I have found that one of the best ways to really get a feel for the sheer size of the universe is to play around with a program called Celestia. There are versions available for Mac, Linux and Windoze.
The program allows you to fly areound the universe at whatever speed you like. It is an awesome program. Try flying around the solar system at ‘just’ the speed of light. It takes foever to get anywhere.
Then make tracks to alpha centauri while increasing your speed to a mind-blowing 30 or so AU per second, which means you are travelling at a speed that will blow past pluto onece a second. You’d think you are really hauling ass, but even at ludicrous spped, you’re not going to get there any time in the next few days.
Until we discover some way around relativity, it just ain’t going to happen. A trip to even the closest star with a tiny unmanned probe would take decades. Anything bigger, or with people on board, would take generations, if it were even possible.