[geoschmo]

Originally posted by JurijD:
so the real question is: why hasn´t anyone done it yet) how come I don´t have a weird little green man for my neighbour... no wait I do.. at least the weird part

There are many possible answers to this question.

It's possible we are alone, although I think it's very unlikely.

It's possible that there are others out there, but none as advanced as us. Again, I think it's an unlikely possibility.

The most likely possibility I suspect is that your assumtions are overly optimistic. It may in fact be much much harder then you you think to travel between the stars. Without some major breakthrough that we can't predict or plan for, it's very unlikely that we will progress in 100 years to any sort of technology that will allow for reasonable travel times. If it takes centuries to get to the nearest star, then it becomes much more difficult to build ships that can stay together long enough to get us there alive. We aren't even sure yet how will overcome the damage to our bodies living in space for the few months it takes to get to Mars. Not even considering the prospect of our ships wearing out.

Assuming we can get there, you are wanting the people you sent to get right to work building another ship. This of course will have to be built entirely from local materials. Which means a lot of infrastructure work building factories and extracting resources, on top of whatever needs to be done just to survive in their new environment. What will be the impetus driving the colonists to send ships to another system? Wouldn't many of them be more interested in exploring their new planet and system? Making a life for themselves?

I am sure eventually they will get to the point of sending out another ship, but 100 years seems very soon to me.

If we do not make any sort of tremendous breakthrough in travel speed, I think it will be a very long time before we leave our own star system. For one main reason, why go? If you overcome the problems with living in space for long periods of time, and can build the size of ships that would be neccesary to send thousands of people to Barnards Star, why not build an L5 colony instead? Or a domed city on Mars, or an undersea city on Titan? There are a lot of interesting places to go right here in our own solar system. And there's lot's of room to expand. It will be quite a while before we run out of room. You could get your fill of exploring new and interesting places, and still be just a few months or years from mother earth.