it keeps coming up-how can they travel such great distances? that and how the ufos can fly in ways that defy inertia Obviously they have discovered a way to do it, a way that Newtonian physics can't accept.
It's the same old line-we have discovered all that there is and anything more is fantasy. Some of these ppl have been around a million years before us.
I don't think serious physicists believe we have learned everything there is to know. We know that we do not have a complete theory for how the universe works because we cannot reconcile both quantum mechanics and general relativity. It is one of the most pressing problems in physics. What I hear is that given what we know, we have no idea how these things would work. Some are naturally skeptical given what we do know, and of course some use that to claim they are impossible. Which is what I think you are referring to. There are people like Michio Kaku that do not rule these things out. And even those that deny uap/ufo visitations do not think we know everything, they just dont see how they are possible so cast assertions about that - which I think shows both hubris and closed-mindedness.