Just imagine a culture with technology so Advanced they could make it across light-years. Currently I think the fastest we can get a ship to go eventually is somewhere between 30000 and 60000 miles per hour. I think I did the math one day and it was 86000 years to get to Proxima Centauri or something along those lines maybe it was only eight thousand years. In any case, you would need a drive that approached light speed in order to get anywhere in any reasonable amount of time.
as far as our earthly understanding of physics goes, it's not even remotely possible for an object to travel at light speed. bar all technological problems, it just isn't theoretically viable. but if you could, say, get a ship to run at speeds we can't comprehend (even half of light speed is incomprehensibly fast), the biggest obstacle in making it across a light year would be fuel. that's where pretty much any idea of actual explorative space travel starts to fall apart.
I am sure that other intelligent life exists out there. there are just too many planets for none of them to have anything. but I'm also sure that they're all too far apart to ever interact with us under any circumstances. it's a shame, really.
I hope that somewhere out there there are two earth-like planets close enough together to interact with each other. maybe even observe us without being able to reach us like a better hubble telescope. that would be cool. not that I'll ever know.