Sedov-Taylor Blast Wave

What you are seeing: a strong point explosion releases energy $E$ into a uniform medium of density $\rho_1$ . The blast wave expands self-similarly: $R(t) = \xi_0 (E t^2 / \rho_1)^{1/5}$ . Post-shock density is exactly $4\rho_1$ for $\gamma = 5/3$ .

Figure 1. Blastwave radius vs time and density jump.

log10(E / erg)51.00

log10(n / cm⁻³)0.00

WHAT TO TRY

Watch the shell sweep outward and slow: the gas piles into a thin dense rim (compression rho2/rho1 = 4 for a strong shock) that cools from white to orange to red as the shock decelerates.
The bottom plot stays a straight line of slope 2/5 on log axes: R proportional to t^(2/5), the self-similar Sedov-Taylor law that let Taylor read the Trinity bomb yield from declassified fireball photos.
Raise the explosion energy or lower the ambient density: the remnant reaches any given radius sooner, but the 2/5 slope never changes, only the line shifts.