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The Amazing Water-Repelling Chemistry Behind Superhydrophobic Materials

To understand how phone cases, windshields, and raincoats are all able to repel liquid, a good place to start is by examining nature—specifically, leafhoppers.

Chemistry Champion winner Mallory Hinks explains that superhydrophobic (roughly translated as "a whole lot of water-hating") coating imitates the ways of this fascinating bug. Like leafhoppers, when water droplets come in contact with it, the liquid forms a ball and sits on top until eventually rolling off.

This phenomenon can be explained by "contact angles": Water droplets have a contact angle with a leafhopper's wing of about 170 degrees—whereas most objects fall somewhere between zero and 120, resulting in the formation of a puddle. At 180 degrees, the droplet would form a perfect sphere.

To learn more about surface chemistry—and how it is possible to pour an entire bottle of red wine on your white shirt without leaving a stain—you can watch the full video from Reactions below:

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History
The Queen of Code: Remembering Grace Hopper
By Lynn Gilbert, CC BY-SA 4.0, Wikimedia Commons

Grace Hopper was a computing pioneer. She coined the term "computer bug" after finding a moth stuck inside Harvard's Mark II computer in 1947 (which in turn led to the term "debug," meaning solving problems in computer code). She did the foundational work that led to the COBOL programming language, used in mission-critical computing systems for decades (including today). She worked in World War II using very early computers to help end the war. When she retired from the U.S. Navy at age 79, she was the oldest active-duty commissioned officer in the service. Hopper, who was born on this day in 1906, is a hero of computing and a brilliant role model, but not many people know her story.

In this short documentary from FiveThirtyEight, directed by Gillian Jacobs, we learned about Grace Hopper from several biographers, archival photographs, and footage of her speaking in her later years. If you've never heard of Grace Hopper, or you're even vaguely interested in the history of computing or women in computing, this is a must-watch:

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science
Why Are Glaciers Blue?
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The bright azure blue sported by many glaciers is one of nature's most stunning hues. But how does it happen, when the snow we see is usually white? As Joe Hanson of It's Okay to Be Smart explains in the video below, the snow and ice we see mostly looks white, cloudy, or clear because all of the visible light striking its surface is reflected back to us. But glaciers have a totally different structure—their many layers of tightly compressed snow means light has to travel much further, and is scattered many times throughout the depths. As the light bounces around, the light at the red and yellow end of the spectrum gets absorbed thanks to the vibrations of the water molecules inside the ice, leaving only blue and green light behind. For the details of exactly why that happens, check out Hanson's trip to Alaska's beautiful (and endangered) Mendenhall Glacier below.

[h/t The Kid Should See This]

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