Astrophysicists have shown that the universe is basically the same every where we look. The distant stars and galaxies are made up of the same elements that we know. If the chemistry is the same, it's likely that conditions on some planets will provide an opportunity for life to begin.

Not only are the elements the same throughout space, it appears that the physics are the same as we've learned. The ability to traverse the impossibly great distances of space would be a leap of knowledge that is far beyond our own technology, obviously. The ideas that have been proposed are worthy but far-fetched attempts, at least for now.

If I were religious, I'd find the enormous distances of space to be an important part of a creator's experiments in creating life. Each galactic Petri dish would be too far away from the others to cross pollinate and ruin each individual experiment.

Another idea is that given the really long history of the universe, perhaps interstellar civilizations don't exist at the same time so they haven't interacted.

My own belief is that the universe is teeming with life, most of which isn't what we call "intelligent." If there are species that are advanced enough to have interstellar transportation, they probably wouldn't be too interested in a civilization that burns fossil fuels.

All that I"m sure of is that we only have this planet to live on. We need to take better care of our home.