In 1908, an intense explosion occurred in the Siberian Wilderness. It measured in the range of a nuclear blast.
No one is sure what caused it.
Was it a meteor or comet strike? A brief, mathematically-possible intersection of matter and anti-matter? An alien space ship crash landing -- or self-destructing to avoid detection?
We don't know.
But I thought we might look at some potential doomsday scenarios today.