It is not only Americans who consider this number to be unlucky. People around the world have what are called superstitions about the number thirteen. Superstitions are popular beliefs that are not based on reason or science. A person believes something brings good or bad luck. The fear of the number thirteen is called triskaidekaphobia.

This fear is so strong around the world that many tall buildings do not have a thirteenth level. And, many airports do not have a gate numbered thirteen.

Some experts say fears about this number come from ancient religious stories. One Norse myth is about twelve gods who were having a party in their heaven, Valhalla. Loki, the god of evil and disorder, arrived at the dinner party uninvited. He became the thirteenth person at the table. Loki then helped cause the death of Balder, the god of joy.

In the Christian book, the Bible, Judas is the thirteenth guest at the dinner called the Last Supper. Judas is the man who betrays Jesus, leading to his death.

Many people around the world also consider Fridays that fall on the thirteenth day of a month to be especially bad luck.

Thomas Fernsler is an associate policy scientist at the University of Delaware in Newark. He is also known as “Doctor 13” because of his interest in this famous number.

He says numerology shows that thirteen suffers because of its position next to the “complete” number twelve. He notes there are many sets of twelve, such as twelve months in the year and twelve signs of the zodiac. Mister Fernsler says thirteen is one more than twelve which makes it what he calls a “restless” number.

Thomas Fernsler can tell you many interesting facts about the number thirteen. He can tell you that if February has a Friday the thirteenth in a non-leap year, March and November will also have Friday the thirteenths. Mister Fernsler can also tell you many examples of good and bad events that have taken place throughout history on Friday the thirteenth.

But do not worry. The only Friday the thirteenth this year will take place in June.