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24 April 2014 11:45 am ,
Vol. 344 ,
Major climate data sets have underestimated the rate of global warming in the last 15 years owing largely to poor data...
The tsetse fly is best known as the vector for the trypanosome parasites that cause sleeping sickness and a disease in...
The National Institutes of Health is revising its "two strikes" rule, which allowed researchers only one chance to...
By stabilizing the components of retromers, molecular complexes that act like recycling bins in cells, a recently...
Fossil fuels power modern society by generating heat, but much of that heat is wasted. Semiconductor devices called...
Researchers are gaining insights into what made Supertyphoon Haiyan so powerful and devastating through post-storm...
Millions around the world got a first-hand look at what it was like to be in Tacloban while it was pummeled by...
- 24 April 2014 11:45 am , Vol. 344 , #6182
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ScienceShot: The Sharp Shape of Frozen Water
12 October 2012 3:04 pm
Frozen water droplets take on a whole new shape when they freeze: Instead of staying round, they form a pointy tip, and eventually sprout a tiny forest of ice crystals on their surface. In order to observe these effects, researchers dripped tiny beads of water on a plate kept at a chilly -20°C. In the 18 seconds that it took the 4-millimeter-diameter droplets (top row) to solidify, researchers snapped photos of the water freezing from the bottom up. During the final stage of freezing, the ice drops developed a pointy tip (middle row), which continued to grow and eventually formed delicate ice crystals on the surface, the team reported last month in Physics of Fluids. Researchers believe the unusual pointy tip is caused by the vertical expansion of the ice combined with the surface tension on remaining liquid. Once frozen, the sharp tip of the drop attracts water vapor from the air, and produces treelike ice crystals (bottom row).
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