The festival proves the theorem: math is a blast!

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"Wake up, there's more math today!" That's how Bianca and Betina woke their mother on Sunday. After spending Saturday at the Math Festival, the 8-year-old twins wanted more. "They were very anxious to come back. It's really wonderful here. Even those who don't like [math] end up enjoying it," explains their mother, Rosângela do Carmo, a general services assistant.

In 2015, the National Math Festival in Washington, D.C., with support from Google and Amazon, received 20,000 visitors. Given the vast difference in realities, we dreamed that our Festival would reach 10,000 people. But not even the national strike day hindered us: almost 18,000 people from all over the country visited the Nave do Conhecimento Cidade Olímpica and the Eleva and SESC schools in Rio de Janeiro, and witnessed the proof of our theorem: mathematics is awesome!

	Leo Coelho/Divulgação/Impa
	A public school student plays on a square-wheeled bicycle during the Mathematics Festival in Rio.

At the opening, Japanese mathematician Shigefumi Mori, president of the International Mathematical Union (IMU), recounted how he was a poor student in elementary school and how the encouragement of his teachers led him to become a mathematician. In 1990, he won the Fields Medal, the Nobel Prize of mathematics. "Always encourage your students!" The IMU's Secretary-General, Norwegian Helge Holden, emphasized the enduring nature of mathematics. "Fashions change, society changes, but what the Greek mathematicians proved 2,000 years ago remains true." The two foreigners became celebrities and signed autographs for enthusiastic boys and girls. The mascot Aramat, the friendly blue macaw who loves mathematics, didn't sign autographs, but stole the show, dancing, playing, and taking photos with countless children and adults alike.

The success began earlier, with the community's response to our call for activity proposals: there were more than 270 proposals, of which 40 were selected. Contributions from Animamundi, the traveling museum of UFMG (Federal University of Minas Gerais), the Museum of Life and traveling planetarium of Fiocruz, the Fundão Project of UFRJ (Federal University of Rio de Janeiro), the Museum of Image and Sound, the Mathematics Film Club of UFF (Federal Fluminense University), SESI Mathematics, the VISGRAF laboratory of IMPA (Institute of Pure and Applied Mathematics), and many others enriched the program, making it eclectic.

The Festival offered workshops in origami, tetrahedral kites, labyrinths, music and mathematics, robotics, Lego, games, mathematics and magic, old calculating machines, games with Möbius strips, and activities for the blind and deaf. Who didn't have fun watching families juggling together in the string-twisting challenge? Everyone had a smile on their face, discovering mathematics where they least expected it. My own children came home loaded with Platonic solids made from drinking straws. And I even had to buy more straws!

The square-wheeled bicycle was an instant success. My colleague Luiz Velho's computer orchestra at IMPA had to create extra schedules to meet the demand. The +Copacabana exhibition revealed the mathematics hidden in nostalgic images of Rio. The film club curator, Professor Humberto Bortolossi from UFF, discussed the content of the films with the children on stage.

At the Imaginary international exhibition, children and adults marveled at 3D prototypes, interactive games and videos, beautiful images, and a mirror that changes the shape of objects, all within easy reach. Mothers entered warning: "You can't touch!" Volunteers had to correct them: "Yes, you can, everything here is meant to be handled with your own hands!" A 40-year-old woman exclaimed in astonishment: "Has mathematics changed that much since my school days?!"

We had memorable lectures. Tábata Pontes moved the audience by recounting how mathematics took her from Vila Missionária, on the outskirts of São Paulo, to Harvard University, and back to Brazil with projects and actions to make a difference. John Bush, from MIT, explained why it's harder to score a goal at the Maracanã than in Mexico City. Carolina Araújo, from IMPA, revealed the fingerprints of mathematics in nature: snowflakes, flowers, beehives, and much more. Pietro Pepe, Alessandra Yoko, and César Ilharco gave other beautiful examples of how mathematics shapes life trajectories and is present in the professions they have achieved.

Ralph Teixeira, from UFF – the first Brazilian to win a gold medal at the International Mathematical Olympiad – caused screams of shock when he "exploded" his own head. Pedro Malagutti made us believe in magic and the mathematics behind it. The Frenchman Étienne Ghys proved that the ball of the 2014 World Cup is actually a cube. And he gave another show explaining why famous mathematicians are interested in haute couture. The Argentinian Adrián Paenza charmed with his showman talent and warned against the mistake of teaching students to solve problems they don't have. The cool Senegalese Khadim War shattered the stereotype of the nerdy mathematician while talking about chaotic systems. The friendly Portuguese Rogério Martins taught how to calculate areas with a bicycle – with round wheels!

No one was immune. Intrigued, production, security, and food service staff would slip away to check out "Number Detectives" or "The Math Magic Circus." Children who visited with their school returned later with their families, making sure to explain everything to their parents in their own words. Two boys who had missed the last Cineclub session asked if there would be another Math Festival next year. What do you think?

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