Reflections on the Purpose and Size of the Universe

One of the things I've been meditating on lately is the universe, particularly: Is there other life out there, and if not, then what is the purpose of the universe being incomprehensibly "big".

First of all, let me just give a little background for those of you who have never studied how big the universe is...  Our Galaxy, the milky way, is one of millions in the universe.  Even if we could channel the science of Star Trek and travel at "above light speeds" (in a sense), we could never hope to physically explore more than a fraction of the universe.  Furthermore, the universe is bigger than we can even observe, and its constantly expanding.  To use theological terms, the universe is somewhat like a mystery... we can begin to comprehend its vastness, but there's things we just don't even know we don't know about it.

So why did God make a universe that is so big?  I have a few theories, and if you as a ready have others, or agree with one or more of these, please feel free to let me know.

1) Mystery: The reason God made the universe a mystery is exactly that--to give us something that will always be a mystery, even to the realm of science.  In some sense, it puts humans in their place, reminding us of how small, finite, and powerless we are compared to the rest of creation.  It helps us to be OK with mystery... we can keep trying to understand it, but ultimately, much like some of revelation, we must be OK with not understanding it completely.  It enables us to continually be amazed at the beauty of creation--it's nearly impossible to meditate on the universe and feel awe at its beauty and complexity.  Finally, this also helps us be a bit more humble.

2) A Purpose Unknown:  It's possible that the universe is so big because God has it purpose for it that we just don't even begin to realize.  While this is much like the first reason, this theory postulates that there is a reason beyond just being a means of exploration and beauty for the universe.

3) Other Life: This is the most commonly believed theory as to the universe, and it's the one that I personally struggle with the most.  As far as I know, the Church holds no definitive teaching about whether alien life exists, or even if believers shouldn't believe in it.  I remember reading something about JPII saying it was up to the choice of the believer, but don't quote me on that.  Anyway, I'm not sure where I stand on the issue.  I know C.S. Lewis, in his sci-fi space series, posits a very believable scenario in which alien life could exist on other planets.  Furthermore, from a statistical standpoint, it's very hard not think that intelligent life could exist on at least one other of the millions of planets in the universe.
      However...from a theological standpoint, it would seem that believing in other beings would compromise the state of human persons as the crown and center of creation, Christ's sacrifice for human's of all time, and our unique relationship with God.

I haven't made my mind up about reason #3, but the first two seem completely reasonable.  Am I missing anything?  No matter what the reason why the universe is so dang huge, it's still one of the most fascinating things in existence, and I will probably never grow tired of thinking about it.