Why Your Christmas Lights Always Get Tangled, According to Science

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A Christmas tree isn't a Christmas tree without those pretty colored lights, right? OK, no problem. You stored them in a box marked "Xmas lights" 11 months ago. You know where the box is. Now you just have to open the box, grab the lights, and—

That's where it gets tricky. Unless you're very lucky, or extremely well organized, the lights are likely all tangled up; soon you're down on your hands and knees, struggling to untangle a spaghetti-like jumble. (And it's not just you: A couple of years ago, the British grocery chain Tesco hired temporary "Christmas light untanglers" for the holiday season.) But why are Christmas lights so prone to tangling in the first place—and can anything be done about it?

IT'S KNOT AN EASY PROBLEM TO SOLVE

There are really two separate problems, explains Colin Adams, a mathematician at Williams College in Williamstown, Massachusetts and the author of The Knot Book, an introduction to the mathematical theory of knots. First, the cord on which the lights are attached is prone to tangling—just as headphone and earbud cords are (or, in the past, telephone handset cords).

Several years ago, physicists Dorian Raymer and Douglas Smith, then at the University of California, San Diego, did a study to see just how easily cords can get tangled. They put bits of string of various lengths in a cube-shaped box, and then mechanically rotated the box so that the strings tumbled around, like socks in a dryer, repeating the experiment more than 3400 times. The first knots appeared within seconds. More than 120 different types of knots spontaneously formed during the experiment. They also found—perhaps not surprisingly—that the longer the string, the more likely it was to become knotted (few knots formed in strings shorter than 18 inches, they noted). As the length of the string increased, the probability of a knot forming approached 100 percent.

The material that the string (or cord) is made of is important too; a more flexible cord is more likely to tangle than a less flexible one. And while the length of the cord matters, so does its diameter: In general, long cords get tangled more easily than short ones, but a cord with a large diameter will be less flexible, which reduces the risk of knotting. In other words, it's the ratio of length to diameter that really matters. That's why a garden hose can get tangled—it's relatively stiff, but it's also very long compared to its diameter.

But that's not the end of the story. If a cord has a metal wire inside it—as traditional Christmas lights do—then it can acquire a sort of "natural curvature," Jay Miller, a senior research scientist at the Connecticut-based United Technologies Research Center, tells Mental Floss. That means that a wire that's been wrapped around a cylindrical spool, for example, will tend to retain that shape.

"Christmas lights are typically spooled for shipping or packing, which bends metal wire past its 'plastic limit,' giving it natural curvature approximately the size of the spool it was wound around," Miller says. Christmas lights can be even harder to straighten than other wound materials because they often contain a pair of intertwined wires, giving them an intrinsic twist.

And then there's the additional problem of the lights. "Christmas lights are doubly difficult, once things get tangled, because there are all of these little projections—the lights—sticking out of them," Adams tells Mental Floss. "The lights get in the way of each other, and it makes it very difficult to pull one strand through another. That means once you're tangled, it's much harder to disentangle."

IS THERE ANY HOPE FOR A TANGLE-FREE CHRISTMAS?

What, then, can be done? One option would be for manufacturers to make the cord out of a stiff yet elastic material—something that would more readily "bounce back" from the curvature that was imparted to it while in storage. A nickel-titanium alloy known as Nitinol might be a candidate, says Miller—but it's too expensive to be a practical choice. And anyway, the choice of material probably makes little difference as long as the lights still protrude from the cord. Perhaps the biggest breakthrough in recent years has been the proliferation of LED "rope lights" that don't employ traditional bulbs at all; rather, they use LEDs embedded within the rope-like cord itself. Of course, these can still get tangled up in the manner of a garden hose, but without those pesky protrusions, they're easier to untangle.

A simpler solution, says Adams, is to coil the lights very carefully when putting them away, ideally using something like twist-ties to keep them in place. (Martha Stewart has proposed something similar, using sheets of cardboard instead of twist-ties.)

Meanwhile, the mathematicians have some advice if you find yourself confronted with a hopelessly tangled, jumbled cord: Find one of the "free" ends, and work from there.

"Eventually," Adams assures us, "you will succeed."

10 Citizen Science Projects That Need Your Help

A citizen scientist takes a photo of scarlet mushrooms.
A citizen scientist takes a photo of scarlet mushrooms.
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Channel your inner Nikola Tesla or Marie Curie by participating in actual scientific research, either out and about or without even leaving your couch. These projects unleash the power of the public to be places that researchers can’t be and to spread the workload when data start piling up. They really can’t do it without you.

1. Catalog photos of Earth's cities at night.

Photo from space of a city at night
Identify cities from the photos taken from the International Space Station.
Chris Hadfield, NASA // Public Domain

Cities at Night—a study by Complutense University of Madrid—asks people to catalog images of the Earth at night taken from the International Space Station, part of the millions of images in the Gateway to Astronaut Photography of Earth database. The current project, Lost at Night, needs people to identify cities within images of 310-mile circles on Earth. Hundreds of volunteers have classified thousands of images already, but classification by multiple individuals ensures greater accuracy. In fact, the project will determine the optimum number of people needed. The primary goal is an open atlas of publicly available nighttime images. Just log on to the image database to help.

2. Follow fish using high-tech tags.

You’ll have to go fishing—an outdoor activity you can do by yourself!—for this assignment. Volunteer to tag fish for the American Littoral Society, whose citizen scientists have tagged more than 640,000 fish since the program began in 1965. You can tag the fish you catch and release, or report tagged fish to the organization. The data is sent to the National Marine Fisheries Service Laboratory in Woods Hole, Massachusetts, where it helps scientists track the populations and movements of coastal species like striped bass, flounder, and bluefish. To get started, become a member of the American Littoral Society, which comes with a packet of tagging gear and instructions.

3. Spy on penguins in Antarctica.

Penguins on an ice floe
Keeping tabs on penguins is one way a citizen scientist can lend a hand.
axily/iStock via Getty Images

Here's another project for those stuck indoors. Penguins are threatened by climate change, fisheries, and direct human disturbance, yet scientists have little data on the birds. To fill in the gaps, 50 cameras throughout the Southern Ocean and Antarctic Peninsula take images of colonies of gentoo, chinstrap, Adélie, and king penguins year-round. You can help the University of Oxford-based research team by sorting through thousands of images to identify and mark individual adult penguins, chicks, and eggs. You'll be pinpointing seasonal and geographic variations in populations that may represent changes to the Antarctic ecosystem. Marking other animals in the images helps researchers figure out which ones are hanging around penguin colonies. Discuss a specific image or the project with the science team and other volunteers in an online forum.

4. Battle an invasive marine species.

Like to dive or snorkel? Make it count by reporting lionfish sightings or captures to the Reef Environmental Education Foundation's Volunteer Reef Survey Project. Lionfish, which are native to the Indo-Pacific, were first sighted in the South Atlantic in 1985 and were likely released by private aquarium owners. Since then, they have spread throughout the Caribbean and Gulf of Mexico and caused native fish populations to decline by up to 80 percent. Scientists say this invasion may be one of the century’s greatest threats to warm temperate and tropical Atlantic reefs. You can also join a lionfish derby to catch and kill some of the tasty fish so scientists can analyze their biology.

5. Count birds from your backyard.

Bluebirds at a bird feeder
Bluebirds dine on mealworms at a bird feeder.
MelodyanneM/iStock via Getty Images

North American birds are in trouble. Recent studies predict dramatic declines in the populations of migratory birds due to climate change—and much of the data that went into these studies came from citizen scientists who monitored species without leaving home. The Cornell Lab of Ornithology and Birds Canada launches Project FeederWatch in the winter months; you simply put out a bird feeder and report the number and species of birds that visit it. Citizen scientists can also join the Cornell Lab's NestWatch—you find a nest, monitor it every three or four days, and report your data. And every February, the Audubon Society runs the Great Backyard Bird Count, in which participants submit data to produce a real-time snapshot of bird populations across North America. Any time of the year, birdwatchers can submit lists of the birds they see on eBird, a huge database of sightings that informs public policy, conservation efforts, and other initiatives.

6. Photograph plants for climate change research.

The Appalachian Mountain Club's Mountain Watch program asks hikers to document alpine and forest plants for ecological research. By taking photos of flowers and fruiting plants along woodland trails and uploading them to the iNaturalist app, participants provide data about the times and places that plants bloom. Scientists then compile the information in an online database and analyze it for trends that could indicate changing climates.

7. Comb through ships' logbooks for weather data.

Old handwritten letters
Practice your handwriting-deciphering skills on the Old Weather project.
scisettialfio/iStock via Getty Images

Ships’ logs from mid-19th century American sailing vessels contain detailed weather observations. Citizen scientists can help transcribe observations from whaling vessels for the Old Weather project; scientists will use the information to learn more about past environmental conditions and create better climate models for future projections. Historians will also use the data to track past ship movements and tell the stories of the people on board.

8. Make American history documents and science notes accessible to more people.

The Smithsonian Libraries are stuffed with original history and science documents that have lain in drawers for decades. Help open up "America's attic" to the public by organizing and transcribing digital versions of handwritten field notebooks, diaries, logbooks, specimen labels, photo albums, and other materials. You'll join thousands of other volunteers to investigate documents like the Sally K. Ride Papers, the collection of the Freedmen's Bureau (which helped former slaves following the Civil War), and field studies of insects by the Irish naturalist Arthur Stelfox.

9. Investigate historical crimes in Australia.

Drawing of a convict ship to Australia
A drawing of a 19th-century convict ship destined for Australia.
Photos.com/iStock via Getty Images

If you're obsessed with true crime, you'll love this project. Volunteer to investigate and transcribe criminal records from 19th- and 20th-century Australia, which was founded as a British penal colony. Alana Piper, a postdoctoral research fellow at the Australian Centre for Public History at the University of Technology Sydney, will use the transcriptions to construct the "life histories and offending patterns of Australian criminals" from the 1850s to the 1940s. More than 40,000 subjects have been completed so far.

10. Map the unique features of Mars's South Pole.

Travel to Mars—without the hassle of zero gravity or space-vegetable farming—through Planet Four, a citizen science project that is currently tasked with identifying features on Mars's dynamic South Pole. Volunteers examine photos from the HiRISE camera on NASA's Mars Reconaissance Orbiter and pick out "fans" or "blotches" in the landscape of seasonal carbon dioxide ice. Scientists believe these structures indicate wind speed and direction on the Martian surface and offers clues about the evolution of the Red Planet's climate.

Why Cats Like to Shove Their Butts in Your Face, According to an Animal Behavior Expert

This cat might be happier showing off its butt.
This cat might be happier showing off its butt.
Okssi68/iStock via Getty Images

Cats are full of eccentric behaviors. They hate getting wet. Their tongues sometimes get stuck midway out of their mouths, known as a “blep.” And they’re really happy hanging out in bodegas.

Some of these traits can be explained while others are more mysterious. Case in point: when they stick their rear end in your face for no apparent reason.

Are cats doing this just to humiliate their hapless caregivers? What would possess a cat to greet a person with its butt? Why subject the person who gives you food and shelter to such degradation?

To find out, Inverse spoke with Mikel Delgado, a postdoctoral fellow at the School of Veterinary Medicine at UC Davis. According to Delgado, cats don’t necessarily perceive their rectal flaunting as anything aggressive or domineering. In fact, it might be a cat’s way of saying hello.

“For cats, it’s normal for them to sniff each other’s butts as a way to say hello or confirm another cat’s identity,” Delgado said. “It’s hard for us to relate to, but for them, smell is much more important to cats and how they recognize each other than vision is. So cats may be ‘inviting’ us to check them out, or just giving us a friendly hello.”

For a cat, presenting or inspecting a butt is a kind of fingerprint scan. It’s a biological measure of security.

Other experts agree with this assessment, explaining that cats use their rear end to express friendliness or affection. Raising their tail so you can take a whiff is a sign of trust. If they keep their tail down, it’s possible they might be feeling a little shy.

If you think this situation is eased by the fact you rarely hear cats fart, we have bad news. They do. Because they don’t often gulp air while eating, they just don’t have enough air in their digestive tract to make an audible noise. Rest assured that, statistically speaking, there will be times a cat giving you a friendly greeting is also stealthily farting in your face.

[h/t Inverse]

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