It’s hard to preserve something as ephemeral as a snowflake, as seen in this microphotograph by Michael Robert Peres. Despite the old adage, it is possible to make identical snowflakes, but it requires mirroring the freezing conditions exactly, including both temperature and humidity. Here, the snowflake’s crystalline structure survives as a ghost in a melting droplet. (Image credit: M. Peres; via Ars Technica)
Tag: snowflakes
“Winter”
Little by little, snow and ice transform the landscape in Jamie Scott’s film “Winter.” From individual snowflakes to entire forest vistas, the timelapses showcase how winter remakes every surface in its image. The growing icicles show freezing in action, but I especially love seeing the “flow” brought about by progressively greater snowfall. Tree limbs bow, shrubs swell, and riverbanks contract as the snow gets thicker. And that final shot that pulls out from single snowflakes to the entire forest? Stunning! (Video and image credit: J. Scott et al.; via Colossal)
Snowflake Still-Life
To take these high-resolution images of individual snowflakes, Nathan Myhrvold and his collaborators built a special camera. Their apparatus keeps the snowflakes chilled despite the strong illumination cast on them. It uses a 500 microsecond shutter and focus-stacking to produce incredibly detailed portraits of these ephemeral subjects. Each snowflake’s shape is the result of the temperature and humidity that crystal experienced as it grew. Since these are natural snowflakes, no two are alike, but, with enough environmental control, it is possible to make twin snowflakes. (Image credit: N. Myhrvold; via Colossal)
Snowmelt
Much of the rain that falls on Earth began as snow high in the atmosphere. As it falls through warmer layers of air, the snowflakes melt and form water droplets. The details of this melting process have been difficult to capture experimentally, but a new computational model may provide insight. The basic process has a couple stages. As snow begins to melt, surface tension draws the water into concave areas nearby. When those regions fill up, the water flows out and merges with neighboring liquid, forming water droplets around a melting ice core.
Although this same sequence was observed for many types of snow, scientists also observed some important differences between rimed and unrimed snowflakes. Rime forms when supercooled water droplets freeze onto the surface of a snowflake. Lightly rimed snow still looks light and fluffy, like the animation above, but heavily rimed snow forms denser and more spherical chunks. Because there are lots of porous gaps in heavily rimed snow, water tends to gather there during initial melting. Rimed snow was also more likely to form one large water droplet rather than breaking into multiple droplets like snow with less rime. For more, check out NASA’s video and the Bad Astronomy write-up. (Image credit: NASA, source; research credit: J. Leinonen and A. von Lerber; via Bad Astronomy; submitted by Kam Yung-Soh)
