If it were just us. If we were the only ones to occupy the great expanse that we call the universe. If that our little blue spec in the ocean full of specs was the only one that had any sort of life; that we were the last ones standing in the mighty cosmos.
The thought just makes your stomach churn.
For some, the paranoids, the skeptics, this would be great news. We wouldn't have to worry about a world beyond are own and the inhabitants that would threaten us. We could consume the rest of our planet because we would know that we could travel untested through the rest of the black canvas that lies above us, and we could terraform and take whatever we found. We'd have the resounding feeling that this entire existence was created solely for us.
For others - and I hope most - it would leave a large feeling of emptiness. Because it would mean, without a doubt, that we are all alone. And it would raise the question:
What's the point?
What's the point if the universe is void of life except us? What's the point if we can travel to the far reaches of space, see it's beauties, but see no other life forms? What's the point of existing if our existence is shared beyond ourselves? Is there a point?
The vastness of space is beyond any kind of comprehension. Think of the largest number you know and square that number. Then square it again. Then again. Already lost? You should be. Space, and it's mysteries, are that big.
Right now are species is on the verge of something. Like some kind of calm before the storm - a moment were we all kneel down, crouch into a ball, and are ready to burst into something else. I believe were charging for something, some kind of answer. It's coming. You can feel it.
The question: Is there other life out there?
The answer: Well if there isn't, it'd be an awful waste of space, don't you think?
PS: Watch the movie Contact.