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NGSS: Core Idea: PS2.A

CCSS: Reading Informational Text: 1

TEKS: 6.8B, 7.3A, 8.6A, P.4D

Tower Power

Teams in Spain build soaring human towers in hopes of rising above the competition

SEAN GALLUP/GETTY IMAGES

WAY UP THERE: These helmeted kids—the lightest members of the team—scale the tower’s trunk and form the crown. The smallest child will climb to the very top.

AS YOU READ, THINK ABOUT the challenges teams face as they try to build taller and taller human towers.

Scholastic editor Karina Hamalainen first visited Tarragona, Spain, when she was 17 years old—and she saw a spectacle she’ll never forget. She watched from a balcony window as groups wearing matching colored shirts, white pants, and black sashes around their waists swarmed into the street below. Music began to play. The members of one group braced themselves against each other in a large circle made of hundreds of bodies. Then some of their teammates climbed barefoot onto their shoulders.

Scholastic editor Karina Hamalainen was 17 years old when she first visited Tarragona, Spain. From a balcony window, she watched a display she’ll never forget. People streamed into the street below. Groups wore matching colored shirts, white pants, and black sashes around their waists. Music began to play. The members of one group braced themselves against each other. They formed a large circle made of hundreds of bodies. Then some of their teammates climbed barefoot onto their shoulders.

COURTESY OF NATALIE SMITH

EYEWITNESS: Seeing human towers being built has been a highlight of Scholastic editor Karina Hamalainen’s many trips to Spain.

People continued to scramble up the rising human tower, adding more and more levels. Finally, a few small children scaled all the way to the top. One stood proudly at the highest point and raised her hand in salute. Spectators crowded in the square erupted into cheers. The children then shimmied down the tower, followed by a cascade of fellow climbers from the highest to lowest level, until the structure was completely dismantled. “It was like a waterfall of people,” says Hamalainen.

What Hamalainen had witnessed was the Spanish tradition of building castells—the Catalan word for “castles.” Teams of castellers, or “castle makers,” in Spain’s northeastern Catalonia region have been constructing these human towers since the 1700s (see Catalan Culture). Back then, a five-level tower was an impressive feat. But today, the most highly skilled teams can reach 10 levels.

People kept climbing the rising human tower. They added more and more levels. Finally, a few small children scaled all the way to the top. One stood proudly at the highest point and raised her hand in salute. The crowd in the street cheered. Then the children slid down the tower. Their fellow climbers followed, from the highest to lowest level. Quickly, the structure came completely down. “It was like a waterfall of people,” says Hamalainen.

Hamalainen had just seen the Spanish tradition of building castells. That’s the Catalan word for “castles.” Teams of castellers, or “castle makers,” form these human towers. They’ve been doing this in Spain’s northeastern Catalonia region since the 1700s. Back then, a five-level tower was a huge feat. But today, the most highly skilled teams can reach 10 levels.

SEAN HODRICK/ALAMY STOCK PHOTO

TEAMWORK: Collaboration is the key to building a towering castell.

Today, castellers build human towers for town festivals and national celebrations. Some teams occasionally participate in competitions too. Their goal is to build the tallest, most complicated castell without it collapsing. Castellers need to be brave, skilled at climbing, and strong—but that’s not all. Teams have to develop strategies to work together to create stable formations that can withstand the forces trying to topple them.

Today, castellers build human towers for town festivals and national celebrations. Some teams enter competitions too. Their goal is to build the tallest, most difficult castell without it falling. Castellers need to be brave, good at climbing, and strong. But that’s not all. Teams must develop plans to work together to create stable towers. These structures have to stand firm against the forces trying to topple them.

SHARING THE LOAD

Castells can take many shapes, but they all have three basic parts (see Engineering a Castell). The base, or bottom level, contains the most people, sometimes hundreds. The trunk consists of several levels and rises from the center of the base. The crown sits on top. It’s usually formed by kids who are light enough for those below to easily support.

Large human towers may appear to put an overwhelmingly heavy burden on the castellers on the lowest level. But Josep Soler, a mechanical engineer and former casteller in Catalonia, says the combined load pushing down on them isn’t as crushing as it looks. “The people at the base work together as a team so that forces are divided among them,” he says. To share the load, the castellers at the center of the base intertwine their arms into carefully planned positions. Hundreds of teammates then surround them, arranging their bodies into an organized pattern that provides support inward and upward. All that pushing toward the center helps counteract the downward force of the weight of the trunk and crown.

Castells can take many shapes, but all have three basic parts. The base is the bottom level. It contains the most people, sometimes hundreds. The trunk has several levels. It rises from the center of the base. The crown sits on top. Kids usually form the crown, because they’re light. It’s easier for those below to hold them up.

Large human towers are very heavy. They may appear to put an impossible burden on the castellers at the bottom. But the combined load pushing down on them isn’t as crushing as it looks, says Josep Soler. He’s a mechanical engineer and former casteller in Catalonia. “The people at the base work together as a team so that forces are divided among them,” he says. The castellers at the center of the base thread their arms into certain positions. That helps them share the load. Then hundreds of teammates surround them. They place their bodies in a pattern that pushes inward and upward. As they push toward the center, this helps offset the downward force of the tower’s weight above them.

The bases for the tallest castells have two or three levels to disperse, or spread, the structures’ entire weight over a wide area. Architects used a similar strategy when designing ancient cathedrals by adding supporting structures called flying buttresses. These external arches push against a cathedral’s outer walls, taking on some of the load to prevent the building from buckling under its own weight. Adding levels to a castell’s base accomplishes the same thing, says Dr. Jaume Rosset. He’s a casteller who practices sports medicine at the Institute of Physiology and Medicine of Art in Terrassa, Spain.

The bases for the tallest castells have two or three levels. That helps to disperse, or spread, the towers’ entire weight over a wide area. Architects used a similar idea on ancient cathedrals. They added structures called flying buttresses for support. These arches push against a cathedral’s walls from the outside. They take on some of the load, so the building doesn’t cave in under its own weight. Adding levels to a castell’s base does the same thing, says Dr. Jaume Rosset. He’s a casteller who practices sports medicine at the Institute of Physiology and Medicine of Art in Terrassa, Spain.

MAJA HITIJ/GETTY IMAGES

IT’S A HANDLE: The wide black sashes worn by castellers serve as grips to help team members climb.

BALANCING ACT

Supporting a tower’s immense weight is just one challenge castellers face. They also need to make sure a tower remains stable as it rises higher and higher. “The difficulty is not only how much load I will sustain on my body but also that this load will be moving during the construction of the tower,” says Rosset.

Castellers strive to keep the tower’s center of mass—the point around which an object’s mass is evenly distributed—balanced directly over the levels below them. As team members ascend the tower, they don’t want to make it shift or sway. Climbers try to align their weight close to the middle of each body they’re climbing over. That way the castell’s center of mass doesn’t tilt too far to one side. Too much tilt could cause the whole tower to collapse.

Castellers must support a tower’s great weight. But that’s just one challenge they face. They also need to keep the tower stable as it rises higher and higher. “The difficulty is not only how much load I will sustain on my body but also that this load will be moving during the construction of the tower,” says Rosset.

The tower’s center of mass is the point around which its mass is evenly spread. Castellers work to keep this point balanced over the lower levels. So team members climb the tower carefully. They don’t want to make it shift or tilt. Climbers try to keep their weight close to the middle of each body they’re climbing over. That way, the castell’s center of mass doesn’t tilt too far to one side. Too much tilt, and the whole tower could fall.

Falling is a risk for castellers and another reason a tower’s base contains so many people—up to 600 castellers for the tallest towers. “They act as a human mattress,” says Rosset. When a castell tumbles—which happens in about 3 percent of attempts—the people in the lower levels absorb the impact of their falling teammates, preventing them from hitting the ground with full force. The youngest—and highest-climbing—members of a castell team also wear helmets for extra safety.

Falling is a risk for castellers. It’s also another reason to have so many people in the base. The bases of the tallest towers contain up to 600 castellers. “They act as a human mattress,” says Rosset. A castell falls in about 3 percent of tries. When that happens, the people in the lower levels absorb the fall of their teammates. This saves the climbers from hitting the ground with full force. The youngest members of a castell team are also the highest climbers. They wear helmets for extra safety.

ALBERT GEA/REUTERS

A STURDY BASE: A group of castellers intertwine their bodies to create a strong, stable base for a human tower.

BEHIND THE SCENES

Depending on its size, a castell can take less than 10 minutes to build and dismantle. But the preparations that go into its construction require years of hard work. Teams usually train several times a week. “It took me about four months to learn the basics of making the castell, but I still have a lot more to learn,” says 12-year-old Arnau, who belongs to a castell team in Barcelona. His position is at the top of the trunk, alongside teammate Ainara, 14. When it comes to climbing, she admits, “I feel a little scared and nervous at times. But being on the team is an incredible experience!”

It’s also an incredible experience to watch a castell take shape, says Hamalainen, the Scholastic editor. She’s witnessed many castell events since that first one years ago, and she’s still in awe. Rosset, the casteller, feels the same way. Even after spending years building castells and studying the science behind them, he hasn’t lost his sense of wonder. “For me, it’s still magical,” he says.

A castell can take less than 10 minutes to build and take apart. That depends on its size. But preparing to build it takes years of hard work. Teams usually train several times a week. “It took me about four months to learn the basics of making the castell, but I still have a lot more to learn,” says 12-year-old Arnau. He belongs to a castell team in Barcelona. He climbs to the top of the trunk, next to his teammate Ainara, who is 14. When it’s time to climb, she says, “I feel a little scared and nervous at times. But being on the team is an incredible experience!”

It’s also an incredible experience to watch a castell take shape, says Hamalainen, the Scholastic editor. She’s seen many castell events since that first one years ago. And she’s still amazed. Rosset, the casteller, feels the same way. He’s spent years building castells and studying the science behind them. But he hasn’t lost his sense of wonder. “For me, it’s still magical,” he says. 

LUCAS VALLECILLOS/VWPICS/REDUX

BIG EVENT: A child reaches the peak of a castell at an event in an arena in Tarragona, Spain.

CONSTRUCTING EXPLANATIONS: Describe the forces that make it tricky to maintain a human tower’s balance.

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