geometry

Math Monday: Magnet constructions

Math Monday: Magnet constructions

By George Hart for the Museum of Mathematics What cool things have you made with magnets lately? Anything like the above dodecahedral construction? These geometric sculptures are the creations that resulted from Robert Hodgin playing with thousands of small magnetic spheres and cylinders. I especially like his geometric forms which remind me of Ernst Haeckel’s […]

Math Monday: Hexagonal stick arrangements

Math Monday: Hexagonal stick arrangements By George Hart for the Museum of Mathematics Interpenetrating hexagonal arrangements of sticks are a challenging mathematical exercise to assemble from pencils. Four different directions are used, as color-coded here. The above sculpture, 72 Pencils, has tiny dots of glue to hold itself together, but you can easily use eight […]

World’s first aperiodic tiling with a single shape

World’s first aperiodic tiling with a single shape

The problem of tiling a plane has fascinated builders and mathematicians alike since time immemorial. At first glance, the task is straightforward: squares, triangles, hexagons all do the trick producing well known periodic structures. Ditto any number of irregular shapes and combinations of them.

A much trickier question is to ask which shapes can tile a plane in a pattern that does not repeat. In 1962, the mathematician Robert Berger discovered the first set of tiles that did the trick. This set consisted of 20,426 shapes: not an easy set to tile your bathroom with.

With a warm regard for home improvers, Berger later reduced the set to 104 shapes and others have since reduced the number further. Today, the most famous are the Penrose aperiodic tiles, discovered in the early 1970s, which can cover a plane using only two shapes: kites and darts.

The problem of finding a single tile that can do the job is called the einstein problem; nothing to do with the great man but from the German for one– “ein”–and for tile–“stein”. But the search for an einstein has proven fruitless. Until now.