From: San Diego, Ca.
There is a famous equation that gives the estimated possibility of life on other planets based upon star type, planets expected, and other variables. Sheldon (Jim Parsons) on Big Bang Theory went through the equation quickly in one episode.
That's all fine and good, but as far as aliens go, one has to ask, "Why?" Even if some alien species was far advanced of humans, and they could somehow manipulate space/time to travel faster than light or close to it, why would they come here?
There are billions of stars like ours in our galaxy. There is nothing peculiar about the Solar system that a space faring race would see from a distance to make them want to explore here.
True, if they could intercept our radio waves, which travel almost as fast as light, they would see a bug fat mess here on Earth, and maybe they would come, but we have only been sending out radio waves for a little less than one hundred years. That means the aliens would have to be within one hundred light years to know we are not just a rock around an average star.
We know that there are no similar radio wave coming from anything that close to us, so the galaxy is basically blind to our civilization. If that is so, why would any alien race farther away have bothered to come here? Note that the radius would only have been about fifty light years back in the 1950's and the Area 51 tale.
While it is likely there is life out there, there is little reason to believe that any of it is any more advanced than us, and that any of it would even bother to check out our star system for intelligent life.
You only have to ask yourself why would we want to go somewhere else and there's your answer. Exploitation expansion of the race into habitable realms beyond our current boundaries. Just to name a few.
History began July 4th, 1776. Anything before that was a mistake.