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Evolution of Icicles

As the holiday season winds down, the weather in many parts of the world remains frightful. In particular, large, sharp icicles often form on gutters, trees and vehicles. Icicles are usually harmless reminders of winter, but they can present huge problems, especially for utility workers faced with power lines that fail under the weight of ice.


In a recently published article on NewScientist, author Michael Brooks explores the applications of physics research on icicle formations. With a better understanding of how icicles grow, scientists hope to provide applicable information for architects, utility workers and even Hollywood CGI specialists.

Over the past year, scientists have learned quite a bit about the evolution of icicles—a field still in its infancy. For instance, physicists from the University of Toronto found that the purity of water can dramatically change the growth of icicles. Pure water tends to lead to icicles that taper nicely into a sharp point. When the scientists used tap water, however, the icicles had more ripples and had large protrusions near the top. These results surprised researchers who generally thought that minor impurities in tap water wouldn't affect the growth of an icicle.

To create these icicles, the scientists created a special icicle growing apparatus. Inside the device, air was constantly circulated and kept at the same temperature while near-freezing water was provided from an external reservoir. In addition to the unforeseen affect of impure water, scientists were able to create several branching icicles with multiple tips. These multi-pronged icicles were more likely to form when the air was still.

Icicles formed in still air are more likely to branch. Image Courtesy Antony Chen/Stephen Morris/University of Toronto. Image Copyright: American Physical Society.

These results contradicted a long-held belief that icicles tend to form self-similar shapes, meaning that the circumference and length are always proportional.

So who can benefit from icicle research? Architects, for instance, have been interested in icicle growth to better design buildings that make it difficult for dangerous stalactites to form easily. Also, CGI experts have increasingly been interested in modeling icicles over time. As reported in the NewScientist article, CGI experts consulted icicle experts for a deleted scene of Superman Returns.

Top image credit: Hans. A Rosbach via Wikipedia.

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