Are there UFOs, of course things flying about that cant be identified
Are there aliens buzzing earth, I doubt it very much
The scales of space are mind bending, Imagine standing in a desert as far as the eye could see in every direction, every grain of sand is uniform in every way, I have buried a single black grain of sand somewhere, that's our solar system, now try and find it. What if that desert you stood in was a cube a hundred miles in its 3 axis? Could you find us?
Even if you could find us, travelling the insane distances in a meaningful way would involve using technology that's at our most wildest dreams and would use amounts of energy that are beyond our comprehension, even if we could get to 90% the speed of light (and a ships mass would be insane at this speed) your still talking many years just to get to the next star, hitting a grain of dust would be equivalent to a 1 gigaton nuclear weapon explosion.
So if any species had the technology to find us and travel to us we would be the intellectual equivalent of bacteria to them.
In my nerdy youth i did some rough calcs on star trek, in the time it would take Mr Worf to say "The Klingons have come out of warp captain" and Picard to say "Take us out of warp me Warf" they would have over shot them by 13 billion (or was it million
) miles at max warp. And thats ignoring how do you actually monitor where some one is when there travelling millions of times faster than light.
On the up side the probability of there being life on another planet is very high since theres so many of them