The new Chalkdust T-shirt

Have you been wondering what the pattern on it means?

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If you’ve been to one of our issue 07 launch events or you’ve been keeping an eye on Twitter, you may have spotted the new Chalkdust T-shirt. If you like it, you can order one here!

Whether or not you’d seen it before, you’re probably wondering what the pattern on the T-shirt means… Wonder no more, we’re about to reveal all in this blog post. If you’d like to try to work it out yourself then stop reading now; spoilers ahead.

The pattern on the new T-shirt is a position in John Conway’s Game of Life. Life is a cellular automaton that was invented by John Conway in 1970, and popularised soon afterwards by Martin Gardner.

In Life, cells on a square grid are either alive or dead. In this post and on the T-shirt, we use white for alive cells and black (or the colour of the T-shirt) for dead cells. Life begins at generation 0 with some cells alive and some dead. The aliveness of a cell in the following generations is determined by the following rules:

  • Any live cell with four or more live neighbours dies of overcrowding.
  • Any live cell with one or fewer live neighbours dies of loneliness.
  • Any dead cell with exactly three live neighbours comes to life.

These three simple rules leads to some surprisingly complicated behaviour.

The pattern to the left is called a glider. This is because as the generations progress it glides across the grid. You can see what I mean in the GIF below.

Another fan favourite is Gosper’s glider gun, which is shown below. It is called Gosper’s glider gun as it fires gliders across the grid, and it was discovered by Bill Gosper.

But before we get too distracted by all the things you can make in Life, let’s get back to the T-shirt.

The T-shirt shows a position in Life. But it’s not just any old position: if you go forward one generation, you get the following:

If you like that, you can buy a T-shirt with it printed on here! You can also use this tool to write any word/phrase you like in Life.

Of course, you could continue to look at what happens to the T-shirt’s pattern after more generations. Unfortunately, not much of interest happens:

Matthew Scroggs is a PhD student at UCL working on finite and boundary element methods. His website, mscroggs.co.uk, is full of maths and now features a video of him completing a level of Pac-Man optimally.
Twitter  @mscroggs    Website  mscroggs.co.uk    + More articles by Matthew

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