The diffusion equation is a blurry snapshot of a crowd of particles: on it, a disturbance spreads across the entire Universe instantly, defying the theory of relativity. The mystery deepened by its link to the growth of entropy (a measure of disorder). But if you increase the sharpness — zoom into the micro level — each particle moves according to Einstein's laws, and there's no violation. The apparent faster-than-light speed is an artifact of poor resolution.
Old paradoxes arose from a wrong angle: math allowed 'snapshots' impossible to get in reality. In the real world, a signal always travels slower than light — you need to catch it not by heat, but by the motion of the particles themselves.
🎯 The thermal speed of water molecules is about 500 m/s, which is 600,000 times slower than light. In practice, diffusion never actually violated the theory.