What’s a strange event you saw that later had solid evidence behind it?

The September 11 attacks fit that description for someone who watched them unfold on television. The plane impacts were recorded and witnessed by many people, and the physical evidence and investigations leave little doubt about what happened, even if the events felt unreal as they were happening.

I’d separate seeing something from knowing what it was. A person can be completely sincere about a strange sighting, but that alone doesn’t establish the object’s identity or explanation. The strongest cases have independent records that support the event itself, not just one interpretation of it.