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# What Exactly Is Curling?

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Olympic curling has taken to the ice, but if you're like most Americans, this writer included, the game is a bit baffling. Here's a quick, stripped-down primer on everyone's favorite icy alternative to shuffleboard. It doesn't cover anywhere near all of the game's nuances, but it should give you enough info that you can enjoy watching an end or two. (And yes, you'll learn what an "end" is.)

#### WHAT'S THE OBJECT OF CURLING?

Good question. First, let's get a bit of the jargon down. The playing surface in curling is called "the sheet." Sheet dimensions can vary, but they're usually around 150 feet long by about 15 feet wide. The sheet is covered with tiny droplets of water that become ice and cause the stones to "curl," or deviate from a straight path. These water droplets are known as "pebble."

At each end there's a target that looks like a big bullseye. These targets are known as "the houses." The center of the house is known as the "button." Basically, the object of the game is to get your stones closer to the button than the other team gets theirs.

#### WHAT'S WITH THE SWEEPING?

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Remember how we talked about the pebble of ice droplets that the rock has to travel across? When the stone touches the pebble, there's friction, which can slow down the stone and makes it curl away from its straight path to the house.

Obviously, that friction is not always a good thing, but sweeping helps combat the problem. The sweeping motion raises the temperature of the ice by a degree or two, which diminishes the friction between the pebble and the stone and keeps the stone moving in a straight line.

#### WHAT ABOUT ALL THE YELLING?

Each curling team has four members: a lead, a second, a vice-skip (or third), and a skip. Each "end" (curling's equivalent of a baseball inning) involves both teams shooting (or "delivering") eight stones at the house, with players delivering two stones apiece.

When the lead, second, and vice are delivering their stones, the skip stands at the opposite end of the sheet (near the house) and uses his broom to give his teammates a target for their deliveries. Once the stone has been delivered and is a "running stone" (that is, one that's still sliding), the skip then yells to the sweepers to let them know when to sweep and how hard. When the skip shoots the last two stones of a team's end, the vice takes over calling the shots.

#### HOW DO YOU KEEP SCORE?

In each end, both teams send eight stones down the sheet. Once all 16 stones have been delivered, the team with the stone that's closest to the button (center of the house) effectively "wins" the end. Only this team will earn any points for the end. It gets a point for each of its stones that are in the house and closer to the button than the other team's closest stone. Since the team that won the end always has at least one stone that's closer to the button than their opponent, the team always scores at least one point, and could score up to eight points.

If neither team manages to keep a stone in the house during an end, it's known as a "blank end," and no points are scored. Olympic curling matches last for 10 ends unless there is a tie, in which case it goes to extra-ends, curling's equivalent of overtime.

#### WHAT'S THE HAMMER?

As you might have guessed from reading about the scoring system, throwing the last stone of an end is a huge advantage. If you've got the last stone, you can always try to knock the other team's best stone away from the button. If a team holds the last stone for an end, it "has the hammer," and should probably be able to score some points. If the team without the hammer manages to somehow stymie their opponent and score points, it's called a "stolen end." Whichever team fails to score points in an end gets the hammer for the next end.

#### SO IS THERE STRATEGY INVOLVED?

Yes, there's all sorts of strategy in curling. Let's say your team doesn't have the hammer. You're at a huge disadvantage when it comes to scoring points, so you might opt to play defensively. To do that, you might just deliver a number of "guards," or rocks that will sit in front of the house and provide an obstacle for the other team's stones. Alternatively, guards can be used to defend your stones that are already in the house from being knocked out by the other team's "takeout" shots.

The third major type of curling shot is the "draw," a shot that's meant to avoid other stones and come to rest in the house. Generally, a draw is used with the hope of scoring points, a guard is thrown to protect the house or a stone that's already been thrown, and a takeout is used defensively.

#### MAY I SEE A CLIP?

Yes you may.

This post was originally published in 2010.

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Big Questions
Why Is the American Flag Displayed Backwards on Military Uniforms?
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In 1968, famed activist Abbie Hoffman decided to crash a meeting of the House Un-American Activities Committee in Washington by showing up in a shirt depicting the American flag. Hoffman was quickly surrounded by police, who ripped his shirt off and arrested him for desecration of the Red, White, and Blue.

Hoffman’s arrest is notable today because, while it might be unpatriotic to some, wearing the American flag, burning it, or otherwise disrespecting it is not a violation of any federal law. In 1989, the Supreme Court ruled that it would be unconstitutional to prosecute any such action. Still, Americans have very fervent and strict attitudes toward displaying the flag, a longstanding symbol of our country’s freedom. According to the U.S. Flag Code, which was first published in 1923, you shouldn’t let the flag touch the ground or hang it upside-down. While there’s no express prohibition about reversing the image, it’s probably a safe bet you shouldn’t do that, either.

Yet branches of the U.S. military are often spotted with a seeming mirror reflection of the flag on their right shoulder. If you look at a member in profile, the canton—the rectangle with the stars—is on the right. Isn’t that backwards? Shouldn’t it look like the flag on the left shoulder?

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Not really. The flag is actually facing forward, and it’s not an optical illusion.

When a service member marches or walks forward, they assume the position of a flagpole, with the flag sewn on their uniform meant to resemble a flag flapping in the breeze. With the canton on the right, the flag would be fluttering behind them. If it were depicted with the canton on the left, the flag would be flying backward—as though it had been hung by the stripes instead of the stars nearest to the pole. The position of the flag is noted in Army Regulation 670-1, mandating the star field should face forward. The official term for this depiction is “reverse side flag.”

As for Hoffman: His conviction was overturned on appeal. In 1970, while at a flag-themed art show in New York, he was invited to get up and speak. He wore a flag shirt for the occasion.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Big Questions
What Causes Sinkholes?
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This week, a sinkhole opened up on the White House lawn—likely the result of excess rainfall on the "legitimate swamp" surrounding the storied building, a geologist told The New York Times. While the event had some suggesting we call for Buffy's help, sinkholes are pretty common. In the past few days alone, cavernous maws in the earth have appeared in Maryland, North Carolina, Tennessee, and of course Florida, home to more sinkholes than any other state.

Sinkholes have gulped down suburban homes, cars, and entire fields in the past. How does the ground just open up like that?

Sinkholes are a simple matter of cause and effect. Urban sinkholes may be directly traced to underground water main breaks or collapsed sewer pipelines, into which city sidewalks crumple in the absence of any structural support. In more rural areas, such catastrophes might be attributed to abandoned mine shafts or salt caverns that can't take the weight anymore. These types of sinkholes are heavily influenced by human action, but most sinkholes are unpredictable, inevitable natural occurrences.

Florida is so prone to sinkholes because it has the misfortune of being built upon a foundation of limestone—solid rock, but the kind that is easily dissolved by acidic rain or groundwater. The karst process, in which the mildly acidic water wears away at fractures in the limestone, leaves empty space where there used to be stone, and even the residue is washed away. Any loose soil, grass, or—for example—luxury condominiums perched atop the hole in the ground aren't left with much support. Just as a house built on a weak foundation is more likely to collapse, the same is true of the ground itself. Gravity eventually takes its toll, aided by natural erosion, and so the hole begins to sink.

About 10 percent of the world's landscape is composed of karst regions. Despite being common, sinkholes' unforeseeable nature serves as proof that the ground beneath our feet may not be as solid as we think.

A version of this story originally ran in 2014.

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