The article referenced by the News bot above says that the odds of humans being the only life to have ever evolved is about 1 in 1E22. It then goes on to assume that this is such an absurdly large number that is must have happened at some point, but that number is not really so large from my perspective. 1 in 1E22 is about 1 liter (1/4 gallon) of water compared to the ocean (~1E22 liters or 2.6E21 gallons). This probability is equivalent to the same set of 6 numbers winning the Powerball lottery 3 times (Or the Germany Lotto has same order of magnitude). Now granted that seems like a highly improbable event, but you have to keep in mind this article is talking about over the entire time period of the universe (~13E9 years) and if you carry back the lottery drawings 2x a week for the last 13 billion years, it is certainly probable that the same 6 numbers have won 3 times (~54% chance). I think there is a reasonable chance we are alone in the universe just because there are so many factors that have to come together perfectly for life to happen.
Edited: Alchyrogue on 3rd May, 2016 - 7:27pm
Even if there is other intelligent life out there I think the only way we will ever see each other is if they are able to tunnel warp. Even going at the speed of light still takes a very long time to move from solar system to solar system.
As stated above, the distances are huge. Even our closest system α Centauri is 4.7 light years away. With a velocity of 20.874 Km/sec, we can reach it in about 134.991,5 years· or approximately 5400 human generations with 25yrs each generation.
Our planet is small, I mean really small compared to the others that have more to offer. Lets consider fuel as a resource in space. Why would even bother with earth when you have gas giants 20 or 30 times our size! We are insignificant but we think we're the center of the universe and nothing could be further from the truth. So there, that's the reason aliens don't bother with us. ;).
Photonics advances allow us to be seen across the universe, with major implications for search for extraterrestrial intelligence
Looking up at the night sky -- expansive and seemingly endless, stars and constellations blinking and glimmering like jewels just out of reach -- it's impossible not to wonder: Are we alone? For many of us, the notion of intelligent life on other planets is as captivating as ideas come. Maybe in some other star system, maybe a billion light years away, there's a civilization like ours asking the exact same question. Imagine if we sent up a visible signal that could eventually be seen across the entire universe. Imagine if another civilization did the same. Ref. Source 3r.
I like the theory of not being able to recognize aliens because they're on a different plane of existence or simply beyond our abilities to comprehend. We have five senses but whose to say there aren't more and that there are beings who move around like ghosts making us totally unaware they are there.
For me if there is a higher intelligence that is capable of being here from another planet or solar system then we would not know it. They would conceal themselves that well.
Even if there were aliens that had interplanetary technology that would not be enough to come from another galaxy if that is where the nearest intelligent life forms are coming from. Just like we can't reach them they can't reach us.
Maybe the only reason we exist still and haven't blown ourselves up is because of alien intervention. If they are smart enough to get there they are smart enough to remain hidden.