whatThe Belousov-Zhabotinsky dish in ink: an excitable medium where every point can burn once, then must rest. Pacemaker sites fire on their own clocks and send out target rings; a whisper of noise sometimes breaks a front, and the broken ends curl into spirals that never die.

whyThe claim: colliding rings ANNIHILATE. Chemical waves are not light -- a front is a fire that eats its fuel, so where two fronts meet, each starves the other, both vanish, and nothing passes through. It is measured against a non-interacting control: the same two rings run alone in private dishes, their burning areas summed. Together is strictly less than apart, and after the meeting exactly ONE merged front remains where superposition would keep two. The second claim rides the noise: break a front and its free ends curl inward -- a spiral, the reaction's immortal scar. Click anywhere to drop a pacemaker of your own.

howA Greenberg-Hastings excitable lattice with a circular weighted ignition kernel (radius 3) and PROBABILISTIC ignition near threshold -- stochastic rounding is what dissolves the lattice's compass and makes the rings round (anisotropy measured at 0.8 percent); three burning ticks, ten of ash; noise adds a 1.5 percent ignition failure and rare spontaneous sparks. The annihilation and spiral trials run noise-silenced on a sealed dish so the control is exact. Everything seeded.