Happy Phi Day: The Last Day to Match the Golden Ratio for a Century


Math whizzes may have noticed something particularly pleasing about today's date. According to Bloomberg, June 1, 2018 (formatted as 1/6/18 in many parts of the world) is Phi Day, a date that matches the first four digits of the golden ratio.

Represented by the 21st letter of the Greek alphabet, the golden ratio, which comes out to roughly 1.618 when rounded, is the number you get when you divide a line into two parts so that the longer part divided by the smaller part is the same as the total length divided by the longer part (or simplified: When the smaller is to the larger as the larger is to the whole).

Non-mathematicians might know it better as the number that appears constantly in nature, art, and architecture. The Pyramids at Giza, Leonardo da Vinci's "Vitruvian Man," nautilus shells, sunflower seed heads, and spiral galaxies all feature the golden ratio.

The golden ratio is also closely related to the famous Fibonacci sequence. In this series of numbers beginning with zero or one, each subsequent number equals the sum of the previous two (i.e., 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, etc.). The ratio of any two successive numbers in this sequence comes very close to the golden ratio. Shapes made with Fibonacci dimensions are considered pleasing to the eye, which is why they so often appear in art, either unintentionally or by design.

Unlike other math holidays such as Pi Day, Phi Day only comes once a century. You can celebrate the once-in-a-lifetime occasion by taking a walk outside and seeing how many examples of the golden ratio you can spot in your neighborhood.

[h/t Bloomberg]

15 Convenient Products That Are Perfect for Summer

First Colonial/Lunatec/Safe Touch
First Colonial/Lunatec/Safe Touch

The Fourth of July is the epitome of summer—and after several months spent indoors, you need some outdoor fun more than anything. Check out these 15 summer must-haves while they’re on sale and save an extra 15 percent when you spend $50 or more with the code JULYFOURTH15.

1. CARSULE Pop-Up Cabin for Your Car; $300 (20 percent off)

Carsule tent from Mogics.

This tent connects to your hatchback car like a tailgate mobile living room. The installation takes just a few minutes and the entire thing stands 6.5 feet tall so you can enjoy the outdoors from the comfort of your car.

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2. Mosquito Killer Lamp; $30 (25 percent off)

Mosquito-killing lamp.

If you just so happen to be one of those unlucky souls who attracts a suspicious amount of mosquitos the second you step outside, you need this repellent lamp to help keep your arms and legs bite-free. It uses a non-toxic combination of LED lights, air turbulence, and other methods to keep the pests at bay.

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3. Super Shield Mosquito Repellent Electronic Watch Band; $17 (57 percent off)

Mosquito repeller watch.
Safe Touch

While a lamp is a great non-toxic solution for keeping bugs at bay, active individuals need a bug repellent that can keep up with their lifestyle. This wrist wearable keeps you safe from mosquitoes anywhere by using ultrasonic sounds to drive them away.

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4. ZeroDark 3-Piece Tactical Set: Flashlight, Lantern, and Headlamp; $20 (66 percent off)

Aduro flashlight set.

If you want your summer to be lit, this set will do the trick. All puns aside, this trio of LED brightness is perfect for camping fun and backyard parties, or it can be stored in the car for emergencies.

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5. Outdoor Collapsible Cooler and Camp Table Set; $64 (27 percent off)

First Colonial cooler.
First Colonial

Cookouts are easy with this cooler and table set that chills your drink until you're ready to pop it into one of the four convenient cupholders. Bring this set camping or out by the pool for convenience anywhere.

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6. Trident: Underwater Scooter; $550 (21 percent off)

Trident underwater scooter.

If you’ve ever dreamed of better mobility while exploring the water, you’re not alone. The Trident underwater scooter, which raised over $82,000 on Indiegogo, can propel you through the water at up to nearly 6 feet per second, which isn't that far off from how fast Michael Phelps swam in his prime. The battery on it will last 45 minutes, allowing you to traverse with ease.

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7. Go Portable Solar Oven; $119 (14 percent off)

GoSun solar grill.

Bake, roast, steam, or broil anywhere you bring this portable oven. Measuring in at just over a foot long and weighing only two pounds, the oven will work in most daytime weather conditions and can hold around 13 ounces of food.

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8. 3-in-1 Waterproof Bug Zapper Lantern; $25 (50 percent off)

3P Experts bug zapper.
3P Experts

Mosquitoes tend to be a big problem at night, partly because it's hard to swat in the dark. This lantern will light the area and zap mosquitos from nipping at you in the process.

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9. Urban E-Skateboard: Basic Version (Orange); $120 (73 percent off)

Urban Rover E-Skateboard
Urban Rover

This e-skateboard is perfect for getting around during the summer. You'll catch a breeze while you’re cruising on the battery-powered platform and won’t break a sweat when you pop the compact board in your bag.

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10. H2 Headlamp: Waterproof, Rechargeable LED Wide 180° Angle Headlight; $37 (26 percent off)

Headlamp from One80Light

Camping, car troubles, and sports all pose a problem at night. This LED headlight will light up your surroundings across a 180-degree radius for prime visibility, meaning your outdoor activities won't have to stop when the sun sets.

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11. Whirlwind Cool Bladeless Mini Fan; $22 (63 percent off)

Bladeless fan

This portable fan comes in a powerful handheld size so you can keep cool while on the move. Unlike other portable fans, this one has a sleek, bladeless design and features three different speeds.

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12. Bladeless Personal Fan; $22 (63 percent off)

Bladeless fan
3P Tech

This bladeless fan won't just keep you cool while you work on your laptop—it also has a built-in rechargable battery that you can use to charge your phone.

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13. MOGICS Coconut: Portable Waterproof Light; $37 (24 percent off)

Mogics portable lamp.

This portable light is designed to adapt to your lighting preference. It self-inflates in a few seconds and can bounce, get wet, and set the mood.

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14. Lunatec 1L Hydration Spray Water Bottle; $25 (21 percent off)

Lunatec spray water bottle.

A water bottle can do more than hydrate you. This one has a spray nozzle that can create shower, stream, and mist patterns for doing dishes while camping, sharing a sip without sharing germs, and washing off those muddy shoes after a long hike.

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15. Sport Force Hydration Backpack; $25 (68 percent off)

Hydration backpack.
It's All Goods

Hiking enthusiasts know how important it is to stay hydrated, but carrying around awkward jugs of water is a hassle. This unique hydration backpack can be filled with two liters of water and features a convenient drinking nozzle that extends to the user's mouth. Now, you can replenish those fluids without breaking stride.

Buy it: Mental Floss Shop

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7 of History's Greatest Pranks

In the 19th century, a New York newspaper convinced readers these creatures lived on the Moon.
In the 19th century, a New York newspaper convinced readers these creatures lived on the Moon.
Wikimedia Commons // Public Domain

It's not known for certain where or why April Fools' Day originated. Some say the humorous holiday goes back to a Roman festival or events in the Bible, while others point to a change in the calendar in 16th-century France. According to the theory, people in various regions across the country marked the new year on different dates, and when the King of France, Charles IX, signed the Edict of Roussillon and standardized the new year to January 1, not everybody got the memo. This led some to continue celebrating the new year around April, and therefore become the butt of jokes.

What we do know is that, at some point, duping people on April 1 became something of a pastime. One of the most common early pranks was to send potential “fools” on impossible tasks—literally, on a fool’s errand—to look for “a bucket of striped paint, a bucket of steam, pigeon milk, a jar of elbow grease,” writes folklorist Nancy Cassell McEntire. In the spirit of good-hearted tomfoolery, here are seven more great pranks from history.

1. Rome’s Most Unbearable Party Stunt

Bust of a Roman emperor against a red background
Not surprisingly, the juvenile emperor had a juvenile sense of humor.
Carole Raddato, Flickr // CC BY-SA 2.0

Considered one of the most incompetent Roman emperors, the teenage Elagabalus was, if nothing else, a solid prankster. According to archaeologist Warwick Ball’s book Rome in the East, Elagabalus routinely seated “his more pompous dinner guests on ‘whoopee cushions’ that let out a farting noise.” Purportedly, the emperor also thought it was funny to release snakes in public. One of his favorite stunts, supposedly, was to place a tamed bear, lion, or leopard in the rooms of his sleeping, drunken guests.

2. Anthemius’s Fake Earthquake Machine

Anthemius of Tralles, a 5th-century Greek architect who helped build Istanbul’s Hagia Sophia, knew his way around a toolbox. So when a feud erupted between him and his neighbor, Zeno, Anthemius knew exactly what to do. The architect erected several boilers of water in his house and connected them to a hose, which he fed into a small hole leading into Zeno’s cellar next door. According to the 1888 Magazine of Western History, “When Anthemius desired to annoy his neighbor, he lighted fires under his boilers, and the steam produced by them rushed in such quantity and with such force under Zeno’s floors that they were made to heave with all the usual symptoms of an earthquake.”

3. The Misleading Monk’s Apple Trick

One of the earliest documented pranks dates to the late 15th century, when Thomas Betson, a monk at England’s Syon Abbey, hollowed out the core of an apple and inserted a large beetle, causing the fruit to rock back and forth. That wasn’t the only trick hidden up the monk’s tunic. Betson was also a fan of making objects in the monastery levitate. Using a strand of fine hair and wax, he could suspend a hollow egg in midair.

4. London’s Washing of the Lions

Vintage event ticket
Your one-way ticket to being duped.
Wikimedia Commons // Public Domain

For centuries, the Tower of London was home to a menagerie of wild animals, from polars bears to lions and even a beer-drinking zebra. On April Fools’ Day in 1698, a clever trickster convinced a handful of people the lions were receiving their annual bath. No such event existed, but that didn’t stop hordes of gawkers from visiting the Tower to have a look. For the next two centuries, the con remained a running gag, even long after the last lion left the Tower. By the 19th century, tricksters were distributing fake tickets to the “Annual Ceremony of the Washing of the Lions.”

5. The English Mercurie: The Prank Newspaper That Keeps On Pranking

Philip Yorke, a Cambridge-educated member of British Parliament and the Second Earl of Hardwicke, used his privilege to pull off some grade-A pranking. In the 1740s, he and his friend Thomas Birch printed The English Mercurie, a phony newspaper purportedly published in 1588—a date that, if true, would make it one of the world's first newspapers. In 1766, Birch gifted the paper, along with other documents, to the British Museum, which treated the publication as legitimate for decades. In fact, the “information” in the fake news report is still erroneously used today! Even the paper's Wikipedia page calls out other Wikipedia entries for citing The English Mercurie as a legitimate source.

6. The New York Sun’s Moon Hoax

On August 25, 1835, readers of the New York Sun were stunned to learn there was a civilization on the Moon. An English astronomer, the paper reported, had traveled to the Southern Hemisphere to study the night’s sky and, upon glancing at the Moon, discovered vegetation, pyramids, unicorns, bipedal beavers, and humanoid creatures with wings. The story, of course, was fake. The series of satirical articles aimed to poke fun at people like science writer Thomas Dick, who had recently claimed the Moon was home to an alien population of more than 4 billion extraterrestrials. Unfortunately, the Sun underestimated the public’s gullibility. News of the “discovery” spread across the globe.

7. William Buckland’s Guano Graffiti

A 19th-century paleontologist and poop expert—yes, poop expert—William Buckland believedguano was the next great lawn fertilizer. As an undergrad at Oxford, he proved his point by carefully sprinkling a bucket of bat guano across one of the university’s lawns, spelling out the word GUANO. Officials quickly noticed the feces and removed it. Little did they know, however, that the fertilizer had invigorated the grass below. Within weeks, the word GUANO was growing in the university’s lawn—and university officials had no way to remove it. According to Buckland’s biographer, “[T]he brilliant green grass of the letters amply testified to [guano’s] efficacy as a dressing.”