the planet that was born from two planets that came together and made another smaller one. (And so began a pattern!)

This theory adequately accounts for the similarity in the isotope composition and how the Moon has an established stable orbit with one side permanently facing the Earth. It is also considered possible that the collision was the cause of the axial tilt of planet Earth that is responsible for our changing seasons. It is most likely that Theia would have impacted Earth from a wider orbit than Earths which would not only have forced Earth closer to the sun by the impact alone. Theias gravity well is now combined with Earths, the Earths mass has increased and orbit shrunk again due to the disappearance of Theias gravity well on the outside of Earths previous orbit.

Earth is in a unique position now, the increased size and mass helps to stabilise its solar orbit, it has a large gravity well for an inner planet and it has a satellite forming around it. Honestly, the Earth has no business being here at all.
The Moons formation adds even more stability to the planet as it acts as a kind of anchor maintaining that angle of axial tilt. The Moon has also been Earths protector over the eons. A last line of defence if you will, against asteroids, comets and various other interstellar debris left over from the creation of the solar system. The Moons presence has been invaluable ever since the collision blew it out into space in tiny bits.

As I mentioned before, the earth has no business being here. No business being here in this orbit. It's too big for this orbit, had the collision not occurred the "Earth" would be a much smaller, dry, rocky, lifeless, planet. Like its neighbours. But the Earths size and mass were boosted which in turn increased the Earths gravity well. Add in the mass from the moon debris and Earth is like a magnet in the early eons of the solar system. No other inner planet has a gravity well like Earths gravity well and the Earth makes the most of this.

Just as the earth has no business being here, water has no business being here either. You see, during the formation of the solar system you basically have all of the elements in varying quantities spinning around like they were in a giant inverted centrifuge. All of the elements arrange themselves in order from the focal point of force by their mass and density. Liquid water does not belong here. It is only here now because of the increased mass and gravity of the newly formed Earth and Moon system. As the solar system began to settle down into some semblance of order there were still countless asteroids and comets spinning around trying to find their place and had the new Earth not been there as it was, their place would have been in the heart of the sun. But the big rocky Earth and Moon became a gravitational focal point in the inner solar system, the Earth and Moon sucked them into their big gravity well and kept them. Those asteroids and comets were from the outer solar system and comprised mostly of frozen gas and liquid, which included water. So not only has the Moon protected the planet since its creation, its creation is the reason why there is something here to protect.