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## Ammann’s Golden b

Most tilings we see are periodic (see wallpaper groups). In a periodic tiling, you can find two points where the tiling looks identical. In fact, if there are two, there will be infinitely many such [/latexpoints.

Mathematicians discovered aperiodic tilings in the 1960s. Aperiodic tilings must be able to tessellate (i.e. fill in) the entire plane, and use only a fixed number of tile types. Most importantly, any tessellation with the tiles must be non-repeating in this sense: pick any two points in the tessellation, and the tiling must look different at those points.

Robert Ammann was an early researcher in aperiodic tilings. Remarkably, he was not a professional mathematician—he was a postal worker with a passion for discovering new tilings. One of the tilings he discovered is based on a single tile shape, in two different sizes. The ratio of the area of the larger tile to the smaller is the golden ratio, $$\phi \approx 1.618$$. Note that the tile is shaped like a chunky letter b, hence the affectionate moniker “Golden b.”

If we take the shortest side of the smaller tile to be one unit long, then we get the other sides by successively multiplying by $$\sqrt{\phi}$$. And we create the larger tile by scaling all side lengths by $$\sqrt{\phi}$$.

The elliptical markings on the tiles enforce a matching rule. So, for example, you might combine the two tiles above to create this:

And behold! It is another, larger, Golden b. This suggests you can combine it with the larger tile to create a still larger Golden b.

As you build a tessellation with the Golden b, the ratio of the number of large to small tiles converges to—you guessed it, the golden mean.

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## A shared hobby created

I’ve had a few careers, all of them motivated by curiosity. Flying airplanes, writing software, financial engineering all provided a creative outlet, but as jobs go, that creativity was necessarily narrowly focused. I always enjoyed teaching, and figured I might take it up when I had explored enough other careers. To my surprise, I discovered teaching high school was the job that really indulged my creative side in the most general way. I taught high school math, physics, and computer science. Teaching computer science in particular enabled me to explore a trove of interesting problems to solve with the students. We wrote games in Scratch, constructed enormous structures in Minecraft using Python and Javascript, and sketched dynamic and interactive visualizations with Processing (and later p5.js).

Processing was especially inspiring. I used its pdf library to algorithmically generate drawings. It was this, combined with a visit to Ann Arbor’s MakerWorks, that ultimately led to Cherry Arbor Design.

MakerWorks has an array of maker tools, but I was drawn to the laser cutter, because I could see how the drawings created in Processing could be turned into precise wood or acrylic representations.  When I brought my creations home, Heidi was immediately intrigued with the possibilities. We started having our date nights at MakerWorks (yep, we’re nerds), creating earrings and other small items from thin cherry and maple boards, colorful acrylic, and Baltic birch plywood. Eventually, so that we could have unlimited access, we decided to buy a laser cutter. I still do most of my work with Processing and pf.js, while Heidi prefers Affinity Designer, an alternative to Adobe Illustrator.

Today, Heidi and I spend much of our time together making things, and further developing our design skills. We are all about nonstop learning, so at the moment, we’re taking a PhotoShop class at the local community college.