Snowball fight: "Snow has all colors. He's not cold either, by the way."
Photo: Allen J. Schaben/Los Angeles Times/Getty Images
MIRROR: Mr. Schneebeli, it's snowing!
Schneebeli: Yes, here too!
MIRROR: Does that still fascinate you at all? You have been working as a snow researcher at the WSL Institute for Snow and Avalanche Research in Davos for more than 30 years. You have several expeditions to Antarctica and the Arctic behind you. What do you think if it snows normally outside the window now?
Schneebeli: That's still a miracle for me every time. No natural phenomenon changes the landscape as comprehensively as snowfall. I think of snow as a kind of short-lived rock, as sediment. As a researcher, I then see geological processes that normally take millions of years unfold before my eyes within a few minutes. Fascinating. And there are so many myths about snow, for example, that it is white.
MIRROR: Isn't he?
Schneebeli: No, it is transparent under the microscope. Glacial caves are blue-greenish, blood snow is reddish due to snow algae. Snow mixed with desert sand is orange. In the long-wave, thermal infrared range, on the other hand, snow does not appear white, but black, as it absorbs almost all radiation. So snow has all colors. By the way, it's not cold either.
MIRROR: But it seemed that way to me today.
Schneebeli: That's because you're a mammal with a core temperature of 37 degrees. From a physical point of view, on the other hand, snow is extremely hot. We call it a "high-temperature material". This means that the substance is usually very close to its melting temperature. That's what makes snow so dynamic, it's changing all the time, it's steaming, it's breathing, so to speak.
MIRROR: Do you have a favorite snowy place in the breathing snow?
Schneebeli: Of course, Antarctica is a paradise. There are firn quakes and diamond snow, which is formed under a bright blue sky, by the finest ice needles in the air, which slowly float to earth when there is no wind and are reminiscent of small stars due to the reflected sunlight. And there, on the edge of a large ice field, I saw huge ice crystals growing out of crevasses, centimeter-sized beaker crystals, giant snow, so to speak.
MIRROR: What is the best snow for a snowball?
Schneebeli: The ideal snow is fresh snow at about minus two degrees. Not wet yet, but already very hot. At these high temperatures, the crystal structures of snow weld together, the ball becomes malleable, but still solid. Wonderful.