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We've all heard that each and every snowflake is unique. But in a lab in sunny southern California, a physicist has learned to control the way snowflakes grow. Can he really make twins? SUBSCRIBE to Deep Look! DEEP LOOK is a ultra-HD (4K) short video series created by KQED San Francisco and presented by PBS Digital Studios. See the unseen at the very edge of our visible world. Get a new perspective on our place in the universe. Explore big scientific mysteries by going incredibly small. * NEW VIDEOS EVERY OTHER TUESDAY! * California's historic drought is finally over thanks largely to a relentless parade of powerful storms that have brought the Sierra Nevada snowpack to the highest level in six years, and guaranteed skiing into June. All that snow spurs an age-old question -- is every snowflake really unique? “It’s one of these questions that’s been around forever,” said Ken Libbrecht, a professor of physics at the California Institute of Technology in Pasadena. “I think we all learn it in elementary school, the old saying that no two snowflakes are alike.” --- How do snowflakes form? Snow crystals form when humid air is cooled to the point that molecules of water vapor start sticking to each other. In the clouds, crystals usually start forming around a tiny microscopic dust particle, but if the water vapor gets cooled quickly enough the crystals can form spontaneously out of water molecules alone. Over time, more water molecules stick to the crystal until it gets heavy enough to fall. --- Why do snowflakes have six arms? Each water molecule is each made out of one oxygen atom and two hydrogen atoms. As vapor, the water molecules bounce around slamming into each other. As the vapor cools, the hydrogen atom of one molecule forms a bond with the oxygen of another water molecule. This is called a hydrogen bond. These bonds make the water molecules stick together in the shape of a hexagonal ring. As the crystal grows, more molecules join fitting within that same repeating pattern called a crystal array. The crystal keeps the hexagonal symmetry as it grows. --- Is every snowflake unique? Snowflakes develop into different shapes depending on the humidity and temperature conditions they experience at different times during their growth. In nature, snowflakes don’t travel together. Instead, each takes it’s own path through the clouds experiencing different conditions at different times. Since each crystal takes a different path, they each turn out slightly differently. Growing snow crystals in laboratory is a whole other story. --- Read the entire article on KQED Science: --- For more information: Ken Libbrecht’s online guide to snowflakes, snow crystals and other ice phenomena. --- More Great Deep Look episodes: Can A Thousand Tiny Swarming Robots Outsmart Nature? | Deep Look What Gives the Morpho Butterfly Its Magnificent Blue? | Deep Look The Amazing Life of Sand | Deep Look The Hidden Perils of Permafrost | Deep Look --- See some great videos and documentaries from the PBS Digital Studios! The Science of Snowflakes | It’s OK to be Smart An Infinite Number of Words for Snow | PBS Idea Channel Is an Ice Age Coming? | Space Time | PBS Digital Studios --- Follow KQED Science: KQED Science: Tumblr: Twitter: --- About KQED KQED, an NPR and PBS affiliate in San Francisco, CA, serves Northern California and beyond with a public-supported alternative to commercial TV, Radio and web media. Funding for Deep Look is provided in part by PBS Digital Studios and the John S. and James L. Knight Foundation. Deep Look is a project of KQED Science, which is also supported by HopeLab, the S. D. Bechtel, Jr. Foundation, the Dirk and Charlene Kabcenell Foundation, the Vadasz Family Foundation, the Gordon and Betty Moore Foundation, the Smart Family Foundation and the members of KQED. #deeplook
