Our Moon

[Ninurta]

 Without the moon, we , humans, would not be possible. Life itself would probably not be possible. 

I believe life WOULD be possible - it just would not have been able to start in the was science (with so far no evidence) says it started. Their theory requires tides so that non-living minerals can suddenly magically combine and organize themselves into living ones.

I have always wondered why the moon is the perfect size to cause solar eclipses.

I think you mean annular solar eclipses, where the sun's corona is just visible around the eclipsing moon, but the sun itself is not, meaning that the moon and the sun are both the same visual size from Earth. That is an accident of the times we live in. The moon, as it orbits the Earth, is slowly moving away from Earth. Millions of yers ago, it appeared much larger in the sky because it was a lot closer. Millions of years in the future, it will not appear big enough to eclipse the entire sun. Right now, it is at just the right distance.

Why does it spin on it's axis at the same rate as it orbits the Earth, only showing one side? 

That is called "tidal locking", and is an effect of gravity between two co-orbiting bodies. Tidal effects slow the bodies down until the time comes when they achieve a resonance. This happens to the smaller body first, as the effects of gravity tend to be stronger on the body with less mass. The same tidal effects are acting on the Earth, but much more slowly because the planet is much more massive. The effect it has on Earth is to lengthen the day as the planet's rotation slows down. It's on the order of microseconds per year, but over enough years it adds up. During the time the coal fields were forming, the length of a day was around 18 hours I believe, rather than the current 24 hours.

Mercury is also tidally locked to the sun, and keeps the same side sunward all the time. Venus rotates "backwards" from what the rest of the planets do, and has a day that is longer than it's year. Now what the hell is up with THAT?

.