I remember when, many years ago, I saw a UFO. I was spading the garden, and taking a break, I thrust my shovel into the soft earth and looked around. I was near the pear tree, where hung the wren's nest box, so I looked to my left to look for the wren that I'd noticed coming and going earlier. I watched her enter the nest box with an insect that she'd found, then after feeding her brood, fly off again.
I looked forward again, and there was the UFO, hovering in the air in front of me, close enough to touch if I only dared to do so. I'd heard of UFOs darting about in the sky, but this one hovered motionlessly just two feet in front of me.
It looked like a wooden ball about an inch and a half in diameter. I suppose some would have looked for little doors or windows for the tiny aliens. Still others might have looked for the face of Mary; but I just stood there pondering the laws of physics.
I remember seeing tent caterpillars hanging from invisible threads, but they swayed in the breeze. I guessed that a wooden ball that size would be too heavy for one of those threads; but nonetheless, I looked up. No, the pear tree was too far away, and there wasn't even a cloud to hang the ball from.
I would have to experiment a bit to figure this out. I passed my hand over the ball, then under it, then on its left and right, as though slicing a box of air around it. So far, the wooden UFO hovered undisturbed. There remained just two sides of the 'box of air' to be checked: in front and behind the wooden UFO.
As I sliced the air behind the UFO, it was quickly obvious what the 'flying object' was, and immediately it lost its 'UFO' status. The wooden ball was the tip of the handle of my shovel that I had thrust into the soft earth in front of me, and had forgotten. The round end of the handle was two feet away, but the blade of the shovel was about seven feet away and thus out-of-focus. The handle of an old-fashioned shovel has a slight bulb-like swelling of its tip, so that the shaft cannot be seen behind the tip even when the shaft is not exactly pointed toward the observer's eye.
To get the above photo, I reconstructed the scene by thrusting an old shovel into a strip of spaded ground between our lawn (on the left) and the neighbor's fence (on the right). If I were more adept with advanced camera settings, I might have made the background more out-of-focus, to simulate what the eye sees. But instead, I found an angle where the shovel blade is hidden behind the much-closer tip of the handle.
What if I were not so cool and patient in my reaction, but instead had panicked and ran away without investigating? Then the object might have remained a UFO forever. But it is also possible that an explanation of the observation as the tip of the shovel might be discovered later. Lacking the experiments that I did which confirmed that it was the shovel-tip, this explanation would be essentially theoretical, although it probably is the only plausible explanation.
Some people believe that observations of UFOs prove something, but that is not logical. Until you have an identification or an explanation, nothing can be proved. You simply have a question with insufficient data to get an answer.