Here's my problem with UFOs.
"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." - Douglas Adams
Question 1: How far away are the aliens? Are they only a few light years away? If so, maybe - maybe - they have access to high-powered telescopes that can detect life here on Earth - if they're even looking in our direction. And why would they be?
If they're hundreds of light years away, then when they look into their telescopes, they're seeing the Middle Ages, or earlier. Why would an advanced space faring civilization want to go visit that era of human history? Or do they have some way to extrapolate the future of humanity to calculate the probability of where our civilization will be when they finally arrive?
Question 2: How far away are the aliens? Yes, same question. Assuming they saw us through telescopes (or whatever) and liked what they saw, and had a means to get here, then:
If they're only a few light years away, do they get here using some advanced sub light speed propulsion that gets them here in less than a lifespan? What are the chances of that happening? Why would they spend the resources to do that? And if they're that close, then why haven't we definitively detected them yet?
If they're hundreds of light years away, have they developed FTL? If not, are they using slower than light tech? Generation ships? Cryosleep? Why would a civilization spend such a huge amount of resources just to say hello to a random blue green world so very far away?
If they HAVE developed FTL, then how do they get over the "arriving before the event you're seeing in your telescope" problem? A civilization that is 100 light years from us looks through their telescopes and sees the year 1916. They go FTL, and arrive in 50 years - in 1866. This opens up a problem with FTL generally, but that's for another time.
So the ultimate question is this:
How does an alien civilization ultimately see us now and get to us now?
Even aliens could detect us and be motivated to visit, that time lag between what they could observe and what might still exist seems like an insurmountable obstacle to interstellar travel, no matter how that might be accomplished.
I have no doubt that aliens exist. As was twice stated in the surprisingly philosophical film,
Contact, if Humanity is alone in the Universe, it would be “an awful waste of space.”
Life and the evolutionary process must have taken place on billions of planets. Because chances of success fall within a very narrow band of environmental conditions, the millions of species which eventually rose to dominate their planets, I suspect, look a lot like humans.
I believe that intelligent species share a common form – bilateral symmetry, a brain container at one end, appendages protruding from an organ-housing body, and some sort of locomotive apparatus at the other end. How else could we all perform the Macarena?
I don't think that we have ever been visited by aliens. If any of the other planets orbiting Earth's sun once held intelligent life, they are not showing evidence of it now. Mars does not need moms.
Outside Earth's solar system, many species may have landed expeditions on other planets, but none have ventured beyond their own solar systems. As noted. the vast distances between Earth and other life-supporting planets, pose some serious travel restrictions, regardless of whether visitors would be motivated by mere curiosity or dreams of conquest. Although Humankind is not alone in the Universe, it is on its own here on Earth.
So, the bad news, as I see it, is that no super-intelligent, technologically advanced extraterrestrial beings are likely coming to save Humankind from itself. The good news is aliens are not on their way steal our water or round us up for dinner.
). The galaxy? Certainly. The Universe? Absolutely.
