Originally Posted by Deathmetalconga
Not only does immense distance separate worlds, but immense stretches of time. Sentient life has existed on earth only for a tiny fraction of its existence and we may never attain interstellar travel. Sentient species may pass each other in the night, out of synch by millions of years. That's just a blink in the time span of the universe, but serious evolutionary time.
There have been numerous proposals discussing the idea of sending deep-space probes to nearby star systems. Unfortunately the technology does not exist to do it in a human time scale. Such probes would need future or near-future technology to be able to travel at the speeds required - then you have to worry about the difficulty of transmitting meaningful data from spacecraft at least several light years away.
Add a human into that equation and you've got a whole host of other problems. A mission to Mars is viable with modern technology - in fact one of the biggest problems is shielding manned missions from solar radiation. Various studies estimate that the risk of cancer developing in an unshielded spacecraft (to one individual) is around 30%. We have the technology to counter that risk (plastics and water shielding) that would work but also add to the weight of the craft, which makes it much harder to launch. Taking humans any further than Mars is not out of the question but it would be very difficult as it currently stands.
With that said, there's no reason why other life forms couldn't have developed the technological solutions - but the chances of different life forms intersecting in time (and space, indeed) in our local area are remote. Certainly not impossible - but remote. We're much better off looking for radio transmissions.
As for Roswell? I've never seen enough to convince me of extraterrestrial origin. There's a lot of hearsay - but that's what I treat it as. I'm naturally skeptical and this hits all those buttons. Not enough hard data.