Sending a few men to mars for a couple months is estimated to cost something like a half trillion dollars. So, what would it cost to send thousands of people to another star? I don't have a clue, beyond that it would be a large portion of the resources of the entire world for a generation. Whether or not that would be a good idea is open to debate, but it isn't gonna happen, at least in our lifetimes. Maybe they should figure out how to make my satellite dish work when it rains before attempting to colonize the galaxy.