Larc, I think you're questions are pretty narrow minded......you're asking these questions with OUR technology in mind.
How long does it take to travel from New York to London? On the Concorde, it takes 3 1/2 hours. How much food would you have to supply to get there? Well, I figure each passenger probably gets a few drinks and one meal.
Now; go back in time 300 years and talk to someone who traveled from England to America. How long did it take them to get there? Probably 2 or 3 weeks. How much food did they have to take? Well, lots. Enough for each person to eat 3 meals a day for 2 or 3 weeks.
Try explaining to these people who lived 300 years ago, that you had the technology to cover the same distance in only 3 1/2 hours and you only needed one meal. They simply couldn't comprehend such a thing and would probably have you burnt at the stake.
Just because mankind hasn't developed the technology yet to travel great distances in space, doesn't mean it can't be done or that another civilization hasn't done it. I saw Stephen Hawking on a documentary a while ago, talking about the possibility of space travel. The jest of it was: if you could create or use a wormhole in space, travel to distant planets would become a reality. Obviously, we have not developed the technology yet to do such a thing, but like I said: that doesn't mean someone else hasn't.
Assuming that we are the only one's in the universe is parallel to the Catholic Church's midevel belief that the earth was the center of the universe.