🦊 Fennec Fox Desert Burrow: How Sand Damps the Daily Heat Wave and Gives a Cool Night Refuge Lab

A cut-away of desert sand shows the daily heat wave creeping downward by conduction: amplitude falls as exp(-z/d) and the peak is delayed by z/d radians. A Crank-Nicolson solver is checked against the exact Fourier solution, and a fennec fox's den depth, soil type and schedule change its chamber temperature and illustrative water budget.