We aren't even entirely sure where the belief comes from, although some assert that it comes from there being 13 people present at Jesus' last supper, and then he was crucified on Good Friday.
That seems full of holes to me, since the idea of Friday the 13th being unlucky dates to maybe the 19th century... not the time of Christ.
The whole thing, though, does cause one to wonder why we — as a species — seem to fascinated with calamitous disaster scenarios. Makes me me want to just ask the disaster mongers what they believe they will have, if their scenarios come to pass.
