I've seen this discussed on several science shows and they all come down to an agreed theory; you'd have to bend the very fabric of space using a wormhole. They say it is technologically possible, but not with today's measures.
That being said, in reference to aliens and other habitable planets, they just launched some sort of telescope far more powerful than Hubble, and it has spotted what is called the "Goldilocks Zone". This is an area about a trillion miles away that has a system similiar to ours and there is a very good likelihood that there is life. Possibly not what we call life, but it might be anything from prehistoric animals to evolved animals or organisms.
This leads me to think: why haven't they contacted us if they are further evolved than we are, and are we threatened by them?
Maybe they aren't further evolved. Maybe they see us fighting with each other over land, religion, and resources, and are afraid we would take advantage of any 'friendship' they offer. If I were an alien and saw how humans treat each other sometimes I would be cautious about being our friend. If there are other life forms out there far more advanced than ours who wanted to talk to us, they are probably well capable of sending a message that we could understand. I think the video that I posted would make sense if it were too happen; that they would be able to figure out what we're saying and send an understandable response back, but I imagine they'd do it in a more sophisticated way than a crop circle....
Mission To Mars
I absolutely love this movie.