The universe is infinite and us, humans, have only explored the tiniest part of our solar system itself, let alone the milky way galaxy. We shouldn't believe that in the whole universe, we are the only living organisms. There is so much to still be explored and we cannot rule out any possibilities when we have not even gone beyond the limits. There is no legible evidence proving that there is alien existence. However, that doesn't mean that aliens exist or not. We simply won't know and probably won't in a long time. But at the very least, we should be open to continuous learning, even if it seems impossible.
If we evolved from life of monkeys then just like albinos mabye the samethings happend to aliens. What if to aliens we are the aliens what if we are the mystery. The great thing about life is we may never know what is real and not and nothing is ever 100% but that is no reason not to believe.
We live in a massive universe. There are an uncountable number of galaxies, each with many solar systems and planets. It is arrogant of us to assume that we are the only living beings in this universe. Most of the life we will find will not be like ET. Most of it will simply be bacteria or other simple organisms like that. However, there will be some that are complex like us.
While it is true that no conclusive evidence for extra-terriestrial, intelligent life has been discovered, when we compare that to the time-scale Humans have been using advanced technology for should we be asking if instead of when? Theoretically over an infinite amount of time we will discover intelligent life outside of this planet. Even outside of our galaxy. To say no to this argument is to be blind to the possibilities. Why shut things out when you can prepare for the reality? Now to understand the opposition it must be explained that for us to be around is nothing short of a miracle. It requires a process still not completely known to this day about the collateral nature of one-celled organisms in an ocean only described by professionals as "purple". The conditions on this planet have to be perfect, we are in what is known as the 'goldilocks zone' of our solar system meaning we are not too far from the sun to have temperatures plummet to inhabitable freeze, or the opposite in which we are too close for the temperatures to be too high. Also, let's not forget without our atmosphere we'd be just as inhabitable as the other planets in our solar system. After all of that has been established, we go back to the one-celled organism, which over an unimaginable, though not comparable to the universes life, amount of time the evolution process enables to create the biggest biological creation of all. The Human mind. Now taking all of this into account, let's not forget the bigger picture. Some of you will not believe in evolution, and that's not something I condone. I believe in freedom of speech. However, I do request that people keep an open mind. Even if it is for something you don't necessarily believe in. Having options and time never hurt anyone, and keeping an open mind is an incredibly strategic move not to mention wise. The bigger picture is (following the theory of evolution) we adapted to our environments over a long period of time. If the same one-celled organisms started to exist on another planet, why couldn't they evolve to their surroundings? How do we know alien life is not carbon based, how do we know it's not silicon based? Has no head and is a giant spike. Evolution creates the opportunity for an organism to adapt to their surroundings. Alien life is completely theoretically and practically possible. No reason to rule it out completely, only for the foreseeable future perhaps. Though my personal opinion? Discovering alien life is inevitable. Whether it is beneficial for the Human race? A different debate entirely.
Our universe is infinite, theoretically. How likely is it that our planet is the only one with intelligent life? I would say there's a very good chance there's another planet somewhere in the universe with at least some life forms, if not intelligent life like humans or other animals. With that knowledge alone, it should be theorized that aliens exist. Also, for what it's worth, there has been a decent handful of unexplained phenomena over the years. I'm usually pretty logical, but I certainly wouldn't rule aliens out in some of those cases.
Given that the universe is so unbelievably huge that we will almost certainly never discover it all, it seems highly improbable that we are alone. Recent estimates put it as one in five stars have an earth sized planet in the 'goldilocks zone'. I believe when our space telescopes are powerful enough we will find confirmation.
Also, these little chaps: http://en.wikipedia.org/wiki/Tardigrade are a highly interesting case study, they can survive the vacuum of space and reentry into earth's atmosphere. We also have not found a conclusive evolutionary origin to explain how they came to be.
If there are intelligent life forms out there on other plants then there won't just be 1 or 2 races, there would be thousands of even millions. Many of those races would be far more advanced than out technologically, if they existed we would know about it. Some would have already discovered the ability to travel successfully to planets on the other side of the universe.
By now we would have either been attacked, or something.
There is a probability for their existence but it doesnot make us need to believe in it, we dont need to believe, we may or not, so, we should not believe. We may spend our brain for more important thing than aliens. We need to say "it is probable" but we shouldnt believe.