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What the hell is going on with these balls?

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Two glass spheres are dropped into a pool of resting water. The sphere on the left causes almost no splash at all, while the one on the right looks like it's doing an impression of your cousin Joey pulling a cannonball at the community pool. The balls are the same size, shape and material. What gives?

Photo credit: L. Bocquet et al.

Here it is again in a looping animation:


Give up? FYFD explains:

It all comes down to the surface treatments. The glass sphere on the left is hydrophilic, but the right one has been treated to be hydrophobic. As a result, the water-fearing molecules of that sphere push the water away, allowing air to be entrained below the water’s surface instead. This creates a big splash that’s absent when the water moves smoothly around the hydrophilic sphere.


The hydrophobic treatment in question was designed by physicist Lydéric Bocquet and his team at France's Université Lyon. You can read more about it in this back issue of Nature Physics, or over at New Scientist.