Why Your Christmas Lights Always Get Tangled, According to Science


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?


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."


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."

Justin Tallis, AFP/Getty Images
Stones, Bones, and Wrecks
8 Cemeteries Unearthed at Construction Sites
Justin Tallis, AFP/Getty Images
Justin Tallis, AFP/Getty Images

The people who lived before us are often just beneath our feet, even if their tombs are sometimes forgotten. Lost under urban development, they are rediscovered when a subway, building, or other structure claims the ground for progress. Here are eight burial sites that came to light in this unconventional manner.


The construction of Rome's subway has unearthed everything from a 2nd-century home decorated with mosaics and frescos to a 2300-year-old aqueduct. The San Giovanni station, slated to open in 2018, will feature displays of artifacts found during its excavation, such as Renaissance ceramics and the remains of a 1st-century agricultural fountain.

Back in 2016, extension work on Line C ran into a 2nd-century military barracks with 39 rooms, likely used by Emperor Hadrian's army, as well as a mass grave of 13 skeletons. The dead may have been members of the elite Praetorian Guard, protectors of the Roman emperor. Investigations are ongoing, although officials have planned for the barracks to be incorporated into the station architecture. Its opening date remains in limbo as archaeological finds continue to slow its construction.


In 1991, construction of a federal office building revealed a colonial-era burial ground in Lower Manhattan. The graves, dating back to the 1690s, had been lost due to landfill and development, yet were identified as part of the African burial grounds that in the 17th century were located outside the old city.

Banned from interment in white cemeteries, free and enslaved Africans and African Americans had established a place to give respect to their dead, with an estimated 10,000 to 20,000 burials. Thanks to grassroots activism, including protests against continued construction, the site is now commemorated with the African Burial Ground National Monument, which opened in 2006.

It's not the sole black cemetery to be buried under development in New York: The Second African Burial Ground, dating from the 18th and 19th centuries, is located below today's Sarah D. Roosevelt Park on the Lower East Side; and in East Harlem, a 17th-century slave burial ground, discovered by construction workers at a bus depot, awaits a planned memorial.


Burrowing deep under London, the ongoing Crossrail commuter rail project has exposed obscure layers of the city's past—and a treasure trove of history. Along with medieval ice skates and a Tudor bowling ball, archaeologists have identified two mass graves. One has 13 skeletons of people who probably died in the 14th century of Black Death (with DNA on their teeth still holding the plague bacterium Yersinia pestis); a larger site has 42 skeletons of victims of the Great Plague of 1665. The study of the Great Plague skeletons, excavated in 2015 by Museum of London Archaeology, similarly showed traces of the disease in their old teeth. (Luckily the bacteria is no longer active, so no need to dust off your plague doctor beak mask.)

While such "plague pits" have long been rumored—some urban legends say the London Underground had to curve to avoid messy heaps of bodies—study of the sites indicated that there was in fact great care taken with the deceased. The bodies were placed in individual coffins, giving them some dignity even in this hasty mass burial.


Sometimes, to borrow a line from Poltergeist, people only move the headstones when relocating a cemetery, and stray bones and coffins are left behind (digging up the dead is generally unpleasant work). That seemed to be the case with a graveyard unearthed at a construction site on Arch Street in Philadelphia in March 2017. The dozens of coffins that were discovered are believed to be part of the First Baptist Church Burial Ground, established in 1707 and supposedly moved to Mount Moriah Cemetery in 1859. The Mütter Institute spearheaded a crowdfunding campaign for analysis and reinterment of the bones, and volunteer archaeologists convened at the site, racing against time to map the grounds and remove the burials of more than 100 people. Their remains were carefully analyzed.

Archaeologists subsequently found the remains of more than 400 people at the site as construction went on in other areas. Building at the site continues, as does the grassroots-funded research on the bones (you can follow the team's progress at the Arch Street Bones Project website).


In 2013, construction on a subway in Thessaloniki, Greece, turned up the grave of a woman buried around 2300 years ago. The Early Hellenistic lady was interred with a gold olive branch wreath.

Surprisingly, this wasn't the first such skeleton found during subway construction to be so regally crowned. In 2008, another Hellenistic woman was discovered with four gold wreaths and gold earrings in the shape of dogs' heads, all indicators of wealth and respectability—something marred a bit by the sewage pipe that had wrecked part of her grave.


While digging a trench in 2013 for a gas pipeline in Saskatchewan, Canada, a contractor noticed bone fragments in the soil that turned out to be 1000-year-old human remains.

Construction was halted so First Nations elders and archaeologists could examine the area. Ultimately, the pipeline company opted to tunnel deeper to avoid disturbing the ancient burials.

It was only one of many instances of massive infrastructure projects coming in contact with pre-colonial burial grounds. In 2017, for example, road construction in Duluth, Minnesota desecrated graves when the state's department of transportation failed to evaluate the area for artifacts prior to breaking ground.


Near Weymouth in Dorset, England, a mass grave of more than 50 young men was discovered in 2009 by archaeologists doing a survey before road construction began. All the victims had been killed brutally, at once, with multiple blows from a sharp weapon visible on their bones, and their heads had been severed. In 2010, researchers identified them as Vikings by radio-carbon dating the bones to 910 to 1030 CE, when the English clashed with Viking invaders. Analysis of the isotopes in the teeth indicated Scandinavian origins. Due to their lack of clothing and their similar manner of death, they were likely executed as captives. They're now part of the Dorset County Museum.


Among the roughly 38,000 people interred beneath a neighborhood on Chicago's Far Northwest Side are the impoverished inmates of the Cook County almshouse and patients from the county insane asylum. The area was known as Dunning, and its squalid institutions were so well known that a judge in 1889 declared them a "tomb for the living." The 20 acres of the site also included a potter's field for the indigent and unclaimed, and the burials of more than 100 unidentified dead from the Great Chicago Fire of 1871.

The potter's field was revealed in 1989 during construction on luxury homes. Sewer workers who were laying pipes also turned up a corpse that was so well-preserved his handlebar mustache was still visible. Bodies were relocated to a site now called Read-Dunning Memorial Park, giving these dead some recognition in the city for the first time.

Just Two Cans of Soda a Day May Double Your Risk of Death From Heart Disease

If you've been stocking your refrigerator full of carbonated corn syrup in anticipation of warmer weather, the American Heart Association has some bad news. The advocacy group on Wednesday released results of research that demonstrate a link between consumption of sugary drinks—including soda, fruit juices, and other sweetened beverages—and an increased risk of dying from heart disease.

Study participants who reported consuming 24 ounces or more of sugary drinks per day had twice the risk of death from coronary artery disease of those who averaged less than 1 ounce daily. There was also an increased risk of death overall, including from other cardiovascular conditions.

The study, led by Emory University professor Jean Welsh, examined data taken from a longitudinal study of 17,930 adults over the age of 45 with no previous history of heart disease, stroke, or diabetes. Researchers followed participants for six years, and examined death records to determine causes. They observed a greater risk of death associated with sugary drinks even when they controlled for other factors, including race, income, education, smoking habits, and physical activity. The study does not show cause and effect, the researchers said, but does illuminate a trend.

The study also noted that while it showed an increased risk of death from heart disease, consumption of sugary foods was not shown to carry similar risk. One possible explanation is that the body metabolizes the sugars differently: Solid foods carry other nutrients, like fat and protein, that slow metabolism, while sugary drinks provide an undiluted influx of carbohydrates that the body must process.

The news will likely prove troublesome for the beverage industry, which has long contended with concerns that sugary drinks contribute to type 2 diabetes and tooth decay. Some cities, including Seattle, have introduced controversial "soda tax" plans that raise the sales tax on the drinks in an effort to discourage consumption.


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