Let's play (frictionless) pinball!
Channel: Nils Berglund
Date: 12/08/2021

This new episode of our #shorts shows how billiards can be used to play a version of pinball, without dissipation, gravity or any device accelerating the ball. The animation shows the trajectory of one particle in a square box that is shot at triangular grid of circular obstacles. The color of the particle changes slightly at each collision, which occur the same way a light ray is reflected off a mirror. The motion within the circular obstacles is an example of Sinai billiard, which is known to behave almost like a random walk. 

Music: Hat the Jazz by Twin Musicom is licensed under a Creative Commons Attribution 4.0 licence. https://creativecommons.org/licenses/by/4.0/
Source: http://www.twinmusicom.org/song/289/hat-the-jazz
Artist: http://www.twinmusicom.org

Current version of the C code used to make these animations: https://github.com/nilsberglund-orleans/YouTube-simulations
https://www.idpoisson.fr/berglund/software.html

Some outreach articles on mathematics:
https://images.math.cnrs.fr/_Berglund-Nils-1343_.html
(in French, some with a Spanish translation)