For decades, the restless drift of Arctic sea ice defied the equations built to predict it — moving too fast, too slow, spreading too reluctantly. A team of researchers has now found that the answer was hidden not in the wind, but in the collisions between the ice itself: floe bumping against floe, transferring energy, acting as a collective brake on a system that science had long tried to understand through simpler means. By borrowing a framework from the physics of granular materials, they have offered climate science a more honest portrait of how the Arctic moves — and, as the ice continues