LOOK closely at any icicle and you’ll see that it carries a series of circular ridges, just 8 millimetres apart. It’s the same no matter how big or cold the icicle, or how much water trickles down. But why?
Naohisa Ogawa became hooked on the puzzle after seeing it presented on TV by Yoshinori Furukawa, an ice researcher at Hokkaido University. Now together they’ve worked out the explanation.
When ice crystals grow, heat escapes fastest from the tips of bumps on their surface, so water there freezes fastest too, accentuating the bumps. The closer the bumps are, the steeper the…
