# You're reading: Phil. Trans. Aperiodic.

x

It’s an unpresupposing little letter, $x$. In fact, that’s the reason we use it to represent something we don’t know. But how do you write it down? When Vijay Krishnan tweeted a link to an American college professor’s page on mathematical handwriting, I was shocked to learn that he thought adding a hook to a simple cross was sufficient to differentiate letter-$x$ from times-$\times$.

So I asked our Twitter followers how they write $x$. The Cambrian explosion of diversity in answers I received was eye-opening – I’m glad I asked!

### A glider on an aperiodic cellular automaton exists!

Good news, everyone! I literally jumped out of my seat and punched the air when I saw this story. It’s as if this site was set up specifically to report on this exact piece of news.

### Open Access Round Up

The march of the righteous towards victory over the rent-seeking publishers continues apace, so here’s another Open Access round up. I’m not even going to bother trying to remain impartial any more, for the following reasons:

### ‘RightingBot’ simulates the way lizards right themselves when falling

RightingBot. Credit: Tom Libby

Lizards, just like cats, have a knack for landing on their feet when they fall. But unlike cats, which twist and bend their torsos to turn in the air, lizards swing their large tails one way to rotate their body the other, according to a recent study. And the longer the tail, the smaller the movement needed. The study used high-speed video, developed a mathematical model and finally used this to develop a lizard-inspired robot, called ‘RightingBot’, which replicates the feat.

### Out-of-work economists will probably not turn to bank robbery

Three economists decided to examine bank robbery as an economic activity. They were given access to data from the British Bankers’ Association on the amounts stolen during robberies, pretended to be statisticians for a bit, and came up with some interesting results. They’ve written up their findings in a feature article in the June edition of Significance.

Photo courtesy Orange County Archives.

### Redrawing the map of Great Britain from a network of human interactions

This is just about the most right-on, 21st-century paper and associated PR I’ve seen this year. MIT’s SENSEable City Lab has produced this little video to go with a paper by some of their researchers, led by Carlo Ratti: