It's an interesting conundrum isn't it?
If we accept that the universe is so huge that there must be intelligent life out there, then we must assume some is far more advanced than humanity. In which case, if inter-stellar space travel is possible then how come there is no evidence?
I suppose, we could be so uninteresting that it isn't worth the effort. It's pretty arrogant to assume we are anything other than insignificant tbh.
Or maybe it's because advanced species are careful about introducing themselves to underdeveloped species. I am not sure I buy that. We don't have a great history of more sophisticated civilisations being anything other than barbaric when dealing with the less developed, so I am not sure I would assume more advanced species will be anything other than complete cunts as well. Same rationale for time travel, btw. If it was possible, grandfather paradox or not, then some fucker would have screwed everything up by now.
More likely, is that inter-stellar travel isn't possible. Either Einstein's theories hold up for ever and nothing can travel faster than the speed of light. I am not sure I buy that either. Why should I? All theories are fine until someone finds some way to contradict them. Or talk of wormholes and bending space time is just theoretical discussion but practically impossible. I suppose if travel was that easy then aliens would be coming here for their holidays. Not sure I buy that either.
So, as I said, it's a conundrum.