# What to do with 66,000 business cards

Why, build a level three Menger Sponge, of course! What the heck is a Menger Sponge? Glad you asked. It's a three-dimensional fractcal cube of sorts, first described by Austrian mathematician Karl Menger in 1926. When, some seventy years later, Dr. Jeannine Mosely found herself confronted with a gargantuan pile of business cards, rendered useless after the company she worked for changed addresses, she knew what she had to do with them: hand-make a real, live Menger Sponge -- creating an actual object from something that had previously been merely a mathematical abstraction -- a (sorta nerdy) feat of Guinness Book proportions. Before we show you how she made one in reality, a quickie guide to making them in the abstract:

1. Begin with a cube.
2. Divide every face of the cube into 9 squares. This will sub-divide the cube into 27 smaller cubes, like a Rubik's Cube
3. Remove the cube at the middle of every face, and remove the cube in the center, leaving 20 cubes (second image). This is a Level 1 Menger sponge.
4. Repeat steps 1-3 for each of the remaining smaller cubes.

66,048 business cards, 8,000 business card cubes (Menger subunits) and 150 pounds of cube later, it was finished. Figuring the whole project required about 600 hours to build, she recruited volunteers from around the country to build parts of it and then ship them to her. Construction photos after the jump!

First, you've got to make a cube from six business cards -- without staples, tape or glue -- which Dr. Mosely describes how to do:

To make a cube out of six business cards, first take two cards and place them across each other at right angles, centering them as nearly as possible. Fold the flaps of the bottom card down over the top card. Turn them over and repeat. Pull the two cards apart. Six of them can be assembled as shown below to make a cube. All flaps must be on the outside of the finished cube.

For a super-detailed (and kinda math-y) description of how Mosely accomplished the rest of her fractal feat, check out this page at the aptly-named Institute for Figuring. Meanwhile, we'll skip right to the pictures:
Photo by Ravi Ap

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These Sparrows Have Been Singing the Same Songs for 1500 Years
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Swamp sparrows are creatures of habit—so much so that they’ve been chirping out the same few tunes for more than 1500 years, Science magazine reports.

These findings, published in the journal Nature Communications, resulted from an analysis of the songs of 615 adult male swamp sparrows found in six different areas of the northeastern U.S. Researchers learned that young swamp sparrows pick up these songs from the adults around them and are able to mimic the notes with astounding accuracy.

Here’s what one of their songs sounds like:

“We were able to show that swamp sparrows very rarely make mistakes when they learn their songs, and they don't just learn songs at random; they pick up commoner songs rather than rarer songs,” Robert Lachlan, a biologist at London’s Queen Mary University and the study’s lead author, tells National Geographic.

Put differently, the birds don’t mimic every song their elders crank out. Instead, they memorize the ones they hear most often, and scientists say this form of “conformist bias” was previously thought to be a uniquely human behavior.

Using acoustic analysis software, researchers broke down each individual note of the sparrows’ songs—160 different syllables in total—and discovered that only 2 percent of sparrows deviated from the norm. They then used a statistical method to determine how the songs would have evolved over time. With recordings from 2009 and the 1970s, they were able to estimate that the oldest swamp sparrow songs date back 1537 years on average.

The swamp sparrow’s dedication to accuracy sets the species apart from other songbirds, according to researchers. “Among songbirds, it is clear that some species of birds learn precisely, such as swamp sparrows, while others rarely learn all parts of a demonstrator’s song precisely,” they write.

According to the Audubon Guide to North American Birds, swamp sparrows are similar to other sparrows, like the Lincoln’s sparrow, song sparrow, and chipping sparrow. They’re frequently found in marshes throughout the Northeast and Midwest, as well as much of Canada. They’re known for their piercing call notes and may respond to birders who make loud squeaking sounds in their habitat.

[h/t Science magazine]

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Whether you’re trying to spiff up your backyard barbeque or cultivate your green thumb, these summertime gadgets will help you celebrate the season from solstice to the dog days.

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#### 6. MLB HOT DOG BRANDERS; \$8 AND UP

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MoMA Shop

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Why It’s Cool: While meat-lovers will inevitably scarf down a lot of hot dogs this summer, vegetarians who happen to love another kind of dog will be smitten with these stainless steel, Dachshund-shaped corn on the cob prongs. They’re a fun spin on a summer grilling favorite.

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Why It’s Cool: Besides delicious food and great company, some memorable tunes are required for the quintessential barbeque. This portable bluetooth speaker offers up some booming sound in a small package, and with a battery power of 10 hours on a single charge you can keep the party going all night.

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Why It’s Cool: When you’re sick of bocce, hate horseshoes, and you’re over cornhole, you might want to take up “rollors,” a family-friendly game that combines your favorite traditional backyard festivities into one game for people of all ages.

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Why It’s Cool: Rest easy knowing that this 100 percent hand-woven and hand-dyed cotton hammock contributes to artisan job-creation in Thailand.

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Why It’s Cool: Compact, convenient, and durable, the VSSL Shelter can come in handy when things don’t go quite as planned. The device—which features a lightweight emergency shelter all within the handle of a compact, weather-resistant aluminum LED flashlight—is designed to keep you safe under the worst conditions.

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