Today's Number: Why Do So Many Consider 13 Unlucky?

Are you superstitious? Do you believe the number 13 is unlucky?

You are not alone. And, since today is Aug. 13, you might want to avoid crossing in front of that black cat slinking around the neighborhood.

Here are some of the reasons why people consider 13 unlucky, courtesy of Mental_Floss.com:

1. There were 13 people at the Last Supper. It’s said that Judas Iscariot—the one who betrayed Jesus—was the 13th man to take his place at the table.

2. Similarly, there’s a Norse legend that has 12 gods sitting down to a banquet when the 13th (uninvited) god, Loki, shows up. Loki killed one of the other gods, which led to events that eventually resulted in Ragnarok — the death of a bunch of gods, a slew of natural disasters, and the eradication of everything on earth save for two human survivors. There’s a lot more to the story than that, but you get the general idea.

3. Let’s go back to Christianity for a moment. Many Christians believe that Jesus was crucified on Friday. Researchers, however, believe that it wasn’t a case of Friday the 13th lore—it was possibly something like Friday, April 3, 33 A.D. But that doesn’t mean the 13th is off the hook. Many Christians also believe that the Cain and Abel debacle took place on that date.

4. Traditionally, there used to be 13 steps leading up the gallows. There’s also a legend that a hangman’s noose traditionally contained 13 turns, but it’s actually more like eight.

5. Apollo 13 is the only unsuccessful moon mission (intended to get men on the moon, anyway) thus far. An oxygen tank exploded and the survival of the astronauts on board was pretty touch-and-go for several days, but they did all come home safely in the end (but you already knew that).

For the full list of 13 reasons why people consider 13 unlucky, click here.