Never with absolute certainty, but a couple of things I’ve seen were pretty mysterious.
Once, I had just had a major shift in consciousness that morning, caused by a thought that I had and ran with (which I don’t remember now), and it was so strong that I remember feeling as though I could sense the shift everywhere, not just in myself.
Anyway, a little later on I went on a car ride (in the back seat), and I had been taking my camera everywhere I went just in case I saw something amazing, but that time I decided screw it, I probably wouldn’t see anything amazing and the camera was bulky to carry around, so I didn’t take it.
Then during the car ride, for no reason I remember I put my head out the window and looked straight up, and there I saw what seemed to be a silver sphere hanging perfectly still in the air, probably a few dozen or a few hundred feet up. My vision was slightly blurry so I’m not sure if it was a sphere shape, but it definitely stayed there perfectly still like nothing man-made does. I watched it for a few seconds, then put my head back into the car.. then a few seconds later I looked out again and it was nowhere to be seen.
Another time, I had heard that there are UFOs encircling the earth all the time, but they use technology that makes them invisible, and if you ask them to they’ll show themselves. So it was night time and I sent out a thought as strongly as I could requesting any UFO around to show itself, and nothing.. then, suddenly, the star (or what I thought was a star) that I was staring directly at, disappeared.