Pointy ice-drops: How water freezes into a singular shape

A water drop that is gently deposited on a very cold surface freezes into a pointy ice-drop with a very sharp tip. The formation of this singular shape originates from the reduction of mass density during the freezing process and can be explained using a simplified model for which the universal structure of the singularity is revealed in full detail. The combination of a relatively simple, static experiment, and the accessible asymptotic analysis makes this system an ideal introduction to the topic of singularities. (C) 2012 American Association of Physics Teachers. [http://dx.doi.org/10.1119/1.4726201]