Quanta Magazine reports progress on what its headline calls the “Infinite Pool-Table Problem”. The problem is explained in the article as follows:
Strike a billiard ball on a frictionless table with no pockets so that it never stops bouncing off the table walls. If you returned years later, what would you find? Would the ball have settled into some repeating orbit, like a planet circling the sun, or would it be continually tracing new paths in a ceaseless exploration of its felt-covered plane?
The article describes progress on the problem via study of ‘optimal’ billiard tables, “shapes whose particular angles make it possible to understand every billiard path that could occur within them”.
More information
New Shapes Solve Infinite Pool-Table Problem, Quanta Magazine.
via @ColintheMathmo on Twitter.