A huge question in the world of Science, and well all areas in life; is there intelligent life in the universe? There is of course much dispute to this point, between religious groups, between scientists and even between the averages Joes out there. I myself am of the view that there is almost a definite chance of not only life in the universe, but intelligent life.
Why? Well, let me start by explaining a few things about the universe in a very basic way. The universe is constantly increasing in its size and is thus infinite in its size; the observable universe is a sphere with a diameter of around 92 billion light years, one light year is about 6 trillion miles/10 trillion kilometres. And that is just what we can view with our limited capabilities. Within the observable universe there is estimated to be more than 100 billion galaxies, and each of these galaxies is estimated to have between 10 million and 1 trillion stars in. All of these huge, mammoth numbers points towards an enormous amount of planets, and even a huge amount within the Goldilocks Zone (read about that here: http://en.wikipedia.org/wiki/Goldilocks_zone#Goldilocks_zone)
What am I really getting towards here? Well with such a massive amount of galaxies, suns, planets, there too has to be life. No matter how minutely small that chance is, with such a gigantic number of planets, the maths points towards it being inevitable that at least one of these planets has developed life. And this is just in what we can currently see, which, if the universe is infinite is practically 0% relative to the entire size of the universe, so surely there's practically a 100% chance of life.
If life has managed to evolve, survived every obstacle the universe can throw at it, and managed to reach the point of evolution we're currently at. Say that their planet was formed a billion years prior to ours, that would mean they would be a billion years more advanced than us (we'll most likely have all died from war by this stage, but you get the picture...). They could, potentially, be able to travel at the speed of light, uncovered the mysteries that lie within black holes and perhaps even found a unifying theory to the creation of the universe.
We often forget that the beginning of our life, our ancestors lives and even our planets life was not the dawn of time. Far from it in fact. The universe is approximately 13.7 billion years old; the Earth however? Just 4.54 billion years old. So it is very possible that we are far less technologically developed than aliens.
"We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet." - Stephen Hawking. Which is very true, aliens are unlikely to come to us searching for much else than harvesting our planet for it's resources and then moving on.
I hope this has given you some food for thought, just a small side note; I do not believe aliens have ever visited Earth, if they had I'm certain it would be on a huge scale. I believe it would be much like when America was "discovered", the indigenous population were driven out.