Interstellar Ark ::
Strange Paths:

Fascinating maths and theoretical physics behind what might be done, and what is patently not going to happen (given our current level of understanding) in terms of interstellar exploration. Well worth a leisurely viewing.

On a side note, this might be the first case of accurate maths on /. although technically only the link is on there, but with one depressingly plausible alternative vision in the comments:

“If we do send an ark, and it arrives an odd 70 years later, the crew will be thoroughly pissed off. Because in the meantime, here on earth we would have invented Star Trek Physics ™ and can get there in half an hour. So they would arrive at a fully colonised Holiday Inn Resort Planet.”