Water and cold air not required. (-:
From the University of Toronto:
Anyone who might be dreading the end of winter or cannot wait until it arrives again can now enjoy the beauty and mystery of icicles all year long with the Icicle Atlas.
A giant trove of data on icicle shapes and growth, the atlas contains more than 230,000 images as well as hundreds of time-lapse movies of icicles grown under controlled conditions in the laboratory. It’s all free for download by anyone, thanks to years of research by physicists at the University of Toronto.
“I expect to be surprised by what uses people find for it,” said Stephen Morris, a professor in U of T’s department of physics who, with former graduate student Antony Chen, has been studying icicle morphology for several years.
An icicle’s shape is a chicken-and-egg scenario between the flow of super-cold water and an evolving shape. The shape determines the flow and flow determines the shape, which makes explaining the icicle’s emergent shape tricky.
Icicle Atlas: The Videos