Go ahead, open an umbrella inside today. We dare you.
That's because it's Friday the 13th, a day commonly associated with superstitions. Like the idea it's bad luck to open an umbrella inside. Or walk under a ladder. Or break a mirror.
Things might seem extra creepy today because it's the first Friday the 13th of 2013. With that much emphasis on the number 13, we must expect a little bad luck today...right?
The Christian Science Monitor notes, "Fears of Friday the 13th usually revolve around personal injury, but studies have shown no reliable relation between Friday the 13ths and rates of car accidents or other serious damages. However, a 1987 study by two finance professors at the University of Miami showed that you are more likely to lose in the stock market on a Friday the 13th, as opposed to a 'normal' Friday."
But researchers attributed the stock market conclusion to "the impact of the superstition on behavior," rather than something inherently unlucky about the day itself.
Triskaidekaphobia is the fear of the number 13.
The fear seems fairly prevalent. Some research suggests more than 80 percent of high-rises lack a floor marked 13.
What made the number so terrifying?
The Wall Street Journal offers a possible explanation: "In the Christian tradition, some people trace it back to the Last Supper, where Jesus shared the table with his 12 disciples. Judas, the disciple who betrayed Jesus before his crucifixion, is considered the 13th guest."
Mental Floss lists 13 reasons why people think the number 13 is unlucky, including this one: "Theres an old superstition that says if you have 13 letters in your name, youre bound to have the devils luck." Examples include Charles Manson and Jack the Ripper.
National Geographic mentions some additional explanations, including a Norse myth about 12 gods having a dinner party. An uninvited 13th guest showed up and things didn't turn out well.
National Geographic also offers a more technical explanation for the stigma accompanying the number 13:
Thomas Fernsler, an associate policy scientist in the Mathematics and Science Education Resource Center at the University of Delaware in Newark, said the number 13 suffers because of its position after 12.
According to Fernsler, numerologists consider 12 a "complete" number. There are 12 months in a year, 12 signs of the zodiac, 12 gods of Olympus, 12 labors of Hercules, 12 tribes of Israel, and 12 apostles of Jesus.
In exceeding 12 by 1, Fernsler said 13's association with bad luck "has to do with just being a little beyond completeness. The number becomes restless or squirmy."
We've established the case against the number 13. But what's so bad about Friday?
National Geographic explains it through Christian beliefs. Some people believe Jesus was crucified on a Friday. The article adds, "Some biblical scholars believe Eve tempted Adam with the forbidden fruit on Friday. Perhaps most significant is a belief that Abel was slain by Cain on Friday the 13th."
A fear of Friday the 13th is called "friggatriskaidekaphobia."
Discussion time: Are you superstitious?