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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."

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Medicine
Charles Dickens Museum Highlights the Author's Contributions to Science and Medicine

Charles Dickens is celebrated for his verbose prose and memorable opening lines, but lesser known are his contributions to science—particularly the field of medicine.

A new exhibition at London’s Charles Dickens Museum—titled "Charles Dickens: Man of Science"—is showcasing the English author’s scientific side. In several instances, the writer's detailed descriptions of medical conditions predated and sometimes even inspired the discovery of several diseases, The Guardian reports.

In his novel Dombey and Son, the character of Mrs. Skewton was paralyzed on her right side and unable to speak. Dickens was the first person to document this inexplicable condition, and a scientist later discovered that one side of the brain was largely responsible for speech production. "Fat boy" Joe, a character in The Pickwick Papers who snored loudly while sleeping, later lent his namesake to Pickwickian Syndrome, otherwise known as obesity hypoventilation syndrome.

A figurine of Fat Boy Joe
Courtesy of the Charles Dickens Museum

Dickens also wrote eloquently about the symptoms of tuberculosis and dyslexia, and some of his passages were used to teach diagnosis to students of medicine.

“Dickens is an unbelievably acute observer of human behaviors,” museum curator Frankie Kubicki told The Guardian. “He captures these behaviors so perfectly that his descriptions can be used to build relationships between symptoms and disease.”

Dickens was also chummy with some of the leading scientists of his day, including Michael Faraday, Charles Darwin, and chemist Jane Marcet, and the exhibition showcases some of the writer's correspondence with these notable figures. Beyond medicine, Dickens also contributed to the fields of chemistry, geology, and environmental science.

Less scientifically sound was the author’s affinity for mesmerism, a form of hypnotism introduced in the 1770s as a method of controlling “animal magnetism,” a magnetic fluid which proponents of the practice believed flowed through all people. Dickens studied the methods of mesmerism and was so convinced by his powers that he later wrote, “I have the perfect conviction that I could magnetize a frying-pan.” A playbill of Animal Magnetism, an 1857 production that Dickens starred in, is also part of the exhibit.

A play script from Animal Magnetism
Courtesy of the Charles Dickens Museum

Located at 48-49 Doughty Street in London, the exhibition will be on display until November 11, 2018.

[h/t The Guardian]

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Health
Feeling Down? Lifting Weights Can Lift Your Mood, Too
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There’s plenty of research that suggests that exercise can be an effective treatment for depression. In some cases of depression, in fact—particularly less-severe ones—scientists have found that exercise can be as effective as antidepressants, which don’t work for everyone and can come with some annoying side effects. Previous studies have largely concentrated on aerobic exercise, like running, but new research shows that weight lifting can be a useful depression treatment, too.

The study in JAMA Psychiatry, led by sports scientists at the University of Limerick in Ireland, examined the results of 33 previous clinical trials that analyzed a total of 1877 participants. It found that resistance training—lifting weights, using resistance bands, doing push ups, and any other exercises targeted at strengthening muscles rather than increasing heart rate—significantly reduced symptoms of depression.

This held true regardless of how healthy people were overall, how much of the exercises they were assigned to do, or how much stronger they got as a result. While the effect wasn’t as strong in blinded trials—where the assessors don’t know who is in the control group and who isn’t, as is the case in higher-quality studies—it was still notable. According to first author Brett Gordon, these trials showed a medium effect, while others showed a large effect, but both were statistically significant.

The studies in the paper all looked at the effects of these training regimes on people with mild to moderate depression, and the results might not translate to people with severe depression. Unfortunately, many of the studies analyzed didn’t include information on whether or not the patients were taking antidepressants, so the researchers weren’t able to determine what role medications might play in this. However, Gordon tells Mental Floss in an email that “the available evidence supports that [resistance training] may be an effective alternative and/or adjuvant therapy for depressive symptoms that could be prescribed on its own and/or in conjunction with other depression treatments,” like therapy or medication.

There haven’t been a lot of studies yet comparing whether aerobic exercise or resistance training might be better at alleviating depressive symptoms, and future research might tackle that question. Even if one does turn out to be better than the other, though, it seems that just getting to the gym can make a big difference.

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