If star travel was possible (it’s not), and if there were other sentient beings in the galaxy (there aren’t), they would have arrived, be arriving, and left calling cards everywhere in the form of self-perpetuating robots. The proof that there is no life anywhere else in the universe? Many would have by now had millions of years headstart to be here, and they aren’t here...
and just why would some alien come to this out of the way, backwater solar system on the edge of our galaxy and visit earth whose atmosphere could be hostile to them?
“if there were other sentient beings in the galaxy (there aren’t)” Having surveyed our galaxy and all 500 billon (at current count) galaxies, you arrive at the conclusion that none of the trillions on trillions of planets have intelligent life; just amazing!
Alternately, we are the Elder Race. Or the Great Filter is REALLY rough to pass. . .
That's an unsupportable assumption. I've read various articles which assert that the conditions that made life on planet earth possible are quite unique, and the chances of them being replicated elsewhere are pretty low.
If I recall correctly, they have identified about 20 factors that are somewhat unique to our solar system that made it possible for the Earth to develop advanced life, not the least of which are the presence of our Moon, and the presence of Jupiter.
They say without the moon, our planet would remain frozen over in a perpetual ice age. They say without Jupiter sweeping up the solar garbage, the planet would have been bombarded to death.
We may be alone or mostly alone in the Universe. While it may be possible that there is life out there somewhere else, it may in fact be well behind us in development.
Of course there are enough plausible UFO stories out there to make me suspect that there may be advanced life that has cracked the distance transportation problem.