Why is 13 unlucky? From Friday the 13th to buildings with no 13th floor

In the United States, Brazil and many other countries, the dreaded day is Friday the 13th. In Spain and much of Latin America, the saying goes «On Tuesday the 13th, don’t marry and don’t set sail.» There are hotels with no room 13, buildings that jump from the 12th floor to the 14th and airlines with no row 13. The fear of the number thirteen even has a scientific-sounding name: triskaidekaphobia. But where does the superstition come from, and does it have any basis?

The perfect 12 and the awkward 13

One of the most common explanations is that 12 is considered a «complete» number in many cultures: 12 months in a year, 12 signs of the zodiac, 12 hours on a clock face, 12 apostles, 12 Olympian gods. Thirteen would break that harmony, the one left over.

Two often-cited stories add to this. In Christian tradition, there were 13 people at the Last Supper, Jesus and his twelve apostles, and the one who betrayed Jesus, Judas, is often described as the thirteenth guest. In Norse mythology there is a story in which the trickster god Loki arrives as the 13th guest at a banquet of the gods and causes the death of Baldr, the god beloved by all. From these grew the old superstition that seating 13 people at a table brings misfortune.

Why Friday, or Tuesday?

In the English-speaking world, Friday already had a bad reputation: in Christian tradition it is the day of the crucifixion. The specific combination «Friday the 13th» as an especially unlucky day appears to be fairly modern. Historians find few references before the 19th century, and a 1907 novel titled Friday, the Thirteenth, by the American Thomas W. Lawson, helped popularize it. Much later, the horror film series of the same name turned the date into a global phenomenon.

In the Spanish-speaking world, Tuesday (martes) is named after Mars, the Roman god of war, and for centuries it was associated with violence and destruction. Some also link it to the fall of Constantinople to the Ottomans, which happened on a Tuesday in 1453, although it is hard to know whether that event shaped the saying.

The mass arrest of the Knights Templar, ordered by the king of France and carried out on Friday, October 13, 1307, is often cited as the origin of the superstition. The date is real, but the connection to the popular belief is a modern explanation and has not been proven.

Buildings with no 13th floor

In many buildings in the United States and elsewhere, especially hotels and apartment towers, the elevator buttons skip from 12 to 14, or the 13th floor is relabeled «12B» or «14». Some hospitals avoid room 13 and some airlines have no row 13. The floor still exists, of course; it just gets a different name because some customers feel uneasy.

Apollo 13: the most famous coincidence

NASA’s Apollo 13 mission lifted off in April 1970 at 13:13 Houston time, and an oxygen tank exploded on April 13. The astronauts had to abandon the planned Moon landing and made it home safely in one of the most celebrated rescue efforts in spaceflight history. For the superstitious it was proof; for the engineers, the cause was a technical fault in the tank that had nothing to do with the number.

What do the data say?

A few curious studies have been carried out. In 1993 a paper in the British medical journal BMJ compared hospital admissions from traffic accidents on Friday the 13th and Friday the 6th, and found more admissions on the 13th. However, the sample was tiny and the authors themselves presented it with a touch of humor. Later analyses, such as one by a Dutch insurer in 2008, even found fewer accidents on Friday the 13th, perhaps because superstitious people are more careful or stay home. Overall, there is no solid evidence that 13 is actually dangerous.

A lucky number elsewhere

Number superstitions vary by culture. In China, Japan and Korea, the number people avoid is 4, because it sounds like the word for «death»; many buildings in Asia have no fourth floor. In Italy the traditionally unlucky number is 17, while 13 can be considered lucky. In some cultures, 13 is even linked to fertility and the lunar cycle, since there are roughly 13 lunar months in a year.

So, should you get married or not?

If you are superstitious, nobody will force you to move house on Friday the 13th. But if you are offered a good price to hold your wedding that day, statistics give you no reason to worry. The «bad luck» of 13 is a cultural construction, fueled by stories, coincidences and centuries of repetition, not by facts.

Tim Sheerman-Chase / Wikimedia Commons (CC BY 2.0) · source