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Marcos André via Flickr Creative Commons // CC BY 2.0

Scientists Explain How Your Shoes Untie Themselves

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Marcos André via Flickr Creative Commons // CC BY 2.0

You know you tied your shoelaces properly. You know you did. Yet halfway down the block, you feel your sneaker slipping away from your foot. How could a knot untie itself? Scientists using slow-motion cameras may have figured it out. They published their report in the journal Proceedings of the Royal Academy A.

There are two classic shoelace knots. There’s the “rabbit comes out of the hole, runs around the tree, and returns to his hole” loop-and-pull, and then there’s the crossed-loop bunny ears approach. (Rabbits have apparently cornered the market on shoelace knots.) Both knots are prone to unraveling under strain, although bunny ears are generally considered the more secure option.

Mechanical engineers at Berkeley wondered what was producing the two knots’ different success rates. Their interest, said co-author Christopher Daily-Diamond, goes well beyond untied cross-trainers. “If you can start to understand the shoelace,” he said in a statement, “then you can apply it to other things, like DNA or microstructures, that fail under dynamic forces. This is the first step toward understanding why certain knots are better than others, which no one has really done."

The first step was to catch the knots in the act of coming undone. The researchers trained a high-speed camera on a treadmill, then co-author and runner Christine Gregg put on her sneakers and got moving.

By slowing down the camera and analyzing the physics of Gregg’s footfalls, the research team was able to spot the conspirators tugging away at those poor, unsuspecting knots. The first was the violence of each footfall, as Gregg’s shoes smacked against the treadmill with seven times the force of gravity. This impact stretched and pushed the knot. And while it was weakening, the whipping motion of the bow’s loops and ends simultaneously pulled the strands apart. These two forces combined untied Gregg’s well-formed knots.

"You really need both the impulsive force at the base of the knot and you need the pulling forces of the free ends and the loops," Daily-Diamond said. "You can't seem to get knot failure without both."

The researchers noted that knot failure is not inevitable; often it takes one specific jolt to the laces to start the unraveling clock. “[Your] laces can be fine for a really long time,” Gregg said, “and it's not until you get one little bit of motion to cause loosening that starts this avalanche effect leading to knot failure.”

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Neil deGrasse Tyson Just Answered the Game of Thrones Question That Everyone's Asking
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HBO

Serial debunker of movies and TV Neil deGrasse Tyson took on Game of Thrones on Sunday evening, analyzing everything from the chains the army of the dead used to pull up dead dragon Viserion (wrong angle) to the dragons themselves (good wing span, though experts we spoke with say they're still too heavy to fly). And then he dropped an intriguing tweet that just might explain Ice Viserion's blue fire, which easily cut through the Wall:

Inverse's Yasmin Tayag took a deep dive into the physics of dragon fire after the season finale and concluded that, according to science, blue flames are the hottest of them all. Typical Game of Thrones dragon fire—the red, yellow, and orange kind—is the result of incomplete combustion. The color is caused by the fuel in the dragon's gut (likely carbon) releasing chemicals as gas in a process known as pyrolysis. Blue flames, though, mean complete combustion, which, according to Tayag, "can only occur when there’s plenty of oxygen available to allow a flame to get super hot, and the fuel being burned doesn’t release too many additional chemicals during pyrolysis that might lead to a different colored flame."

In August, Game of Thrones sound designer Paula Fairfield—perhaps in an attempt to answer viewers’ nagging question about whether Viserion was blowing fire or ice—told Vanity Fair’s Joanna Robinson that, “He’s just going at it and slicing with this. It's kind of like liquid nitrogen. It’s so, so cold. So imagine if that’s what it was, but it’s so cold it’s hot. That kind of thing.”

This could have big consequences if Ice Viserion and Drogon face off. "If the HBO series decides to follow these particular laws of thermal physics (and why should it when Thrones so flagrantly disregarded chain physics?!?), then Viserion will surely be at an advantage if and when he ever goes talon-to-talon with his brother Drogon," wrote Robinson in response to deGrasse Tyson’s tweet.

Game of Thrones's final season won't debut until late 2018 or 2019, so we have a long time to wait before we see which dragon's fire comes out on top. 

[h/t: Vanity Fair]

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MasterClass
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Attention Aspiring Filmmakers: Martin Scorsese Is Teaching an Online Class
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MasterClass

Since launching his career 50 years ago, Martin Scorsese has inspired countless fans to get into the moviemaking business. Now aspiring directors looking for a place to start can receive guidance from the legendary director himself. Beginning early next year, Martin Scorsese will lead his own filmmaking course through the online education platform MasterClass.

MasterClass is best known for offering classes taught by instructors who have already risen to the top of their respective fields. An architecture course from Frank Gehry, a music composition course from Hans Zimmer, and a tennis course from Serena Williams are just a few of the listings in the catalog. The company has also recruited several famous filmmakers in the past, including Aaron Sorkin and Werner Herzog, but Scorsese—the iconic director behind such classics as Taxi Driver (1976), Raging Bull (1980), and Goodfellas (1990) is in a league of his own.

Scorsese’s MasterClass includes more than 20 video lessons that pupils will be able to watch at their desired pace. They will also have the chance to upload their own videos and receive feedback from classmates, with Scorsese answering select questions.

"I was excited by this project because it gave me a chance to pass down my own inspirations and experiences and practices and evolutions,” the Oscar-winning director said in a release. “It was so important for me to have people that passed down their own knowledge when I was young, and MasterClass has given me an opportunity to try it myself.”

Prospective students can pre-enroll for $90 today to receive unlimited access to the course when it goes live in 2018.

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