If you're going to consider the possibility that there is other intelligent life in the universe, you also have to consider the time scales involved when thinking about how advanced they could be relative to us. There has been life on earth for many millions of years, but modern humans only for the last 40,000 or so. Farming didn't develop until around 10,000 years ago. So in approx 10,000 years we've gone from being hunter/gatherers to landing on the moon. Assuming we don't blow ourselves up, what we could we achieve in 2-3 million years? The possibilities are almost inconceivable. If there's a planet out there where intelligent life did evolve million of years ago there is really no telling what they might be capable of as far as space travel, etc. I like the time travel idea though, that's pretty good.I agree. Its very arrogant or ignorant maybe to think we are the only intellegent life in the universe. Its simple math. If our solar system (yes Earth is included) is one in 100 million that contains life, then life exists on 100 million other planets. I base this on the fact that there are 100 miliion stars in our galaxy and then there are as many galaxies in our universe each containing 100 million stars.
The problem is, everything is so far away that nobody could ever get here. This is the only reason why I don't believe in UFO's. Its just too damn far for any one to travel.
Perhaps, however that the UFO's are time travelers and not aliens! How cool would that be!