On the other hand I have seen a very few cases and video which pretty clearly show something--or somethings (they may not be the same phenomena) very strange.
I've also read Charles Fort and he and successors pretty well establish that every so often, very strange events occur on Earth--which are also very hard to explain. And I've read material on the Mothman (not well described in the recent movie), "Springheels Jack" and other outre phenomena...which makes you wonder.
That the "something" is little green guys in spacesuits interested in anal probing is open to question.
There are more things in Heaven and Earth than are dreamt of in our philosophy...
--Boris
Even if we're not, it's not very likely that they can get here.
Actually, what we keep finding, over and over again, is that our situation in the universe is not unique but ordinary. It is far more likely, more "ordinary" that we will find life wherever there is free water than for life on Earth to be unique.
If you see "Rare Earth" as an explanation for Fermi's Paradox, I think a more likely reason is the vast distances between stars.