My father believed in UFOs, and one of his friends claimed to have seen one as an Air Force test pilot.
As for me, I was of the opinion that UFOs were totally explainable by optical illusion, atmospheric refraction, etc, because I believed very firmly that there is nothing that isn't explainable by known technology (yes, a poorly founded and highly opinionated view, but in my defense, I was 12, and very into science.). This was long ago, back when the Internet was not really a thing, back when cell phones were brick-sized (early 90's).
One night, about 9pm, my father and I were building a deck awning in the backyard. Our house was on a hillside overlooking a southern california beach town, not out in the wilds. It was just an average night, clear, with the moon pretty bright. We were just gathering up the tools, a task made easy by the moonlight, bright enough to cast a shadow. As I reached for a hammer, I noticed I now had two shadows - one moving.
I looked over my shoulder, seeing the bright light, much like a full moon, only a little brighter - and moving fast. I yelled, loud, for Dad to look, and he did. It was about the same angular diameter as the moon, or a quarter held at arm's length. It was brighter than any full moon I've ever seen, though not hugely so. It was round when overhead, changing to an ellipsoid as it moved west (so I'm guessing it was the shape of a thick disk). We watched it move, very fast, east to west, then take a sudden dogleg to the northeast. It left no trail. We only had it in view for a few seconds, until it vanished behind the hills.
Whatever it was, its velocity was supersonic. Had it been small and low enough to be moving sub-sonically at that rate of angle change, it would IMHO have hit the hills. I've seen low flying fighter jets plenty of times, I know what a high subsonic pass looks like. This was faster. If it was high up, it was a lot faster. And there was no sound, none at all.
I was stunned. I could not even begin to explain what I'd seen. My father, on the other hand, only smiled as he said, "I've always wanted to see one," and then returned to gathering up our tools.
We often talked of that night in the following years. At first, I tried hard to rationalize it, to fit it in with my science-centered world view. I never could. Eventually, I came to accept it as my father did; a literal unidentified flying object, something we can't currently explain.
I know what I saw. I can still close my eyes and see it. I know too that I cannot come up with a scientific explanation for it (This was long before drones, in case anyone is wondering).
Was it aliens? Was it some secret government technology test (over a major population area?!?!? Not exactly conducive to secrecy...) Was it some as-yet unknown natural phenomenon? I have no idea, and I've finally accepted that I will never know. It wasn't easy.
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