April 18, 2021. Cracks in a drying mud puddle form a network of T-intersections. A parent crack generates a baby crack, so in principle, we can read off the history of the puddle. In practice, this history is almost never unique, and instead leads us to a computationally intractable problem in order theory.
The surface of a drying mud puddles contracts as water evaporates. This creates a stress on the surface, relieved by introducing cracks. These cracks will form from microscopic flaws in the surface, described by fracture mechanics, and in particular criteria for failure developed by A. A. Griffith and modified by G. R. Irwin.
Thanks to Sarah Alexander for suggesting I investigate mud puddles.