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Your Afternoon Catharsis: Liquid Droplets Coalescing in Slow Motion

You've probably seen two beads of liquid coalesce hundreds of times in your life. Maybe thousands. But we're willing to bet you've never seen them do it in slow motion.

This high-speed video, which was filmed at 16,000 frames per second and is played back here at 20, shows two beads of silicone oil becoming one. As FYFD's Nicole Sharpe puts it, the video highlights the "intricate interplay between surface tension, viscosity, and inertia" in this otherwise mundane process:

At the very instant the drops meet, an infinitesimally small neck is formed between the droplets. Mathematically speaking, the pressure and curvature of the droplets diverge as a result of this tiny contact area. This is an example of a singularity. Surface tension rapidly expands the neck, sending capillary waves rippling along the drops as they become one.


Like most high-speed videos of water, the process is positively mesmerizing to behold. Not to mention ridiculously satisfying.

More catharsis and visceral satisfaction here, here and here.

[S. Nagel et al. and J. Paulsen via FYFD]

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Oo, it's always exciting to see FYFD make it onto io9. And thank you for even mentioning me by name! I'm Sharp with no e, though, like the pointy end.