Do the sounds of dripping eaves and squelching slush heaps make you just the tiniest bit sad about winter ending? No more crunchy snow underfoot, no more picturesque flakes drifting past your window? Relegating all your sweaters and thick socks to the back of the closet? Just me? For anyone else who wants a taste of winter in the off-season—or for anyone living in less wintry climes—now there's the Icicle Atlas. Over four years, researchers at the University of Toronto grew and photographed icicles. They may seem mundane when they're sprouting from your gutters, but icicles are mysterious in how they form. Their shapes emerge from a complex set of interacting factors: air flow, water flow, the icy foundations they've already built. The scientists grew 237 icicles on an icicle growing machine with a slowly rotating dripper nozzle. The apparatus turned about once every four minutes, ensuring that conditions were the same all around the icicle. "This is the same reason you rotate the meat in a BBQ; to make all sides the same," says Stephen Morris, the physicist who supervised the project. With their icicles rotisserie-ing away, the researchers tweaked several variables—temperature, air flow rate, water flow rate, the makeup of the water—and watched the effects. "The most interesting variable turned out to be water purity," Morris says. "Impure water icicles have regular ripple patterns on their sides." Even a tiny bit of salt in the water created the ridged shape. What's more, Morris says, "We still can't explain the ripples." Scientists don't know why small impurities are enough to create the ridges, or why they're always about 1 centimeter wide. They don't even know why the ripples exist in the first place. All of the physicists' results are available on the Icicle Atlas homepage: research papers by Morris and his former PhD student Antony Chen, photos and videos of the icicles, and entire spreadsheets and tables of data. The researchers want the information to be there for anyone who wants it. That might include scientists studying fluid dynamics; artists and modelers; and even the occasional person who just misses winter. Find your icicle zen with these videos from the Atlas: Fast icicles.
Slow icicles.
Icicles with attitude.
All images and videos: Antony Chen and Stephen Morris, Nonlinear Physics, University of Toronto
