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Icicle mysteries revealed: Researchers delight in exploring the physics of ripple formations

The reason Stephen Morris studies icicles is simple. They are common and beautiful, and they make you wonder. And they are now documented online in all their chilly, wet glory in the Icicle Atlas.

Morris, a University of Toronto professor who created the atlas, is a physicist who probes the subtle underpinnings of the kinds of obvious physical phenomena people see every day.

“Being Canadian,” he said, “I see a lot of icicles.”

But not enough. And not created in controlled conditions. So he recruited a graduate student, Antony Chen, now an instructor at the Southern Alberta Institute of Technology in Calgary. Chen produced “the most elaborate study of icicle morphology ever done,” Morris said.

Their most surprising discovery was that ripples on icicles result from impurities in the water. Chen generated a lot of data, now available online at physics.utoronto.ca/Icicle_Atlas for other scientists who want to tackle some of the remaining issues.

The atlas also includes images and movies that Morris said might interest artists and do-it-yourself types who want to use a 3-D printer to make icicle ornaments, as well as people who just miss winter. A multimedia art installation is already planned for May in Toronto.

Raymond Goldstein, of the University of Cambridge, said the availability of all the data “is a fantastic service to the scientific community.”

He and Morris had worked on stalactites together, and then they turned to icicles. Goldstein, then at the University of Arizona, joined with colleagues there to come up with a “platonic theory” of how the ideal icicle shape is created.

Growing icicles in a refrigerated lab had its frustrations.

“At first they grew into really strange shapes,” he said. Without air flow, icicles grow multiple legs. So the researchers had to blow air to get them to form as single upside-down cones. Then they rotated the growing icicles to get images of all sides.

Some scientists had suggested that the ripples on the surface of icicles had to do with surface tension. Chen and Morris found out that this wasn’t the cause. When they used distilled water, no ripples formed. When they used tap water or added even tiny amounts of salt, the ripples appeared.

They do not yet understand the physics of the ripple formations. But they have uncovered some strange facts. The spacing of the ripples doesn’t seem to vary with different levels of impurities.

“The ripples have a universal wavelength of exactly 1 centimeter, no matter what you do,” Morris said. “That’s the real mystery.”

Although information gleaned from studying the formation of icicles could someday help with the management of ice formation – or the building of better house gutters, for that matter – Morris said he was motivated more by curiosity than practical applications.

“I’m kind of wired to see patterns,” Morris said. “I’m just amazed at these forms.”

He said that while many people found beauty in flowers or other natural biological phenomena, he found it in “rocks and bumpy roads and icicles.”

The Icicle Atlas includes about 237,000 pictures. Each icicle was photographed from eight different points of view, at 10 frames per second as it grew. Data on water, air flow and temperature are also available for each icicle, along with computer analyses of the shapes as the icicles grew.

Nonetheless, Morris said, “I’m not completely, grimly serious about this project.”

It’s partly just visual curiosity, and a delight in the images themselves, some of which he submits to art exhibitions. He likes to think that his pursuits capture the spirit of 19th century natural philosophers, who did not separate beauty, form, mathematics and science into different domains.

Classical physics is experiencing a renaissance, he said, “because of the tools that we have now to analyze and look at systems where there are huge amounts of data.”