Who'd ever guess that skating on thin ice could be so ... (dangerously) fun?
Hear how skating on black ice - a precariously thin layer of ice that forms on a recently frozen lake - can produce otherworldly, laser-like sounds in this fascinating video clip by Nat Geo.
Swedish photograher and filmmaker Henrik Trygg and mathematician Mårten Ajne, both ice skating enthusiasts, explain how black ice makes those weird sounds:
Why is black ice so good at producing those amazing, laser-like sounds?
In the video, the sounds are created by me skating on it. There is a distinctive sonorous tone and the noise from cracks striking.
Black ice doesn’t expand and contract because it’s kept warm by the underlying water, even when it’s cold out. Isothermal would be the technical word for it—in a narrow temperature range.
The sonorous tone is the song of black ice, best heard (and recorded) from a short distance. The layman explanation would be that the tone is inversely related to the thickness of the ice. The thinner the ice, the higher the tone. Intriguingly, the ice is about to collapse at high C, the supposedly highest note of a soprano opera singer, for example in Puccini’s Turandot.