13 ways to ruin a perfectly good Friday

A day so full of superstition, it has its own psychological disorder: friggatriskaidekaphobia.
Try saying that five times fast (or even once without spitting).

Let’s be honest: there’s no solid proof that more bad things happen on Friday the 13th.

You’re just as likely to trip over your cat or fail a maths test on a Tuesday.

And yet... here we are.

Again.

Avoiding mirrors, black cats, ladders — and anything involving “free bungee jump” in the fine print.

So is there any actual science behind the fear?

Or are we just really bad at numbers, patterns, and probability?

Here are 13 ways to find out. (Or at least 13 ways to ruin a perfectly good Friday.)

1. Prime suspect

Thirteen is a prime number: the maths version of a loner.

It’s about as easy to split as your kid’s last cookie.

Ever tried slicing a cake into 13 equal pieces? Good luck not starting a food fight.

It’s stubborn. It’s odd (literally). And people don’t like numbers that won’t play fair.

Here’s a super curricular side quest: What do 13, encryption algorithms, and internet banking have in common?

Everything.

🧠 Explore: Prime numbers are fundamental to number theory and cryptography, including RSA and elliptic curve encryption.

📚 Suggested reading: Koblitz, N. (1987). Elliptic Curve Cryptosystems.

2. The uninvited +1

Twelve is the universe’s golden child: 12 months, 12 eggs in a dozen, 12 pairs of cranial nerves. It’s tidy, balanced, and socially acceptable.

Thirteen? That’s the uninvited guest who shows up late, messes up the playlist, and spills the punch.

From Euclidean geometry to Norse legends, this is where numbers cross over into human storytelling, and you start seeing structures everywhere.

🧠 Explore: Study numerical bases, composite numbers, and their applications in human culture.

📚 Suggested reading: Ifrah, G. (2000). The Universal History of Numbers.

3. The unlucky date that keeps coming back

Friday the 13th isn’t cursed. It’s just how the calendar rolls.

Any month that starts on a Sunday? You’ll get a Friday the 13th.

Thank you, Pope Gregory XIII, for giving generations of students accidental access to modular maths… and a recurring excuse to blame the calendar for their bad luck.

🧠 Explore: Modular math (mod 7), used in everything from clock arithmetic to cryptography.

📚 Suggested reading: Burton, D. M. (2011). Elementary Number Theory.

4. The probability is not in your favour

Over a 400-year Gregorian calendar cycle, the 13th lands on a Friday more than any other day.

This isn't fate. This is just statistical fluke.

But our brains love patterns, and hate randomness, which is exactly how harmless coincidences start looking freaky.

Super curricular prompt: Explore the intersection of probability and perception — and why we’re terrible at both.

🧠 Explore: Use this anomaly to dive into probability theory and random distributions.

📚 Suggested reading: Feller, W. (1968). An Introduction to Probability Theory and Its Applications.

5. The physics of fear

Your brain’s danger detector (called the amygdala) is like an overenthusiastic fire alarm. Always ready to shout “Danger!” even when it’s just toast burning.

Friday the 13th? Red flag city.

Psychology meets neuroscience: Want to ruin a Friday? Study evolutionary fear responses. Your panic is 10,000 years old and still wearing mammoth furs.

🧠 Explore: Fear response, neurobiology, and evolutionary psychology.

📚 Suggested reading: LeDoux, J. (1996). The Emotional Brain.

6. You’re the victim of confirmation bias

Bad things happen on all days, but we only remember the ones that match our superstitions. It’s a classic case of confirmation bias with our brains doing dodgy data analysis.

It’s like blaming your phone for dropped calls only when you’re outside, but forgetting it works just fine inside.

Perfect for a TOK essay or psych EPQ: Can you trust your own memory?

🧠 Explore: Cognitive biases in decision-making and probability estimation.

📚 Suggested reading: Kahneman, D. (2011). Thinking, Fast and Slow.

7. Your default mode network ruins everything

Ever catch yourself worrying about “what if” moments?

That’s your brain’s default mode network.

It's the part that helps you imagine fun things and also makes spooky stories feel real.

It’s where fear and superstition fester.

Neuroscience insight: The same mechanism that helps us imagine the future… also makes us afraid of cursed numbers.

🧠 Explore: Brain networks involved in imagination, anxiety, and future prediction.

📚 Suggested reading: Raichle, M. E. (2015). The Brain’s Default Mode Network (Annual Review of Neuroscience).

8. Loki wrecked the party

In Norse mythology, Loki was the 13th guest at a dinner in Valhalla.

He got someone killed.

Mythology, probability, and game theory walk into a banquet hall... Someone doesn’t walk out.

Moral: don’t skip RSVP.

🧠 Explore: Use mythology and cultural narratives to examine symbolic numerology.

📚 Suggested reading: Lindow, J. (2001). Norse Mythology: A Guide to the Gods, Heroes, Rituals, and Beliefs.

9. Judas ruined group dinners forever

The Last Supper? 13 at the table. Judas was #13.

He brought betrayal, and terrible number PR for centuries to come.

Sometimes, all it takes is one bad apple to ruin the whole basket... or the whole number’s reputation.

Use this in Religious Studies, Sociology, or even Art History: 13 is symbolic. But so is who gets blamed.

🧠 Explore: Religious symbolism and number metaphors in art, theology, and storytelling.

📚 Suggested reading: Vermes, G. (2005). The Passion: The True Story of an Event That Changed Human History.

10. Apollo 13 exploded

NASA’s infamous Apollo 13 mission launched at 13:13 and was the only moon mission to experience an in-flight explosion.

Is it bad luck, or just entropy? Cue discussion on systems engineering, risk, and the mathematics of failure.

🧠 Explore: Engineering risk, chaos theory, and human factors in complex systems.

📚 Suggested reading: Tufte, E. (1997). Visual Explanations: Images and Quantities, Evidence and Narrative — includes analysis of the Apollo 13 O-ring failure.

11. Italy disagrees

In Italy, 13 is lucky. It’s 17 that’s cursed. Rearranged Roman numerals (XVII = VIXI) spell “I have lived” which is a poetic way to say, “Game over.”

A cross-cultural superstition study with language, history, and logic.

🧠 Explore: Linguistics, culture, and symbolic systems in number perception.

📚 Suggested reading: Devereux, G. (1967). Superstition and Symbol.

12. Elevators are lying to you

Many buildings skip labeling the 13th floor. You might press floor 14, but physics doesn’t care — you’re still 130 feet above ground, no matter what the button says.

Architectural design, human psychology, and number theory meet in a hotel corridor. Bring snacks.

🧠 Explore: Spatial cognition, behavioral design, and urban superstition.

📚 Suggested reading: Gifford, R. (2007). Environmental Psychology: Principles and Practice.

13. You didn’t check the data

A 1993 study claimed Friday the 13th causes more road accidents.

Later studies showed… it doesn’t.

The scariest thing? Bad research spreads faster than good data.

This is the hill we die on: correlation ≠ causation.

Use responsibly.

Or not at all.

🧠 Explore: Research design, statistical literacy, and media sensationalism.

📚 Suggested reading: Goldacre, B. (2008). Bad Science.

🎥 Have a watch of Ben Goldacre's TED talk on Battling Bad Science:

So what should you do with all this?

Easy.

Turn fear into curiosity.

Turn superstition into science.

Out-nerd the curse.

Want to feel safer?

Learn more.

Laugh more.

And maybe stay off ladders. Just in case.

— Nici