07/08/2018

Tadashi Tokieda extends an invitation to play.

The everyday cup of tea; the fragrant cedar balls scattered in the cupboard; the colorful paper balloon that decorates the children's room. In the hands of Japanese artist Tadashi Tokieda, these mundane objects take on new meanings that surprise and delight audiences.

On Tuesday afternoon, while presenting "Mathematics Through Toys" at the 2018 International Congress of Mathematicians (ICM), the Stanford University (USA) professor once again demonstrated why he is among the world's renowned popularizers of the discipline. This was the fourth lecture in the IMPA-Serrapilheira Cycle of Popularizing Mathematics.

In introducing Tokieda, physicist Marco Moriconi, from the Federal Fluminense University (UFF), highlighted his unusual trajectory – painter in Japan, classical philologist in France, mathematician in England – and considered that, in addition to a “fine sense of humor” and “special perspective,” he gives “extremely captivating” lectures – an observation that the audience present could confirm an hour and a half later. “His work has been crucial in the dissemination of mathematics,” he emphasized.

After demonstrating how the sound of a spoon hitting a cup changes depending on the angle chosen, Tadashi showed how the movement of small balls inside a cup "magically" changes according to the parameter of agglomeration. If there are few balls, they rotate following the direction in which the cup is moved. If there are many balls, the directions are reversed.

“In greater quantity, the rotation is transmitted. The spin becomes diffuse and propels the overall movement. If you continue to increase the number of balls, the movement becomes completely frozen,” the mathematician showed, who during the presentation used a video camera to zoom in on the objects used in the experiments and display them on two large screens.

Tadashi also surprised with two small red heptagons. “I can guarantee three things about them: they are made of the same material, they have the same mass, and the mass distribution is perfectly homogeneous,” he said. However, only one rolls. The difference between them is only one hundredth of a millimeter, which causes a bulge, making the sides slightly more rounded. “You have to convince yourself that such a small difference wouldn’t be able to cause such a big effect.”

At the end of the lecture, a long line formed. Everyone wanted to exchange a few words with the magician Tokieda. Pedro Henrique de Lima, 15 years old, a student at CEFET, was enchanted. "The most interesting thing is that he uses everyday objects to demonstrate concepts of Physics and Mathematics," he declared.

Classes from the Brazil-China School, a bilingual public institution in Niterói, also attended the lecture. Among the 90 students, friends Mariana Mendonça, 17, and Luiza de Oliveira, 17, particularly enjoyed the physics presented in the experiments. “I want to study astronomy,” said Mariana, concluding that researchers could also focus on disseminating their studies, like the Japanese teacher who teaches through play, or vice versa.