The Universe is infinite. We need to be infinitely naive to believe we're the only ones out there.
What makes you think that there is only one universe? Have you not heard of the parallel universes theory? What is before being born and after death? Time itself is a fascinating subject, as its not as constant as some people may think... They say before the big bang time wasn't even moving.
There is also the Fermi paradox, you should all get acquainted with it. We might very well not be alone, but unable to meet. Because the distances... time and resources required to develop interstellar travel, and never forget, relativity of time, this is more important than you may think, people living in different celestial objects won't have their time in sync, to some, we come and go in the blink of an aye, and to others its the other way around.
I think some sci-fi shows and novels have tried to explain this time dilation business, but it isn't easy to grasp.
Remember what i just wrote above about time?
Time perception changes with speed relative to other objects. Everything in the universe is moving, away from each other, orbiting larger celestial objects, each have their own relative velocities.
Even if we were to somehow establish an interstellar colony somewhere, the time to them would pass different tot he time of those who stayed on earth. It might not look too different for a close colony, say, in Mars, but start settling in Proxima Centauri and things will start getting funny, assuming you can somehow overcome the traveling there and communications thing.
Most people explain time relativity with the usual man made ship going near light speed, but time elasticity does occur at slower speeds, even people flying in planes have their time different than those on the ground, but its too small to notice. Astronauts have it a bit more measurable, but still too little. Keep getting father and farther, and the difference will start to be noticeable. Go interstellar... Go even beyond that.
For us too, we are looking at the light of death stars, the information that we are observing here took so long to travel that over there is different. Zoom enough into space and you get to the origin of the universe (a radio telescope picture of the past was already taken by a man made satellite).
And yet, this is but a particle of sand dust in the vast ocean of space... Our little human minds might never be able to comprehend.