A friend of mine asked me a question about the way that standing waves make sand on a 2D plate make pretty patterns.

So, I whipped up a quick 1D example in Mathematica.

I threw 50 randomly distributed (in x) particles at a string and let them jump around as a function of the friction on the string and a sort of faux-gravity.

I didn’t get the friction quite right of the particle / surface interaction. Probably messed up putting the energy into the particles too. But, it took 10 minutes and I got this pretty thing (pls forgive the crappy background as GraphicConverter does something weird with the colors when it converts to GIF here).