Let's stick with what we know- there are billions of other planets and galaxies.
Now why? A YEC might have difficulty with that. But from a theistic evolutionist standpoint, it's simply a side effect of the Big Bang. How so? The universe displays homogenity. If God created our planet via condensation of stellar gases and matter into the sun, which eventually would get enough mass to undergo nucleosynthesis. One of the effects of GR is the prediction of frame bending. Naturally, as matter fell into the sun, SOME of it (in our galaxy, roughly less than 1 percent)would get caught along the orbit of it in it's angular momentum. These rings of matter eventually condensed then.
Seeing that what caused the sun and the other galaxies to condense was simply put, a lot of matter, why wouldn't there be the same effect IN ALL DIRECTIONS? The trait of homogenity would mean that if matter condensed in this portion of the universe, and likewise there's matter expanding in ALL directions, wouldn't all directions then evidence the same effect?
Now to say there's life on other planets- let's not get ahead of ourselves. If there is, God ordained it. I'm really a traditional Reformationist Christian- I believe that not a speck of dust falls without God knowing about it and God ordaining it. If there's life on other planets, God made it via natural processes.
The issue of intelligent life... I'm not going to solve a problem that we don't know exists. If there is, God made it. I don't ask the questions man, I just submit and obey.
TTYL Jesus loves you!
BTW, I read a book called The Five Ages of the Universe that went into great depth about this. It's EXTREMELY speculative, but an interesting read nonetheless. Actually, one of the authors is like a few years older than I. Man, I hope that when I'm 21 I'll be that smart. And famous. That'd be nice too.