A powerful mathematical technique is used to model melting ice and other phenomena. But it has long been imperiled by certain “nightmare scenarios.” A new proof has removed that obstacle. Introduction Imagine an ice cube floating in a glass of water. Eventually, it will melt down to a tiny frozen speck before disappearing. As it shrinks, its surface gets smoother, and any irregularities or sharp edges gradually vanish. Mathematicians want to understand this process in greater detail, to be able ...