^ Since an UFO in the meaning of not-man-made represents unknown technology (if technology at all), that is a far-fetched conclusion.
Maybe space travel must be more thought in terms of travel by mind. The outer space seems to be unfinite, the inner space seems to be infinite. That begs the question whether both spaces really are two. Or even can be two at all - if both are infinite.
Another scenario not to be ruled out is that we find ways to move our mind from biological hardware into mechanical, more endurable hardware. Many astronomers and physicists assume that for this reason most civilizations, if there are any - I am not convinced - , are not inhibited and formed by biological but technological entities. Robot civilization, to put it simply.
Our own AI experiment has an unknown outcome. Nobody can rule out that we as biological creatures will not survive it.
What is mind? What is space? Whats the difference, in the end? Where did it all began? Did it began at all? And whatever the answer may be - why was/is it so? Why is there simply not just nothing?
Our sciences tell us to be specialist idiots. Maybe we dont see the forest for all the trees.
And maybe the forest is not friendly.
When I was young, I was a big fan of scifi scenarios about colonizing other planets, and exploring space. But today I think this cold black vacuum is just lethal and hostile to any life, travelling into it holds no more attraction to me, and the idea that man will survive as a species only when colonizing other planets and bulding new civilizations there - borders insanity to me. Not to mention the principle question whether that is really desirable.
If we do not learn to have a peaceful mind we cnanot carry a peaceful mind to other stars or planets, only our old inner flaws and the same old conflicts.
Consider you reach Mars. What would you do there, eh? Only one thing you could find out there: how damn far away from your real home you are. Living in a container - is not attractive. And when we cannot even manage our own home planet to clean its atmosphere and pollution - how can we dare to dream of terraforming the atmosphere of another planet...? Our forefathers build big cathedrals, but building these were measured in generations, in centuries sometimes, the whole cities around them evolved and grew dramatically in that time. Who today still thinks and lives in such time scales?
Nobody.
Little boys at child play. Thats why Musk and Trump get along so well with each other. They play like little boys on a school backyard. And they cant look beyond its fence. Elon plays the astronaut, and Donny is Captain Nemo. Two 8 year-old who dont grow up and get entangled by their fantasy. Lovely.